Simulation Of Effects Of Irradiation Embrittlement On Mechanical Properties Of Nuclear Pressure Vessel Steel And Prediction Of Its Fracture Toughness

With the application of experimental work and theretical analysis, the irradiation embrittlement of the steel for nuclear pressure vessel is studied in this paper. On the one hand, to solove the problem that test materials is hard to obtain, experimental simulation is used to obtain’irradiation steel’; on the other hand, concerning the size effect of surveillance specimens, various methods are attempted to accurately relate the test results of small-scale specimens to those of big-size test pieces. The main conclusions obtained are as follow:(1) To as-received unirradiated material, a procedure which combines the application of cold prestrain together with high temperature heat treatments can be used to simulate the effects of irradiation embrittlement on the mechanical properties. After assessment, the simulated’irradiation steel’amounts to make the as-received steel irradiated by neutron at a dose of φ=3.66x1019n/cm2. In pratical application, various parameters of heat treatment and prestrain can be used to obtain different degrees of’irradiation steel’.(2) Combined with finite element analysis, a new method is proposed to model specimen size effects:energy factor method. It has been found that When energy factor E reaches its critical value Ec at a load, E> Ec, fracture occurs, and Ec is a constant indepentent of geometry and size of test specimen. By calculating Ec, the proposed model can use the fracture toughness test results of small-scale specimens to predict those of standard1T size test pieces. The validity of the present model has been verified. The predicted values Kpred fit well with the experimental results KJC(IT) and the scatter of the predicted and experimental values is comparable. Energy factor method also has been proved effective when applied in ’irradiation steel’.(3) Combined with energy factor method, Master curve can deal with lower constraint specimens. Energy factor method and traditional Master Curve method have their respective advantages and application scope. Comprehensive consideration is needed in pratical application, to choose the better one or to complement each other.