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7 Strategic Alternatives Seven principal alternatives for Molten Salt Reactor Experiment (MSRE) salt remediation have been identified (Peretz, 1996c) and are quoted below. Some of the defined alternatives address in general a range of treatment options. These alternatives are grouped according to the disposition of MSRE fuel salts. The chapter then offers commentary on these alternatives, with a basis for rejecting all but the last and with a discussion of why permanent geologic disposal end points are too far in the future to derive meaningful strategy. PERMANENT DISPOSAL IN THE DRAIN TANKS Alternative 1: No Action. Continue to store the MSRE Mel and flush salts in their respective drain tanks, in their current condition. Assume all facility operations eventually cease. Alternative 2: Enhanced Storage. Continue to store the MSRE fuel and flush salts in their respective drain tanks, but implement and operate enhancements to control reactive gases, prevent nuclear criticality, and contain radioactive materials. DISPOSAL OF ALL KEY CONTAMINANTS IN TTIE FEDERAL REPOSITORY Alternative 3: Dispose of the Salt, Including Uranium, in the Federal Repository. 65
66 ANEVALUATION OF DOE ALTERNATIVES FOR MSRE Remove the MSRE fuel and flush salts from their drain tanks. Stabilize the salts as appropriate for shipment. Ship the salts to [NEL Idaho National Engineering Laboratory] as spent fuels in accordance with the Programmatic ETS [Environmental Impact Statement] for DOE Department of Energy] spent nuclear fuel. Convert the salt to oxide in the INEL waste calciner. Store the calcine at INEL until the proposed remote- handled immobilization facility becomes available. Vitrify the calcine in the remote-handled immobilization facility. Ship the vitrified waste to the Federal repository for ultimate disposal. DISPOSAL OF KEY CONTAMINANTS IN THE SALT RESIDUE IN THE WASTE ISOLATION PILOT PLANT (WIPP) Alternative 4: Transfer the Uranium to the Materials Disposition Program and Dispose of the Salt Resistive in WIPP. Remove the MSRE fuel and flush salts from their drain tanks. Separate the uranium from the salts using fluoride volatility or another process. Convert the UFO "uranium hexafluoride] to U3O~ [uranium oxide] and place the oxide in storage at ORNE tOak Ridge National Laboratory] Radiochemical Development Facility (RDF) for future disposition in the Materials Disposition Program (MDP). Stabilize the salts and store (in RH- TRU [remote-handled transuranic] canisters) at ORNL until WIPP is available. Ship to WIPP for permanent disposal. Chemical reactions in the salt can lead to separation (via volatile compounds) of the Missile material from the matrix. In most commercial spent fuels (oxides), this hazard does not exist. The instability of the fluoride salts may limit or preclude transportation options.
STRATEGIC ALTERNATIVES DISPOSAL OF KEY CONTAMINANTS IN SALT RESIDUE IN THE FEDERAL REPOSITORY Alternative Sa: Transfer the Uranium to the MAP, Vitrify the Salt in the DWPF /(Defense Waste Processing Facility], and Dispose of the Salt Residue in the Federal Repository. Remove the MSRE fuel and flush salts from their drain tanks. Separate the uranium from the salts using fluoride volatility or another process. Convert the UFO to U3O~ and place the oxide in storage at ORNE Radiochemical Development Facility (RDF) for future disposition in the Materials Disposition Program (MDP). Stabilize the salts and ship to Savannah River. Dissolve the salts and bleed into the waste stream being fed into the DWPF. Store the waste in glass logs at Savannah River until the Federal repository is available. Ship the vitrified waste to the Federal repository for ultimate disposal. Alternative Sb: Transfer the Uranium to the MAP, Process the Salt by Electroref ning, ant! Dispose of the Salt Residue in the Federal Repository. Remove the MSRE fuel and flush salts from their drain tanks. Construct an electroref~ner [facility] at ORNL. Separate the zirconium and rare earths from the salt by. electrorefining and convert them to a metal waste form to be managed with similar wastes at ANL-W "Argonne National Laboratory-West]. Separate the uranium and other radioactive materials from the salt. Electrorefine this material in a chloride salt electrorefiner to separate the uranium. Convert the uranium to U3O~, place the oxide in storage at the ORNE RDF, and interface with the national 233U repository for disposal. Dispose of the chloride salt along with similar wastes generated at ANL. Separate the transuranics, actini`des, and cesium and place in a bismuth metal waste form. Either qualify 67
68 AN EVALUATION OF DOE ALTERNATIVES FOR MSRE this waste for disposal in the Federal repository, or develop a vitrification program for this material. Separate the strontium from the salt and place in long- term storage for decay. Stabilize the salt residue and transfer to a low-level waste storage facility. REUSE OF THE SALT Alternative 6: Transfer the Uranium to the MDP and Transfer the Salt to Another Program for Reuse. Remove the MSRE Mel and flush salts from their drain tanks. Separate the uranium from the salts using fluoride volatility or another process. Convert the UFO to U3O~ and place the oxide in storage in the ORNE RDF. Interact as necessary with the uranium MDP, as in alternatives 4 and Sa. Stabilize the salts and transport the salt to Los Alamos for use. INTERIM STORAGE Alternative 7: Transfer the Uranium to the MDP and Place the Salt Residue in Interim Storage. Remove the MSRE fuel and flush salts from the drain tanks. Separate the uranium from the salts by fluoride volatility. Convert the UFO to U3Os and place the oxide in storage in the ORNE RDF. Interface with the national 233U repository at the ORNE RDF. Stabilize the salts by the addition of a chemical getter. Package the salts in a form compatible with repository containers such as the RH-TRU canister. Store the salt waste in the ORNE waste storage facilities until a permanent disposition mode becomes available.
STRATEGIC ALTERNATIVES 69 There are five general options for interim storage that appear representative, as given below. Alternatives 7b, 7c, and 7d all require shipping of waste products for interim storage off-site and revised acceptance criteria for storage. Alternative 7e is based on additional proposals for new forms of processing at ORNL. Alternative 7a: Transfer the Uranium to the MDP, Stabilize the Salt Residue with a Fluorine Getter, and Store at ORAL. Alternative 7b: Transfer the Uranium to the MDP, Convert Radioactive Materials in the Salt into Metallic and Other Waste Forms by Electroref ning, and Store at ANL-W. Alternative 7c: Calcine the Salt, Including the Uranium, and Store the Calcine at INEL. Alternative 74: Transfer the Uranium to the MDP, Incorporate the Salt Resicl?ve in Borosilicate Glass, and Store at Savannah River. Alternative 7e: Transfer the Uranium to the MDP, Construct a Salt Conversion Facility at ORNT, Convert the Salt Resiciz~es to Glass or Phosphate Waste Forms, and Store at ORAL. RATIONALE FOR REJECTING THE FIRST SIX ALTERNATIVES Alternatives ~ and 2 are not attractive as permanent solutions because the drain tanks lie below the water table (creating a criticality hazard) and constitute shallow subsurface storage of transuranic waste (which is contrary to present DOE practice).
70 AN EVALUATION OF DOE ALTERNATIVES FOR MSRE For alternatives 3, 4, and 5, ultimate disposition requires the availability of repositories not yet in operation or constructed. Other problems with these options include off-site transportation of the chemically unstable salt medium and the incompatibility of fluoride salts with a glass waste form. Alternatives 3 and 4 are mutually exclusive ideally, because the Mel salts should be classified legally either as defense-related TRU waste or as high-level waste or spent Mel, not both. A definitive classification decision would appear to aid the decision- making process here by eliminating one of these alternatives. If there were other uses for the radioactive salt mixture (this is doubtful because it contains plutonium and fission products) and if transportation requirements would allow the transport of a salt medium that is unstable in the presence of radiation (this too seems doubtful), alternative 6 would be attractive, as noted in Peretz (1996c). Thus, it is advisable to evaluate interim storage as a realistic objective (Peretz, 1996c) in selecting technical process options. INTERIM VERSUS PERMANENT STORAGE AND DISPOSAL In reviewing the alternatives for longer-term remediation activities, proposed or planned, the pane! excluded consideration of the multiple issues involved in very long term or "permanent" waste disposal. That topic comes under the jurisdiction of many groups and agencies and involves time scales well beyond the year 2000. Waiting for a better definition of the regulatory and technical issues involved in the acceptability of a waste form for ultimate disposal is not, in the panel's judgment, a satisfactory decision at this time, given the known and anticipated hazards of the MSRE. The panel notes that determination of the ultimate geologic waste disposal system is not essential to the selection of a process to be used in the cleanup of the Mel and flush salt tanks, although the process chosen will affect waste disposal costs. The panel assumes that the eventual long-term disposal procedures will be adaptable to handling a variety of materials, in some cases requiring welI-established methods for further processing. Accordingly, the panel believes that attempts to anticipate possible
STRATEGIC ALTERNATIVES 71 eventual long-term storage criteria and disposal processes are fruitless at this time and are secondary to efforts to evaluate options for near-term remediation work and interim, on-site storage. In summary, a final disposal form cannot be selected at this time because final repository criteria are not yet established. Definitive criteria, though desirable, remain conjectural, with final resolution probably beyond the time horizon of the MSRE cleanup project. However, cleanup work on the salts need not be driven by these . considerations. The panel notes that chemical reactions that are going on can lead to further separation of the Missile material from the salt matrix. In most commercial spent fuels (oxides), this hazard does not exist. It appears feasible to isolate the uranium from the solvent salt and to convert both of these fractions to stabilized materials suitable for safe and secure interim storage on-site. Of the on-site interim storage possibilities, combining the MSRE mixture of 232U and 233U with existing inventories of 233U in the MDP program may be undesirable due to the containment and measurement challenges created by the gaseous daughters of 232U (see Appendix C).