Meeting the growing energy demand from an increasing population, whilst addressing the depletion of fossil fuels and reducing greenhouse gases is the one of the grandest scale challenges of the 21st century. Currently, around 15% of the world's electricity is generated by nuclear fission energy, the largest supply by any non-greenhouse gas emitting resource and it will be critical to the country's energy mix if the UK is to meet its goal of net zero carbon emissions by 2050 as evidenced by the construction the UKs first nuclear power plant in two decades at Hinkley point C. However, new materials are being developed to improve the intrinsic safety of current nuclear reactors and for deployment in future nuclear power plant technologies. The fuel materials to be studied in this project include uranium silicide, nitride and boride and cladding materials, silicon carbide, zirconium carbide and zirconium nitride will be studied to asses their feasibility for use in current and next generation nuclear power plants by using ion beam irradiation to mimic the conditions of a nuclear reactor and performed an in-depth characterisation of the materials post irradiation. These novel fuel materials are strong candidates to replace current uranium oxide fuel assemblies due to their much higher thermal conductivity, which will reduce fuel temperatures and buy vital time in an accident scenario, such as Fukushima like accident. The cladding materials also have much higher melting temperature than the currently used Zr alloy in water cooled reactors and so would delay or even mitigate meltdown scenarios. If these materials can prove themselves in current nuclear reactors for these reasons, they will also be promising for deployment in next generation nuclear power plants which will operate at much higher temperatures and under more extreme radiation damage. Radiation damage from neutron bombardment causes atomic displacement which leads to defects in materials that can evolve as a function of temperature. In addition to this build-up of defects, gases (such as hydrogen and helium) can accumulate from transmutation reactions. These gases interact with the defects formed and can further degrade the mechanical and thermophysical properties. Research into the effects of radiation damage on the properties of these advanced non-oxide ceramics are in their infancy and will need to be better understood before the materials can be developed further and eventually deployed. This project will use facilities at the Nuclear Fuel Centre for Excellence and the Dalton Cumbria Facility (DCF) based withing the Henry Royce Institute to manufacture, irradiate and perform micro and nano-structural characterisation of the materials post irradiation. Thermal analysis of the materials will then be performed at project partners at the University of Oxford and The Massachusetts Institute of Technology (MIT) will answer the key question - what effect does radiation damage have on the superior thermal conductivity of these materials and do they fall to levels below which developing these new materials becomes uneconomical? Finally, from the highly detailed understanding of the effect of radiation damage on their micro and nano-structure, can we reverse engineer these materials

Starting in early April 2020, wildfires have, to date, burnt about 500 square km of land in the Ukrainian Chernobyl Exclusion Zone (CEZ). Formed as a result of evacuation following the 1986 accident at the Chernobyl nuclear power plant, the CEZ (2600 square km) and the adjoining similar sized area of Belarus now constitute the third largest nature reserve in mainland Europe. Although levels of radioactivity remain high in some areas of the CEZ and it includes the world's most radiologically contaminated ecosystems, the CEZ is internationally recognised as an iconic example of rewilding (ecosystem recovery/restoration). The current fires are the worst in the 34 y history of the CEZ and have decimated large areas of forest and former meadow land, including in the most contaminated areas. These fires have the potential to remobilise contamination, modify ecosystem services and result in long-term habitat change. Given the importance of the CEZ as a natural laboratory, research into the impacts of the fires needs to start as soon as possible. This urgent research activity must capitalise on the opportunity to learn how fire affects radiologically contaminated landscapes whilst also establishing post-fire baseline data to underpin future CEZ research. CHAR brings together an interdisciplinary network (from hydrology to social science) of three UK organisations with key European and Ukrainian collaborators (both researchers and practitioners). The CHAR team's UK and international partners have collaborated for >20 years, including successfully coordinating extensive field research in the CEZ since 1993. The CHAR team is in a unique position to conduct the proposed research because of baseline data from our previous NERC-funded projects, including one which investigated the impacts of a fire in the small (<6 square km) but highly contaminated Red Forest area in 2016, and long-term data holdings for the CEZ held by Ukrainian collaborators. CHAR will address four key research questions: (i) What is the influence of the fires on birds and mammals in the CEZ?; (ii) Have the fires increased the mobility of radionuclides for uptake into plants and/or transfer to aquatic systems?; (iii) Do repeated fires and radiation stress impact soil function in the Red Forest?; and (iv) Does contaminated smoke present a significant risk to fire fighters and the wider public? CHAR's results will benefit any users of the CEZ natural laboratory, including radioecologists studying the effects of radiation on wildlife, environmental modellers and those undertaking broader ecological research on rewilding. The findings of CHAR will also be used to inform future management of the CEZ and other contaminated regions (such as the large forest areas in Fukushima). Fires in radiologically contaminated regions give rise to concerns from both those responding to the fires (e.g. fire fighters) and the wider public; CHAR's independent risk assessments will be useful in addressing these concerns. Recognising that CHAR research will mainly take place during a period of international travel restrictions due to the coronavirus pandemic, the work programme has been specifically designed to ensure that all aspects can still be completed successfully. The longstanding collaborations between the UK and Ukrainian scientists and a proven track record of delivering NERC research in the CEZ during a previous period of travel restrictions (due to the armed conflict on the eastern Ukraine border) provide a high degree of confidence in the ability of the CHAR team to deliver all aspects of the proposed research. The Ukrainian collaborators have the support of the relevant Government Agency and already have permissions to work in the CEZ during the coronavirus pandemic. Additionally, the Ukrainian collaborators have the equipment and consumables required to begin the CHAR research activities as soon as CHAR is approved.

For all sources of radioactivity, radiological risk assessments are essential for safeguarding human and environmental health. But assessments often have to rely upon simplistic assumptions, such as the use of simple ratios in risk calculations which combine many processes. This pragmatic approach has largely arisen due to the lack of scientific knowledge and/or data in key areas. The resultant uncertainty has been taken into account through conservative approaches to radiological risk assessment which may tend to overestimate risk. Uncertainty arises at all stages of the assessment process from the estimation of transfer to human foodstuffs and wildlife, exposure and risk. Reducing uncertainty is important as it relates directly to scientific credibility, which will always be open to challenge given the highly sensitive nature of radiological risk assessment in society. We propose an integrated, multi-disciplinary, programme to assess and reduce the uncertainty associated with radiological risk assessment to protect human health and the environment. At the same time we will contribute to building the capacity needed to ensure that the UK rebuilds and maintains expertise in environmental radioactivity into the future. Our project has four major and highly inter-related components to address the key goal of RATE to rebuild UK capacity and make a major contribution to enhancing environmental protection and safeguarding human health. The first component will study how the biological availability of radionuclides varies in soils over time. We will investigate if short-term measurements (collected in three year controlled experiments) can be used to predict the long-term availability of radionuclides in soils by testing our models in the Chernobyl exclusion zone. The second component will apply the concepts of 'phylogeny' and 'ionomics' to characterise radionuclide uptake by plants and other organisms. These approaches, and statistical modelling methods, are increasingly applied to describe uptake of a range of elements in plant nutrition, and we are pioneering their use for studying radionuclide uptake in other organisms and human foods. A particularly exciting aspect of the approach is the possibility to make predictions for any plant or animal. This is of great value as it is impossible to measure uptake for all wildlife, crops and farm animals. The third component of the work will extend our efforts to improve the quantification of radiation exposure and understanding of resultant biological effects by investigating the underlying mechanisms involved. A key aim is to see whether what we know from experiments on animals and plants in the laboratory is a good representation of what happens in the real world: some scientists believe that animals in the natural environment are more susceptible to radiation than laboratory animals: we need to test this to have confidence in our risk assessments. Together these studies will enable us to reduce and better quantify the uncertainties associated with radiological risk assessment. By training a cohort of PDRA and PhDs our fourth component will help to renew UK capacity in environmental radioactivity by providing trained, experienced researchers who are well networked within the UK and internationally through the contacts of the investigators. Our students will be trained in a wide range of essential skills through their controlled laboratory studies and working in contaminated environments. They will benefit from being a member of a multidisciplinary team and opportunities to take placements with our beneficiaries and extensive range of project partners. The outputs of the project will benefit governmental and non-governmental organisations with responsibility for assessing the risks to humans and wildlife posed by environmental radioactivity. It will also make a major contribution to improved scientific and public confidence in the outcomes of environmental safety assessments.