Trends of long-term storage management technology of spent fuel

Many countries choose dry storage as a spent fuel management method. In the U.S., Germany, etc., where storage period is expected to prolong, the structural integrity evaluation technology for the constituent materials of spent fuel and storage containers is being developed. In the U.S., priorities and tasks are extracted based on gap analysis, and necessary research and countermeasures are being implemented, which steadily leads to resolution. Regarding the evaluation of the soundness of fuel cladding tubes at the time of dry storage, the reorientation of hydride is focused, and the test-based data using high burnup fuel is being obtained. In addition, preliminary storage at the North Anna nuclear plant storage facility has been started. As for the stress corrosion cracking evaluation of canisters, measurement is carried out not only in the basic research at laboratory but also at the existing storage facilities. Establishment of evaluation method based on the accumulation of these data is in progress. The Central Research Institute of Electric Power Industry, which focuses on a countermeasure technology for the stress corrosion cracking of canisters, is developing a technique for relieving welding residual stress and a technique for measuring attached salt using laser. Dry storage technology has different designs in containers, but there are many common integrity evaluation techniques, so it is necessary to continue to improve safety and reliability while acquiring overseas information in the future. (A.O.)