Behavior of fission products zirconium and barium in fast reactor fuel irradiated to high burnup

Barium and Zr generated in nuclear fuels can precipitate as multi-component oxide with some other fission products. In addition, the solubility of Ba in the fuel depends on the oxygen potential and the temperature and Zr can easily dissolve into the fuel matrix. Therefore, the behavior of the Ba-Zr oxide inclusions during irradiation is rather complex. In this work, the composition of multi-component oxides and the distributions of Ba and Zr as a function of relative radius were evaluated with X-ray microanalysis. As results, the oxide inclusions containing both Ba and Zr and containing only Ba were observed in the fuel irradiated to the burnup of 13.3 and 10.6at%, respectively. These results were discussed in terms of the solubility of Ba and Zr in the fuel and in terms of the ZrO2-UO2 phase diagram, together with the radial distributions of Ba and Zr in fuel matrix. (author)