SUMMARY

Thesis Announcment/Abstract
This work presents a detailed methodology for generating effective material properties of tri-structural isotropic (TRISO) fuel pellets for use in reduced-order homogenized thermal and/or mechanical calculations. This is achieved by use of the finite-element (FE) method to perform simulations of explicitly modeled TRISO fuel pellets, in conjunction with derivation of analytical equations for analogous homogenous pellets which preserve a particular parameter of interest. This method is applied to several properties including thermal conductivity, specific heat capacity, thermal expansion coefficient, Young’s Modulus and Poisson’s Ratio, and the properties generated are a function of temperature and packing fraction. It is demonstrated that the state-of-the-art for homogenizing the thermal conductivity is inadequate for realistic TRISO pellets, while for the other properties no existing standard is found in the literature for homogenizing. Additionally, a multi-physics application of the properties is demonstrated, which involves coupling neutronics with thermo-mechanical calculations. The fission power distribution is obtained from the neutronic analysis, and then the temperature, displacement and stress-strain distributions from the explicit model are compared with those from the homogenous calculations. For the finite-element simulations, the commercial software Abaqus is used, and the Monte Carlo code MCNP is used for the neutronics to obtain the power distributions.