Irradiation and post-annealing reirradiation effects on fracture toughness of RPV steel heat JRQ

A plate of A533 grade B class 1 steel designated heat JRQ has been used for many research studies around the world, especially those sponsored by the International Atomic Energy Agency. In this study, groups of Charpy impact, tensile, and precracked Charpy specimens of the JRQ plate were irradiated by the Paul Scherrer Institute to four different fast neutron fluences [from 0.39 to 5.0 x 10(23) n/m(2) (> 1 MeV)] in a test reactor. Additional specimens were given a post-irradiation thermal annealing treatment at 460 degrees C for 18 h when 50% of the target fluence was reached, followed by reirradiation to the same target fluences for the four groups of irradiated specimens. Additionally, Oak Ridge National Laboratory has thermally annealed some of the reirradiated specimens, as well as some of those in the irradiated only condition. Charpy impact, tensile, fracture toughness, and hardness tests have been performed to evaluate material response in the various conditions and for comparison with the unirradiated material. Except at the highest fluence, the results show that the material given an intermediate annealing treatment exhibited irradiation-induced transition temperature shifts about the same as those that were only irradiated. However, the upper-shelf energies were generally higher and the yield strengths were generally lower for the reirradiated groups. At the highest fluence, the Charpy 41-J temperature shift was significantly lower for the reirradiated group relative to the irradiated group at the same total fluence. The intermediate thermal annealing resulted in less reirradiation embrittlement of fracture toughness than Charpy impact toughness, while annealing after reirradiation resulted in significant increases in Charpy upper-shelf energy above that in the unirradiated condition. Comparisons of Charpy impact and fracture toughness results are mixed relative to transition temperature shifts for irradiated and reirradiated conditions.