Irradiation swelling, creep and thermal fatigue behaviors of LMFBR pressure vessels

Abstract

The behaviors of irradiation swelling, irradiation creep and thermal-cycling fatigue induced by fast neutron fluence and developed in the LMFBR pressure vessels are analyzed on the basis of experimental data. From the interactions of the irradiation swelling, irradiation creep and thermal-cycling fatigue, the failure criterion for the design and safety surveillance of the pressure vessels can be expressed as a(frbuilt|t/t c) u+b(frbuilt|N/N f) v+c(ϵ/ϵ s) w=1, where t is time, t c is creep rupture time, N is number of cycles, N f is number of cycles to failure, ϵ is strain, ϵ s is swelling strain to failure, and a, b, c, u, v and w are parameters or constants. The tangential tensile strain produced by the irradiation creep, thermal-cycling fatigue and hydrostatic pressure of the liquid sodium coolant may be combined together with the irradiation swelling strain ϵ as a whole. The inter-relationships between the behaviors of irradiation swelling, irradiation creep and thermal-cycling fatigue developed in the LMFBR pressure vessels are discussed.