Nuclear energy is a CO2 neutral energy generation technology and will play an important role in reducing green-house gas emissions to meet government and societal targets and improve the quality of life. However, a main concern of the nuclear energy is its safety. The next generation nuclear reactors under development to be deployed in the next decades are aimed at achieving inherent safety using technologies such as passive cooling. Such systems require a significantly advanced thermal hydraulics approach to deal with much higher temperature and pressure systems and/or non-conventional coolants such as liquid metal and molten salts. The traditional methodology is insufficient to deal with the new challenges to be encountered. The proposed CCP for nuclear thermal hydraulics is aimed at building and supporting a community of researchers and engineers for developing and maintaining computational methods and software packages to modernise the nuclear thermal hydraulics tools to meet the demands imposed from the development of advanced next-generation nuclear reactor systems. The activities of the proposed CCP are grouped into two work packages. WP1 is aimed at community building and networking through a variety of activities and events. These include annual technical meetings, special topic, cross-CCP and international workshops, training courses, international and UK visit/exchange programs, benchmarking exercises and various outreach activities. WP2 is aimed at development and maintenance of methodology and computer code for the community through services provided by STFC's Computational Science Centre for Research Communities. The work includes supporting, developing and maintaining (i) robust (reliable, affordable and user-friendly) CFD methodologies and tools for the analysis of reactor systems and (ii) high fidelity modelling and simulation methods and software tools, focusing on a community DNS code, aimed at providing new understanding and benchmarking database for modelling validation and engineering correlation development. The CCP will also explore innovative and disruptive methodologies aimed at bringing a step-change in computational thermal hydraulics analysis. The proposed CCP is formed from academic and industrial partners. The initial academic memberships are Universities of Manchester, Sheffield, Leeds, Liverpool John Moores, Cambridge, Oxford, Bangor, Queen Mary, Imperial Colleague London and STFC Daresbury Laboratory. The industrial partners are EDF Energy, Frazer-Nash Consultancy, Moltex, Rolls-Royce and Wood Nuclear. The CCP also includes an international partner and advisor from Penn State University/Argonne National Laboratory. The CCP will encourage any interested researchers and engineers to become a member when it is up and running and any activities organised by the CCP are open to the entire community.

In order to meet the UK's carbon reduction targets, and achieve an energy mix that produces less CO2, we must continue to investigate ways in which to make nuclear power cleaner, cheaper and safer. At the same time, as new reactors such as Hinkley Point C are built, the UK needs to develop the work force who will operate, regulate and solve technical problems in civil nuclear power, in order to capitalise on our investment in nuclear energy. Important in this respect is that the UK currently operates mainly old advanced gas-cooled reactors, fundamentally different from the next fleet of UK nuclear power stations, which will be light-water reactors. Key to this change, in terms of this research project, is that Zirconium is a preferred fuel cladding material in LWRs. A major part of a nuclear reactor is the fuel assembly - the structure that encapsulates the highly radioactive nuclear fuel. Understanding the performance of the materials used to make these assemblies is critical for safe, efficient operation, and they must be able to maintain their structure during normal operation, handling and storage, as well as survive in the unlikely event of an accident, when they become crucial in preventing the escape of radioactive materials. Because of the need to operate nuclear reactors as safely as possible, fuel is often removed well before it is spent, as we currently do not know enough about fuel assembly materials, so must adopt a highly cautious, safety-first approach. This does mean, however, that it is more costly to run a reactor, as assemblies must be replaced well before all the fuel is consumed, and this also means the assembly then - prematurely - becomes additional nuclear waste, which must be safely handed and stored, at further high cost. By gaining greater understanding of how assembly materials perform when irradiated, we will be able to make more accurate safety cases, which will mean that fuel assemblies can be used for longer periods without additional risk. Such knowledge will enable the UK to operate the next generation of reactors far more efficiently, significantly reducing the cost of nuclear power. This is particularly important now, given that the UK is going to have light-water, instead of advanced gas-cooled, reactors, and with it the fuel assembly and its material will change very fundamentally. This research effort will also significantly benefit other countries using nuclear energy, which will establish the UK as a centre of expertise in the area. This will further attract inward investment in research and development in the UK, creating future wealth and employment alongside cleaner energy. A second key theme of the project will be to explore the use of zirconium alloys in critical components for future fusion reactors. The UK has a leading position in defining the materials that will be chosen for the ITER and DEMO international fusion projects, and this theme will contribute to maintaining the UK's reputation as a centre of excellence in fusion research.

This is currently one of the most exciting and dynamic periods for UK nuclear science & engineering since the 1950s. Inter alia, both new reactor build (essential to meet climate change targets) and the decommissioning of the UK's legacy nuclear sites (a 120 year, £121 bn programme) are driving forward, BEIS are investing heavily in the new national nuclear innovation programme and the sector deal for the industry has just been published. The already acute need for skilled nuclear scientists and engineers is therefore increasing and will continue to do so into the long term. To address these needs we propose a CDT in Nuclear Energy (GREEN), a partnership between 5 of the UK's leading nuclear universities and 12 industry partners, addressing EPSRC priority area 19: Nuclear Fission & Fusion for Energy. Evolving from the very successful Next Generation Nuclear (NGN) CDT, GREEN will deliver comprehensive doctoral training across the whole fission fuel cycle as well as in allied areas of fusion. Inspired by changes in external drivers and feedback from alumni, employers and funders, GREEN will offer both academically- and industrially- based research pathways, linked to enhanced employability training. We will further widen our already strong industry engagement by inclusion of new external partners, and align closely with other national and international activities, including other proposed CDTs. Experience from NGN suggests we will be able to leverage EPSRC support to give a typical cohort size of 15-20 students. Remarkably, using the leverage of 40 studentships from EPSRC, GREEN has already secured a further 47 studentships from Industry and Academia, ensuring a minimum number of 87 students in the GREEN CDT.