DEVELOPMENT OF A PRODUCTION-SCALE DISSOLVER FOR NITRIC-ACID DISSOLUTION OF LEU FOILS

ABSTRACT In the LEU-Modified Cintichem process, the first processing step in extracting 99 Mo is dissolving the irradiated uranium foil in nitric acid. A pilot-scale dissolver system, designed at Argonne was used to collect data needed to design a production-scale dissolver capable of dissolving up to 250 g of irradiated LEU and the accompanying fission-recoil barrier. This paper presents the conceptual design for the production scale dissolver as well as the experimental and modeling results that were used for the design. The key information collected to ensure a sound design for the scaled-up dissolver included: the stoichiometry and chemical nature (exothermic, endothermic) of the dissolution reaction, the phenomena that control the rate of the reaction, the chemistry of the dissolver solution during and after dissolution, the chemistry of the off-gas, and the pressure and temperature profiles produced when a specific mass of uranium metal is dissolved in heated nitric acid in a closed vessel.