I have generally been quite a skeptic about thorium as a source of nuclear fuel. Although I know that thorium was tried in the fuel at two very early commercial power reactors in the United States (Elk River, and Indian Point-1), the idea did not take off. The proposals to use thorium in fluid fuel reactors were far less successful, with none moving beyond the prototype stage. Even given the low success rate, it still remains that the use of thorium is promising.
Thorium itself isn't fissile, because it can't itself be split to produce energy. However, if it is bombarded by neutrons then after a decay process it produces a fissionable isotope of uranium. So, it is called "fertile" rather than "fissile," and it is fairly abundant. There are many millions of metric tons of it around, and it's not being used for much.
So today, at the ANS 2014 Winter Meeting, I attended the "Thorium Resources, Recovery, Fuels and Fuel Cycles" session in order to see for myself what the cutting-edge thinking might be on using this apparently abundant, but now-all-but-abandoned, nuclear fuel. The efforts and papers put forth were brilliant, and my view has changed.
The leadoff paper, Thorium Recovery from Rare Earth Element Deposits in the US (Bradley Van Gosen, Steven Krahn, Timothy Ault) first showed us that thorium is very abundant right here in the United States. There are in fact several operations underway right now that can supply it, and that is because thorium is found in the same place where rare earth elements are found. Thorium is tossed aside as a radioactive nuisance. According to the paper's authors, since the material is already being pulled from the ground, and if and when a thorium fuel cycle for nuclear reactors develops, then it can piggyback on the existing rare earth mining operations. That is a concept that could significantly reduce the capital cost of the fuel cycle. Furthermore, if the thorium is recovered from mine tailings already dumped, it can help toward what would normally be considered remediation of a mining site. In other words, what was once perceived as hazardous waste cleanup, would still be viewed as hazardous, but also as a fuel source.
The presentation detailed a number of mining operations, both underway and planned in the US, from which thorium could be obtained if required. However, it noted that major hurdles face this particular prospect. For example, the present thorium market is small, and there is zero market for fuel; no government subsidies exist either. No present facility exists to separate the thorium from the mine tailings; if one did, it would need complicated permitting to stockpile concentrated radioactive material.
These observations made the next presentation all the more important. "Environmental Impact of Thorium Recovery from Titanium Mining in North America" was delivered next, out of order due to a schedule problem (authored by Timothy Ault, Steven Krahn, Allen Croff, Raymond Wimer). It pointed out that there is an enormous demand for titanium worldwide, far higher than for rare earths (primarily in white paints) and that where you find titanium, you also find thorium. In fact, there are dozens of possible titanium (and thorium) mining sites in the US Piedmont Region, beyond the ten or so already operating there. While the process to separate the thorium from the basic ore would require very large amounts of not only water, but chemicals too, it requires no new materials or processes to be developed that aren't already in existence. Further, the cost of the process could be driven down if other rare earths essentially sloughed off from this process were sold as commodities. Thus, the production of thorium from already existing titanium mining is far more attractive than simply finding other ores in the ground and starting a mine from scratch or even remediating rare earth mine tailings. This essentially moves that first step of the thorium fuel process from the "where, and how" phase to the "here, and here's how" phase.
In fairness the paper's authors did detail that the thorium fuel process done this way does have a relatively high radiation dose rate -- primarily at the first step where the original ore, called Monazite, is broken down to extract the thorium. This is because of radioactive Radium-228, which then follows the rare earths through the process. However, titanium mines here and in Canada already have some processing facilities nearby (although not for nuclear fuel) and have very sufficient transportation infrastructure. After hearing these arguments, I myself became convinced that thorium might not be that hard to come by after all as a fuel source, and we know how to deal with radioactive materials quite well enough. One person at the session did speak up and point out that the more or less mainstream thorium messaging constantly points out that it's about four times more plentiful than uranium, but that this messaging ignores the fact that thorium is also distributed exceedingly sparsely around the world in small concentrations over large areas. This makes economic recovery of thorium as a fuel a problem, unless you piggyback the process on something already existing, such as mining titanium.
The next paper is at the ANS Winter Meeting session is what really convinced me that this material could actually be used in commercial nuclear fuel, in my lifetime. Saleem Drera of Thor Energy (a small company of 20 people) delivered a paper on his company's efforts to develop commercial nuclear fuel, already well underway, which uses thorium and which can be burned in, and licensed in, present light water reactors.
Thor Energy is already testing fuel pellets of a number of designs in the Halden Research Reactor in Norway. The company's theory is that the introduction of thorium should be "evolutionary, not revolutionary" and should start with the present design of reactors (both boiling water reactors and pressurized water reactors) that will be the mainstay of commercial nuclear power worldwide for at least the rest of the 21st century. To that end, it's already testing fuel pellets made in its own small lab setup in the Halden Research Reactor in Norway, with excellent results. The company feels that its fuel design could actually allow any reactor in which it is used to receive a power uprate. That is an important point for a utility trying out a new fuel, since the profit margin will be higher. The company's second run of test fuel pins will be put in the same reactor in 2015. A good deal of the presentation was given to the actual process for manufacturing the fuel, but what is important is that right now we have fuel pins that will work in conventional existing reactors under test.
The final paper presented at the meeting was written by Gonghoon Bae and Ser Gi Hong of Kyung Hee University, South Korea. It was an exceedingly technical review of a new, small, light water reactor core design that can burn what we call TRU or transuranic materials. These are the worst of the materials in spent nuclear fuels, and there have been many attempts over the years to develop reactors that can burn them up. This South Korean group has developed a small (308 MW thermal) reactor, a light water-cooled moderated reactor. It uses a special, graphite-stainless steel neutron reflector and specially developed fuel, including thorium, that can actually burn up a very high percentage of TRU material. The reactor is planned to operate on a four and a half year fuel cycle, and can burn up 25 percent of the transuranics inserted into the core and/or generated in it during operation; part of the fuel includes reprocessed TRU material.
South Korea, however, is now reaching a choke point when it comes to storing spent nuclear fuel. Currently it is working on building a small, light water-cooled and moderated and partly thorium-fueled reactor that can burn up the waste.
I walked out of that session convinced that I need to keep an eye on all of these development tracks. I was enthralled by the enthusiasm of those in the room presenting, and the competence of the questions from the audience. Not only was this one of the best technical sessions I've seen at any ANS meeting, it left me changed; I can see a way out for thorium now.
Will Davis is the Communications Director for the N/S Savannah Association, Inc. where he also serves as historian, newsletter editor and member of the board of directors. Davis has recently been engaged by the Global America Business Institute as a consultant. He is also a consultant to, and writer for, the American Nuclear Society; an active ANS member, he is serving on the ANS Communications Committee 2013-2016. In addition, he is a contributing author for Fuel Cycle Week, and writes his own popular blog Atomic Power Review. Davis is a former US Navy reactor operator, qualified on S8G and S5W plants.