Even nuclear energy is vulnerable to the plague of the retro – that is, old designs have been pulled up for a once-over, even a twice-over. Consider this summary, from Discover and M. Mitchell Waldrop, of a reactor that has as its fuel not a solid component, but a mixture of molten salts:
… the worldwide nuclear engineering community was beginning to get fired up about unconventional reactor designs — technologies that had been sidelined 40 or 50 years before, but that might have a lot fewer problems than existing reactors. And the beer-and-nuclear group found that one such design, the molten salt reactor, had a simplicity, elegance and, well, weirdness that especially appealed.
The weird bit was that word “molten,” says [Troels] Schönfeldt [of the Niels Bohr Institute]: Every other reactor design in history had used fuel that’s solid, not liquid. This thing was basically a pot of hot nuclear soup. The recipe called for taking a mix of salts — compounds whose molecules are held together electrostatically, the way sodium and chloride ions are in table salt — and heating them up until they melted. This gave you a clear, hot liquid that was about the consistency of water. Then you stirred in a salt such as uranium tetrafluoride, which produced a lovely green tint, and let the uranium undergo nuclear fission right there in the melt — a reaction that would not only keep the salts nice and hot, but could power a city or two besides.
Weird or not, molten salt technology was viable; the Oak Ridge National Laboratory in Tennessee had successfully operated a demonstration reactor back in the 1960s. And more to the point, the beer-and-nuclear group realized, the liquid nature of the fuel meant that they could potentially build molten salt reactors that were cheap enough for poor countries to buy; compact enough to deliver on a flatbed truck; green enough to burn our existing stockpiles of nuclear waste instead of generating more — and safe enough to put in cities and factories. That’s because Fukushima-style meltdowns would be physically impossible in a mix that’s molten already. Better still, these reactors would be proliferation resistant, because their hot, liquid contents would be very hard for rogue states or terrorists to hijack for making nuclear weapons.
It’s fascinating stuff, if this is accurate. In particular, the bit about profitably burning the nuclear waste stockpiles which currently haunt the industry has to be something to get the pulse of an environmentalist pounding; indeed, the whole thing should be exciting environmentalists, at least those who have some knowledge of how nuclear reactors work, and can distinguish between the old-style, high cost reactors, and the reactors discussed in this article. Admittedly, you have to do a lot of learning.
But I, of course, have to be careful. There is a certain hagiographic element to the story, which I notice with its mere a hand wave, a single paragraph, at the problem of the corrosive nature of molten salt. True, it’s an engineering detail, but it may be a detail the size of a mountain. You just don’t know until you put 20 years into solving it. But I worry that Waldrop may be leaving out, or be ignorant of, certain technical objections to the design, whether it be in supplies of necessary materials, corrosion, or pollution / waste peculiar to this sort of reactor.
But Waldrop makes one other point in reaction to the obvious question of why this option, if a demo installation was successfully run for a while, wasn’t pursued.
The nuclear engineering community was just too heavily committed to solid fuels, both financially and intellectually. Practitioners already had decades of experience with experimental and commercial solid-fueled reactors, versus that one molten salt experiment at Oak Ridge. A huge infrastructure existed for processing and producing solid fuel. And, not incidentally, the US research program was committed to a grand vision for the global nuclear future that would expand this infrastructure enormously — and that, viewed with 20-20 hindsight, would lead the nuclear industry into a trap.
When the managers take over, the scientists and engineers get sidelined just when they should have been making the technical evaluations without the pressure of those who had made the investments. If we do assume the molten salt reactors can be built, then we have to acknowledge that there’s a lot of environmental damage caused by that mistaken industry decision, in the form of fossil fuel pollution.
It speaks to the importance of technical evaluations unencumbered by financial and personal considerations.
