Thorium: a safer nuclear power

In the same month as the Three Mile Island and Fukushima nuclear disasters, China announces it is speeding up its research into so-called molten salt reactors that can run on thorium.  If it succeeds, it would create a cheaper, more efficient, and safer form of nuclear power that produces less nuclear waste than today's uranium-based technology.

April may have the been the “cruelest month” for T.S. Eliot, but March may hold that claim for the Japanese and American nuclear industries, where two high-profile accidents – Fukushima and Three Mile Island – have etched themselves in collective memory and distrust (read more here and here). 

Such accidents could become a thing of the past if the nuclear industry can wean itself off of uranium and embrace thorium, which is more abundant, less melt-prone, and therefore safer to use. China last week announced it was going to speed up its research and development of "fourth generation" so-called molten salt reactors that can run on thorium. It aims to have one operational in 10 years instead of 25 years – what those in the industry call the nuclear-power equivalent of a moonshot. If it succeeds, nuclear power would become more efficient, cheaper, and safer than today’s uranium-based reactors. It would also produce less nuclear waste.

 “If China is building molten salt reactors, it will be a push in the right direction for all other nations not to be left behind,” says David LeBlanc, a molten-salt reactor expert with Terrestrial Energy in Canada, in an interview. “China is starting from scratch, however, and while it can certainly accelerate its program, it won’t happen overnight.”

India and, to a lesser extent, Canada are also pursuing the technology. The United States is working with national agencies to bolster Chinese research, so its embrace of thorium technology will depend in part on Chinese success. But the US still relies on second-generation light-water, solid-fuel reactors that operate, on average, at more than 90 percent capacity. Georgia-based Southern Company and South Carolina-based SCANA are building third-generation light-water reactors that are more efficient and safer. But most of those plants are going up in China and India.

Fourth-generation reactors are just on the drawing boards. Theoretically, they will be even more efficient than third-generation union with the potential to produce more electricity at less cost. They operate at much higher temperatures but at lower pressures than third-generation reactors. Thorium is better suited to run them than uranium because it has a higher melting point. That substitution would minimize the danger of a meltdown at the reactor’s core, which happened partially at Three Mile Island and wholly at Fukushima.

There are reasons for skepticism.  Critics say that it is still difficult to maintain high thermal efficiencies, which diminishes the economic case for those fourth-generation reactors over today’s technologies. At this point, a thorium-fueled system is costlier than a uranium-fueled one. Also, the thorium fuel cycle still makes radioactive material that must be warehoused, and some say it does produce an isotope of uranium that could be used in nuclear weapons, although the byproduct is not plutonium, which is the main component for an atomic bomb.

“In 30 to 50 years, I can see a move away from light-water reactors to molten-salt reactors because they have a safer cycle,” says Tom Drolet, a Florida-based nuclear-energy expert and energy consultant, in an interview. “Thorium is also the most abundant nuclear resource on earth.”

The US, however, will find it difficult to transition to thorium because of its cold-war decision to invest in uranium fuels, which could be more easily enriched to make nuclear bombs. Even if there is a breakthrough in thorium technology, it would be too costly to retrofit America’s existing nuclear energy infrastructure. The supply chain is now fully stocked and includes everything from uranium suppliers to reactor designers.

Uranium supplies can feed the current reactor fleet, says David Martin, deputy director of research for the Weinberg Foundation in London, in an e-mail. But if nuclear energy should undergo a renaissance and the need for that fuel stock would increase as a result, it would only underscore the need for fourth generation molten salt nuclear reactors that use thorium.

“China's ambition is far-sighted,” he says. “This announcement should cause Western governments to end their de facto shutdown of nuclear R&D and massively increase investments in advanced reactors.”