Fire and Explosion Safety

The flammable inventory is small quantities of hydrogen isotopes; standard hydrogen-safety practice controls the risk, with no radiological coupling.

The combustible hazards in a fusion plant are ordinary industrial ones: small quantities of deuterium (and, in the breeder, tritium as a hydrogen isotope) that are flammable, plus conventional plant systems. There is no large flammable radioactive inventory of the kind that can couple a fire into a major radiological release.

The flammable inventory

• Deuterium: flammable hydrogen isotope in small working quantities — buoyant, disperses upward.
• Tritium (breeder): also a flammable hydrogen isotope, but in tiny quantities and sealed containment.
• Conventional systems: cabling, lubricants, electrical — standard fire-protection scope.

Hydrogen-isotope fire safety is a mature discipline: leak detection, ventilation to prevent accumulation, buoyant dispersion, elimination of ignition sources, and inerting where appropriate. The quantities involved are small, and hydrogen isotopes rise and disperse rather than pooling. A tritium-bearing fire is bounded by the very small tritium quantities in any single system and by secondary containment.

Decoupling from the radiological case

Crucially, a fire does not add energy to the fusion reaction (which needs confinement, not combustion) and cannot cause a chain reaction. The worst radiological consequence of a fire is bounded by the small tritium inventory it could mobilize — caught by containment and detritiation. See deuterium safety.

Fire safety here is conventional industrial fire protection plus tritium containment, not a nuclear fire scenario.