Enhanced Methodologies for Advanced Nuclear System Safety (eMEANSS)

A re-assessment of the impact of uncertainties within the nuclear industry is of paramount importance, not only ensuring the continued safety of nuclear energy systems, but also to ensure the economic viability of nuclear power, allowing for continued reductions in CO2 emissions globally.

Uncertainties are unavoidable, and complex systems such as nuclear reactors are designed to cope with them. A naive approach would be to consider worst cases scenarios individually without considering their dependencies. This approach can produce over-designed and expensive systems without guaranteeing their overall safety. Proper quantification and propagation of uncertainty across multi-physical components allows one to determine vulnerable componentry, prioritise investments, identify operational margins and adopt relevant measures to guarantee safety whilst at the same time reducing the overall cost of advanced nuclear design.

Methods will be synthesised as part of this project to improve the estimation of uncertainty/safety, bringing together researchers specialising in reactor physics, fuel performance, structural materials and uncertainty quantification.

Work package 1: In reactor physics the new methods will be tested by considering the uncertainties propagated through a severe nuclear reactor accident assessment, specifically a loss-of-coolant accident (LOCA). The project will attempt to target and reduce uncertainties related to properties including nuclear data associated with specific isotopes and temperature dependent effects corresponding to neutron capture cross-sections. Drawing on the expertise in the UK and India, the enhancements in the methods utilised will have far-reaching impacts.

Work package 2: Fatigue failure of graphite components, especially at high service temperatures, is of serious concern for next generation reactors. A design tool is to be produced that can efficiently incorporate variances in the mechanical and thermal loading history, and material properties to quantify a probable component life. In addition to the simple uncertainties in boundary conditions, complications arise from both the load sequence and the temperatures at which loading occurs, coupled with the impacts arising from neutron irradiation, temperature and coolant interactions. The world-leading team in the UK and India will generate new knowledge on the high temperature cyclic response of advanced nuclear graphite and will utilise it in the development of a new probabilistic modelling framework.

Work package 3: Nuclear fuel performance codes predict the behaviour of fuel in a reactor, allowing operating regimes to be tested that avoid fuel melting or fuel failure. The models improved over decades of experience in the UO2-Zr system remain highly empirical (i.e. not mechanistic) and large uncertainties exist that are to be quantified through the use of uncertainty modelling (depending on each model's impact) and reduced through the addition of mechanistic models. Novel fuels with greater uncertainties will also be considered. Here, uncertainty modelling will be used to target the most rapid reduction of uncertainty of behaviour possible to expedite licensing and commercial use of the fuel.

Work package 4: The uncertainty models will be identified and commonalities will be linked to enable the overarching uncertainty methodology to be formulated. This is an important task that will ensure the outputs from the targeted examples (in work packages 1-3) have far reaching impact beyond themselves in other areas of nuclear engineering and beyond. In addition to linking the uncertainty modelling methods this work package will lead by communicating the results to the wider community through publications and workshops.

The project will provide impact in the following areas:
- Develop uncertainty modelling in the UK and Indian nuclear industries - driving efficiency increases and cost reductions in a sector that has highlighted this need.
- Ensure that the methods developed as part of this project are disseminated as efficiently as possible using a multi-faceted approach including traditional methods such as conferences and journal articles, as well as public workshops, glossy publications and development of a web-presence.
- Coordinated efforts with leading industry figures in the UK and India. Letters of support for the project have been provided by Wood Plc and the National Nuclear Laboratory (NNL) who will attend and contribute to the public workshops and private meetings. The NNL have also provided access to their fuel performance code - ENIGMA - to ensure that the outputs from the project will have industrial impact. Industrial impact through Wood and the NNL will also be gained as the outputs from this project will impact the Nuclear Innovation Programme (funded by BEIS) that both organisations are leading figures in.
- The improvement of methods used by industry will provide an economic benefit for the industry partners in this project and those that utilise the methods after dissemination through the public events and publications.

The need for improved methods involving better treatment of uncertainties is clear for nuclear new build in the UK, India and internationally. Without updated methods, the cost and speed of developing new nuclear systems is prohibitive, limiting the use of a low-CO2 producing power source. This sentiment has been highlighted by the UK government through the Nuclear Sector Deal and Nuclear Industry Strategy papers stating "a 30% reduction in the cost of new build projects by 2030" target; providing a "unique stock of technology and skills which will benefit other industries and services and which has significant potential in overseas markets"; aiming to "put the UK at the forefront of the artificial intelligence and data revolution"; and "to be a respected partner contributing significantly to appropriate international research programmes undertaken with selected international collaborators" working with our talented and enthusiastic Indian colleagues.