Are Thorium Reactors the Carbon-free Answer?

Let me make one thing clear from the outset. I have never been a proponent of nuclear power plants. I think there are as many different reasons to avoid them as there are to avoid eating meat. (i.e. medical, political, social, environmental, and economic)

Namely:

• They are dangerous today (e.g. Fukushima)


• The waste problem will be enormous for many tomorrows to come


• The are incredibly expensive


• They are not carbon free


• They can lead to harder stuff—like nuclear weapons


• They substitute one limited fuel for another

I strongly believe that we need to address our impending energy and climate crisis by dramatically improving efficiency and reducing demand, while at the same time bringing more and more clean and safe renewables online, preferably in a distributed manner.

But there is no guarantee that we are going to be able to navigate a smooth transition from our current wasteful, high-intensity economy to a more sustainable one on a timetable that is swift enough to adequately address our rapidly deteriorating climatic stability. As new fast-growing economies come online, pouring more and more carbon dioxide into the atmosphere, there seems to be little inclination on anyone’s part to stop for a few decades to give the atmosphere a chance to digest what’s already up there. So the CO₂ levels continue grow, even as we have already crossed the maximum safe threshold of 350 ppm.

So, despite my aforementioned bias, when a friend told me about a little-known alternative nuclear energy source, that purportedly addresses all of the above-mentioned concerns and could conceivably become widely available in a short time, I thought this might be something worth considering as an interim solution.

We could use a bridge of 20-50 years to allow our existing fossil infrastructure to be gracefully decommissioned while the new efficiency and renewable supply regime develops and matures.

The use of thorium as an energy source for nuclear power plants was first demonstrated at the DOE’s Oak Ridge National Laboratory (ORNL) in the early 1960’s. The main reason it was outgunned by uranium as the fuel of choice was because it did not produce plutonium as a byproduct, which, at the time, the DOD needed, in large quantities, to fuel our emerging nuclear weapons program.

There is widespread consensus among scientists that thorium is as “a safer, cleaner and more abundant alternative fuel,” when compared to uranium. It is less radioactive and more proliferation resistant. Its reaction in a molten-salt reactor (MSR) does produce U²³³ but that is apparently not a weapons-grade material. Thorium is about four times more abundant in nature than uranium. The largest reserves are in Australia, India, and the US.

The modern version of the MSR is the Liquid-Fluoride Thorium Reactor (LFTR). This design is considered especially safe because of its inherent properties. The reactor core is not pressurized. Any increase in temperature results in a reduction in power, thus eliminating the problematic runaway meltdown scenario. If the fluid should get too hot, a salt plug at the bottom of the tank simply melts dumping the entire mess in to a storage vessel directly below the reactor.

The waste scenario is also quite encouraging. Thorium produces about a thousand times less waste throughout the supply chain than uranium. Then it is almost entirely consumed in the reaction. Of the remaining quantity, which is quite small (I’ve been told it's  about the size of a coke can for every billion kilowatt hours), 83% is safe within ten years and the rest (17%) requires 300 years of storage before it becomes safe. While that is still a long time, it is far more manageable than the 10,000 years required for today’s spent fuel.

There are no other known issues. The technology is still unproven and questions remain about the economics and the specific turbine-generators that would mate with these reactors have yet to be designed. It is expected to cost far less than conventional reactors and  because of its simplicity, it can be scaled down to the point where one can be carried on the back of a tractor-trailer and used in a distributed manner.

Of course, if we look from life-cycle analysis perspective, thorium power, like all forms of nuclear power, is not truly carbon free. A good deal of carbon must be used in construction, transportation, maintenance and disposal. I’ve not seen such an analysis done, but it does appear to have a footprint that is considerably smaller than that of uranium.

While this technology was invented in the US, it is China and India that are pursuing its commercialization most aggressively. Earlier this year China announced its plan to press forward with Thorium at the Chinese Academy of Sciences. While the US DOE set up an international collaborative R&D initiative called Generation IV Nuclear Energy Systems, China has made it clear that, seeing the tremendous opportunity here, they intend to go it alone.

While I see a considerable niche for this technology as an interim solution, I do not believe that this or any other energy source should be considered the long term panacea to our societal challenges. Unlimited energy would only continue the trend of unlimited consumption on what is still a fundamentally limited planet. Land, water, raw materials and waste repositories will all eventually be exhausted unless we learn to curb our consumption and live within our means.

[Image credit/kmichiels/Flickr Creative Commons]

RP Siegel is the co-author of the eco-thriller Vapor Trails, the first in a series covering the human side of various sustainability issues including energy, food, and water.  Like airplanes, we all leave behind a vapor trail. And though we can easily see others’, we rarely see our own.

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