The influence of testing conditions and irradiation on the stress corrosion cracking susceptibility of zircaloy

Abstract

Variables in the SCC testing technique and the effect of the fast neutron dose appear to explain most of the controversy about the effect of irradiation damage on the SCC behaviour of Zircaloy. The environmental variables in the SCC test have a larger influence on the lifetime for autoclaved material than for pickled and sandblasted metal. The effect is even more pronounced for irradiated and oxidized material as a ten times increase in the iodine concentration reduced the failure stress from 500 to 250 MPa. Small amounts of air in the testing atmosphere tended to increase the stress required to cause SCC in a given time for both unirradiated and irradiated oxidized material. By comparing our results with published data it is concluded that the failure stress (after 1–3 h) is very dependent upon the neutron dose. Neutron damage will raise the stress threshold for doses up to 10 20 n/cm 2, whereafter the failure stress is gradually decreased to low values with increasing neutron doses up to 5 × 10 21 n/cm 2.