3.8 COMPARISON OF ACTIVITIES ASSOCIATED WITH THE ALTERNATIVES
The alternatives described in this section provided a range of alternatives from continued storage under the No Action alternative to retrieval and treatment of as much of the waste as practical under the ex situ alternatives. These alternatives also provided for varying levels of waste treatment from containment under the In Situ Fill and Cap alternative to extensive immobilization of all retrieved waste using vitrification under the Ex Situ Intermediate Separations alternative. It should be recognized that there are differences in the level of development between the alternatives, which means there are additional uncertainties associated with the data for some of the alternatives.
Closure for each of the alternatives (except No Action and Long-Term Management ) is described to assess the cumulative impacts only. Each of the alternatives included continued routine operations, which included monitoring, maintenance, and waste management activities. Closure will be the subject of future NEPA decision making.
Major activities for each of the tank waste alternatives are summarized as follows:
- No Action alternative:
- The waste would be left in the current state. Current operations would be continued for 100 years, at which time administrative control would assumed to be lost.
- Long-Term Management alternative:
- DST waste would be retrieved and transferred to replacement DSTs at 50-year intervals (two times) during the 100-year period.
- The SST waste would remain in the current state.
- Current operations would be continued for 100 years, at which time administrative control would assumed to be lost.
- In Situ Fill and Cap alternative:
- All of the tank waste would remain onsite where it would be disposed of in place following DST waste evaporation and tank stabilization operations.
- No measures would be taken to immobilize the waste.
- Minimal construction would be required (no Tank Farm Confinement Facilities are assumed to be required).
- In Situ Vitrification alternative:
- All of the tank waste would remain onsite where it would be vitrified (turned into glass) and disposed of in place.
- Considerable construction would be involved in building the Tank Farm Confinement Facilities over each tank farm.
- In Situ Vitrification has not been attempted on this scale before and would require development.
- Ex Situ Intermediate Separations alternative:
- Major construction would be involved building the retrieval systems and processing, disposal, and support facilities. -
- All tank waste practicable (assumed to be 99 percent) would be retrieved and processed into vitrified HLW or LAW.
- LAW would be vitrified and disposed of onsite in a retrievable manner in near-surface vaults, and HLW would be vitrified and shipped to the potential geologic repository for final disposal.
- Ex Situ No Separations (Vitrification or Calcination) alternative:
- Major construction would be involved with building the retrieval systems, HLW processing facility, and support facilities.
- All tank waste practicable (assumed to be 99 percent) would be retrieved and processed into vitrified or calcined HLW.
- All recovered waste would be disposed of in the potential geologic repository.
- Ex Situ Extensive Separations alternative:
- Major construction would be involved with building the retrieval, processing, and disposal facilities.
- All tank waste practicable (assumed to be 99 percent) would be retrieved and processed into vitrified HLW or vitrified LAW.
- The volume of HLW requiring transportation and disposal would be minimized by extensive separations of waste into HLW and LAW streams.
- HLW would be disposed of at the potential geologic repository and LAW would be disposed of onsite in vaults.
- Ex Situ/In Situ Combination 1 alternative :
- Tanks would be selected for retrieval and processing based on their potential contribution to long-term risk.
- This alternative would use a combination of in situ and ex situ waste treatment aimed at achieving acceptable risk levels at a lower cost than ex situ treatment of all tank waste.
- Using the aforementioned assumption, the waste from approximately 70 of the tanks would be retrieved and the remaining tanks would be filled and disposed of in place.
- Considerable construction would be involved in building retrieval systems, processing, and disposal facilities. These facilities would be similar in type, but smaller than those described for the Ex Situ Intermediate Separations alternative.
- Retrieved HLW would be vitrified and shipped to the potential geologic repository; retrieved LAW would be vitrified and disposed of onsite in vaults; and waste that is not recovered would be disposed of in place.
- Ex Situ/In Situ Combination 2 alternative:
- Tanks would be selected for retrieval and processing based on their potential contribution to long-term risk.
- This alternative would use a combination of in situ and ex situ waste treatment aimed at achieving acceptable risk levels at a lower cost than the Ex Situ/In Situ Combination 1 alternative.
- Using the aforementioned assumption, the waste from approximately 25 of the tanks would be retrieved and the remaining tanks would be filled and disposed of in place.
- Considerable construction would be involved in building retrieval systems, processing, and disposal facilities. These facilities would be similar in type, but smaller than those described for the Ex Situ Intermediate Separations alternative.
- Retrieved HLW would be vitrified and shipped to the potential geologic repository; retrieved LAW would be vitrified and disposed of onsite in vaults; and waste that was not recovered would be disposed of in place.
- Phased Implementation alternative:
Phase 1- Two demonstration-scale processing facilities would be constructed. One facility would process LAW, and one facility would process both LAW and HLW.
- Selected HLW would be retrieved and processed.
- Immobilized HLW and LAW would be stored onsite for disposition during Phase 2.
- Major construction would be involved with building the retrieval, processing, disposal, and support facilities.
- All tank waste practicable (assumed to be 99 percent) would be retrieved and processed into vitrified HLW or LAW.
- LAW would be vitrified and disposed of in a retrievable manner onsite in near-surface vaults. HLW would be vitrified and shipped to the potential geologic repository for final disposal.
Major activities for each of the capsule alternatives are summarized as follows:
- No Action alternative:
- Storage of capsules would continue in WESF for a period of 10 years, at which time one of the other alternatives would have to be implemented.
- Onsite Disposal alternative:
- Capsules would be retrieved, packaged into canisters (3 m [10 ft] long), and placed in drywells for indefinite storage.
- Monitoring and maintenance would continue for 100 years, at which time administrative control is assumed to be lost.
- Overpack and Ship alternative:
- Capsules would be retrieved and packaged into sealed canisters (4.5 m [15 ft ] long).
- Canisters would be overpacked into Hanford Multi-Purpose Canisters for interim storage and disposal at the potential geologic repository.
- Vitrify with Tank Waste alternative:
- Capsules would be retrieved, cut up, and the contents would be vitrified with the HLW from the tanks.
- This alternative assumes that a tank waste alternative using ex situ vitrification would be selected.
- Following vitrification, the capsule waste would become part of the vitrified HLW for disposal at the potential geologic repository.
A comparison of the waste volumes produced, schedule, and cost for the alternatives is presented in Table 3. 8 .1 for tank waste and in Table 3. 8 .2 for capsules.
Table 3.8 .1 Comparison of Tank Waste Alternatives
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