E.2.0 NO ACTION ALTERNATIVE (TANK WASTE)
This section analyzes the risk resulting from potential accidents associated with the No Action alternative. The No Action alternative is to continue the following activities:
- Perform routine management and maintenance activities; and
- Continue pumping and evaporating liquid for 10 years.
This section analyzes the transportation and operation risk associated with this alternative. Because tanks and facilities would not be constructed under this alternative, there would be no risk from construction.
E.2.1 TRANSPORTATION ACCIDENTS
Transportation activities associated with this alternative include employees commuting to work each day.
E.2.1.1 Radiological Cancer Risk
All operations would be conducted within established operating parameters for the tanks and would not involve transporting radioactive materials by container. Therefore, there would be no radiological cancer risk resulting from transportation. Accidents involving the transportation of waste in the transfer lines are discussed in Section E.2.2.
E.2.1.2 Chemical Exposure
Because there would be limited transportation of toxic materials (such as lubricants that are used in continued operations), it is extremely unlikely there would be any accidents resulting in chemical exposures. Therefore, transportation accidents involving chemical exposures were not quantified.
E.2.1.3 Occupational Injuries and Fatalities
Employee Traffic Accidents
Workers and other personnel required to perform the various activities would drive to the Hanford Site in their vehicles. The total person-years to perform the activities was estimated at 1.04E+05 (Jacobs 1996).
Each person was assumed to work 260 days a year. The round-trip distance traveled to work from the Tri-Cities area was estimated at 140 kilometers (km) (87 miles [mi]) with an estimated 1.35 passengers per vehicle (DOE 1994a). The total employee vehicle distance was therefore calculated to be 2.80E+09 km (1.74E+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 are calculated as follows:
Injuries = (2.80E+09 km) · (7.1E-07 injuries/km) = 2.00E+03
Fatalities = (2.80E+09 km) · (8.98E-09 fatalities/km) = 2.52E+01
E.2.2 OPERATION ACCIDENTS
The potential exists for accidents resulting from routine operation activities. The routine operations are discussed in Volume Two, Appendix B.
The dominant accident scenarios analyzed in the following subsections were selected from the Accident Screening Table (Table E.2.2.1). The accidents listed in Table E.2.2.1 were taken from the accidents analysis data package (Shire et al. 1995 and Jacobs 1996). The methodology of screening was previously discussed in Section 1.1.2.
Table E.2.2.1 Accident Screening Table for the No Action Alternative (Tank Waste)
E.2.2.1 Continued Operations Accident - Tank Waste Transfers
Continued operations include transferring liquid waste from the SSTs to an evaporator where the solids and liquid are separated. Types of radiological releases resulting from potential accidents associated with continued operations include sprays, leaks, fires/deflagrations, explosions, and ventilation. From Table E.2.2.1 the credible accident (accidents with a frequency of occurring greater than 1.0E-06 per year) identified as having the highest risk was Accident 4.1.7: "mispositioned jumper in SST double-contained receiver tank pump pit with cover off."
A pressurized-liquid spray release from a mispositioned jumper was postulated to occur in an SST double-contained receiver tank (DCRT) pump pit that services the transfer from DCRT to DST or pumps into or out of a receiver tank. A jumper is a short connection pipe that is used in a jumper pit to route tank waste transfers from one line to another line in sending tank waste to a specific location.
E.2.2.1.1 Scenario and Source-term Development for - Mispositioned Jumper
This analysis was based on the following assumptions:
- A jumper was mispositioned and pinhole leaks develop at both ends of the jumper;
- The pump pressure was 1.43E+06 Pascals (Pa) (207 pounds per square inch [psi]);
- The maximum spray leak from each end was calculated to be 0.027 liters per minute (L/min) 0.007 gallons per minute (gal/min) or 0.054 L/min (0.014 gal/min) total;
- All spray particles were assumed to evaporate to less than 10 m before reaching the ground on their calculated trajectory; therefore, 100 percent of the spray was considered respirable;
- The fine spray is not detectable with installed leak detection devices;
- The pump pit was unintentionally left uncovered;
- The release time was for two shifts or 16 hours (960 min); and
- The source-term consists of 70 percent SST liquids and 30 percent SST solids.
Source-term - Assuming a spray duration of two shifts or 16 hours, the source-term was calculated as follows:
(0.054 L/min) · (960 min) = 52 L (14 gal)
E.2.2.1.2 Probability of Mispositioned Jumper
The frequency of a mispositioned jumper in a SST DCRT pump pit with its cover off was calculated to range from 1.1E-02 per year to 8.0E-03 per year (Shire et al. 1995 and Jacobs 1996). For conservatism, the frequency of 1.1E-02 was assumed for calculating risk. Waste transfers would take place for up to 10 years; therefore, the probability of the accident was calculated to be 1.1E-01.
E.2.2.1.3 Radiological Consequence from Mispositioned Jumper
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 1.1.6. The results, which were taken from the accident data package (Shire et al. 1995 and Jacobs 1996), are summarized in Table E.2.2.2.
Table E.2.2.2 Dose Consequence from Mispositioned Jumper
E.2.2.1.4 Radiological Cancer Risk from Mispositioned Jumper
The LCF risk is the product of the dose to the receptor measured in rem, the dose to risk conversion factor, and the probability of the event. A dose-to-risk conversion factor of 8.0E-04 LCF per person-rem for the workers, MEI worker, and MEI noninvolved worker was used because the individual doses were greater than 20 rem. Dose-to-risk conversion factors of 4.0E-04 LCF per person-rem for the noninvolved worker and 5.0E-04 LCF per person-rem for the general public were used, because the individual doses were less than 20 rem.
Using the workers as an example, a dose to the workers of 5.9E+02 person-rem would result in an estimated 4.7E-01 latent cancer deaths if the accident were to occur. Factoring in the probability of 1.1E-01 the LCF risk (point estimate) was calculated as follows:
( 5.9E+02 rem) · (1.1E-01) · (8.0 E-04 LCF/rem) = 5.2E-02 LCF
The LCF risks for each receptor are calculated in Table E.2.2.3.
Table E.2.2.3 Latent Cancer Fatality Risk from Mispositioned Jumper
The bounding calculations show all 10 workers would potentially receive a fatal dose from radiation if the accident occurred. Approximately seven noninvolved workers would receive fatal cancers, and two LCFs would be incurred to the general public. The nominal scenario calculations show there would be no LCFs.
E.2.2.1.5 Chemical Consequences of Mispositioned Jumper
The chemical exposure to the receptors from the postulated accident were calculated in Appendix A of the accident data package (Shire et al. 1995 and Jacobs 1996 and Jacobs 1996 ) and summarized in the exposure column in Tables E.2.2.4 and E.2.2.5 for nominal and bounding toxic effects, and Tables E.2.2.6 and E.2.2.7 for nominal and bounding corrosive/irritant effects, respectively. The tables compare the concentration of the postulated chemical releases to acute exposure criteria (ERPGs) discussed in Section 1.1.7.
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 since 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 3.0, 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 since 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 1.10E-01.
E.2.2.2 Continued Operations Accident - Waste Storage Tanks
Types of radiological releases resulting from potential accidents associated with unstabalized tank waste are fires, deflagrations, and tank leaks. From Table E.2.2.1 the credible accident identified as having the highest risk was Accident 7.1: "hydrogen deflagration in waste storage tank."
E.2.2.2.1 Scenario and Source-term Development for Hydrogen Deflagration in Waste Storage Tank
Hydrogen could be generated in tank waste, rise into tank headspace, and reach the concentrations necessary for combustion. Ignition would occur in the tank headspace during a 1-hour time period when the gas concentration exceeds the LFL. Turbulence accompanying rapid combustion could suspend waste as aerosols and pressure drive some of the particulate out the ventilation system into the environment.
Source-term - The MAR was assumed to be 5.0E+05 L (1.3E+05 gal), the ARF RF = 6.5E-06, and the LPF = 7.5E-01. The source-term was calculated as follows:
(5.0E+05 L) · (6.5E-06) · (7.5E-01) = 2.4 L (0.6 gal)
E.2.2.2.2 Probability of Hydrogen Deflagration in Waste Storage Tank
The frequency of a hydrogen deflagration in a waste storage tank was estimated at 7.2E-03 per year for the tank farms (LANL 1995). The probability for this scenario based on 100 years of operation was therefore estimated to be 7.2E-01.
E.2.2.2.3 Radiological Consequence from Hydrogen Deflagration in Waste Storage Tank
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 1.1.6. The results are presented in Table E.2.2.8.
Table E.2.2.8 Dose Consequence from Hydrogen Deflagration in Waste Storage Tank
E.2.2.2.4 Radiological Cancer Risk from Hydrogen Deflagration in Waste Storage Tank
In the bounding scenario a ll 10 workers would potentially receive a fatal dose and would 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 LCFs and LCF point estimate risk are presented in Table E.2.2.9. The nominal scenario calculations show there would be no LCFs.
Table E.2.2.9 Latent Cancer Fatality Risk from Hydrogen Deflagration in Waste Storage Tank
E.2.2.2.5 Chemical Consequences from Hydrogen Deflagration in Waste Storage
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 ) and summarized in the exposure column in Tables E.2.2.10 and E.2.2.11 nominal and bounding toxic effects, respectively and Tables E.2.2.12 and E.2.2.13 for nominal and bounding corrosive/irritant effects, respectively. The tables compare the concentration of the postulated chemical releases to acute exposure criteria (ERPGs) discussed in Section 1.1.7.
Under bounding conditions c hemical 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 1.57 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 9.38, 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 1.65 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 1.00 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 (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 3.82 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 1.74 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 7.20E-01.
E.2.2.3 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.2.2.3.1 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 specific gravity (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 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) · (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) · (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.2.2.3.2 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 100 years of operation was therefore estimated to be 1.40E-02.
E.2.2.3.3 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.2.2.14.
Table E.2.2.14 Dose Consequence from Seismic Event
E.2.2.3.4 Radiological Cancer Risk from a Beyond Design Basis Earthquake
The LCFs and LCF point estimate risk are presented in Table E.2.2.15.
Table E.2.2.15 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.2.2.3.5 Chemical Consequences from a Beyond Design Basis Earthquake
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.2.2.16 and E.2.2.17 for the nominal and bounding toxic effects, respectively, and Tables E.2.2.18 and E.2.2.19 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.2.2.16), 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. No acute health effects are calculated to occur for the MEI general public under nominal conditions.
Under bounding conditions (Table E.2.2.17), the cumulative hazard ratios for the MEI and nearest noninvolved worker (335 workers located 290 m [950 ft] away) were 2.15E+03 and 7.80 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 1.00 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 (5,840 ft) away, was 2.15 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. 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 1.00 for ERPG-3, suggesting that the noninvolved worker population would not receive an exposure that would result in any permanent 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 1.20 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 (Table E.2.2.19), 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 2.65, 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).
Based on the discussion presented above, no irreversible corrosive/irritant effects would be anticipated for the nearest noninvolved worker population.
For the next nearest noninvolved worker and MEI general public, the cumulative acute hazard ratios were 1.74 and 1.42, 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 1.40E-02.
E.2.2.4 Occupational Injuries and Fatalities from Operations
The total person-years required for operations was estimated at 1.04E+05 (Jacobs 1996) for the 100 years of continued operations. The total recordable injuries or illnesses, lost workday cases, and fatalities were calculated as follows:
Total Recordable Cases = (1.04E+05 person-years) · (2.2E+00 incidences /100 person-years) = 2.29E+03
Lost Workday Cases = (1.04E+05 person-years) · (1.1E+00 incidences/100 person-years)= 1.14E+03
Fatalities = (1.04E+05 person-years) · (3.2E-03 fatalities/100 person-years) = 3.33E+00
E.2.3 POST-REMEDIATION ACCIDENT
For the No Action (tank waste) alternative, the waste would remain in the tanks and the tanks would not be stabilized. During the 100-year institutional control period, the tanks would be maintained. After the 100 years there would be no additional maintenance of the aging tanks (the design life of the tanks would be exceeded) and the tanks would deteriorate and lose their structural strength. With the tanks in an unstable condition, a seismic event (a 0.2 gravity earthquake with an annual frequency of 8.0E-04) collapses the tank dome into the tanks resulting in an acute release of contaminants followed by a chronic release at much lower levels until the waste would be covered with earth by natural forces.
Source-Term Development
It was conservatively assumed that all 177 tanks collapse and 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 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, the potential source-term contribution from the headspace release for 177 tanks was calculated as follows:
(100 mg/m3) (1 g/L,000 mg) · (1 L/1,000 g) · (1,000 m3) · (1/1.5) · (177) = 1.18E+01 L (3.1 gal)
It was conservatively assumed that the liquids had drained from leaks in the tanks so that the surface was dry and crumbly and the MAR was 2,500 L (660 gal) for each tank. It was postulated that the fall of the dome and overburden generated a substantial air movement to suspend a fraction the MAR. Assuming the respirable release fraction to be 2.0E-03 (Shire et al. 1995 and Jacobs 1996), the potential source-term contribution from entrainment for all 177 tanks was calculated as follows:
(2,500 L) · (2.0E-03) · (177) = 8.85E+02 L (234 gal)
The combined source-term for the acute release is calculated as follows:
(1.18E+01 L) + (8.85E+02 L) = 8.97E+02 L (237 gal)
Following the initial release, no corrective action would be taken and the waste would continually be released by air currents lifting a fraction of the waste into the air for 1 year. After the first year it was assumed the waste would be covered by natural forces. It was assumed that the dome and overburden covers most of the waste surface reducing the MAR to 10 percent or 250 L (66 gal) , and a respirable release fraction of 4.0E-05/hr was assumed. The source-term for the chronic release for one year from 177 tanks is calculated as follows:
(2.50E+02) · (4.0E-05/hr) · (8.74E+03 hr/yr) · (177) = 1.55E+04 L (4,090 gal)
Consequence for Tank Dome Collapse
The nominal tank inventory was used in calculating the radiological dose to the receptors. It was assumed that the offsite population size and location remained the same and the onsite population of people living on the Hanford Site was 10 percent of the current Hanford population or 1,090. The radiological dose to the receptors was calculated by the GENII computer code (Napier et al. 1988) using the methodology previously discussed in Section E.1.1.6.
The radiological consequences to the onsite population would result in approximately 42 LCFs. E xposure to toxic chemicals that would exceed the ERPG-3 threshold values by a factor of 2.25E+02.
The radiological consequences to the offsite populations would result in approximately 4 LCFs. The population living closest to the Hanford Site would receive an exposure to toxic chemicals that would exceed the ERPG- 1 threshold value by a factor of 1.08E+01 indicating they would suffer from mild, transient health effects.
E.2.4 SUMMARY OF ACCIDENTS
The potential consequences from nonradiological and nonchemical accidents that include occupational and transportation impacts are summarized in Table E.2.4.1 The LCFs associated with representative accidents for each component of the alternative are summarized in Table E.2.4.2 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.2.4.3. The chemical hazard is expressed as an exceedance of the ERPG threshold values.
Table E.2.4.1 Summary of Potential Nonradiological/Nonchemical Accident Consequences
Table E.2.4.2 Summary of Potential Radiological Accident Consequences
Table E.2.4.3 Chemical Exposures Resulting from Potential Operations and Transportation Accidents
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