Void Formation in Fast-Reactor Materials

Abstract

The dimensional and mechanical stability of fuel-cladding and structural components of fast-reactor systems is of prime concern to the reactor engineer. In 1966 Cawthorne and Fultonl discovered that austenitic stainless-steel fuel-cladding exposed to high doses of fast neutrons developed an internal porosity in the form of small (∼ 100 Å) cavities. Such cavities were shown to be essentially empty and were therefore called ‘voids’(see Fig. 1). Previously recognized problems associated with irradiation in a fast-neutron, environment such as lowtemperature hardening, high-temperature embrittlement, and the acceleration of diffusion-controlled processes-although still far from completely understood-have tended to give rise to less concern as more experimental evidence has been accunlulated. On the other hand the consequences of void formation tend to dominate current assessments of fuel-pin and structural material behaviour in fast reactors.