FAILURE PROPENSITIES OF PRESSURIZED ZIRCALOY TUBE CONTAINING IODINE AND OTHER CHEMICAL-SPECIES

Failure propensities of Zircaloy-4 cladding tube internally pressurize d with Ar gas containing iodine and iodine plus each of other chemical species were examined at 360-degrees-C, to study the effect of corros ive fission products (FPs) on the integrity of spent nuclear fuel rods during dry storage, and also to assess the capability of preventing t he spent fuel rod degradation. The iodine stress corrosion cracking (S CC) of Zircaloy tube occurred in the long time/low stress exposure tes ts at stresses much lower than the conventional ''threshold stress'', with considerably large strains at failure. The addition of cesium to iodine perfectly suppressed the SCC. It is inferred from these results that the degradation of spent fuel rods induced by corrosive fission products is unlikely during dry storage. Even if iodine alone should t ake effect, a proper strain limit could prevent spent fuel rods from i ncurring iodine induced effects because of considerably large strains necessary for iodine SCC of Zircaloy tube at low stresses.