Simulation of the coupling behaviors of particle and matrix irradiation swelling and cladding irradiation growth of plate-type dispersion nuclear fuel elements

Abstract

Within plate-type dispersion nuclear fuel elements, besides irradiation swelling of fuel particles induced by nuclear fissions, the metal matrix and the cladding are attacked continuously by the fast neutrons released from the fuel particles. As a consequence, the matrix undergoes a bit irradiation swelling and the cladding takes on irradiation growth, which both might have remarkable effects upon the mechanical behaviors within fuel elements. In this paper, the three-dimensional large-strain constitutive relations for the fuel particles, the metal matrix and cladding are developed; based on them, the method of virtual temperature increase proposed by Ding et al. (2008) is further developed to model the irradiation swelling; the method of anisotropic thermal expansion is introduced to model irradiation growth of the cladding; and a method of multi-temperature-loadstep is proposed to simulate the coupling features of the irradiation swellings of both the metal matrix and the fuel particles together with the irradiation growth of the cladding. In order to clarify the critical factors that affect their mechanical performances and carry out optimal design, with the aid of the research thoughts of particle-reinforced composites, numerical simulations of the irradiation-induced mechanical behaviors are implemented with the finite element method in consideration of the micro-structure of the fuel meat. The obtained results indicate the effects of irradiation swelling of the matrix and irradiation growth of the cladding as that: (1) they might weaken the in-pile mechanical performances at the matrix to some extent; and (2) the former increases interfacial stresses between the fuel meat and the cladding, while the latter relatively relieve those interfacial stresses; and the interfacial mechanical strength might be improved by getting suitable irradiation growth mode of the cladding.