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Patent
Tokamak Energy Ltd. | Date: 2015-04-09

An efficient compact nuclear fusion reactor for use as a neutron source or energy source includes a toroidal plasma chamber and a plasma confinement system arranged to generate a magnetic field for confining a plasma in the chamber, where the plasma confinement system is configured so that a major radius of the confined plasma is 1.5 m or less and the toroidal magnetic field is operated 5 T or less and the plasma current is 5 MA or less, yet a-particles generated are confined in the plasma.


News Article | October 23, 2015
Site: news.mit.edu

It’s an old joke that many fusion scientists have grown tired of hearing: Practical nuclear fusion power plants are just 30 years away — and always will be. But now, finally, the joke may no longer be true: Advances in magnet technology have enabled researchers at MIT to propose a new design for a practical compact tokamak fusion reactor — and it’s one that might be realized in as little as a decade, they say. The era of practical fusion power, which could offer a nearly inexhaustible energy resource, may be coming near. Using these new commercially available superconductors, rare-earth barium copper oxide (REBCO) superconducting tapes, to produce high-magnetic field coils “just ripples through the whole design,” says Dennis Whyte, a professor of Nuclear Science and Engineering and director of MIT’s Plasma Science and Fusion Center. “It changes the whole thing.” The stronger magnetic field makes it possible to produce the required magnetic confinement of the superhot plasma — that is, the working material of a fusion reaction — but in a much smaller device than those previously envisioned. The reduction in size, in turn, makes the whole system less expensive and faster to build, and also allows for some ingenious new features in the power plant design. The proposed reactor, using a tokamak (donut-shaped) geometry that is widely studied, is described in a paper in the journal Fusion Engineering and Design, co-authored by Whyte, PhD candidate Brandon Sorbom, and 11 others at MIT. The paper started as a design class taught by Whyte and became a student-led project after the class ended. The new reactor is designed for basic research on fusion and also as a potential prototype power plant that could produce significant power. The basic reactor concept and its associated elements are  based on well-tested and proven principles developed over decades of research at MIT and around the world, the team says. “The much higher magnetic field,” Sorbom says, “allows you to achieve much higher performance.” Fusion, the nuclear reaction that powers the sun, involves fusing pairs of hydrogen atoms together to form helium, accompanied by enormous releases of energy. The hard part has been confining the superhot plasma — a form of electrically charged gas —  while heating it to temperatures hotter than the cores of stars. This is where the magnetic fields are so important—they effectively trap the heat and particles in the hot center of the device. While most characteristics of a system tend to vary in proportion to changes in dimensions, the effect of changes in the magnetic field on fusion reactions is much more extreme: The achievable fusion power increases according to the fourth power of the increase in the magnetic field. Thus, doubling the field would produce a 16-fold increase in the fusion power. “Any increase in the magnetic field gives you a huge win,” Sorbom says. While the new superconductors do not produce quite a doubling of the field strength, they are strong enough to increase fusion power by about a factor of 10 compared to standard superconducting technology, Sorbom says. This dramatic improvement leads to a cascade of potential improvements in reactor design. The world’s most powerful planned fusion reactor, a huge device called ITER that is under construction in France, is expected to cost around $40 billion. Sorbom and the MIT team estimate that the new design, about half the diameter of ITER (which was designed before the new superconductors became available), would produce about the same power at a fraction of the cost and in a shorter construction time. But despite the difference in size and magnetic field strength, the proposed reactor, called ARC, is based on “exactly the same physics” as ITER, Whyte says. “We’re not extrapolating to some brand-new regime,” he adds. Another key advance in the new design is a method for removing the the fusion power core from the donut-shaped reactor without having to dismantle the entire device. That makes it especially well-suited for research aimed at further improving the system by using different materials or designs to fine-tune the performance. In addition, as with ITER, the new superconducting magnets would enable the reactor to operate in a sustained way, producing a steady power output, unlike today’s experimental reactors that can only operate for a few seconds at a time without overheating of copper coils. Another key advantage is that most of the solid blanket materials used to surround the fusion chamber in such reactors are replaced by a liquid material that can easily be circulated and replaced, eliminating the need for costly replacement procedures as the materials degrade over time. “It’s an extremely harsh environment for [solid] materials,” Whyte says, so replacing those materials with a liquid could be a major advantage. Right now, as designed, the reactor should be capable of producing about three times as much electricity as is needed to keep it running, but the design could probably be improved to increase that proportion to about five or six times, Sorbom says. So far, no fusion reactor has produced as much energy as it consumes, so this kind of net energy production would be a major breakthrough in fusion technology, the team says. The design could produce a reactor that would provide electricity to about 100,000 people, they say. Devices of a similar complexity and size have been built within about five years, they say. “Fusion energy is certain to be the most important source of electricity on earth in the 22nd century, but we need it much sooner than that to avoid catastrophic global warming,” says David Kingham, CEO of Tokamak Energy Ltd. in the UK, who was not connected with this research. “This paper shows a good way to make quicker progress,” he says. The MIT research, Kingham says, “shows that going to higher magnetic fields, an MIT speciality, can lead to much smaller (and hence cheaper and quicker-to-build) devices.” The work is of “exceptional quality,” he says; “the next step … would be to refine the design and work out more of the engineering details, but already the work should be catching the attention of policy makers, philanthropists and private investors.” The research was supported by the U.S. Department of Energy and the National Science Foundation.


Costley A.E.,Tokamak Energy Ltd | Hugill J.,Tokamak Energy Ltd | Buxton P.F.,Tokamak Energy Ltd | Buxton P.F.,University of York
Nuclear Fusion | Year: 2015

It is generally accepted that the route to fusion power involves large devices of ITER scale or larger. However, we show, contrary to expectations, that for steady state tokamaks operating at fixed fractions of the density and beta limits, the fusion gain, Qfus, depends mainly on the absolute level of the fusion power and the energy confinement, and only weakly on the device size. Our investigations are carried out using a system code and also by analytical means. Further, we show that for the two qualitatively different global scalings that have been developed to fit the data contained in the ITER ELMy H-mode database, i.e. the normally used beta-dependent IPB98y2 scaling and the alternative beta-independent scalings, the power needed for high fusion performance differs substantially, typically by factors of three to four. Taken together, these two findings imply that lower power, smaller, and hence potentially lower cost, pilot plants and reactors than currently envisaged may be possible. The main parameters of a candidate low power (∼180MW), high Qfus (∼5), relatively small (∼1.35m major radius) device are given. © 2015 IAEA, Vienna.


Chan V.S.,General Atomics | Costley A.E.,Tokamak Energy Ltd. | Wan B.N.,CAS Hefei Institutes of Physical Science | Garofalo A.M.,General Atomics | Leuer J.A.,General Atomics
Nuclear Fusion | Year: 2015

This paper presents the results of a multi-system codes benchmarking study of the recently published China Fusion Engineering Test Reactor (CFETR) pre-conceptual design (Wan et al 2014 IEEE Trans. Plasma Sci. 42 495). Two system codes, General Atomics System Code (GASC) and Tokamak Energy System Code (TESC), using different methodologies to arrive at CFETR performance parameters under the same CFETR constraints show that the correlation between the physics performance and the fusion performance is consistent, and the computed parameters are in good agreement. Optimization of the first wall surface for tritium breeding and the minimization of the machine size are highly compatible. Variations of the plasma currents and profiles lead to changes in the required normalized physics performance, however, they do not significantly affect the optimized size of the machine. GASC and TESC have also been used to explore a lower aspect ratio, larger volume plasma taking advantage of the engineering flexibility in the CFETR design. Assuming the ITER steady-state scenario physics, the larger plasma together with a moderately higher BT and Ip can result in a high gain Qfus ∼ 12, Pfus ∼ 1 GW machine approaching DEMO-like performance. It is concluded that the CFETR baseline mode can meet the minimum goal of the Fusion Nuclear Science Facility (FNSF) mission and advanced physics will enable it to address comprehensively the outstanding critical technology gaps on the path to a demonstration reactor (DEMO). Before proceeding with CFETR construction steady-state operation has to be demonstrated, further development is needed to solve the divertor heat load issue, and blankets have to be designed with tritium breeding ratio (TBR) > 1 as a target. © 2015 General Atomics.


Gryaznevich M.P.,Tokamak Energy Ltd | Gryaznevich M.P.,Imperial College London | Gryaznevich M.P.,Technical University of Denmark | Chuyanov V.A.,Tokamak Energy Ltd | And 2 more authors.
Journal of Physics: Conference Series | Year: 2015

On the path to Fusion power, the construction of ITER is on-going, however there is not much progress in performance improvements of tokamaks in the last 15 years, Fig.1. One possible reason for this stagnation is the lack of innovations in physics and technology that could be implemented with this approach in which progress is expected mainly from the increase in the size of a Fusion device. Such innovations could be easier to test and use in much smaller (and so cheaper and quicker to build) compact Fusion devices. In this paper we propose a new path to Fusion energy based on a compact high field Spherical Tokamak approach. © Published under licence by IOP Publishing Ltd.


Costley A.E.,Tokamak Energy Ltd
Nuclear Fusion | Year: 2016

The energy confinement time of tokamak plasmas scales positively with plasma size and so it is generally expected that the fusion triple product, nTτ E, will also increase with size, and this has been part of the motivation for building devices of increasing size including ITER. Here n, T, and τ E are the ion density, ion temperature and energy confinement time respectively. However, tokamak plasmas are subject to operational limits and two important limits are a density limit and a beta limit. We show that when these limits are taken into account, nTτ E becomes almost independent of size; rather it depends mainly on the fusion power, P fus. In consequence, the fusion power gain, Q fus, a parameter closely linked to nTτ E is also independent of size. Hence, P fus and Q fus, two parameters of critical importance in reactor design, are actually tightly coupled. Further, we find that nTτ E is inversely dependent on the normalised beta, β N; an unexpected result that tends to favour lower power reactors. Our findings imply that the minimum power to achieve fusion reactor conditions is driven mainly by physics considerations, especially energy confinement, while the minimum device size is driven by technology and engineering considerations. Through dedicated R&D and parallel developments in other fields, the technology and engineering aspects are evolving in a direction to make smaller devices feasible. © 2016 IAEA, Vienna.


Patent
Tokamak Energy Ltd | Date: 2014-09-10

Disclosed herein is a toroidal field coil for generating a toroidal magnetic field in a nuclear fusion reactor comprising toroidal plasma chamber having a central column, the toroidal field coil comprising a plurality of windings passing through the central column and around the outside of the plasma chamber. Each winding includes a cable comprising a plurality of stacked HTS tapes, each HTS tape including one or more layers of a high temperature superconductor material. The HTS tapes are arranged such that a face of each HTS tape is parallel to the toroidal magnetic field as the cable passes through the centre column


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Proof of Market | Award Amount: 25.00K | Year: 2011

Culham Laboratory currently leads the world in the science and technology of tokamaks and magnetic confinement fusion. This is the most promising technology for the huge, long term, challenge of producing electricity from fusion. This project aims to establish the market demand for small tokamaks. In particular we will investigate the market for a small tokamak to produce a plasma suitable initially for plasma physics research and training and for R&D on plasma processing of materials for extreme environments. Technological breakthroughs with tokamaks at Culham, linked to advances in High Temperature Superconducting (HTS) magnets by Oxford Instruments, have led to this opportunity to design and develop a small tokamak (


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Development of Prototype | Award Amount: 250.00K | Year: 2012

Fusion power has the potential to be clean, green and plentiful. It is inherently safe and carries no risks of nuclear proliferation. Projections of future world energy supply anticipate fusion power being responsible for 36% of all global electricity production by the year 2100. However, with the present R&D proposals, including the €15bn investment in the ITER tokamak in France, it is unlikely that fusion power can become an economic reality before 2050. Tokamak Solutions has built an early prototype of a small tokamak that has the potential to speed up the fusion R&D process and bring forward the time when fusion power will be available. While huge experiments such as JET at Culham and the future ITER tokamak tackle major problems in fusion R&D, small tokamaks designed and built by Tokamak Solutions can tackle many of the challenges of fusion that are amenable to rapid development with a small device. In other words, Tokamak Solutions aims to provide a research tool to allow rapid incremental innovation in fusion in a way that is complementary to, and will speed up, mainstream fusion R&D. As demand for electricity increases (at 5% per annum worldwide) and global warming concerns increase, the need for fusion energy will become more pressing. Annual global expenditure on fusion energy R&D is about £2bn. Our proof of market study has shown that every country with a serious scientific effort would want its own tokamak for fusion research with the latest magnet technology. The objective of this project is to develop and demonstrate the world’s first tokamak with all its magnets made from high temperature superconductor (HTS). We will demonstrate that this small tokamak is easy to use by students and researchers and is capable of ground-breaking research. If we can win initial orders for small tokamaks from universities and research institutes, then the opportunities to participate in larger fusion projects will open up.


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Proof of Concept | Award Amount: 100.00K | Year: 2011

The business opportunity that this project addresses has been summarised in the editorial and main feature article in The Engineer published on 11 April 2011. In the words of the Editor: “The medical industry relies on nuclear fission for the production of radioactive isotopes – which are essential for a range of scanning techniques and cancer treatments. With the experimental reactors that produce these isotopes coming to the end of their lives and plans to prolong their lives or replace them suddenly not looking so straightforward [due to events at Fukushima], there are genuine fears that we’re heading for a worldwide shortage of nuclear medicine. But where one technology falters, another spies an opportunity and [as Appendix A explains], an impending radioisotope shortage could give nuclear fusion – the energy industry’s holy grail – a more immediate opportunity to prove its worth. Indeed, nuclear medicine is just one application that could drive the development of fusion, its usefulness as a source of neutrons could also see it being used to clean up nuclear waste and even to trigger fission reactions in new, safe, hybrid fusion-fission reactors… Despite its considerable promise, the commercial case for fusion is far from certain and, in an economic climate where investment is increasingly limited to dead-certs, its progress has been stuttering at best. But by providing genuine solutions to short-term problems its credibility will be improved, funding should be more forthcoming and, perhaps most importantly, engineers will continue to advance the technology to the point where it can be used for commercial energy generation.” The opportunity is for Tokamak Solutions UK Ltd (TSUK) to be first to secure valuable IP (patents and designs), first to market with a Compact Fusion Neutron Source (CFNS) and first to form collaborative partnerships with larger businesses capable of addressing each of the major markets for a CFNS. The opportunity arises from the UK’s world lead in fusion research at Culham Centre for Fusion Energy (CCFE), TSUK’s invention of a CFNS based on a novel combination of existing technologies and recent developments in high temperature superconducting magnets. This project will set TSUK on course to seize the opportunity. The medical applications of a CFNS are of particular interest. As well as producing isotopes, our CFNS has the potential to produce neutron beams, initially for imaging research and then for clinical use. Fusion neutron beams may also be useful for neutron capture therapy (based on B, Ga and other elements) or for fast neutron therapy. Both of these therapies offer promising approaches to treatment of certain cancers. However, both are held back by the limitations of neutron sources, particularly by the lack of high flux sources suitable for a clinical environment. Appendix A, published in The Engineer on 11 April 2011, gives a good summary of our overall business proposition.

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