Delayed hydride cracking assessment of PWR spent fuel during dry storage

One of the possible degradation mechanisms of PWR spent fuel cladding is delayed hydride cracking (DHC), which can activate within a relatively low temperature range. Due to the high crack growth rate, it is essential to prevent DHC crack growth, but most of the existing DHC studies have focused on the crack growth rate. In this regard, the values and characteristics of the threshold stress intensity factor (SIF) for PWR Zircaloy-4 cladding were described as assessment criteria of DHC. Based on the limited existing test results and analyses, threshold SIF and applied SIF were evaluated. In addition, the possibilities of degradation by DHC were discussed during long-term dry storage. From the analysis with conservative approaches, DHC does not largely contribute to cladding failure. For a more reliable analysis, additional information on spent fuel is needed.