Study On Fracture Toughness Of Nuclear Reactor Pressure Vessel Steels And Corresponding Structure

To study the fracture toughness of nuclear reactor pressure vessel(RPV)steels which include Chinese A508-3 steel,tensile and fracture toughness test of Chinese A508-3 steel at low temperature were carried out in this paper.Based on the test results,Master Curve method in ASTM 1921 standard was adopted to obtain the reference temperature T0 of Chinese A508-3 steel,and predict its fracture toughness curve in the ductile-brritle region.Taking the particularity of RPV steels into account,correlations between Charpy impact energy and fracture toughness were also studied.Fracture toughness of RPV steels were predicted from Charpy impact energy using empirical formulas and Master Curve method respectively.Besides,Considering the constraint effect,J-A2 method was incorporated into Master Curve method to predict the fracture toughness of structures better.The results reveal that the several T0 values of Chinese A508-3 steel are close to each other,no matter Charpy size or 0.5 Charpy size three points bending specimens are used for test and no matter singular temperature method or multi-temperature method is used for calculating T0.Thus,the average of above T0 values Tave is used as the final reference temperature.Based on Tave,the fracture toughness curve of Chinese A508-3 steel in the ductile-brritle region is generated and shows excellent aggrement with test data,indicating the effectiveness of Master Curve method in characterizing the fracture toughness of Chinese A508-3 steel.When predicting fracture toughness of RPV steels in the ductile-brritle region from Charpy impact energy,Master Curve method shows superiority than empirical formulas.The reference temperature T0 of Master Curve method can be predicted through its correlations with T28 J,T41J,IGC parameters(IGC1 and IGC2),and can be also predicted through the combination of empirical formulas and multi-temperature method.The Master Curve method can't be used for predicting fracture toughness in the upper shelf region,but with suitable empirical formulas,the predicted fracture toughness are consistent with test data.The combination of empirical formulas and Master Curve method indicate the feasibility of predicting fracture toughness from Charpy impact energy.If other conditions are identical,larger ratio of crack depth to width means higher constraint and corresponds to lower fracture toughness of structures.Through thecombination of J-A2 method and Master Curve method,the reference temperature T0 of nonstandard structures can be predicted from standard fracture toughness test result,consequently predicting their fracture toughness curve in the ductile-brritle region.