IMPACT BEHAVIOR OF REDUCED-ACTIVATION STEELS IRRADIATED TO 24 DPA

Charpy impact tests were previously conducted on eight chromium-tungst en steels after irradiation at 365 degrees C to 6-8 and 15-17 dpa in t he Fast Flux Test Facility. These same steels, which range in chromium concentration from 2.25 to 12 wt% (all steels contained 0.1%C), have now been irradiated to 20-24 dpa under the same conditions. Post-irrad iation Charpy impact tests after 20-24 dpa showed that the loss of imp act toughness, as measured by an increase in the ductile-brittle trans ition temperature (DBTT) and a decrease in the upper-shelf energy, rem ained relatively unchanged from the values after 15-17 dpa. As before, the most irradiation-resistant steels were two 9% Cr steels: the DBTT of a 9Cr-2W-0.25V steel increased 59 degrees C, and for the same comp osition with an addition of 0.07% Ta, the DBTT increased only 21 degre es C. The other steels developed shifts in DBTT of 100 to 300 degrees C. A 2.25% Cr steel with 2% W and 0.25% V was less severely affected b y irradiation than 2.25% Cr steels with 0.25% V and no tungsten, 2% W and no vanadium, and with 1% W and 0.25% V. Steels with 5 and 12% Cr, 2% W, and 0.25% V had properties between those of the 2.25Cr and 9Cr s teels.