[en] Highlights: • Stress and strain distributions of microcell UO₂-5 vol% Mo pellets under thermal expansion were investigated. • Formation of Mo network in UO₂ pellets could reduce the maximum hoop stress and radial strain of UO₂ pellets. • Microcell UO₂-5 vol% Mo pellets could considerably reduce the maximum cladding stresses. - 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%.