1 INTRODUCTION

Under the sponsorship of the Ministry of Economy, Trade and Industry (METI), Nuclear Power Engineering Corporation (NUPEC) is carrying out irradiation test programs for BWR and PWR fuel assemblies.

The irradiation test program for BWR is "The Verification Test on BWR High Burnup Fuel" to verify fuel integrity and to study fuel behaviors of the lead use assemblies (LUAs) of high burnup 8x8 fuel (BWR Step II Fuel)[1] ^,[2] ^,[10] ^,[11]. The time schedule of the program, which includes the power ramp test on irradiated rods and post irradiation examinations (PIEs), is shown in Figure 1. The LUAs of high burnup 8x8 fuel were irradiated up to 5 cycles in Fukushima Daini Nuclear Power Station No. 2 Unit. Segment rods were installed in LUAs and used for power ramp tests in Japanese Material Test Reactor (JMTR). PIEs of segment rods were carried out at Nippon Nuclear Fuel Development Co., Ltd. (NFD) before and after ramp tests.

Figure 1: Test Schedule of BWR High Burnup Fuel

The irradiation test program for PWR is "The Verification Test on PWR High Burnup Fuel" to verify fuel integrity and to study fuel behaviors of the lead test assemblies (LTAs) of 55 GWd/t fuel (PWR Step II Fuel) [12] ^, [13], [14] ^. The time schedule of the program, which includes the power ramp test on irradiated rods and PIEs, is shown in Figure 2. The LTAs of 55 GWd/t fuel were irradiated up to 4 cycles in...