IRRADIATION EMBRITTLEMENT MECHANISMS AND RELEVANT INFLUENCE FACTORS OF NUCLEAR REACTOR PRESSURE VESSEL STEELS

Abstract

Nuclear reactor pressure vessel is the irreplaceable component of the nuclear power plant and its integrity is one of the key issues of any nuclear power plant for long term operations. Various nanofeatures, includ- ing solute clusters, matrix damage and grain boundary segregation formed in reactor pressure vessel steels in the face of neutron irradiation. These ultrafine microstructural features lead to an increase in the ductile brittle transi- tion temperature as is the measure used to describe the irradiation embrittlement. The balance of features depends on the composition of the reactor pressure vessel steels and the irradiation conditions. This paper reviews the cur- rent phenomenological knowledge and understanding of the basic mechanisms and relevant influence factors for ir- radiation embrittlement of nuclear reactor pressure vessel steels. To be specific, the formation and evolution pro- cesses of the embrittling features are presented. Also, the influences of material variables, such as copper, nickel and manganese contents on irradiation embrittlement and those of irradiation variables, such as neutron flux and post irradiation annealing are summarized. In addition, fundamental research issues that remain to be addressed are briefly pointed out.