Development of LBB Assessment Method for Japanese Sodium Cooled Fast Reactor (JSFR) Pipes: 2—Crack Opening Displacement Assessment of Thin Wall Pipes Made of Modified 9Cr-1Mo Steel

This paper presents crack opening displacement (COD) evaluation methods used in leak before break (LBB) assessment of sodium piping system in the Japanese sodium cooled fast reactor (JSFR). Thin wall and low work hardening material are features of piping of JSFR. Detectability of coolant sodium is very high, the target leak detection performance of leak detector of JSFR is 100g/hr. Internal pressure of JSFR piping is very low, and large through wall crack is allowable to satisfy LBB condition. The existing COD evaluation method cannot be applied to the piping of JSFR which has above-mentioned features. Finite element analysis (FEA) were performed to evaluate COD for thin wall and low work hardening material piping with a circumferential through wall crack. These analytical results were arranged into engineering evaluation formulae. Proposed method gives high accuracy COD estimation, and is applicable to LBB assessment of JSFR piping.