Mercedes Mullins
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. Research into fusion reactors began in the 1940s, but as of 2025, only a few devices have reached net power. Fusion reactors use a combination of hydrogen gases—deuterium and tritium—heated to very high temperatures (over 100 million degrees Celsius) to generate power. The amount of fuel required depends on the type of fuel and the energy output of the plant. A large fusion power station generating 1500 megawatts of electricity would use approximately 600 grams of tritium and 400 grams of deuterium each day, while a 1000 MW coal-fired power plant requires 2.7 million tonnes of coal per year. The ITER fusion reactor in France will aim to produce 500 megawatts of fusion power and will require 300 grams of tritium per day.
| Characteristics | Values |
|---|---|
| Fuel used in fusion reactors | Hydrogen, Deuterium, Tritium, Lithium, Protium, Boron |
| Fuel required for a 1000 MW fusion plant per year | 250 kgs |
| Fuel required for a small-scale fusion station | 400 g per year |
| Fuel required for an 800 MW demonstrator | 300 g of tritium per day |
| Fuel present in the plasma at any given moment | A few grams |
| Fuel present in the vacuum vessel at any given moment | Less than 1 g |
| Fuel cycle | Tritium is bred within the fusion reaction |
| Fuel extraction | Multiple technologies are involved, including tokamak exhaust processing, isotope separation, storage and delivery, atmospheric detritiation, water detritiation, and analytics |
| Fuel activation | Lithium breeding blankets are subjected to neutron fluxes to generate tritium |
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What You'll Learn
Deuterium-tritium (D-T) reaction
The deuterium-tritium (D-T) reaction is a fusion process that combines hydrogen's isotopic variants, deuterium and tritium, to generate energy. This reaction has been identified as the most efficient for fusion devices among the different isotopes of light elements that can be paired to achieve fusion. The D-T reaction requires significantly less fuel than other power plants, with only a few grams of fuel present in the plasma at any moment. For context, a 1000 MW coal-fired power plant consumes 2.7 million tonnes of coal annually, whereas a fusion plant with the same output would only need 250 kgs of fuel per year, evenly split between deuterium and tritium.
Deuterium, a hydrogen atom with a single proton, is easily accessible since it can be distilled from all forms of water, including seawater, where about 1 in every 6700 hydrogen atoms is deuterium. It is also routinely produced for scientific and industrial applications. On the other hand, tritium is a fast-decaying radioisotope of hydrogen with a short half-life and no natural sources. This challenge is typically overcome by producing tritium during the fusion reaction through contact with lithium. In fusion reactors, a 'breeding blanket' made of lithium orthosilicate is often placed along the walls to capture free neutrons created by D-T fusion and produce more tritium.
The D-T fusion process involves heating a combination of deuterium and tritium gases to temperatures exceeding 100 million degrees Celsius. At these extreme temperatures, the gas becomes a plasma, and the nuclei fuse to form a helium nucleus and a neutron, with a small fraction of the mass converted into fusion energy. This reaction releases a free neutron, which can be utilised to generate more tritium by bombarding lithium.
The D-T reaction has been studied and developed in fusion devices known as tokamaks, a Russian word for a ring-shaped magnetic chamber. These devices use powerful magnets to control the intensely hot plasma. JET, a tokamak experiment, achieved a record-breaking 59 megajoules of sustained fusion energy over five seconds using the D-T fuel mix. The ITER tokamak, currently under construction in France, aims to build on these successes and demonstrate the viability of fusion power on a commercial scale.
Spin-polarized D-T fuel has been proposed as a method to increase the tritium burn efficiency (TBE) significantly without sacrificing output. For example, in a 481 MW ARC-like tokamak, using spin-polarized fuel with a 63:37 D-T mix reduced the required tritium inventory from 0.69 kg to 0.03 kg. This improvement in TBE can be further enhanced by advancements in helium divertor pumping efficiency, potentially achieving values of 10%-40% with low-tritium-fraction spin-polarized fuel.
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Fuel cycle
Fusion power is an attractive option for energy generation due to its environmental benefits and the abundance of its fuel sources. The two primary fuels required for fusion reactions are hydrogen and lithium, both of which are widely available worldwide.
The fusion reaction combines two light elements, such as hydrogen's isotopic variants deuterium and tritium, to form a heavier element. This process releases a significant amount of energy, with only a few grams of fuel needed in the plasma at any given moment. For example, a 1000 MW coal-fired power plant requires 2.7 million tonnes of coal annually, whereas a fusion plant with the same output would only need 250 kg of fuel, half deuterium, and half tritium.
Deuterium is readily obtainable from all forms of water, including seawater, and is safe and virtually inexhaustible. Tritium, on the other hand, is a fast-decaying radioisotope of hydrogen that occurs naturally in trace amounts. It can be produced during the fusion reaction through contact with lithium or bred within the fusion reaction itself.
The breeding of tritium is crucial for the long-term sustainability of large-scale fusion power plants. While the current global inventory of tritium is limited to around 20 kg, fusion power stations can produce substantial amounts. However, establishing a self-sustaining tritium fuel cycle within fusion reactors can take decades due to the need for special neutron multiplier-enriched blankets.
The fusion fuel cycle involves several steps. First, air and impurities are evacuated from the vacuum vessel. Then, powerful magnets are activated to confine and control the plasma, after which the low-density gaseous fuel is injected into the vessel. An electrical current is applied to the system, causing the gas to become ionized and form a plasma. The plasma facilitates the fusion reaction, resulting in the release of energy.
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Fuel extraction
Raw Material Extraction:
The first step is to extract the raw materials required for fuel production. For a fusion reactor, the primary raw material is often lithium, which can be obtained from seawater. Lithium reserves in seawater are practically unlimited and could potentially fulfill the world's energy needs for approximately 60 million years. Additionally, deuterium, a naturally occurring isotope of hydrogen, is also extracted from water sources. It is abundant and can be distilled from all forms of water, including seawater, where there are about 33 grams of deuterium per cubic meter.
Fuel Processing:
Once the raw materials are obtained, they undergo processing to produce the fusion fuel. In the case of lithium, it is used in the breeding process to generate tritium, a crucial fuel component. Tritium is a fast-decaying radioisotope of hydrogen that occurs in trace amounts in nature. Through the fusion reaction, neutrons escaping the plasma interact with lithium, producing tritium. This breeding process is essential for sustaining the fuel cycle in a fusion reactor.
Fuel Cycle Optimization:
Compounds and processes are optimized to efficiently breed and sustain the tritium fuel cycle. This involves the development of materials and technologies that can maximize the breeding process, ensuring a consistent supply of tritium fuel for the fusion reactor.
Fuel Injection:
After the fuel is produced and processed, it is introduced into the fusion reactor. This involves evacuating all air and impurities from the vacuum vessel of the reactor. Then, powerful magnets are activated to confine and control the low-density gaseous fuel, which is injected into the vessel through a gas injection system.
Fuel Reinjection:
In the divertor region of the reactor, powerful torus cryopumps are employed to continuously exhaust unconsumed fuel, helium ash, and impurities. The extracted fuel is then sent to the Tritium Plant, where it undergoes multiple separation and purification processes. The purified fuel is then stored and reinjected into the fuelling cycle, ensuring efficient utilization of resources.
The fuel extraction and management process for a full-scale fusion reactor is complex and involves various technologies. The optimization of fuel breeding, extraction, and reinjection processes is vital to ensure a consistent and sustainable supply of fuel for the reactor's operation.
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Fuel requirements
Fusion power is an attractive option to meet the growing demand for energy, as it does not produce carbon emissions or other harmful atmospheric emissions. The fuel requirements for a full-scale fusion reactor are dependent on the type of fuel used and the energy output of the reactor.
The most common fuel mix for fusion power is a combination of hydrogen gases—deuterium and tritium. Deuterium can be distilled from all forms of water and is readily available, while tritium is a radioactive isotope of hydrogen that occurs in trace amounts in nature. However, tritium can be produced during the fusion reaction through contact with lithium, a process known as "breeding".
The amount of fuel required is relatively small compared to other power sources. For example, a 1000 MW coal-fired power plant requires 2.7 million tonnes of coal per year, while a fusion plant with the same output will only require 250 kgs of fuel per year, with half being deuterium and the other half being tritium.
The ITER fusion reactor, currently being constructed in France, will require 300 grams of tritium per day to produce 800 MW of power. This equates to approximately 109.5 kg of tritium per year. According to one source, the current global demand for tritium is 400 grams per year, with a total remaining supply of around 75 kg. This highlights the need for efficient tritium breeding within fusion reactors to sustain their fuel cycle.
While fusion power offers the potential for abundant energy, the reality is that there is currently a limited supply of tritium available. This means that the development of fusion reactors must be accompanied by advancements in tritium breeding technology to ensure a sustainable fuel source.
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Fuel sources
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, releasing energy. This process requires fuel in a state of plasma, and a confined environment with sufficient temperature, pressure, and confinement time.
The two sources of fuel for fusion reactions are hydrogen and lithium, which are widely available in many parts of the Earth. Hydrogen is the most common fuel, with its isotopic variants deuterium and tritium forming a powerful cocktail for fusion reactions. Deuterium can be distilled from all forms of water, including seawater, and is a virtually inexhaustible resource. Tritium, on the other hand, is a fast-decaying radioelement of hydrogen that occurs only in trace amounts in nature. It can be produced during the fusion reaction through contact with lithium, a process known as "breeding" tritium.
The amount of fuel required for a fusion reactor depends on various factors, including the type of fuel used and the energy output of the reactor. A reactor generating more than 1 kilowatt of power will use more fuel, with estimates ranging from 520 grams of fuel for a thousand years to 5200 kilograms for ten thousand years. However, these numbers may not be directly comparable due to the varying efficiency of different fuel cycles. For example, the p-11B aneutronic fuel cycle produces most of its reaction energy as charged particles, allowing for more efficient energy harvesting.
ITER, a multinational tokamak fusion reactor under construction in France, aims to produce 500 megawatts of fusion power. It will require 300 grams of tritium per day for its 800 MW demonstrator, amounting to 250 kilograms of fuel per year, with half deuterium and half tritium. This is a significantly smaller amount of fuel compared to a 1000 MW coal-fired power plant, which consumes 2.7 million tonnes of coal annually.
While fusion reactors require limited fuel, the challenge lies in achieving and sustaining the conditions necessary for fusion, such as extremely high temperatures and confinement of the plasma.
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Frequently asked questions
The amount of fuel needed depends on the type of fuel used and the energy output of the reactor. A 1000 MW fusion plant will require 250 kgs of fuel per year, half of it deuterium, and half of it tritium.
Fusion reactors use hydrogen and lithium as fuel. The most efficient fusion reaction involves the use of hydrogen's isotopic variants, deuterium and tritium.
Fusion reactors breed their own fuel, tritium, through neutron fluxes interacting with lithium. Tritium is also produced in the fusion reaction and is consumed within the plant in a closed circuit.
A 1000 MW coal-fired power plant requires 2.7 million tonnes of coal per year, while a fusion plant with the same output requires only 250 kgs of fuel per year, making fusion fuel highly efficient and virtually inexhaustible.
