The effects of low dose rate irradiation and thermal aging on reactor structural alloys

As part of the EBR-II reactor materials surveillance program, test samples of fifteen different alloys were placed into EBR-II in 1965. The surveillan ce (SURV) program was intended to determine property changes in reactor str uctural materials caused by irradiation and thermal aging. In this work, th e effect of low dose rate (approximately 2 x 10-K dpa/s) irradiation at 380 -410 degrees C and lone term thermal aging at 371 degrees C on the properti es of 20% cold worked 304 stainless steel, 420 stainless steel, Inconel X75 0, 304/308 stainless weld material, and 17-4 PPI steel are evaluated. Doses of up to 6.8 dpa and thermal aging to 2994 days did not significantly affe ct the density of these alloys. The strength of 304 SS, X750, 17-4 PH, and 304/308 weld material increased with irradiation. In contrast, the strength of 420 stainless steel decreased with irradiation. Irradiation decreased t he impact energy in both Inconel X750 and 17-4 PII steel. Thermal aging dec reased the impact energy in 17-4 PH steel and increased the impact energy i n Inconel X750. Tensile property comparisons of 304 SURV samples with 304 s amples irradiated in EBR-II at a higher dose rate show that the higher dose rate samples had greater increases in strength and greater losses in ducti lity. (C) 1999 Elsevier Science B.V. All rights reserved.