Influence of the neutron flux density on the radiation embrittlement of VVér-440/213 vessel materials

In work on minisamples of the fifth complex of the No. 3 unit of the Kola nuclear power plant it is shown that for neutron fluence 410^sup 23^ m^sup -2^ (operation for approximately 10 yr), neutron flux density 310^sup 15^ sec^sup -1^m^sup -2^ and copper content 0.03% and 0.09% in the metal the shifts of the cold-brittleness temperature are 50 and 120°C, respectively. Under the same irradiation conditions but with neutron flux density 310^sup 16^ sec^sup -1^m^sup -2^, this shift for standard samples is 50°C. These results attest to the state of the vessel material at a given moment in time.[PUBLICATION ABSTRACT]