SCK·CEN contribution to the IAEA Round Robin exercise on WWER-440 RPV weld material: Irradiation, annealing and re-embrittlement

In the frame of an IAEA Round-Robin exercise, SCK·CEN has extensively characterized the mechanical properties of the WWER-440 weld material in the following four conditions: • baseline (unirradiated); • irradiated in the BR2 reactor up to an average fast neutron fluence of 6.5 × 10¹⁹ n/cm²; • irradiated and eventually annealed for 100 h at 475 °C; • irradiated, annealed and finally re-irradiated in the BR2 reactor up to a cumulated fast fluence of 1.3 × 10²⁰ n/cm². The experimental activity consisted, for each condition examined, in tensile tests, instrumented impact tests on standard and sub-size Charpy-V specimens and fracture toughness tests on pre-cracked Charpy-V specimens. The effects of irradiation, annealing and re-irradiation on the mechanical properties of the VVER-440 RPV weld have been considered and analysed. Additional items addressed are: • the relationship between full-size and sub-size Charpy-V specimens for this material; • the assessment of radiation embrittlement, annealing recovery and re-irradiation embrittlement measured in terms of impact and fracture toughness properties.