| Abstrakt: |
Theoretical basis of the simplified (engineering) version of Local Approach (LA) to fracture is summarized, and the possibility of using this version to predict the lifetime of RPV steels is demonstrated. The concept of “effective” volume, , within which stresses and strains are uniformly distributed, but the magnitude of the probability of cleavage initiation are equal to their real values at given value of , underlies the proposed engineering version of LA. A function was selected to describe the temperature dependence of local cleavage stress, and a calibration procedure was proposed for determining the constants in this dependence from the results of tests of surveillance specimens. For weld metal of WWER-1000 reactors the dependences of brittle strength on fluence were obtained, and the maximum permissible fluence values were determined. It is shown that in addition to the radiation hardening, the radiation-induced reduction in the level of brittle strength, , has a significant effect on the radiation service life of reactor pressure vessel steel. |
