Mapping the UK’s road to advanced nuclear fuels

The UK’s National Nuclear Laboratory (NNL) is leading the UK’s Advanced Fuel Cycle Programme (AFCP) which recently marked a ‘major milestone’ when it published a series of roadmaps. Gareth Headdock, NNL’s science and technology & government programmes director says, “By taking a strategic approach to the fuel cycle, the UK will ensure it can achieve the nuclear ambitions set out in the government’s plans. The pathways described in the roadmaps will support the development and success of this future-focused approach.” 

The UK believes it can build on a long history of fuel development and manufacture, and a significant present capability, to continue to develop a world-leading UK RD&D capability able to address immediate challenges and respond to future needs that are not yet fully understood. The programme aims to give both policymakers and industry the foresight they need to build capability and capacity. 

The roadmaps are set out in a new report: ‘Fuelling Net Zero: Advanced Nuclear Fuel Cycle Roadmaps for a Clean Energy Future’. 

The report first discusses the use of roadmaps. It says this approach is now widely used to align R&D with goals and strategy. A roadmap “sets a pathway from current capability towards a future vision and identifies key opportunity areas.” It can support innovation and build consensus on priorities and actions required to move forward.

The process starts by defining the context, drivers of change and understanding of future energy systems. It then considers opportunity areas and specific applications within them. That indicates the necessary technologies and capabilities that will be required, which allows enablers to be identified — strategic planning, industry collaboration and government support.

Developing the roadmap

The process starts by establishing a vision. The vision for
a 2050 UK fuel cycle capability was set out in by the UK government in 2013 in the ‘Nuclear Industrial Strategy’ ’ and the supporting Nuclear Energy Research and Development Roadmap. It included:

• UK supplying the fuel needs of Gen III+ and any Gen IV and small modular reactors (SMRs) 
• UK industry having a strong domestic capability from fuel enrichment and manufacture, reactor technology, operations to recycling and waste minimisation, storage and disposal.

In 2020 an Energy White Paper (a first step towards new legislation) set out a potential role for large, small and advanced nuclear in delivering net zero. Next it is necessary to develop future nuclear deployment scenarios to understand potential fuel cycle demands. Working with the Energy Systems Catapult (ESC), AFCP modelled likely scenarios in which the UK would meet its goal of net zero by 2050 on which to base its roadmaps. They found that: 

• A wide range of nuclear deployment pathways are possible, from zero to over 60GWe installed capacity 
• Large, small and advanced reactors could all play a part in reaching net zero by 2050. 

The fuel cycle implications for this range of deployment have to be assessed. But investing in innovation in the fuel cycle could enhance exports, create jobs and drive down the cost of clean energy. 

Advanced fuels have the potential to improve the economic performance of future nuclear systems. In addition, the development of advanced fuels is an essential component for developing advanced fuel cycles and considering new fuel processing technologies. 

Advanced reactor fuels may need higher density fissile materials and higher thermal conductivity since the reactors tend to operate at higher heat generation rates. They may also use recycled fuel as part of an integrated fuel cycle, requiring the development of recycling technologies that can produce the required fuels for future applications. 

Although the relative numbers remain low, the UK is internationally recognised as having world-leading capability across the fuel cycle. 

Recent public investment, through AFCP and broader UK Research Council-funded programmes in academia, has helped to further improve capability. If the UK continues to invest in advanced fuels and fuel cycle RD&D it can maintain and develop these strategically important capabilities. 

The UK may need a range of new and existing fuel types, and recycle technologies and advanced fuel cycles are a logical path to sustainability. 

The resulting roadmaps therefore include advanced fuels for a range of reactor applications and the consideration of fuel recycle technology.

The roadmaps

The opportunity areas identified for the UK, which form the basis of the new technology roadmaps, fall into two categories: 

• Advanced fuels roadmaps: advanced technology fuels (ATFs); coated particle fuels (CPFs); and fast reactor fuels and fuel cycle.    
• Sustainable advanced fuel cycle roadmaps: advanced recycle of LWR fuel to produce future fuels; advanced recycle technology of ATF to produce future fuels; and pyrochemical (molten salt) recycle technology to produce future fuels. 

These roadmaps represent evolution, rather than being detailed project plans, and they will themselves evolve over time. 

They are set out in full in Fuelling Net Zero: Advanced Nuclear Fuel Cycle Roadmaps for a Clean Energy Future
but a brief indication of each follows.

Advanced fuels roadmaps

Advanced technology fuels (ATFs, coined from their initial acronym — accident tolerant fuels) were initially developed for their robust properties, but they must also deliver improved performance and economics. 

AFCP’s work has been aligned with the Westinghouse EnCoreTM ATF products, as it has an operational fuel manufacturing site in the UK, but the technology roadmap is not intended to be vendor-specific. It focuses on three areas: in the near term on coated Zr alloy cladding and in the longer term on high density fuels (eg uranium nitride) and advanced cladding (eg silicon carbide) composites.

The roadmap suggests there is potential for commercial coated cladding and next-generation ATF to be manufactured in the UK in the next 10 to 15 years, which would help to secure indigenous fuel manufacturing capability. Enablers identified in the roadmap include international partnering, access to irradiation and post-irradiation examination facilities, and nuclear data requirements for new fuel qualification.

Coated particle fuels (CPFs) have a ‘kernel’ of fissile material, typically uranium dioxide, with outer layers for protection and to form a barrier to fission products. There is growing interest in CPFs for high temperature reactors and they are also being considered for LWR applications, and for applications involving novel micro-reactor and space reactor systems. Through AFCP, the UK is re-establishing capabilities to manufacture CPF. The CPF U
V technology RD&D roadmap focuses on developing kernel and coating technology, as well as encapsulation technology.

Fast reactor fuels have a long history in the UK. Revitalising the UK’s expertise in this area through AFCP will address the needs of the continued interest in fast reactor systems, such as the UK’s AMR programme. 

AFCP focuses on installing UK capability to research and optimise the manufacture of fast reactor fuel pellets within the NNL Central Laboratory at Sellafield in Cumbria. The aim will be to manufacture UK fast reactor specification MOX fuel for the first time in over 20 years and develop broader capabilities that will contribute to development of sodium fast reactor technology. 

It is also exploring fast reactor fuel recycle technology by building on collaborative European R&D programmes, addressing specific challenges around using LWR fuel recycling technologies for fast reactor fuels. That includes high plutonium contents, high radiation levels and significant heat generation. 

The fast reactor fuel and fuel cycle RD&D roadmap covers both uranium-based fuels with steel cladding and plutonium and minor actinide-based fuels and cladding with the enabling recycle technology.

Sustainable advanced fuel cycle roadmaps 

To modernise the fuel cycle and ensure sustainability, future fuel must come with fuel recycling.

An advanced PUREX process is being developed within AFCP which aims to shrink the current approach. It will
use a much smaller single-cycle process and simplified, more flexible operations along with proliferation barriers. The secondary wastes generated will be minimised at source. 

This roadmap focuses on the core recycle process, process technologies and key waste management technologies. The key technology development needs are:

• Head end operations, including shearing, fuel dissolution and conditioning of uranium oxide (UOX) and MOX fuels 
• Processes for separating uranium and plutonium (and potentially neptunium) from fission products, avoiding a pure plutonium stream at any point in the process 
• Simple processes for recovering minor actinides from high level liquid wastes 
• Co-conversion of mixed products to fuel precursors with acceptable properties for fuel fabrication 
• An integrated and optimised secondary waste management strategy with advanced abatement and immobilisation 
• Innovative online analysis for process monitoring, control and safeguards.
• Government support is important across three broad areas: policy, infrastructure and international. 

The roadmap notes that work on plutonium disposition and re-use and minimising the size and inventory of a geological disposal facility (GDF) provide drivers for capability development. There is a possible future market for advanced reactor fuel. Enablers include infrastructure for active demonstrations, international partnering and advanced modelling and simulation tools. 

Importantly, the UK has globally unique experience and near-term efforts are needed to capture this before it is lost with the completion of industrial reprocessing at Sellafield.

The advanced recycle RD&D roadmap for a revolutionary concept ATF will depend on the fuel concept taken forward, but will have strong overlaps with the roadmap for advanced recycle of LWR fuel. It focuses on the additional R&D needed to address revolutionary concept ATF recycle which is expected to mainly impact the head end fuel preparation steps. Alongside the LWR oxide fuel recycle roadmap additional development would focus on, for example, nitrogen-15 recovery. 

There should be credible technical options for fuel recycle within the next 10 to 15 years, enabling a decision on the requirement for future reprocessing and recycle of fuel in the UK. 

Drivers include the development and qualification of an ATF product, a potentially expanded nuclear programme in the UK and the possible deployment of AMRs using advanced fuels. 

Enablers include the ability to make simulant fuels, international engagement and access to infrastructure for active demonstrations.

Pyrochemical (molten salt) recycle technology to produce future fuels is a complementary approach to aqueous recycling based primarily on the electrorefining of fuels. AFCP is placing a strong focus on salt chemistry and engineering to rebuild UK expertise in this field and better understand its science and engineering challenges. As well as the core metal electrorefining processes, the programme is looking pyro-processing for oxide fuels, via electroreduction, and some of the cross-cutting challenges with molten salt advanced reactor (MSR) technologies. Finally, off-gas capture and salt treatment and immobilisation are key strands. 

This roadmap focuses on developing an advanced recycle process for high burn-up fuel. The skills developed here will support wider UK ambitions. Technology includes electroreduction and electrorefining, while waste management development includes technology for clean-up of the salt from the recycle process. 

These three core areas are inextricably linked with the chemistry and electrochemistry of each and key enablers identified in the roadmap include building a skills pipeline, knowledge capture, international engagement and developing the supporting infrastructure for active demonstrations. 

The full roadmaps are available at:
https://afcp.nnl.co.uk/wp-content/uploads/sites/3/2021/06/AFCP-Advanced-Nuclear-Roadmaps.pdf