Clean, Green, Nuclear Power?

The iconic nuclear cooling tower may have no place in the future of nuclear energy.

In 1955, Levi Strauss, then chairman of the Atomic Energy Commission, said that nuclear energy would one day be “too cheap to meter.”  A little more than a year after the Fukushima disaster and the decision to eliminate nuclear energy in Germany, it is obvious that the promise of nuclear energy has not yet been realized.  With extremely high insurance costs, high uranium costs, and increasing concern over safety, it seems safe to say that the current universal source of nuclear power, light water reactors, will never achieve Strauss’s vision of energy too cheap to meter.  But, if a small group of nuclear power enthusiasts has its way, his vision may be realized by a new source of power:  the liquid fluoride thorium reactor (LFTR).

The LFTR was first developed in the 1950s by Alvin Weinburg at the Oak Ridge National Laboratory in Tennessee.  He viewed the LFTR as a solution for many of the problems that plagued the uranium based light water reactors that were being developed at the same time.  Many of these problems still plague LWRs: they are costly, vulnerable to cooling system failures (as demonstrated by Fukushima), require substantial civilian buffer zones, and produce large amounts of radioactive waste that must be stored for several hundred thousand years. The waste LWRs produce can also be converted into weapons grade plutonium. Finally, the fuel source for most LWRs – uranium – is expensive and environmentally damaging to mine.

Weinburg saw in LFTRs a power source that had none of these problems. They are not vulnerable to cooling system failures because they are designed to operate at substantially higher temperatures. Furthermore, they are designed explicitly so that if external power is lost – as happened at Fukushima – the reaction that drives the reactor stops automatically; this is exactly the opposite of how a LWR is designed. Because LFTRs do not need the expansive cooling systems of a LWR they are also substantially smaller and, combined with the fact that their automatic shutoffs and security from radioactive explosions mean there is no need for a substantial civilian buffer zone, have a much smaller geographic footprint than a LWR. As a result, they can be located much closer to power demand and so obviate the need for extensive transmission lines. Finally, LFTRs consume a much higher proportion of their radioactive fuel than do LWRs; this results in a smaller amount of radioactive waste that cannot be converted into weapons grade plutonium and need only be stored for several hundred years. Add to these features the fact that the IAEA estimates that thorium is 3-4 times more abundant than uranium and its mining is less environmentally damaging by two orders of magnitude and it is easy to see why Kirk Sorenson and other thorium enthusiasts are so excited: thorium would appear to be the silver bullet solution to global energy problems.

This begs the question: if thorium is the perfect energy source and the technology to exploit it has existed since the 50s, why isn’t there a LFTR in every city in the world? Unfortunately, there does not seem to be a good answer to that question. Thorium enthusiasts suggest that the decision to pursue LWRs in the 50s and 60s was primarily political, not technical, and driven at least in part because LWRs produced waste that could be used in the arms race. The decision to pursue LWRs resulted in technological lock-in and the continued pursuit of LWRs because that was the existing paradigm. In its list of challenges facing thorium based reactors, the IAEA echoes this sentiment, saying that the lack of expertise and experience running thorium reactors is one of the largest challenges facing thorium. But it is not only a lack of knowledge that poses a challenge to thorium. The IAEA lists several technical and design issues that also pose obstacles to LFTR development. Two of the most important technical deficits are the absence of engineering systems that can withstand the temperatures at which LFTRs function over a long operational lifetime and a proper method for dealing with the corrosive by-products of the liquid fluoride reactions.

It is too early yet to say whether LFTRs are the silver bullet that Sorenson claims they are. Dismissing him and his fellow thorium enthusiasts as pie in the sky dreamers is also too facile. LFTRs may prove to be technically impossible on a large scale; or prohibitively expensive; or fail for some other reason. Or they may be the saviors of the global energy system. Either way, Sorenson and his fellows are a perfect example of the creative thinkers who wander the wilderness of lost ideas and return with new solutions that push humanity forward. If the wicked problems that face the planet – from over-population to global warming – are going to be solved, then we need more thinkers like Sorenson and more solutions like the LFTR.

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