DEMOnstration Power Plant

DEMO, short for demonstration power plant, is a special kind of experimental reactor designed to show that we can make electricity from a process called nuclear fusion. Nuclear fusion is the same powerful energy that powers the sun. Many countries, including the ones working on the ITER project, plan to build their own DEMO-class reactors to test this idea.

The most well-known plan comes from the European Union (EU). They want their DEMO reactor to produce at least 2000 megawatts—or 2 gigawatts—of fusion power all the time. This is enough energy to power a big city! The reactor would be about the size of a modern power station, but it needs to make much more power than it uses just to prove the technology works.

To reach these goals, a DEMO reactor would need to be a little bigger and use more material than the ITER reactor. According to plans from EUROfusion, this DEMO reactor could start working as early as 2051. After DEMO, scientists hope to build smaller, cheaper fusion power plants that could help provide clean energy for the world.

DEMO's place in the development of fusion power

The 2019 US National Academies of Sciences, Engineering, and Medicine report suggested that smaller, more compact fusion facilities might be better for attracting industry support and speeding up the path to commercial fusion energy. About two dozen private companies are now working to develop their own fusion reactors within the same time frame as DEMO plans. The US is aiming to build one or more national DEMO-class fusion power plants together with industry partners.

The UK announced plans in 2019 for a Spherical Tokamak for Energy Production reactor that could be ready by 2040, potentially moving faster than the ITER project. China’s proposed CFETR reactor and Japan’s JA-DEMO plan, using an upgraded JT-60, also aim for DEMO-level capabilities. In November 2020, EUROfusion confirmed it would move forward with designing its own DEMO reactor with European partners and industry.

In June 2021, General Fusion agreed to build the world’s first major public-private partnership fusion demonstration plant at the Culham Centre for Fusion Energy. Construction began in 2022 and is set to finish in 2025. This plant will be 70% of full size and aims to create a stable plasma at 150 million degrees, helping to prepare for commercial fusion plants in the late 2020s.

History of the concept

The idea of a DEMO reactor started in the 1970s. By 1979, scientists at General Atomics and Oak Ridge National Laboratory had already created plans for these special reactors.

In 1986, a meeting organized by the IAEA helped agree on what a DEMO reactor should be: a full power station that shows all the technologies needed for future commercial reactors work well enough. It doesn’t have to be the most economic or the biggest size itself. The next year, more designs were shared from places like the US, Italy, the UK, and Europe. One European design, called NET, was planned to produce about 628 MW of electricity and 2200 MW of heat, similar to today’s EU DEMO plans.

Timeline

The EU DEMO timeline has changed many times because of delays in the ITER project. In 2004, a plan was shared that included:

• Completing the basic design by 2017
• Finishing detailed engineering by 2024
• Starting construction from 2024 to 2033
• Beginning the first phase of operation from 2033 to 2038
• Updating the station and starting a second phase of operation in 2040

In 2012, another plan suggested:

• Completing the basic design by 2020
• Finishing engineering and deciding to build by 2030
• Building from 2031 to 2043
• Operating and showing electricity production by 2048

This plan was supposed to be updated in 2015 and 2019. In 2018, the plan was updated again to aim for completing the basic design before 2030, finishing engineering between 2030 and 2040, and starting construction from 2040, with operations beginning sometime in the 2050s.

Technical considerations

See also: Nuclear fusion and Fusion power

When deuterium and tritium join together, they create a helium nucleus and a fast-moving particle called a neutron.

²
₁H + ³
₁H → ⁴
₂He + ¹
₀n + 17.6 MeV

The DEMO reactor will be built after scientists solve problems with today’s fusion reactors. These problems include keeping the fuel very hot, keeping enough fuel close together, and catching the fast-moving neutrons without damaging the reactor.

DEMO, a kind of reactor called a Tokamak, needs very hot fuel and a lot of it to keep the fusion reaction going. The heat helps the tiny parts of the fuel get close enough to join together. Special magnetic fields keep the hot fuel away from the walls of the reactor so they don’t melt. After fusion starts, fast-moving neutrons will carry most of the energy away from the reaction. This energy will be used to make electricity. The heat from the neutrons will be used to boil water, and the steam will turn turbines to create electric current. The DEMO project will build on ideas from ITER, but many details are still being decided.

Conceptual design

In 2009, a team of scientists talked about ideas for a special kind of power plant called DEMO. They looked at four different plans, called PPCS A, B, C, and D. They needed to find strong materials that could handle lots of energy and special wires that stay cool without using too much helium. They also wanted to make sure the systems could heat and power everything well.

By 2012, they hoped to finish these ideas by the year 2020.

Radioactive waste

Fusion reactors like ITER and DEMO do not create certain types of waste that regular nuclear reactors make. However, some parts of these reactors can become radioactive because of special particles called neutrons hitting them. Scientists are working to create materials that will make this waste stop being harmful much faster—within about 100 years instead of much longer. They are testing these materials at a special facility.

Right now, making a material called tritium creates waste that lasts a long time. But in the future, DEMO should be able to make its own tritium without needing regular nuclear reactors for this.

PROTO

Main article: PROTO (fusion reactor)

PROTO was a plan for an experiment that would come after DEMO. It was part of the European Commission long-term strategy for studying fusion energy. PROTO would act like a model power station, testing any last changes to the technology and showing how electricity could be made in a commercial way. This was expected to happen after DEMO, sometime after the year 2050. However, PROTO is no longer mentioned in official plans.