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How can deuterium be obtained from seawater?

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3D illustration of the interior reaction chamber of a tokamak fusion reactor, showing a large, cylindrical, metallic structure with curved walls and bright light panels. — fusion reactor A tokamak is a device used in nuclear-fusion research for magnetic confinement of plasma.

Deuterium is a stable isotope of hydrogen found naturally in seawater, where approximately one in every 6,760 hydrogen atoms—or roughly one in every 3,000 water molecules—is a deuterium atom.12

Because deuterium is chemically similar to ordinary hydrogen, it must be concentrated to be useful for nuclear fusion. Several industrial processes are used to extract and concentrate it from water:

Electrolysis: By passing an electric current through water, ordinary hydrogen is released more readily than deuterium. Through continued electrolysis, the remaining water becomes increasingly enriched with deuterium oxide, or heavy water.13
Fractional Distillation: This method exploits the fact that deuterium oxide is less volatile than ordinary water, allowing it to be concentrated in the liquid residue during the distillation process.14
Chemical Exchange: Processes such as the Girdler sulfide process involve exchanging deuterium between hydrogen sulfide and water to increase its concentration.14

These methods allow for the recovery of deuterium, which serves as a virtually inexhaustible fuel source for future fusion energy applications.2