As part of the H-Canyon Waste (HLW) Minimization Plan, H-Canyon Engineering requested that SRNL evaluate the feasibility of using HB-Line (HBL) column waste streams from AFS-2 processing for the dissolver solution for Used Nuclear Fuel (UNF) processing. The targeted UNF for dissolution using recycled solution are fuels similar to the University of Missouri Research Reactor (MURR) fuel. However, a limited number of the fuel bundles were anticipated to contain uranium silicide fuels similar to the Denmark Reactor (DR-3). The experiments initially performed to evaluate the use of AFS-2 column waste solution for UNF dissolutions used Al-1100 alloy coupons. The Al-1100 coupons were considered a representative surrogate (based on the fuel bundle and assembly material) that provided an upper bound on the generation of flammable gas during the dissolution process. Experimental results from this work with Al-1100 alloy challenged current assumptions regarding the potential to exceed 60 % of the H2 lower flammability limit (LFL) in the dissolver off-gas during fuel dissolution. To resolve differences in the previous data that were used for the technical basis, additional experiments were performed as part of an experimental plan to more closely represent the fuels to be dissolved in H-Canyon. This plan included a study of L-Bundle alloy comprised of Al-6061 and U-Al alloys. Guidance for dissolving the remaining Sodium Reactor Experiment (SRE) and DR-3 fuels planned in the Batch 4, 5, and 6 charge plans of the SRE Campaign is provided in this report. Dissolution of the remaining UNF will be addressed in a future report. Flammability calculations are provided for H-Canyon to safely dissolve the fuel assemblies contained in L-Bundles with respect to the H2 levels in the projected peak off-gas rates for SRE and DR-3 fuels.
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