HYDRIDE REORIENTATION TEST FOR SPENT FUEL INTEGRITY

Evaluation of spent fuel integrity for dry storage and transportation situation is getting more important because dry storage is significantly reconsidered for another extension beyond 200 years after Yucca mountain repository project was suspended in US. This very long term storage situation can cause more severe hydrogen related degradation as storage system temperature decreases. Republic of Korea faces the PWR spent fuel pool saturation situation in reactor and dry storage like other countries seems to be most possible temporary solution in near future. Since spent fuels have to be transported to the final solution place after storage, possible spent fuel integrity degradation mechanisms must be thoroughly evaluated. Among them hydride reorientation(HR) has the highest priority deeply related to structural integrity during the transportation. Therefore, HR research has begun with testing system installation in hotcell area in Korea. The purpose of this testing are to follow the previous research works and compare our data with their result range, to suggest an empirical modeling including various parameter like hoop stress, temperature history (cooling time), and hydrogen contents (burnup). Testing methods consist of 5 mm height ring type and 25 cm long tube type. Each method has advantages and disadvantages to analyze HR phenomena. Unirradiated cladding charged with hydrogen and irradiated cladding from spent fuel were used as testing specimen. Since Zircaloy-4 cladding occupies 78% of Korean spent fuel, this cladding is the main target material. ZIRLO, however, was also tested in the ring shape. This paper written at beginning stage of testing does not suggest any analysis opinion, but introduces current research situation and direction about hydride reorientation testing in Korea.