Irradiation embrittlement of model alloys and commercial steels: analysis of similitude behaviors

Abstract

The deep understanding of the irradiation embrittlement of the pressure vessel of nuclear reactors is a key issue for the plant lifetime assessment and life extension through mitigation methods like annealing and much effort have been done in the last decades to tackle such complex issue. The reactor pressure vessel (RPV) material of nuclear power plants is exposed to neutron irradiation during its operation. Such exposure is generally inducing a degradation of the mechanical and physical properties of the materials, e.g. an increase of the ductile to brittle, DBT, transition temperature and a decrease of the upper shelf energy. The different response of materials to neutron irradiation, even many factors are also playing significant role, is mainly due, for a given exposure, to the chemical composition of the materials. In particular, for the RPV steel, elements like phosphorus, P, copper, Cu, and nickel, Ni, are playing a key role. A parametric study of the response to neutron irradiation of 32 different model alloys with parametric variation of elements (Ni from 0.004 to ∼2 wt%, P from 0.001 to 0.039 wt%, Cu from 0.005 to ∼1 wt%) has been recently completed within the frame of the European Network AMES and EC-JRC AMES Institutional project [1]. Such study on model alloys reveals to be a fundamental tool to understand the individual role of each element and synergisms. To demonstrate the usefulness of the study to commercial RPV steels, an analysis of the results and the similitude of behavior between model alloys and available RPV commercial steels has been carried out and the results are presented in this paper.