Safer Than Uranium, Thorium May Become Nuclear Fuel For Power Plants

Unless you're really into trivia about gas lanterns and the mantles that make their light so bright, you've probably never heard of thorium, but you may hear a lot more about it in the future. This unassuming metal could one day rival uranium as the nuclear fuel of choice, David Szondy reported for New Atlas.

Photo Insert: Could this new discovery about thorium signal that the days of uranium in nuclear power plants be numbered?

Discovered in 1828 by the Swedish chemist Jons Jakob Berzelius, thorium is named after Thor, the Norse god of thunder. It is a slightly radioactive metal found in trace in rocks and soils all over the world and is particularly abundant in India and the state of Idaho.

Thorium has only one major isotope – 232Th – and its others only exist in minute traces. This isotope eventually decays into the lead isotope 208Pb. But what makes thorium interesting is that 232Th can easily absorb passing neutrons, turning it into 233Th.

This new isotope, in a matter of minutes, emits an electron and an antineutrino to become 233Pa, an isotope of palladium. With a half-life of 27 days, this then converts into a uranium isotope called 233U. In other words, nuclear fuel.

The challenge is to design fuels and reactors that can produce more 233U than the reactor consumes. If this can be achieved, then thorium has an advantage over uranium, which cannot produce more fuel or "breed" in a conventional reactor. It's also possible to mix thorium and plutonium into a hybrid fuel, where uranium is produced as the plutonium is consumed.

The trick is to find the optimum mix and arrangement of the fuel to handle the neutrons and their absorption. Thorium also absorbs fast neutrons, so they can be used in fast molten salt and other Generation IV reactors that are now emerging, with uranium or plutonium fuel to initiate fission – though it doesn't work as well as 238U.

A number of thorium reactors have been built since 1960, starting with the thorium-based nuclear reactor at Oak Ridge National Laboratory and a few research reactors are in operation today.

Today, thorium is seen by some as a thousand-year solution to energy and environmental problems, but one that is offset by high start-up costs and a number of technical hurdles. Part of the reason why development has been so slow is that uranium-based reactors and the infrastructure to support them had a long head start after the Second World War.

The development of liquid-metal fast-breeder reactor (LMFBR) in the 1970s seemed much more promising than thorium for commercial applications and the US government largely abandoned thorium research after 1973.

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