Adaptive hierarchical radiation transport methods to meet future challenges in reactor physics

This proposal comes at a time when the UK nuclear sector is resurgent. It is now widely accepted that one of the ways in which the UK can meet its commitments to reducing CO2 emissions, as well as dealing with its over-reliance on imported fuel supplies, is to replace the current fleet of ageing nuclear reactors. However, in recent years the UK has seen a substantial reduction in trained scientists and engineers and this skills shortage is now approaching a critical point. Unless immediate action is taken the skilled work force will be too small to oversee safe operation, decommissioning and waste disposal from the current nuclear power facilities, let alone satisfy demand driven by any future new build. In addition, many nuclear related issues also remain unsolved, from new reactor designs to waste disposal, and so increasing our expertise as well as our understanding in nuclear is of great importance. In this proposal we will address many of the main issues by developing novel approaches for radiation transport modelling (RT). This will enhance our understanding across a range of fields from reactor physics, radiation shielding and radiation damage to criticality safety and waste disposal. This will put the UK back at the forefront of RT research. It will also inform policy makers, scientists and engineers involved in energy and environmental initiatives and increase confidence in nuclear safety and waste disposal.
RT modelling has been notoriously difficult. This is partly due to the high complexity of the 7 dimensional phase-space that describes radiation transport, but also the inherent multi-scale geometries within reactor cores are beyond the modelling capabilities of most numerical schemes. Multi-scale, reduced order, and adaptive numerical methods can therefore be extremely valuable to this area of reactor physics. They can link together the numerous length-scales, from the smallest fuel element to the largest fuel arrays, with mathematical rigour whilst forming computationally efficient and fast solutions. The proposed work will realise this potential by developing, for the first time:
1) A full multi-scale model for RT that rigorously links all length scales for reactor physics applications.
2) Embedded reduced order methods that significantly reduce computational complexity by several orders of magnitude through the reduction of large scale models to only a few hundred unknowns.
3) Error estimates that enable adaptive capabilities which can resolve the full 7D phase-space & focus computing resources on resolving the key physics, therefore increasing efficiency without compromising accuracy.
4) Parallel solver technologies for the efficient solution of large scale problems that can be carried out on current & future multi-core computer platforms.
5) Embedded data assimilation methods that link the above technologies with known nuclear data uncertainties to form error bounds on solutions & other key parameters.
This will provide new information on uncertainties, sensitivities & errors resulting from variations in geometry, material data and other input parameters.
Our overall aim of this project is the accurate prediction of RT using a world leading model. The novel technologies including; multi-scale methods, reduced order models, error estimates, adaptivity, data assimilation and parallel solvers will be implemented within our finite element RT model framework RADIANT. By providing a model with advanced numerical technologies that accurately capture intricate geometric detail, combined with estimates of errors and sensitivities, we can enable the user to make informed judgements on a wide range of nuclear applications. This will have wide ranging impacts, e.g. informing government and regulatory bodies, enhancing company and stakeholder capabilities and ensuring that the scientific communities research methodologies are cutting edge. This will serve to increase confidence, mitigate errors and reduce risk.

This work will benefit those scientists, government bodies and industries concerned with nuclear power safety and coupled systems. This includes areas of multi-phase flows, structural models, damage models, geological safety of waste repositories and state-of-the-art computational modelling. Specific organisations that will benefit from these advanced RT technologies include AWE, AREVA, NNL, NDA, HSE, Rolls-Royce and EDF (now running UK nuclear reactors).

Example benefit areas include: Optimising fuel loading, reactor lifetime extension, and planning for safe decommissioning, this work will also be of interest to wider EPSRC and NERC communities. For the EPSRC community, areas where our work will be of benefit include: plasma physics, imaging, nuclear waste modelling and thermal radiation research (in combustion and furnaces). NERC communities will benefit from this next generation RT technology for research on cloud physics for climate and process study models, spectral wave models for free surface and internal waves in oceans, and RT processes within meteor impacts. The use of our RT technologies for the above listed research themes will advance climate models, earth system science, prediction of natural hazards, and other related technology areas. Many of the techniques and tools we will be working on are also of interest to the wider computational physics community. There is strong potential for their re-application to resolve other physical phenomena using the general adaptive discretisations, data assimilation, multi-scale models and solver technologies. There is also a strong interest in using this software for multi-physics simulations in National Laboratories including those in the USA, France and Japan, where our researchers already have links.

This proposal comes at a time when the UK is in danger of being dominated by overseas commercial software and we are not on a level playing field when contributing to science and engineering in this important area. This proposal will therefore help correct this trend, by providing a modern approach to reactor physics, criticality and shielding applications. This will result in improved safety for new build and decommissioning activities, by providing an independent and improved alternative to vendor codes from France and the USA. This work will therefore play many important roles ranging from informing government policy decisions on energy to addressing the general public's concern regarding nuclear power safety and with safe decommissioning and waste disposal.

The project also has an important economic impact as it will help combat the introduction of commercial software from abroad. At present this is eroding UK software sales and damaging the prospects for growing UK licence sales during the forthcoming era of new build. If allowed to continue it could cost the UK nuclear industry hundreds of thousands of pounds per annum if a competitive UK alternative is not launched soon. This project will also aim to expand and market beyond the UK and seek new business in overseas governmental and industrial bodies, including the US, Japan and Mainland Europe. Our technologies will also make inroads into the main energy hubs, particularly in the US where we already have strong links, and thus increase the project's economic impact on a global scale, improving UK competiveness and revenue flow through increased licence sales abroad.