Nuclear fusion, Generation IV fission reactors and aerospace gas turbines are critical to our future energy generation and transportation. Their operation at high temperatures necessitates construction from a variety of advanced materials. In order to withstand these extreme environments materials require high melting points, high temperature strength and environmental resistance, and, for nuclear, irradiation resistance. There are strong environmental and economic incentives to yet further increase the temperature capability of the materials used, in order to improve efficiency to reduce fuel use, as well as for improve performance, design life and safety. However, while iterative improvements are being made year on year the temperature gains are becoming ever harder to realise. In this proposal a step change in temperature capability is sought by the realisation of a new class of body-centred-cubic (bcc, an atomic crystal structure) superalloys based on (1) Tungsten, (2) Titanium, and (3) Steel, for the extreme environments of nuclear fusion and gen IV fission reactors as well as aerospace gas turbine engines. I will create a close network of industrial, national and international academic partners, that will enable translation of these advanced materials from concept through to scale-up. The collaborations will be split across the bcc-superalloys Work Packages: (WP1) Tungsten, bringing in Culham Centre for Fusion Energy (CCFE), and ANSTO Sydney, toward nuclear fusion and Gen IV fission; (WP2) Titanium, brining in TIMET and Rolls Royce, for aero-engines, as well as ETH Zurich for thin film based alloy discovery; (WP3) Steel, bringing in Rolls Royce, for gas/steam turbines, and the Max-Planck-Institut für Eisenforschung (Iron Research, MPIE) Dusseldorf for advanced characterisation and steels expertise. Bcc superalloys comprise a metal matrix, where the atoms are arranged in a bcc crystal structure, which are reinforced by forming precipitates of high strength ordered-bcc intermetallic compounds (e.g. TiFe or NiAl). This has parallels to the strategy used in current face-centred-cubic (fcc) nickel-based superalloys. However, changing the base metal's crystal structure, and therefore also the reinforcing intermetallic compound, represents a fundamental redesign and necessitates the development of new understanding. The key advantage of using a bcc refractory-metal-, titanium-, or steel- based superalloy is their increased melting point(s), which give the possibility of increased operating temperatures, as well as greatly reduced cost for the case of steels. However, the change in crystal structure requires a fundamentally new design strategy. While the limited investigations into bcc superalloys have indicated that they have attractive strength, and creep resistance, they have been held back by their low ductility. During this fellowship, I will thoroughly investigate multiple ductilisation strategies on bcc-superalloys to advance their technology readiness level (TRL) and so remove the current barrier to their commercialisation. Investigation of the systems will be undertaken by myself, the 2 Research Fellows (RF), technician, and PhD students allowed for by the programme, as well as staff time from the project partners (CCFE, TIMET, Rolls Royce, ANSTO, ETH Zurich and MPIE). The PhD students will undertake alloy development between: WP1 on Tungsten alloys 50% supported by CCFE, WP2 on Titanium, two students, one 50% by TIMET and a second 50% by Rolls Royce, with a fourth school funded by UoB on WP3 industrially supervised by Rolls Royce. The two 2 RFs and technician would work in alloy development and characterisation alongside these students, but also perform more detailed investigations, with one RF focussed on irradiation damage mechanisms, and the second RF on deformation mechanisms, both using advanced microscopy and micromechanics on which the related students would be progressively trained.

With the UK committed to reducing its reliance on fossil fuels by 2050, there must be a commensurate increase from other energy sources to maintain and provide for increased energy requirements, at the same time increasing the diversity in energy sources. As a mature and clean energy production method, nuclear power will no doubt make a significant contribution to the UKs energy portfolio. The UK currently operates a civil nuclear fleet consisting primarily of advanced gas reactors (AGRs). Any new nuclear build in the forseable future will likely be new Pressurised Water Reactor (PRW), such as the Westinghouse AP1000 or Areva European Pressurised Reactor (EPR). Both reactors are designed to run using UO2 fuel types enriched with fissile uranium to ~3-5%. In addition to these generation III and III+ type of reactors, some fourth generation (GenIV) reactor types are designed to operate using UO2 fuels (3 out of the 6 final designs). Furthermore it is becoming more desirable by plant operators to increase the level of burn-up in the fuel, not only increasing the efficiency of the reactor, but also reducing operating costs and minimising the volume of nuclear waste produced. One key factor limiting higher burn-up of nuclear fuel is the production and accumulation of fission products within the fuel that can significantly affect the physical properties and limit performance. Broadly speaking, there are four different characteristic fission products produced during burn-up: gaseous, metallic precipitates, oxide precipitates, and those in solid solution. The work to be undertaken here examines the behaviour of fission products under irradiation in both a non-radioactive model nuclear fuel simulant (ceria) and in simulated and real spent nuclear fuel. These materials will be fully characterised, both structurally and chemically, through a combination of transmission electron microscopy and atom probe tomography, with the results being fed back to modellers to validate and/or benchmark predictive models for in-core performance of the fuels, such as ENIGMA. The behaviour of nanocrystalline materials under irradiation will also be investigated. Nanocrystalline materials are viewed to be a viable route towards radiation tolerance, and may therefore improve safety, due to the high number of grain boundaries and interfaces present acting as efficient sinks for defects. It is therefore critical that information on the radiation response of nanocrystalline materials is obtained if this class of materials is to be used in nuclear reactors as a means to improve reactor safety. This characterisation of the materials in the as-received and irradiated state will be performed using the electron microscopy and atom probe capabilities at Oxford University. The ceria samples will be provided by the Universities of Nebraksa and Sheffield, and the real/synthetic/simulated fuels samples will be provided by the National Nuclear Laboratory. The NNL - who will benefit significantly from the results to be obtained from this project - will provide advice in the safe handling of radioactive material, and will provide access to the hot/active transmission electron microscope at the Sellafield central laboratory for characterisation of active samples.

"Weld modelling" is a powerful tool in understanding the structural performance of welded structures. Conventional continuum-mechanics-based predictions of the stresses generated by welding have achieved considerable success in understanding the in-service performance and degradation mechanisms of welds in the UK's nuclear reactor fleet. However their practical use is currently limited to materials that do not undergo so-called solid state phase transformation (SSPT) during welding, since the presence of SSPT makes it necessary to predict changes in the material microstructure in order to predict the stresses. In addition, the microstructural changes imposed by welding have a profound influence on a weld's resistance to creep, thermal ageing, oxidation, stress corrosion and other in-service degradation mechanisms, and upon its sensitivity to the presence of cracking. The Fellowship research programme aims to extend conventional weld modelling into a multi-disciplinary tool that can predict both continuum parameters such as stress & distortion, and microstructural parameters such as grain size and shape, the occurrence of secondary phases, and precipitate distributions, and hence both directly predict long term structural performance and be used for "virtual prototyping " of weld processes and procedures for novel welding processes. Success offers the prospect of better understanding of in-service performance of welds in both the existing UK nuclear reactor fleet, and in any industrial sector where the long term structural performance of welds is important. It will also aid the choice of weldment materials, joint design and welding process for structural welds in new-build nuclear power plants, and in advanced Generation IV designs that may be built on a longer time frame.

Nuclear fission offers a reliable low carbon source of energy, but, the nuclear waste generated as a result of nuclear reactor operation needs proper treatment and confinement in a durable material to ensure that the biosphere is not contaminated with radioactive elements in the near and long-term future. Geological disposal (GD) - which involves confining the host material inside a safety barrier (usually a metal canister) and then permanent deposition of such wastepackages in a pre-selected geological site - is now an internationally accepted methodology including the UK. Nonetheless, after thousands of years, the outer safety barrier will get corroded and the host material will be exposed to the surrounding geological conditions. When in contact with water/moisture, the radioelements may be released from the host matrix into the surrounding geology from where they can be transported into the biosphere. Understanding long-term changes in the wastepackages -starting from the day of their fabrication - is a key element in addressing the eventual release of the radioisotopes. Besides corrosion, one of the reasons why the wastepackages will change under geological disposal conditions is the fact that radioactive decay of the confined radioisotopes will damage the host matrix at atomic level called as self-irradiation damage. This damage accumulation over hundreds of thousands to millions of years can potentially alter the chemical and mechanical durability of the wastepackages. These irradiation induced modifications can have a significant effect on the eventual release of the radioisotopes. Thus, addressing radiation stability of the wastepackages is an essential part of demonstrating long-term safety of the geological disposal. This research proposal will utilize MIAMI irradiation facility at the University of Huddersfield to study the effects of self-irradiation damage and He accumulation in various types of waste packages ranging from glasses to glass-ceramic composites. Using a transmission electron microscope with in-situ dual-ion-beam irradiation, the irradiation induced modifications will be monitored in real time. The dual-ion-beam irradiation represents the closest analogue to self-irradiation damage in nuclear wasteforms yielding reliable and realistic results. These ion irradiation effects will be compared with actinide doping studies to be undertaken in collaboration with nuclear industry partners, thereby, allowing establishing the irradiation conditions necessary to simulate the self-irradiation damage. The research will be undertaken on leached (gels) and non-leached materials to understand the irradiation induced evolution of the wastepackages and address the effect of radiation damage on the leaching and vice versa. By collaborating with external partners such as ANSTO Australia, CEA Marcoule France, University of Cambridge and, National Nuclear Lab UK, this proposal will bring together the experience and expertise of internationally recognised researchers to develop a better understanding of the wasteform evolution due to self-irradiation damage under geological disposal conditions including leaching.

Temperature records are critical for understanding past and future climate. However, reconstructing past temperature dynamics is incredibly difficult. Of the currently available terrestrial archives of past temperature, these are often spatially limited, suffer from ambiguity around calibration, or require large sample sizes. These issues have prevented the development of a high resolution, high density network of terrestrial temperature records. This is now often considered the single most significant gap in the palaeoclimate archive. Here, we seek to provide a breakthrough in the field of temperature reconstruction by developing a new palaeothermometer. For this, we use speleothems (cave stalagmites). Speleothems grow in layers, which can be dated like the rings in a tree. The chemistry in each layer offers an unprecedented resolution of environmental information, constrained by an absolute age model over 500,000 years. At the Lancaster Environment centre, we have recently developed a technique which allows phosphate to be extracted from the stalagmite layers. This is a critically important advance in the research field, as phosphate-oxygen isotopes are known to be controlled by temperature dynamics. Our first measurements of the phosphate-oxygen isotope composition in cave drip waters and modern cave calcite provide clear evidence that the cave temperature signal can be captured and stored within the speleothem record. As the internal temperature of shallow cave systems are known to reflect the external average air temperature (plus or minus localised effects), this provides an exciting opportunity through which a truly independent terrestrial temperature record may be built. This research aims to build and test a modern-day calibration between cave temperature and speleothem phosphate-oxygen isotopes. This will enable a platform from which precisely dated, well preserved, independent temperature records can be confidently obtained from the global archive of speleothems at a spatial and temporal scale hitherto unprecedented.