Helium-3 - Production

Production

Current US industrial consumption of Helium-3 is approximately 60,000 liters per year; cost at auction has typically been approximately $100/liter although increasing demand has raised prices to as much as $2,000/liter in recent years. Helium-3 is naturally present in small quantities due to radioactive decay, but virtually all helium-3 used in industry is manufactured. Helium-3 is a product of tritium decay, and tritium can be produced through neutron bombardment of deuterium, lithium, boron, or nitrogen targets. Production of tritium in significant quantities requires the high neutron flux of a nuclear reactor; breeding tritium with lithium-6 consumes the neutron, while breeding with lithium-7 produces a low energy neutron as a replacement for the consumed fast neutron.

Current supplies of helium-3 come, in part, from the dismantling of nuclear weapons where it accumulates, however the need for warhead disassembly is diminishing. Consequently tritium itself is in short supply, and the US Department of Energy recently began producing it by the lithium irradiation method at the Tennessee Valley Authority's Watts Bar reactor. Substantial quantities of tritium could also be extracted from the heavy water moderator in CANDU nuclear reactors.

Production of helium-3 from tritium at a rate sufficient to meet world demand will require significant investment, as tritium must be produced at the same rate as helium-3, and approximately eighteen times as much tritium must be maintained in storage as the amount of helium-3 produced annually by decay (production rate dN⁄dt from number of moles or other unit mass of tritium N, is N γ = N (ln 2)⁄t_½ where the value of t_½⁄(ln 2) is about 18 years; see radioactive decay). If commercial fusion reactors were to use helium-3 as a fuel, they would require tens of tonnes of helium-3 each year to produce a fraction of the world's power, requiring substantial expansion of facilities for tritium production and storage.