Q&A: UKAEA Directors on the UK’s quest to lead on nuclear fusion

JP Casey 28 November 2019 (Last Updated November 27th, 2019 17:32)

The UK is home to the world’s largest magnetic fusion experiment and the UK Atomic Energy Authority has started work on a new nuclear test facility in Rotherham. Here two UKAEA directors, Colin Walters of the National Fusion Technology Platform, and Howard Wilson of the STEP Programme explain how the UK could be poised to lead a nuclear fusion revolution.

Q&A: UKAEA Directors on the UK’s quest to lead on nuclear fusion
“Fusion is a key element in a portfolio of sustainable energy sources that will help combat climate change,” said Howard Wilson. Credit: Robert Mumgaard

JP Casey (JPC): How will the new nuclear test facility in Rotherham help expand the UK’s nuclear fusion capabilities?

Colin Walters (CW): Over the last 50 or so years, the majority of research into fusion energy has focussed upon the physics of the incredibly hot plasmas from which the power is generated. However, given the UKAEA mission to help develop fusion power to a point it can be put into commercial operation, it is now also vital that we fully understand the materials from which such systems will be built and are also able to validate the manufacturing processes that will be employed.

This is the primary purpose of our new facility in Rotherham; although there are already many nuclear research facilities already in existence both in the UK and elsewhere, these are largely focussed on supporting current and future systems which obtain power from the process of nuclear fission. As the conditions within fission power plant are markedly different from those anticipated within future fusion systems, the materials used to fabricate the systems are different.

We are therefore currently designing a world-first test facility, to be sited at Rotherham, which will allow us to evaluate the performance of new materials and prototype structures under many of the arduous conditions that will be experienced in a future fusion power plant. Although entirely non-radioactive, the facility will be able to simulate the combined effects of vacuum, extreme heat loading and high magnetic fields.

Installation of the test facility will begin as soon as the new UKAEA building is completed in September 2020. The facility is expected to initially employ approximately 40 highly qualified staff and is also expected to attract visiting researchers from across the world. The reason for siting the facility in Rotherham is that the region is the heart of the UK’s advanced manufacturing capability and that such a location will greatly enhance our ability to collaborate and engage with the region’s industrial and academic organisations.

JPC: How does the UK’s nuclear fusion infrastructure compare to that of other countries, and why is nuclear power so crucial to the future of the world’s energy mix?

Howard Wilson (HW): The UK has amongst the strongest fusion infrastructure in the world. It hosts and operates for the EU the most advanced experiment in the world, JET, as well as operating a wide range of facilities that underpin the commercialisation of fusion energy: the compact, innovative MAST Upgrade spherical tokamak reactor; the Materials Research Facility for analysing activated materials; the RACE robotics and remote maintenance facility; the H3AT tritium science facility, and the Fusion Technology Facilities.

Fusion is a key element in a portfolio of sustainable energy sources that will help combat climate change, especially as power consumption grows into the second half of the century and renewables will struggle to keep up with demand in all parts of the world.

Building on its expertise and the range of facilities available, the UK is embarking on an ambitious programme called STEP – Spherical Tokamak for Energy Production – that aims to lead the way to delivery of the first fusion power to the grid by the early 2040’s; the UK Government recently awarded £222M to complete the first five-year design phase of the STEP Programme.

JPC: Would you say the UK is in a unique position with regards to fusion development, and why have other countries not invested as heavily in the technology?

HW: The strength of UK fusion is the expertise of its scientists and engineers, established with over 50 years of experience, and the breadth of state-of-the-art facilities.

To achieve fusion requires the fuel to be heated to extreme conditions, which takes a lot of power – this means it is not possible to take incremental steps that progressively demonstrate steadily increasing amounts of net power output. Rather, one needs to exceed a certain high input power and a certain size of reactor core to deliver any significant fusion power at all. As a result, a large capital investment is required to establish the conditions required for efficient fusion power production. This, in turn, creates an extremely hostile environment with high thermal power loads onto material surfaces, high electromagnetic loads from the magnets that hold the fuel, and high fluxes of damaging neutrons into the reactor vessel components.

Testing materials in such conditions is a major challenge, and an important part of the ongoing R&D to advance towards the world’s first net fusion power output. The STEP programme aims to achieve these conditions early to not only demonstrate the feasibility of fusion power generation, but also to optimise components and materials to be employed in the subsequent fleet of commercial fusion reactors. The high capital investment, combined with the infrastructure needed, can be a barrier to some countries entering the fusion field before its commercial phase.

JPC: Does international collaboration have a role to play in developing nuclear power generation?

HW: Because of the scale of fusion power, it can most efficiently advance when the associated costs are shared. ITER embodies such an international partnership, with seven parties, including the EU, coming together to build a reactor that will produce 500 megawatts of fusion power. While it will not generate electricity, the ITER results will be crucial for optimising the class of energy-producing fusion reactors beyond, including STEP.

Another important example of international collaboration is materials testing in a fusion neutron environment. The EU is working together to design, and then build, a billion-pound-scale neutron irradiation facility called IFMIF-DONES. This will help identify and qualify the materials and components required for the first demonstration reactors.

Thus, while single countries can, and will, make huge advances, these advances are best built on the achievements and goals of the international fusion community – especially ITER. STEP embodies this philosophy, seeking to build on the UK’s international partnerships, including ITER and IFMIF-DONES, to accelerate the pathway to fusion commercialisation.

JPC: What are some of the challenges remaining to the widespread adoption of nuclear fusion power, and how could they be overcome?

HW: Some of the biggest challenges include: developing the right magnetic ‘cage’ to hold the fuel in fusion conditions [which] is at the heart of the reactor concept we call the ‘tokamak’; identifying and qualifying the reactor materials that perform well over long periods of time in the hostile fusion environment; developing the robotic and remote maintenance systems to enable rapid replacement of damaged components that are key to high availability; breeding and managing sufficient tritium fuel to sustain the fusion reactor; extracting the fusion power and efficiently converting it to electricity; managing the high thermal loads associated with the heat exhaust system; and preventing the hot fuel, which takes the form of a plasma, from damaging the reactor.

Thus, the obstacles are largely technical, but because of the scale a large financial investment is required. The funding provided for the STEP programme, working alongside international collaborative programmes, will progressively address the technical challenges as well as one further key challenge – how to integrate all the different subsystems into a single coherent design to deliver electricity to the grid on a 2040s timescale.