No, not the Marvel Comics superhero- although, Thorium is named after the Norse god often associated with the protection of humankind.
As discussed in a recent Globe and Mail opinion piece, in the dawn of the nuclear age there were two fissionable fuel sources suitable for use in the production of nuclear energy: uranium and thorium. Uranium was chosen, not because of its superior qualities as a nuclear fuel, but because it could be used to synthesize plutonium- the key ingredient of forty-five years’ worth of Mutually Assured Destruction insanity we now call the Cold War. Thorium cannot be converted to a weapons-grade fissile material with any sort of practicality, thus it was not chosen, as the military and scientific goals of early 20th century nuclear research marched in a paranoid lockstep.
Today, the world is a much different place. Energy security and safety is a much more pressing concern than the rapid proliferation of nuclear armaments (at least, in most places outside of Africa, South-East Asia, and the Middle East). And anyone versed in the field of nuclear physics can quite easily tick off the advantages that thorium has over uranium as an energy source- shorter half-life, fewer radioactive by-products, and greater energy density in its natural form. The geologists would also note a greater abundance on earth- perhaps 3 to 4 times so.
If thorium is the six million dollar man of nuclear energy, why do we still use uranium as a nuclear fuel source- even after the military agenda supporting uranium has faded? The easy answer is market momentum. And the not so easy answer is also, market momentum. For nearly fifty years, demand for uranium has created deep capital and commodities markets centred around the innovation of nuclear technologies. Starting the process over with thorium would be counter-productive to the interests of the free market and its investors. However- the nuclear industry has reached a stage of technological advancement where the substitution of thorium as a nuclear fuel would not necessarily eradicate the capital gains built on the back of uranium. Mining techniques are quite similar, the refinement of thorium is not overly complex or cost-prohibitive, and there are existing reactor designs that could utilize thorium as a fuel source with only minor modification (the most pre-eminent of such is our own CANDU reactor design).
Let’s examine the economics of thorium over uranium for a moment-
Thorium tends to exist in nature in relative high purity, whereas uranium-235 has to be enriched from it’s natural state (~0.7%) to between 4 and 5% purity in order to be used effectively for the generation of electricity in a nuclear reactor. Clearly, thorium ore has a much higher energy density than uranium ore. CERN’s Carlo Rubbia stated in an interview for the BBC earlier this year that one tonne of thorium ore could produce as much energy as 200 tonnes of uranium ore.
That’s a pretty substantial efficiency improvement. The June 2011 settled price for uranium futures contracts on the Chicago Mercantile Exchange is $57.50 ($US/pound). In other words, purchasing a short ton of uranium for June 2011 cost US$115,000. Purchasing 200 tonnes of it for the same contract period cost US$23 million.
Currently, thorium isn’t commercially traded in the volumes required for power generation- nor is it listed on any of the world’s mercantile exchanges. Around five million tonnes of natural uranium is known to be recoverable- compare that to one and a half million tonnes or so for thorium; according to data from the United States Geographical Survey. However this figure is hypothesized without any exploration activity and represents a best guess only; it is quite likely that additional deposits of thorium would be discovered with commercial exploration, as naturally-occurring thorium is more abundant in the earth’s crust than is naturally-occurring uranium.
If we assume a direct correlation in supply and demand pricing between the two metals, then a reasonable ceteris paribus free market price for thorium would be about US$77 per pound- assuming a total of 1.5 million tonnes of recoverable thorium (in a mature market, assuming equal supply capacity and market demand as that of uranium). A simplistic estimate, perhaps, but one not without merit for the purposes of this demonstration.
At US$77/pound, one ton would cost US$154,000- more than the cost of one ton of uranium. However, since the energy density of thorium ore is so much greater than that of uranium ore, the cost to produce the equivalent amount of energy with uranium would be on the order of US$23 million- as calculated above. It doesn’t take a calculator to see that the cost savings potential for using thorium as a nuclear fuel is absolutely gargantuan.
But, if you want the number… generating the equivalent energy of 200 tonnes of uranium ore with thorium ore would cost 99.33% less. Currently, the world consumes about 67,000 tonnes of uranium annually for electricity generation. Only 335 tonnes of thorium would need to be consumed to generate the same amount of electricity- meaning that this level of electricity generation could be sustainable for 4,477 years even if no additional thorium was discovered beyond what is known to be recoverable today.
There’s another important tidbit of information about thorium that makes it highly desirable for the generation of energy in a nuclear fuel cycle: the potential for catastrophic meltdown is greatly reduced, since the melting point of thorium is nearly a thousand degrees (celsius) higher than that of uranium (and since the element is unable to ‘go critical’ in the event of a power outage or natural disaster damaging a reactor). Considering recent events, I’d say that in itself is reason enough to pursue thorium-fueled nuclear power.
Sources:
- British Broadcasting Corporation
- World Nuclear Association
- New Scientist Magazine
- Chicago Mercantile Exchange
- Discovery.com Blogs [Patrick J. Kiger]
Disclosure: at time of writing, I did not own an equity position in any of the companies mentioned in this article.