Demonstration of leak-before-break in Japan Sodium cooled Fast Reactor (JSFR) pipes

Wakai, Takashi ; Machida, Hideo*; Yoshida, Shinji*; Xu, Y.*; Tsukimori, Kazuyuki

This paper describes LBB assessment procedure applicable to JSFR pipes made of modified 9Cr-1Mo steel. Firstly, a LBB assessment flowchart was proposed. Secondly, a rational unstable fracture assessment technique, taking the compliance changing with crack extension into account, was also proposed. Thirdly, a COD assessment technique was developed, because COD assessment method applicable to JSFR pipes - thin wall and small work hardening material - had not been proposed yet. In addition, fracture toughness tests were performed using CT specimens to obtain the fracture toughness and the crack growth resistance curve at elevated temperature. Finally, by using the flowchart, proposed techniques and collected data, LBB assessment for the primary sodium pipes of JSFR was conducted. As a result, LBB aspect was successfully demonstrated with sufficient margins.