The effects of microstructure on iodine-induced stress corrosion cracking(ISCC) of Zircaloy-4 tube was studied by an internal pressurization test method at temperature 330℃ and at iodine concentration of 2.2 mg/㎠.
The threshold stress was found to be 400 MPa for stress - relieved, 350 MPa for water quenched and for 280 MPa air cooled Zircaloy-4 tube respectively. The following relationship was found between the failure time ( $t_f$ ) and hoop stress ( ${\sigma}_n$ ) at the stress of threshold level :
$t \propto exp(-C{\sigma}_n)$
In the above equation the values of constant C were found as follows
C = 0.046 for stress-relieved Zircaloy-4
C = 0.022 for water quenched Zircaloy-4
C = 0.012 for air cooled Zircaloy-4
It was found that the SCC resistivity exhibit minimum value at a certain strain rate of 1-6×10$sec^{-6}$.
