Summary For a lot of academic and industrial research into nuclear energy, using NNUF and other facilities, it is important that neutron-irradiated material of known provenance is available. Getting samples irradiated in reactors is both time-consuming and expensive, and as much use as possible should be made of existing material. There is a wide range of surveillance and other samples in the UK, owned by organisations like the Nuclear Decommissioning Authority (NDA), EDF Energy and Rolls-Royce. Establishing either a central or distributed archive of a selection of this material that can be accessed by researchers has been identified as a priority by the UK Government's Nuclear Innovation and Research Advisory Board (NIRAB). The archive is the second item in the table of favoured investments in EPSRC's NNUF Phase 2 call. While the Irradiated Materials Archive Group (IMAG), comprising universities, National Nuclear Laboratory (NNL), UK Atomic Energy Authority (UKAEA), NDA and other stakeholders, has developed this concept, further work is required before the key stakeholders are in a position to decide if and how to proceed. Options could range from leaving the material where it presently is and having systems that enable individuals to ascertain the material and pedigree available, and request samples for their research, to bringing samples from locations in the UK to dedicated stores at Sellafield (higher activities) and UKAEA's Culham site (low-activity). It is, therefore, proposed that the archive is taken forward in two stages. Stage 1 is an option study and the subject of this proposal. At the end of Stage 1, key stakeholders - including EPSRC, the owners of the material and the managers of proposed stores - would decide whether to proceed and with which option. Stage 2 would require a new proposal for funding based on cost estimates established in Stage 1. However, an upper bound for the latter is indicated in this proposal. Important considerations in Stage 1 include: ascertaining what material samples are available and which are of interest to UK researchers; logistical issues including ownership and liability, transport and waste disposal; and the requirements for the archive database(s). An attractive option for the last of these may be for NDA and other owners of material to manage their own databases in a way that permits users to interrogate these and request samples. UKAEA, NNL and the University of Bristol (UoB) propose to undertake Stage 1 and produce an options appraisal for EPSRC and its NNUF Management Team, having consulted all stakeholders. This would take 19 months and require £524,000. Wide-ranging support for this proposal is confirmed by letters from Dame Sue Ion (first chair of NIRAB), the CEO of the Henry Royce Institute for Advanced Materials and AWE. The NDA has been consulted in the drafting of this proposal and expressed its willingness to collaborate in the project, as has Rolls-Royce in its letter of support. The US has had a national archive for some years and learning from its experience would be part of this project; a letter confirming the value of the archive is from the Director of Nuclear Science User Facilities at Idaho National Laboratory.

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.

This research project will apply aperture synthesis, a diagnostic technique used routinely in radio astronomy, to make the first time-resolved measurements of the current density in the tokamak plasma edge. This measurement is crucial for understanding violent eruptions known as ELMs which could be extremely damaging for ITER, the next generation fusion device. At EUR10Bn, ITER is one of the largest international science projects on Earth.Fusion involves making two positively-charged nuclei collide to produce a heavier nucleus, releasing energy in the process. This can only occur at temperatures of about 100 million degrees. The fundamental challenge to performing fusion is to confine the hot ionised gas (plasma) sufficiently well. The principle behind the leading candidate design for a fusion power plant (called a tokamak) is to use the fact that the charged particles of the plasma state respond to electromagnetic fields, which can be used to confine them away from the material walls of the device. If sufficient heating power is injected into a tokamak plasma, then it enters a high-confinement mode. In this mode, the thermal energy of the plasma increases by about a factor of two due to the creation of a highly insulating layer near the plasma edge, which is typically only a few centimetres thick, compared to the body of the plasma which can be a metre or so across. The pressure gradient in this edge layer is extremely high, so there is a vulnerability to instabilities. The plasma experiences a repetitive series of violent plasma eruptions called Edge Localised Modes, or ELMs, which expel large amounts of energy typically within about a hundred millionths of a second. These are an interesting scientific phenomenon on today's tokamaks but on ITER, where the ejected power in an ELM is expected to be an order of magnitude larger, they could cause serious damage if not controlled. There are ideas for how to control ELMs that work on existing tokamaks, but to extrapolate them reliably to ITER requires a more detailed understanding of the physics. In order to test and constrain theoretical models for ELMs, we need to be able to measure the current density and pressure gradient in the thin edge layer. While a number of tokamaks have a good measurement of the pressure gradient, the current density is much more challenging, and the role of the current density in ELMs remains unconfirmed experimentally.This project will develop a novel diagnostic technique to measure the edge current density on the MAST tokamak routinely (in the sense that in principle the process could be automated). Our diagnostic technique will also have good time resolution, being able to make several measurements of the edge current density through an ELM and address the intriguing question of how (or whether) the current density is flushed out of the plasma edge region within the ELM time-scale (ie about 100 microseconds).The physical basis for this diagnostic technique is the directional emission of electron Bernstein wave (EBW) radiation, which is an example of electron cyclotron emission (ECE). Bernstein waves are electrostatic plasma waves generated in the plasma core at frequencies typically around tens of gigahertz. Most of these outgoing waves are reflected back into the core from a cut-off layer, but waves travelling at a particular angle with respect to the equilibrium magnetic field undergo a mode conversion to an electromagnetic wave that enables them to travel to the plasma edge and to be observed. The EBW emission profile allows us to measure both the direction of the magnetic field, and the rate at which it is changing. Since we know the absolute value of the toroidal magnetic field (it varies inversely proportionally with the distance from the centre of the device), we can use the rate of change of direction of the field to calculate the current density.

In 2018, the Exascale Computing ALgorithms & Infrastructures for the Benefit of UK Research (ExCALIBUR) programme was proposed by the Met Office, CCFE and EPSRC (on behalf of UKRI). The goal of ExCALIBUR is to redesign high priority computer codes and algorithms, keeping UK research and development at the forefront of high-performance simulation science. The challenge spans many disciplines and as such the programme of research will be delivered through a partnership between the Met Office and UKRI Research Councils. Research software engineers and scientists will work together to future proof the UK against the fast-moving changes in supercomputer designs. This combined scientific expertise will push the boundaries of science across a wide range of fields delivering transformational change at the cutting-edge of scientific supercomputing. DiRAC proposed the inclusion in the ExCALIBUR business case of a request for £4.5M in capital funding over 4.5 years to develop a hardware fore-sighting programme. Industry co-funding for the programme will be sought where possible. The £4.5m capital is intended to provide a testbed area that uses pre-commercial equipment for software prototyping and development. It has two main purposes: (1) to enable the software community to be ready to use commercial products effectively as soon as they come on to the market; and (2) to provide the UKRI HPC community with the ability to influence industry and the necessary knowledge to guide their purchase decisions. This will ensure that facilities and the future UK National e-Infrastructure are in a position to maximise value for money by getting the most powerful systems exactly suited to the communities' needs. This double-pronged approach will give UK researchers a competitive advantage internationally. ExCALIBUR will now establish a set of modest-sized, adaptable clusters dedicated solely to this purpose and embedded within established HPC environments. Although small, they need to be of a scale capable of carrying out meaningful performance studies. They are expected to be co-funded with industry partners and will initially require investments of £200k-£300k each, and will allow a range of future hardware to be assessed for its relevance to the delivery of UKRI science and innovation. The pre-commercial equipment will be refreshed and added to on a regular, likely to be annual, basis. This agile tactic is designed to take advantage of the different approaches across industry (some companies, e.g. NVidia tend to have a short (less than 3-month) pre-commercial window while for others this can be up to a year). ExCALIBUR can use the hardware piloting systems to drive software innovation across the UKRI research community. Researchers are rightly reluctant to invest time in code development to take advantage of new hardware which may not be available at scale for several years or may even prove not to have longevity - scientific leadership demands that research funding is used to deliver science results now. In addition and DiRAC and others will offer funded RSE effort to support the development work combined with access to novel technologies within modest-sized systems, Excalibur can lower the bar for engaging with the process of software re-engineering and encourage researchers to make the necessary (modest) investments of their time. In some cases, there may also be the potential for some immediate science outputs by exploiting the proof-of-concept systems. Excalibur will thus be able to provide an incentive for greater software innovation across the UKRI research communities and help to ensure that when novel technology is included in national services, there are workflows that are already able to exploit it optimally. This will increase productivity across all UKRI computing services and enable UK researchers to use the latest hardware to deliver the largest and most complex calculations, ensuring international leadership.

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