The effect of low dose rate irradiation on the swelling of 12% cold-worked 316 stainless steel

In pressurized water reactor (PWR) and fast reactor components, some structural components made of stainless steel are irradiated at temperatures near 400 degreesC. If large amounts of swelling (>10%) occur in these reactor internals, significant swelling related embrittlement may occur. Although fast reactor studies indicate that swelling should be insignificant at around 400 degreesC, the low dose rate conditions experienced by structural components may possibly lead to significant swelling. To address these issues, JNC and ANL have collaborated to analyze swelling in 12% cold-worked 316 stainless steel, irradiated in the EER-II reactor at temperatures ti-om 376-444 degreesC, at dose rates between 4.9x10(-8) and 5.8x10(-7) dpa/s, and to doses of 56 dpa. For these irradiation conditions, the swelling decreases markedly at temperatures less than approximately 386 degreesC, with the extrapolated swelling at 100 dpa being around 3%. For temperatures greater than approximately 386 degreesC, the swelling extrapolated to 100 dpa is around 9%. For a factor of two difference in dose rate, no statistically significant effect of dose rate on swelling was seen. For the range of dose rates analyzed, the swelling measurements do not support significant (>10%) swelling of 316 stainless steel in PWRs.