Explore how fusion energy works, how it differs from fission, its fuels, safety and commercialization challenges through primary sources. Compare three approaches and explore research, companies and policy in Japan.
Fusion energy is released when light atomic nuclei join. Fusion also powers the Sun, but a terrestrial power plant uses different fuels and ways to sustain the reaction.
A guide to the mechanism, the challenges on the path to power generation and developments in the industry. Explore comparison diagrams, glossary entries and explainers for more detail.
Reference: QST's introductory explanation ↓Fusion joins light atomic nuclei; fission splits heavy ones. Fusion therefore differs from the reactions used in today's nuclear power stations.
In D–T fusion, using deuterium and tritium, a blanket captures the energy of the emitted neutrons as heat and transfers it to power-generation equipment. Producing a reaction is only part of the process: the heat must also be converted to electricity.
D–T fusion uses two forms of hydrogen: deuterium and tritium. The resources from which deuterium can be obtained are distinct from the processes needed to prepare reactor-ready fuel.
Tritium occurs naturally only in very small quantities. Establishing a cycle that breeds it through lithium–neutron reactions and recovers, purifies and reuses it remains a challenge. Abundant resources do not automatically ensure a reliable fuel supply.
Sources:NIFS: fuel and heat recovery ／ QST: reactor engineering
The fusion reaction itself emits no carbon dioxide. Together with potentially abundant fuel resources, this may support decarbonization and energy security. Generation costs and reliable operation still need to be demonstrated.
A fusion reaction continues only while conditions such as fuel supply and high temperature are maintained. Unlike a fission chain reaction, it stops when its required fuel supply or power is removed.
D–T systems nevertheless handle radioactive tritium, neutrons and activated structural materials. They require shielding, containment and waste management, as well as precautions for high temperatures, strong magnetic fields and other equipment hazards. Easy reaction shutdown does not mean that safety management is unnecessary.
Sources:Cabinet Office: national strategy ／ QST: reactor engineering
Japan aims to demonstrate fusion power generation in the2030s. This is a development target, not a confirmed date for electricity supply to homes. Producing reactions, delivering net electricity and supplying power economically and continuously are separate stages.
An energy-gain figure depends on the boundary used to compare input and output. The whole power plant must be assessed, including heating and cooling loads, fuel supply, material lifetimes and equipment replacement.
Sources:Cabinet Office: national strategy ／ QST: fundamentals ／ QST: reactor engineering
Distinguish the roles of research institutions and devices from the equipment and technologies supplied by companies. Explore the path from research to business through machines, supply chains and policy.
Read about the purposes and verified development stages of ITER, JT-60SA and demonstration plants.
Explore projects →From reactor development to materials, vacuum, superconductors and maintenance: identify each company's role and evidence of its work.
Explore companies →Start with the technology you need →Distinguish national policies from individual programmes and calls; check participation requirements in official documents.
Explore policy and regulation →Explore opportunities and procurement →Fusion reactions, fuels, plasma and energy gain
D–T heat recovery, blankets and tritium breeding
Fuel breeding, shielding, heat recovery and safe handling technologies
National strategy, pathways to deployment and fundamental safety principles
This guide is edited from public sources. It does not imply review or endorsement by the research institutions. Image sources appear below each figure.
Start with principles, methods, research devices or power generation, wherever your interest lies.
Start with how fusion releases energy.
Explore the differences between tokamak, helical and laser approaches.
View the downloadable comparison chart ↓Learn what JT-60SA and ITER are each designed to investigate.
Explore demonstration power plants and the technologies needed across the power-generation system.
Compare confinement approaches and the challenges of power generation. Save the diagram for explanation and review.
Magnetic confinement
Magnetic confinement: stellarators, heliotrons and related devices
A form of inertial confinement
This diagram does not rank approaches or commercialization prospects. Results from research devices are distinct from demonstrating a power plant.
Save the comparison PNG ↓An original FUSION INDUSTRY comparison diagram, credited to fusionindustry.jp/learn.
Nuclear fusion
From the fusion reaction to electricity supply, this guide explains fuel, confinement, heat recovery and plant consumption. Primary sources help distinguish fusion's benefits and challenges, deployment targets and the conditions needed for viable businesses.
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National Institutes for Quantum Science and Technology
QST stands for the National Institutes for Quantum Science and Technology. This Japanese research institution advances ITER, JT-60SA and demonstration-reactor development through its Naka and Rokkasho sites.
Read the definition and related informationNaka Institute for Fusion Science and Technology
QST's institute in Naka City, Ibaraki. It advances JT-60SA plasma research and component and reactor-engineering work supporting ITER.
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Rokkasho Institute for Fusion Energy
QST's institute in Rokkasho, Aomori connects fusion to power systems through research on demonstration-reactor design, materials, neutron sources, blankets and fuel.
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ITER (fusion experimental reactor)
ITER is an international fusion experiment under construction in southern France. It studies burning plasma and machine technology, but will not generate or transmit electricity.
Read the definition and related informationJT-60SA (JT-60 Super Advanced)
Japan–Europe superconducting tokamak at Naka, supporting ITER, future demonstration reactors and fusion research training.
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Q-DEMO (conceptual design for an ITER-sized fusion demonstration reactor)
QST’s ITER-sized demonstration-reactor concept, targeting phased validation of electricity generation, fuel breeding and steady-state operation.
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Activation and radioactive waste
Fusion still requires management of activated materials and tritium. Conditions vary with the approach, materials and fuel.
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Fusion reactor blanket
In a D–T fusion reactor, the blanket receives neutron energy as heat and also supports tritium breeding. Heat extraction and material durability are crucial.
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Commercialization of fusion energy
Look beyond company target years to what each project plans to demonstrate and its stage of development.
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Direct energy conversion
DEC recovers charged-particle kinetic energy without a heat engine. Learn why magnetic mirrors offer a suitable exhaust path and why WHAM’s demonstration is not net-electricity generation.
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Nuclear fission
Fusion joins light nuclei; fission splits heavy nuclei. An overview of their different principles and technical challenges.
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Field-reversed configuration
This approach uses a plasma structure called a field-reversed configuration. Helion's magnetic compression and TAE's beam-driven approach differ in operation and fuel strategy.
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Fusion fuel cycle
Fusion fuel does not simply pass through a reactor once. Understand the separate tasks of recovering unburned fuel from a D–T system’s exhaust, replacing consumed tritium, and preparing fuel for reuse.
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Magnets using high-temperature superconducting materials
Magnet technology for producing strong magnetic fields. CFS uses REBCO high-temperature superconducting materials in more compact high-field tokamaks.
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Laser-driven inertial-confinement fusion
Lasers compress and heat tiny fuel targets. For power generation, integrating high-repetition-rate irradiation with target supply is a challenge.
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The loss cone describes velocity directions for particles that escape without magnetic reflection. It is a region in velocity space, not a cone-shaped hole in the vessel.
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A magnetic mirror reflects some charged particles using a magnetic field that becomes stronger toward its ends. Learn the reflection condition, end losses and the WHAM example.
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The mirror ratio compares the strong end field with the weaker central field. The same peak field can give different ratios, and one number cannot describe device performance.
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Ratio of fusion power to external plasma heating
Plasma energy gain Q and net electricity after subtracting the entire plant's power consumption are different metrics. Check the measurement boundary before comparing numbers.
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Stellarator (helical-family magnetic confinement)
How do external coils confine a hot plasma? Explore stellarator magnetic fields, the differences between LHD and W7-X, long-pulse results and the engineering challenges on the path to fusion power.
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A tandem mirror connects a central plasma region to end plugs. Their electrostatic potential helps reduce particle escape. Learn how this differs from a simple mirror and why WHAM is not a complete tandem device.
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Tokamak magnetic confinement
A tokamak uses magnetic fields to confine hot plasma in a toroidal vessel. Integrated design covering heating, control and materials is essential.
Read the definition and related informationEach page explains one key term. Entries for institutions and devices share their project information pages. For news and in-depth analysis, follow the related articles on each page.
What is fusion energy? Start with principles, approaches, devices or the challenges of power generation. You do not need to know every abbreviation first.
Start by understanding how fusion energy works. Use the glossary on this page to check unfamiliar terms, then explore the approaches and devices that interest you.
Fusion joins light nuclei, while fission splits heavy nuclei. Explore not only their reactions but also differences in fuel, control and the challenges of generating electricity.
They have different purposes and development stages. Focus on what each device or plan aims to research or demonstrate to understand the path from research towards power generation.
