Irradiation embrittlement of 2 1/4 Cr - 1 Mo steel at 400 C and its electrochemical evaluation

The effect of neutron irradiation on mechanical properties of normalized and tempered 2 1/4 Cr-1 Mo steel was evaluated by conducting postirradiation tensile and Charpy impact tests. The specimens were irradiated at 400 C to a fluence as high as 3 x 1024 n/m2 (E > 1 MeV). Only slight hardening was observed because of the high temperature of irradiation. However, irradiation at 400 C to a fluence larger than 1 x 1024 n/m2 (E > 1 MeV) caused high Charpy shifts accompanied by intergranular fracture. Results of electrochemical tests indicated that a possible element responsible for intergranular fracture was phosphorus. (orig.)