Nuclear energy is made available via two principles: 1) fission, in which energy is released by inducing heavy atoms to split into lighter elements, and 2) fusion, where energy is released by fusing light atoms together forming heavier ones. Fission is mature and is used throughout much of the world; fusion is the subject of significant research and investment, due to its potential to yield low-carbon, uninterrupted energy production without the yield of high-active radioactive waste produced in fission. When the fuel used in fission reactors reaches the end of its useful life it is deemed spent, and is either stored or dissolved and separated (the latter known as being reprocessed). The widespread expectation is that spent fuel from fission reactors that is not reprocessed will be disposed of in the form of intact fuel assemblies. However, thus far in the UK much of it has been stored under water to ensure that it is cooled satisfactorily and that the radiation from it is shielded, and this has resulted in some of the assemblies having water inside them. Similarly, where fuel material exists in disordered form associated with, for example, miscellaneous wastes from processing operations and accidents (known as fuel containing materials - FCM), often it has been stored in silos and again the abundance of water present needs to be assessed. It is important to understand the extent of the situation concerning water abundance in spent fuel and FCM prior to it being disposed of permanently (for example in an underground repository) because the water constitutes a significant influence on the stability of the fuel against an inadvertent nuclear reaction, and this could influence how it is stored and the safety case concerning the design of the repository it is stored in. A relevant recent example, and perhaps the highest-profile illustration of late, concerns the FCM at Chernobyl. This received widespread media coverage in 2021 when it was observed that the level of neutron radiation emitted by it was increasing. The debris in question had been shrouded by a new cover erected over the site to protect it from the elements and the suspicion arose that this was causing the fission rate in the material to escalate. Neutrons arise in materials containing fuel predominantly from fission in uranium-235, with the concern being that a fall in the water content in the debris was causing this to increase with the ultimate potential for uncontrolled energy release. However, the emission might also increase due to reduced shielding and absorption of neutrons by a reducing quantity of water, enabling more neutrons to get out, or by an increase in neutron-emitting reactions by alpha particles or due to the neutron detectors being used responding more efficiently at higher energies, none of which have implications as serious as an escalation in induced fission on uranium-235. Rather than measuring the neutron flux, as was the source of concern for the FCM at Chernobyl, greater insight might be gained concerning this complex problem by detecting the gamma rays that are emitted when neutrons are captured by isotopes in the surrounding materials. This has the advantage that the gamma rays have energies that are characteristic of the isotope producing them and that they are measured relatively easily: this is the focus of this proposal. For example, hydrogen emits gamma rays with an easily-identifiable energy of 2.223 MeV which could be characteristic of changes in water content and which might be separable from changes in the neutron environment. Interestingly, one of the few ways to measure fusion power aside from the neutron emission is also to study these emissions, by for example considering the 16.7 MeV emission from the deuterium-tritium reaction. In this project, we intend to bring together these opportunities to determine whether fission and fusion energy might benefit from high-energy capture gamma spectroscopy.

The accident at Japan's Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 represents one of the worst radioactive release events to have ever occurred. In the aftermath of the event approximately 160,000 people were evacuated from their homes - many of whom are still to return due to the high levels of radiation that surround the plant. While eight years have now passed since the multi-reactor incident, there still exists a considerable gap in the connected knowledge of not only where the radioactive particulate released during the accident exists and the state/form of such material, but also the state of the multiple damaged reactor cores and the resulting decommissioning challenges associated with the eventual fuel debris retrievals. Since the accident, and release of material from three of the site's nuclear reactors, there have been numerous studies on the microscopic material recovered from aerosol samplers, plant surfaces, bulk sediments and even articles of clothing. Such studies on the particulate extracted from these samples have provided stochastic insight into the nature/cause of the accident, its environmental legacy and more-importantly the conditions that will be faced during the soon to commence clean-up activities. The outcome of this project seeks to consolidate the multinational fragmented knowledge on this harmful, radioactive and chemotoxic contamination (most of which is easily inhalable being of micron-scale) to produce a cross-institutional platform (supported by the IAEA, Sellafield Ltd, JAEA and numerous international research organisations) on which information pertaining to the particulates location can be combined with experimentally-derived information (e.g. structure, form, composition). Such a collaborative platform would; (i) accelerate the understanding of the environmental hazards associated with this invisible material, and most-importantly over the next decade, (ii) provide the required physical data to support in-situ (reactor) measurements made using systems such as the University of Bristol "Rad Hard" Diamond Detection system.

Managing the UKs nuclear legacy is projected to cost £124B over the next century, a large portion of which derives from handling and disposal of highly radioactive actinide wastes, such as plutonium and uranium. Manual handling and chemical manipulation of these radioactive materials presents a hazardous task for the industry and requires extremely costly risk mitigation measures to be implemented. The risk is increased further by the potential of many actinide species to ignite on contact with air, meaning technologies must be used to prevent their exposure to oxygen and moisture. Recently, automation tools have increasingly been incorporated into a chemist's workflow, improving safety and throughput while decreasing time and labor costs. However, one reagent is constant in these systems, air. The impact this reactive gas has on the chemistry cannot be understated and a wealth of undiscovered science is made available by providing dry environments which allow experiments to be conducted under inert or different atmospheres. Importantly, the incorporation of remotely operable automation tools for actinide handling could dramatically increase the safety of researchers and decrease costs in the nuclear industry, all while allowing us to narrow the sizeable knowledge gap which currently exists for the behavior of these difficult to probe materials. In this Fellowship I will develop the first comprehensive automation technology for chemical manipulations in the absence of air and moisture and will collaborate with Sellafield nuclear site to develop safe tools for the remote automation of key inert operations. This work builds upon my track record in actinide science and automation of inorganic chemistry but also pushes further towards building tools which meet industrial needs. This project has three key steps: Build, Secure & Validate. I will first build a suite of technologies which allow automation of full reactions while excluding air and water allowing for a wide range of chemistry to be undertaken under different gas conditions. Firstly a low-cost remotely operable gas & vacuum distribution system will be developed which allows multiple reactors to be systematically purged of air and water along with a range of digitally controllable air-tight reactors for the safe storage and transportation of highly reactive species. I will also develop an integrated gas-liquid handing system increasing both safety and throughput of reactions under inert conditions. By designing the system with anaerobic handling in mind I will increase the speed at which we are able to investigate different reactions under inert conditions. Next, I will develop new strategies to ensure safe automation. I will collaborate with experts in sensor design to build feedback into the technology as an early detection system for potential hazards including pressure increases, elevated temperature and radiation leaks. I will also develop new risk assessment technologies which can flag potential hazards and suggest mitigation steps in advance. The technology developed herein will be validated on the synthesis of uranium compounds as models of nuclear waste materials behavior. Uranium imido complexes which can act as soluble analogues of the actinide oxo species present in nuclear wastes and allow us to deeply probe the behavior of these species. Utilizing my inert atmosphere technologies model complexes will be synthesized and subsequently reacted with a range of relevant contaminants (eg H2) using the technology described above. Finally, throughout this project I will collaborate closely with scientists as Sellafield. Together we will design experiments to meet their key challenges and demonstrate the utility of my technology for the industry. I will also build upon this Fellowship opportunity to deepen my ties within industry and work towards having my technologies implemented & handling radioactive materials at an appropriate UK site.

The proposed research will use U-containing particles found in the environment around the Fukushima Dai-ichi Power Plant as micro-scale representations of fuel debris and corium materials still inside the stricken reactors. By collecting, isolating and studying these particles we can build an improved knowledge base capable of underpinning the decommissioning of these highly degraded nuclear fuels within these damaged reactors (specifically Fukushima Daiichi, but also applicable to the Chernobyl nuclear power plant). There is equally an applicability to UK legacy nuclear sites, for example historic environmental contamination from Windscale or Dounreay. The development of this unique knowledge base will support a reduction in the hazard, cost and timescale of decommissioning, enabling accelerated decommissioning of nuclear sites. This may have a secondary impact of enhancing public acceptance of civil nuclear energy generation and geological disposal of radioactive wastes at an important time prior to the launch of the geological disposal facility siting process. At the same time, this research will build expertise towards the Civil Nuclear and Resilience Directorate's (CNRD) objectives to protect nuclear sites from threats and hazards; ensuring the UK's preparedness for civil nuclear emergencies and ensuring the UK is a leader on non-proliferation.

Processing of fine and cohesive powders is very difficult and often marred by inconsistencies in powder flow behaviour which adversely affects plant reliability and productivity. Good examples are in pharmaceutical, fine chemicals and nuclear industries, where dosing and dispersion of small quantities of cohesive powders is technologically very challenging. For instance for drug delivery through lungs the functionality of dry powder inhalers is strongly dependant on flowability of weakly compacted bulk powders. Current test methods for assessing the flow behaviour of powders (unconfined compression and shear cell testing) require a relatively large amount (at least 100 g) of powders. This is undesirable for industries such as nuclear and pharmaceutical due to ionising radiation for the former and toxicity, cost of drugs and lack of availability at the early stages of development for the latter. Furthermore the traditional test methods are not suitable for testing very weak compacts and the packing may be different from that used in the common methods such as unconfined compression and shear cell. Therefore the flowability of the sample has to be assessed in its own container. This research project is formulated to evaluate the analysis of the deformation and flow behaviour of fine cohesive powders at small scales (typically a few cubic mm) and at very low loads by the indentation probe method. An integrated approach is proposed to achieve the goal, which includes experimental work to analyse the mechanical properties of the single particles and bulk flow behaviour and simulation work to relate the bulk behaviour to the properties of primary particles. The described procedure will establish a link between the microscopic and macroscopic behaviour of particle assemblies subjected to compression and will elucidate the circumstances under which the particles form a strong compact. In particular the deliverables are:-a correlation between powder flow function, based on the unconfined yield stress, and indentation characteristics for samples of a few cubic mm;-a validated test methodology for measurement of the bulk yield stress of small quantities of cohesive powders;-an understanding of powder deformation at low loads.