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OCR for page 65
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.
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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.
OCR for page 67
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
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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.
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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).
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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
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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).
Representative terms from entire chapter:
drain tanks
