Fuel failure simulation test in the experimental fast reactor JOYO

Ishida, Koichi; Ito, Chikara   ; Aoyama, Takafumi 

When a fuel failure occurs in a nuclear reactor, it is important to detect and identify the failed fuel subassembly to improve reactor safety and reduce radiation exposure and impact on the environment. A Fuel Failure Simulation Test in the experimental fast reactor JOYO was performed to confirm the JOYO plant operation procedures for potential future fuel failure events and help prepare for future planned run-to-cladding-breach tests in JOYO. The test fuel elements with an artificial slit in the fuel cladding was loaded in the core center position of the MK-III core. The test fuel elements were irradiated, the release of fission products was detected, and the location of the leaking test subassembly was identified. The performance of the fuel failure detection system and the failed fuel detection and location systems, and the plant operation procedure of fuel failure were confirmed. To decrease the radioactive concentration in the cover gas, the Cover Gas Clean-up System which collects fission product nuclides by the cryogenic distillation method and furnace-cover-gas-purge were operated, and their operation procedure and performance ware confirmed. This test results will improve the JOYO operation procedures and potential upgrades to the facilities, and be contributed to the safety enhancement of fast breeder reactors.