Stress Corrosion Cracking of Zircaloys in Iodine Containing Environments

Abstract

Iodine solutions in organic solvents fall into two groups. First, those which, like iodine vapor at room temperature, cause crack propagation in double cantilever beam (DCB) specimens but do not initiate cracks in smooth specimens. These are solvents which form no, or only weak complexes with iodine. A second group of solvents (alcohols) both initiate cracking in smooth specimens and cause crack propagation in DCB specimens. These are solvents which form strong complexes with iodine. In addition to these two groups there are a few solvents in which neither crack propagation in DCB specimens nor cracking of smooth specimens occur. Modifications to the chemistry of the system by additives were effective only for arsenite and N2O additions to alcoholic solvents. In both instances times to failure were increased. These results are discussed in terms of the chemistry of the system, and the mechanisms operating during both crack initiation and propagation are considered.