Study of system safety evaluation on LTO of National project structural integrity assessment of reactor pressure vessels

Katsumata, Genshichiro; Masaki, Koichi*; Osakabe, Kazuya*; Nishikawa, Hiroyuki*; Katsuyama, Jinya  ; Nishiyama, Yutaka ; Onizawa, Kunio 

To assure the structural integrity of a reactor pressure vessel (RPV) is known as one of the critical issues to maintain the safe long-term operation of a nuclear power plant. In Japan, the assessment methods for RPV integrity, stipulated in the codes and standards, have been endorsed by the regulatory body. Authors have initiated extensive research on the improvement of structural integrity assessment methods of RPVs. In this paper, we describe some research results obtained from the second-year activity. These include the study on revisiting the technical background of the methods, such as loading conditions, postulated crack definition, the other evaluation methods. In addition, studies on probabilistic methods for the applicability to the current rules and the standardization of the probabilistic analysis methods have been presented.