The concept of a gas-filled nuclear reactor, first discussed in the 1950s, is presently being developed for energy production. Two reactor classes, generically known as high-temperature reactors (HTRs) and very-high-temperature reactors (VHTRs) (including pebble-bed reactors), utilize graphite-moderated cores for energy production and helium as a coolant. In the nuclear reactor application, helium has the distinct advantages of (1) high heat transfer capability, (2) chemical inertness, and (3) not forming isotopes and thus not producing deleterious radiogenic by-products. Such designs are under serious consideration and development in the United States as well as in other nations, including South Africa, the Netherlands, and China. In addition to being potentially significant sources of energy, these reactors will have a critically important secondary use: as highly efficient incinerators for the disposal of surplus weapons-grade plutonium.
According to the 2007 report of the International Panel on Climate Change, the production of electricity by nuclear fuel could be a good option for mitigating greenhouse gases. Presently, approximately 16 percent of energy production worldwide derives from nuclear fission (IPCC, 2007), with production in 2005 of 2,626 TWh of energy using 65,500 tons of uranium. Nuclear reactors are being planned or proposed for China, India, Japan, Korea, Russia, and South Africa. The amount of helium needed for each reactor has been estimated at approximately 1 MMcf, with a loss rate of approximately 0.1 MMcf per year.6
While the future helium requirement for VHTR and HTR energy production has not been reliably quantified, helium consumption by this particular U.S. and global sector will increase. No ready substitutes are available, given the high temperatures and heat loads demanded by these facilities. Advanced recycling and recovery efforts might reduce estimated helium loss rates.
Because of its low viscosity and large diffusion coefficient, helium is an excellent leak detector gas and is widely used as such in science and technology. In one detection method, a vacuum pump is used to pull helium sprayed outside the system through the leak and into an extremely sensitive mass-spectrometer-based helium leak detector. This detection process is the gold standard for any industry that relies on a high vacuum, including the electronics and advanced materials industries, in scientific research, and in the testing and manufacture of large rocket engines.