Copper and phosphorus effect on residual embrittlement of irradiated model alloys and RPV steels after annealing

The dependence of the recovery of the transition temperature shift after annealing (475 °C, 100 h) on copper and phosphorus contents has been studied on irradiated reactor pressure vessel (RPV) materials. A set of model alloys with low nickel content, lower than 0.2 mass%, was used for the study. Copper and phosphorus contents were varied in a wide range: 0.005–0.99 and 0.002–0.039 mass%, respectively.Recovery efficiency has been estimated by the value of residual embrittlement after annealing, measured in terms of a shift in transition temperature (ΔTKres).A comparison of the results obtained on model alloys with data for VVER-440 RPV materials has also been carried out. Comparative analysis has confirmed the conclusion that ΔTKres is independent of phosphorus content while the effect of copper on ΔTKres is not significant for typical VVER-440 RPV materials with a typical range of Cu contents between 0.10 and 0.24 mass%. However, for model alloys with a wider range of copper content, copper mainly controls the value of ΔTKres.