The Consideration of Irradiation Embrittlement of RPV Steels in German Licensing Rules as Compared to Recent Results of Irradiation Experiments

After a brief outline of the consideration of irradiation embrittlement of RPV steels (e.g. 22NiMoCr3 7, 20MnMoNi5 5) in the pertinent German KTA licensing rules, the prerequisites of the licensing procedure are identified and addressed in the light of recent results, mainly from the research program Safety of Components. It is stated that the T sub 41J shift can be determined reliably and reproducibly and that measured shifts are conservatively predicted by the trend lines of KTA 3203. It is further shown that the T sub 41J shift is generally greater than the T sub NDT shift and that the measured reference temperature RT sub NDT in the irradiated state compares reasonably well with the adjusted reference temperature RT sub NDTj . Experimental K sub Ic /K sub Jc values for two steels, unirradiated and irradiated, have been found to scatter largely but lie always far left from the corresponding lower bound K sub Ic curves. Preliminary results and ongoing research programmes are briefly discussed with respect to the influence of neutron energy spectrum and flux density on embrittlement. Graphs. 12 ref.--AA