View source for DEMOnstration Power Plant

{{Short description|Planned fusion facility}}
{{Other uses of|DEMO|Demo (disambiguation){{!}}Demo}}
{{Use dmy dates|date=July 2020}}
[[File:EUROfusion schematic diagram of fusion power plant.jpg|thumb|Artist's concept of DEMO connected to the power grid]]
'''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 [[Energy return on investment|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.<ref>{{Cite web|url=https://www.iaea.org/newscenter/news/charting-the-international-roadmap-to-a-demonstration-fusion-power-plant|title = Charting the International Roadmap to a Demonstration Fusion Power Plant|date = 11 May 2018}}</ref><ref name=":1">{{Cite book|last=(U.S.)|first=National Academies of Sciences, Engineering, and Medicine|url=http://worldcat.org/oclc/1237825246|title=Bringing fusion to the U.S. grid.|date=17 November 2021|publisher=National Academies Press |isbn=978-0-309-68538-2|oclc=1237825246}}</ref>

Plans for DEMO-class reactors are intended to build upon the [[ITER]] experimental nuclear fusion reactor.<ref name=":2">{{Cite web|date=2021-05-06|title=Demonstration fusion plants|url=https://www.iaea.org/fusion-energy/demonstration-fusion-plants|access-date=2021-05-28|website=www.iaea.org|language=en}}</ref><ref>{{Cite web|date=2021-05-13|title=ITER: The World's Largest Fusion Experiment|url=https://www.iaea.org/fusion-energy/iter-the-worlds-largest-fusion-experiment|access-date=2021-05-28|website=www.iaea.org|language=en}}</ref>

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 [[gigawatt]]s) 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.<ref name="Fusion for Energy">{{cite web |website=Fusion for Energy |title=Demonstration Fusion Reactors|publisher=European Joint Undertaking for ITER and the Development of Fusion Energy |url=http://fusionforenergy.europa.eu/3_4_demo_en.htm |access-date=5 February 2011 |archive-url=https://web.archive.org/web/20070708082042/http://www.fusionforenergy.europa.eu/3_4_demo_en.htm |archive-date=8 July 2007 }}</ref> 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.<ref>{{Cite journal|last1=Ciattaglia|first1=Sergio|last2=Falvo|first2=Maria Carmen|last3=Lampasi|first3=Alessandro|last4=Proietti Cosimi|first4=Matteo|date=2020-05-01|title=Energy Analysis for the Connection of the Nuclear Reactor DEMO to the European Electrical Grid|journal=Energies|volume=13|issue=9|pages=2157|doi=10.3390/en13092157|issn=1996-1073|doi-access=free|hdl=11573/1394965|hdl-access=free}}</ref><sup>:5</sup>

{| class ="wikitable" style="text-align:center" 
|-
! Project !! Injected Thermal Input !! Gross Thermal Output !! [[Fusion energy gain factor|Q plasma value]]
|-
| '''[[Joint European Torus|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#Measurement|linear]] dimensions about
15% larger than ITER, and a [[Plasma (physics)|plasma]] density about 30% greater than ITER. According to timeline from [[EUROfusion]], operation is planned to begin in 2051.<ref>{{Cite web |url=https://www.euro-fusion.org/fileadmin/user_upload/EUROfusion/Documents/2018_Research_roadmap_long_version_01.pdf |title=2018 Research roadmap |access-date=29 May 2021 |archive-date=21 January 2022 |archive-url=https://web.archive.org/web/20220121082514/http://www.euro-fusion.org/fileadmin/user_upload/EUROfusion/Documents/2018_Research_roadmap_long_version_01.pdf |url-status=dead }}</ref>

It is estimated that subsequent commercial fusion reactors could be built for about a quarter of the cost of DEMO.<ref name="ITERorg">{{cite web |website=The ITER Project |title=Beyond ITER|publisher=Information Services, Princeton Plasma Physics Laboratory |url=http://www.iter.org/Future-beyond.htm|archive-url=https://web.archive.org/web/20061107220145/http://www.iter.org/Future-beyond.htm |archive-date=7 November 2006 }}</ref><ref name="EFDA_Activities">{{cite web|website=[[European Fusion Development Agreement|EFDA]] |title=Overview of EFDA Activities |publisher=[[European Fusion Development Agreement]] |url=http://www.efda.org/about_efda/downloads/EFDAoverview.ppt |archive-url=https://web.archive.org/web/20061001123645/http://www.efda.org/about_efda/downloads/EFDAoverview.ppt |archive-date=1 October 2006 |url-status=dead}}</ref> 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,<ref>{{Cite journal|last=Cardozo|first=N. J. Lopes|date=2019-02-04|title=Economic aspects of the deployment of fusion energy: the valley of death and the innovation cycle|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=377|issue=2141|pages=20170444|doi=10.1098/rsta.2017.0444|pmid=30967058|bibcode=2019RSPTA.37770444C|issn=1364-503X|doi-access=free|url=https://pure.tue.nl/ws/files/120645046/rsta.2017.0444.pdf}}</ref> as DEMO tokamaks will need to develop new supply chains<ref>{{Cite journal|last1=Entler|first1=Slavomir|last2=Horacek|first2=Jan|last3=Dlouhy|first3=Tomas|last4=Dostal|first4=Vaclav|date=2018|title=Approximation of the economy of fusion energy|journal=Energy|volume=152|pages=489–497|doi=10.1016/j.energy.2018.03.130|issn=0360-5442|doi-access=free|bibcode=2018Ene...152..489E }}</ref> and are labor intensive.<ref>{{Cite journal|last1=Banacloche|first1=Santacruz|last2=Gamarra|first2=Ana R.|last3=Lechon|first3=Yolanda|last4=Bustreo|first4=Chiara|date=2020-10-15|title=Socioeconomic and environmental impacts of bringing the sun to earth: A sustainability analysis of a fusion power plant deployment|url=https://www.sciencedirect.com/science/article/pii/S0360544220315681|journal=Energy|language=en|volume=209|pages=118460|doi=10.1016/j.energy.2020.118460|bibcode=2020Ene...20918460B |s2cid=224952718|issn=0360-5442|url-access=subscription}}</ref>

==DEMO's place in the development of fusion power==
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".<ref>{{Cite book|last=National Academies of Sciences, Engineering, and Medicine (U.S.). Committee on a Strategic Plan for U.S. Burning Plasma Research. National Academies of Sciences, Engineering, and Medicine (U.S.). Board on Physics and Astronomy. National Academies of Sciences, Engineering, and Medicine (U.S.). Division on Engineering and Physical Sciences.|title=Final report of the Committee on a Strategic Plan for U. S. Burning Plasma Research|publisher=The National Academies Press|year=2019|isbn=978-0-309-48743-6|location=The National Academies Press|pages=12|oclc=1107989881}}</ref> Approximately two dozen private-sector companies are now aiming to develop their own fusion reactors within the DEMO roadmap timetable.<ref>{{Cite news|url=https://www.bloomberg.com/news/features/2019-09-28/startups-take-aim-at-nuclear-fusion-energy-s-biggest-challenge|title=Nuclear Fusion Could Rescue the Planet From Climate Catastrophe|last1=Asmundsson|first1=Jon|last2=Wade|first2=Will|date=28 September 2019|newspaper=Bloomberg.com}}</ref><ref>{{Cite news|last=Michaels|first=Daniel|url=https://www.wsj.com/articles/fusion-startups-step-in-to-realize-decades-old-clean-power-dream-11581001383|title=Fusion Startups Step in to Realize Decades-Old Clean Power Dream|date=2020-02-06|work=The Wall Street Journal|access-date=2020-02-24|language=en-US|issn=0099-9660}}</ref> The US appears to be working towards one or more national DEMO-class fusion power plants on a cost-sharing basis.<ref name=":1" /><ref>{{Cite book|title=Community Plan for Fusion Energy and Discovery Plasma Sciences|publisher=Department of Energy|year=2020|location=Washington, D.C.|arxiv=2011.04806|last1=Baalrud|first1=Scott|last2=Ferraro|first2=Nathaniel|last3=Garrison|first3=Lauren|last4=Howard|first4=Nathan|last5=Kuranz|first5=Carolyn|author5-link=Carolyn Kuranz|last6=Sarff|first6=John|last7=Solomon|first7=Wayne}}</ref><ref>{{Cite journal|last1=Carayannis|first1=Elias G.|last2=Draper|first2=John|last3=Bhaneja|first3=Balwant|date=2020-10-02|title=Towards Fusion Energy in the Industry 5.0 and Society 5.0 Context: Call for a Global Commission for Urgent Action on Fusion Energy|journal=Journal of the Knowledge Economy|volume=12|issue=4|pages=1891–1904|doi=10.1007/s13132-020-00695-5|issn=1868-7865|doi-access=free|pmc=7529587}}</ref>

The 3 October 2019 UK Atomic Energy announcement of its [[Spherical Tokamak for Energy Production]] (STEP)<ref>{{Cite web|url=https://ccfe.ukaea.uk/uk-to-take-a-big-step-to-fusion-electricity/|title=UK to take a big 'STEP' to fusion electricity|last=Holloway|first=Nick|date=2019-10-03|website=Culham Centre for Fusion Energy|language=en-GB|access-date=2020-02-24}}</ref> grid-connected reactor for 2040 suggests a combined DEMO/PROTO phase machine apparently to be designed to [[Leapfrogging|leapfrog]] the ITER timetable.<ref>{{Cite journal|last=Gibney|first=Elizabeth|date=2019-10-11|title=UK hatches plan to build world's first fusion power plant|url=http://www.nature.com/articles/d41586-019-03039-9|journal=Nature|language=en|pages=d41586–019–03039-9|doi=10.1038/d41586-019-03039-9|pmid=33037417|s2cid=208833905|issn=0028-0836|url-access=subscription}}</ref> China's proposed [[China Fusion Engineering Test Reactor|CFETR]] machine, a grid-connected gigawatt-generating reactor, overlaps the DEMO timetable.<ref>{{Cite journal|last1=Liu|first1=Xiaogang|last2=Wang|first2=Zhaoliang|last3=Ren|first3=Yong|last4=Li|first4=Junjun|last5=Yin|first5=Dapeng|last6=Li|first6=Lei|last7=Gao|first7=Xiang|last8=Wu|first8=Yu|date=2018-01-01|title=Mechanical performance evaluation of the CFETR central solenoid model coil design|url=http://stacks.iop.org/0029-5515/58/i=1/a=016035?key=crossref.4309661f87883f6f311d28b2f2f8f627|journal=Nuclear Fusion|volume=58|issue=1|pages=016035|doi=10.1088/1741-4326/aa9866|bibcode=2018NucFu..58a6035L|issn=0029-5515|doi-access=free}}</ref><ref>{{cite web|last1=Li|first1=Jiangang|author-link=Li Jiangang|title=Closing gaps to CFETR Readiness|url=http://www-naweb.iaea.org/napc/physics/meetings/TM49530/website/talks/May%2012%20Sessions/Li_J.pdf|publisher=Institute of Plasma Physics, CAS|access-date=30 May 2018|location=IAEA TCM 3rd DEMO workshop, Hefei, China|date=11-14 May 2015|archive-date=14 December 2018|archive-url=https://web.archive.org/web/20181214070434/http://www-naweb.iaea.org/napc/physics/meetings/TM49530/website/talks/May%2012%20Sessions/Li_J.pdf|url-status=dead}}</ref> Japan also has plans for a DEMO reactor, the JA-DEMO, via its upgraded [[JT-60]],<ref>{{Citation|last=Goto|first=Takuya|title=DEMO design activities and helical initiatives in Japan|date=2020|url=http://dx.doi.org/10.1088/978-0-7503-2719-0ch9|work=Commercialising Fusion Energy|publisher=IOP Publishing|doi=10.1088/978-0-7503-2719-0ch9|isbn=978-0-7503-2719-0|s2cid=234531080|access-date=2021-12-17|url-access=subscription}}</ref><ref>{{Cite journal|last1=Tobita|first1=Kenji|last2=Hiwatari|first2=Ryoji|last3=Sakamoto|first3=Yoshiteru|last4=Someya|first4=Youji|last5=Asakura|first5=Nobuyuki|last6=Utoh|first6=Hiroyasu|last7=Miyoshi|first7=Yuya|last8=Tokunaga|first8=Shinsuke|last9=Homma|first9=Yuki|last10=Kakudate|first10=Satoshi|last11=Nakajima|first11=Noriyoshi|date=2019-05-07|title=Japan's Efforts to Develop the Concept of JA DEMO During the Past Decade|url=https://repo.qst.go.jp/?action=repository_action_common_download&item_id=76084&item_no=1&attribute_id=22&file_no=2|journal=Fusion Science and Technology|volume=75|issue=5|pages=372–383|doi=10.1080/15361055.2019.1600931|bibcode=2019FuST...75..372T |s2cid=164357381|issn=1536-1055|url-access=|url-status=|archive-url=|archive-date=|doi-access=free}}</ref> as does South Korea (K-DEMO).<ref>{{Cite journal|last1=Park|first1=H.K.|last2=Choi|first2=M.J.|last3=Hong|first3=S.H.|last4=In|first4=Y.|last5=Jeon|first5=Y.M.|last6=Ko|first6=J.S.|last7=Ko|first7=W.H.|last8=Kwak|first8=J.G.|last9=Kwon|first9=J.M.|last10=Lee|first10=J.|last11=Lee|first11=J.H.|date=2019-07-31|title=Overview of KSTAR research progress and future plans toward ITER and K-DEMO|url=http://dx.doi.org/10.1088/1741-4326/ab20e2|journal=Nuclear Fusion|volume=59|issue=11|pages=112020|doi=10.1088/1741-4326/ab20e2|bibcode=2019NucFu..59k2020P|s2cid=164484142|issn=0029-5515|url-access=subscription}}</ref>

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.<ref>{{Cite web|last=Vries|first=Gieljan de|title=Expert panel approves next DEMO design phase|url=https://www.euro-fusion.org/news/2020/december/expert-panel-approves-next-demo-design-phase/|access-date=2021-02-16|website=www.euro-fusion.org|date=15 December 2020 |language=en}}</ref>

In June 2021, General Fusion announced it would accept the UK government's offer to host the world's first substantial [[Public–private partnership|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.<ref>{{Cite web|date=2021-06-16|title=A Historic Decision: To Demonstrate Practical Fusion at Culham|url=https://generalfusion.com/2021/06/a-historic-decision-to-demonstrate-practical-fusion-at-culham/|access-date=2021-06-18|website=General Fusion|language=en-US}}</ref>

== History of the concept ==
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]].<ref>{{Cite book|last=Stacey|first=W.M.|url=https://www.worldcat.org/oclc/840282564|title=Advances in Nuclear Science and Technology|date=1983|publisher=Springer US|others=Martin Becker|isbn=978-1-4613-3757-7|location=Boston, MA|pages=200|oclc=840282564}}</ref>

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."<ref>{{Cite book|last=IAEA|url=https://www.iaea.org/publications/696/fusion-reactor-critical-issues-reports-of-four-intor-related-meetings|title=Fusion Reactor Critical Issues (Reports of Four INTOR-related Meetings)|publisher=IAEA|year=1987|location=Vienna|pages=127}}</ref>

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.<ref>{{Cite book|last=IAEA|url=https://www.iaea.org/publications/696/fusion-reactor-critical-issues-reports-of-four-intor-related-meetings|title=Fusion Reactor Critical Issues (Reports of Four INTOR-related Meetings)|publisher=IAEA|year=1987|location=Vienna|pages=132}}</ref>

==Timeline==

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]]:<ref name="ITERorg"/>
*Conceptual design was to be completed in 2017
*Engineering design is to be complete by 2024 (after input from ITER D-T tests, and data from [[IFMIF]] - both delayed {{As of|2016|lc=y}})
*The first construction phase is to last from 2024 to 2033
*The first phase of operation is to last from 2033 to 2038
*The station is then to be expanded and updated (e.g. with phase 2 blanket design)
*The second phase of operation is to start in 2040

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.<ref name=EFDA-roadmap-2012>[https://www.euro-fusion.org/wpcms/wp-content/uploads/2013/01/JG12.356-web.pdf Fusion Electricity - A roadmap to the realisation of fusion energy] {{Webarchive|url=https://web.archive.org/web/20170530221846/https://www.euro-fusion.org/wpcms/wp-content/uploads/2013/01/JG12.356-web.pdf |date=30 May 2017 }} EFDA 2012 - 8 missions, ITER, DEMO, project plan with dependencies, ...</ref>
* Conceptual design to be complete in 2020<ref name=EFDA-roadmap-2012/>{{rp|63}}
* Engineering design complete, and decision to build, in 2030
* Construction from 2031 to 2043
* Operation from 2044, Electricity generation demonstration 2048

This 2012 roadmap was intended to be updated in 2015 and 2019.<ref name=EFDA-roadmap-2012/>{{rp|49}} The EFDA was superseded by [[EUROfusion]] in 2013. The roadmap was subsequently updated in 2018.<ref name=":0">{{Cite web|url=https://www.euro-fusion.org/eurofusion/roadmap/|title=Roadmap|last=EUROfusion|website=www.euro-fusion.org|language=en|access-date=2019-03-27|archive-url=https://web.archive.org/web/20190212202505/https://www.euro-fusion.org/eurofusion/roadmap/|archive-date=12 February 2019|url-status=dead}}</ref>
* Conceptual design to be complete before 2030
* Engineering design 2030-2040
* Construction from 2040

This would imply operations commencing sometime in the 2050s.

==Technical considerations==
{{See also|Nuclear fusion|Fusion power}}
[[File:Deuterium-tritium fusion.svg|thumb|250px|The [[deuterium]]-[[tritium]] (D-T) fusion reaction is considered the most promising for producing [[fusion power]].]]
[[Image:DEMO power plant schematic.jpg|thumb|400px|Schematic of a DEMO nuclear fusion power plant]]
When [[deuterium]] and [[tritium]] fuse, the two [[atomic nucleus|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]].
:{{nuclide|Hydrogen|2}} + {{nuclide|Hydrogen|3}} → {{nuclide|Helium}} + {{SubatomicParticle|10neutron}} + 17.6 MeV
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.

*The activation energy for fusion is very large because the [[proton]]s in each nucleus strongly repel one another; they are both positively [[Elementary charge|charged]]. In order to fuse, the nuclei must be within 1 [[femtometre]] (1 × 10<sup>−15</sup> metres) of each other, where quantum-tunnelling effects permit the parent nuclei to fuse together into the resonant state. The principle is to form a quasi-Maxwellian distribution for the deuterons and the tritons, at very high temperatures, where the nuclei in the tail of the Maxwellian undergo fusion, while the continuous elastic collisions among the other nuclei will not alter the state of the plasma.
*DEMO, a [[Tokamak]] reactor, requires both dense plasma and high temperatures for the fusion reaction to be sustained.
*High [[temperatures]] give the nuclei enough energy to overcome their [[electrostatic repulsion]]. This requires temperatures in the region of 100[[Kelvin#Derived units and SI multiples|MK]], and is achieved using energy from various sources, including [[Ohmic heating]] (from electric currents induced in the plasma), [[microwaves]], [[ion]] beams, or neutral beam injection.
*Containment vessels melt at these temperatures, so the [[Plasma (physics)|plasma]] is to be kept away from the walls using [[magnetic confinement]].

Once fusion has begun, [[Neutron radiation|high-energy neutrons]] at about 160[[Kelvin#Derived units and SI multiples|GK]] 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 Tokamak containment vessel will have a lining composed of ceramic or composite tiles containing tubes in which warm liquid [[lithium]] metal will flow, cooling the lining.
*Lithium readily absorbs high-speed neutrons to form helium and tritium, becoming hot in the process.
*This increase in temperature is passed on to another (intermediate) coolant, possibly (pressurized) liquid [[water]] in a sealed, pressurized pipe. Lithium (especially when molten) reacts violently with water, even the humidity in the air, and the moisture in other substances, releasing hydrogen gas, which may catch fire explosively.
*Heat from the intermediate coolant will be used to boil water in a [[heat exchanger]].
*Steam from the heat exchanger will be used to drive turbines and generators, to create [[electric current]].
*Waste heat energy in excess of the generated electrical energy is dumped into the environment.
*Helium byproduct is the "ash" of this fusion, and will not be allowed to accumulate too much in the plasma.
*Carefully measured amounts of deuterium and tritium are added back into the plasma and heated.
*The lithium is processed to remove the helium and tritium, with the balance recycled to collect more heat and neutrons. Only a tiny amount of lithium is consumed.

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.<ref>{{Cite journal|last1=Kemp|first1=R.|last2=Wenninger|first2=R.|last3=Federici|first3=G.|last4=Reimerdes|first4=H.|last5=Ambrosino|first5=R.|last6=Brown|first6=R.|last7=Coleman|first7=M.|date=2018|title=Exploring a broad spectrum of design options for DEMO|url=http://dx.doi.org/10.1016/j.fusengdes.2018.04.049|journal=Fusion Engineering and Design|volume=136|pages=970–974|doi=10.1016/j.fusengdes.2018.04.049|bibcode=2018FusED.136..970K |issn=0920-3796|hdl=21.11116/0000-0002-BCCB-6|s2cid=125644486|hdl-access=free}}</ref><ref>{{Cite journal|last1=Taylor|first1=Neill|last2=Ciattaglia|first2=Sergio|last3=Coombs|first3=Dave|last4=Jin|first4=Xue Zhou|last5=Johnston|first5=Jane|last6=Liger|first6=Karine|last7=Mazzini|first7=Guido|last8=Mora|first8=Juan Carlos|last9=Pinna|first9=Tonio|last10=Porfiri|first10=Maria Teresa|last11=Urbonavicius|first11=Egidijus|date=2019|title=Safety and environment studies for a European DEMO design concept|url=http://dx.doi.org/10.1016/j.fusengdes.2018.11.049|journal=Fusion Engineering and Design|volume=146|pages=111–114|doi=10.1016/j.fusengdes.2018.11.049|bibcode=2019FusED.146..111T |s2cid=126327529|issn=0920-3796|url-access=subscription}}</ref><ref>{{Cite journal|last=Okano|first=Kunihiko|date=2018-06-15|title=Review of Strategy Toward DEMO in Japan and Required Innovations|url=http://dx.doi.org/10.1007/s10894-018-0169-y|journal=Journal of Fusion Energy|volume=38|issue=1|pages=138–146|doi=10.1007/s10894-018-0169-y|s2cid=125600515|issn=0164-0313|url-access=subscription}}</ref>

==Conceptual design==

All aspects of DEMO were discussed in detail in a 2009 document by the Euratom-UKAEA Fusion Association.<ref name=Stork2009>[http://fire.pppl.gov/eu_demo_Stork_FZK%20.pdf DEMO and the Route to Fusion Power, Derek Stork, Euratom-UKAEA Fusion Association, September 2009]</ref>
Four conceptual designs PPCS A, B, C, D were studied. Challenges identified included:<ref name=Stork2009/>
* structural materials resistant to the high neutron flux
* [[High-temperature superconductivity|high-temperature superconductors]], to avoid the need for large amounts of [[Helium cryogenics|helium for cooling]], that would challenge world helium reserves 
* need for high efficiency in the heating and current drive systems.

In the 2012 timeline, the conceptual design should be completed in 2020.

== Radioactive waste ==
While fusion reactors like ITER and DEMO will produce neither [[transuranic]] nor [[fission product]] wastes, which together make up the bulk of the [[nuclear waste]]s produced by [[fission reactor]]s, some of the components of the ITER and DEMO reactors will become radioactive due to [[neutron activation|neutrons impinging upon them]]. It is hoped that [[plasma facing material]]s will be developed so that wastes produced in this way will have much shorter [[Half life|half lives]] than the waste from fission reactors, with wastes remaining harmful for less than one century.<ref>{{cite journal |last1=Someya |first1=Youji |last2=Tobita |first2=Kenji |last3=Utoh |first3=Hiroyasu |last4=Asakura |first4=Nobuyuki |last5=Sakamoto |first5=Yoshiteru |last6=Hoshino |first6=Kazuo |last7=Nakamura |first7=Makoto |last8=Tokunaga |first8=Shinsuke |title=Management Strategy for Radioactive Waste in the Fusion DEMO Reactor |journal=Fusion Science and Technology |date=2015 |volume=68 |issue=2 |pages=423–427 |doi=10.13182/FST15-101 |bibcode=2015FuST...68..423S |s2cid=117010543 | access-date = 2023-01-04 |url = https://www.tandfonline.com/doi/abs/10.13182/FST15-101|url-access=subscription }}</ref> Development of these materials is the prime purpose of the [[International Fusion Materials Irradiation Facility]]. The process of [[Tritium#Production|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 reactor|CANDU]] fission reactors,<ref>{{cite journal|doi=10.1016/j.fusengdes.2018.04.090|title=Tritium supply and use: A key issue for the development of nuclear fusion energy|year=2018|last1=Pearson|first1=Richard J.|last2=Antoniazzi|first2=Armando B.|last3=Nuttall|first3=William J.|journal=Fusion Engineering and Design|volume=136|pages=1140–1148|bibcode=2018FusED.136.1140P |s2cid=53560490|url=http://oro.open.ac.uk/55293/1/1-s2.0-S092037961830379X-main.pdf}}</ref> late-stage ITER (to some extent) and DEMO should be able to produce its own tritium thanks to [[Breeding blanket|tritium breeding]],<ref>{{cite journal |last1=Day |first1=Christian |title=The pre-concept design of the DEMO tritium, matter injection and vacuum systems |journal=Fusion Engineering and Design |date=June 2022 |volume=179 |page=113139 |doi=10.1016/j.fusengdes.2022.113139 |s2cid=248369849 |url=https://publikationen.bibliothek.kit.edu/1000146504/148785449 |access-date=2023-01-04|url-access= |url-status= |archive-url= |archive-date= |doi-access=free |bibcode=2022FusED.17913139D }}</ref> dispensing with the fission reactor currently used for this purpose.

== PROTO ==
{{Main|PROTO (fusion reactor)}}
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.

== See also ==
*[[China Fusion Engineering Test Reactor]]
*[[COLEX process]]
*[[ITER]]
*[[PROTO (fusion reactor)|PROTO]]
*[[Spherical Tokamak for Energy Production]]

==References==
{{reflist|30em}}

{{fusion experiments}}

[[Category:Tokamaks]]
[[Category:Proposed nuclear power stations]]
[[Category:Proposed fusion reactors]]
[[Category:ITER]]