An Example of Evaluation Study on Reliability for Core Shroud Failure in LWR

Abstract

This study presents an approach to a rational integrity evaluation method of rules on fitness-for-service based on the quantitative margin evaluation. So-called twice-slope method is being applied with design margin in fitness-for-service code as one of the limit analyses to evaluate collapse or plastic buckling, to reactor internals such as core shroud even when it has cracks. Monotonic and cyclic loading test using cylindrical test specimens simulating core shroud showed conservatism of conventional design margin. In order to evaluate an appropriate design margin quantitatively, potential factors which may have effect on collapse load were identified and the probabilistic distribution of collapse load caused by the variation of these factors was calculated.