Numerical and experimental investigation on thermal expansion of UO2-5 vol% Mo microcell pellet for qualitative comparison to UO2 pellet

Thermally conductive microcell UO2 pellets in which metallic networks enclose UO2 granules have been highlighted due to their enhanced thermal performance for a potential candidate of accident-tolerant fuels. However, studies on thermal expansion effects of microcell UO2 pellets are still lacking. Here, stress and strain distributions of the fabricated UO2-5 vol% Mo microcell pellet under thermal expansion were investigated. After we confirmed that the numerical results agreed well with experimental measurement in terms of linear thermal expansion, stress and strain distributions of the microcell pellets were calculated under maximum stress and maximum strain conditions. As a result, formation of Mo network decreases the maximum hoop stress and the maximum radial strain of UO2 pellets by 50.9% and by 29.4%, respectively under a linear heat generation rate of 200 W/cm. Finally, the UO2-5 vol% Mo microcell pellet can decrease the maximum cladding stresses by 36.7%.