Development of LBB assessment method for Japanese Sodium Cooled Fast Reactor (JSFR) pipes, 1; Study on the premise for the standardization of assessment procedure

JSFR配管のLBB評価法の開発,1; 評価手法基準化の前提条件に関する検討

若井 隆純 ; 町田 秀夫*; 江沼 康弘*; 浅山 泰 

Wakai, Takashi; Machida, Hideo*; Enuma, Yasuhiro*; Asayama, Tai

This paper describes the premise for the standardization of Leak Before Break (LBB) assessment procedure applicable to Japanese Sodium cooled Fast Reactor (JSFR) pipes made of modified 9Cr-1Mo steel. For the early commercialization of the SFRs, economic competitiveness is one of the most essential requirements. Japan Atomic Energy Agency (JAEA) proposes an attractive plant concept and studies the applicability of some innovative technologies to the plant. One of the most practical means to reduce the construction costs is to diminish the total amount of structural materials. To meet the requirements, modified 9Cr-1Mo steel has attractive characteristics as a main structural material of SFRs, because the steel has both excellent thermal properties and high temperature strength. Employing the steel to the main structural material, remarkable compact plant design can be achieved. Since the ductility and toughness of the steel is relatively inferior to those of conventional austenitic stainless steels, a LBB assessment technique suitable for the pipes made of modified 9Cr-1Mo steel may be required. In addition, since the SFR pipes mainly subjected to displacement controlled thermal loads, it is expected that fast unstable fracture is hard to take place. Taking both material and structural features into account, the premise to establish a precise LBB assessment procedure for SFR pipes must be organized.