The Final Frontier: Focusing On Fusion

Online Editor

Tony Roulstone details the complex path to commercialisation

The promise of fusion is to provide low-cost, zero carbon energy without the problems of long-term radioactive waste. Because it uses isotopes of hydrogen as its fuel, there seems to be no limit to the energy that fusion can provide. The prospects for fusion are looking up with the construction of the large machine in France – ITER – that aims to demonstrate that fusion works. Also, fusion is attracting huge amounts of private investment stimulating many different ideas about how to commercialise fusion. These developments are laid out in the 2021 report: Fusion energy: A global effort – A UK opportunity from the Institution of Mechanical Engineers.

Most of the fusion talk is about the physics – how to make fusion work and the results from the latest experiments. The record for fusion power is still held after 20 years by JET for a fusion burn lasting just 20 seconds. It had a gain of only 0.67 – much too low to be useful. ITER is aiming for a gain of 10. More recent experiments in Korea (KSTAR) and China (EAST) have shown that fusion conditions (100 million degrees) can be maintained for much longer – 1,000 seconds.

The current fusion development strategy has three stages:

  • JET in Europe and related machines such as TFTR/Alcator-C/NSTX in the USA, KSTAR in Korea & EAST in China – all tokamaks, but all too small to be self-sustaining;
  • ITER being built in France, to start operating in 2027 – producing 500MW of power for 100 seconds and a power gain of 10 – perhaps by 2035 with its first D-T active plasmas;
  • DEMO the follow-on power plant – in the 2040s using the physics, magnet technology and materials of ITER together with the systems for a power plant: making tritium and turning fusion energy into sensible heat in the blanket that surrounds the reactor and then converting this energy into electricity

Commercialisation is about how to turn fusion from large, state-of-the-art physics experiments into practical, large-scale and economical power plants.

Fusion from tokamaks such as ITER is the main line of development. Nevertheless, there are many other ideas and concepts, but these seem, to the fusion community, to be further from fruition and would need more work to become sources of electricity.Assuming that ITER is successful and it proves the physics of tokamaks, the focus will be on DEMO, the precursor to commercial fusion plant designs that can be replicated around the world.At this early stage, there are many variants and designs of DEMO that are modelled with whole system design codes: such as ARIES in the USA and PROCESS in Europe.

Key Considerations In The Commercialisation Process

The questions for commercialisation include: what are the practicalities of fusion power plants? And what are the economics of such devices?

First, we must recognise that fusion economics are quite uncertain because useful fusion is yet to be demonstrated and all the current devices are experimental ‘start-of-the art’. Also, there are very few economic studies of fusion power plants. Nevertheless, we can see the main issues of competitiveness. In 2040 and beyond, energy will be zero-carbon and largely renewable. System costs that include the cost of production, distribution and back-up will be in the range £60+/MWh.

Capital costs of DEMO-like power plant available in the 1940s are high – £8,000/kWe for an nth of a kind (NOAK) power plant (which is similar maturity to Hinkley Point) with costs being dominated by magnet and vessel costs that are about 50% of the total. Costs could be reduced to just less than £6,000/kWe for production of the 10th unit. Energy costs are also high (£150/MWh) even for mature design using this early technology.

Why is this? Firstly, power availability is low because of both the pulsed power mode of operating tokamaks and also the need to shut the system down and replace vessel and blanket components every few years. Secondly, overall power plant efficiency is low because of the low- temperature power cycle. Also, the high power required to drive the plasma and both the magnets and the cooling systems is all reducing the power cycle efficiency.

There are near-term production engineering ways of reducing cost and longer-term more advanced technologies, available perhaps in the 2050s, 10 years after the first DEMO, that could address the energy cost issues – improved plasma physics allowing steady-state operation and better materials that both permit longer periods between maintenance and higher cycle efficiency. These more advanced designs with repeated production of standard units could achieve both competitive capital costs – £4,000/kWe – and energy costs – £70-80/MWh (with 7% financing).

Frustration with the long timescales of fusion and the drive of private investment is behind alternative fusion strategies based on tokamaks. These aim to build fusion power plants in the early 2030s by utilising spherical designs – the shape of an apple – and high-temperature superconductors that provide higher magnetic pressures, leading to smaller sizes and hence lower capital costs. ARC from MIT and Commonwealth Fusion, Tokamak Energy and perhaps also Culham with STEP, are examples of these different strategies. However, these will need the same advanced material vessels and blankets as the larger machines to be competitive – technologies that might not be available before 2050.

What Happens Next?

The prospects for fusion are exciting, spurred on by the global need for clean energy, by records being broken in fusion, by the construction of ITER and by the new privately funded projects. The UK has strong credentials and skills in both fusion physics and systems design, which is making it a hub for fusion.

The question now is: “Can the UK build the supply chain as well as the technology to become a leader in commercial fusion power by 2040?”

Tokamak Energy, General Fusion and UKAEA Culham are all investing hundreds of millions of pounds in new experiments and in planning fusion power plants in the UK. These investments speak volumes about the possibility for UK to lead in fusion – as will the higher power fusion burns in JET with a deuterium-tritium mixture, planned for the next few years.

Tony Roulstone stablished and teaches on the Nuclear Energy Masters programme in the Department of engineering at the University of Cambridge