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Thorium was discovered by the Swedish chemist Jöns J. Berzelius in 1828. He named it after Thor, the Norse god of thunder and war, because of its power. Thorium is the most efficient nuclear reactor fuel, so there have been many attempts to produce reactor fuel from thorium, including current unrelated efforts by Thorium Power and by institutes in India.

Thorium oxide has the highest melting point of all oxides, which can provide a safety benefit as a nuclear reactor fuel. Thorium is estimated to be three times as abundant as uranium, holding more untapped energy than all oil, coal, natural gas, and uranium combined, with vast reserves in the U.S., Australia, India, Canada, and many other countries. Thorium is also responsible for most of the internal heating of Earth.

Thorium is stockpiled around the world. When rare-earth elements are separated from monazite sands for use as a fuel-cracking catalyst in the petroleum industry, a by-product is thorium. Although hundreds of tons of thorium are stockpiled from this process, only small amounts are used in commercial processes and products. In the U.S., a commercial use of thorium was small quantities in the wicks of camping lanterns. I have been told that Coleman stopped this use when it found out that people were testing Geiger counters on the wicks. In addition, small quantities of various forms of thorium have been produced for nonenergy uses such as ceramics, magnesium-thorium alloys, and welding electrodes.

I first heard of thorium in 1992 from Alvin Radkowsky, who designed the thorium fuel that Thorium Power is now developing. Alvin was the original chief scientist for the U.S. Naval Reactors Program for Adm. Hyman G. Rickover, and he also headed the design team for the first nuclear power plant on land, at Shippingport, Pa. That reactor used thorium in its first core and was the first reactor under former president Dwight D. Eisenhower's Atoms for Peace program, which began 50 years ago.

When Radkowsky's former professor, Edward Teller, asked him in 1986 if he could come up with a fuel design to address proliferation concerns, Radkowsky turned back to thorium as the answer. Radkowsky passed away last year, but his work led to the fuel design now being developed and tested in Russia to dispose of weapons-grade plutonium and to stop the production of new weapons-suitable plutonium. Radkowsky spent most of his career in the U.S. Navy program during the Cold War and was amused by how times change; his technology is being tested in Russia to dispose of plutonium from warheads.

The project has been headed in Russia by academician Nikolai N. Ponomarev-Stepnoi, vice president of the Kurchatov Institute, where the first Soviet atomic bomb was developed. The work in Russia has determined that the thorium fuel design will dispose of more plutonium per year in a reactor than any other method, and current estimates are that the costs will prove to be significantly less than any other method. In addition, fuels that burn plutonium without thorium actually produce large quantities of new weapons-suitable plutonium in the spent fuel; this is not the case with thorium fuel. The fuel also results in dramatically less toxic spent fuel, with much less spent fuel for the same amount of electricity generated.

Reps. Jim Gibbons (R-Nev.) and Curt Weldon (R-Pa.) have taken up the cause of thorium fuel for plutonium disposition in Russia. They have traveled to Moscow to speak with scientists and engineers and witnessed the thorium fuel ampules in a test reactor in Moscow. These congressmen are leading the effort to secure government funding for the project.

Promising new thorium fuel technologies eventually may lead governments and the nuclear power industry to uncover the untapped energy potential of thorium for peaceful energy uses.


In a reactor with thorium fuel, some neutrons are absorbed by thorium-232 atoms, which become uranium-233. Uranium-233 is a more efficient nuclear fuel than uranium-235 or plutonium, with a high fission cross-section, a high number of neutrons released per fission (which makes it easier to sustain a critical reaction), and a high ratio of fission-to-parasitic capture. For these reasons, the thorium/uranium-233 cycle has been studied since the earliest days of nuclear power, and it has been implemented in several water- and gas-cooled reactor systems.

DIVINE JUSTICE Thor wields his mighty hammer, Mjollnir.

Seth H. Grae is president of Thorium Power, a Washington, D.C.-based company developing nuclear fuel designs to stop the production of weapons-grade plutonium and eliminate plutonium stockpiles. He holds a B.A. from Brandeis University, a J.D. from American University, and an L.L.M. and M.B.A. from Georgetown University.


Chemical & Engineering News
Copyright © 2003 American Chemical Society

Name: Named for Thor, the Norse god of thunder.
Atomic mass: 232.04.
History: Discovered in 1828 by Swedish chemist Jöns Jakob Berzelius.
Occurrence: Occurs naturally as a weakly radioactive isotope. Much of Earth's internal heat has been attributed to thorium and uranium decay. Thorium is primarily obtained from the minerals thorite and thorianite.
Appearance: Silvery white metal.
Behavior: Radioactive with a high melting point. The powdered metal is a fire hazard. The pure metal resists corrosion but tarnishes in air when contaminated with the oxide.
Uses: Used in fabricating portable gas lamps, filament wire, breeder reactor fuel, gaslight mantles, and crucibles. Thorium oxide is used as a catalyst in the production of sulf uric acid and the conversion of ammonia to nitric acid.

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