3.5 CESIUM AND STRONTIUM CAPSULE ALTERNATIVES
3.5.1 No Action Alternative (Capsules)
3.5.1.1 Overview
The capsules No Action alternative would involve the continued storage of the cesium capsules and strontium capsules in WESF. Current planning indicates that WESF will be maintained until approximately 2007. Selecting this alternative would require that DOE select an alternate storage method for the capsules within the next 10 years. If the No Action alternative were selected for implementation, one of the other capsule alternatives would have to be selected and implemented by 2007. This will be considered in the Cesium and Strontium Capsule Management Plan.
3.5.1.2 Process Description
Cesium and strontium capsules would continue to be stored in water-filled basins. The capsules would continue to be monitored for signs of leakage and physical change, and the facility would be maintained to provide for continued safe management.
3.5.1.3 Construction
No major construction activities would take place under this alternative. Limited construction activities would be required to complete life extension programs required for continued safe operations.
3.5.1.4 Operations
The operational activities associated with this alternative would involve the continued storage and management of these capsules at WESF.
3.5.1.5 Post Remediation
There would be no post-remediation activities associated with the No Action alternative. Administrative controls would be assumed to be effective until another capsule alternative were implemented.
3.5.1.6 Schedule, Sequence, Cost
A schedule for major activities for this alternative is shown in Table 3.5.1. The estimated cost for this alternative is summarized in Table 3.5.2.
Table 3.5.1 Schedule - No Action Alternative (Capsules)
Table 3.5.2 Cost - No Action Alternative (Capsules)1
3.5.1.7 Implementability
Implementing this alternative would include continued storage of the capsules in WESF and present no new processes or technology challenges. This alternative would meet all applicable regulations (Section 6.2).
3.5.2 Onsite Disposal Alternative
3.5.2.1 Overview
The Onsite Disposal alternative would involve removing the capsules from their current storage in water-filled basins at WESF and packaging them in 3-m [10-ft]-long canisters for onsite disposal. Disposal would consist of placing the sealed canisters into onsite engineered subsurface wells at specified intervals to provide safe, long-term, passively-cooled disposal (Figure 3.5.1). Information used in describing cesium and strontium capsule alternatives is from Disposition of Cesium and Strontium Capsules Engineering Data Package for the TWRS EIS (WHC 1995h and Jacobs 1996).
Figure 3.5.1 Capsules - Onsite Disposal Alternative
Construction activities associated with this alternative would involve minor modifications to WESF for capsule packaging and building the Drywell Disposal Facility. Operations would involve placing the capsules into sealed canisters and placing the canisters in the drywells for disposal.
3.5.2.2 Process Description
Cesium and strontium capsules would continue to be stored in water-filled basins until the packaging and canister handling facilities were ready to begin operations. Disposal of the capsules would involve the following process steps: 1) retrieve the capsules from storage basins; 2) inspect the capsules for integrity; 3) place the capsules in a rack to support the capsule within the canister; 4) insert the capsules into canisters (three or four capsules placed in each canister); 5) seal the canisters by welding closed; 6) decontaminate and inspect the canisters; 7) place the canisters into drywells for disposal; and 8) monitor the capsules and maintain the facility.
3.5.2.3 Construction
The subsurface disposal facility would be the main construction activity for this alternative. This facility would cover approximately 3.8 hectares (ha) (9.4 acres [ac]) including a 30-m (100-ft)-wide surrounding buffer zone. The proposed location is shown in Figure 3.5.2. The site would be leveled, and security fencing and an estimated 672 drywells would be installed (Figure 3.5.3). The drywells would be 4.6 m (15 ft) deep by 0.76 m (2.5 ft) in diameter. A steel encasement would be placed into each hole to house the canister (Figure 3.5.4). A shielded transporter vehicle would be designed and constructed to place the capsules into the drywells.
Capsule packaging operations would require modifications and upgrades to WESF. These modifications would involve installing equipment and utilities to perform remote capsule handling and packaging, as well as canister welding, decontamination, and inspection.
3.5.2.4 Operation
The major operational activities for this alternative would include the following:
- Operating the capsule/canister packaging facility;
- Transporting the canisters to the disposal facility;
- Placing the canisters into the drywells;
- Placing intrusion prevention barriers over the drywells; and
- Monitoring and maintaining the disposal facility.
3.5.2.5 Post Remediation
Post-remediation activities would consist of decontamination and decommissioning of capsule packaging facilities and closure of the disposal facility. Decontamination and decommissioning activities associated with this alternative would include facility decontamination. Contaminated equipment would be decontaminated to the extent possible and disposed of according to State and Federal regulations. Closure of the disposal facilities would involve placing intrusion prevention barriers over the drywells.
3.5.2.6 Schedule, Sequence, Cost
The schedule of major activities for this alternative is shown in Table 3.5.3. The cost associated with this alternative is shown in Table 3.5.4.
Table 3.5.3 Schedule - Onsite Disposal Alternative
3.5.2.7 Implementability
Implementing this alternative would involve storage practices used periodically in the past and thus would present no new technology challenges.
This alternative would not meet the land disposal requirements of RCRA for hazardous waste. Near-surface disposal of HLW would not meet DOE policy for disposal of readily retrievable HLW in a potential geologic repository (Section 6.2).
Figure 3.5.2 Capsules - Onsite Disposal Location
Figure 3.5.3 Capsules Onsite Disposal Arrangement (Conceptual)
Table 3.5.4 Cost - Onsite Disposal Alternative 1
Figure 3.5.4 Capsule Dry-Well Disposal Assembly
3.5.3 Overpack and Ship Alternative
3.5.3.1 Overview
The Overpack and Ship alternative would consist of placing the capsules into canisters ( 4.6 m [ 15 ft] long), which then would be overpacked into Hanford Multi-Purpose Canisters. Four canisters containing capsules would be placed into each Hanford Multi-Purpose Canister. The Hanford Multi-Purpose Canisters would be stored temporarily onsite pending shipment and disposal at the potential geologic repository (Figure 3.5.5).
Construction activities for this alternative would involve modifying WESF to support capsule packaging operations. Operations would involve packaging the capsules into sealed canisters, overpacking the canisters into Hanford Multi-Purpose Canisters for interim storage, and transporting the Hanford Multi-Purpose Canisters by rail to the potential geologic repository. Final design of the canister packaging would include design criteria for waste acceptance at the potential geologic repository.
3.5.3.2 Process Description
Cesium and strontium capsules would continue to be stored in water-filled basins until the packaging facilities were ready to begin operations. Overpacking the capsules would involve the following process steps.
- Retrieve capsules from storage basins.
- Inspect capsules for integrity.
- Place capsules in a rack to support the capsule within the canister.
- Insert capsule into canisters (three to four capsules placed in each canister).
- Seal canister by welding closed.
- Decontaminate and inspect canisters.
- Overpack sealed canisters into Hanford Multi-Purpose Canisters.
- Place canisters into storage.
- Monitor and maintain canisters.
3.5.3.3 Construction
Capsule packaging would require minor modifications and upgrades to WESF. These modifications would involve installing equipment and utilities and modifying existing facilities to perform remote capsule handling and packaging, as well as canister welding, decontamination, and inspection activities.
Interim storage of the Hanford Multi-Purpose Canisters containing the sealed capsule canisters would require the construction of a concrete storage pad similar to the interim HLW storage pads. The interim storage location would be adjacent to the HLW interim storage associated with the tank waste Ex Situ Extensive Separations alternative or other ex situ alternatives .
3.5.3.4 Operation
The major operational activities for this alternative would include the following.
- Remove capsules from wet storage.
- Operate packaging facility.
- Transport Hanford Multi-Purpose Canisters to onsite interim storage pad and cover with a shielding cask.
- Monitor Hanford Multi-Purpose Canisters in interim storage.
- Transport Hanford Multi-Purpose Canisters to the potential geologic repository for disposal.
3.5.3.5 Post Remediation
After all of the capsules were packaged and transported to the interim storage pad, the equipment installed for capsule handling and packaging would be decontaminated and decommissioned. After transporting the Hanford Multi-Purpose Canisters to the repository, the storage pad associated with the interim storage of capsules would be decontaminated and decommissioned.
Figure 3.5.5 Capsules - Overpack and Ship Alternative
3.5.3.6 Schedule, Sequence, Cost
The schedule of activities for this alternative is shown in Table 3.5.5. The cost associated with this alternative is shown in Table 3.5.6.
Table 3.5.5 Schedule - Overpack and Ship Alternative
Table 3.5.6 Cost - Overpack and Ship Alternative 1
3.5.3.7 Implementability
This alternative would use common practices, which present no new technology issues. This alternative might not meet the land disposal restrictions of RCRA because of the characteristic corrosivity of the cesium chloride and strontium fluoride. Also, assuming the waste was mixed waste, it would not meet the DOE restriction against disposal of mixed waste in the first potential geologic repository. Also, the powder waste form of the strontium fluoride would not meet the waste acceptance requirements to immobilize particulate waste (Section 6.2). Further evaluation would be required to resolve technical and programmatic concerns associated with disposal of the cesium and strontium capsules in the potential geologic repository.
3.5.4 Vitrify with Tank Waste Alternative
3.5.4.1 Overview
Vitrifying the capsule contents with the tank waste would involve removing the capsule contents, dissolving or suspending it in a slurry, possibly chemically processing it, and blending it into the vitrification feed stream at the HLW vitrification facility. This would combine the high-activity cesium chloride and strontium fluoride from the capsules with the HLW waste for vitrification. Following the vitrification step, the cesium and strontium would be handled in the same manner as described previously for HLW glass. This eventually would lead to offsite disposal in the potential geologic repository (Figure 3.5.6).
This alternative could be implemented only if one of the ex situ alternatives involving vitrification were selected for the tank waste.
Construction activities associated with this alternative would involve installing the equipment required to remove the capsule contents, processing the cesium chloride and strontium fluoride, and feeding the capsule waste into the HLW vitrification feed stream. This equipment would be installed in a dedicated area of the HLW vitrification facility.
The capsules would be taken from their current storage location to the HLW vitrification facility where they would be cut up, possibly chemically processed, and metered into the waste stream, which would be fed to the HLW vitrification melter. Following remediation, the capsule contents would be a part of the vitrified high-level tank waste and stored onsite temporarily awaiting transport and disposal at the potential geologic repository.
3.5.4.2 Process Description
Cesium and strontium capsules would continue to be stored in water-filled basins at WESF until the HLW vitrification facility was operating and ready to accept the capsules. Vitrifying the capsule contents with the tank waste would involve retrieving the capsules from storage basins; transporting the capsules to the HLW facility in shielded transport casks; dismantling the capsules and remove the cesium and strontium salts; and blending the capsule contents into the HLW stream.
3.5.4.3 Construction
This alternative would require additional construction within the HLW vitrification facility to accommodate capsule-related activities. Construction in the HLW vitrification facility would include shielding and remote equipment to cut up the capsules, removing the contents, chemically treating the cesium chloride and strontium fluoride if required, and blending the capsule material into the HLW feed stream.
3.5.4.4 Operation
Operations for this capsule alternative would be conducted in the HLW vitrification facility and WESF and include the following.
- Continue storing the capsules in WESF until all capsules are removed.
- Remove and truck transport the capsules to the HLW vitrification facility in shielded transport casks.
- Cut up the capsules and remove the contents.
- Perform chemical processing of the capsule contents as required.
- Blend the capsule contents into the vitrification feed stream by slowly metering the dissolved cesium chloride and slurry containing strontium fluoride just before the waste enters the HLW melter.
- Decontaminate and shred the empty capsule containers.
- Dispose of the shredded capsule container materials onsite at the low-level waste burial grounds.
Figure 3.5.6 Capsules - Vitrify with Tank Waste Alternative
3.5.4.5 Post Remediation
Following vitrification, the contents of the capsules would be incorporated into the vitrified HLW. The HLW produced would be stored onsite temporarily and then transported to the potential geologic repository for permanent disposal.
After all HLW was been vitrified, the equipment and facilities dedicated to capsule processing in the HLW vitrification facility would be decontaminated and decommissioned. Contaminated equipment would be disposed of according to State and Federal regulations. The capsule facility portion of the HLW vitrification facility would be decommissioned along with the HLW vitrification facility.
3.5.4.6 Schedule, Sequence, Cost
The schedule of activities for this alternative is provided in Table 3.5.7. Cost associated with this alternative is shown in Table 3.5.8.
3.5.4.7 Implementability
This alternative could be implemented only if one of the ex situ alternatives were selected. This cesium and strontium could require chemical processing to remove the chloride and fluoride from the cesium and strontium salts. The cesium and strontium would need to meet the required feed specifications that would be developed for the HLW stream as part of the vitrification process. This alternative would meet all applicable regulations for disposal of hazardous, radioactive, or mixed waste assuming that the hazardous waste components were adequately treated during waste processing or vitrification.
Table 3.5.7 Schedule - Vitrify with Tank Waste Alternative
Table 3.5.8 Cost - Vitrify with Tank Waste Alternative 1
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