A NEW DEFORMATION MODE OBSERVED IN AUSTENITIC LOW-NICKEL STAINLESS STEELS IRRADIATED TO HIGH NEUTRON EXPOSURE AT 310-432C

摘要

It appears that under some PWR-relevant irradiation conditions low-nickel steels comparable to those used in austenitic internals can develop a new form of deformation when exposures greater than -20 dpa are reached. Whereas current design equations for radiation-induced changes in mechanical properties assume that ductility will decrease initially and then saturate with increasing exposure, it appears that the ductility loss will be reversed at higher exposure for deformation temperatures characteristic of zero-power shut-down conditions. The enhanced ductility is a consequence of radiation-enhanced martensite formation that precludes necking and produces a deformation wave that moves through the steel. Such behavior may make the steel less vulnerable to failure and may extend predicted lifetimes of components of baffle-former assemblies.