Probabilistic safety assessment on the experimental fast reactor Joyo, 4-1; Identification of the most important accident sequence on risk assessment of Joyo

Yamamoto, Masaya; Kawahara, Hirotaka ; Terakado, Tsuguo ; Maeda, Shigetaka   ; Saito, Hiroto; Aoyama, Takafumi 

Frequency of ATWS (Anticipated Transient Without Scram) and PLOHS(Protected Loss of Heat Sink) are relatively high in Joyo. To identificate the most important accident and to select the subject of Joyo's level 2 PSA (Probabilistic Safety Assessment), frequency of these accidents were estimated through dynamics characteristic analysis and natural circulation analysis with detailed success standard. Moreover, consequence of these accidents were also evaluated. As a results of these evaluation, the most important accident is identified as UTOP and this accident is selected to the subject of Joyo's level 2 PSA.