Uranium vs Thorium for Power Production (George Stanford)

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Uranium vs Thorium for Power Production: IFR vs LFTR—an Overview George S. Stanford September 2013

The possibility of using molten-salt reactors with thorium as the fertile element has captured the imagination of a number of researchers, who see the potential for thorium-based reactors to be superior to today’s uranium-based light-water reactors in several respects. This document is one person’s attempt to express concisely the essence of the thorium/uranium situation. That’s a bit of a challenge, however, since so many variations of uranium- and thorium-based reactors have been proposed, including some hybrids, that a comprehensive discussion would get hopelessly bogged down with esoteric, mind-numbing details. In this paper, therefore, one prominent example of each category of reactor has been selected for discussion: the IFR1 is considered representative of Generation-IV uranium-fueled fast reactors, and the LFTR2 is taken as typical of Gen-IV3 thorium-fueled reactors, even though currently its technology is not nearly as mature as that of the IFR. Thus we will have much-simplified view of the uranium-vs-thorium picture, under the hypothetical assumption that thorium-molten-salt technology has successfully achieved the maturity that has already been reached with uranium-based fast-reactor technology. Let’s be perfectly clear. The issue is not whether to deploy LFTRs (or some other thoriumbased technology)4 instead of IFRs or LWRs—the IFRs are almost ready, the LFTRs are not, and LWRs will probably continue being deployed for several decades at least, regardless. So if this exercise is only hypothetical, why do it at all? The intention is to try to fill the public-information gap regarding the place of the IFR in the energy picture. In the publicity being given to thorium technology’s potential, seldom, if ever is there mention of the moremature fast-reactor technology. This has had the effect of distracting attention from the need to start now to deploy the next-generation reactors that can reduce the consumption of fossil fuel, while dealing with worries about nuclear waste and weapons proliferation. The hope is that this paper will throw light on the plusses and minuses of going with the bird in the hand (the IFR) versus waiting for the one in the bush (the LFTR). The conclusions reached are summarized in tabular form at the end of the document. 1

IFR: Integral Fast Reactor, developed at Argonne National Laboratory, ~1970—1994. The program was aborted, for non-technical reasons, in1994, when it was on the verge of commercial demonstration. 2 LFTR (pronounced “lifter”): Liquid Fluoride Thorium Reactor, an extension (so far on paper only) of early work on thorium reactors (discontinued in the 1970s). 3 The reactors currently being built are considered to belong to the third generation (Gen-III). 4 Besides the LFTR, another thorium-burning concept is attracting interest. Called the DMSR (Denatured Molten Salt Reactor), some U-238 is included to “denature” the U-233. In one of its forms, it is visualized as a oncethrough, 30-year fuel cycle, with a breeding ratio of ~0.8, which makes it sort of a compromise between LWR and LFTR. For simplicity, the DMSR is not discussed further in this overview. Uranium vs Thorium for Power Production

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