Development of a Multiscale Thermal Conductivity Model for Fission Gas in UO₂
Accurately predicting changes in the thermal conductivity of light water reactor UO2 fuel throughout its lifetime in reactor is an essential part of fuel performance modeling. However, typical thermal conductivity models from the literature are empirical. In this work, we begin to develop a mechanistic thermal conductivity model by focusing on the impact of gaseous fission products, which is coupled to swelling and fission gas release. The impact of additional defects and fission products will be added in future work. The model is developed using a combination of atomistic and mesoscale simulation, as well as analytical models. The impact of dispersed fission gas atoms is quantified using molecular dynamics simulations corrected to account for phonon-spin scattering. The impact of intragranular bubbles is accounted for using an analytical model that considers phonon scattering. The impact of grain boundary bubbles is determined using a simple model with five thermal resistors that are parameterized by comparing to 3D mesoscale heat conduction results. When used in the BISON fuel performance code to model four reactor experiments, it produces reasonable predictions without having been fit to fuel thermocouple data.
M. R. Tonks et al., "Development of a Multiscale Thermal Conductivity Model for Fission Gas in UO₂," Journal of Nuclear Materials, vol. 469, pp. 89-98, Elsevier, Feb 2016.
The definitive version is available at https://doi.org/10.1016/j.jnucmat.2015.11.042
Center for High Performance Computing Research
Keywords and Phrases
Analytical Models; Fission Products; Fuels; Gases; Grain Boundaries; Heat Conduction; Light Water Reactors; Molecular Dynamics; Phonons; Spin Dynamics; Thermal Conductivity of Gases; Thermocouples; Uranium Dioxide; Fission Gas Release; Fuel Performance; Intragranular Bubbles; Mesoscale Simulation; Molecular Dynamics Simulations; Multi-Scale Modeling; Thermal Conductivity Model; Thermal Resistor; Thermal Conductivity; Uranium Dioxide
International Standard Serial Number (ISSN)
Article - Journal
© 2016 Elsevier, All rights reserved.
01 Feb 2016