Density, porosity and grain size. 1. Unirradiated ROX fuels

Two types of ROX fuels (ROX-SZR and ROX-ThO2) and 9 simulated ROX fuels (PuO2 was replaced by UO2) were prepared. Density, porosity and grain size as experimental parameters of those under unirradiated condition were studied. Obtained results are: The theoretical density (TD) was estimated to be 5.6 g/cc for the ROX-SZR and 6.2 g/cc for the ROX-ThO2, while corresponded as-sintered density was 4.6 g/cc for the former and 5.2 g/cc for the latter, respectively. Densities of the ROX fuels were about half of that in UO2 fuels used in conventional light water reactors. Percent TD of the ROX fuels was relatively low to the magnitude of about 82-83%TD. The porosity was large (17-18%) and grain size was small (2 μm). The theoretical density of the simulated ROX fuels was estimated to be in the range of 5.0-5.7 g/cc, while corresponded as-sintered density was in the range of 4.9-5.4 g/cc, respectively. Densities of the simulated ROX fuels were the same in magnitude to those of the ROX fuels but about half of that in UO2. Percent TD of the simulated ROX fuels was relatively high to the magnitude of about 94-98%TD. The porosity was small (<6%) and grain size was also small (3-4 μm). (author)