13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Numerical Simulation Method of radiation damage effects in plate-type dispersion nuclear fuel elements Yunmei Zhao, Shurong Ding*, Xin Gong, Yongzhong Huo Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433, China * Corresponding author: dsr1971@163.com Abstract A metal-matrix dispersion nuclear fuel plate is composed of dispersion nuclear fuel meat and metal cladding. The fuel meat is similar to a kind of particle composite with the fuel particles embedded in the metal matrix. The extremely harsh irradiation environment results in the complex thermo-mechanical coupling behaviors occurring in the dispersion fuel plate. Especially, this complexity stems more from the irradiation damage effects, such as irradiation hardening and creep in the metal materials induced by the high-energy fission fragments and neutrons, and the thermal conductivity degradation of fuel particles as well. In this study, for heterogeneous irradiation conditions, the three-dimensional large deformation constitutive relations and stress update algorithms are built and validated for the homogenized fuel meat and cladding in the co-rotational coordinate system through forming subroutines in ABAQUS. The obtained results for the whole fuel plate indicate that when the non-homogeneous irradiation condition introduced: (1) both the mechanical and temperature fields show remarkable non-uniform characters along the length direction; (2) the deformation of the plate surface tends to be an arch, which could affect the normal flow of coolant with increasing burnup. The developed numerical simulation method provides a convenient way to simulate the heterogeneous irradiation damage. This study can lay a basis for establishing failure criteria for metal materials in the irradiation environment. Keywords radiation damage, stress update algorithm, non-homogeneous irradiation condition, thermo-mechanical coupling 1. Introduction Dispersion nuclear fuel elements are composed of metal cladding and fuel meat [1] with a certain volume fraction of fuel particles embedded in the matrix. Compared to the presently used nuclear fuel elements in nuclear plants, they have much better thermal conductivity and thus can reach higher burnup. They have a promising usage in the advanced nuclear reactors and disposal of nuclear wastes. The thermo-mechanical behaviors evolution of nuclear fuel elements and assembly is one of the mostly concerned issues for their in-pile safety, and it is a critical issue in their optimal design as well. Recent researches on thermo-mechanical behaviors in dispersion fuel elements with the finite element method (FEM) have been becoming a development trend, and the numerical simulation method is expected to be an important way for their optimal design. Some finite element method codes, such as FASTDART [2-3], PLATE [4-5], MAIA [6-7] and DART-TM [8], were developed with the attempt to study their thermal and thermal-mechanical behaviors. Van Duyn’s study [9] treated the rod-like dispersion fuel pellet as a composite and established a three-dimensional model with the mutual interaction between the particles and matrix considered. Shurong Ding [10-11]studied the thermal and mechanical behaviors and Qiming Wang [12] studied the interfacial behaviors of the plate-type dispersion nuclear fuel elements based on the Representative Volume Element (RVE) method. In the demanding environment of nuclear reactors,
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