In Germany there are two first generation commercial nuclear power plants in operation, Obrigheim NPP (KWO) and Stade NPP (KKS). The reactor pressure vessels of both plants were fabricated of forged rings, joined with submerged arc welds. These welds were performed with a flux of the first generation, produced in license of Linde, and with copper-coated wires. When the first results of the irradiation surveillance programs were available, it became obvious that the neutron-induced embrittlement of the welding materials would be higher than expected at design of the power stations in the late sixties.
To evaluate the neutron irradiation response, additional irradiation programs were performed. In the scope of these programs, submerged arc test welds were produced, corresponding in chemical composition, mechanical properties and Charpy toughness in the unirradiated condition of the core-welds of the two NPPs concerned. It was intended to assess also KIc, T-curves of the welding material established on fracture toughness tests of large specimens.
This report presents some results of unirradiated and irradiated tensile, Cv, KIc specimens and E208 drop weight specimens according to ASTM E208 taken from submerged arc welds with different copper content up to 0.42 wt.%. Irradiation was performed in the RPVs concerned and in the VAK RPV with different fluxes and fluences up to about 3.3E19 cm-2 (E > 1MeV).
The irradiation behavior of the welding material in general is shown, especially the influence of the copper content. At a copper content of about 0.30 wt. %. saturation in in the T41 shift was found. The results show no influence of the irradiation facilities and of the different fluxes. With results on irradiated Cv, E208 drop weight, and WOLX specimens the conservatism of the use of the T41 shift according to the RTNDT concept could be confirmed.