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Evaluation of Codisposal Viability for Aluminum-Clad DOE-Owned Spent Fuel: Phase I Intact Codisposal Canister

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BBA000000-01717-5705-00011_MOL.19971111.0726.pdf (1.3 MB) 1.3 MB

This evaluation is prepared by the Mined Geologic Disposal System (MGDS) Waste Package Development Department (WPDD) to provide analyses of disposal of aluminum (AI)-based Department of Energy-owned research reactor spent nuclear fuel (DOE-SNF) in a codisposal waste package with five canisters of high-level waste (HLW). The analysis was performed in sufficient detail to establish the technical viability of the Al-based DOE-SNF codisposal canister option. The objective is to analyze the disposal characteristics of the codisposal canister with regards to criticality safety, structural strength, thermal limits, and effect on the waste package surface dose rates.
Two DOE-SNF fuel types were designated by Savannah River Site (SRS) personnel (Ref. 8.3) to represent near-bounding conditions for the wide variations found in Al-based research reactor fuels: the high-enrichment Massachusetts Institute of Technology (MIT) reactor fuel and the medium- enrichment Oak Ridge Research (ORR) reactor fuel. The MIT fuel has an initial maximum enrichment of 93.5 weight percent U-235 and the ORR fuel has an initial maximum enrichment of 20.56 weight percent U-235. Criticality calculations were performed for intact fuel contained within the codisposal canister for fully flooded conditions as typically assumed as worst case for both transport and disposal. Thermal, structural and shielding analyses were also performed for intact fuel contained within the codisposal canister for repository conditions. Also, sufficient criticality analyses of the potential degraded states of MIT and ORR fuel within an intact codisposal canister basket were performed in order to establish the quantity of stainless steel/boron alloy needed to insure subcriticality if the fuel degrades within an intact basket. The further degradation of the codisposal canister wall, which would allow fuel material to migrate outside the codisposal canister, will be addressed in Phase II.

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