Prediction of minimum UO 2 particle size based on thermal stress initiated fracture model

Abstract

An analytic study was employed to determine the minimum UO 2 particle size that could survive fragmentation induced by thermal stresses in a UO 2Na fuel-coolant interaction (FCI), based on a brittle fracture mechanics approach. Solid and liquid UO 2 droplets were considered, with perfect wetting by the sodium or finite heat transfer coefficient. The analysis indicated that particles below the range of 50 μm in radius could survive an FCI under the most severe temperature conditions without thermal stress fragmentation, and seemed to verify the experimental observations as to the range of the minimum particle size due to thermal stress fragmentation by FCI. The basic complexities in fracture mechanics make further investigation in this area interesting but not necessarily fruitful for the immediate future.