Radiation-Induced Segregation and Void Swelling in 304 Stainless Steel

Abstract

Void swelling and radiation-induced segregation have been measured in 304 stainless steel. Samples were irradiated in the outer regions of the EBR-II reactor where displacement rates of 2.0×10-8 and 6.6 ×10-8 dpa/s are comparable to those in pressurized water reactor components. Samples were irradiated at temperatures from 371-390°C to total doses of up to 20 dpa. Void swelling reached a maximum of 2 % at 20 dpa. Nickel enrichment and chromium depletion to of 20 at% and 12 at% respectively were measured. Both void swelling and radiation-induced segregation were dependent on dose rate, increasing as the dose rate decreased. Grain boundary compositions were measured both near and in areas free of precipitates. The presence of a precipitate significantly changes the grain boundary compositions near the precipitate.

Microchemical and microstructural evolution of AISI 304 stainless steel irradiated in EBR-II at PWR-relevant dpa rates

“…Comparable Cr depletion at grain boundaries has been reported in numerous studies of irradiated steels, e.g. [68,76,[78][79][80][81][82].…”

“…the formation and growth of carbide and phosphide particles) and radiation-induced segregation by an inverse Kirkendall mechanism [76,77] can explain the observed grain boundary chemistry. As observed by A llen et al [69][70][71]78], grain boundary precipitation can significantly alter grain boundary composition and the associated radiationinduced segregation profiles. Comparable Cr depletion at grain boundaries has been reported in numerous studies of irradiated steels, e.g.…”

ANL/CRIEPI collaborative program for evaluation of irradiated EBR-II stainless steels.

“…Although displacement rate has been shown to affect swelling in 304 stainless steel [17], displacement rate has not been shown to significantly affect swelling in Type 316 stainless steel [16]. Although differences in displacement rate may contribute to greater than expected swelling, displacement rate is probably less of a contributor than composition.…”