The radioactive hydrogen isotope at the heart of near-term fusion — rare, expensive, and self-consuming, making tritium supply the critical bottleneck for commercial D-T fusion power.
Tritium (3H or T) is a radioactive isotope of hydrogen with one proton and two neutrons. It decays by beta emission with a half-life of 12.32 years, emitting a low-energy electron (maximum 18.6 keV) that cannot penetrate skin or paper. Tritium does not occur naturally in significant quantities — the global inventory is approximately 25–30 kg, produced as a byproduct of heavy-water fission reactors (CANDU).[1]
CANDU reactors: Ontario Power Generation (Canada) detritiates heavy water from its CANDU fleet, producing ~0.5–1.5 kg/year. This is essentially the only current source. Future breeding: Fusion reactors will breed tritium via 6Li(n,t)4He and 7Li(n,n′t)4He reactions in lithium-bearing blankets. Cost: Tritium is valued at $30,000–100,000 per gram, making it one of the most expensive substances on Earth.[2]
Tritium is a low-hazard radioactive material — its beta radiation cannot penetrate the dead outer layer of skin. The primary concern is inhalation or ingestion of tritiated water (HTO). Fusion reactors will contain 1–4 kg of tritium on-site, requiring robust containment and accountancy systems, but this represents a far smaller radiological hazard than the fission product inventory in a fission reactor.[3]