FURTHER EXPERIMENTAL-VERIFICATION OF WARM PRESTRESSING EFFECT UNDER PRESSURIZED THERMAL-SHOCK (PTS)

Fracture tests for the verification of WPS (warm prestressing) effect were carried out by using large flat specimens with very low toughness . Tensile and bending loads and thermal shock were applied simultaneou sly to the specimens with the realistically postulated flaw and the tw o times larger one in order to make the maximum K-I cross the lower bo und of K-IC data. During the tests, loading was controlled to simulate the shape of K-I versus temperature curve for the postulated PTS tran sient Both the specimens did not break within the scatter band of K-IC when K-I was decreasing during cooling. K-I values at fracture by rel oading were beyond the upper bound of K-IC. That is, the effectiveness of WPS was directly demonstrated for the PTS transients. Also, K-I va lues at fracture can be predicted by Chell's theory. As the test resul ts, Japanese PWRs have sufficient temperature margin against PTS.