E.6.0 EX SITU INTERMEDIATE SEPARATIONS ALTERNATIVE
The Ex Situ Intermediate Separations alternative for tank waste would involve constructing and operating vitrification and support facilities, low-level vitrified waste burial vaults, and transfer lines from the tank farms and T Plant to the vitrified facilities. This alternative would also involve transporting retrieved tank waste to a vitrification facility and vehicle traffic of the personnel required to support the alternative. This section analyzes the construction, operation, and transportation risks associated with this alternative.
E.6.1 CONSTRUCTION ACCIDENTS
The potential exists for accidents resulting from construction activities. The construction activities are outlined in Appendix B of the EIS. It should be noted there are no radiological or chemical consequences associated with construction accidents. Occupational injuries, illnesses, and fatalities resulting from potential construction accidents are calculated as follows.
The number of construction personnel was estimated at an average 3.11E+04 person-years (Jacobs 1996). The number of total recordable injuries and illnesses, lost workday cases, and fatalities were calculated using the incidence rates from Table E.1.2.1 as follows:
Total Recordable Cases = (3.11E+04 person-years) · (9.75E+00 incidences/100 person-years) = 3.03E+03
Lost Workday Cases = (3.11E+04 person-years) · (2.45E+00 incidences/100 person-years) = 7.61E+02
Fatalities = (3.11E+04 person-years) · (3.2E-03 fatalities/100 person-years) = 9.94E-01
E.6.2 TRANSPORTATION ACCIDENTS
Under the Ex Situ Intermediate Separations alternative, Hanford Site tank waste would be stabilized by vitrification. The vitrified HLW would be shipped to onsite storage and the LAW would be buried in vaults on the Hanford Site. These waste streams would be transported by pipeline, truck, and rail. In addition to transporting the waste, construction materials and process chemicals would be transported to the Hanford Site by truck and rail. This alternative would also be supported by a work force of employees that would commute to work each day.
E.6.2.1 Radiological Cancer Risk
Radiological exposures resulting from accidents were analyzed using RADTRAN 4 (Neuhauser-Kanipe 1992). Exposures resulting from accidents from the following transportation activities were included in the analysis.
- Transporting residual waste from the SSTs to the processing facility by truck; and
- Transporting waste from MUSTs to the processing facility by truck.
The analysis addressed radiological accident impacts as an integrated population risk (i.e., accident frequencies times consequences integrated over the entire shipping campaign) using RADTRAN 4 and a maximum credible accident using GENII computer codes (Napier et al. 1988).
The population doses were dependent on the accident probability, release quantities, atmospheric dispersion parameters, population distribution parameters, human uptake, and dosimetry models.
Radiological exposure to the MEI was calculated for a bounding scenario accident by GENII computer code (Green 1995). The public and worker dose calculated by GENII were dependent on the release quantities of radioactive material, release duration, receptor location, and meteorology.
E.6.2.1.1 Truck Transport of Retrieved Tank Waste
The receptor dose and LCF risk resulting from the accident analysis for retrieval of MUST waste and SST residuals is presented in Table E.6.2.1 for the integrated population and Table E.6.2.2 for the MEI worker and MEI general public.
Table E.6.2.1 Integrated Radiological Impact from Retrieval Transport Accidents
Table E.6.2.2 MEI Radiological Impact from Retrieval Transport Accidents
There would be no LCFs resulting from an accident while transporting retrieved waste on site.
E.6.2.2 Chemical Exposure
Chemicals transported to the Hanford Site to support the pretreatment and vitrification processes would have the greatest chemical impact. An analysis was performed to 1) identify the hazardous chemicals that could result in the largest toxicological impacts; and 2) evaluate the toxicological impacts of the maximum credible accidents involving the highest hazard chemicals (Green 1995). A preliminary screening analysis was performed to identify the chemicals representing the highest potential toxicological hazard. The highest hazard chemicals in terms of toxicity were determined to be nitric acid, sodium hydroxide, anhydrous ammonia, and dicyclopentadiene. The chemical concentrations resulting from the maximum credible accident at 100 m (330 ft) and the frequency of the accidents (Green 1995) are summarized in Table E.6.2.3.
Table E.6.2.4 compares the respirable concentration of the postulated chemical releases to exposure limits discussed in Section E.1.1.7.
Table E.6.2.4 shows the general public exposure to anhydrous ammonia would exceed the ratio of exposure to ERPG-3 by 1.24E+01 and sodium hydroxide would exceed the ratio of exposure to ERPG-1 by 2.45E+00 for corrosive/irritant chemicals. The magnitude of the anhydrous ammonia exceedance indicates potential lethal effects for the MEI general public.
E.6.2.3 Occupational Injuries and Fatalities
Truck and Rail Transportation
Injuries and fatalities resulting from direct impact of transportation accidents are analyzed in this subsection. Rail and truck transportation activities to transport materials and supplies to the Site for this alternative were estimated (WHC 1995j) and are summarized in Table E.6.2.5.
The number of injuries and fatalities were calculated by multiplying the total distance traveled in each zone shown in Table E.6.2.6 by the appropriate unit risk factors shown in Table E.1.3.1. The distance traveled in the population zones were calculated using the methodology previously discussed in Section E.1.3. The expected injuries and fatalities resulting from transportation accidents associated with the Ex Situ Intermediate Separations alternative are summarized in Table E.6.2.7.
Employee Traffic
In addition to transporting materials and supplies to and from the Hanford Site by truck and rail, Site workers and other personnel required to perform the various activities would be driving to the site in their vehicles. The total person-years to perform the activities was estimated at 8.58E+04.
Each person was assumed to work 260 days of the year. The round-trip distance traveled to work from the Tri-Cities area was estimated at 140 km (87 mi) with an estimated 1.35 passengers per vehicle (DOE 1994a). The total employee vehicle distance was therefore calculated as follows:
(8.58E+04 person-years) · (260 days/year) · (140 km/day) · (1/1.35) = 2.31E+09 km (1.44E+09 mi)
To calculate the expected number of injuries and fatalities resulting from vehicle accidents, the injury/fatality rates discussed in Section E.1.3 were used. The expected number of injuries and fatalities resulting from employee vehicle accidents were calculated as follows:
Injuries = (2.31E+09 km) · (7.14E-07 injuries/km) = 1.65E+03
Fatalities = (2.31E+09 km) · (8.98E-09 fatalities/km) = 2.08E+01
Cumulative Transportation Injuries and Fatalities
The cumulative nonradiological and nontoxicological injuries and fatalities incurred as a direct result of traffic accident impacts are the sum of the truck and rail transport and employee vehicle accidents. The results are summarized in Table E.6.2.8.
E.6.3 OPERATION ACCIDENTS
Operations are discussed in Appendix B. The operations are separated and analyzed according to the following modes of operation:
- Continued operations - Previously discussed in the No Action alternative.
- Retrieval operations - DST waste would be extracted from tanks using slurry pumping. Hydraulic sluicing would be used to remove SST waste. If hydraulic sluicing did not meet waste retrieval goals, robotic arm-based retrieval methods would be used. Pipelines would transfer waste from the tank farms to a pretreatment facility.
- Pretreatment - Pretreatment would consist of sludge washing and chemical processes to separate the waste into HLW and LAW streams. The solids in the tank would be washed to dissolve salts to the extent practical and those salts bearing liquid would be added to the supernatant stream going to Cs removal. The sludge remaining in the tanks would be washed to remove additional solids and to minimize the feed to the HLW vitrification facility.
- Treatment - LAW would be pumped into a LAW vitrification facility where it would be mixed with feed material and vitrified into glass. Vitrification is a high-temperature process where waste is blended with additives and fused into a glass-like form suitable for disposal. The HLW would be routed from a lag storage facility, where it would be temporarily stored before treatment, to a HLW vitrification facility where it would be mixed with feed material (such as glass formers) and then fused into glass.
- Disposal - The LAW glass would be placed into a near-surface retrievable disposal facility on the Hanford Site. A Hanford Barrier would be constructed over the retrievable LAW disposal site to inhibit migration of contaminants or intrusion by humans or animals. The high-level vitrification waste glass would be placed in aboveground storage facility at the Hanford Site. It would then be shipped by rail to an offsite potential geologic repository for permanent disposal.
The potential for accidents exists during the operation of these activities. The dominant accident scenarios analyzed in the following subsections were selected from the Accident Screening Table (Table E.6.3.1). The methodology of the table was previously discussed in Section E.1.1.2.
Table E.6.3.1 Accident Screening Table for the Ex Situ Intermediate Separations Alternative
E.6.3.1 Routine Operation Accidents - Tank Waste Transfers
The dominant routine operations accident during tank waste transfer is the mispositioned jumper accident previously discussed in the No Action alternative in Section E.2.2.1 and summarized as follows:
Source-term - The source-term resulting from a spray release in Section E.2.2.1.1 was calculated to be 52 L (14 gal).
Probability - The frequency of a mispositioned jumper in Section E.2.2.1.2 was 1.1E-02 per year. The Ex Situ Intermediate Separations routine operation activity was based on 25 years of operations; therefore, the probability was calculated to be 2.8E-01.
Radiological Consequences - The radiological consequences presented in Table E.2.2.2 are reproduced in Table E.6.3.2.
Table E.6.3.2 Dose Consequence from Mispositioned Jumper
Radiological Cancer Risk - The LCFs calculated in Section E.2.2.1.4 are the same for the Ex Situ Intermediate Separations alternative. However, the LCF risk (point estimate) is not the same due to the difference in probabilities. The LCFs and the LCF risk are calculated in Table E.6.3.3.
Table E.6.3.3 Latent Cancer Fatality Risk from Mispositioned Jumper
The bounding calculations show all 10 workers would potentially receive fatal dose and assumably die directly after the exposure if the accident occurred. Approximately seven noninvolved workers would receive fatal cancers and two fatal cancers would be incurred to the general public. The nominal scenario calculations show there would be no LCFs.
Chemical Consequences
Potential acute hazards associated with a mispositioned jumper are identical to those summarized in Tables E.2.2.4 (toxic chemicals, nominal conditions), E.2.2.5 (toxic chemicals, bounding conditions), E.2.2.6 (corrosive/irritant chemicals, nominal conditions) and E.2.2.7 (corrosive/irritant chemicals, bounding conditions) for the No Action alternative.
Toxic Impact from Chemical Exposure
Under nominal conditions (Table E.2.2.4), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker, and MEI general public were less than 1.0, indicating that no adverse acute health effects would be expected for these three receptors. Under bounding conditions (Table E.2.2.5), the MEI worker was not evaluated because death would occur from exposure to radionuclides. The cumulative acute hazard ratio for the MEI noninvolved worker was 5.36E+00 for ERPG-2, indicating that reversible acute health effects would be expected. This acute hazard ratio was primarily attributable to mercury (approximately 89 percent of the overall hazard ratio). No adverse acute health effects were predicted for the MEI general public under bounding conditions.
Corrosive/Irritant Impact from Chemical Exposure
Under nominal conditions (Table E.2.2.6), the cumulative acute hazard ratio for the MEI worker was 2.70E+00 for ERPG-3, indicating the potential for irreversible health effects that could be life threatening. This acute hazard ratio was almost entirely attributable to sodium assumed to be equivalent to sodium hydroxide in corrosive/irritant effects. For the MEI noninvolved worker, the cumulative acute hazard ratio for ERPG-1 was 3.00E+00, indicating that only mild, reversible irritant effects would be expected. No acute health impacts were predicted for the MEI general public under nominal conditions. Under bounding conditions (Table E.2.2.7), the MEI worker was not evaluated because death would occur from exposure to radionuclides. For the MEI noninvolved worker, the cumulative acute hazard ratio for ERPG-1 was 4.36E+00, indicating that only mild reversible irritant effects would be expected. No acute health impacts were predicted for the MEI general public under bounding conditions.
Under both nominal and bounding conditions, the probability of a mispositioned jumper is 2.75E-01.
E.6.3.2 Continued Operations Accidents - Waste Storage Tanks
The dominant accident is a hydrogen deflagration in a waste storage tank previously discussed in the No Action alternative in Section E.2.2.2.1 and is summarized as follows.
Source-term - The source-term resulting from the fire in Section E.2.2.2.1 was calculated to be 2.4 L (0.6 gal).
Probability - The frequency of the hydrogen deflagration in a waste storage tank in Section E.2.2.2.2 was estimated to be 7.2E-03 per year. The probability of the scenario based on 25 years of operation was therefore estimated to be 1.8E-01.
Radiological Consequences - The radiological consequences presented in Table E.2.2.8 are reproduced in Table E.6.3.4.
Table E.6.3.4 Dose Consequence from Hydrogen Deflagration in Waste Storage Tank
Radiological Cancer Risk - The LCFs calculated in Section E.2.2.2.4 are the same for the Ex Situ Intermediate Separations alternative. However, the LCF risk (point estimate) is not the same due to the difference in probabilities. The LCR and the LCF risk are calculated in Table E.6.3.5.
Table E.6.3.5 Latent Cancer Fatality Risk from Hydrogen Deflagration in Waste Storage Tank
In the bounding all 10 workers would potentially receive a fatal dose and assumably die directly after the exposure. There would also be 10 LCFs attributed to the exposure to the noninvolved workers and 2 LCFs to the general public if the accident occurred. The nominal scenario calculations show there would be no LCFs.
Chemical Consequences
Potential acute hazards associated with a hydrogen burn in a waste storage tank are identical to those summarized in Tables E.2.2.10 (toxic chemicals, nominal conditions), E.2.2.11 (toxic chemicals, bounding conditions), E.2.2.12 (corrosive/irritant chemicals, nominal conditions) and E.2.2.13 (corrosive/irritant chemicals, bounding conditions) for the No Action alternative.
Under bounding conditions, chemical impacts were not evaluated for the MEI worker because all workers would receive a lethal radiation dose as discussed previously.
Toxic Impact from Chemical Exposure
Under nominal conditions (Table E.2.2.10), the cumulative acute hazard ratio for the MEI worker was 1.57E+00 for ERPG-2, indicating that reversible acute health effects would be expected. This acute hazard ratio was primarily attributable to TOC (approximately 87 percent of the overall ERPG-2 ratio). The TOC is assumed to be equivalent in toxicity to tributylphosphate, which is the most acutely toxic constituent of the organic analytes identified. Tributylphosphate was used as a surrogate because an inventory of the various chemicals that make up the TOC class is not available. For the MEI noninvolved worker, the cumulative acute hazard ratio for ERPG-3 was 9.38E+00, indicating the potential for irreversible health effects that could be life-threatening. This acute hazard ratio was also primarily attributable to TOC (approximately 90 percent of the overall ERPG-3 ratio) However, the MEI noninvolved worker is a hypothetical worker assumed to be located 100m (330 ft) from the source area. The first anticipated noninvolved worker population is located 290 m (950 ft) from the source area and had no cumulative acute hazard ratios greater than 1.0 for any of the ERPGs, indicating that no acute health effects would be expected for the nearest noninvolved worker population. Likewise, no acute health effects were predicted for the MEI general public under nominal conditions.
Under bounding conditions (Table E.2.2.11), the cumulative acute hazard ratio for the MEI noninvolved worker was 4.54E+02 for ERPG-3, indicating the potential for irreversible health effects that could be life-threatening. This acute hazard ratio is primarily attributable to:
- Oxalate (approximately 37 percent of the total hazard ratio);
- Beryllium (approximately 13 percent of the total hazard ratio);
- Cadmium (approximately 14 percent of the total hazard ratio);
- Uranium (approximately 12 percent of the total hazard ratio); and
- TOC (approximately 8 percent of the total hazard ratio).
As discussed previously, this is a hypothetical receptor located 100m (330 ft) from the source. The cumulative acute hazard ratio for the nearest noninvolved worker population located 290 m (950 ft) from the source was 1.65E+00 for ERPG-3, indicating the potential for irreversible health effects that could be life threatening for 335 workers. This hazard ratio was attributable to the same toxic chemicals listed above. This exceedance of the ERPG-3 criterion for the nearest noninvolved worker population would not be expected to result in irreversible health effects or place these workers in a life-threatening situation for the following reasons.
- ERPG-3 is defined as a concentration in which a receptor can be exposed for 1 hour without irreversible health effects. Because the Hanford Site has an in-place emergency response plan designed to evacuate workers within 1 hour of an accident, workers would be expected to evacuate their location and move to an area where potential exposures would be well below ERPG-3. Therefore, this worker population would not be exposed to airborne concentrations that would be either life threatening or result in irreversible health effects.
- The estimated air concentrations of chemicals as a result of this accident were based on very conservative meteorology, which results in movement of a plume directly toward the worker population at a relatively slow rate with minimal wind dispersion. If less conservative meteorological parameters were used, wind dispersion would cause the estimated air concentrations of chemicals to be substantially less, and the ERPG-3 criterion would not be exceeded.
- Only the bounding toxic chemical evaluation exceeded ERPG-3, while the nominal evaluation was well below 1.00E+00 for ERPG-3, suggesting that the noninvolved worker population would not receive an exposure that would result in any permanent health effects.
The next nearest noninvolved worker population is located 1,780 m (5,840 ft) from the source and contains 1,500 workers. The cumulative acute hazard ratio was less than 1.0 for all ERPGs, indicating that no acute health effects would be expected for this population of workers. No acute health impacts were predicted for the MEI general public.
Corrosive/Irritant Impact from Chemical Exposure
Under nominal conditions (Table E.2.2.12), the cumulative acute hazard ratio for the MEI worker was 3.82E+00 for ERPG-3, indicating the potential for irreversible corrosive/irritant effects that could be life threatening. For the MEI noninvolved worker, the cumulative acute hazard ratio for ERPG-3 was 7.89E+01 and would indicate irreversible corrosive/irritant effects that could be life threatening for this hypothetical receptor. This hazard ratio was primarily attributable to sodium, which was assumed to be equivalent to sodium hydroxide in corrosive/irritant effects. For the nearest noninvolved worker population (290 m [950 ft]) composed of 335 workers, the cumulative acute hazard ratio for ERPG-1 was 1.38E+01, indicating that only mild reversible effects would be expected. No acute health impacts were predicted for the MEI general public under nominal conditions.
Under bounding conditions (Table E.2.2.13), the cumulative acute hazard ratio for the MEI noninvolved worker was 1.91E+02 for ERPG-3, indicating irreversible health effects that could be life threatening for this hypothetical receptor. This hazard ratio was primarily attributable to:
- Sodium as sodium hydroxide (approximately 75 percent of the total hazard ratio);
- Chromium (approximately 14 percent of the total hazard ratio); and
- Calcium (approximately 6 percent of the total hazard ratio).
For the nearest noninvolved worker population (290 m [950 ft]) composed of 335 workers, the cumulative acute hazard ratio was 1.74E+00 for ERPG-2, indicating that reversible acute effects would be expected. No acute health impacts were predicted for the MEI general public under nominal conditions.
Under both nominal and bounding conditions, the probability of a hydrogen deflagration event in a waste storage tank is 1.80E-01.
E.6.3.3 Retrieval Accidents
The types of potential accidents associated with retrieval are leaks, sprays, ventilation failure, fire/deflagration, mechanical impacts, and criticality. From the Accident Screening Table (Table E.6.3.1), the accident within design basis identified as having the highest risk was Accident E.4.3.1.10, "loss of filtration."
A tank dome collapse analysis (Shire et al. 1995 and Jacobs 1996) concluded that the annual frequency of the event would be incredible depending on barrier configuration and administrative controls. The collapse of a tank dome would require a heavy vehicle on the dome. Large objects such as the tank 241-SY-101 mixer pump do not represent sufficient weight to cause damage to the tank dome because they are suspended from a support structure in the central pit. Mechanical barriers such as posts spaced closely together would prevent large vehicles from driving on top of the domes without removing the posts. Post removal would be administratively controlled through a controlled locking system. Failure of the barrier configuration and the administrative control system was calculated to be 1.0E-07/year.
E.6.3.3.1 Scenario and Source-term Development for Loss of Filtration
It was postulated that a ventilation heater failure could occur due to an electrical fault resulting in humid air plugging the HEPA filter and filter blowout. A condenser maintenance backflush error could also result in plugging the HEPA filter and filter blowout. Loss of both stages of filtration would allow an unfiltered release LPF of 1.00 for the bounding scenario.
The impact of the postulated accident during retrieval of tank waste would result in an airborne release of the radionuclides in the headspace of the tank. Assuming a respirable concentration of radionuclides in the headspace of 100 mg/m3 (based on a partition fraction between liquid and aerosol of 1.0E-07), a liquid SpG of 1, and a headspace volume of 2,500 m3, the potential source-term from the headspace release was calculated as follows:
(100 mg/m3 ) · (2,500 m3 ) · (1 g/1,000 mg) · (1 L/1,000 g) · (1) = 0.25 L (0.066 gal).
E.6.3.3.2 Probability of Loss of Filtration
The annual frequency of the event was calculated in the potential accident data package (Shire et al. 1995 and Jacobs 1996) as follows:
The failure rate of an electrically powered air heater was calculated to be 8.8E-03/yr based on an hourly failure rate of 1.0E-06. The HEPA filtration system would have a monitoring and alarm system that could detect the change in the differential pressure caused by a filter plug or filter blowout. This system was given a failure rate of 1.0E-03/yr. The annual frequency of this event was therefore calculated to be 8.8E-06. Based on 25 years of operation, the probability was calculated to be 2.2E-04.
E.6.3.3.3 Radiological Consequence from Loss of Filtration
The radiological dose to the receptors from the previous source-term was calculated by the GENII computer code (Napier et al. 1988) using the methodology previously discussed in Section E.1.1.6. The results (Shire et al. 1995 and Jacobs 1996) are summarized in Table E.6.3.6.
Table E.6.3.6 Dose Consequence from Loss of Filtration
E.6.3.3.4 Radiological Cancer Risk from Loss of Filtration
The LCFs and the LCF point estimate risk were calculated for the receptors and are presented in Table E.6.3.7.
Table E.6.3.7 Latent Cancer Fatality Risk from Loss of Filtration
In the bounding scenario all 10 workers would potentially receive a fatal dose and assumably die directly after the exposure. There would also be less than one LCF attributed to the exposure to the noninvolved workers and general public if the accident occurred. The nominal scenario calculations show there would be no LCFs.
E.6.3.3.5 Chemical Consequences from Loss of Filtration
The chemical exposure to the receptors from the postulated accident was calculated in Appendix A of the accident data package (Shire et al. 1995 and Jacobs 1996) and summarized in the exposure column in Tables E.6.3.8 and E.6.3.9 for the nominal and bounding toxic effects, respectively, and Tables E.6.3.10 and E.6.3.11 for the nominal and bounding corrosive/irritant effects, respectively. The tables compare the concentration of postulated chemical releases to acute exposure criteria (ERPGs) discussed in Section 1.1.7.
Under bounding conditions, chemical impacts were not evaluated for the MEI worker because all workers would receive a lethal radiation dose, as discussed previously.
Toxic Impact from Chemical Exposure
Under nominal conditions (Table E.6.3.8) the cumulative acute hazard ratio for the MEI worker was less than 1.0 for all ERPGs, indicating that no adverse acute health effects would be expected. For the MEI noninvolved worker, the cumulative acute hazard ratio was 1.84 for ERPG-1, indicating that only mild, transient acute health effects would be expected. No acute health effects were predicted for the MEI general public under nominal conditions.
Under bounding conditions (Table E.6.3.9), the cumulative acute hazard ratio for the MEI noninvolved worker was 7.27E+01 for ERPG-3, indicating the potential for irreversible health effects that could be life-threatening. This acute hazard ratio is primarily attributable to:
- Uranium (approximately 48 percent of the total hazard ratio);
- Oxalate (approximately 24 percent of the total hazard ratio);
- Mercury (approximately 13 percent of the total hazard ratio); and
- TOC (approximately 7 percent of the total hazard ratio).
As discussed previously, this is a hypothetical receptor located 100m (330 ft) from the source. The cumulative acute hazard ratio for the nearest noninvolved worker population (335 workers) located 290 m (950 ft) from the source was 5.40E+00 for ERPG-2, indicating that reversible acute health effects would be expected. No acute health impacts were predicted for the MEI general public.
Corrosive/Irritant Impact from Loss of Filtration
Under nominal conditions (Table E.6.3.10), the cumulative acute hazard ratio for the MEI worker was 2.11E+00 for ERPG-2, indicating that reversible corrosive/irritant effects would be expected. For the MEI noninvolved worker, the cumulative acute hazard ratio for ERPG-3 was 1.72E+01 and would indicate irreversible corrosive/irritant effects that could be life threatening for this hypothetical receptor. This hazard ratio was primarily attributable to sodium which was assumed to be equivalent to sodium hydroxide in corrosive/irritant effects. For the nearest noninvolved worker population (290 m [950 ft]) composed of 335 workers, the cumulative acute hazard ratio for ERPG-1 was 3.02, indicating that only mild, transient irritant effects would be expected. No acute health impacts were predicted for the MEI general public under nominal conditions.
Under bounding conditions (Table E.6.3.11), the cumulative acute hazard ratio for the MEI noninvolved worker was 2.47E+01 for ERPG-3, indicating irreversible health effects that could be life threatening for this hypothetical receptor. This hazard ratio was primarily attributable to :
- Sodium as sodium hydroxide (approximately 82 percent of the total hazard ratio); and
- Calcium (approximately 9 percent of the total hazard ratio).
For the nearest noninvolved worker population (290 m [950 ft]) composed of 335 workers, the cumulative acute hazard ratio was 4.38 for ERPG-1, indicating that only mild, transient irritant effects would be expected. No acute health impacts were predicted for the MEI general public under nominal conditions.
Under both nominal and bounding conditions, the probability of a loss of filtration event is 2.20E-04 for the MEI worker, MEI noninvolved worker and MEI general public.
E.6.3.4 Pretreatment
Types of potential accidents associated with pretreatment are spills, sprays, and explosions. From the Accident Screening Table (Table E.6.3.1), the design basis accident identified as having the highest risk was a pressurized spray release, Accident 4.5.1.1.2, "line break occurs within vault due to earthquake."
It was postulated that a line break could occur within a ventilated vault because of a design basis earthquake. The vault would be located between the separations facility and the HLW vitrification facility. The pump pressure to the line would be 1,430 kPa (207 psi).
E.6.3.4.1 Scenario and Source-term Development for Seismic Induced Line Break in Vault
It was determined a maximum respirable spray release from the ruptured line with a pump pressure of 1,430 kPa (207 psi) would be approximately 7.6 L/min (2.0 gal/min) (Shire et al. 1995 and Jacobs 1996). The total released quantity would be drawn through a double-stage HEPA filter before being released to the environment.
Assumptions were as follows:
- The spray was limited to 16 hours (960 minutes); and
- HEPA filters provided an assumed LPF of 1.0E-05.
The source-term was calculated as follows:
(7.6 L/minutes) · (960 minutes) · (1.0E-05) = 7.3E-02 L (1.9E-02 gal).
E.6.3.4.2 Probability of Seismic Induced Line Break in Vault
The annual exceedance frequency of the event was assumed to be 6.5E-04 (Shire et al. 1995 and Jacobs 1996). This is the frequency of a 0.23 g design basis earthquake at the Hanford Site. It is assumed the leak would occur given the probability of the design basis earthquake. Based on 25 years of operation the probability was calculated to be 1.6E-02.
E.6.3.4.3 Radiological Consequences of Seismic Reduced Line Break in Vault
The radiological dose to the receptors from the previous source-term was calculated by the GENII computer code using the methodology discussed in Section E.1.1.4. The results (Shire et al. 1995 and Jacobs 1996) are summarized in Table E.6.3.12.
Table E.6.3.12 Dose Consequence for Seismic Reduced Line Break in Vault
E.6.3.4.4 Radiological Cancer Risk of Seismic Induced Line Break in Vault
Based on a dose-to-risk conversion factor of 4.0E-04 LCF per person-rem for the workers and noninvolved workers and 5.0E-04 per person-rem for the general public, the LCFs and the LCF risk (point estimate) were calculated for the receptors and presented in Table E.6.3.13. The calculations show there would be no LCFs attributable to this exposure if the accident occurs for the bounding or nominal scenarios.
Table E.6.3.13 Latent Cancer Fatality Risk from Seismic Induced Line Break in Vault
E.6.3.4.5 Chemical Consequences of Seismic Induced Line Break in Vault
The chemical exposure to the receptors from the postulated accident was calculated in Appendix A of the accident data package (Shire et al. 1995 and Jacobs 1996) and summarized in the exposure column in Tables E.6.3.14 and E.6.3.15 for the nominal and bounding toxic effects, respectively, and Tables E.6.3.16 and E.6.3.17 for the nominal and bounding corrosive/irritant effects, respectively. The tables compare the concentration of postulated chemical releases to acute exposure criteria (ERPGs) discussed in Section 1.1.7.
Toxic Impact from Chemical Exposure
Under nominal conditions (Table E.6.3.14), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker, and MEI general public were less than 1.0, indicating that no adverse acute health effects would be expected for these three receptors. Under bounding conditions (Table E.6.3.15), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker, and MEI general public were less than 1.0, indicating that no adverse acute health effects would be expected for these three receptors.
Corrosive/Irritant Impact from Chemical Exposure
Under nominal conditions (Table E.6.3.16), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker, and MEI general public were less than 1.0, indicating that no adverse acute health effects would be expected for these three receptors. Under bounding conditions (Table E.6.3.17), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker, and MEI general public were less than 1.0, indicating that no adverse acute health effects would be expected for these three receptors.
Under both nominal and bounding conditions, the probability of a pretreatment spray release is 1.63E-02.
E.6.3.5 Treatment Accidents
The treatment section of the Accident Screening Table (Table E.6.3.1) shows the radiological consequences to be insignificant for all credible accidents. The dominant accident was identified as Accident 4.5.4.4 "A Canister Dropped Due to Mechanical Failure or Human Error."
E.6.3.5.1 Source-term for Breached Canister
The source-term for a 24-hour release through a two-stage HEPA filter was calculated in Shire (Shire et al. 1995 and Jacobs 1996) to be 2.5E-06 grams (8.8E-08 ounces).
E.6.3.5.2 Radiological Consequences of Immobilization Accident
Accident 4.5.4.4, "a canister dropped due to mechanical failure or human error," has the highest dose consequences. As calculated in the accident data package (Shire et al. 1995 and Jacobs 1996) the radiological dose to the receptors are shown in Table E.6.3.18.
Table E.6.3.18 Dose Consequence for Breached Canister
E.6.3.5.3 Probability of Breached Canister
The annual frequency of the accident was considered in the accident data package (Shire et al. 1995 and Jacobs 1996) to be 6.0E-01. This was based on the frequency of a canister being dropped during transfer of 3.0E-04 per transfer and 2,000 transfers per year. Based on 25 years of operation the probability was calculated to be 1.0E+00.
E.6.3.5.4 Radiological Cancer Risk of Breached Canister
The LCFs and the LCF risk (point estimate) were calculated for the receptors and presented in Table E.6.3.19.
Table E.6.3.19 Latent Cancer Fatality Risk from Breached Canister
The calculations show there would be no LCFs attributable to this exposure for the bounding or nominal scenarios.
E.6.3.5.5 Chemical Consequences of Breached Canister
No chemical consequences were evaluated in (Shire et al. 1995 and Jacobs 1996) since the release would first pass through a two-stage HEPA filters that would reduce the source-term to a very small amount, well below the cumulative ratio of exposure to ERPG-1 values for toxic or corrosive/irritant chemicals.
E.6.3.6 Disposal/Storage Accidents
No design basis accidents resulting in a radiological or chemical consequences to the receptors were identified. This is largely due to the vitrified waste form of the material and the engineered structural packaging of the vitrified LAW in burial vaults and vitrified HLW in shipping containers.
E.6.3.7 Beyond Design Basis Accidents
The beyond design basis accident is a seismic event resulting in the collapse of a SST. In the event of a 0.43 g earthquake, a SST could potentially collapse (LANL 1995). This event is not dependent on the remediation alternative but has the same annual frequency regardless of the alternative that is chosen. The length of time unremediated waste would remain in tanks that have not been backfilled would vary depending on the alternative and would affect the probability of the event. The probability of the event is the product of the annual frequency of the earthquake and the number of years the waste remains untreated in the unstabilized tanks.
At smaller annual frequencies, larger earthquakes could occur resulting in greater destruction and larger numbers of LCF to the onsite and offsite populations. In addition to population exposures from the collapsed SSTs, the impact to other Hanford Site facilities and operations would potentially add to the chemical and radiological risk. This would be a severe earthquake that would cause catastrophic structural damage in the Tri-Cities and the Hanford Site with expected extensive loss of life. There would be injuries and fatalities resulting from collapsed buildings and homes, fires, and traffic accidents. However, this section evaluates the radiological and chemical impacts resulting from the collapse of one SST.
E.6.3.7.1 Source-Term Development
It was conservatively assumed that the radiological and chemical contaminants in the headspace are available for release. The collapse of a portion of the dome and overburden compresses the vapor in the headspace as it descends, enhancing the vapor release rate by a sudden pressure difference. Assuming for each tank a respirable concentration of contaminants in the headspace of 100 mg/m3, a liquid SpG of 1.5, and a headspace volume of 1,000 m3 (Shire et al. 1995 and Jacobs 1996), the potential source-term contribution from the headspace release was calculated as follows:
(100 mg/m3) · (1 g/1,000 mg) · (1 L/1,000 g) · (1,000 m3) · (1/1.5) = 6.67E-02 L (1.8E-02 gal).
It was conservatively assumed that the liquids had been pumped from the tanks so that the tanks contained only solids and the MAR was 2,500 L (660 gal) for each tank. It was postulated that the fall of the dome and overburden generated an air movement sufficient to suspend a fraction of the MAR. Assuming the respirable release fraction to be 2.0E-03 (Shire et al. 1995 and Jacobs 1996), the potential source-term contribution was calculated as follows:
(2,500 L [660 gal]) · (2.0E-03) = 5.0 L (1.3 gal).
It was postulated that prevailing winds resuspend a respirable fraction of the MAR (2,500 L [660 gal]). A respirable release fraction of 4.0E-05/hr for 24 hours was assumed. The potential source-term contribution from resuspension was calculated as follows:
(2,500 L [660 gal]) · (4.0E-05/hr) · (24 hr) = 2.4 L (0.6 gal).
The combined source-term for the acute release is calculated as follows:
(6.67E-02 L) + (5.00E+00 L) + (2.4 L) = 7.4 L (2.0 gal).
E.6.3.7.2 Probability of a Beyond Design Basis Earthquake
This earthquake has a calculated annual exceedance frequency of approximately 1.40E-04 (WHC 1996b). The probability for this scenario based on 25 years of operation was therefore estimated to be 3.5E-03.
E.6.3.7.3 Radiological Consequences from a Beyond Design Basis Earthquake
The radiological dose to the receptors from the previous source-term was calculated by the GENII computer code (Napier et al. 1988) using the methodology previously discussed in Section E.1.1.6. The results are presented in Table E.6.3.20.
Table E.6.3.20 Dose Consequence from Seismic Event
E.6.3.7.4 Radiological Cancer Risk from a Beyond Design Basis Earthquake
The LCFs and LCF point estimate risk are presented in Table E.6.3.21.
Table E.6.3.21 Latent Cancer Fatality Risk from Seismic Event
In the bounding scenario, all 10 workers would potentially receive a fatal dose and assumably die directly after the exposure. There would also be 10 LCFs attributed to the exposure to the noninvolved workers and two LCFs to the general public if the accident occurred. The nominal scenario calculations show there would be no LCFs.
E.6.3.7.5 Chemical Consequences from a Beyond Design Basis Earthquake
Potential acute hazards associated with a beyond design basis earthquake are identical to those summarized in Tables E.2.2.16 (toxic chemicals, nominal conditions), E.2.2.17 (toxic chemicals, bounding conditions), E.2.2.18 (corrosive/irritant chemicals, nominal conditions) and E.2.2.19 (corrosive/irritant chemicals, bounding conditions) for the No Action alternative.
Under bounding conditions, chemical impacts were not evaluated for the MEI worker because all workers would receive a lethal radiation dose, as described previously.
Toxic Impact from Chemical Exposure
Under nominal conditions, the cumulative acute hazard ratio for the MEI worker was 2.64E+00 for ERPG-1, indicating that only mild transient effects would be expected. For the MEI noninvolved worker, the cumulative acute health hazard was 2.59E+00 for ERPG-3, indicating the potential for irreversible health effects that could be life threatening. This acute hazard ratio was primarily attributable to TOC (approximately 84 percent of the total hazard ratio). The TOC is assumed to be equivalent in toxicity to tributylphosphate, which is the most acutely toxic constituent of the organic analytes identified. Tributylphosphate was used as a surrogate because an inventory of the various chemicals that make up the TOC class is not available. The cumulative acute hazard ratio for the nearest noninvolved worker population consisting of 335 workers located 290 m (950 ft) away was less than 1.0 for all ERPGs, suggesting that no acute health effects would be expected.
Under bounding conditions (Table E.2.2.17), the cumulative hazard ratios for the MEI and nearest noninvolved worker population (335 workers located 290 m (950 ft) away) were 2.15E+03 and 7.80E+00 for ERPG-3, respectively. These ratios were primarily attributable to:
- Uranium (approximately 47 percent of the total hazard ratio);
- Oxalate (approximately 24 percent of the total hazard ratio); and
- Mercury (approximately 13 percent of the total hazard ratio).
This exceedance of the ERPG-3 criterion for the nearest noninvolved worker population would not be expected to result in irreversible health effects or place these workers in a life-threatening situation for the following reasons.
- ERPG-3 is defined as a concentration in which a receptor can be exposed for 1 hour without irreversible health effects. Because the Hanford Site has an in-place emergency response plan designed to evacuate workers within 1 hour of an accident, workers would be expected to evacuate their location and move to an area where potential exposures would be well below ERPG-3. Therefore, this worker population would not be exposed to airborne concentrations that would be either life threatening or result in irreversible health effects.
- The estimated air concentrations of chemicals as a result of this accident were based on very conservative meteorology, which results in movement of a plume directly toward the worker population at a relatively slow rate with minimal wind dispersion. If less conservative meteorological parameters were used, wind dispersion would cause the estimated air concentrations of chemicals to be substantially less, and the ERPG-3 criterion would not be exceeded.
- Only the bounding toxic chemical evaluation exceeded ERPG-3, while the nominal evaluation was well below 1.00E+00 for ERPG-3, suggesting that the noninvolved worker population would not receive an exposure that would result in any permanent health effects.
The cumulative acute hazard ratio for the next nearest noninvolved worker population, composed of 1,500 people and located 1,780 m (5,840 ft) away, was 2.15E+00 for ERPG-2, indicating that reversible acute health effects would be expected. The cumulative acute hazard ratio for the MEI general public was 1.76E+00 for ERPG-2, indicating that reversible acute health effects would be expected.
Corrosive/Irritant Impact from Chemical Exposure
Under nominal conditions (Table E.2.2.18), the cumulative acute hazard ratios for the MEI worker, MEI noninvolved worker and nearest noninvolved worker (335 workers at 290 m [950 ft]) were 2.47E+01, 5.10E+02 and 1.85E+00, respectively, for ERPG-3, indicating the potential for irreversible health effects that could be life threatening. These ratios were almost entirely attributable to sodium, which was assumed to be equivalent to sodium hydroxide in corrosive/irritant effects. As discussed previously, this exceedance of the ERPG-3 criterion would not be expected to result in irreversible or life threatening health effects. For the next nearest noninvolved worker population (1,500 workers at 1,780 m [5,840 ft]), the cumulative acute hazard ratio was 1.20E+00 for ERPG-1, indicating that only mild irreversible irritant effects would be anticipated. For the MEI general public, the cumulative acute hazard ratio was less than 1.0 for all ERPGs, and no acute health effects would be expected.
Under bounding conditions, the cumulative acute hazard ratios for the MEI noninvolved worker and nearest noninvolved worker (335 workers at 290 m [950 ft]) were 7.31E+02 and 2.65E+00, respectively, for ERPG-3, indicating the potential for irreversible health effects that could be life threatening. These acute hazard ratios were primarily attributable to:
- Sodium (approximately 83 percent of the total hazard ratio); and
- Calcium (approximately 10 percent of the total hazard ratio).
As discussed previously, this exceedance of the ERPG-3 criterion would not be expected to result in irreversible or life threatening health effects.
For the next nearest noninvolved worker and MEI general public, the cumulative acute hazard ratios were 1.74E+00 and 1.42E+00, respectively, for ERPG-1, indicating that only mild, transient irritant effects would be expected.
Under both nominal and bounding conditions, the probability of a seismic event is 3.50E-03.
E.6.3.8 Occupational Injuries and Fatalities
The number of operation personnel to support the Ex Situ Intermediate Separations alternative was estimated (Jacobs 1996) and is summarized as follows:
- Retrieval operations - 3.74E+04 person-years; and
- Vitrification operations - 1.73E+04 person-years.
The total recordable injuries and illnesses, lost workday cases, and fatalities were calculated as follows:
Total Recordable Cases = (5.47E+04 person-years) · (2.2E+00 incidences/100 person-years) = 1.20E+03
Lost Workday Cases = (5.47E+04 person-years) · (1.1E+00 incidences/100 person-years) = 6.02E+02
Fatalities = (5.47E+04 person-years) · 3.2E-03 fatalities/100 person-years) = 1.75E+00
E.6.4 POST-REMEDIATION ACCIDENT
E.6.4.1 Deflagration in Storage Tank
After 99 percent of the tank waste has been removed from each tank, the probability of a tank generating enough hydrogen to exceed the LFL is considered to be incredible.
E.6.4.2 Seismic-Induced Rupture of Stabilized Tanks
As discussed in Section E.4.4.2, displacement on a fault that would increase exposure to the waste after remediation is considered incredible. The tanks would most likely crack, allowing increased infiltration to the groundwater.
E.6.5 SUMMARY OF ACCIDENTS
The potential consequences from nonradiological and nonchemical accidents that include occupational and transportation impacts are summarized in Table E.6.5.1. The LCFs associated with representative accidents for each component of the alternative are summarized in Table E.6.5.2 along with the probability of the accident. The chemical hazards associated with representative accidents for each component of the alternative are summarized in Table E.6.5.3. The chemical hazard is expressed as an exceedance of the ERPG threshold values.
Table E.6.5.1 Summary of Potential Nonradiological/Nonchemical Accident Consequences
Table E.6.5.2 Summary of Potential Radiological Accident Consequences
Table E.6.5.3 Chemical Exposures Resulting from Potential Operations and Transportation Accidents
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