Deuterium Abundance

Deuterium's natural concentration in water is fixed and well measured, which makes the size of the fuel reservoir straightforward to reason about.

A measured, constant ratio

The deuterium-to-hydrogen ratio in ocean water is a standard reference quantity in geochemistry. On average about 156 deuterium atoms occur for every million hydrogen atoms — close to one part in 6,400 by atom count. This ratio is stable enough that it defines an international water standard used in laboratories worldwide.

From a small fraction to a large reservoir

A small fraction of an enormous reservoir is still an enormous quantity. The world ocean holds a vast mass of water, so even at parts-per-million concentration the total deuterium inventory is measured in scales that dwarf global annual energy demand by many orders of magnitude. The fuel is dilute but effectively unlimited on any human timescale.

Why the ratio is dependable

• The ratio is set by physical chemistry, not by geology or politics
• It varies only slightly between oceans and is well characterized
• Extraction does not deplete it in any measurable way
• The same isotope is present in freshwater, though seawater is the practical source

Because the concentration is known and constant, the breeder (Hyperion) fuel plan does not rely on discovering new deposits. It relies on chemistry that already runs at industrial scale. See longevity of supply and energy density of fusion fuel.

Dilute yet inexhaustible

It can seem paradoxical that a fuel present at only parts per million is called inexhaustible. The resolution is scale: the reservoir is so large and the energy per unit of fuel so great that even a tiny concentration yields an astronomical energy content. Dilution is a separation task, not a scarcity, and the separation is routine industrial chemistry rather than exploration or mining.