H. Okamura et al., FURTHER EXPERIMENTAL-VERIFICATION OF WARM PRESTRESSING EFFECT UNDER PRESSURIZED THERMAL-SHOCK (PTS), Journal of pressure vessel technology, 118(2), 1996, pp. 174-180
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.