A power plant that produces net electricity from nuclear fusion, which first needs a fusion fuel target or plasma that releases several times more energy than is delivered to it.
Scope
In: deuterium-tritium fusion plants, whether by inertial confinement (laser-driven targets) or by magnetic confinement (tokamaks and stellarators). Out: fission and fission-fusion hybrids. The fuel supply is energy/tritium-breeding; the magnets are materials/low-cost-hts-conductor.
Scientific gain (Q_sci) headline1.8 orders of magnitude to go
Fusion energy released divided by the heating energy absorbed by the plasma or, in inertial confinement, by the driver energy delivered to the target (the target gain). Scientific breakeven is Q_sci = 1; it leaves out the energy drawn from the grid to run the drivers, heating and magnets. Higher is better.
Current (2022-12-05)1.5
Target100
Limit–
Conditions. Indirect-drive inertial confinement, laser energy delivered to the target, scientific breakeven.
Why this target. The high-gain requirement for an inertial fusion energy plant: a ratio of neutron yield to incident laser energy of about 100 (goncharov2025laser), stated independently as gains above 100 needed for a laser-fusion power plant (mcgeoch2025development). Gain must cover the driver's wall-plug efficiency, the thermal-to-electric conversion and the power recirculated to the driver, and still leave most of the output for the grid.
The record target gain is 1.5, from a single shot at the National Ignition Facility. A plant needs a gain of about 100, which in turn needs a high fraction of the laser energy coupled to the target and the loss mechanisms from laser-plasma instabilities held down. Broadband lasers show promise against those instabilities, and simulations predict gains above 100 with less than 1 MJ of argon fluoride laser energy in direct drive, with no experiment yet at that gain.
Low-cost high-temperature superconducting conductorCompact magnetic-confinement designs need fields above 18-20 T, for which high-temperature superconductors are the enabling technology, and their cost and complexity are a large part of the reactor core.
Tritium breedingDeuterium-tritium plants must breed their own tritium; natural supply is negligible.