Is Thorium the Nuclear Fuel of the Future?

PHOTO CREDIT: Nuclear Power Corporation of India
The Kalpakkam fast breeder reactor, near Tamil Nadu, India, is well on its way to completion by 2012. Once complete, it will usher in the second phase of India’s three-stage plan to achieve thorium-based energy independence by 2025.


Many of the reactor choices in this month’s Nuclear Redux are sure to be controversial, both in terms of what we included and what we left out. Our seven designs run the gamut, from incremental advances on existing designs to designs so new they’re barely on the drawing board.

But there’s one design that we’d surely include in a possible follow-up article (look for it sometime in 2015): By that point, it’s likely that someone will have submitted a credible design to the US Nuclear Regulatory Commission for a thorium reactor. That’s because the United States, India, Japan, and Russia (PDF) are among the countries now working on thorium reactors.

The thorium reactor has a sizeable fan base. Proponents argue that thorium provides a nuclear energy generation magic bullet: It’s clean, abundant, cheap, and safe. Now let’s quickly review each of these points.

Clean. Like all nuclear power, a thorium reactor would produce few emissions (which is not to say that nuclear power carries no caveats).

Abundant. Thorium is three to four times more abundant on Earth than uranium. “Any cubic meter of Earth, Moon or Mars has enough Th-232 to run a profligate American's energy life for several years,” says Alexander Cannara, an electrical engineer and green activist who is also an IEEE Life Member.

Cheap. Not only is thorium actually cheaper than uranium, it’s indirectly cheaper. 1) A fully functioning thorium reactor would be smaller and produce less waste. 2) In countries like China and India, where the natural abundance of thorium exceeds that of uranium, obviously the price tag for imported material would be lower.

Safe. Cannara tells us that "there are millennia of thorium atoms within easy reach, requiring no energy-intensive, proliferation-endangering 'enrichment', and no wasteful removal of delicate fuel pellets and rods before even 10 percent of their fuel is consumed."

But perhaps the most promising advantage is that a thorium reactor cleans up after itself. It eats its own waste. Proponents say the thorium reactor could function as a kind of waste disposal mechanism for plutonium and other weapons grade material, as part of its regular energy generation process. This is the miracle that proponents point to. “A Thorium-Fluoride Molten-Salt Reactor is a neutron machine that will fission down any fissile element,” says Cannara.

You’d have to be Ebenezer Scrooge himself to argue with something so amazing.

And in fact, several countries are investigating the possibility of thorium-based energy generation: India's working on an Advanced Heavy Water Reactor, Japan has the miniFuji, Russia is working on the VVER-1000 and even the United States has long term plans to experiment with commercial energy generation by thorium. Most of these plans are nebulous, but for some it’s a serious option. The country with the most specific plan is India, which has drawn up a three-stage process to rely almost entirely on thorium by 2030.

When IEEE Spectrum interviewed thorium reactor designer Ratan Kumar Sinha (who was recently promoted to director of Bhabha Atomic Research Centre, or BARC) two years ago, he explained India’s plan:

In the first stage, pressurized heavy water reactors (PHWRs)--similar to those used in advanced industrial countries--burn natural uranium. In the second stage, fast-breeder reactors, which other countries have tried to commercialize without success, will burn plutonium derived from standard power reactors to stretch fuel efficiency. In the key third stage, on which India's long-term nuclear energy supply depends, power reactors will run on thorium and uranium-233 (an isotope that does not occur naturally).

A year earlier, Sudhinder Thakur, an executive director at the Nuclear Power Corporation of India (NPCIL), told Spectrum that construction on the 500-MW fast breeder reactor, was expected to be complete in 2011. And apart from a couple of minor hiccups, that schedule is on target.

In an email update, Thakur tells me that the Kalpakkam fast breeder reactor is progressing well, with operation slated for 2012. That will take India into stage 2 of their plan. By 2020, four more such reactors will be operational.

The fast breeder reactor is only the second stage of a long-term project. “There are no defined time lines as lot of technology development, research and demonstration activities need to be completed before commercial deployment of thorium reactors for power,” Thakur told me in an email. “I think it is decades away.” First, he explains, “we need to have a significant capacity of the fast breeder reactors where thorium could be used as a blanket.” (For a good overview on what this means, read this article on thorium reactor physics at the World Nuclear Association.)

BARC's 300-MW advanced Heavy Water Reactor will test thorium as a fuel. That project is under IAEA design review, and after it obtains regulatory approval, it will take an estimated seven years to build it.
       
Thorium has always looked attractive theoretically, but it just has not taken off in countries that have adequate supplies of regular uranium. Despite the many features that recommend it, it's only really attractive for nations–like India and China—that have too little uranium and a big surplus of thorium.

Finally, there are a lot of objections to characterizing thorium as a promising nuclear fuel. I won’t get into the endless back and forth, but the gist of the arguments according to the Institute for Energy and Environmental Research (PDF) is that because Th-232 is not fissile, you need some kind of weapons-grade material to kick-start the chain reaction.

In addition, the IEER challenges the claim that the fuel for these reactors is proliferation-resistant. That’s because thorium is converted into (what IEER calls) fissile uranium-233 in the course of the reaction. “U-233 is as effective as plutonium-239 for making nuclear bombs,” according to the report.

I must note here that there are counter-arguments to these arguments and counter-counter-arguments to boot. If I listed them all it would just be turtles all the way down. Ultimately, we can argue all we want, but the proof will come in the most basic possible form—someone submitting a credible design to the US Nuclear Regulatory Commission or some analogous body. So far, that hasn’t happened. NRC spokesperson Scott Burnell told Spectrum that there “isn't anything on our radar for a thorium-based reactor at this point.”


Required Reading:

The history of the thorium reactor

The thorium reactor and other proliferation-resistant reactor designs

Why thorium is so green

Thorium power in China

Google Tech Talks remix: the Liquid Fluoride Thorium reactor

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