How fusion works
The easiest reaction to reach joins two heavy forms of hydrogen, deuterium and tritium, into helium and a fast neutron, releasing energy. To make it happen the fuel must be heated to well over a hundred million degrees, where it becomes a plasma, and held together long enough for the reactions to pay back the energy put in.
Two main approaches
Magnetic confinement holds the plasma in a ring-shaped chamber using powerful magnets, in designs called tokamaks and stellarators. The large international ITER project in France is a tokamak under construction. Inertial confinement squeezes a tiny fuel pellet with lasers. In December 2022 a US laser facility reported getting more fusion energy out of the target than the laser energy delivered to it, a landmark for science, though far from a power plant.
What stands in the way
Materials that survive intense neutron bombardment, breeding the tritium fuel inside the machine, running steadily for long periods, and bringing the cost down. Several companies and governments are building pilot plants and aim to show electricity in the 2030s, but timelines in fusion have often slipped.
Where it is used
- Grid electricity (expected) If pilot plants succeed and the cost comes down.
- Industrial heat (proposed) High-temperature heat for industry.
- Science and engineering Plasma physics and materials research that other fields can use.
Fusion compared with fission and renewables
Fission splits heavy atoms and runs today. It gives steady power but produces long-lived waste. Fusion joins light atoms; it is not yet generating power and faces materials and fuel challenges. Wind and solar are cheap and growing but variable, and need storage.
If it works, fusion would offer steady low-carbon power, so it is generally seen as a complement to other sources, not a replacement.
Key terms
- Plasma
- A very hot gas whose atoms have been stripped of electrons.
- Tokamak
- A ring-shaped magnetic chamber for confining plasma.
- Deuterium and tritium
- Two heavy forms of hydrogen used as fusion fuel.
- Net energy gain
- Getting more energy out than was put in.
Common questions
Is fusion safe?
- A fusion reaction cannot run away like a fission chain reaction, and it does not produce long-lived high-level waste, though parts of the plant become radioactive and must be managed.
When will fusion power the grid?
- Pilot plants are targeted for the 2030s. Wide commercial use is later and uncertain.
How is fusion different from fission?
- Fission splits heavy atoms such as uranium. Fusion joins light atoms. They use different fuels and have different safety and waste profiles.
Sources and further reading
Independent pages we checked while writing this guide. They are not Reinnder products, and Reinnder is not affiliated with them.
Reinnder’s angle
How Reinnder looks at fusion power
Reinnder Energy and Reinnder Labs follow fusion as a long-horizon technology that could change clean power.
This guide explains the technology in general terms. It is not advice, and it does not describe a Reinnder product on sale.