Comparative irradiation study of reactor pressure-vessel steel weld metals

Charpy-V specimens of several test welds made of MnMo, MnCrMo, MnNiMo and MnNiCrMo types were irradiated simultaneously in two series at 3150C and 2850C, respectively, with neutron fluences between 8 x 1018 and 5 x 1019 n/cm2 (E > 1 MeV). The known influence of copper on the 41 J temperature shift (ΔT41) was clearly detected for variations from 0.08 to about 0.3%. A considerable variation in embrittlement of low copper (below 0.08%) welds was not traceable to copper or phosphorus. Obviously it is related to variations of the nickel content (up to 1.7%). The effects of copper and nickel seem to be independent on each other. Both, however, have an influence on the slope of the ΔT41 against fluence curves. The effects of other elements as silicon, phosphorus, arsenic, manganese, chromium, molybdenum and of welding procedure and welding flux are discussed in the paper. Due to overlapping, these effects could not be clearly defined. The Charpy-V upper shelf energy drop shows an effect equivalent to overaging. The shelf drop recovers by further irradiation in the region of 1 to 4 x 1019 n/cm2 for all low copper weld metals except that with 1.7% nickel. The shelf drop sequence of the materials tested is in general similar to ΔT41 sequence with some differences in detail