Spherical tokamak 'to put fusion power in grid' by 2030

30 January 2017

Experimental and theoretical research has shown 'spherical' tokamaks to be a "fast route to fusion" compared with more "conventional" tokamak devices such as Joint European Torus (JET), according to David Kingham, chief executive of Tokamak Energy.

"By pursuing this route, fusion researchers around the world, including at Tokamak Energy, are developing new materials and technologies to help us get fusion power into the grid by 2030," Kingham told a meeting held last week by the International Energy Agency (IEA) on developing fusion power. Tokamak Energy was invited as "one of the three most promising fusion concepts", along with General Fusion and Tri-Alpha Energy.

The UK's Tokamak Energy grew out of Culham Laboratory, home to JET - the world's most powerful tokamak - and the world's leading centre for magnetic fusion energy research. Tokamak Energy's technology revolves around high temperature superconducting (HTS) magnets, which allow for relatively low-power and small-size devices, but high performance and potentially widespread commercial deployment.

The world's first tokamak with exclusively HTS magnets - the ST25 HTS, Tokamak Energy's second reactor - demonstrated 29 hours continuous plasma during the Royal Society Summer Science Exhibition in London in 2015 - a world record.

"The plasma is where the fusion reaction takes place, and its stability is crucial," Kingham said.

The next reactor in construction - the ST40 - would produce plasma temperatures of 15 million degrees Celsius - hotter than the centre of the Sun - this year. The ST40 is currently being built at Tokamak Energy's facility at Milton Park in Oxfordshire.

"The ST40 is designed to achieve 100 million degrees C and get within a factor of ten of energy break-even conditions. To get even closer to break-even point, the plasma density, temperature and confinement time then need to be fine-tuned," Kingham said.

"The next step is to build a reactor that takes this knowledge and uses it to demonstrate first electricity from fusion by 2025. This will then form the basis of a power plant module that will deliver electricity into the grid by 2030," he added.

This huge challenge requires, he said, "massive investment, many important collaborations, an excellent supply chain, many dedicated and creative engineers and scientists - and, no doubt, some good luck and good management" in order to succeed.

Tokamak Energy has raised private investment of £20 million ($25 million) from Oxford Instruments, L&G Capital, the Institution of Mechanical Engineers and others. It has a "valuable dialogue", Kingham said, with Princeton Plasma Physics Laboratory on spherical tokamaks, and with the Plasma Science and Fusion Centre at MIT on HTS magnets. Both institutions are "leading laboratories that share our vision", he said.

Elsewhere private ventures can be seen "tackling challenges previously assumed to be the realm of governments" - Virgin Galactic and Space X being two examples, he said.

"Even Lord Rees of Ludlow, ex-president of the Royal Society, said in 2015 that the private sector now has greater appetite for risk in scientific projects than Western governments. This is good news for fusion, which over previous decades has become large, political and cumbersome.

"Private investment is allowing smaller, agile companies to try different approaches and make new inroads into an old problem. We are treating the pursuit of fusion energy as an engineering challenge and a business, rather than a 'big science' project," he said.

Commissioning this Spring

In an interview with World Nuclear News (WNN) on 26 January, a day after his meeting with the Paris-based IEA, Kingham said the ST40 is due to be completed and start commissioning this Spring.

"This signals a defining moment for Tokamak Energy, as the ST40 will be the most powerful compact spherical tokamak in the world that will aim to produce plasma temperatures hotter than the centre of the sun well before the end of the year," he said.

The IEA has a Fusion Power Coordinating Committee (FPCC), which provides a forum to co-ordinate international science and research with regard to fusion - device-specific research (tokamaks and alternate concepts) and cross-cutting research (materials, safety and technologies). The FPCC also oversees eight IEA Technology Collaboration Programs in fusion.

"The IEA fosters international collaboration and coordination to help close the existing gaps in physics, technology and regulation and move forward in developing the peaceful use of fusion energy," Kingham said. Its activities in this field cover, among others, plasma physics and fusion power, technologies and material, both for magnetic and inertial fusion.

Tokamak Energy is "unique among nimble, privately funded fusion energy ventures", he said, in the way that the majority of them are looking for alternative and quicker routes to fusion energy, in comparison to large publicly funded companies, which often make slow progress but do sometimes produce new scientific breakthroughs. Tokamak Energy is unique amongst privately funded fusion energy ventures, he added, as it is aiming to accelerate the development of fusion energy based on the tokamak.

Other "routes to fusion" are being taken by, for example, General Fusion and Tri-Alpha Energy, he noted. General Fusion is taking the approach of Magnetised Target Fusion, with the aid of modern electronics, materials, and advances in plasma physics. Tri-Alpha Energy is utilising proprietary advanced beam-driven field reversed configuration technology to create a superheated plasma environment. Tri Alpha Energy has operated a national lab-scale machine, which in many aspects resembles a future power plant, in which hydrogen and boron would fuse generating helium and energy.

The tokamak as a class of device has had "unprecedented global support backed up by scientific consensus", Kingham said. More than 200 tokamaks have been built in laboratories worldwide, he noted, and there has been a €20 billion ($21 billion) international agreement to build Iter, a huge tokamak, in France.

The Iter fusion reactor is widely seen as being JET's successor on the route to developing commercial fusion power. Iter is currently scheduled to produce its first plasma in 2025 and start deuterium-tritium operations in 2035. Like JET, Iter will not demonstrate the use of nuclear fusion to produce electricity. That will be the objective of Iter's successor, the Demonstration Fusion Power Reactor, or DEMO, which will aim to demonstrate the continuous output of energy, supplying electricity to the grid. According to EUROfusion, DEMO is expected to follow Iter by 2050.

The most recent and largest investment Tokamak Energy has received in a single round to date was announced at the end of last year, when Legal & General Capital, British billionaire David Harding and other private individuals invested over £10 million. This was "a signal of our ambitions within the fusion energy industry and a vindication of our approach", Kingham told WNN. This investment boost brought the total investment Tokamak Energy has received to almost £20 million. Previous rounds of investment came from investors in the engineering and corporate sectors, including Oxford Instruments, the Institution of Mechanical Engineers and Rainbow Seed Fund.

Other developers, like General Fusion, Tri-Alpha Energy, Helion Energy and First Light Fusion have had recent investment rounds, he added.

Tokamak Energy was originally established in 2009, with the objective of designing and developing compact fusion reactors and small spherical tokamaks for a variety of applications. Its strategy has evolved significantly since 2012, Kingham said, and moved towards prioritising the development of a pilot plant to exceed fusion energy breakeven. The company is primarily focused on compact spherical tokamaks due to their efficiency; these devices can achieve a much higher plasma pressure for a given magnetic field than conventional tokamaks, he added.

"Today, we hold the world record for running our tokamak with magnets of high temperature superconductors for 29 hours. The previous record was five hours, indicating the progress being made at Tokamak Energy towards achieving the goal of fusion energy,” he told WNN. "We've made progress backed by scientific evidence and acknowledged by globally recognised bodies. For example, we were announced as a Technology Pioneer of the World Economic Forum in August 2015. Papers by Tokamak Energy scientists including Dr Alan Costley, occupy the top three places in the 'most read' charts of the Nuclear Fusion Journal," he added.

The "economical size" of a tokamak device is crucial, he said.

"Historically, the school of thought has been that as far as the tokamak based approach goes, the bigger the better. However, Tokamak Energy's scientifically backed approach (the use of high temperature superconducting magnets) shrinks the reactor down into a much more compact and therefore economical size, more easily rolled out on a larger scale.

"The ST40 will be the most powerful compact spherical tokamak in the world as it will aim to produce the highest temperature and pressure ever reached by a spherical tokamak. The device aims to reach plasma temperatures hotter than the centre of the sun before the end of this year. The ultimate milestone we'd like to achieve is to demonstrate that fusion temperatures of 100 million degrees can be achieved in a dense plasma in a small tokamak," he said.

The ST40 has not yet produced a plasma, but forerunner device, the ST25, achieved a maximum plasma temperature of 1 million degrees. The timeline for the ST40 is to achieve "first plasma" in March this year, to be fully commissioned over the next six months, culminating in demonstration of a 15 million degree plasma in September, he said.

JET, Iter and DEMO are all conventional, high aspect ratio, tokamaks, Kingham noted.

"JET at Culham in the UK is the basis of a centre of fusion expertise in the UK. Locating Tokamak Energy near to Culham is no mistake," he said. "The expertise fostered by JET (and other devices like START and MAST - spherical tokamaks - at Culham) has helped us to get to where we are today. Large government projects like JET and Iter further the understanding of the fusion process so that businesses such as ours can prosper and get closer to the fusion goal."

According to the World Nuclear Association, fusion power presents scientific and engineering challenges, one of which is a concern of the possible release of tritium into the environment. Asked about this, Kingham said fusion will initially use tritium and deuterium as fuel, and the tritium will be bred from lithium within the tokamak device.

"Great care will be taken to avoid any risk of leakage of tritium," he said. "In the long term we may work out how to use a deuterium-deuterium fusion process that would not require tritium."

Asked how things have changed from seeing fusion as science fiction rather than science - in the absence of definite details, such as budgets or working prototypes - Kingham said the answer lies with private ventures.

"Fusion projects in government laboratories have become increasingly expensive and slow. For example, Iter is now planning to start full power operations in 2035. However, now there is a new way forward with fusion, based on rapid development of new technologies by private ventures. Being a privately funded commercial entity with the necessary expertise and team, we feel that we can make fusion a reality and have stated a clear timeline to do so, i.e. putting fusion electricity into the grid by 2030," he said.

"What is different is our approach - we are aiming to accelerate the development of fusion energy taking the tokamak route. More specifically, we aim to do this through combining two emerging technologies: spherical tokamaks and high-temperature superconductors; and by aiming to keep our devices as small as possible."

On the relationship between the fusion and fission industries, Kingham said nuclear fission innovators have also realised the benefits of compact reactors and the benefits of faster technological development and rapid deployment they bring.

"Therefore, we do not consider the fission industry as competitors, but instead consider our relationship with them as one that is mutually beneficial, involving the exchange of ideas. There is an interesting overlap of technologies between small modular fission reactors and the equivalent small modular fusion reactors of the type we are developing.

"We are creating a way for small, modular fusion energy to become a reliable source of clean energy for the world. Our business model is based on agility and 'open innovation'," he said. "We believe that machines that are able to generate net energy gain for a sustained period need to be built; these machines must be economical to build, run and decommission."

Tokamak Energy's schedule is, he said: build a small prototype tokamak to demonstrate the concept; build a tokamak with all magnetics of high temperature superconductor (achieved in 2015); reach fusion temperatures in a compact tokamak (aiming for 100 million degrees in 2018); achieve close to energy breakeven conditions by 2019; produce electricity for the first time by 2025; put fusion electricity into the grid by 2030.

Researched and written
by World Nuclear News