Containment integrity evaluation of MSF-type cask for interim storage and transport of PWR spent fuel

Many spent fuel storage pools in nuclear plant facilities are now reaching their full capacity in Japan. As a solution of this issue, Mitsubishi Heavy Industries, ltd. (MHI) has developed a high integrity dual purpose cask for interim storage and transport of PWR spent fuel. As for the dual purpose cask, the conformity with the requirements for leak-tightness during transport specified in IAEA Safety Standards (Safety Requirements No. TS-R-1) has to be verified by drop tests and/or numerical simulations. A Full-scale drop test is a valid and feasible way for demonstrating a containment performance because it is difficult to scale down a closure system, especially the dimensions and characteristics of the metallic O-rings attached to the lids, according to the scaling law. Therefore, MHI conducted full-scale drop tests and demonstrated the conformity with the leak-tightness requirements. The closure system of the MSF-21P cask has been designed on the basis of the full-scale drop test results and its containment integrity has been verified by dynamic Finite Element (FE) analyses based on the full-scale drop test results.