D.4.0 REMEDIATION RISK
This section presents the results of the assessment for radiological and toxicological risk during remediation to remediation workers, noninvolved workers, and the general public for each of the TWRS alternatives. The risk presented in this section was evaluated using the methodology described in Section D.2.0. Using this methodology, remediation risk to the MEIs are expressed as the probability that the individual would contract a fatal cancer as a result of exposure to a radioactive substance and/or carcinogenic chemicals during the duration of the proposed project. In the case of an exposed population, remediation risk represents the expected increase in LCFs in the population at risk of potential exposure. The toxic effects resulting from chemical exposure also are analyzed.
D.4.1 NO ACTION ALTERNATIVE (TANK WASTE)
This section presents the anticipated remediation risk associated with the No Action alternative for tank waste, as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative were based on the air emissions and direct exposure from continued operations (including tank farm and evaporator operations). There would be no construction, retrieval, pretreatment, treatment, storage, disposal, or waste transportation activities associated with this alternative; therefore, there would be no risk from these components.
D.4.1.1 Radiological Risk
The LCF risk to the worker, noninvolved worker, and general public receptors could result from atmospheric emissions from the evaporator and tank farms. The risk was determined by analyzing the radiological source term, transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.1.1.1 Source Term
Operating air emissions shown in Table D.4.1.1 are the evaporator and tank farm source term for the noninvolved workers and the general public (WHC 1995g and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure to radiation fields associated with the evaporator and tank farm operations.
Table D.4.1.1 Atmospheric Radiological Emissions for the No Action Alternative (Tank Waste)
D.4.1.1.2 Transport
The atmospheric transport parameters for the No Action alternative are presented in Table D.4.1.2. The tank farm atmospheric radiological operating emissions were modeled as a ground release and the evaporator was modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data presented in Table D.2.2.1 and Figure D.2.2.1.
Table D.4.1.2 Atmospheric Transport Parameters for the No Action Alternative (Tank Waste)
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.00E-04 sec/m3 for the noninvolved worker MEI and 6.60E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.90E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for 10 years of evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.00E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.60E-03 sec/m3.
D.4.1.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.1.3. The table shows the exposure each receptor would receive from every component. The sum of the components is shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995g and Jacobs 1996). The calculations for the worker exposures from continued operations are as follows:
| Tank farms = (5.00E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 7.00E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 8.28E+02 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved worker and general public receptor exposures to the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q from Table D.4.1.2. The dose for each receptor from tank farm and evaporator operations is presented in Table D.4.1.3.
D.4.1.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from the evaporator and tank farms, shown in the combined dose column in Table D.4.1.4, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk. The LCF risk for each receptor is presented in Table D.4.1.4.
Table D.4.1.4 Summary of Anticipated Risk for the No Action Alternative (Tank Waste)
D.4.1.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm and the evaporator for the worker, noninvolved worker, and general public. Potential carcinogenic risks and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.1.2.1 Source Term
Operating air emissions from the tank farm area and the evaporator are presented in Table D.4.1.5 (WHC 1995g and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area and the evaporator. The worker would be exposed only to emissions (ground-level release) from the tank farm area because emissions from the evaporator occur through a stack-release and would not impact the onsite worker.
Table D.4.1.5 Chemical Emissions for the No Action Alternative (Tank Waste)
D.4.1.2.2 Transport
The tank farm chemical operating emissions were modeled as a ground release. Chemical operating emissions from the evaporator would occur from the evaporator stack and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and MEI general public are identical to the radiological parameters presented in Table D.4.1.2.
The MEI worker was evaluated using a "box" model presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.1.2.3 Exposure
Worker
As discussed previously in Section D.2.2.3, the MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions from the tank farm area (mg/m3) were estimated by multiplying the cumulative tank farm emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3). Exposure point concentrations for each volatile chemical emitted from the tank farm area are summarized in Table D.4.1.6.
Table D.4.1.6 No Action Alternative Tank Farm Emissions
Estimated operating chemical emission intakes for the MEI worker were calculated according to the equation presented in Section D.2.2.3 and are presented in Table D.4.1.6.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area and the evaporator were estimated by multiplying the cumulative tank farm and evaporator emission rates (mg/sec) by the MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm and 2.50E-06 sec/m3 for the evaporator, respectively). Exposure point concentrations for each volatile chemical emitted from the tank farm area and evaporator are summarized in Table D.4.1.7 and D.4.1.8, respectively.
Table D.4.1.7 No Action Alternative Tank Farm Emissions
Table D.4.1.8 No Action Alternative (Tank Waste) Evaporator Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.1.7 and D.4.1.8 for the tank farm area and evaporator emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area and the evaporator were estimated by multiplying the cumulative tank farm and evaporator emission rates (mg/sec) by the MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm and 3.90E-08 sec/m3 for the evaporator), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and evaporator are summarized in Table D.4.1.9 and D.4.1.10, respectively.
Table D.4.1.9 No Action Alternative Tank Farm Emissions
Table D.4.1.10 No Action Alternative (Tank Waste) Evaporator Emissions
D.4.1.2.4 Toxicity Assessment
Toxicity assessment characterizes the relationship between the exposure to a chemical and the incidence of adverse health effects in exposed populations. In a quantitative carcinogenic risk assessment, the dose-response relationship of a carcinogen is expressed in terms of a slope factor (oral) or unit risk (inhalation), which are used to estimate the probability of risk of cancer associated with a given exposure pathway. Cancer slope factors and URFs as published by EPA (IRIS and HEAST) were used in this operating chemical emission evaluation.
For noncarcinogenic effects, toxicity data developed from animal or human studies typically are used to develop noncancer acceptable levels, or RfDs. A chronic RfD is defined as an estimate of a daily exposure for the human population, including sensitive subpopulations, that is likely to be without appreciable risk of deleterious effects. Chronic RfDs, as published in IRIS or HEAST, were used in this chemical evaluation. Table D.4.1.11 summarizes the cancer slope factors, RfDs, and data sources for each volatile operating chemical emission.
Table D.4.1.11 Toxicity Criteria for Operations Chemical Emissions
D.4.1.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm are summarized in Table D.4.1.6. The total HI and cancer risk from routine tank farm emissions are 7.70E-02 and 7.05E-07, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risks for chemical emissions from the tank farm and evaporator are summarized in Tables D.4.1.7 and D.4.1.8, respectively. The total HI and cancer risk from combined tank farm and evaporator emissions are 3.33E-02 and 3.05E-07, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risks for chemical emissions from the tank farm and evaporator are summarized in Tables D.4.1.9 and D.4.1.10, respectively. The total HI and cancer risk from combined tank farm and evaporator emissions is 1.82E-05 and 9.08E-11, respectively.
D.4.2 LONG-TERM MANAGEMENT ALTERNATIVE
This section presents the anticipated remediation risk associated with the Long-Term Management alternative for tank waste, as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative were based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), and retrieval operations. There would be no pretreatment, treatment, storage, disposal, or waste transportation activities associated with this alternative; therefore, there would be no risk from these components.
D.4.2.1 Radiological Risk
The LCF risk to the worker, noninvolved worker, and the general public could result from direct exposure and atmospheric emissions from the evaporators and tank farms. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.2.1.1 Source Term
Operating air emissions shown in Table D.4.2.1 are the evaporator and tank farm source terms for the noninvolved workers and the general public (WHC 1995g and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure to radiation fields associated with the evaporator and tank farm operations.
Table D.4.2.1 Atmospheric Radiological Emissions for the Long-Term Management Alternative
D.4.2.1.2 Transport
The atmospheric transport parameters of the Long-Term Management alternative are presented in Table D.4.2.2. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release and the evaporator emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.2.2 Atmospheric Transport Parameters for the Long-Term Management Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.0E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary from the 200 East Area in an east-southeast direction).
The calculated Chi/Q values for 20 years of evaporator operations were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.6E-03 sec/m3.
D.4.2.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.2.3. The table shows the exposure each receptor would receive from every component. The sum of the components is shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
Table D.4.2.3 Summary of Anticipated Radiological Exposure for the Long-Term Management Alternative
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995g and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, and retrieval are as follows:
- Construction = (7.17E+02 person-yr) (1.4E-02 rem/person-yr) = 1.0E+01 person-rem
- Continued Operations -
Tank farms = (5.00E+04 person-yr) (1.40E-02 rem/person-yr) = 7.0E+02 person-rem
Evaporator = (7.86E+02 person-yr) (2.00E-01 rem/person-yr) = 1.6E+02 person-rem
Total = 8.6E+02 person-rem - Retrieval = (1.82E+03 person-yr) (2.00E-01 rem/person-yr) = 3.6E+02 rem
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved worker and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.2.1.4 Risk
The LCFs are calculated as the product of the estimated dose multiplied by the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, and retrieval, for each receptor shown in the combined dose column in Table D.4.2.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.2.4 Summary of Anticipated Risk for the Long-Term Management Alternative
D.4.2.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, and evaporators for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.2.2.1 Source Term
Operating air emissions from the tank farm area, tank waste retrieval, and the evaporators are presented in Table D.4.2.5 (WHC 1995g and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, and the evaporators. The worker would be exposed only to emissions (ground-level release) from the tank farm area and retrieval operations because emissions from the evaporators occur through a stack-release and would not impact the onsite worker.
Table D.4.2.5 Chemical Emissions for the Long-Term Management Alternative
D.4.2.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporators would occur from the evaporator stacks and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and MEI general public are identical to the radiological parameters presented in Table D.4.2.2.
The MEI worker was evaluated using a "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.2.2.3 Exposure
Worker
As discussed previously in Section D.4.1.2.2, the MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.2.6 and D.4.2.7, respectively.
Table D.4.2.6 Long-Term Management Tank Farm Emissions
Table D.4.2.7 Long-Term Management Retrieval Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4.2.6 and D.4.2.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, and the evaporators were estimated by multiplying the cumulative tank farm, retrieval, and evaporator emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm, 4.0E-04 sec/m3 for retrieval, 2.5E-06 sec/m3 for the two evaporators). Exposure point concentrations for each volatile chemical emitted from the tank farm area, retrieval operations, and the evaporators are summarized in Tables D.4.2.8, and D.4.2.9, D.4.2.10, and D.4.2.11, respectively.
Table D.4.2.8 Long-Term Management Tank Farm Emissions
Table D.4.2.9 Long-Term Management Retrieval Emissions
Table D.4.2.10 Long-Term Management Evaporator-1 Emissions
Table D.4.2.11 Long-Term Management Evaporator-2 Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.2.8, D.4.2.9, D.4.2.10, and D.4.2.11 for the tank farm area, retrieval, evaporator-1 , and evaporator-2 emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, retrieval operations, evaporator-1 , and evaporator-2 were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for retrieval operations, 6.00E-08 sec/m3 for evaporator-1 , and 3.90E-08 sec/m3 for evaporator-2 ). Exposure point concentrations for each volatile chemical emitted from the tank farm area, retrieval operations, evaporator-1 , and evaporator-2 are summarized in Tables D.4.2.12, D.4.2.13, D.4.2.14, and D.4.2.15, respectively.
Table D.4.2.12 Long-Term Management Tank Farm Emissions
Table D.4.2.13 Long-Term Management Retrieval Emissions
Table D.4.2.14 Long-Term Management Evaporator-1 Emissions
Table D.4.2.15 Long-Term Management Evaporator-2 Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.2.12, D.4.2.13, D.4.2.14, and D.4.2.15 for the tank farm area, retrieval, evaporator-1 , and evaporator-2 , respectively.
D.4.2.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.2.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4.2.6 and D.4.2.7, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions are 1.12E-01 and 9.84E-07, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risks for chemical emissions from the tank farm, retrieval operations, evaporator-1 , and evaporator-2 are summarized in Tables D.4.2.8, D.4.2.9, D.4.2.10, and D.4.2.11, respectively. The total HI and cancer risk from combined tank farm, retrieval, and evaporator emissions are 4.85E-02 and 4.26E-07, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, retrieval operations, evaporator-1 , and evaporator-2 are summarized in Tables D.4.2.12, D.4.2.13, D.4.2.14, and D.4.2.15, respectively. The total HI and cancer risk from combined tank farm, retrieval, and evaporator emissions are 3.51E-05 and 1.27E-10, respectively.
D.4.3 IN SITU FILL AND CAP ALTERNATIVE
This section presents the anticipated remediation risk associated with the In Situ Fill and Cap alternative for tank waste, as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative were based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), treatment (including evaporator and gravel fill operations), and closure and monitoring. There would be no retrieval, pretreatment, storage, or waste transportation activities associated with this alternative; therefore, there would be no risk from these components.
D.4.3.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, transport mechanism, exposure, and risk associated with the exposure as discussed in the following subsections.
D.4.3.1.1 Source Term
Source terms used for the noninvolved worker and general public are the atmospheric radiological emissions presented in Table D.4.3.1 (WHC 1995f and Jacobs 1996). The worker would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.3.1 Atmospheric Radiological Emissions for the In Situ Fill and Cap Alternative
D.4.3.1.2 Transport
The atmospheric transport parameters of the In Situ Fill and Cap alternative are presented in Table D.4.3.2. The tank farm and gravel fill atmospheric radiological operating emissions were modeled as a ground release, and the evaporators were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.3.2 Atmospheric Transport Parameters for the In Situ Fill and Cap Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.6E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.6E-03 sec/m3.
D.4.3.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.3.3. The table shows the exposure each receptor would receive from every component. The sum of the components is shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed, but is represented by the component with the highest MEI dose.
Table D.4.3.3 Summary of Anticipated Radiological Exposure for the In Situ Fill and Cap Alternative
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995f and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, treatment, and closure are as follows:
| Construction = (1.37E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 1.9E+00 person-rem |
| Continued Operations - | ||
| Tank farms = (1.21E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 1.7E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.3E+02 person-rem |
| Total | = | 3.0E+02 person-rem |
| Treatment Operations - | ||
| Evaporator = (7.30E+01 person-yr) · (2.00E-01 rem/person-yr) | = | 1.5E+01 person-rem |
| Gravel fill = (1.04E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 2.1E+02 person-rem |
| Total | = | 2.3E+02 person-rem |
| Closure - | ||
| Closure = (1.83E+02 person-yr) · (1.4E-02E-01 rem/person-yr) | = | 2.56E+00 person-rem |
| Monitoring = (6.25E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 8.75E+00 person-rem |
| Total | = | 1.13E+01 person- rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.3.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4.3.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.3.4 Summary of Anticipated Risk for the In Situ Fill and Cap Alternative
D.4.3.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, the evaporators, and tank filling (gravel filling) operations for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.3.2.1 Source Term
Operating air emissions from the tank farm area and the evaporators and filling the tanks with gravel are presented in Table D.4.3.5 (WHC 1995f and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, the evaporators, and filling the tanks with gravel. The worker would be exposed only to emissions (ground-level release) from the tank farm area and filling the tanks with gravel because emissions from the evaporators occur through a stack-release and would not impact the onsite worker.
Table D.4.3.5 Chemical Emissions for the In Situ Fill and Cap Alternative
D.4.3.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during filling the tanks with gravel) were modeled as a ground release. Chemical operating emissions from the evaporators would occur from the evaporator stacks and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.3.2.
The MEI worker was evaluated using a "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.3.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and filling the tanks with gravel were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and tank-filling emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.3.6 and D.4.3.7, respectively.
Table D.4.3.6 In Situ Fill and Cap Tank Farm Emissions
Table D.4.3.7 In Situ Fill and Cap Gravel Fill Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and tank filling operations for the MEI worker are presented in Tables D.4.3.6 and D.4.3.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, filling the tanks with gravel, and the evaporators were estimated by multiplying the cumulative tank farm, tank-filling, and evaporator emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm, 4.0E-04 sec/m3 for tank-filling, 2.50E-06 sec/m3 for the evaporators).
Exposure point concentrations for each volatile chemical emitted from the tank farm area, tank-filling operations, and the evaporators are summarized in Tables D.4.3.8 and D.4.3.9, D.4.3.10, and D.4.3.11, respectively.
Table D.4.3.8 In Situ Fill and Cap Tank Farm Emissions
Table D.4.3.9 In Situ Fill and Cap Gravel Fill Emissions
Table D.4.3.10 In Situ Fill and Cap Evaporator-1 Emissions
Table D.4.3.11 In Situ Fill and Cap Evaporator-2 Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.3.8, D.4.3.9, D.4.3.10, and D.4.3.11 for the tank farm area, tank-filling, evaporator-1 , and evaporator-2 emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, tank-filling operations, the evaporator, and the DST evaporator were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for tank-filling operations, and 3.90E-08 sec/m3 for the evaporators). Exposure point concentrations for each volatile chemical emitted from the tank farm area, tank-filling operations, evaporator-1 , and evaporator-2 are summarized in Tables D.4.3.12, D.4.3.13, D.4.3.14, and D.4.3.15, respectively.
Table D.4.3.12 In Situ Fill and Cap Tank Farm Emissions
Table D.4.3.13 In Situ Fill and Cap Gravel Fill Emissions
Table D.4.3.14 In Situ Fill and Cap Evaporator-1 Emissions
Table D.4.3.15 In Situ Fill and Cap Evaporator-2 Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.3.12, D.4.3.13, D.4.3.14, and D.4.3.15 for the tank farm area, tank-filling operations, evaporator-1 , and evaporator-2 , respectively.
D.4.3.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.3.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and tank filling operations are summarized in Tables D.4.3.6 and D.4.3.7, respectively. The total HI and cancer risk from routine tank farm emissions and tank filing emissions are 7.89E-02 and 4.50E-07, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, tank filling operations, evaporator-1 , and evaporator-2 are summarized in Tables D.4.3.8, D.4.3.9, D.4.3.10, and D.4.3.11, respectively. The total HI and cancer risk from combined tank farm, tank filling, and evaporator emissions are 3.42E-02 and 1.95E-07, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, tank filling operations, the evaporator, and the DST evaporator are summarized in Tables D.4.3.12, D.4.3.13, D.4.3.14, and D.4.3.15, respectively. The total HI and cancer risk from combined tank farm, tank filling, and evaporator emissions are 2.75E-05 and 5.80E-11, respectively.
D.4.4 IN SITU VITRIFICATION ALTERNATIVE
This section presents the anticipated remediation risk associated with the In Situ Vitrification alternative for tank waste as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), treatment (including evaporator and in situ vitrification operations), and closure and monitoring. There would be no retrieval, pretreatment, storage, or waste transportation activities associated with this alternative; therefore, there would be no risk from these components.
D.4.4.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.4.1.1 Source Term
Source terms used for the noninvolved worker and general public are the atmospheric radiological emissions presented in Table D.4.4.1 (WHC 1995f and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.4.1 Atmospheric Radiological Emissions for the In Situ Vitrification Alternative
D.4.4.1.2 Transport
The atmospheric transport parameters of the In Situ Vitrification alternative are presented in Table D.4.4.2. The tank farm atmospheric radiological operating emissions were modeled as a ground release, and the evaporators and in situ vitrification were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Figure D.2.2.1 and Table D.2.2.1.
Table D.4.4.2 Atmospheric Transport Parameters for the In Situ Vitrification Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.6E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporators and 300 m (980 ft) for vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the vitrification operation, the Chi/Q values were 2.30E-07 sec/m3 for the noninvolved worker MEI, 2.4E-08 sec/m3 for the general public MEI, 2.00E-04 sec/m3 for the noninvolved worker population, and 1.10E-03 sec/m3 for the general public population.
D.4.4.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.4.3. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed, but is represented by the component with the highest MEI dose.
Table D.4.4.3 Summary of Anticipated Radiological Exposure for the In Situ Vitrification Alternative
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995f and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, treatment, and closure are as follows:
| Construction = (5.73E+03 person-yr) · (1.4E-02 rem/person-yr) | = | 8.02E+01 person-rem |
| Continued Operations - | ||
| Tank farms = (1.06E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 1.48E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 2.76E+02 person-rem |
| Treatment Operations - | ||
| Evaporator = (7.30E+01 person-yr) · (2.00E-01 rem/person-yr) | = | 1.46E+01 person-rem |
| Vitrification = (5.89E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 1.18E+03 person-rem |
| Total | = | 1.19E+03 person-rem |
| Closure - | ||
| Closure = (1.82E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 2.55E+00 person-rem |
| Monitoring = (5.00E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 7.00E+00 person-rem |
| Total | = | 9.55E+00 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved worker and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.4.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure for each receptor shown in the combined dose column in Table D.4.4.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.4.4 Summary of Anticipated Risk for the In Situ Vitrification Alternative
D.4.4.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, the evaporators, tank filling (sand filling) operations, and vitrification of the tank contents for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.4.2.1 Source Term
Operating air emissions from the tank farm area, filling the tanks with sand, the evaporators, and vitrification of the tank contents are presented in Table D.4.4.5 (WHC 1995f and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, the evaporators, filling the tanks with sand, and vitrification. The worker would be exposed only to emissions (ground-level release) from the tank farm area filling the tanks with sand because emissions from the evaporators and vitrification occur through a stack-release and would not impact the onsite worker.
Table D.4.4.5 In Situ Vitrification Source Emissions
D.4.4.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during filling the tanks with gravel) were modeled as a ground release. Chemical operating emissions from the evaporators and vitrification operations would occur from stacks and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.4.2.
The MEI worker was evaluated using a "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.4.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and filling the tanks with sand were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and tank-filling emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.4.6 and D.4.4.7, respectively.
Table D.4.4.6 In Situ Vitrification Tank Farm Emissions
Table D.4.4.7 In Situ Vitrification Sand Fill Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and tank filling operations for the MEI worker are presented in Tables D.4.4.6 and D.4.4.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, filling the tanks with sand, the evaporators, and vitrification operations were estimated by multiplying the cumulative tank farm, tank-filling, evaporator, and vitrification emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm, 4.0E-04 sec/m3 for tank-filling, 2.5E-06 sec/m3 for the evaporators, and 2.30E-07 sec/m3 for vitrification). Exposure point concentrations for each volatile chemical emitted from the tank farm area, tank-filling operations, evaporators, and vitrification are summarized in Tables D.4.4.8 and D.4.4.9, D.4.4.10, D.4.4.11, and D.4.4.12, respectively.
Table D.4.4.8 In Situ Vitrification Tank Farm Emissions
Table D.4.4.9 In Situ Vitrification Sand Fill Emissions
Table D.4.4.10 In Situ Vitrification Evaporator -1 Emissions
Table D.4.4.11 In Situ Vitrification Evaporator -2 Emissions
Table D.4.4.12 In Situ Vitrification Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.4.8, D.4.4.9, D.4.4.10, D.4.4.11, and D.4.4.12 for the tank farm area, tank-filling, evaporator-1 , evaporator-2 , and vitrification emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, tank-filling operations, evaporator-1 , evaporator-2 , and vitrification were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for tank-filling operations, 3.90E-08 sec/m3 for the evaporators, and 2.40E-08 sec/m3 for vitrification). Exposure point concentrations for each volatile chemical emitted from the tank farm area, tank-filling operations, evaporator-1 , evaporator-2 , and vitrification are summarized in Tables D.4.4.13, D.4.4.14, D.4.4.15, D.4.4.16, and D.4.4.17, respectively.
Table D.4.4.13 In Situ Vitrification Tank Farm Emissions
Table D.4.4.14 In Situ Vitrification Sand Fill Emissions
Table D.4.4.15 In Situ Vitrification Evaporator-1 Emissions
Table D.4.4.16 In Situ Vitrification Evaporator-2 Emissions
Table D.4.4.17 In Situ Vitrification Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.4.13, D.4.4.14, D.4.4.15, D.4.4.16, and D.4.4.17 for the tank farm area, tank-filling operations, evaporator-1 , evaporator-2 , and vitrification, respectively.
D.4.4.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.4.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and tank filling operations are summarized in Tables D.4.4.6 and D.4.4.7, respectively. The total HI and cancer risk from routine tank farm emissions and tank filling emissions are 7.89E-02 and 4.51E-07, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, tank filling operations, evaporator-1 , evaporator-2 , and vitrification are summarized in Tables D.4.4.8, D.4.4.9, D.4.4.10, D.4.4.11, and D.4.4.12, respectively. The total HI and cancer risk from combined tank farm, tank filling, evaporator, and vitrification emissions are 3.48E-02 and 1.95E-07, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, tank filling operations, evaporator-1 , evaporator-2 , and vitrification are summarized in Tables D.4.4.13, D.4.4.14, D.4.4.15, D.4.4.16, and D.4.4.17, respectively. The total HI and cancer risk from combined tank farm, tank filling, evaporator, and vitrification emissions are 2.04E-04 and 5.81E-11, respectively.
D.4.5 EX SITU INTERMEDIATE SEPARATIONS ALTERNATIVE
This section presents the anticipated remediation risk associated with the Ex Situ Intermediate Separations alternative for tank waste, as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, separations and treatment, storage and disposal, onsite transportation of waste, monitoring and maintenance, and closure and monitoring.
D.4.5.1 Radiological Risk
The LCF risk to the worker, noninvolved worker, and the general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.5.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.5.1 (WHC 1995j and Jacobs 1996). They also would receive a direct exposure dose from the vitrified HLW as it is being transported onsite . The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
D.4.5.1.2 Transport
The atmospheric transport parameters of the Ex Situ Intermediate Separations alternative are presented in Table D.4.5.2. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release, and the evaporator and the separations and vitrification were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.5.2 Atmospheric Transport Parameters for the Ex Situ Intermediate Separations Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.6E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 800 m (2,600 ft) for separations and vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.6E-03 sec/m3. For the separations and vitrification operation, the Chi/Q values were 2.9E-08 sec/m3 for the noninvolved worker MEI, 7.70E-09 sec/m3 for the general public MEI, 5.00E-05 sec/m3 for the noninvolved worker population, and 5.00E-04 sec/m3 for the general public population.
D.4.5.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.5.3. The table shows the exposure each receptor would receive from every component. The sum of the components is shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995j and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (8.02E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 1.12E+01 person-rem |
| Continued Operations - | ||
| Tank farms = (1.90E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 2.66E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 3.94E+02 person-rem |
| Retrieval = (2.21E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 4.42E+03 person-rem |
| Separation/Treatment = (1.49E+04 person-yr) · (2.0E-01 rem/person-yr) | = | 2.98E+03 person-rem |
| Monitoring/Maintenance = (6.00E+01 person-yr) · (1.4E-02 rem/person-yr) | = | 8.40E-01 person-rem |
| Closure - | ||
| Closure = (2.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.88E+00 person-rem |
| Monitoring = (6.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 9.48E+00 person-rem |
| Total | = | 1.34E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.5.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, retrieval, treatment, storage and disposal, monitoring and maintenance, and closure for each receptor shown in the combined dose column in Table D.4.5.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.5.4 Summary of Anticipated Risk for the Ex Situ Intermediate Separations Alternative
D.4.5.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, the evaporator, and exposure to particulate emissions from the separation and vitrification of HLW and low-activity waste (LAW) for the worker, noninvolved worker, and the general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.5.2.1 Source Term
Operating air emissions from the tank farm area, tank waste retrieval, the evaporator, and vitrification facilities are presented in Table D.4.5.5 (WHC 1995j and Jacobs 1996). The emission rates from the HLW and LAW vitrification facilities were combined and treated as a single-source emission. The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, evaporator, and vitrification facilities. The worker would be exposed only to emissions (ground-level release) from the tank farm area and retrieval operations because emissions from the evaporator and vitrification facilities occur through a stack-release and would not impact the onsite worker.
Table D.4.5.5 Chemical Emissions for the Ex Situ Intermediate Separations
D.4.5.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporator and vitrification facilities would occur from stack releases and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.5.2.
The MEI worker (onsite worker) was evaluated using a simplified "box" model, as presented in detail in Section D.4.1.2.2. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.5.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively.
Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.5.6 and D.4.5.7, respectively.
Table D.4.5.6 Ex Situ Intermediate Separations Tank Farm Emissions
Table D.4.5.7 Ex Situ Intermediate Separations Retrieval Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4.5.6 and D.4.5.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, evaporator, and vitrification facilities were estimated by multiplying the cumulative tank farm, retrieval, evaporator, and plant emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm, 2.50E-06 sec/m3 for the evaporator, 4.0E-04 sec/m3 for retrieval, and 2.90E-08 sec/m3 for the vitrification plant). Exposure point concentrations for each volatile chemical emitted from the tank farm area, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.5.8, D.4.5.9, D.4.5.10, and D.4.5.11, respectively.
Table D.4.5.8 Ex Situ Intermediate Separations Tank Farm Emissions
Table D.4.5.9 Ex Situ Intermediate Separations Evaporator Emissions
Table D.4.5.10 Ex Situ Intermediate Separations Retrieval Emissions
Table D.4.5.11 Ex Situ Intermediate Separations Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.5.8, D.4.5.9, D.4.5.10, and D.4.5.11 for the tank farm area, the evaporator, retrieval operations, and the vitrification facility emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, the evaporator, retrieval operations, and the vitrification facility were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for the evaporator, 6.60E-08 sec/m3 for retrieval operations, and 7.70E-09 sec/m3 for the vitrification facility). Exposure point concentrations for each volatile chemical emitted from the tank farm area, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.5.12, D.4.5.13, D.4.5.14, and D.4.5.15, respectively.
Table D.4.5.12 Ex Situ Intermediate Separations Tank Farm Emissions
Table D.4.5.13 Ex Situ Intermediate Separations Evaporator Emissions
Table D.4.5.14 Ex Situ Intermediate Separations Retrieval Emissions
Table D.4.5.15 Ex Situ Intermediate Separations Plant Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.5.12, D.4.5.13, D.4.5.14, and D.4.5.15 for the tank farm area, the evaporator, retrieval operations, and the vitrification plant, respectively.
D.4.5.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.5.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4.5.6 and D.4.5.7, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions are 3.08E-01 and 2.51E-06, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.5.8, D.4.5.9, D.4.5.10, and D.4.5.11, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and plant emissions are 1.33E-01 and 1.09E-06, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.5.12, D.4.5.13, D.4.5.14, and D.4.5.15, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and plant emissions are 7.29E-05 and 5.43E-10, respectively.
D.4.6 EX SITU NO SEPARATIONS ALTERNATIVE
This section presents the anticipated remediation risk associated with the Ex Situ No Separations alternative for tank waste, as outlined in Volume Two, Appendix B.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, treatment (vitrification or calcination), storage and disposal, onsite transportation of waste, monitoring and maintenance, and closure and monitoring. There would be no pretreatment and therefore, no associated risk.
D.4.6.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.6.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.6.1 (WHC 1995c and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.6.1 Atmospheric Radiological Emissions for the Ex Situ No Separations Alternative
D.4.6.1.2 Transport
The atmospheric transport parameters of the Ex Situ No Separations alternative are presented in Table D.4.6.2. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release, and the evaporator and vitrification or calcination emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Tables D.2.2.1 and D.2.2.2 and Figures D.2.2.1 and D.2.2.2.
Table D.4.6.2 Atmospheric Transport Parameters for the Ex Situ No Separations Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.6E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q was 1.6E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 800 m (2,625 ft) for treatment (vitrification or calcination). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the treatment (vitrification or calcination) operation, the Chi/Q values were 2.90E-08 sec/m3 for the noninvolved worker MEI, 7.70E-09 sec/m3 for the general public MEI, 5.00E-05 sec/m3 for the noninvolved worker population, and 5.00E-04 sec/m3 for the general public population.
D.4.6.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.6.3. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated individual dose. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995c and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (8.02E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 1.12E+01 person-rem |
| Continued Operations - | ||
| Tank farms = (1.09E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 1.53E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 2.81E+02 person-rem |
| Retrieval = (2.10E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 4.20E+03 person-rem |
| Treatment = (1.89E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 3.78E+02 person-rem |
| Monitoring/Maintenance = (5.40E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 7.56E+00 person-rem |
| Closure - | ||
| Closure = (2.15E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.01E+00 person-rem |
| Monitoring = (5.93E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 8.30E+00 person-rem |
| Total | = | 1.13E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.6.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4.6.4, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.6.4 Summary of Anticipated Risk for the Ex Situ No Separations (Vitrification) Alternative
D.4.6.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, and the evaporator, and exposure to particulate emissions from the separation and vitrification of HLW and LAW for the worker, noninvolved worker, and the general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.6.2.1 Source Term
Operating air emissions from the tank farm area, tank waste retrieval, evaporator, and vitrification facility are presented in Table D.4.6.5. The emission rates from the HLW and LAW vitrification facilities were combined and treated as a single-source emission. The noninvolved worker and the general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, evaporator, and vitrification facilities. The worker would only be exposed to emissions (ground-level release) from the tank farm area and retrieval operations because emissions from the evaporator and vitrification facilities occur through a stack-release and would not impact the onsite worker.
Table D.4.6.5 Chemical Emissions for the Ex Situ No Separation
D.4.6.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporator and vitrification facilities would occur from stack releases and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.6.2.
The MEI worker was evaluated using a simplified "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.6.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.6.6 and D.4.6.7, respectively.
Table D.4.6.6 Ex Situ No Separations Tank Farm Emissions
Table D.4.6.7 Ex Situ No Separations Retrieval Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4.6.6 and D.4.6.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, evaporator, and vitrification facilities were estimated by multiplying the cumulative tank farm, retrieval, evaporator, and plant emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.00E-04 sec/m3 for the tank farm, 2.50E-06 sec/m3 for the evaporator, 4.00E-04 sec/m3 for retrieval, and 2.90E-08 sec/m3 for the vitrification facility). Exposure point concentrations for each volatile chemical emitted from the tank farm area, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.6.8, D.4.6.9, D.4.6.10, and D.4.6.11, respectively.
Table D.4.6.8 Ex Situ No Separations Tank Farm Emissions
Table D.4.6.9 Ex Situ No Separations Evaporator Emissions
Table D.4.6.10 Ex Situ No Separations Retrieval Emissions
Table D.4.6.11 Ex Situ No Separations Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.6.8, D.4.6.9, D.4.6.10 and D.4.6.11 for the tank farm area, the evaporator, retrieval operations and the vitrification facility emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, the evaporator, retrieval operations, and the vitrification facility were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 3.90E-08 sec/m3 for the evaporator, 6.60E-08 sec/m3 for retrieval operations, and 7.70E-09 sec/m3 for the vitrification facility). Exposure point concentrations for each volatile chemical emitted from the tank farm area, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.6.12, D.4.6.13, D.4.6.14 and D.4.6.15, respectively.
Table D.4.6.12 Ex Situ No Separations Tank Farm Emissions
Table D.4.6.13 Ex Situ No Separations Evaporator Emissions
Table D.4.6.14 Ex Situ No Separations Retrieval Emissions
Table D.4.6.15 Ex Situ No Separations Plant Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.6.12, D.4.6.13, D.4.6.14, and D.4.6.15 for the tank farm area, the evaporator, retrieval operations and the vitrification facility, respectively.
D.4.6.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.6.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4.6.6 and D.4.5.7, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions are 3.08E-01 and 1.90E-06, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, the evaporator, retrieval operation, and the vitrification facility are summarized in Tables D.4.6.8, D.4.6.9, D.4.6.10 and D.4.6.11, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and plant emissions are 1.33E-01 and 8.22E-07, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.6.12, D.4.6.13, D.4.6.14 and D.4.6.15, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and plant emissions are 7.34E-05 and 4.29E-10, respectively.
D.4.6.3 Calcination Subalternative
Calcining the tank waste rather than vitrifying it is a subalternative to the Ex Situ No Separations alternative as out lined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this subalternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, treatment (vitrification or calcination), storage and disposal, onsite transportation of waste, monitoring and maintenance, and closure and monitoring. There would be no pretreatment (separations) ; therefore, there would be no risk from pretreatment.
D.4.6.3.1 Radiological Risk
The LCF risk to workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.6.1 (WHC 1995c and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Transport
The atmospheric transport parameters are presented in Table D.4.6.2.
Exposure
The radiological exposure for the Ex Situ No Separations (Calcination) alternative is presented in Table D.4.6.16. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed, but is represented by the component with the highest MEI dose.
Exposure to the worker population and MEI worker was previously calculated in Section D.4.6.1.3. The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4.6.17, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.6.17 Summary of Anticipated Risk for the Ex Situ No Separations Alternative (Calcination)
D.4.7 EX SITU EXTENSIVE SEPARATIONS ALTERNATIVE
This section presents the anticipated remediation risk associated with the Ex Situ Extensive Separations alternative for tank waste, as outlined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, separations and treatment, onsite transportation of waste, monitoring and maintenance, and closure and monitoring.
D.4.7.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.7.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.7.1 (WHC 1995e and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.7.1 Atmospheric Radiological Emissions for the Ex Situ Extensive Separations Alternative
D.4.7.1.2 Transport
The atmospheric transport parameters of the Ex Situ Extensive Separations alternative are presented in Table D.4.7.2. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release and the evaporator and the separations and vitrification were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.7.2 Atmospheric Transport Parameters for the Ex Situ Extensive Separations Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.0E-04 sec/m3 for the noninvolved worker MEI and 6.60E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.90E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 800 m (2,600 ft) for separations and vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the separations and vitrification operation, the Chi/Q values were 2.90E-08 sec/m3 for the noninvolved worker MEI, 7.70E-09 sec/m3 for the general public MEI, 5.00E-05 sec/m3 for the noninvolved worker population, and 5.00E-04 sec/m3 for the general public population.
D.4.7.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.7.3. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. These data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995e and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (8.02E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 1.12E+01 person-rem |
| Continued Operations - | ||
| Tank farms = (1.24E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 1.74E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 3.02E+02 person-rem |
| Retrieval = (2.21E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 4.42E+03 person-rem |
| Separation/Treatment = (1.63E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 3.26E+03 person-rem |
| Monitoring/Maintenance = (6.00E+01 person-yr) · (1.40E-02 rem/person-yr) | = | 8.40E-01 person-rem |
| Closure - | ||
| Closure = (2.81E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.93E+00 person-rem |
| Monitoring = (8.20E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 1.15E+01 person-rem |
| Total | = | 1.54E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.7.1.4 Risk
Latent cancer fatalities are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4.7.4, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.7.4 Summary of Anticipated Risk for the Ex Situ Extensive Separations Alternative
D.4.7.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, and the evaporator, and exposure to particulate emissions from the separation and vitrification of HLW and LAW for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.7.2.1 Source Term
Operating air emissions from the tank farm area, tank waste retrieval, the evaporator and vitrification facilities are presented in Table D.4.7.5 (WHC 1995e and Jacobs 1996). The emission rates from the HLW and LAW vitrification facilities were combined and treated as a single-source emission. The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, evaporator, and vitrification facilities. The worker would only be exposed to emissions (ground-level release) from the tank farm area and retrieval Operations because emissions from the evaporator and vitrification facilities occur through a stack-release and would not impact the onsite worker.
Table D.4.7.5 Chemical Emissions for the Ex Situ Extensive Separations Alternative
D.4.7.2.2 Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporator and vitrification facilities would occur from stack releases and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.7.2.
The MEI worker was evaluated using a simplified "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.7.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.7.6 and D.4.7.7, respectively.
Table D.4.7.6 Ex Situ Extensive Separations Tank Farm Emissions
Table D.4.7.7 Ex Situ Extensive Separations Retrieval Emissions
Chemical intake (dose) was estimated for the MEI Worker using the same equation and exposure parameters defined in Section D.2.2.3.1. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4.7.6 and D.4.7.7, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, evaporator, and vitrification facilities were estimated by multiplying the cumulative tank farm, retrieval, evaporator and plant emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.0E-04 sec/m3 for the tank farm, 2.50E-06 sec/m3 for the evaporator, 4.0E-04 sec/m3 for retrieval, and 2.90E-08 sec/m3 for the vitrification facility). Exposure point concentrations for each chemical emitted from the tank farm area, the evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.7.8, D.4.7.9, D.4.7.10 and D.4.7.11, respectively.
Table D.4.7.8 Ex Situ Extensive Separations Tank Farm Emissions
Table D.4.7.9 Ex Situ Extensive Separations Evaporator Emissions
Table D.4.7.10 Ex Situ Extensive Separations Retrieval Emissions
Table D.4.7.11 Ex Situ Extensive Separations Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.7.8, D.4.7.9, D.4.7.10 and D.4.7.11 for the tank farm area, the evaporator, retrieval operations, and the vitrification facility emissions, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, evaporator, retrieval operations, and the vitrification facility were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 3.90E-08 sec/m3 for evaporator, 6.60E-08 sec/m3 for retrieval operations, and 7.70E-09 sec/m3 for the vitrification facility). Exposure point concentrations for each chemical emitted from the tank farm area, the evaporator, retrieval operations and the vitrification facility are summarized in Tables D.4.7.12, D.4.7.13, D.4.7.14 and D.4.7.15, respectively.
Table D.4.7.12 Ex Situ Extensive Separations Tank Farm Emissions
Table D.4.7.13 Ex Situ Extensive Separations Evaporator Emissions
Table D.4.7.14 Ex Situ Extensive Separations Retrieval Emissions
Table D.4.7.15 Ex Situ Extensive Separations Plant Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.7.12, D.4.7.13, D.4.7.14, and D.4.7.15 for the tank farm area, the evaporator, retrieval operations and the vitrification facility, respectively.
D.4.7.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.7.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4.7.6 and D.4.7.7, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions are 3.08E-01 and 2.33E-06, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.7.8, D.4.7.9, D.4.7.10 and D.4.7.11, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and plant emissions are 1.33E-01 and 1.01E-06, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4.7.12, D.4.7.13, D.4.7.14 and D.4.7.15, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval and plant emissions are 7.28E-05 and 4.92E-10, respectively.
D.4.8 EX SITU/IN SITU COMBINATION 1 ALTERNATIVE
This section presents the anticipated remediation risk associated with the Ex Situ/In Situ Combination 1 alternative for tank waste, as outlined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, separations and treatment (including vitrification, evaporator, and gravel fill operations), onsite transportation of waste , storage and disposal, monitoring and maintenance, and closure and monitoring.
D.4.8.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.8.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.8.1 (WHC 1995f, 1995j, and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.8.1 Atmospheric Radiological Emissions for the Ex Situ/In Situ Combination 1 Alternative
D.4.8.1.2 Transport
The atmospheric transport parameters of the Ex Situ/In Situ Combination 1 alternative are presented in Table D.4.8.2. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release; the evaporator and the separations and vitrification were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.8.2 Atmospheric Transport Parameters for Ex Situ/In Situ Combination 1 Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.00E-04 sec/m3 for the noninvolved worker MEI and 6.60E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.90E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 800 m (2,600 ft) for separations and vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.0E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the separations and vitrification operation, the Chi/Q value was 2.90E-08 sec/m3 for the noninvolved worker MEI, 7.70E-09 sec/m3 for the general public MEI, 5.00E-05 sec/m3 for the noninvolved worker population, and 5.00E-04 sec/m3 for the general public population.
D.4.8.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.8.3. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed, but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated individual dose. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995f, j and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (5.36E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 7.50E+00 person-rem |
| Continued Operations - | ||
| Tank farms = (1.90E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 2.66E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 3.94E+02 person-rem |
| Retrieval = (1.32E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 2. 64 E+03 person-rem |
| Separation/Treatment = (9.98E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 2.00E+03 person-rem |
| Monitoring/Maintenance = (6.00E+01 person-yr) · (1.40E-02 rem/person-yr) | = | 8.40E-01 person rem |
| Closure - | ||
| Closure = (2.44E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.41E+00 person-rem |
| Monitoring = (6.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 9.48E+00 person-rem |
| Total | = | 1.29E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.8.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4.8.4, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.8.4 Summary of Anticipated Risk for the Ex Situ/In Situ Combination 1 Alternative
D.4.8.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, the evaporators, tank filling (sand filling) operations, retrieval operations, and particulate emissions from vitrification of tank waste for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.8.2.1 Source Term
Operating air emissions from the tank farm area, the evaporators, filling the tanks with sand, retrieval of the tank waste, and vitrification of tank waste are presented in Table D.4.8.5 (WHC 1995f, j and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, the evaporators, filling the tanks with sand, retrieval operations and vitrification, while the worker would only be exposed to emissions (ground-level release) from the tank farm area, filling the tanks with sand and retrieval, because emissions from the evaporators and vitrification facility occur through a stack-release and would not impact the onsite worker.
Table D.4.8.5 Chemical Emissions for the Ex Situ/In Situ Combination 1 Alternative
D.4.8.2.2 Transport
Chemical operating emissions from the tank farm, filling of the tanks and retrieval of tank waste were modeled as a ground release. Chemical operating emissions from the evaporators and vitrification facility would occur from the evaporator stacks and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4.8.2.
The MEI worker was evaluated using a simplified "box" model, as presented in detail in Section D.4.1.2.2. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.8.2.3 Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area, filling the tanks with sand and retrieval of tank waste were estimated by multiplying each cumulative source emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3). Exposure point concentrations for each volatile chemical emitted from the tank farm area, retrieval operations, and filling of the tanks are summarized in Tables D.4.8.6, D.4.8.7 and D.4.8.8, respectively.
Table D.4.8.6 Ex Situ/In Situ Combination 1 Tank Farm Emissions
Table D.4.8.7 Ex Situ/In Situ Combination 1 Retrieval Emissions
Table D.4.8.8 Ex Situ/In Situ Combination 1 Gravel Fill Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm, retrieval operations and tank filling operations for the MEI worker are presented in Tables D.4.8.6, D.4.8.7, and D.4.8.8, respectively.
Noninvolved Worker
The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, evaporators, retrieval operations, tank-filling, and vitrification were estimated by multiplying each cumulative source emission rate (mg/sec) by its respective MEI noninvolved worker Chi/Q value (4.00E-04 sec/m3 for the tank farm, 4.00E-04 sec/m3 for tank-filling, 2.50E-06 sec/m3 for the evaporator, 4.00E-04 sec/m3 for retrieval, and 2.90E-08 sec/m3 for vitrification). Exposure point concentrations for each volatile chemical emitted from the tank farm area, evaporators, retrieval, tank-filling and vitrification are summarized in Tables D.4.8.9, D.4.8.10, D.4.8.11, D.4.8.12, D.4.8.13 and D.4.8.14, respectively.
Table D.4.8.9 Ex Situ/In Situ Combination 1 Tank Farm Emissions
Table D.4.8.10 Ex Situ/In Situ Combination 1 Evaporator-1 Emissions
Table D.4.8.11 Ex Situ/In Situ Combination 1 Evaporator-2 Emissions
Table D.4.8.12 Ex Situ/In Situ Combination 1 Retrieval Emissions
Table D.4.8.13 Ex Situ/In Situ Combination 1 Gravel Emissions
Table D.4.8.14 Ex Situ/In Situ Combination 1 Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4.8.9, D.4.8.10, D.4.8.11, D.4.8.12, D.4.8.13 and D.4.8.14 for the tank farm area, evaporator-1, evaporator-2 , retrieval operations, tank-filling, and vitrification, respectively.
General Public
The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from each source were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for tank-filling operations, 3.90E-08 sec/m3 for the evaporators, 6.60E-08 sec/m3 for retrieval, and 7.70E-09 sec/m3 for vitrification). Exposure point concentrations for each chemical emitted from the tank farm area, evaporator-1, evaporator-2 , retrieval, tank-filling, and vitrification are summarized in Tables D.4.8.15, D.4.8.16, D.4.8.17, D.4.8.18, D.4.8.19 and D.4.8.20, respectively. The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4.8.15, D.4.8.16, D.4.8.17, D.4.8.18, D.4.8.19, and D.4.8.20 for the tank farm area, evaporator-1, evaporator-2 , retrieval, tank-filling, and vitrification, respectively.
Table D.4.8.15 Ex Situ/In Situ Combination 1 Tank Farm Emissions
Table D.4.8.16 Ex Situ/In Situ Combination 1 Evaporator-1 Emissions
Table D.4.8.17 Ex Situ/In Situ Combination 1 Evaporator-2 Emissions
Table D.4.8.18 Ex Situ/In Situ Combination 1 Retrieval Emissions
Table D.4.8.19 Ex Situ/In Situ Combination 1 Gravel Fill Emissions
Table D.4.8.20 Ex Situ/In Situ Combination 1 Plant Emissions
D.4.8.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.8.2.5 Risk Characterization
MEI Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, retrieval and tank filling operations are summarized in Tables D.4.8.6, D.4.8.7 and D.4.8.8, respectively. The total HI and cancer risk are 3.10E-01 and 2.52E-06, respectively.
MEI Noninvolved Worker
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator-1, evaporator-2 , retrieval, tank-filling, and vitrification are summarized in Tables D.4.8.9, D.4.8.10, D.4.8.11, D.4.8.12, D.4.8.13 and D.4.8.14, respectively. The total HI and cancer risk are 1.34E-01 and 1.09E-06, respectively.
MEI General Public
The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator-1, evaporator-2 , retrieval, tank-filling, and vitrification are summarized in Tables D.4.8.15, D.4.8.16, D.4.8.17, D.4.8.18, D.4.8.19 and D.4.8.20, respectively. The total HI and cancer risk are and 5.44E-10, respectively.
D.4.9 EX SITU/IN SITU COMBINATION 2 ALTERNATIVE
This section presents the anticipated remediation risk associated with the Ex Situ/In Situ Combination 2 alternative for tank waste, as outlined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this alternative was based on the same factors discussed for the Ex Situ/In Situ Combination 1 alternative (Section D.4.8).
D.4.9.1 Radiological Risk
Latent cancer fatality risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.9.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4.9.1 (WHC 1995f,1995j and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.9.1 Atmospheric Radiological Emissions for the Ex Situ/In Situ Combination 2 Alternative
D.4.9.1.2 Transport
The atmospheric transport parameters of the Ex Situ/In Situ Combination 2 alternative are identical to those presented in Table D.4.8.2 for the Ex Situ/In Situ Combination 1 alternative. The modeling assumptions and calculated Chi/Q values for the Ex Situ/In Situ Combination 2 alternative are also identical to those discussed in Section D.4.8.1.2 for the Ex Situ/In Situ Combination 1 alternative.
D.4.9.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.9.2. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed, but is represented by the component with the highest MEI dose.
The worker population dose is dependent on the number of people in the population and the anticipated individual dose. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995f, j and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (5.36E+02 person-yr) · (1.4E-02 rem/person-yr) | = | 7.50E+00 person-rem |
| Continued Operations - | ||
| Tank farms = (1.90E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 2.66E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 3.94E+02 person-rem |
| Retrieval = (1.32E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 2.64E+03 person-rem |
| Separation/Treatment = (9.98E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 2.00E+03 person-rem |
| Monitoring/Maintenance = (6.00E+01 person-yr) · (1.40E-02 rem/person-yr) | = | 8.40E-01 person rem |
| Closure - | ||
| Closure = (2.44E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.41E+00 person-rem |
| Monitoring = (6.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 9.48E+00 person-rem |
| Total | = | 1.29E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.9.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure for each receptor shown in the combined dose column in Table D.4.9.3 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.9.3 Summary of Anticipated Risk for the Ex Situ/In Situ Combination 2 Alternative
D.4.9.2 Chemical Exposure
The potential carcinogenic risk and noncarcinogenic health hazards resulting from implementing the Ex Situ/In Situ Combination 2 may result from exposure to volatile emissions from the tank farm, the evaporators, tank filling (sand filling) operations, retrieval operations, and particulate emissions from vitrification of tank waste for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
D.4.9.2.1 Source Term
The source emissions for the Ex Situ/In Situ Combination 2 alternative are approximately the same as those of the Ex Situ/In Situ Combination 1 alternative. This is a conservative assumption based on reviewing and comparing the waste types, volumes, and activities that would take place during the operating period of the Ex Situ/In Situ Combination 2 alternative. The chemical concentration of many contaminants would be higher for the waste retrieved for the Ex Situ/In Situ Combination 2 compared to Ex Situ/In Situ Combination 1 alternative. However, the volume of waste that would be retrieved for the Ex Situ/In Situ Combination 2 alternative would be approximately 30 percent of the Ex Situ/In Situ Combination 1 alternative. The volume of vitrified waste produced would be approximately 60 percent of the Ex Situ/In Situ Combination 1 alternative. Volatile emissions from the waste treatment facilities stacks would be lower for the Ex Situ/In Situ Combination 2 alternative based on smaller treatment facilities and smaller contaminant inventories. Chemical emissions from the waste treatment facilities would be the largest component of the operating emissions. Volatile emissions from the fill and cap portion of the Ex Situ/In Situ Combination 2 alternative would be higher than those from the Ex Situ/In Situ Combination 1 alternative because more tanks would be treated in situ. The combination of these factors resulted in assessing the chemical risk using the same emissions rates for both combination alternatives.
Therefore, operating air emissions from the tank farm area, the evaporators, filling the tanks with sand, retrieval of the tank waste, and vitrification of tank waste are presented in Table D.4.8.5 (WHC 1995f, j and Jacobs 1996). The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, the evaporators, filling the tanks with sand, retrieval operations and vitrification, while the worker would only be exposed to emissions (ground-level release) from the tank farm area, filling the tanks with sand and retrieval, because emissions from the evaporators and vitrification facility occur through a stack-release and would not impact the onsite worker.
D.4.9.2.2 Transport
Chemical transport modeling assumptions and parameters for the Ex Situ/In Situ Combination 2 alternative are identical to those presented in Table D.4.8.2 for the Ex Situ/In Situ Combination 1 alternative. The MEI worker was evaluated using a simplified "box" model, as presented in detail in Section D.4.1.2.2. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
D.4.9.2.3 Exposure
The chemical exposure to each MEI receptor (i.e., worker, noninvolved worker, and general public) from volatile chemicals emitted as a result of implementing the Ex Situ/In Situ Combination 2 alternative is approximately equal to that of Ex Situ/In Situ Combination 1 alternative.
Therefore, chemical intake (dose) for each MEI receptor are presented in Section D.4.8.2.3.
D.4.9.2.4 Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
D.4.9.2.5 Risk Characterization
The noncarcinogenic hazard, and carcinogenic risk to each MEI receptor (i.e., worker, noninvolved worker, and general public) resulting from implementing the Ex Situ/In Situ Combination 2 alternative are approximately equal to that of the Ex Situ/In Situ Combination 1 alternative.
The total HI and cancer risk to each MEI receptor for each scenario is presented in Section D.4.8.2.5.
D.4. 10 PHASED IMPLEMENTATION ALTERNATIVE
The Phased Implementation alternative includes remediating the tank waste in a two-phase process. The first phase would be a commercial demonstration of the separations and immobilization processes for selected tank waste. The second step would involve scaling-up the demonstration processes to treat the remaining tank waste and construction of larger treatment facilities.
D.4.10.1 Phase 1
This section presents the anticipated remediation risk associated with Phase 1, as outlined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction (including construction, decontamination and decommissioning), continued operations (including tank farm and evaporator operations), retrieval, separations and treatment (including the LAW vitrification facility and the LAW/HLW vitrification facility), storage and disposal, and monitoring and maintenance.
D.4.10.1.1 Radiological Risk
Th LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 10 .1. The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the workplace.
Table D.4.10 .1 Atmospheric Radiological Emissions for Phase 1
Transport
The atmospheric transport parameters for Phase 1 are presented in Table D.4.10 .2. The tank farm atmospheric radiological operating emissions were modeled as a ground release and the evaporator and the separations and vitrification were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.10 .2 Atmospheric Transport Parameters for Phase 1
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.00E-04 sec/m3 for the noninvolved worker MEI and 6.60E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.9E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 400 m (1,300 ft) for separations and vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 4.00E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q values were 1.60E-03 sec/m3. For the separations and vitrification operation, the Chi/Q values were 9.40E-08 sec/m3 for the noninvolved worker MEI, 1.50E-08 sec/m3 for the general public MEI, 1.20E-04 sec/m3 for the noninvolved worker population, and 8.00E-04 sec/m3 for the general public population.
Exposure
The radiological exposure for the alternative is presented in Table D.4.10 .3. The table shows the exposure each receptor would receive from every component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
Table D.4.10 .3 Summary of Anticipated Radiological Exposure for Phase 1
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995a and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction = (5.00E-01 person-yr) (1.40E-02 rem/person-yr) | = | 7.00E-03 person-rem |
| Continued Operations - | ||
| Tank farms = (5.00E+03 person-yr) · (1.40E-02 rem/person-yr) | = | 7.00E+01 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 1.98E+02 person-rem |
| Retrieval = (1.00E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 2.00E+01 person-rem |
| Separation/Treatment = (3.36E+03 person-yr) · (2.00E-01 rem/person-yr) | = | 6.72E+02 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, treatment, and closure, for each receptor shown in the combined dose column in Table D.4. 10 .4, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.10 .4 Summary of Anticipated Risk for Phase 1
D.4.10.1.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, and the evaporator, and exposure to particulate emissions from the separation and vitrification of HLW and LAW for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
Source Term
Operating air emissions from the tank farm area, tank waste retrieval, evaporator and vitrification facilities are presented in Table D.4.10 .5 (Jacobs 1996). The emission rates from the full-scale HLW and LAW vitrification facilities were combined and treated as a single-source emission, as discussed in Section D.4.5.2.1 for the Ex Situ Intermediate Separations alternative. This assumption is conservative and health protective as the pilot separation/vitrification facilities are scaled-down versions and would emit a fraction of the particulates emitted in this scenario. The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, evaporator, and vitrification facilities. The worker would only be exposed to emissions (ground-level release) from the tank farm area and retrieval operations because emissions from the evaporator and vitrification facilities occur through a stack-release and would not impact the onsite worker.
Table D.4.10 .5 Chemical Emissions for Phase 1
Transport
The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporator and vitrification facilities would occur from stack releases and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public, are identical to the radiological parameters presented in Table D.4. 10 .2.
The MEI worker was evaluated using a simplified "box" model, as presented in detail in Section D.2.2.3. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
Exposure
Worker
The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4.10 .6 and D.4. 10 .7, respectively.
Table D.4.10 .6 Phase 1 Tank Farm Emissions
Table D.4.10 .7 Phase 1 Retrieval Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4. 10 .6 and D.4.10 .7, respectively.
Noninvolved Worker - The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm, and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, evaporator, and vitrification facilities were estimated by multiplying the cumulative tank farm, retrieval, evaporator, and plant emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.00E-04 sec/m3 for the tank farm, 2.50E-06 sec/m3 for the evaporator, 4.00E-04 sec/m3 for retrieval, and 2.90E-08 sec/m3 for the vitrification facility). Exposure point concentrations for each chemical emitted from the tank farm area, the evaporator, retrieval operations and the vitrification facility are summarized in Tables D.4.10 .8, D.4. 10 .9, D.4.10 .10 and D.4. 10 .11, respectively.
Table D.4.10 .8 Phase 1 Tank Farm Emissions
Table D.4.10 .9 Phase 1 Evaporator Emissions
Table D.4.10 .10 Phase 1 Retrieval Emissions
Table D.4.10 .11 Phase 1 Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4. 10 .8, D.4.10 .9, D.4. 10 .10, and D.4.10 .11 for the tank farm area, the evaporator, retrieval operations, and the vitrification facility emissions, respectively.
General Public - The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, the evaporator, retrieval operations, and the vitrification facility were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 3.90E-08 sec/m3 for evaporator, 6.60E-08 sec/m3 for retrieval operations, and 7.70E-09 sec/m3 for the vitrification facility). Exposure point concentrations for each volatile chemical emitted from the tank farm area, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4. 10 .12, D.4. 10 .13, D.4. 10 .14 and D.4. 10 .15, respectively.
Table D.4.10 .12 Phase 1 Tank Farm Emissions
Table D.4.10 .13 Phase 1 Evaporator Emissions
Table D.4.10 .14 Phase 1 Retrieval Emissions
Table D.4.10 .15 Phase 1 Plant Emissions Phase 1 Plant Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4. 10 .12, D.4. 10 .13, D.4. 1 .14, and D.4. 10 .15 for the tank farm area, the evaporator, retrieval operations and the vitrification facility, respectively.
Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
Risk Characterization
MEI Worker - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4. 10 .6 and D.4.10 .7, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions are 1.12E-01 and 5.14E-07, respectively.
MEI Noninvolved Worker - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4. 10 .8, D.4. 10 .9, D.4. 10 .10 and D.4. 10 .11, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval and plant emissions are 4.84E-02 and 2.23E-07, respectively.
MEI General Public - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the vitrification facility are summarized in Tables D.4. 10 .12, D.4. 10 .13, D.4. 10 .14 and D.4. 10 .15, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval and plant emissions are 2.82E-05 and 1.58E-10, respectively.
D.4.10.2 Total Alternative
This section presents the anticipated remediation risk associated with the Total alternative for tank waste, as outlined in Volume Two, Appendix B of the EIS.
The radiological and toxicological risk for this alternative was based on the air emissions and direct exposure from construction, continued operations (including tank farm and evaporator operations), retrieval, separations and treatment (including Phase 1 and Phase 2), storage and disposal, onsite transportation of waste, monitoring and maintenance, and closure and monitoring.
D.4.10.2.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
Source Term - The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 10 .16 (WHC 1995j and Jacobs 1996). They would also receive a direct exposure dose from the vitrified HLW as it is being transported to a national HLW repository. The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.10 .16 Atmospheric Radiological Emissions for the Total Alternative
Transport - The atmospheric transport parameters of the Total alternative are presented in Table D.4. 10 .17. The tank farm and retrieval atmospheric radiological operating emissions were modeled as a ground release, and the evaporator and the separations and vitrification were modeled as elevated releases. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.10 .17 Atmospheric Transport Parameters for the Total Alternative
For ground releases, dispersion in the atmosphere would cause contaminant air concentrations and exposures to decrease with increasing distance from the source. Maximum individual exposures therefore would occur at the inner boundaries (i.e., closest distance to the source) of the defined receptor occupancy zones. For the noninvolved worker, the maximum exposure would occur 100 m (330 ft) from the source (in an east-southeast direction). For the general public, the maximum exposure would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the center of the 200 East Area).
The calculated Chi/Q values for ground releases from the tank farms were calculated by the GENII computer code to be 4.00E-04 sec/m3 for the noninvolved worker MEI and 6.60E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 1.60E-03 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 2.90E-03 sec/m3.
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction) for the evaporator and 800 m (2,600 ft) for separations and vitrification. The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values for the evaporator operation were 2.50E-06 sec/m3 for the noninvolved worker MEI and 3.90E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q values were 4.00E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q values were 1.60E-03 sec/m3. For Phase 1 separations and vitrification operation, the Chi/Q values were 9.40E-08 sec/m3 for the noninvolved worker MEI, 1.50E-08 sec/m3 for the general public MEI, 1.20E-04 sec/m3 for the noninvolved worker population, and 8.00E-04 sec/m3 for the general public population. For Phase 2 separations and vitrification operation, the Chi/Q values were 2.90E-08 sec/m3 for the noninvolved worker MEI, 7.70E-09 sec/m3 for the general public MEI, 5.00E-05 sec/m3 for the noninvolved worker population, and 5.00E-04 sec/m3 for the general public population.
Exposure - The radiological exposure for the alternative is presented in Table D.4. 10 .18. The table shows the exposure each receptor would receive from each component. The sum of the components are shown in the last column for each population and MEI receptor except for the MEI worker. The MEI worker is not summed but is represented by the component with the highest MEI dose.
Table D.4.10 .18 Summary of Anticipated Radiological Exposure for the Total Alternative
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995j and Jacobs 1996). The calculations for the worker exposures from construction, continued operations, retrieval, separations and treatment, monitoring and maintenance, and closure are as follows:
| Construction | ||
| Phase 1 = (5.00E-01 person-yr) · (1.40E-02 rem/person-yr) | = | 7.00E-03 person-rem |
| Phase 2 = (5.36E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 7.50E+00 person-rem |
| Total | = | 7.51E+00 person-rem |
| Continued Operations - Phase 1 and Phase 2 | ||
| Tank farms = (1.90E+04 person-yr) · (1.40E-02 rem/person-yr) | = | 2.66E+02 person-rem |
| Evaporator = (6.40E+02 person-yr) · (2.00E-01 rem/person-yr) | = | 1.28E+02 person-rem |
| Total | = | 3.94E+02 person-rem |
| Retrieval | ||
| Phase 1 and 2 = (2.21E+04 person-yr) · (2.00E-01 rem/person-yr) | = | 4.42E+03 person-rem |
| Separation/Treatment | ||
| Phase 1= (6.72E+03 person-yr) · (2.0E-01 rem/person-yr) | = | 1.34E+03 person-rem |
| Phase 2= (9.98E+03 person-yr) · (2.0E-01 rem/person-yr) | = | 2.00E+03 person-rem |
| Total | = | 3.34E+03 person-rem |
| Monitoring and Maintenance. | ||
| Phase 1 and 2 = (6.00E+01 person-yr) · (1.40E-02 rem/person-yr) | = | 8.40E-01 person-rem |
| Closure - Phase 1 and Phase 2 | ||
| Closure = (2.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 3.88E+00 person-rem |
| Monitoring = (6.77E+02 person-yr) · (1.40E-02 rem/person-yr) | = | 9.48E+00 person-rem |
| Total | = | 1.34E+01 person-rem |
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a maximum of 30 years.
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q value.
Risk - The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The sum of the radiological dose from construction, continued operations, retrieval, treatment, storage and disposal, monitoring and maintenance, and closure for each receptor shown in the combined dose column in Table D.4.10 .19, was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.10 .19 Summary of Anticipated Risk for the Total Alternative
D.4.10.2.2 Chemical Exposure
Potential carcinogenic risk and noncarcinogenic health hazards may result from exposure to volatile emissions from the tank farm, tank waste retrieval, the evaporator, and exposure to particulate emissions from the separation and vitrification of HLW and LAW for the worker, noninvolved worker, and general public. Potential carcinogenic risk and noncarcinogenic health hazards were estimated using the chemical source term, transport mechanism, exposure, and toxicological criteria as discussed in the following subsections.
Source Term - Operating air emissions from the tank farm area, tank waste retrieval, evaporator, and vitrification facilities are presented in Table D.4. 10 .20 (WHC 1995j and Jacobs 1996). The emission rates from the HLW and LAW vitrification facilities were combined and treated as a single-source emission for both Phase 1 and Phase 2. The noninvolved worker and general public would be exposed to combined emissions from the tank farm area, tank waste retrieval operations, evaporator, and Phase 1 and Phase 2 vitrification facilities. The worker only would be exposed to emissions (ground-level release) from the tank farm area and retrieval operations because emissions from the evaporator and vitrification facilities occur through a stack-release and would not impact the onsite worker.
Table D.4.10 .20 Chemical Emissions for the Total Alternative
Transport - The tank farm chemical operating emissions (routine emissions from the tank farm and emissions during retrieval) were modeled as a ground release. Chemical operating emissions from the evaporator and vitrification facilities would occur from stack releases and were modeled as elevated releases. Transport parameters, location of the MEI noninvolved worker and MEI general public, and Chi/Q values for the MEI noninvolved worker and general public are identical to the radiological parameters presented in Table D.4. 10 .17.
The MEI worker (onsite worker) was evaluated using a simplified box model, as presented in detail in Section D.4.1.2.2. The estimated Chi/Q value for the MEI worker was 9.26E-04 sec/m3.
Exposure
Worker - The MEI worker was assumed to be located within a box placed directly over the tank farm area. Exposure point concentrations of chemical emissions (mg/m3) from the tank farm area and retrieval operations were estimated by multiplying the cumulative tank farm emission rate (mg/sec) and retrieval operation emission rate (mg/sec) by the MEI worker Chi/Q value (9.26E-04 sec/m3), respectively. Exposure point concentrations for each volatile chemical emitted from the tank farm area and during retrieval are summarized in Tables D.4. 10 .21 and D.4.10 .22 respectively.
Table D.4.10 .21 Total Alternative Tank Farm Emissions
Table D.4.10 .22 Total Alternative Retrieval Emissions
Chemical intake (dose) was estimated for the MEI worker using the same equation and exposure parameters defined in Section D.2.2.3. Estimated intakes of chemical emissions from the tank farm and retrieval operations for the MEI worker are presented in Tables D.4. 10 .21 and D.4.10 .22, respectively.
Noninvolved Worker - The MEI noninvolved worker was assumed to be located at the point where maximum downwind air concentrations were calculated (100 m [330 ft] from the tank farm and 200 m [660 ft] from the evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm, retrieval operations, evaporator, and vitrification facilities were estimated by multiplying the cumulative tank farm, retrieval, evaporator, and plant emission rates (mg/sec) by their respective MEI noninvolved worker Chi/Q values (4.00E-04 sec/m3 for the tank farm, 2.50E-06 sec/m3 for the evaporator, 4.00E-04 sec/m3 for retrieval, 9.40E-08 sec/m3 for Phase 1 vitrification, and 2.90E-08 sec/m3 for Phase 2 vitrification). Exposure point concentrations for each volatile chemical emitted from the tank farm area, the evaporator, retrieval operations, and the Phase 1 and Phase 2 vitrification facility are summarized in Tables D.4.10 .23, D.4. 10 .24, D.4.10 .25, D.4. 10 .26, and D.4.10 .27 respectively.
Table D.4.10 .23 Total Alternative Tank Farm Emissions
Table D.4.10 .24 Total Alternative Evaporator Emissions
Table D.4.10 .25 Total Alternative Retrieval Emissions
Table D.4.10 .26 Total Alternative Phase 1 Plant Emissions
Table D.4.10 .27 Total Alternative Phase 2 Plant Emissions
Chemical intake (dose) was estimated for the MEI noninvolved worker according to the same equation and exposure parameters used for the MEI worker. Estimated operating chemical emission intakes for the MEI noninvolved worker are presented in Tables D.4. 10 .23, D.4.10 .24, D.4. 10 .25, D.4.10 .26, and D.4. 10 .27 for the tank farm area, evaporator, retrieval operations, and the Phase 1 and Phase 2 vitrification facilities emissions, respectively.
General Public - The MEI general public receptor was assumed to be located at the point where maximum air concentrations were calculated (approximately 22 km [14 mi] from both the tank farm area and evaporator). Exposure point concentrations (mg/m3) of chemical emissions from the tank farm area, the evaporator, retrieval operations, and the vitrification facilities were estimated by multiplying the cumulative emission rates (mg/sec) of each source by their respective MEI general public Chi/Q values (6.60E-08 sec/m3 for the tank farm, 6.60E-08 sec/m3 for the evaporator, 6.60E-08 sec/m3 for retrieval operations, 1.50E-08 sec/m3 for Phase 1 vitrification, and 7.70E-09 sec/m3 for Phase 2 vitrification). Exposure point concentrations for each volatile chemical emitted from the tank farm area, evaporator, retrieval operations, and the Phase 1 and Phase 2 vitrification facilities are summarized in Tables D.4.10 .28, D.4. 10 .29, D.4.10 .30, D.4. 10 .31, and D.4.10 .32, respectively.
Table D.4.10 .28 Total Alternative Tank Farm Emissions
Table D.4.10 .29 Total Alternative Evaporator Emissions
Table D.4.10 .30 Total Alternative Retrieval Emissions
Table D.4.10 .31 Total Alternative Phase 1 Plant Emissions
Table D.4.10 .32 Total Alternative Phase 2 Plant Emissions
The residential or general public intake was calculated according to the equation and exposure parameters presented in Section D.2.2.3. Estimated chemical emission intakes for the MEI general public are presented in Tables D.4. 10 .28, D.4. 10 .29, D.4. 10 .30, D.4. 10 .31, and D.4. 10 .32 for the tank farm area, the evaporator, retrieval operations, and the Phase 1 and Phase 2 vitrification facilities, respectively.
Toxicity Assessment
Toxicity assessment was previously discussed in detail in Section D.4.1.2.4. Cancer slope factors, RfDs, and data sources for each volatile operating chemical emission are summarized in Table D.4.1.11.
Risk Characterization
MEI Worker - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm and retrieval operations are summarized in Tables D.4. 10 .21 and D.4. 10 .22, respectively. The total HI and cancer risk from routine tank farm emissions and retrieval emissions combined are 3.08E-01 and 2.51E-06, respectively.
MEI Noninvolved Worker - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farms, the evaporator, retrieval operations, and Phase 1 and 2 vitrification facilities are summarized in Tables D.4. 10 .23, D.4. 10 .24, D.4. 10 .25, D.4. 10 .26, and D.4. 10 .27, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and vitrification emissions are 1.33E-01 and 1.09E-06, respectively.
MEI General Public - The noncarcinogenic hazards and carcinogenic risk for chemical emissions from the tank farm, evaporator, retrieval operations, and the Phase 1 and Phase 2 vitrification facilities are summarized in Tables D.4.10 .28, D.4. 10 .29, D.4.10 .30, D.4. 10 .31, and D.4.10 .32, respectively. The total HI and cancer risk from combined tank farm, evaporator, retrieval, and vitrification emissions are 7.50E-05 and 6.35E-10, respectively.
D.4.11 NO ACTION ALTERNATIVE (CAPSULES)
This section presents the anticipated remediation risk associated with the No Action alternative for Cs and Sr capsules, as outlined in Volume Two, Appendix B of the EIS.
The radiological risk for this alternative was based on the air emissions and direct exposure from storage operations at WESF. No nonradiological chemical (toxicological) emissions were associated with the capsules.
D.4.11.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.11.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 11 .1 (WHC 1995h and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the workplace.
Table D.4.11 .1 Atmospheric Radiological Emissions for the No Action Alternative (Capsules)
D.4.11.1.2 Transport
The atmospheric transport parameters of the No Action Capsules alternative are presented in Table D.4. 11 .2. The atmospheric radiological operating emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.11 .2 Atmospheric Transport Parameters for the No Action Alternative (Capsules)
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values were 5.40E-07 sec/m3 for the noninvolved worker MEI and 3.40E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 3.70E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.70E-03 sec/m3.
D.4.11.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.11 .3. The table shows the exposure each receptor would receive.
Table D.4.11 .3 Summary of Anticipated Exposure and Risk for the No Action Alternative (Capsules)
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995h and Jacobs 1996). The calculations for the worker exposures from storage operations are as follows:
Storage = (7.61E+02 person-yr) · (2.00E-01 rem/person-yr) = 1.52E+02 person-rem
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a duration of the alternative (not exceed 30 years).
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q value.
D.4.11.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The dose-to-risk conversion factors used were 4.00E-04 LCFs per person-rem for workers and noninvolved workers and 5.00E-04 LCFs per person-rem for the general public.
The radiological dose for each receptor shown in the dose column in Table D.4. 11 .3 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
D.4.12 ONSITE DISPOSAL ALTERNATIVE
This section presents the anticipated remediation risk associated with the Onsite Disposal alternative for Cs and Sr capsules, as outlined in Volume Two, Appendix B of the EIS.
The radiological risk for this alternative was based on the air emissions and direct exposure from storage and packaging operations at WESF. No nonradiological chemical (toxicological) emissions were associated with the capsules.
D.4.12.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.12.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 12 .1 (WHC 1995h and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the workplace.
Table D.4.12 .1 Atmospheric Radiological Emissions for the Onsite Disposal Alternative
D.4.12.1.2 Transport
The atmospheric transport parameters of the Onsite Disposal alternative are presented in Table D.4. 12 .2. The atmospheric radiological operating emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.12 .2 Atmospheric Transport Parameters for the Onsite Disposal Alternative
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values were 5.40E-07 sec/m3 for the noninvolved worker MEI and 3.40E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 3.70E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.70E-03 sec/m3.
D.4.12.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.12 .3. The table shows the exposure each receptor would receive.
Table D.4.12 .3 Summary of Anticipated Radiological Exposure for the On Site Disposal Alternative
The worker population dose is dependent on the number of people in the population and the anticipated dose each individual would receive. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995h and Jacobs 1996). The calculations for the worker exposures from storage and packaging are as follows:
Storage/Packaging = (8.40E+02 person-yr) · (2.00E-01 rem/yr) = 1.68E+02 person-rem
Dry storage monitoring = (4.40E+02 person-yr) · (1.40E-01 rem/yr) = 6.16E+00 person-rem
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for the duration of the alternative (not exceeding 30 years).
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q value.
D.4.12.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The radiological dose for each receptor shown in the combined dose column in Table D.4.12 .4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.12 .4 Summary of Anticipated Risk for the Onsite Disposal Alternative
D.4.13 OVERPACK AND SHIP ALTERNATIVE
This section presents the anticipated remediation risk associated with the Overpack and Ship alternative for Cs and Sr capsules, as outlined in Volume Two, Appendix B of the EIS.
The radiological risk for this alternative was based on the air emissions and direct exposure from storage and overpacking at WESF, and transporting capsules onsite . No nonradiological chemical (toxicological) emissions were associated with the capsules.
D.4.13 .1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.13.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 13 .1 (WHC 1995h and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the work place.
Table D.4.13 .1 Atmospheric Radiological Emissions for the Overpack and Ship Alternative
D.4.13.1.2 Transport
The atmospheric transport parameters of the Overpack and Ship alternative are presented in Table D.4.13.2. The atmospheric radiological operating emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.13 .2 Atmospheric Transport Parameters for the Overpack and Ship Alternative
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values were 5.40E-07 sec/m3 for the noninvolved worker MEI and 3.40E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 3.70E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.70E-03 sec/m3.
D.4.13.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.13 .3. The table shows the exposure each receptor would receive.
Table D.4.13 .3 Summary of Anticipated Radiological Exposure for the Overpack and Ship Alternative
The worker population dose is dependent on the number of people in the population and the anticipated individual dose. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995h and Jacobs 1996). The calculations for the worker exposures from storage and overpacking operations are as follows:
Storage/Overpacking = (1.48E+02 person-yr) · (2.00E-01 rem/person-yr) = 2.84E+01 person-rem
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for the duration of the alternative (not exceeding 30 years).
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.13.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The dose-to-risk conversion factors used were 4.00E-04 LCFs per person-rem for workers and noninvolved workers and 5.00E-04 LCFs per person-rem for the general public.
The radiological dose for each receptor shown in the combined dose column in Table D.4.13.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.13 .4 Summary of Anticipated Risk for the Overpack and Ship Alternative
D.4.14 VITRIFY WITH TANK WASTE ALTERNATIVE
This section presents the anticipated remediation risk associated with the Vitrify With Tank Waste alternative for Cs and Sr capsules, as outlined in Volume Two, Appendix B of the EIS.
The radiological risk for this alternative was based on the air emissions and direct exposure from storage and overpacking operations in WESF, and transporting the overpacked capsules to the vitrification facility. No nonradiological chemical (toxicological) emissions were associated with the capsules.
D.4.14.1 Radiological Risk
The LCF risk to the workers, noninvolved workers, and general public could result from direct exposure and atmospheric emissions from the components associated with this alternative. The risk was determined by analyzing the radiological source term, the transport mechanism, exposure, and the risk associated with the exposure as discussed in the following subsections.
D.4.14.1.1 Source Term
The source term used for the noninvolved worker and general public was the atmospheric radiological emissions presented in Table D.4. 14 .1 (WHC 1995h and Jacobs 1996). The workers would receive a combined dose from the air emissions and from direct exposure from radiation fields in the workplace.
Table D.4.14 .1 Atmospheric Radiological Emissions for the Vitrify with Tank Waste Alternative
D.4.14.1.2 Transport
The atmospheric transport parameters of the Vitrify with Tank Waste alternative are presented in Table D.4. 14 .2. The atmospheric radiological operating emissions were modeled as an elevated release. For modeling purposes, it was assumed that the source term would be released at a point in the 200 Areas represented by the meteorological conditions at the Hanford Meteorological Station. The analysis used the Hanford Meteorological Station joint frequency data from Table D.2.2.1 and Figure D.2.2.1.
Table D.4.14 .2 Atmospheric Transport Parameters for the Vitrify with Tank Waste Alternative
For elevated releases (stack releases), the maximum exposure would not necessarily occur at the closest distance to the source. Air transport modeling indicates that the maximum exposure for the noninvolved worker would occur 200 m (660 ft) from the source (in an east-southeast direction). The maximum exposure for a member of the general public would occur 22 km (14 mi) from the source (i.e., the distance to the Hanford Site boundary in an east-southeast direction from the 200 East Area).
The calculated Chi/Q values were 5.40E-07 sec/m3 for the noninvolved worker MEI and 3.40E-08 sec/m3 for the general public MEI. For the noninvolved worker population of 10,900 occupying an area between 100 m (330 ft) from the source and the Hanford Site boundary, the population-weighted Chi/Q value was 3.70E-04 sec/m3. For the general public population of 376,000 occupying an area outside the Hanford Site boundary within an 80-km (50-mi) radius centered on the 200 Areas, the population-weighted Chi/Q value was 1.70E-03 sec/m3.
D.4.14.1.3 Exposure
The radiological exposure for the alternative is presented in Table D.4.14 .3. The table shows the exposure each receptor would receive.
The worker population dose is dependent on the number of people in the population and the anticipated individual dose. The data were obtained from the Site maintenance and operations contractor and the TWRS EIS contractor (WHC 1995h and Jacobs 1996). The calculations for the worker exposures from storage and overpacking operations are as follows:
Storage/Overpack = (1.40E+02 person-yr) · (2.00E-01 rem/person-yr) = 2.8E+01 person-rem
The MEI worker was assumed to receive a dose of 500 mrem (5.00E-01 rem) per year for a duration of the alternative (not exceeding 30 years).
The noninvolved workers and general public exposures from inhalation of the atmospheric emissions (source term) were converted to a radiological dose in rem using the GENII computer code and applying the appropriate Chi/Q.
D.4.14.1.4 Risk
The LCFs are calculated as the product of the estimated dose times the dose-to-risk conversion factor (Section D.2.2.4). The dose-to-risk conversion factors used were 4.00E-04 LCFs per person-rem for workers and noninvolved workers and 5.00E-04 LCFs per person-rem for the general public.
The radiological dose for each receptor shown in the combined dose column in Table D.4.13.4 was multiplied by the appropriate dose-to-risk conversion factor to produce the LCF risk.
Table D.4.14 .4 Summary of Anticipated Risk for the Vitrify with Tank Waste Alternative
D.4.15 REMEDIATION RISK SUMMARY
This section summarizes the results of the remediation risk assessment presented in Sections D.4.1 to D.4.14 for each of the alternatives. Separate summaries are presented for radiological risk and chemical risk.
D.4.15.1 Radiological Risk
Table D.4.15.1 summarizes the calculated LCF risk associated with radiological exposures for each alternative. Risks are summarized for the workers, noninvolved workers, and the general public. Risks are also summarized for the MEI from each of these receptor groups. The table presents both remediation risk and total risk for each receptor and alternative. The total risk includes the risk from remediation activities plus the risk from post-closure monitoring.
D.4.15.2 Chemical Risk
Tables D.4.15.2 and D.4.15.3 summarize the calculated noncarcinogenic health hazard and carcinogenic risk associated with chemical air emissions for each tank waste alternative. Capsule alternatives are not shown because chemical emissions are not associated with any of these alternatives. Table D.4.15.2 summarizes the nonradiological health hazard (expressed as a HI) for the MEI worker,
Table D.4.15.2 Comparison of Nonradiological Chemical Hazards from Remediation Operations
Table D.4.15.3 Comparison of Nonradiological Chemical Cancer Risks from Remediation Operations
MEI noninvolved worker, and MEI general public for each alternative. Table D.4.15.3 summarizes the nonradiological cancer risk for the MEI worker, MEI noninvolved worker, and MEI general public for each alternative.
D.4.16 UNCERTAINTY
The uncertainties in the risk assessment for tank waste remediation are associated with the source data and source term, transport, exposure pathway, and dose to risk conversion factors. By far the greatest uncertainty is associated with the source data, which are based on the estimated inventory and source terms (e.g., the amount of chemicals and radionuclides released into the environment). The uncertainties associated with the source and source terms are discussed in detail in Volume Five, Appendix K . Other contributors to the routine risk assessment uncertainty are the airborne transport of the released chemicals and radionuclides, accumulation of contaminants in food products, production and distribution of food products, lifestyle and diet of specific individuals or food consumption rates, and dose conversion factors of the contaminants . A detailed discussion of the uncertainties in the remediation risk assessment is presented in Volume Five, Appendix K.
|
NEWSLETTER
|
| Join the GlobalSecurity.org mailing list |
|
|
|
