316 stainless steel cavity swelling in a PWR

Swelling was measured on a cold-worked (CW) 316 stainless steel (SS) flux-thimble tube irradiated in a Pressurized Water Reactor (PWR) plant. The measured swelling was approximately 0.03% (in the range of 0.01 to 0.09%). The sample was irradiated at a temperature between 305 and 315 C to a calculated dose of about 35 dpa. Comparison with High Flux Isotope Reactor (HFIR) swelling data suggests that the observed cavity swelling is due to helium bubbles. The PWR datum was extrapolated to the approximate end-of-life reactor internals component dose of 100 dpa using HFIR swelling data. HFIR CW 316 SS swelling data indicate that swelling will be less than 3% at 100 dpa in the temperature range between 300 C and 440 C. Garner [1,2] has proposed that large amounts of swelling (>10%) and severe swelling-embrittlement could possibly occur in PWR reactor internals during post shutdown handling. Since the PWR and HFIR end-of-life extrapolated swelling values are probably less than 3%, the proposed swelling and swelling-embrittlement is not considered to apply to PWR reactor internals fabricated with CW 316 SS and operating at temperatures between 300 C and 440 C. (orig.)