Generation and Decomposition Behavior of Nitrous Acid During Dissolution of UO₂ Pellets by Nitric Acid

The generation and decomposition behavior of nitrous acid is experimentally investigated during dissolution of unirradiated uranium dioxide (UO₂) pellets by a nitric acid solution. The nitrous acid is generated by the dissolution of UO₂ and it then decomposes to nitrogen oxides through the solution surface. The generation rate is equal to the dissolution rate of the uranium pellet and it depends on the nitric acid concentration, solution temperature, and effective pellet surface area. The decomposition rate depends on the solution surface area and temperature. These findings allow prediction of changes in nitrous acid concentration during and after dissolution.