isotope separation is the industrial extraction of one isotope of an element from another, as in producing deuterium from seawater or enriching lithium-6 for 📝fusion blankets.
The term is distinct from chemical separation, its near-neighbor: isotopes of an element are chemically identical, so no reaction can sort them, and separation must instead exploit the tiny differences in mass that alter reaction rates, diffusion speeds, and vapor pressures. That is why isotope separation is industrially hard — each pass through a separating stage enriches only slightly, and useful purity demands cascades of many stages.
Fusion's fuel supply rests on three separations. 📝Deuterium, one atom per 6,700 of hydrogen in seawater, is extracted at scale by processes such as the Girdler sulfide exchange, making it cheap and effectively inexhaustible. 📝Lithium-6, the isotope that breeds well from slow neutrons, historically came from the mercury-based COLEX process, which no Western facility has run since the 1960s — a supply-chain gap the fusion industry must close before breeding blankets are built in numbers. And inside the plant itself, hydrogen isotope separation by cryogenic distillation continuously sorts protium, deuterium, and 📝tritium in the exhaust stream so that pure fuel returns to the 📝plasma.