Nucleation of Voids in Irradiated Stainless Steel

Abstract

AUSTENITIC steels are primary materials for use as fuel cladding and core structural components in high-flux fast breeder reactors. Considerable attention has recently been focused^1,2 on the phenomenon of void formation—three-dimensional clusters of lattice vacancies; the retention of vacancies in the form of such stable secondary defects results in a significant volume expansion of the void-containing material. Reactor core design is complicated by this swelling phenomenon, and it is desirable to eliminate or minimize the effect. The study of void formation in austenitic steels by transmission electron microscopy has previously been limited to studies in the void growth regime. With the availability of high voltage electron microscopes, the very early stages of void formation can be studied by direct observation of specimens while under irradiation in the electron microscope. Using this technique, we have been able to observe the nucleation and growth of voids in AISI Type 316 stainless steel.