Delayed hydride cracking velocity of Zr-1Nb-1.4Sn-0.3Fe pressure tube with different environmental conditions

Delayed hydride cracking velocity of a Zr-1Nb-1.4Sn-0.3Fe tube was evaluated in air and pressurized water to investigate the effect of the environmental conditions on the DHC characteristics. Compact tension specimens charged electrolytically with 29 to 60 ppm H were subjected to DHC tests at temperature ranging from 144 to 250 .deg. C. DHC velocity increased with increasing temperature but was slightly higher in pressurized water conditions than air. This environmental effect on DHCV of the Zr-1Nb-1.4Sn-0.3Fe tube appeared striking at low temperature but disappeared at the temperature as high as 250 .deg. C. A discussion was made on the effect of the environmental conditions on DHCV of the Zr-1Nb-1.4Sn-0.3Fe tube. For the 001 sake of the safety of pressure tubes operating in reactors, DHCV velocity obtained in pressurized water seems more valid than that in air