Development of LBB assessment method for Japan Sodium Cooled Fast Reactor (JSFR) pipes, 5; Crack growth assessment method for pipes made of Mod.9Cr-1Mo steel

Wakai, Takashi ; Machida, Hideo*; Yoshida, Shinji*; Tokiyoshi, Takumi*; Kikuchi, Koichi*; Xu, Y.*; Tsukimori, Kazuyuki

This paper studies the master curve to estimate the crack length when a postulated initial crack unexpectedly grows and penetrates the pipe thickness. In order to obtain the fatigue crack and creep crack growth characteristics of modified 9Cr-1Mo steel pipes, fatigue crack and creep crack growth tests were conducted using compact tension (CT) specimens and crack growth rates for both fatigue and creep at elevated temperature were obtained. Based on the obtained material characteristics and the results of a series of crack growth calculations, a relationship between the penetrated crack length and the ratio of membrane to total stress, so called as master curve, was proposed. In this study, master curves were proposed for pipes made of modified 9Cr-1Mo steel as a function of pipe geometry, i.e. the ratio of radius to thickness.