Energy security and supply is of utmost importance in today's society and it is abundantly clear that nuclear fission will play an increasing critical role in delivering the net zero carbon agenda by 2050. A significant challenge for nuclear fission in the UK is its nuclear legacy, resulting from over 60 years of civil nuclear power generation and nuclear weapons production. This nuclear 'clean-up', including the decommissioning of legacy nuclear facilities and the long-term disposal of radioactive wastes, will cost upwards of £230bn and is a multi-generational project. To be able to progress safely, securely and efficiently with nuclear decommissioning and waste disposal, it is crucial to understand the underpinning chemistry of radionuclides within radioactive wastes. This project aims to deliver a step-change in fundamental understanding of uranium chemistry - a key component of radioactive waste management. Understanding uranium behaviour, e.g. uranium solubility and mobility, in engineered and natural environments is key to the safe decommissioning of legacy nuclear facilities and the long-term disposal of radioactive wastes. These systems are dynamic, with changes in chemistry likely to occur over the lifetimes of legacy nuclear and disposal facilities. It is therefore essential to understand how these changes in chemistry will impact on uranium behaviour in nuclear decommissioning and disposal scenarios including in deep geological disposal conditions. This fellowship will combine electrochemistry and advanced X-ray spectroscopies to investigate industrially and environmentally relevant reactions of uranium for the first time. Uranium behaviour is controlled by its oxidation state and the presence of complexing ligands, chemical species which are present in groundwaters and other solutions that come into contact with uranium-containing systems. These ligands can strongly bind uranium and stabilise solid- or solution-phase uranium species, significantly altering its behaviour. Changes in reduction/oxidation (redox) conditions can therefore have a significant impact on the behaviour of uranium and the chemical processes underlying these changes are not fully understood. These underlying chemical processes, or 'redox pathways', can control the eventual fate of uranium and the presence of different complexing ligands may significantly alter these redox pathways. Therefore, it is important to understand these fundamental processes to gain a holistic understanding of uranium chemistry and behaviour in dynamic systems where changes in redox and solution conditions may be expected. This fundamental understanding can then inform radioactive waste handling strategies and nuclear decommissioning approaches, promoting the safest and most efficient approaches to dealing with the nuclear legacy. In this fellowship, an electrochemical cell will be used to control the redox potential in experimental systems to change the oxidation state of uranium. Using a range of techniques, the changes in chemical bonding environment and oxidation state will be monitored during these reactions. The goal here is to produce controlled reactions whereby the changes in uranium chemistry at the molecular level can be probed during these key redox pathways, creating a step-change in the understanding of uranium redox chemistry in the presence of key complexing ligands. This analysis will be done using a multi-technique approach, measuring concentrations of uranium in solution and the chemical form of uranium in both the solid and solution phases. X-ray spectroscopy will be a key technique for analysing the chemical speciation, shedding new light on crucial reaction pathways occurring in these highly relevant systems.

Since the 2004 Energy Act, nuclear fission has rapidly grown, and continues to grow, in significance in the UK's Energy and Net Zero Strategies. Government's Nuclear Industrial Strategy states clearly that the nuclear sector is integral to increasing productivity, driving growth across the country and meeting our Net Zero target. Nuclear is, and will continue to be, a vital part of our energy mix, providing low carbon power now and into the future, and the safe and efficient decommissioning of our nuclear legacy is an area of world-leading expertise. In order for this to be possible we need to underpin the skill base. The primary aim of SATURN is to provide high quality research training in the science and engineering underpinning nuclear fission technology, focussed on three broad themes: Current Nuclear Programmes. Decommissioning and cleanup; spent fuel and nuclear materials management; geological disposal; current operating reactors (AGRs, Sizewell B, propulsion); new build reactors (Hinkley C, Sizewell C, possibly Wylfa Newydd; Future Nuclear Energy: Advanced nuclear reactors (light water reactors, including PWR3, gas cooled reactors, liquid metal cooled reactors, other concepts); advanced fuel cycles; fusion (remote handling, tritium); Nuclear Energy in a Wider Context: Economics and finance; societal issues; management; regulation; technology transfer (e.g. robotics, sensors); manufacturing; interaction of infrastructure and environment; systems engineering. It has become clear that skills are very likely to limit the UK's nuclear capacity, with over half of the civil nuclear workforce and 70% of Subject Matter Experts due to retire by 2025. High level R&D skills are therefore on the critical path for all the UK's nuclear ambitions and, because of the 10-15 year lead time needed to address this shortage, urgent action is needed now. SATURN is a collaborative CDT involving the Universities of Manchester, Lancaster, Leeds, Liverpool, Sheffield and Strathclyde, which aims to develop the next generation of nuclear research leaders and deliver underpinning (Technology Readiness Level (TRL) 1-3), long term science and engineering to meet the national priorities identified in Government's Nuclear Industrial Vision. SATURN also provides a pathway for mid technology level research (TRL 4-6) to be carried out by allowing projects to be based partly or entirely in an industrial setting. The consortium partners have been instrumental in a series of highly successful CDTs, Nuclear FiRST (2009-2013), NGN (Next Generation Nuclear, 2013-2018) and GREEN (Growing skills for Reliable, Economic Energy from Nuclear, 2018-2023). In collaboration with an expanded group of key nuclear industry partners SATURN will create a step-change in PhD training to deliver a high-quality PhD programme tailored to student needs; high profile, high impact outreach; and adventurous doctoral research which underpins real industry challenges.