Session: 05-02 Fuel Performance Assessment

Paper Number: 65563

Start Time: August 5, 2021, 04:15 PM

65563 - Modeling of Irradiation-Induced Thermo-Mechanical Coupling Behavior in Triso-Zr Fuel 

The application of TRISO-Zr dispersion fuel to advanced light water reactors, small modular reactors and mirco-reactors has attracted increasing attention. TRISO-Zr dispersion fuel element is a typical composite fuel, in which the fuel pellet is enveloped by zircaloy cladding. Fuel pellet consists of tri-structural isotropic(TRISO) fuel particles embedded in zircaloy matrix. To guarantee the safety and obtain the maximal fissile loading, it is necessary to perform in-pile thermo-mechanical behavior in TRISO-Zr fuel.

Under irradiation environments, TRISO-Zr fuel element experiences a complex thermo-mechanical coupling behavior and strong mechanical interaction. The fission heat generated by fuel kernels results from a non-homogeneous temperature profile, resulting in occurrence of thermal stresses. Irradiation-induced swelling of fuel kernel keeps squeezing buffer layer. Buffer layer also shrinks under neutron irradiation. Concurrently, fission gases and other gases are released into buffer layer which results in gas-induced expansion and variation of thermal conductivity. Buffer layer is constrained by anisotropic IPyC. Both PyC layers (IPyC and OPyC) shrink due to irradiation. SiC layer exhibits temperature-dependent irradiation-induced swelling. Also of importance, irradiation-induced creep of each material can affect mechanical interaction among coating layers greatly. Moreover, the in-pile behavior of zircaloy matrix and cladding especially creep effect and irradiation-induced growth can affect particle-to-particle and meat-to-cladding interaction. One can realize that the thermo-mechanical coupling behavior of TRISO-Zr fuel is a complex and multi-scale phenomena.

To date, though a set of mathematical models and simulation methods have been subsequently developed for fully ceramic micro-encapsulated (FCM) fuel rod, yet the in-pile behaviors of TRISO-Zr dispersion fuel is rarely reported. An accurate and comprehensive analysis needs to be conducted involving all the aforementioned mechanical interaction and physical mechanisms for advanced fabrication and optimization of TRISO-Zr dispersion fuel.

In this study, three-dimensional finite element analysis for the thermo-mechanical behavior in TRISO-Zr fuel element is performed with the irradiation effects considered thoroughly. The actual thermal-mechanical boundary conditions in LWRs is adopted. Distribution and evolution of temperature field and stress-strain fields are obtained and analyzed. This study provides a fundamental basis for advanced fabrication and optimization of TRISO-Zr dispersion fuel element.

Presenting Author: Hongyang Wei Nuclear Power Institute of China

Authors:

Hongyang Wei Nuclear Power Institute of China
Fawen Zhu Nuclear Power Institute of China
Jun Ru Nuclear Power Institute of China
Haoyu Wang Nuclear Power Institute of China
Jing Zhang Fudan University
Hua Li Nuclear Power Institute of China
Yun Li Nuclear Power Institute of China
Chunlan Huang Nuclear Power Institute of China
Yuanming Li Nuclear Power Institute of China
Shurong Ding Fudan University