THE BEHAVIOR OF CONTENTS OF A SPENT FUEL PACKAGE DURING A 9M VERTICAL DROP TEST WITH LID SIDE DOWNWARDS

Regarding a safety evaluation of a spent fuel package, it was reported that several times of acceleration occurs to the contents compared to the body during the 9 m drop test. This phenomenon creates a safety concern about leaktightness. The greater acceleration is seemed to be produced by the delayed impact of the contents. The delayed impact of the contents is seemed to occur due to a gap between the contents and the inner surface of the lid that is created during the 9 m drop test. In this research, the behaviour of the contents during a 9 m free fall was clarified using EFM analysis that is simulated the 9 m vertical drop test with lid side downwards. Moreover, the 9 m drop analysis was performed to confirm the influence on a package when the gap existed. In this analysis, two types of models were used, the difference between them lies in how the contents are represented, in one the contents are modelled as one body whereas in the other it's divided into the basket and the simplified fuel assemblies. From the results of the analysis, it was confirmed that the greater the gap caused the greater influence on a package. However, we found the maximum gap height is not the only condition that could happen according to the analysis of the behavior of the contents during a 9 m free fall. Moreover, we concluded that a more realistic behavior of the package would be evaluated when the contents are modelled individually compared to the case that the contents are represented as one body