Neutron Flux Density Effect on Vessel Steel Embrittlement

Abstract

The effect of the neutron flux density on the embrittlement of the reactor vessel materials is analyzed in an investigation of the impact of neutron irradiation on their properties. The evaluation of the dependence of radiation embrittlement of the vessel steel on the neutron flux density is made to a fi rst approximation for conventional virtual material by averaging the radiation embrittlement coefficient, taking account of the chemical composition, A_F = 800(P + 0.07Cu). The actual radiation embrittlement coefficient was determined experimentally on the basis of the normative dependence ΔT_F = A_F(F·10^–18)^1/3. It was found as a result that the dependence of the radiation embrittlement coefficient of virtual steel on the neutron flux density has the form A_F = 17.8 + 9.5/φ, where φ is the neutron flux density in the units 1011 sec^–1·cm^–2. As the neutron irradiation intensity decreases, embrittlement increases; the highest sensitivity to the neutron flux density is observed in the range (0.1–1)·10¹¹ sec^–1·cm^–2. This dependence makes it possible to evaluate the impact of the intensity of neutron irradiation of vessel steel on embrittlement.