Electrometallurgical Techniques for DOE Spent Fuel Treatment Final Report (2000) / Chapter Skim
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3 The Electrometallurgical Process at Argonne National Laboratory
3 The Electrometallurgical Process at Argonne National Laboratory
Pages 25-44
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From page 25... ...
The electrometallurgical treatment process for driver and blanket fuel comprises four stages: disassembly of the fuel elements with an element chopper; electrochemical removal of the uranium from the stainless-steel-clad fuel element pieces in an electrorefiner; consolidation of the electrodeposited uranium and removal of the entrained salt in a cathode processor; and finally, casting of the uranium product from the cathode processor into an ingot in a casting furnace. Down blending of the highly enriched uranium (HEW)
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From page 26... ...
Laug, and J.R. Krsul, Process Description for Blanket Fuel Treatment Operations, NT Technical Memorandum No.
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THE ELECTROMETALLURGICAL PROCESS AT ARGONNE NATIONAL LABORATORY ~ r FIGURE 3.2 Driver fuel assembly. SOURCE: Argonne National Laboratory.
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From page 28... ...
The chopped blanket fuel segments are fed directly into the anode basket assemblies of the Mark-V anode-cathode module. As part of ANL' s demonstration project criterion that required a blanket throughput rate of 150 kg per month sustained for one month,4 the blanket element chopper was used to process 3.5 blanket fuel assemblies or 66 blanket fuel elements for a total of 164.4 kg of uranium.
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From page 29... ...
A small stirring propeller inserted through the ER cell cover into the cadmium pool provides agitation. The Mark-IV ER's overall anode batch size of 16 kg, achieved by using dual anode assemblies in parallel with a single serial cathode.
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From page 30... ...
In the anodic dissolution mode, the fuel dissolution baskets serve as the anode, and the cadmium pool serves as the cathode: the uranium is electro-chemically oxidized from the chopped fuel elements as U3+, transported through the melt by forced convection, and then reduced at the surface of the cadmium pool, where it dissolves in the cadmium. (Reduction of plutonium at the cadmium cathode did not occur because of the low concentration of plutonium in the salt and careful voltage regulation.)
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From page 31... ...
As part of ANL's demonstration project,5 the Mark-IV electrorefiner was used to treat twelve driver assemblies over a two-month period at an average rate of 24 kg of uranium per month compared to the target criterion of 16 kg (~4 driver assemblies) per month over a three-month period.6 Mark-V Electrorefiner The processing capacity of the Mark-IV ER is inadequate to permit timely processing of blanket fuel, which exists in much larger quantities than driver fuel.
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From page 32... ...
FICURE 3~ Scbem~c of me -V ~ec~oreAner SOURCE: Argonne N~Uon~1 L~or~ory. ~~ ~~ ~~ ~~ ~~ ~~ ma_ A -- -- -- -- -it domon~on pr~cct UC1~ was added to the mch ~ ~ concon~on of 4 to 7 At A
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From page 33... ...
Washing consists of rotating the anode basket assembly in the ACM without the passage of current. An automated sequence involving a stripping step, washing step, deposition step, and a second washing step constituting an operational cycle appears to have mitigated the problem,8 with some decrease in overall efficiency.
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From page 34... ...
, which has evolved from earlier induction furnaces designed at ANL-E, provides a means to reduce the 235U enrichment of the driver fuel product from the cathode processor by the addition of depleted uranium resulting from the cathode processor and to consolidate further the uranium product. Its components are similar to those of the cathode processor except that there is no condenser stage and associated receiver crucible to collect the distillate.
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THE ELECTROMETALLURGICAL PROCESS AT ARGONNE NATIONAL LABORATORY FIGURE 3.8 Schematic of the cathode processor. SOURCE: Argonne National Laboratory.
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From page 36... ...
The operating parameters associated with the casting furnace include the crucible coating, temperature control, and pressure control. A crucible coating is required in the casting furnace to minimize the interaction of molten uranium with the graphite crucible and to prevent the cast ingot from adhering to the crucible walls.
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From page 37... ...
. FABRICATION OF WASTE FORMS Metal Waste Form Following the electrorefining operations the stainless-steel cladding hulls are left in the anode basket, along with the noble metal fission products (Zr, Mo, Ru, Rh, Pd.
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From page 38... ...
. Ceramic Waste Form Significant amounts of fission products and transuranic elements accumulate in the LiCl-KC1 electrolyte used in the electrorefining process.
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From page 39... ...
The standard or reference ceramic waste form is made with 75 mass % salt-loaded zeolite and 25 mass % of a commercial glass that acts as a binder. The fission product chlorides are allowed to build up in the salt until a sodium chloride limit is reached.
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In summary, the operating parameters for the production of the ceramic waste form have been developed and applied successfully to operations with radioactive materials at the demonstration scale. All the equipment for
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From page 41... ...
Pressureless Sintering ANL is also investigating alternatives to use of the HIP for ceramic waste form fabrication. In particular, a process of pressureless sintering, or consolidation, is being studied that may have certain advantages over the HIP process.
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From page 42... ...
Recommendation: Studies to compare the type, abundance, and radionuclide inventory of minor and trace phases between ceramic waste forms produced by pressureless sintenng versus the HIP process should be given high priority in the post-demonstration phase. COMMITTEE ANALYSIS OF ALTERNATIVE METHODS FOR TREATMENT OF DOE SNF A variety of other methods, besides electrometallurgical technology, are either in use or have been proposed for the treatment of spent nuclear fuel.
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From page 43... ...
a high-temperature chlorination step that operates at approximately 1500 °C and converts metallic fuel and cladding materials to gaseous chloride compounds, (2) a molten zinc chloride bed that removes the TRU chlorides and most of the fission products and operates at approximately 400 °C, (3)
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From page 44... ...
Although plasma arc processing has been used successfully to treat nonradioactive and low-level radioactive wastes, significant research, development, and demonstration would be needed to process SNF because of the much higher fission product and fissile material content. With regard specifically to EBR-II fuels, extensive work would have to be performed to ensure that the plasma arc process would be compatible with safely processing potentially pyrophoric uranium, and volatile and reactive sodium metal.
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