Upscaled elasticity modulus for nuclear fuel pellet (UO2) with porosity effects

The nuclear fuel pellet is a sintered material with heterogeneous characteristics constituted of the solid (fuel particle) and gas-phase (space between solids). For these fuel pellets, the volume averaging method (VAM) was applied to the equations governing mechanics at the microscale to calculate the upscaled elasticity modulus, which resulted in being a function of the porosity. The systematic application of VAM leads to one equation valid at pellet scales, which includes two effective tensors related to the elastic modulus and one new effective vector ( interfacial elasticity coefficient ) quantifying the deformation for strongly deformed materials. The analysis presented in this work considers the computation of the up scaled coefficients for four microstructure cases: slit, spherical-cup-slit, symmetric and asymmetric configurations with which is feasible to consider the different types of porosity that can occur within UO2 fuel during reactor operation. In addition, a Young's modulus correlation is proposed as a function of porosity and pressure that can be implemented in computational subroutines.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the mechanical properties of nuclear fuel pellets by calculating the upscaled elasticity modulus and new effective vector, allowing for consideration of different types of porosity. The findings are crucial for the design and performance evaluation of nuclear fuel.