Verification of Warm Prestressing Effect Under a Pressurized Thermal Shock (PTS) Event

Fracture tests for the verification of WPS (warm prestressing) effect were carried out by using large flat specimens and big compact specimens with low toughness. In the case of monotonical K_I increasing during cooling, the specimen broke within the scatter band of K_IC. On the other hand, when K_I was decreasing during cooling, the specimens did not break even if K_I values were beyond the scatter band of K_IC. That is, WPS effect was confirmed even for the low toughness steel like reactor pressure vessel wall under neutron irradiation. Also, K_I values at fracture can be predicted by Chell’s theory. By applying WPS effect and the predictive equations for irradiation embrittlement for Japanese PWR reactor steels to the PTS integrity analysis, much more temperature margin can be expected.