Study on factors important to structural integrity of reactor pressure vessel during PTS with regard to fracture probability

Onizawa, Kunio ; Matsuzawa, Hiroshi*

The structural integrity of RPV during PTS is assessed by considering important factors related to fracture mechanics analysis such as fracture toughness, PTS transient, and irradiation embrittlement prediction and so on. The effects of such factors have been evaluated with regard to the fracture probability of RPV using probabilistic fracture mechanics (PFM) analysis code PASCAL2. Results from sensitivity analyses on the factors showed that the effect of fracture toughness curve is significant when the curve shape is different at high temperature range. Revised embrittlement correlation method gave slightly lower probability of fracture. The heat transfer coefficient for PTS transient and welding residual stress due to overlay cladding showed some effects to increase the probability of fracture. Uncertainties related to the RTNDT shift with regard to the probabilistic variables such as chemical composition and neutron fluence are compared with the deterministic result with a margin.