Population growth worldwide and the drive for economic development will enormously increase energy demands. Current projections estimate that global energy needs will more than double by 2050. Although fossil fuel resources and proven reserves are still large (possible use of oil and gas for 50 years and coal for 275 years) their use could be severely restricted because of the emitted CO2 and their impact on climate change, problems with security of supply and for geopolitical reasons. Nuclear energy from fission can provide substantial amounts of carbon free electricity and process heat and significant expansion is planned worldwide.
One of the main concerns in nuclear power generation is the management of the radioactive spent fuel from the nuclear reactor, because it can remain radiotoxic for about 200,000 years. In reprocessing through a series of operations the spent fuel is concentrated and usually uranium and plutonium are separated from the rest of the minor actinides and fission products. This reduces the volume and toxicity of the remaining spent fuel and reduces the demands on geological repositories. The separated uranium and plutonium can be recycled back to the reactor and extend in this way the supply certainty of uranium.
Reprocessing technologies have remained unchanged for the last decades and have not taken advantage of the enormous strides in other areas of process industry. In the Department of Chemical Engineering we are investigating processes based on intensified separation units and molten salts technology.
Intensified separators. We are studying intensified separation units for the liquid-liquid extraction of uranyl ions consisting of channels with characteristic dimensions in the order of a few hundred microns. The thin fluid layers that form in the small channels significantly reduce mass transfer resistances and the time required for separation. The intensification also results in reduced amounts of organic solvents. We use advanced diagnostics to investigate the configuration of the liquid-liquid flows in the small channels
Molten salts are an excellent reaction medium – hot, liquid and ionically conducting. This technology is the foundation for a research programme to deliver nuclear fuel reprocessing by materials electrosynthesis through direct oxide reduction and selective electrodissolution and electroplating. Developing, optimising and controlling these processes will provide methods for, and a fundamental understanding of how best to reprocess nuclear fuel. This is in addition to the development of techniques for new molten salt systems, new sensing and analysis technologies and the establishment of the kinetics and mechanisms by which molten salt processes occur. This will facilitate rapid process development and optimization, as well as the generation of applications in related areas.