DEMO, or a demonstration power plant (often stylized as DEMOnstration power plant), refers to a proposed class of nuclear fusion experimental reactors that are intended to demonstrate the net production of electric power from nuclear fusion. Most of the ITER partners have plans for their own DEMO-class reactors. With the possible exception of the EU and Japan, there are no plans for international collaboration as there was with ITER. [1] [2]
Plans for DEMO-class reactors are intended to build upon the ITER experimental nuclear fusion reactor. [3] [4]
The most well-known and documented DEMO-class reactor design is that of the European Union (EU). The following parameters have been used as a baseline for design studies: the EU DEMO should produce at least 2000 megawatts (2 gigawatts) of fusion power on a continuous basis, and it should produce 25 times as much power as required for scientific breakeven, which does not include the power required to operate the reactor. The EU DEMO design of 2 to 4 gigawatts of thermal output will be on the scale of a modern electric power station. [5] However, the nominal value of the steam turbine is 790 megawatts, which, after overcoming a 5% loss because of the coupling from the turbine to the synchronous generator, results in a nominal value for electrical power output of approximately 750 megawatts. [6] :5
Project | Injected Thermal Input | Gross Thermal Output | Q plasma value |
---|---|---|---|
JET | 24 MW | 16 MW | 0.6 |
ITER | 50 MW | 500 MW | 10 |
EU DEMO | 80 MW | 2000 MW | 25 |
To achieve its goals, if utilizing a conventional tokamak design, a DEMO reactor must have linear dimensions about 15% larger than ITER, and a plasma density about 30% greater than ITER. According to timeline from EUROfusion, operation is planned to begin in 2051. [7]
It is estimated that subsequent commercial fusion reactors could be built for about a quarter of the cost of DEMO. [8] [9] However, the ITER experience suggests that development of a multi-billion US dollar tokamak-based technology innovation cycle able to develop fusion power stations that can compete with non-fusion energy technologies is likely to encounter the "valley of death" problem in venture capital, i.e., insufficient investment to go beyond prototypes, [10] as DEMO tokamaks will need to develop new supply chains [11] and are labor intensive. [12]
The 2019 US National Academies of Sciences, Engineering, and Medicine 'Final Report of the Committee on a Strategic Plan for U. S. Burning Plasma Research' noted, "a large DEMO device no longer appears to be the best long-term goal for the U.S. program. Instead, science and technology innovations and the growing interest and potential for private-sector ventures to advance fusion energy concepts and technologies suggest that smaller, more compact facilities would better attract industrial participation and shorten the time and lower the cost of the development path to commercial fusion energy". [13] Approximately two dozen private-sector companies are now aiming to develop their own fusion reactors within the DEMO roadmap timetable. [14] [15] The US appears to be working towards one or more national DEMO-class fusion power plants on a cost-sharing basis. [2] [16] [17]
The 3 October 2019 UK Atomic Energy announcement of its Spherical Tokamak for Energy Production (STEP) [18] grid-connected reactor for 2040 suggests a combined DEMO/PROTO phase machine apparently to be designed to leapfrog the ITER timetable. [19] China's proposed CFETR machine, a grid-connected gigawatt-generating reactor, overlaps the DEMO timetable. [20] [21] Japan also has plans for a DEMO reactor, the JA-DEMO, via its upgraded JT-60, [22] [23] as does South Korea (K-DEMO). [24]
In November 2020, an independent expert panel reviewed EUROfusion's design and R&D work on the EU's DEMO, and EUROfusion confirmed it was proceeding with the next step of its Roadmap to Fusion Energy, namely the conceptual design of a DEMO in partnership with the European fusion community and industry, suggesting an EU-backed DEMO-phase machine that could formally bear the DEMO name. [25]
In June 2021, General Fusion announced it would accept the UK government's offer to host the world's first substantial public-private partnership fusion demonstration plant, at Culham Centre for Fusion Energy. The plant will be constructed from 2022 to 2025 and is intended to lead the way for commercial pilot plants in the late 2020s. The plant will be 70% of full scale and is expected to attain a stable plasma of 150 million degrees. [26]
The DEMO reactor concept goes back to the 1970s. A graph by W.M. Stacey shows that by 1979, there were completed DEMO designs by General Atomics and Oak Ridge National Laboratory. [27]
At a June 1986 meeting organized by the IAEA, participants agreed on the following, concise definition for a DEMO reactor: "The DEMO is a complete electric power station demonstrating that all technologies required for a prototype commercial reactor work reliably enough to develop sufficient confidence for such commercial reactors to be competitive with other energy sources. The DEMO does not need to be economic itself nor does it have to be full scale reactor size." [28]
The following year, an IAEA document shows design parameters for a DEMO reactor in the US by Argonne National Laboratory, a DEMO reactor in Italy called FINTOR, (Frascati, Ispra, Napoli Tokamak Reactor), a DEMO reactor at Culham (UK), and a European DEMO reactor called NET (Next European Torus). The major parameters of NET were 628 MW net electrical power and 2200 MW gross thermal power output, nearly the same as the current EU DEMO design. [29]
The EU DEMO timeline has slipped several times, following slippage in the ITER timetable. The following timetable was presented at the IAEA Fusion Energy Conference in 2004 by Christopher Llewellyn Smith: [8]
In 2012, European Fusion Development Agreement (EFDA) presented a roadmap to fusion power with a plan showing the dependencies of DEMO activities on ITER and IFMIF. [30]
This 2012 roadmap was intended to be updated in 2015 and 2019. [30] : 49 The EFDA was superseded by EUROfusion in 2013. The roadmap was subsequently updated in 2018. [31]
This would imply operations commencing sometime in the 2050s.
When deuterium and tritium fuse, the two nuclei come together to form a resonant state which splits to form in turn a helium nucleus (an alpha particle) and a high-energy neutron.
DEMO will be constructed once designs which solve the many problems of current fusion reactors are engineered. These problems include: containing the plasma fuel at high temperatures, maintaining a great enough density of reacting ions, and capturing high-energy neutrons from the reaction without melting the walls of the reactor.
Once fusion has begun, high-energy neutrons at about 160GK will flood out of the plasma along with X-rays, neither being affected by the strong magnetic fields. Since neutrons receive the majority of the energy from the fusion, they will be the reactor's main source of thermal energy output. The ultra-hot helium product at roughly 40GK will remain behind (temporarily) to heat the plasma, and must make up for all the loss mechanisms (mostly bremsstrahlung X-rays from electron deceleration) which tend to cool the plasma rather quickly.
The DEMO project is planned to build upon and improve the concepts of ITER. Since it is only proposed at this time, many of the details, including heating methods and the method for the capture of high-energy neutrons, are still undetermined. [32] [33] [34]
All aspects of DEMO were discussed in detail in a 2009 document by the Euratom-UKAEA Fusion Association. [35] Four conceptual designs PPCS A,B,C,D were studied. Challenges identified included: [35]
In the 2012 timeline, the conceptual design should be completed in 2020.
While fusion reactors like ITER and DEMO will produce neither transuranic nor fission product wastes, which together make up the bulk of the nuclear wastes produced by fission reactors, some of the components of the ITER and DEMO reactors will become radioactive due to neutrons impinging upon them. It is hoped that plasma facing materials will be developed so that wastes produced in this way will have much shorter half lives than the waste from fission reactors, with wastes remaining harmful for less than one century. [36] Development of these materials is the prime purpose of the International Fusion Materials Irradiation Facility. The process of manufacturing tritium currently comes with production of long-lived waste. However, while early-stage ITER's tritium will mainly come from the current operation of heavy-water CANDU fission reactors, [37] late-stage ITER (to some extent) and DEMO should be able to produce its own tritium thanks to tritium breeding, [38] dispensing with the fission reactor currently used for this purpose.
PROTO was a proposal for a beyond-DEMO experiment, part of the European Commission long-term strategy for research of fusion energy. PROTO would act as a prototype power station, taking in any remaining technology refinements, and demonstrating electricity generation on a commercial basis. It was only expected after DEMO, beyond 2050, and probably will not be the second part of a DEMO/PROTO experiment as it no longer appears in official documentation. [39]
A tokamak is a device which uses a powerful magnetic field generated by external magnets to confine plasma in the shape of an axially-symmetrical torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. The tokamak concept is currently one of the leading candidates for a practical fusion reactor.
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved.
This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion.
The Joint European Torus (JET) was a magnetically confined plasma physics experiment, located at Culham Centre for Fusion Energy in Oxfordshire, UK. Based on a tokamak design, the fusion research facility was a joint European project with the main purpose of opening the way to future nuclear fusion grid energy. At the time of its design JET was larger than any comparable machine.
ITER is an international nuclear fusion research and engineering megaproject aimed at creating energy through a fusion process similar to that of the Sun. Upon completion of construction of the main reactor and first plasma, planned for late 2025, it will be the world's largest magnetic confinement plasma physics experiment and the largest experimental tokamak nuclear fusion reactor. It is being built next to the Cadarache facility in southern France. ITER will be the largest of more than 100 fusion reactors built since the 1950s, with ten times the plasma volume of any other tokamak operating today.
The T-15 is a Russian nuclear fusion research reactor located at the Kurchatov Institute, which is based on the (Soviet-invented) tokamak design. It was the first industrial prototype fusion reactor to use superconducting magnets to control the plasma. These enormous superconducting magnets confined the plasma the reactor produced, but failed to sustain it for more than just a few seconds. Despite not being immediately applicable, this new technological advancement proved to the USSR that they were on the right path. In the original shape, a toroidal chamber design, it had a major radius of 2.43 m and minor radius 0.7 m.
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of controlled fusion research, along with inertial confinement fusion.
The International Fusion Materials Irradiation Facility, also known as IFMIF, is a projected material testing facility in which candidate materials for the use in an energy producing fusion reactor can be fully qualified. IFMIF will be an accelerator-driven neutron source producing a high intensity fast neutron flux with a spectrum similar to that expected at the first wall of a fusion reactor using a deuterium-lithium nuclear reaction. The IFMIF project was started in 1994 as an international scientific research program, carried out by Japan, the European Union, the United States, and Russia, and managed by the International Energy Agency. Since 2007, it has been pursued by Japan and the European Union under the Broader Approach Agreement in the field of fusion energy research, through the IFMIF/EVEDA project, which conducts engineering validation and engineering design activities for IFMIF. The construction of IFMIF is recommended in the European Roadmap for Research Infrastructures Report, which was published by the European Strategy Forum on Research Infrastructures (ESFRI).
Ignitor is the Italian name for a proposed tokamak device, developed by ENEA. The project was abandoned in 2022.
SST-1 is a plasma confinement experimental device in the Institute for Plasma Research (IPR), an autonomous research institute under Department of Atomic Energy, India. It belongs to a new generation of tokamaks with the major objective being steady state operation of an advanced configuration plasma. It has been designed as a medium-sized tokamak with superconducting magnets.
The Culham Centre for Fusion Energy (CCFE) is the UK's national laboratory for fusion research. It is located at the Culham Science Centre, near Culham, Oxfordshire, and is the site of the Joint European Torus (JET), Mega Ampere Spherical Tokamak (MAST) and the now closed Small Tight Aspect Ratio Tokamak (START).
In nuclear fusion power research, the plasma-facing material (PFM) is any material used to construct the plasma-facing components (PFC), those components exposed to the plasma within which nuclear fusion occurs, and particularly the material used for the lining the first wall or divertor region of the reactor vessel.
The ARC fusion reactor is a design for a compact fusion reactor developed by the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). ARC aims to achieve an engineering breakeven of three. The key technical innovation is to use high-temperature superconducting magnets in place of ITER's low-temperature superconducting magnets. The proposed device would be about half the diameter of the ITER reactor and cheaper to build.
The China Fusion Engineering Test Reactor, or CFETR, is a proposed tokamak fusion reactor, which uses a magnetic field in order to confine plasma and generate energy. As of 2015, tokamak devices are leading candidates for the construction of a viable and practical thermonuclear fusion reactor. These reactors may be used to generate sustainable energy whilst ensuring a low environmental impact and a smaller carbon footprint than fossil fuel-based power plants.
The tritium breeding blanket, is a key part of many proposed fusion reactor designs. It serves several purposes; primarily it is to produce further tritium fuel for the nuclear fusion reaction, which owing to the scarcity of tritium would not be available in sufficient quantities, through the reaction of neutrons with lithium in the blanket. The blanket may also act as a cooling mechanism, absorbing the energy from the neutrons produced by the reaction between deuterium and tritium ("D-T"), and further serves as shielding, preventing the high-energy neutrons from escaping to the area outside the reactor and protecting the more radiation-susceptible portions, such as ohmic or superconducting magnets, from damage.
Spherical Tokamak for Energy Production (STEP) is a spherical tokamak fusion plant concept proposed by the United Kingdom Atomic Energy Authority (UKAEA) and funded by UK government. The project is a proposed DEMO-class successor device to the ITER tokamak proof-of-concept of a fusion plant, the most advanced tokamak fusion reactor to date, which is scheduled to achieve a 'burning plasma' in 2035. STEP aims to produce net electricity from fusion on a timescale of 2040. Jacob Rees-Mogg, the UK Secretary of State for Business, Energy and Industrial Strategy, announced West Burton A power station in Nottinghamshire as its site on 3 October 2022 during the Conservative Party Conference. A coal-fired power station at the site ceased production a few days earlier. The reactor is planned to have a 100 MW electrical output and be tritium self-sufficient via fuel breeding.
Deuterium–tritium fusion is a type of nuclear fusion in which one deuterium nucleus fuses with one tritium nucleus, giving one helium nucleus, one free neutron, and 17.6 MeV of total energy coming from both the neutron and helium. It is the best known fusion reaction for fusion devices.
Ambrogio Fasoli is a researcher and professor working in the field of fusion and plasma physics. A Fellow of the American Physical Society, he is Director of the Swiss Plasma Center, located at EPFL, the Swiss Federal Institute of Technology in Lausanne, Switzerland. Since 1 January 2019, he chairs the European consortium EUROfusion, the umbrella organisation for the development of nuclear fusion power in Europe.
The history of nuclear fusion began early in the 20th century as an inquiry into how stars powered themselves and expanded to incorporate a broad inquiry into the nature of matter and energy, as potential applications expanded to include warfare, energy production and rocket propulsion.
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