Thermomechanical preloading (warm prestressing) as a promising method for extending the life of WWER-type reactor pressure vessels operating under conditions of radiation

摘要

The purpose of the present work was to study the influence of different regimes of overloading of pressure vessel steels in different states which correspond to the steel properties at the beginning of the reactor operation and at differentdegrees of embrittlement (simulated by thermal treatment). The experiments were performed on 25-,50-, 150 mm-thick specimens with short and long cracks of various shape in the temperature range 293-623 K corresponding to the service temperature range ofthose steels. The following factors were investigated: contribution of different mechanisms (residual stresses, strain hardening, crack tip blunting) into the enhancement of the brittle fracture resistance of steels after warm prestressing; stability ofthe warm prestressing positive effect during subsequent exposure of those steels to different service loading conditions; size effect on optimal regimes of thermomechanical prestressing and on the brittle fracture resistance characteristics of the steelsstudied after warm prestressing. An approach is proposed for the prediction of the increase in the brittle fracture resistance of steels with cracks after warm prestressing.