Reactor type 10 of 10
Fusion
by Joe Miller
Fusion joins light atoms, deuterium and tritium, at over 100 million degrees, the way the sun does. There is no chain reaction to run away, no meltdown and no long-lived high-level waste. It has reached real milestones, but no machine has yet made net electricity.
Plain-English explainer by Joe Miller, a nuclear engineer. Not investment advice. Figures are the latest public numbers we could find and change fast; sources are at the bottom of each page.
What it looks like
How the coolant circulates
- Magnets confine the deuterium-tritium plasma.
- Fusion releases fast neutrons that fly into the blanket.
- The blanket heats up and breeds tritium from lithium.
- Coolant carries blanket heat to a heat exchanger that makes steam.
- Tritium is recovered and fed back as fuel.
The main components
| Component | What it does |
|---|---|
| Plasma | Fuel heated so hot that electrons are stripped from atoms; it must never touch the walls. |
| Superconducting magnets | Hold and shape the plasma in a doughnut (tokamak) or twisted ring (stellarator). |
| Vacuum vessel and first wall | Take the heat and neutron bombardment; materials life is a major challenge. |
| Lithium blanket | Absorbs fast neutrons, turns their energy into heat, and breeds the tritium fuel. |
| Heating systems | Microwaves and neutral particle beams heat the plasma. |
| Heat exchanger and turbine | Blanket coolant makes steam like any other power plant. |
| Laser fusion alternative | NIF uses 192 lasers to crush a fuel capsule instead of magnets. |
Key details
| Item | Detail |
|---|---|
| Fuel | Deuterium (from seawater) and tritium (bred from lithium) |
| Temperature | Over 100 million °C |
| Waste | Activated structures, no long-lived spent fuel |
| Status | NIF ignition 2022; SPARC first plasma aimed at 2027; Helion target 2028; ITER D-T 2035 |
| Net electricity | Not yet demonstrated |
| Refueling | Continuous fueling |
How it is maintained
- Remote handling: the first wall and blanket become radioactive and must be replaced by robots.
- Component replacement every few years as neutrons damage materials.
- Tritium accounting and containment.
- Magnet cooling to near absolute zero.
Where it runs
Lawrence Livermore's NIF (ignition in 2022, 8.6 MJ record in 2025); Commonwealth Fusion Systems' SPARC (about 80% built, first plasma aimed at 2027); Helion's plant for Microsoft (2028 target); ITER in France (research operations around 2034); Wendelstein 7-X in Germany.
Who's writing this? I'm Joe Miller, a nuclear engineer since 1974 and an ASME Fellow. I've run safety analyses for PWRs and BWRs, directed nuclear engineering at a working BWR, and reviewed new reactor designs for the NRC. This site explains every kind of reactor in plain English. My background and papers.