Why won't fusion explode?
The most common question — and the most reassuring answer.
This is the question I hear most often when I talk about nuclear fusion. And the answer is: it is physically impossible.
A nuclear bomb uses fission — the uncontrolled splitting of uranium or plutonium. Fusion requires extremely precise conditions of temperature, pressure and confinement to occur. If any one of those parameters falls out of control — if the plasma cools even for a millisecond — the reaction simply stops. It is the opposite of an explosion.
On top of that:
- Fusion produces no long-lived radioactive waste. The main by-product is Helium — inert and harmless.
- The fuel (deuterium and tritium) cannot be used to make bombs.
- There is no chain reaction. Without continuous fuelling, the process stops immediately.
In safety terms, nuclear energy is one of the sources with the lowest mortality rate per unit of energy generated: 0.04 deaths per terawatt-hour — compared with 24.6 for coal. Nuclear results in 99.8% fewer deaths than coal per unit of energy generated.
Source: Our World in Data, "What are the safest sources of energy?", 2024.