高速炉配管のLBB評価におけるスクリーニングルール

Abstract

Since the piping of fast reactor is used at low internal pressure and its material has high ductility, LBB is easily satisfied in general. Especially when the internal pressure is low and thermal expansion reaction force is small, both crack driving force and fracture load are small, then it is easily imagined that LBB might be easily satisfied. However, the crack opening displacement and leak rate dynamically evaluated are small in such conditions. For this reason, the contradiction occurs that LBB evaluation is not satisfied despite the crack driving force and the fracture load are small. To eliminate such inconsistencies, screening rules to determine the necessity of a detailed LBB evaluation were proposed. According to the rules, the detailed LBB evaluation can be omitted for the cases of low internal pressure and small thermal expansion load as the fracture of pipes do not occur. Based on the piping design of the constructed fast reactor plant, the applicability of the proposed screening rules was examined.