Study on the design limit of the FBR fuel cladding at the anticipated transient event; Evaluation of the thermal transient test results

Seshimo, Ichiro; Ukai, Shigeharu  ; Nomura, Shigeo; Shikakura, Sakae

Fuel cladding integrity must be confirmed even at the anticipated transient event in LMFBR. In case of loss of coolant accident, cladding highest temperature is limited to 830 for Monju design from a view point of preventing the cladding creep rupture failure by increasing internal gas pressure. In this study, using the recent thermal transient test results of modified SUS316 stainless steel, Larson-Miller Parameter Life Fraction method was applied for predicting the optimum failure temperature. With this method, different thermal transient data can be evaluated systematically, and the effect of irradiation on cladding failure temperature was analyzed. Through this analysis, the Monju design limit temperature of 830 for cladding failure can be changed to 966, and alternative limiting temperature of 920 defined for preventing the coolant sodium boiling becomes a critical factor. This results shows the possibility of improvement for the design limit of this event.