Build the power plant
The plasma is only the beginning. Each layer has to work on its own, and then work with every other layer, repeatedly, for years.
01Magnets & superconductors
A magnetic fusion plant begins with a field strong enough to keep an extraordinarily hot plasma away from the walls. Superconducting coils carry enormous currents; cryogenics keeps the conductors below their operating limits.
Confine the plasma
Conventional D-T magnetic plantSuperconducting coils create a magnetic cage. Stronger fields can shrink the machine, but neutron shielding and structural loads set physical limits.
20 T · Full-scale MIT/CFS HTS magnet resultHigher field can make a smaller machine. The MIT/CFS programme demonstrated a full-scale REBCO magnet at 20 T. ITER’s conventional superconducting system stores about 51 GJ. Compact high-field designs still need structural support, quench protection, and enough shielding to protect their coils from neutrons.
What’s inside: components, evidence, and interfaces
- Components
- REBCO or Nb₃Sn/Nb-Ti conductor, toroidal and poloidal coils, structural cases, joints, cryostat, power supplies.
- Key metrics
- Peak field (T), stored energy (GJ), critical current, operating temperature, strain, and joint resistance.
- Readiness
- TRL 6-8 for low-temperature superconducting systems; approximately 5-6 for compact HTS fusion systems.
- Interfaces
- Cryogenics → conductor → coil → plasma control; neutron shielding protects the magnet system.
- Principal risk
- Mechanical stress, radiation damage, detection of quenches, and economical production of fusion-grade REBCO tape.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
Commonwealth Fusion Systems / MIT
ITER Organization
Tokamak Energy
Proxima Fusion
Thea Energy
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
02Vacuum & plasma heating
The vessel must hold a clean, near-empty environment while fuel flows in and helium ash flows out. Neutral beams and radio-frequency systems then heat the plasma and, in many tokamaks, help sustain its current.
Industrial experience does not yet equal power-plant availability. ITER’s systems evacuate a 1,400 m³ vessel and an 8,500 m³ cryostat. Each heating neutral beam is designed to deliver 16.5 MW of 1 MeV deuterium for up to 3,600 seconds. A commercial plant must do this efficiently and reliably while handling tritiated exhaust.
What’s inside: components, evidence, and interfaces
- Components
- Vacuum vessel, mechanical pumps, cryopumps, neutral-beam injectors, RF sources, transmission systems, and plasma controls.
- Key metrics
- Base pressure, pumping speed, leak rate, injected MW, wall-plug efficiency, and pulse length.
- Readiness
- Vacuum systems approximately TRL 7-8; heating approximately 7-8 experimentally, 5-6 at plant efficiency and availability.
- Interfaces
- Fuel cycle, plasma exhaust, cryogenics, electrical supplies, vessel seals, and shielding.
- Principal risk
- Tritiated pumping, remote maintenance, component lifetime, coupling losses, and high recirculating power.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
ITER Organization
UKAEA
TAE Technologies
QST / Fusion for Energy
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
03Fuel & the tritium cycle
Deuterium is widely available. Tritium is not. A deuterium-tritium plant must recover unburned fuel and breed replacement tritium from lithium, closing a cycle that current experiments do not demonstrate at commercial scale.
A reactor cannot simply buy decades of fuel. A 1 GW fusion source consumes about 55.8 kg of tritium per full-output year. Tritium also decays, with a 12.32-year half-life. Breeding must exceed consumption with enough margin for decay, processing inventory, extraction delays, and losses.
What’s inside: components, evidence, and interfaces
- Components
- Fuel injection, isotope separation, storage beds, detritiation, blanket extraction, and fuel-accounting systems.
- Key metrics
- Tritium breeding ratio, inventory, burn-up fraction, processing residence time, permeation, and losses.
- Readiness
- TRL 6-7 for tritium handling; approximately 3-4 for an integrated closed commercial cycle.
- Interfaces
- Lithium blanket → extraction → isotope separation → storage → plasma → exhaust recovery.
- Principal risk
- Scarce start-up inventory, insufficient breeding margin, and tritium permeation into coolant and structures.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
UKAEA / LIBRTI
ITER Organization
EUROfusion DEMO
BABY experimental programme
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
04Blanket, first wall & materials
The blanket has three jobs: turn neutron energy into heat, breed tritium, and shield the rest of the machine. The first wall and divertor must withstand extreme heat and particle loads while remaining replaceable.
This is one of the least mature integrated layers. D-T neutrons carry 14.1 MeV and progressively damage structural materials. ITER’s blanket can remove roughly 736 MW of heat, but breeding is tested in modules rather than a self-sufficient fuel cycle. Heat removal alone is not a validated power-plant blanket.
What’s inside: components, evidence, and interfaces
- Components
- Lithium breeder, tungsten plasma-facing surfaces, structural steel, neutron shielding, coolant channels, and divertor.
- Key metrics
- Breeding ratio, heat flux (MW/m²), neutron wall load, displacements per atom, coolant temperature, and replacement interval.
- Readiness
- Approximately TRL 3-5 for the integrated blanket and breeder.
- Interfaces
- Plasma → first wall → blanket → coolant and tritium plant; blanket → shielding → magnets.
- Principal risk
- Cracking, erosion, embrittlement, corrosion, tritium permeation, and remote replacement of activated components.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
ITER Organization
EUROfusion DEMO
IFMIF-DONES
UKAEA
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
05Heat, turbines & net power
Hot coolant transfers the captured energy to a power cycle. Steam turbines are mature technology, but integrating them with a fusion heat source, tritium isolation, and large auxiliary loads is a new problem.
Gross generation is not what reaches the grid. The ARC physics basis gives an illustrative chain of about 1.18 GW thermal input, 500 MWe gross generation at 42% efficiency, and 400 MWe net after approximately 100 MW of house loads. These are design quantities, not measured plant output.
What’s inside: components, evidence, and interfaces
- Components
- Primary coolant loop, heat exchangers, steam generator, turbine, condenser, generator, and grid connection.
- Key metrics
- Thermal efficiency, gross and net MWe, coolant outlet temperature, recirculating load, and capacity factor.
- Readiness
- TRL 9 for conventional steam Rankine equipment; approximately 4-6 for an integrated fusion plant.
- Interfaces
- Blanket → primary coolant → heat exchanger → turbine → generator → grid and plant auxiliaries.
- Principal risk
- Coolant temperature limits, pulsed heat input, tritium isolation, and electricity consumed by the machine itself.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
Commonwealth Fusion Systems
EUROfusion DEMO
UK Fusion Energy / STEP
Type One Energy
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
06Maintenance & availability
A successful pulse lasts seconds. A useful asset must operate for decades. Activated internal components need remote inspection and replacement, with access designed into the machine from the start.
Component lifetime becomes an electricity-cost problem. Once a plasma is comfortably burning, a longer-lived blanket or a shorter maintenance outage can be more valuable than a small improvement in plasma gain. Remote handling, replaceable modules, and material qualification are essential parts of the plant architecture.
What’s inside: components, evidence, and interfaces
- Components
- Remote manipulators, inspection systems, replaceable blanket and divertor modules, hot cells, and material qualification facilities.
- Key metrics
- Replacement interval, outage duration, net annual capacity factor, inspection coverage, and replacement cost.
- Readiness
- Industrial remote-handling experience exists; a commercially available integrated fusion maintenance regime remains unproven.
- Interfaces
- Vessel access, magnets, activated blanket and divertor, tritium containment, and plant operations.
- Principal risk
- Long unscheduled outages, inaccessible components, activation, and repeated replacement costs.
Adapted from the physical-stack section of fusion.md. Technology readiness levels are analyst mappings, not official programme ratings.
Research & industry participants
UKAEA
EUROfusion DEMO
ITER Organization
IFMIF-DONES
Programmes associated with this layer in the supplied report; inclusion does not imply a supplier contract.
Different machines, shared constraints
Every architecture trades one difficult problem for another. The useful comparison is the complete power-production boundary.
High-field tokamak
Stronger magnets make the machine smaller. The deepest magnetic-confinement evidence base still leaves disruptions, neutron shielding, tritium breeding, and plant availability to solve.
Stellarator
Complex coils provide naturally steady-state confinement without a large driven plasma current. The trade is demanding geometry, manufacturing, and access for maintenance.
Laser inertial fusion
NIF has demonstrated target ignition. A power plant needs efficient lasers, inexpensive precision targets, several shots per second, and a chamber that survives repeated neutron loads.
Pulsed and direct-conversion concepts
Z-pinches, magnetised targets, FRCs, and magnetic mirrors simplify parts of the conventional plant. They introduce demanding confinement, repetition-rate, fatigue, or energy-recovery requirements.
Removing a component from a reactor diagram does not remove its job from the power plant.
Who is building what
Public experiments establish the physics and integration base. Private programmes pursue shorter design-build-test cycles across multiple architectures.
Commonwealth Fusion SystemsSPARC → ARCHigh-field tokamak
- Reported evidence
- SPARC reported almost 80% complete
- Announced next step
- ~400 MWe, early 2030s
- Unresolved risk
- Blanket, fuel cycle, and availability beyond SPARC
HelionPolaris → OrionPulsed FRC / direct conversion
- Reported evidence
- Polaris operating; company reports D-T fusion
- Announced next step
- ≥50 MW, originally 2028
- Unresolved risk
- Net electricity at commercial repetition rate
TAE TechnologiesDa VinciBeam-driven FRC
- Reported evidence
- Five reactor generations operated
- Announced next step
- First operations, 2031
- Unresolved risk
- Confinement and recirculating beam power
Proxima FusionAlpha → StellarisHTS stellarator
- Reported evidence
- Alpha consortium; €411m financing in 2026
- Announced next step
- Demonstrator, early 2030s
- Unresolved risk
- Burning plasma, complex coils, and maintenance
Type One EnergyInfinity TwoStellarator
- Reported evidence
- 400 MWe design with TVA interest
- Announced next step
- 400 MWe design capacity
- Unresolved risk
- Whole-plant validation beyond existing stellarators
Thea EnergyEos → HeliosPlanar-coil stellarator
- Reported evidence
- Full-size Eos-spec coil operated in 2026
- Announced next step
- Helios preconcept reviewed
- Unresolved risk
- Reactor-scale plasma and neutron geometry
Tokamak EnergyST40 / Demo4Spherical tokamak / HTS
- Reported evidence
- Demo4 reached 13.7 T; STEP magnet partner
- Announced next step
- HTS and plasma development
- Unresolved risk
- Centre-column shielding and plant engineering
General FusionLM26Magnetised-target fusion
- Reported evidence
- Compressional heating demonstrated
- Announced next step
- Lawson milestones through 2028
- Unresolved risk
- Compression symmetry, fatigue, and repetition
Zap EnergyCenturySheared-flow Z-pinch
- Reported evidence
- 1,080 consecutive ≥100 kA plasmas
- Announced next step
- ~50 MWe/module preconcept
- Unresolved risk
- High-current stability and electrode lifetime
Pacific FusionDemonstration SystemPulsed-magnetic inertial fusion
- Reported evidence
- Campus broke ground in August 2026
- Announced next step
- Net facility gain, 2030
- Unresolved risk
- High-yield targets and repetitive chamber systems
Xcimer EnergyPhoenix → Vulcan → AthenaExcimer-laser inertial fusion
- Reported evidence
- Phoenix operating; >1 kJ source
- Announced next step
- 400 MWe, mid-2030s
- Unresolved risk
- Efficient, durable, repetitive multi-MJ lasers
Marvel FusionATLASLaser inertial / fast ignition
- Reported evidence
- $150m laser demonstrator with CSU
- Announced next step
- Early operation around 2027
- Unresolved risk
- Target gain, laser efficiency, and optics lifetime
Focused EnergyGerman-US laser programmeLaser inertial fusion
- Reported evidence
- Biblis concept reported in research
- Announced next step
- Mid-2030s ambition
- Unresolved risk
- Driver, target, and chamber integration
Realta FusionWHAMAxisymmetric magnetic mirror
- Reported evidence
- Plasma kinetic-energy conversion in 2026
- Announced next step
- Confinement and conversion development
- Unresolved risk
- End losses and reactor confinement
ITER OrganizationITERSuperconducting tokamak
- Reported evidence
- Assembly and integration
- Announced next step
- D-T operation, 2039; no electricity
- Unresolved risk
- Full-scale first-of-a-kind integration
UK Fusion Energy / UKAEASTEPSpherical tokamak
- Reported evidence
- Engineering and development programme
- Announced next step
- First operations, 2040
- Unresolved risk
- HTS, shielding, and maintainability
EUROfusionDEMOD-T tokamak
- Reported evidence
- Concept and technology development
- Announced next step
- 300-500 MWe design
- Unresolved risk
- Closed fuel cycle and plant availability
LLNLNational Ignition FacilityLaser inertial fusion
- Reported evidence
- 8.6 MJ yield; target gain 4.13
- Announced next step
- Ignition research; no electricity plant
- Unresolved risk
- Target gain excludes facility electricity
Max Planck IPPWendelstein 7-XStellarator
- Reported evidence
- 1.8 GJ energy turnover over 360 s
- Announced next step
- Long-duration confinement research
- Unresolved risk
- Extrapolation to burning-plasma conditions
Programme status and target dates are reproduced from the supplied September 2026 research. A target is not a forecast; a design review is not hardware validation.
There is more than one finish line
“Net energy” can describe entirely different boundaries. Crossing one does not mean the next has been crossed.
- 1
Scientific breakeven
Fusion output exceeds energy delivered directly to the target or plasma.
Demonstrated at NIF’s target - 2
Facility breakeven
Output also covers the energy consumed by the driver and machine.
Not demonstrated in this record - 3
Net electricity
Electrical generation exceeds all plant auxiliary loads.
Not demonstrated - 4
Repeatable pilot operation
Meaningful electrical output, maintainability, and sustained availability.
Analyst outlook: 2030s - 5
Financeable commercial power
Reliable generation at a capital and operating cost buyers can finance.
Analyst outlook: a harder 2040s problem
Announced net electrical capacity
Company targets. No demonstrated net fusion electricity in the supplied record.
Source: fusion.md, “How close fusion is to deployment.” Evidence & definitions
View the report’s probability ranges
| Milestone | Date | Analyst probability |
|---|---|---|
| Private magnetic plasma Q > 1 | 2030 | 65-80% |
| >10 MWe net exported to a grid | 2030 | 20-35% |
| Repeated ≥50 MWe pilot operation | 2035 | 45-65% |
| ≥300 MWe plant, >50% annual capacity factor | 2040 | 20-35% |
| Financeable repeat-order plant below ~$7.5m/MWe | 2045 | 15-30% |
| >1 GWe operating commercial fusion globally | 2050 | 45-70% |
Judgements from the report, not project-published probabilities or statistical confidence intervals.
The cost of useful electricity
The denominator matters. A 500 MW fusion plasma with no turbine has zero electrical capacity. A 500 MWe generator using 100 MW to run its own plant exports 400 MWe.
What it may cost. What the grid can afford.
Cheap fuel alone does not make cheap fusion power. Financing, replacement blankets and divertors, recirculating electricity, and unscheduled downtime can dominate the economics.
What would the electricity cost?
Change the assumptions. The result is a scenario, not a price forecast.
Levelised cost of electricity
- Capital recovery
- $110
- O&M + replacements
- $51
- Variable / fuel cycle
- $8
35-year life; fixed O&M 3% of CAPEX/year; variable cost $8/MWh. All capital costs use net electrical capacity. Real 2026 dollars; excludes tax credits, construction-period interest, and decommissioning.
Calculation & assumptions
LCOE = CAPEX × (capital recovery factor + fixed O&M + replacement reserve) ÷ (8.76 × capacity factor) + variable costs.
CAPEX is converted to $/kWe; annual percentages and capacity factor are expressed as fractions. Capital recovery uses the selected real discount rate and scenario lifetime. Reset a scenario to restore its original inputs.
The report suggests experience rates of 2-8% per cumulative-capacity doubling, closer to large, customised thermal plants than mass-produced electronics. Standardisation and easier maintenance matter as much as a smaller reactor core.
About the record
This page is an editorial adaptation of Fusion Energy: The Physical Stack, Economics and Path to Commercial Power, with a research cut-off of 16 September 2026. Monetary figures are US dollars unless labelled otherwise.
- Reported / measured
- An experimental result or programme status recorded in the research.
- Announced / target
- A company or programme’s intended future performance or date.
- Modelled / derived
- A study result or calculation conditional on stated assumptions.
- Analyst judgement
- An interpretation of readiness, timing, or probability, not a measured result.
Source limitation: the supplied Markdown includes citation identifiers, but no resolvable bibliography for those identifiers. Claims here are attributed to that report and have not been independently reverified.