Deuterium

Deuterium is a heavy, stable isotope of hydrogen abundant in seawater — one half of the Kronos staged D–³He fuel cycle.

Symbol

D or ²H

Nucleus

1 proton + 1 neutron

Source

~1 in 6,400 hydrogen atoms in seawater

Role

Primary fuel; also breeds ³He via D–D

Deuterium is a stable, naturally occurring isotope of hydrogen with a proton and a neutron in its nucleus. It is abundant and cheap — extractable from ordinary water, where about one hydrogen atom in 6,400 is deuterium — so fuel scarcity is never a deuterium problem.

In the Kronos staged, catalyzed D–³He cycle deuterium plays two roles: it fuses with helium-3 in the aneutronic primary reaction, and it fuses with itself (D–D) to breed fresh helium-3 in situ. That second role is why the plant is not hostage to scarce external ³He — but it is also the source of the residual neutrons that make the plant low-neutron rather than neutron-free.