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 specime ns with low toughness. In the case of monotonical K(I) increasing duri ng cooling, the specimen broke within the scatter band of K(IC). On th e other hand, when K(I) was decreasing during cooling, the specimens d id 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 l ike reactor pressure vessel wall under neutron irradiation. Also, K(I) values at fracture can be predicted by Chell's theory. By applying WP S effect and the predictive equations for irradiation embrittlement fo r Japanese PWR reactor steels to the PTS integrity analysis, much more temperature margin can be expected.