ISSUE OF APPLICATION FOR THE PRE-CRACKED CHARPY SPECIMENS TO ESTIMATE WWER-1000 RPV METAL EMBRITTLEMENT

In this study the analysis of fracture toughness test data has been performed in terms of estimation of the proper To value for several WWER-1000 RPV materials in unirradiated condition. The surveillance test data for the standard and reconstituted specimens were included in the analysis. It was found that a reference temperature To for reconstituted specimens is 31 degrees C higher on average in comparison to the standard specimens. The possible reason is a high level of the stress intensity factor K-max during the cycle at the stage of completion of crack tip sharpening for standard specimens. Furthermore, the Charpy impact and fracture toughness test data for standard and reconstituted specimens have been compared considering the known relationship between the reference temperature To and the transition temperature T28 which corresponds to the Charpy energy level of 28 J. Another objective of this study was to compare the RPV metal embrittlement rate for the two reactor pressure vessels using surveillance test data from standard and reconstituted fracture toughness specimens. The analysis has shown that test data for the reconstituted specimens is consistent with the test data for the standard specimens with regard to the embrittlement rate.