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AN ASSESSMENT OF CONTINUED R&D INTO AN ELECTROMETALLURGICAL APPROACH FOR TREATING DOE SPENT NUCLEAR FUEL
statements (EISs), including site-specific ones, that will provide the framework within which the DOE must operate to safely, reliably, and efficiently manage and prepare for disposal of its inventory of SNF. Issues being addressed include transportation, characterization, stabilization, interim storage, and technology development for ultimate storage.
CATEGORIZATIONS OF SPENT NUCLEAR FUEL
Historically, for purposes of reprocessing and recovery, DOE SNFs have been grouped by enrichment level and by cladding and construction. Enrichment levels vary for the different fuel forms (construction), nominally classified as oxide, aluminum alloy, metal or metal non-aluminum alloy, carbide, hydride, naval, or other. Cladding can be described in terms of four main subgroups: zirconium or Zircaloy, stainless steel, aluminum, and graphite.
In the Spent Fuel Background Report3 from INEL, SNF is broadly classified into three categories: (1) production fuels, (2) special fuels, and (3) naval fuels.
Production Fuels Most of the production fuels are located at DOE's Hanford Reservation and include the N-reactor and single pass reactor (SPR) fuels, with the N-reactor fuels alone accounting for about 80% of the total DOE fuel inventory. N-reactor fuel elements consist of two concentric tubes made of uranium metal coextruded into Zircaloy cladding. Two basic types of N-reactor fuel are differentiated by their uranium enrichment. In one type (Mark IV), the pre-irradiation enrichment levels in both tubes is about 0.95% U-235; in the other type (Mark IA), pre-irradiation enrichment levels are about 0.95% and 1.25% U-235 in the inner and outer tubes, respectively. Approximately 70% (by MTHM) of the fuel currently in storage is Mark IV, the remainder being Mark IA.
Special Fuels The category of special fuels includes both low- and high-enrichment fuels from a variety of reactors used in a wide range of research, development, and testing activities. Fuel materials include uranium oxides, metal alloys, mixed oxides, metals, carbides, and others. Cladding materials include zirconium, aluminum, and stainless steel. Fuel forms vary among bundled or individual rods, pieces of rods, plates, carbide pellets in graphite blocks, solidified salts, and even core debris from the Three Mile Island (TMI) reactor.
The largest contributors to the DOE inventory of special fuels include TMI core debris (83 MTHM), pressurized water reactor (PWR) fuel assemblies from Virginia Power and Electric and Nevada Power Corporation's Engine Maintenance Assembly and Disassembly commercial plants (38 MTHM), Fermi-1 blanket fuels (34 MTHM), and graphite fuel (24 MTHM) from the Fort St. Vrain reactor.