抄録
The high-burnup BWR 9×9 lead use fuel assemblies (LUAs), which are designed for a maximum assembly burnup of 55 GWd/t in Japan, have been examined after irradiation in a commercial BWR to confirm the reliability of the current safety evaluation methodology and to accumulate data for judging the adequacy of its application to the future higher burnup fuel. The irradiation performance of 9×9 LUAs for two different designs, types A and B, is generally on the extended trend of 8×8 fuel, but some new findings in terms of fuel performance have been addressed after 5 cycle irradiations. Accelerated corrosion of cladding for the corner rods in Type-B fuel assemblies and spacers in both types is observed after 5 cycle irradiations. The increasing trend of high hydrogen concentration seems to be an issue, which should be paid much attention with respect to fuel integrity during high-burnup irradiation. The large difference in fission gas release rate between two types of fuel is confirmed after 3 and 5 cycle irradiations, and the release rate of Al-Si-O doped pellets is particularly higher than the others.
