Dissolution flowsheet for high flux isotope reactor fuel at SRS

Abstract

ABSTRACTH-Canyon at Savannah River Site has started dissolving High Flux Isotope Reactor (HFIR) fuel as part of the Spent Nuclear Fuel (SNF) processing campaign. Each HFIR fuel core contains inner and outer fuel elements fabricated from uranium oxide (U3O8) dispersed in a continuous Al phase. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates including the production of H2. The objective of this work was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. The work showed that a full HFIR core could be dissolved using nominally 0.002 M Hg to catalyze the dissolution and the margin between the predicted H2 concentration and the calculated Lower Flammability Limit (LFL) was greater when the dissolving solution was allowed to boil for 45 min prior to initiating the Hg addition.