The Thorium “Dream Factory”[1]
When nuclear power was sold to a reluctant public in the 1950s, it was “safe, clean, cheap, dependable and virtually inexhaustible”. It took a few decades or longer for people to realize that these were lies. It staggers the mind that otherwise reasonable people are now falling for the same claim being made for another generation of nuclear reactors. The fact is, if it sounds too good to be true, it probably isn't true.
Those who don't know history are condemned to repeat it. Some of us are old enough to remember when Atomic Energy of Canada pursued this technology aggressively in the 1970's only to abandon it when the risk of nuclear weapons became evident. One very small thorium reactor operated for five years in the 1960's at Oak Ridge, Tennessee. There is some media buzz about the development of thorium reactors in India and China but none have yet been built. The technology to bump energy production from the 15 KW of Oak Ridge to something suitable for commercial use is just not there. Even the industry admits that were it to invest in developing the technology, it would be 30 to 40 years before large-scale energy production would happen.
The Theory: Thorium, Th-232, is lighter than uranium and about four times more widespread in nature. India has quite a bit of it. Its decay[2] is rapid with less high-level waste (defined as waste with lots of short-acting gamma emitters). A thorium reactor would act as a waste disposal unit for plutonium (Pu) and produce uranium-233 for its own use all the while boiling water to produce steam to turn turbines for the production of electricity. Furthermore, if such a reactor used a particle accelerator to fire neutrons at thorium to keep the reaction going, it could theoretically be shut down quickly simply by turning off the neutron beam.
Safety? Thorium doesn't naturally fission. Thorium is not even the actual fuel in the reactor. Thorium-232 has to be turned into uranium-233 by absorbing a neutron either fired at it by a linear accelerator or from the plutonium or uranium-235 mixed with the thorium. To refer to thorium-232 as a fuel is misleading. In fact, the plutonium or uranium used to get the thorium started needs to be “weapons grade”. In the formation of uranium-233, U-232 also gets formed. This is an intense gamma emitter and definitely not safe.
A thorium reactor would typically use a molten salt (either referred to as MSR or as hybrid LFTR) in place of conventional solid fuel design. This makes a meltdown accident impossible. However, the high temperatures required to maintain the salt both in a molten state and in continuous flow also makes it extremely corrosive; although there are elegant ways to drain the salt away, no one knows how well it can be sufficiently contained.
Clean? This cycle is not clean. It needs neutrons from another source to produce the fission cycle to get the process started. Then it is run by using protons from the uranium-233. To keep it running, the uranium-233 needs to be continually stripped of the nasty U-232 and its fission products or the process clogs up. Reprocessing, with acids and alkalis, produces large volumes of high-level liquid nuclear waste.
Recycle nuclear waste? Conventional reactors have created over 200,000 tonnes of waste so it would be a dream come true if a reactor could truly recycle that waste. However, there are actually only a few radioisotopes that can be “recycled”; they are the ones that produce neutrons. Hence the only wastes that can be recycled would be U-238 (“Depleted” Uranium), U-235 (conventional fuel still present in waste), Pu-239 and other “actinides” but these products would continue to perpetuate the “plutonium cycle”, not enter the “thorium cycle”.
Terrorist free? If the reactor is “recycling” plutonium, it has to be transported to the reactor. This step by itself would require extensive security measures. The uranium-233 produced in the reactor is itself weapons-grade material. In 1955, it was used in a bomb that was part of the USA Operation Teapot. What was done before can be done again.
Waste free? This is a most bizarre claim. Of course, thorium reactors would produce waste. Uranium-232 has a highly toxic decay chain. It must be continually removed from the molten salt in order for the energy-producing reaction to continue; otherwise, the reactor just winds down by clogging up. Nuclear fission is ultimately uncontrollable no matter what kind of nuclear reactor is moderating it. Accurately predicting the products of splitting an atom cannot be done.
Cost? One big argument against following this line of research is that it is still theoretical and would cost unbelievable sums of money to develop. None of the main companies within the nuclear industry are particularly interested without huge government subsidies – something the nuclear industry has relied upon for the last seventy years. Since it shows no advantage over our current CANDU reactors, why would one pursue it?
Conclusion: Thorium is not a source of sustainable or renewable energy. Besides generating a list of false claims, a thorium reactor, if it existed, would be, like conventional nuclear power plants, unable to connect to the “smart grid” of the future.
“With uranium-based nuclear power continuing its decades-long economic collapse, its awfully late to be thinking of developing a whole new fuel cycle whose problems differ only in detail from current versions.” Amory Lovins, March 2009.
[1] Courtesy Dr. Gordon Edwards, president of Canadian Coalition for Nuclear Responsibility (www.ccnr.org)
[2] Often there is confusion about the products of decay and those of fission. In decay, the product and the energy release during its production are always the same. Each radioactive element has a decay sequence specific to themselves. In fission, the nucleus is broken apart. There will be a host of products with varying amounts of energy. Humans cannot control decay; in nuclear power plants, the rate of fission is controlled but there is no control over the kinds or numbers of new elements formed.
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