Fusion reactors

Experimental machines that join light atoms, as the Sun does.

Capture · Emerging · No. 47

• Capture
• Output: Heat (experimental)

NIF's record laser shot in 2025 released 8.6 MJ of fusion energy, but its lasers drew about 300 MJ from the grid.

Chart: Illustration: Fusion reactors

Where it comes from

Chart: Map of where it comes from

Fusion joins light atoms, as the Sun does. Tokamaks and stellarators hold plasma above 100 million °C in magnetic fields; lasers crush pea-sized fuel capsules instead.

Three things to know

1. JET held a plasma gain of 0.33 for five seconds in 2021; ITER aims for a gain of 10 in 400-second pulses.
2. ITER needs 100,000 km of niobium-tin superconducting strand, over 400 tonnes, to make its confining magnetic fields.
3. Most activated materials in a fusion plant should be recyclable after about 100 years, but waste volumes are expected to be large.

The journey

1. 1 Light atomsDeuterium, plus tritium bred from lithium
2. 2 ConfinementMagnets hold plasma, or lasers crush fuel
3. 3 FusionNuclei join above 100 million °C
4. 4 BlanketNeutrons deposit heat and breed tritium
5. 5 TurbineHeat to electricity, 35-38% assumed

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