Evidence for chromium stabilisation of irradiation damage in RPV weld metals

A study using some available high-quality data from German surveillance and research programmes has been carried out in order to provide evidence on the prediction capabilities of a semi-mechanistic model for changes in ductile to brittle transition temperature. The model was developed and tuned originally on model alloys and later proved to be suitable also for WWER and other materials. This study demonstrates that the model can predict very well all the results obtained on low nickel–manganese weld metals and that the corrections required for high nickel–manganese weld metals are consistent with those found for model alloys.An important additional conclusion is that a strong effect of chromium can be identified; weld metals with higher chromium contents show much less sensitivity to radiation embrittlement and a drastic reduction, up to 50%, of the main embrittlement model parameters is required to reproduce the data.