Optimization of Dissolution Process Parameters for Uranium Ore Concentrate Powders

Abstract

Nuclear fuel complex processes Uranium Ore Concentrate (UOC) for producing uranium dioxide powder required for the fabrication of fuel assemblies for Pressurized Heavy Water Reactor(PHWR)s in India. UOC is dissolved in nitric acid and further purified by solvent extraction process for producing nuclear grade UO₂ powder. Dissolution of UOC in nitric acid involves complex nitric oxide based reactions, since it is in the form of Uranium octa oxide(U₃O₈) or Uranium Dioxide (UO₂). The process kinetics of UOC dissolution is largely influenced by parameters like concentration and flow rate of nitric acid, temperature and air flow rate and found to have effect on recovery of nitric oxide as nitric acid. The plant scale dissolution of 2 MT batch in a single reactor is studied and observed excellent recovery of oxides of nitrogen (NO_x) as nitric acid. The dissolution process is automated by PLC based Supervisory Control And Data Acquisition(SCADA) system for accurate control of process parameters and successfully dissolved around 200 Metric Tons of UOC.

The paper covers complex chemistry involved in UOC dissolution process and also SCADA system. The solid and liquid reactions were studied along with multiple stoichometry of nitrous oxide generated.