Anodic Dissolution of UO2 Pellet Containing Simulated Fission Products in Ammonium Carbonate Solution

We have proposed it reprocessing process based on the dissolution of spent fuels in aqueous carbonate solution. In order to develop such a reprocessing process, anodic dissolution experiments were carried out by using a simulated spent fuel pellet in (NH4)(2)CO3 Solution. The dissolution rate constant of the simulated fuel pellet at 323 K was estimated as 3.1 x 10(-6) mol(.)com(-2.)min(-1), which is comparable to that in 5 mol(.)dm(-3) HNO3 solution containing 0.01 mol(.)dm(-3) HNO2 at 323 K. The dissolution rate and the current efficiency for file dissolution of simulated fuel pellet in (NH4)(2)CO3 solution were found to decrease with the elapse of time. Furthermore, in order to examine dissolution behavior, the surface conditions of the pellet before and after the dissolution experiments were analyzed with the scanning electron microscopy and the energy dispersive X-ray spectroscopy. It was found that neat UO2 matrix exists on the dissolved surface and a decrease in the dissolution rate and the efficiency is caused by the increase in such surface area on the pellet. During the dissolution experiments, precipitates of the simulated fission products were observed on the pellet and in (NH4)(2)CO3 solution used as the electolytic solution. Analyses of the electrolytic solution revealed that most of the simulated fission products, i.e. alkaline earth and rare earth elements, are precipitated in high ratios. From these results it is expected that the anodic dissolution of spent fuels and the separation of fission products by precipitation can be performed simultaneously.