Several countries are developing their own concepts for demonstration fusion power plants.

Fission Plants Inspiration

A fusion power plant can be divided broadly into the reactor systems, where fusion energy is converted into heat, and the balance of plant, where this heat is converted into electricity. Many components outside the reactor itself — heat exchangers, turbines, generators and cooling systems — will be based on technologies already used in conventional thermal power plants. Several reactor coolants are being considered, including pressurised water, helium and liquid metals, and the achievable electrical efficiency will depend strongly on the temperatures and power-conversion cycle selected.

Schematic diagram of a fusion power plant and its electricity-generation system.

Thermal Storage

Many current demonstration-power-plant concepts are based on tokamaks, and some may operate in long pulses rather than continuously. In such designs, an intermediate thermal-energy-storage system could smooth the heat supply to the turbine during the dwell period between plasma pulses. Molten salts are among the storage media that have been investigated for this purpose in European DEMO studies.

Large Magnets

A fusion power plant will require powerful superconducting magnets to confine and control the plasma. Their size and field strength will depend on the reactor concept: some DEMO designs remain larger than present-day tokamaks, while other concepts pursue more compact high-field machines. ITER uses Nb₃Sn superconductors for its strongest magnets, providing valuable experience with large fusion-grade coils. High-temperature superconductors such as REBCO are also being developed because they can operate at higher magnetic fields and temperatures, although their long-term performance in a reactor environment still requires further demonstration.

Tritium Breeders

A breeding blanket will surround the plasma and perform several functions at once: it will breed tritium from lithium, remove fusion heat and shield the magnets and surrounding structures from neutrons. Different blanket concepts are being developed, including solid lithium-containing ceramic breeders and liquid lithium–lead systems, using water or helium as coolants in some designs. European DEMO studies continue to assess several concepts, including helium-cooled ceramic breeder and water-cooled lithium–lead blankets, while Japanese and Korean DEMO programmes have generally focused on ceramic breeder concepts with helium or water cooling. Tritium will be extracted continuously from the breeding material and returned to the fuel cycle. Because neutron irradiation gradually damages and activates blanket structures, large blanket modules will eventually have to be replaced remotely and transferred to dedicated maintenance and storage facilities.

Divertor

The divertor will usually be located at the lower part of the vacuum vessel, although alternative magnetic configurations with upper and lower divertors are also being studied. Its design must allow the removal of intense heat and particle fluxes while permitting remote maintenance and replacement of plasma-facing components.

Inputs and Outputs

A fusion power plant will require extensive auxiliary systems, including cryogenic refrigeration for superconducting magnets, vacuum systems, plasma-heating equipment, fuel handling, tritium processing, electrical power supplies and large cooling systems. Deuterium and lithium-containing breeder materials will provide the basic fuel resources, while tritium will be bred and recycled on site. The fusion reaction produces helium, but neutron activation will also create radioactive structural materials that require controlled handling, storage and, where possible, recycling.

Plant Layout

A fusion power station will consist of much more than the reactor itself. The tokamak complex will be surrounded by buildings for tritium processing, remote maintenance and hot-cell operations, cryogenic equipment, heating and power supplies, radioactive-material handling, cooling systems and electricity generation. The exact layout will depend on the reactor concept, safety requirements and maintenance strategy.