Environmental Effects on PWSCC Initiation and Propagation in Alloy 600

New stress corrosion studies are presented from initiation tests and crack growth measurements on Alloy 600 in primary PWR environment. The effects of hydrogen, lithium and boron have been studied. Initiation tests have been performed at a high hydrogen content of 70 cc/kg. A longer initiation time was measured compared to intermediate levels but shorter than for low hydrogen concentration of 5 ml/kg. Initiation tests at a Li content of 6 ppm have also been performed. The time to initiation was longer than for 3.5 ppm and about the same as for 2.2 ppm. In addition crack growth measurements using different Li/B contents to simulate a reactor cycle and study any variations with the different composition has been performed. The results show a weak influence of the primary environment. A correlation with the boron concentration was noticed and for high boron contents also a weak dependence on the lithium concentration. The results show that the beginning of cycle conditions usually used for PWSCC studies creates conservative crack growth rates.
QC 20210518