21st century fusion: space and time

17 November 2016

Nuclear fusion has, for many years, been the next big thing for power generation. However Dr David Kingham, CEO at Tokamak Energy, reveals it’s inching closer with significant technological developments.

Nuclear fusion is the creative process of the universe. All matter, besides hydrogen and a smattering of helium, was created in the fusion furnaces within stars as small atomic nuclei joined together to make larger ones. This reaction releases huge amounts of energy – about ten million times as much by weight as the chemical reaction
of fossils fuels, and all without any harmful byproducts. One can see why it is hailed as the energy of the future, the power source that will right the wrongs of a fossil fuel-reliant past and present. But it is not easy to achieve.

The established method for this reaction on Earth is to combine deuterium and tritium – two isotopes of hydrogen – to make helium and a neutron. In order to do this, fusion reactors must recreate the conditions found in stars, where fusion naturally occurs. This means confining the fuel and heating it to temperatures of 100 million degrees, which creates a super-hot 'plasma' within which the nuclei fuse. The neutrons generated by this reaction are not confined by the magnetic fields that confine the fuel and so fly out of the vessel to be captured in a “blanket”. Electricity can be generated by capturing the energy of these neutrons.

The scientific and engineering challenges behind putting a star in a box are huge. Without proper confinement of the plasma, the reactor walls would get hot and the fusion fuel would get cold. The reaction would stop. The hot, electrically charged plasma must be isolated from the walls of the reactor using magnetic fields. The most advanced machine for this purpose is the ‘tokamak’.

JET is the best-performing tokamak in the world. In 1997 it produced 16MW of fusion power with 24MW input – i.e. 65% as much energy out as was put in. It holds the world record for total fusion power produced and for getting closest to energy breakeven. JET was the pinnacle of rapid progress in fusion research that had begun in the 1960s. The temperature, density and energy confinement time, which indicates fusion performance, was increasing at a faster and faster rate up until the JET experiments.

Since then progress has stalled. Experiments have been built and much has been learned, but progress towards energy breakeven has slowed. It has yet to be reached almost 20 years after those momentous JET experiments.

The traditional development trajectory has produced consecutively larger designs, culminating in the ITER experiment currently under construction in the south of France. This will be over 30m tall and weigh about 23,000 tonnes. The demonstration reactor that follows, dubbed DEMO, will likely be bigger again. 

When ITER was being designed in the 1990s it was believed that the only feasible way to increase fusion power was to
increase machine size. However, the size and complexity of ITER has led to very slow progress, with first plasma now set for 2025 (or later) and the first use of tritium fuel not expected until well into the 2030s. Moreover, DEMO is not currently intended as a prototype for a commercially viable reactor (that will follow) despite literature to suggest that DEMO could play this role. If it did it would shorten the timescale to commercial fusion power by 20 years.

The establishment fusion timeline is measured in many decades, not years. But in view of the COP21 target of keeping global temperature rises below 2°C by 2050, promising methods of reducing carbon emissions from energy generation should be prioritised as a matter of urgency.

This urgency and desire for change, combined with the sluggishness of the mainstream fusion programme (and an awareness of the inherent difficulties of such a big project as ITER), has produced a new spirit. The possibility of a smaller way to fusion has fired the imagination of inventors, innovators and now investors.

Fusion is not the only field where private funding is entering into the research domain of governments. Ventures like Virgin Galactic and SpaceX, and now the Breakthrough Energy Coalition led by Bill Gates and Mark Zuckerberg, are other examples. These large investments in new technologies and promising areas of scientific research are becoming increasingly common. As Lord Rees of Ludlow, cosmologist, astrophysicist and past President of the Royal Society, put it in 2015 “the private sector now has greater appetite for risk in scientific projects than Western governments”.

The fusion industry has benefitted hugely from this change in appetite. In the late 2000s, research from the European Commission found there was virtually no private investment in fusion technology. Nearly all money in fusion came through one single programme called EURATOM. Over the same period in the UK, average private sector expenditure on R&D was 67-69% of total R&D spending – a stark contrast to fusion. It is clear that, until recently, private industry viewed fusion as a goal nowhere near commercialisation.

This is now being corrected. In the past few years, fusion has gained the attention of high- profile technology backers such as Jeff Bezos, founder of Amazon, Paul Allen of Microsoft and Peter Thiel, co-founder of PayPal. Together they have invested many tens of millions into private fusion ventures in the US. Further investments come from a wide array of venture capital funds, sovereign wealth funds and angel investors.

Tokamak Energy has greatly benefitted from this new era of enthusiasm for fusion in the UK and elsewhere. It has raising over £10 million so far, mainly from private investors. This has enabled complex fusion engineering to be developed faster than it has for years, and has allowed Tokamak Energy to develop plans to play a leading role in the race to fusion energy.

Research into fusion began in the mid-20th century, so there is an accumulation of knowledge about how tokamaks hold plasma in strong magnetic fields. Tokamak Energy has added to this knowledge base. In 2015 and 2016 papers were published that showed, for the first time, size is not an important factor in fusion reactors. They show that a compact reactor can produce an energy gain – a game changer when you consider the grand scale of other fusion projects. One of these papers ‘On the Power and Size of Tokamak Fusion Pilot Plants and Reactors’ has gone on to have the most online downloads in the history of Nuclear Fusion journal. Establishing the science behind its reactor concept and prototypes has helped Tokamak Energy turn the pursuit of fusion energy from an unattainable dream into a series of addressable engineering challenges.

An important element of the Tokamak Energy approach is the use of second-generation “high temperature” superconductors, which will be used for the all-important magnets holding the plasma in place.

Traditional superconducting magnets need to be cooled to -269°C (4K) in order to eliminate electrical resistance within them and function effectively. The surrounding equipment required to achieve this takes up a considerable amount of space and poses a fundamental problem to reducing the size of a reactor.

All tokamaks are a ring shape (whether a wide doughnut-like ring of conventional tokamaks or a compressed cored-apple-shaped ring of spherical tokamaks) and magnets looping around the ring pass through the central core. Reducing the size of a reactor dramatically lowers the amount of space within the core, so it cannot hold a conventional superconducting magnet and the necessary systems to keep it at a super-low temperature.

Tokamak Energy has developed “high temperature” superconducting (HTS) magnets using HTS tape that has remarkably high conductivity even in exceptionally high magnetic fields. This high conductivity combined, with a higher operating temperature (which requires much less energy to keep it cool), means the magnets can fit through the centre of a smaller reactor. Thus, using private investment, Tokamak Energy has successfully overcome a key engineering problem of reducing reactor size while maintaining performance.

Regular, achievable goals and fast iterations are what is required to thrive in this new private climate. Tokamak Energy’s plan breaks down the engineering challenges into distinct steps. In doing so, finance can be raised privately to achieve each step, with success enabling further funding to be raised to tackle the next challenge.

Tokamak Energy aims to deliver a fusion power gain by 2020, first electricity by 2025 and a 100MWe power plant by 2030, though this will depend on attracting a huge amount of additional investment. But progress is good. Its third device, a high-field spherical tokamak, is already nearing completion. The company plans to build five tokamaks – the fifth being a prototype commercial reactor that can be plugged into the grid to prove the concept of compact, modular fusion power stations.

Other fusion startups also understand this need for clear, achievable targets and a reasonable pathway to an end goal.

General Fusion in Canada is using a magnetized vortex approach based on scientific theory from 30 years ago. It says
it is following “a clear and practical path” in the development of its reactor. Currently this involves developing sub-systems that will be used to operate the reactor ahead of a prototype reactor build.

Tri-Alpha Energy in California is addressing the challenge of heating up a plasma within its novel hydrogen-boron reactor, methodically scaling temperatures over the next three to four years to validate its technology.

The benefits of this smaller, iterative, faster route to success are also recognised outside the fusion industry. Nuclear fission innovators are beginning to realise the promise of small modular reactors and the benefits of faster technological development and maturation. Developer NuScale Power’s explanation is typical: it says it offers a “shorter, more predictable” construction period, which reduces financial risks and costs, while the size of its prototype reactor ensures a far less complex end product. With a smaller, more cost effective and flexible nuclear energy infrastructure on the horizon, both fusion and fission are following an established trend across the energy industry for more distributed generation.

There is latent public enthusiasm for ‘smaller’ energy generation but also for nuclear fusion as a future clean energy source. People recognise that harnessing fusion is an important challenge that we have a duty to tackle. As a scientific concept, it has grabbed the imagination since it was first identified as the source of energy in the sun. The new climate of investment and the appetite for fresh approaches brings hope for a fusion future.

The old jest is that fusion will forever be 30 years away. Tokamak Energy is working squarely on making it a reality much sooner. 

Fusion Diagrammatic layout of the third reactor being built by Tokamak Energy – the ST40
Fusion Approximate R&D investment in nuclear fusion from industry and public sectors.
Fusion Nuclear fusion is publicly financed with the EU-funds and Member States, amounting to a total of around €482 million in 2007.

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