PROGRESS IN THE DEVELOPMENT OF HIGH DENSITY FUELS FOR ENHANCED ACCIDENT TOLERANCE

Fuel materials with uranium densities higher than UO2 could bring significant economic benefits to accident tolerant fuel concepts. The most promising candidate materials, UN and U3Si2, also have improved thermal properties compared to UO2 resulting in additional safety benefits. This paper describes experimental studies of high temperature reactions between UF6 and silicon which, if promising, might be used to develop a commercially scalable fabrication route for U3Si2 which avoids the need to use uranium metal. Investigations into optimising the pelleting procedures for U3Si2 are also outlined, using a conventional arc melted feedstock. In addition, a novel thin film approach has been used to fabricate idealised surfaces of uranium nitrides and oxides. The reaction of water (and hydrolysis products such as H2O2) with these surfaces has been studied using highly surface sensitive techniques, such as X-ray reflectivity and X-ray photoelectron spectroscopy revealing insights into the reaction mechanisms that are still debated within the literature.