Recycling Scrap from Un-Irradiated Nuclear Fuel by HNO3 Leaching

Abstract

The work describes the wet chemical route process to recover and recycle a defective un-irradiated uranium dioxide sintered pellets. The optimal conditions of the un-irradiated UO2 sintered pellets dissolution in Nitric acid solutions has been examined. The effects of acid concentration, contact time and temperature on dissolution action have been studied. The samples were exposed to leaching over a range of nitric acid concentrations 2–8 mol/L and temperatures from 20 to 70 °C. The stoichiometry of the dissolution reaction depends on the acidity of the solution. The shrinking core model (product diffusion control model and chemical reaction control model) was used to correlate the experimental results. Kinetics study shows that the chemical reaction model controls the dissolution of UO2 sintered pellets in nitric acid solution. The average value of apparent activation energy estimated from the temperature effect of the chemical reaction was found to be about 101.40 kJ/mol. The optimal conditions to dissolve the UO2 sintered pellets in nitric acid solution have been proposed.