Void swelling and resultant strains in thick 304 stainless steel components in response to spatial gradients in neutron flux-spectra and irradiation temperature

摘要

In this paper we examine the internal swelling distribution of a set of thick blocks constructed of AISI 304 stainless steel that served in one of the reflector assemblies in the EBR-II fast reactor. A series of both nondestructive and destructive measurements shows that significant internal variations in swelling occur that arise primarily from the higher internal temperatures generated by gamma heating and the thermal resistivity of the thick blocks. Of particular interest are the results generated from ultrasonic time-of-flight measurements that allow measurements and visualization of the internal spatial distribution of swelling. Off-center internal peaks approaching ～4% swelling were found in the center of the block with highest dose, where the average swelling was only ～1.5% over the block cross section. In another block with the lowest dose levels, void swelling was much lower and carbide-induced densification dominated to produce overall negative strains. Varying levels of distortion in individual blocks were observed as a consequence.