Requirements for fracture toughness to satisfy LBB behavior of a pipe made of high chromium steel

The volumetric test for piping of a sodium cooled fast reactor (SFR) is difficult from the poor accessibility. Therefore, detection of a crack in a pipe is difficult until its penetration, and an SFR has a plan to detect sodium leakage from a through wall crack before fracture of a pipe. Plant safety is ensured by detection of sodium leakage in small quantity and by shutting down a plant as soon as possible, even if crack penetrates a pipe wall. Consequently, it is important to ensure establishment of leakage-before-break (LBB) in this plan. High chromium steel (Mod. 9Cr-1Mo steel) is one of the candidates for fast reactor piping material. Effects of a fracture resistance curve (J-R curve) on fracture strength of a cracked pipe made of this material are evaluated in this study, and requirements for a J-R curve to achieve the LBB were proposed. (author)