THE EFFECTS OF MANUFACTURING PARAMETERS ON THE PROPERTIES OF URANIUM SILICIDE NUCLEAR FUEL

Abstract

As a response to the 2011 nuclear accident at the Fukushima Daiichi nuclear power station the nuclear industry has begun to work on so-called Accident Tolerant Fuels (ATF) as a means to prevent core damage and release of radionuclides into the environment as a result of a Fukushima-style accident at another plant. ATF is concerned with modifying the existing UO2-Zr fuel-cladding system in light water reactors to improve the safety characteristics, and particularly to reduce the potential to create hydrogen when oxidised. One candidate material to replace the UO2 fuel is uranium silicide in the U3Si2 phase. In this work U3Si2 has been synthesised by arc-melting of elemental uranium and silicon. The resulting material has been comminuted by planetary ball milling and fabricated into pellet samples to represent nuclear fuel. The sintering time of each pellet was varied to develop changes in density and microstructure in order to establish the dependency of these properties on sintering parameters. The pellet samples have been characterised, with measurements taken of the thermal expansion, thermal diffusivity and specific heat using pushrod dilatometry, laser flash analysis and differential scanning calorimetry respectively. Microstructural studies have also been carried out to examine the structure of both pellets and as-cast material. The reaction of U3Si2 with CO2 has also been studied, as have additional fabrication efforts including a cerium loading into two pellets to act as a surrogate for plutonium. The sintering time was not found to have an impact on thermophysical properties or microstructural development over the range of times and the temperature examined. The reaction with CO2 was found to be energetic and rapid, culminating in the production of U3O8. Cerium containing samples were found to have cerium precipitates in discrete regions rather than a solid solution of cerium throughout the samples.

Date of Award	16 Mar 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Joel Turner (Co Supervisor) & Timothy Abram (Main Supervisor)