Plutonium dioxide is a very dynamic material. Radioactive decay damages the lattice and also forms other elements in the material. Helium, an inert gas, may be localised or trapped in the lattice, or maybe released. Uranium isotopes (formed from the decay of plutonium-238, 239, 240) and americium-241 (formed from decay of plutonium-241) are formed atom-by-atom within the plutonium dioxide lattice. The UK has 140 tonnes of separated plutonium in the form of plutonium dioxide, the World's largest civil stockpile. This has been separated over the last half century and will need to be stored for several decades into the future before its end use. Currently, Government intends most of this material to be made into nuclear reactor fuel ('mixed oxide fuel'), with a small proportion, which cannot be made into fuel, being disposed of as waste, although policy changes could lead to more of it being designated as waste. Whatever the final fate of the plutonium, the material will need to be processed into a suitable form for its end use, and its evolution while it is being stored will affect its suitability for processing. We therefore need to be able to predict how plutonium dioxide will change in storage, so we know whether it will be suitable for its final use. The purpose of this project is to understand how plutonium dioxide changes so we can make these predictions. We will make experimental measurements with plutonium dioxide to define the effects of radiation damage, helium formation and decay product formation on the material over timescales up to several decades. The evolution of plutonium dioxide will be explored using both a series of model samples and materials drawn from the UK stockpile. Behaviour of decay products will be determined using the stockpile materials. We will use synchrotron techniques (X-ray absorption spectroscopy, diffraction and tomography), electron microscopy and specific surface area measurements to characterise the materials. The results of these experiments will be used to develop computational models of plutonium dioxide evolution. Because decay products form atom-by-atom, and decay processes affect the electronic structure of the material, we need to model all these processes at the scale of individual atoms and small aggregates of atoms, but because the properties we are interested in are manifest at the lattice scale, we also need to understand how the atomic-scale effects carry across to this larger scale, and we will also develop models which we can use at this larger scale.

The proposed research will develop generic knowledge in the field of decommissioning engineering that can be used to solve problems associated with nuclear decommissioning. The work will be carried out under the auspices of the Dalton Institute of the University of Manchester and thus a multi-disciplinary approach to the research will be facilitated. Existing nuclear facilities (eg. Magnox, AGR Station, Reprocessing plant, medical waste) present significant challenges with respect to waste management and decommissioning. The research programme will expand and enhance the skill base in nuclear engineering and science in order to meet these challenges. Additionally, the research will provide valuable information for use in future generations of nuclear facilities so as to reduce decommissioning and waste management problems.The impact of the new Chair appointment will be enhanced by interactions with the already established links with industry and in particular with BNFL. Furthermore, the appointee will contribute to the training of research scientists, in an area of research where the demands of industry substantially exceed the availability of individuals with appropriate expertise.

Lancaster University is consistently ranked in the UK Top 10 (the only such NW university), and in the top 1% of universities worldwide. Lancaster plays a key role in the N8 Northern university partnership and the annual Higher Education Business and Community Interaction Survey places Lancaster in the UK top 10 for the number and value of its SME partnerships. To ensure the highest quality research Lancaster has made targeted investments of over £450m since 2004, with a further £135m planned for the next three years. Targeted and strategic investment is employed to expand in new areas and to improve performance in our current subject strengths. Areas of strength at Lancaster include: research in advanced functional materials; ultra-isolated environments; nuclear materials research; and development and the security of large-scale complex cyber-physical environments, and these four areas make up the themes of the experiment bundles in this application. Following a very strong performance in RAE 2008, we anticipate a strong outcome in the 2014 exercise to reinforce our position among the UK's very best research-led universities. The experimental equipment highlighted herein will support, refresh and update facilities in these areas. Existing academics in these fields have solid international reputations, and we are also recruiting 50 rising stars in celebration of our 50th anniversary, whose appointment will be strategically aligned to support and develop our very best research. Lancaster has a strong international presence through strategic international university and industrial partnerships. We collaborate globally on key research issues with international impact. Nationally, Lancaster is a leading research-intensive university. As a key partner in the N8 consortium, Lancaster contributes to the N8 database of assets and follows guidelines set out in the N8 Equipment Sharing Toolkit (N8 EST) to facilitate sharing of equipment between members. New state-of-the-art facilities in these key areas will lead to new research collaborations and opportunities - both at a national and international level and help to bring in talented collaborators not only to the UK but to the Northern region. Demand assessment studies conducted externally on behalf of Lancaster show significant industrial demand for the use of these facilities for their own research and development activities as well as research and innovation projects with the university. Lancaster University has an excellent track record of engaging with SMEs, and since 1998 it has delivered over 50 projects, part-funded by the European Regional Development Fund, totaling over £72m, enabling the university to work with over 5000 companies to date. An essential element of our sustainability model is the promotion of industrial access to our facilities and resources. The university already has in place access arrangements for industry in key facilities (InfoLab21, Lancaster Environment Centre and Engineering), with over 100 company staff currently co-located in facilities in our departments. The new Collaborative Technology Access Programme (cTAP) at Lancaster will develop a business model to provide managed industry access to an increasingly wide range of technologies on the campus, including the facilities highlighted within this proposal. We are developing a single entry route to our facilities, supported by a business-facing group of technical staff and believe we will be the first university to offer this service.

We propose to carry out fundamental mathematical research into efficient methods for problems with uncertain parameters and apply them to radioactive waste disposal.The UK Government's policy on nuclear power states that it is a proven low-carbon technology for generating electricity and should form part of the UK's future energy supply. Energy companies will be allowed to build new nuclear power stations provided sufficient progress is made on the radioactive waste issue. In common with other nations, geological disposal is the UK's preferred option for dealing with radioactive waste in the long term. Making a safety case for geological disposal is a major scientific undertaking. National and international research programmes have produced a good understanding of the mechanisms by which radionuclides might return to the human environment and of their consequences once there. One of the outstanding challenges is how to deal with the uncertainties inherent in geological systems and in the evolution of a repository over long time periods and this is at the heart of the proposed research.The main mechanism whereby radionuclides might return to the environment, in the event that they escape from the repository, is transport by groundwater flowing in rocks underground. The mathematical equations that model this flow are well understood, but in order to solve them and to predict the transport of radionuclides the permeability and porosity of the rocks must be specified everywhere around the repository. It is only feasible to measure these quantities at relatively few locations. The values elsewhere have to be inferred and this, inevitably, gives rise to uncertainty. In early performance assessments, relatively rudimentary approaches to treating these uncertainties were used, primarily due to the computational cost. Since then, there have been considerable advances in computer hardware and in the mathematical field of uncertainty quantification. One of the most common approaches to quantify uncertainty is to use probabilistic techniques. This means that the coefficients within the flow equations will be modelled as random fields, leading to partial differential equations with random coefficients (stochastic PDEs), and solving these is much harder and more computationally demanding than their deterministic equivalents. Many fast converging techniques for stochastic PDEs have recently emerged, which are applicable when the uncertainty can be approximated well with a small number of stochastic parameters. However, evidence from field data is such that in repository safety cases much larger numbers of stochastic parameters will be required to capture the uncertainty in the system. Only Monte Carlo (MC) sampling and averaging methods are currently feasible in this case, and the relatively slow rate of convergence of these methods is a major issue.In the work proposed here we will develop and analyse a new and exciting approach to accelerate the convergence of MC simulations for stochastic PDEs. The multilevel MC approach combines multigrid ideas for deterministic PDEs with the classical MC method. The dramatic savings in computational cost which we predict for this approach stem from the fact that most of the work can be done on computationally cheap coarse spatial grids. Only very few samples have to be computed on finer grids to obtain the necessary spatial accuracy. This method has already been applied (by one of the PIs), with great success, to stochastic ordinary differential equations in mathematical finance. In this project we will extend the technique to PDEs, developing the analysis of the method required, and apply the technique to realistic models of groundwater flow relevant to radioactive waste repository assessments. The potential impact for future work on radioactive waste disposal and also for other areas where uncertainty quantification plays a major role (e.g. carbon capture and storage) is considerable.

In UK Energy strategy, nuclear fission is growing rapidly in significance. Government's recent Nuclear Industrial Strategy states clearly that the UK should retain the option to deploy a range of nuclear fission technologies in the decades ahead, and that it should underpin the skill base to do so. The primary aim of Next Generation Nuclear is to provide high quality research training in the science and engineering underpinning nuclear fission technology, focused particularly on developing a multi-scale (from molecular to macroscopic), multi-disciplined understanding of key processes and systems. Nuclear fission research underpins strategic UK priorities, including the safe management of the historic nuclear legacy, securing future low carbon energy resources, and supporting UK defence and security policies. It has become clear that skills are very likely to limit the UK's nuclear capacity, with over half of the civil nuclear workforce and 70% of Subject Matter Experts due to retire by 2025. High level R&D skills are therefore on the critical path for all the UK's nuclear ambitions and, because of the 10-15 year lead time needed to address this shortage, urgent action is needed now. Next Generation Nuclear is a collaborative CDT involving the Universities of Lancaster, Leeds, Liverpool, Manchester and Sheffield, which aims to develop the next generation of nuclear research leaders and deliver underpinning (Technology Readiness Level (TRL) 1-3), long term science and engineering to meet the national priorities identified in Government's Nuclear Industrial Vision. Its scope complements the Nuclear IDC (TRL 4-6), with both Centres aiming to work together and exploit potential synergies. In collaboration with key nuclear industry partners, Next Generation Nuclear will build on the very successful Nuclear First programme to deliver a high quality training programme tailored to student needs; high profile, high impact outreach; and adventurous doctoral research which underpins real industry challenges.