Irradiation embrittlement assessment and prediction of Armenian NPP reactor pressure vessel steels

• Prediction of irradiation embrittlement of Armenian RPV materials on the basis of surveillance data.
• Selected materials from IAEA International Database on RPV materials were used for analysis.
• Regulatory Guide predicts rather conservative the irradiation embrittlement of RPV steels.

The basic results of the Armenian RPV surveillance program are presented. A change in ΔTk – neutron fluence trend curve shape is observed at a fluence of more than 4 × 1020 cm−2 for both base metal and weld.The prediction of radiation embrittlement of Armenian RPV materials was performed on the basis of surveillance data and information from the IAEA International Database on RPV materials. Because the original weld surveillance data could not be used for the Armenian RPV weld embrittlement assessment, an analysis of selected data from the Database was carried out. Six welds and two base metals of WWER-440 steel with P and Cu contents similar to Armenian welds were selected and their embrittlement results were compared with the Russian Regulatory Guide prediction. It is demonstrated that the Guide corresponding to Af = 24.64 (chemistry factor for Armenian RPV weld No. 4) predicts the irradiation embrittlement of the selected steels conservatively. According to the Guide prediction the Tk for weld No. 4 should not exceeded 145 °C by 2016. It is also demonstrated that the Armenian base metal irradiation embrittlement is substantially less than the Guide prediction.