A U.S. company says it is getting closer to putting prototype electric cars on the road that will be powered by the heavy-metal thorium.

Thorium is a naturally occurring, slightly radioactive rare-earth element discovered in 1828 by the Swedish chemist Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. It is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium.

However, the use of thorium is controversial because, as with uranium, it is used as a nuclear power source. Indeed, the internal heat of the Earth largely is attributed to the presence of thorium and uranium.

The key to the system developed by inventor Charles Stevens, CEO and chairman of Connecticut-based Laser Power Systems, is that when silvery metal thorium is heated by an external source, becomes it is so dense its molecules give off considerable heat.

Small blocks of thorium generate heat surges that are configured as a thorium-based laser, Stevens tells Ward’s. These create steam from water within mini-turbines, generating electricity to drive a car.

A 250 KW unit weighing about 500 lbs. (227 kg) would be small and light enough to drop under the hood of a car, he says.

Jim Hedrick, a specialist on industrial minerals – and until last year the U.S. Geological Survey’s senior advisor on rare earths – tells Ward’s the idea is “both plausible and sensible.”

Because thorium is so dense, similar to uranium, it stores considerable potential energy: 1 gm of thorium equals the energy of 7,500 gallons (28,391 L) of gasoline Stevens says. So, using just 8 gm of thorium in a car should mean it would never need refueling.

Stevens’ prototype systems generate electricity within 30 seconds of firing a laser. This can feed power into a car, without the need for storage.

If his technology were to become successful on a commercial scale, one advantage would be that thorium is fairly common throughout the world. However, the distribution of thorium resources is poor because of relatively low-key exploration efforts arising out of insignificant demand.

The U.S. Geological Survey’s estimated thorium reserves in 2010 shows the U.S. leading with 440,900 tons (440,000 t), followed by Australia with 333,690 tons (300,000 t).

However, several world organizations conclude India may possess the lion's share of the world's thorium deposits, with estimates ranging from 319,667 to 716,490 tons (290,000-1650,000 t).

Natural thorium has little radioactivity, Stevens says. What isotopes there are could be blocked by aluminum foil, so the power unit’s 3-in. (7.6-cm) thick stainless-steel box should do the trick.

“The issue is having a customized application that is purpose-made,” he says, admitting that developing a portable and usable turbine and generator is proving to be a tougher task than the laser-thorium unit.

“How do you take the laser and put these things together efficiently?” he asks rhetorically. But once that is achieved, “This car will run for a million miles. The car will wear out before the engine. There is no oil, no emissions – nothing.”

Stevens says his company should be able to place a prototype on the road within two years. The firm has 40 employees and operates out of an in-house research workshop.

Hedrick, the industrial minerals expert, says 7,500 gallons is “way more gasoline than an average person uses in a year. Switching to thorium-driven cars would make the U.S. energy self-sufficient, and carbon emissions would plummet.

“It would eliminate the major need for oil,” he says. “The main (remaining) demand would be for asphalt for roadways, natural gas, plastics and lubricants.”

Stevens’ research is part of growing efforts to develop thorium as an energy source. Scientists in India, for example, long have tried to heat thorium sufficiently to cause a self-sustaining fission reaction that can run major power plants, without the nuclear waste problems of uranium-based generators. Some North American companies are doing the same thing.

Canon Bryan, CEO of Vancouver, BC, Canada-based Thorium One, knows Stevens’ work and agrees thorium-based fuel sources are “scalable and energy efficient. There’s no reason why it should not be able to power cars.”

Thorium has unique properties that make it useful as such a source, he says. For instance, it has the highest melting point of all oxides.

So if thorium would be a safe and abundant fuel source for vehicles, other devices and even power stations, why is it not being utilized widely?

Stevens, Hedrick and Bryan all have the same answer: After World War II, a strategic decision was undertaken by industrialized nations to pursue uranium-driven energy instead, because its by-product – plutonium – could be weaponized. By contrast, it is almost impossible to make a bomb out of thorium.

However, a recent International Energy Agency report accepts there is widespread interest in thorium-power sources, with research being conducted in India, Russia, Germany, France, the Netherlands and elsewhere.

The IEA notes research from Switzerland-based physics institute CERN that proposes “the use of thorium as the feed material in accelerator-driven systems, which could serve as an energy source with minimum long-term waste production,” although this is for power generation.

But there still is skepticism in the nuclear-energy research world about using thorium as a power source, especially in mobile applications.

Reza Hashemi-Nezhad, director of the Institute of Nuclear Science at the University of Sydney, Australia, says nuclear power plants already run submarines and could operate oil tankers, “but they are not small enough to fit in the boot (trunk) of a car.”

And amid widespread concerns about terrorism, would governments allow scores of nuclear sources to roam the freeways? Processed thorium can produce uranium 233 as a byproduct. Would governments allow charging an electric vehicle using radioactive material in private garages?

“Nobody will allow that to happen,” Hashemi-Nezhad says.

Hedrick thinks such concerns are overblown, stressing thorium’s by-products are very hard to turn into weapons-grade material, requiring an immense amount of work and energy.

Stevens agrees, emphasizing his system is “sub-critical,” which means no self-sustaining nuclear reaction within the thorium creating significant amounts of radioactivity. “It’s very safe,” he says.