SCC INITIATION AND GROWTH IN PWR PRIMARY WATER CONTAINING KOH VS. LIOH

摘要

The cost and availability of Li is creating interest inthe use of KOH to replace LiOH in PWR primary water.These studies evaluated SCC initiation in round tensilespecimens of Alloy 600 with 15% cold forge at constantload, monitored with DC potential drop. Two tests of tenspecimens each were evaluated in 360°C water in twochemistries containing 1500 ppm B with molar equivalentconcentrations of KOH or LiOH to achieve a pH310C of7.0 with 26 cc/kg H2 at 102% of the yield strength. SCCgrowth rate tests were also performed using two 0.5T CTspecimens of Alloy 600 with 15% cold forging (at 18Mpam~(1/2)) and one specimen of Alloy 182 weld metal (25Mpam~(1/2)) in four chemistries: 1500 ppm and 10 ppm B,with either LiOH or KOH to achieve a pH310C =7.0. Afifth chemistry was evaluated at 1000 ppm B, 1 ppm Liand 3.3 ppm K (pH310C = 7.0) to simulate thetransmutation of B to Li during PWR operation.Chemistries were changed during the test (on-the-fly), sothat nothing changed in the test apart from the chemistry.No significant effect of KOH vs. LiOH was observed.