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.