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

Abstract

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%. (C) 2019 Elsevier B.V. All rights reserved.