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Is Safe, Green Thorium Power Finally Ready For Prime Time?
MrSeb writes "If you've not been tracking the thorium hype, you might be interested to learn that the benefits liquid fluoride thorium reactors (LFTRs) have over light water uranium reactors (LWRs) are compelling. Alvin Weinberg, who invented both, favored the LFTR for civilian power since its failures (when they happened) were considerably less dramatic — a catastrophic depressurization of radioactive steam, like occurred at Chernobyl in 1986, simply wouldn't be possible. Since the technical hurdles to building LFTRs and handling their byproducts are in theory no more challenging, one might ask — where are they? It turns out that a bunch of U.S. startups are investigating the modern-day viability of thorium power, and countries like India and China have serious, governmental efforts to use LFTRs. Is thorium power finally ready for prime time?"
Oh no. Nation states might do bad things using their custom designed expensive reactors.
In the production of U233 from thorium-232, it is unavoidable that one will invariably produce small amounts of uranium-232 as an impurity, because of parasitic (n,2n) reactions on uranium-233 itself, or on protactinium-233. Uranium 232 is really, really bad stuff.
The decay chain of U232 quickly yields a number of different strong gamma radiation emitters, which makes manual handling in a glove box with only light shielding (as commonly done with plutonium) too hazardous. Not only will it kill you dead, its presence will also poison your weapon yield, and it will alert anyone who cares to look exactly where your weapon site is.
The thing is, any nation (or terrorist group?) with the money and the resources needed could produce weapons more cheaply and with less risk to their workers by enriching U238 into Plutonium 239, which is much better for making weapons anyway.
I think the article is fear mongering at best. Is their a proliferation risk? Sure. An exceedingly impractical risk imho.
According to wikipedia:
Quote:
The United States detonated an experimental device in the 1955 Operation Teapot "MET" test which used a plutonium/U-233 composite pit; this was based on the plutonium/U-235 pit from the TX-7E, a prototype Mark 7 nuclear bomb design used in the 1951 Operation Buster-Jangle "Easy" test. Although not an outright fizzle, MET's actual yield of 22 kilotons was significantly enough below the predicted 33 that the information gathered was of limited value. In 1998, as part of its Pokhran-II tests, India detonated an experimental U-233 device of low-yield (0.2 kt) called Shakti V.
So it has been attempted, and seems to have badly fizzled with both efforts. The bomb makers with deep pockets have quite rightly given up in disgust. If some well funded terrorist group or nation state is going to bother with trying to make a bomb, they are going to buy or steal U239 or they will build themselves a uranium reactor, then frequently load and unload fresh fuel rods so they can extract plutonium. Nobody is likely to ever again give bomb making with U233 much additional effort.
Anybody trying to extract the Protactinium from a LFTR in the hope of making U233 will find the neutron economy is such that they simply have to load all that U233 right back into the reactor or the thing will shut down.
Uranium-233 is produced in LFTR's. It is perfectly suitable for bombs. The neat thing is that it is "easy" to separate since it is chemically different from the rest of the molten salt.
Admittedly nothing is ever easy around molten salts, especially not anything involving fluorine, but that kind of reprocessing is an integral part of how an LFTR will work. If you do not have equipment that could be repurposed to separate uranium-233, you probably do not have a commercially viable LFTR.
Finally! A year of moderation! Ready for 2019?
So there is a trope in the engineering world that the safest reactors are the ones that are confined to paper studies, or, to put it more timely, to PowerPoint slides.
Yes. Here's the original source of that, from Hyman Rickover, 1953:
"An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose. (7) Very little development will be required. It will use off-the-shelf components. (8) The reactor is in the study phase. It is not being built now."
"On the other hand a practical reactor can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It requires an immense amount of development on apparently trivial items. (4) It is very expensive. (5) It takes a long time to build because of its engineering development problems. (6) It is large. (7) It is heavy. (8) It is complicated."
Looking at the history of reactors, almost everything other than water-cooled reactors has been an operational failure. Pebble-bed reactors have pebble jams. Helium-cooled reactors leak. Sodium-cooled reactors have fires. Boiling water reactors are basically simple devices, and even they have problems. Complexity in the radioactive side of a reactor system has not worked well in practice. The environment is hostile and the required lifetime without maintenance is decades long.
Interesting article.
One unexpected finding was shallow, inter-granular cracking in all metal surfaces exposed to the fuel salt. The cause of the embrittlement was tellurium - a fission product generated in the fuel. This was first noted in the specimens that were removed from the core at intervals during the reactor operation. Post-operation examination of pieces of a control-rod thimble, heat-exchanger tubes, and pump bowl parts revealed the ubiquity of the cracking and emphasized its importance to the MSR concept. The crack growth was rapid enough to become a problem over the planned thirty-year life of a follow-on thorium breeder reactor.
So not quite as problem free and viable in the long term as you were hoping. Long term operation is in fact one of the biggest problems for thorium reactors. Even if the salt doesn't damage them the reactor vessel itself becomes highly radioactive and thus difficult to examine and maintain. Decommissioning is similarly problematic.
That's one reason no-one has built a commercial scale plant. It's a long term investment and there are many uncertainties about reliability over 40+ years, where as current designs are at least proven to mostly work at reasonable cost for that kind of lifetime.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
Wow man, chicken little much? Yes a liquid sodium reactor would react in a very violent way to a water intrusion... but the whole system isn't PRESSURIZED. The byproducts of a LFTR reactor are orders of magnitude LESS radioactive than the byproducts of a LWR, and ALL the fuel is used. None of it is left to lanquish in your vaunted zirconium steel (which by the way, are cracked and fissured by end of life due to the temp and flux in the core). The whole concept of the LFTR is it's 'safe mode' is to freeze like you intimate. You simply heat it back up to unplug the channels. The chemical separation portion of the reactor is a fairly simple and non-complex affair, unlike the current enrichment facilities for uranium processing and could easily be managed by a small group of chemists at about the level of complexity used to make freaking beer. There's also NO possibility of a 'china syndrome', and it can't go BOOM no matter what you do. If Fukishima had been an LFTR reactor we would never have even heard about it, because when the power went out, the freeze plug would melt and the entire contents of the core would have drained into the safety tank and cooled into a solid. When they were ready, you just heat it back up and start pumping again. Hell, even the quantity of reactants in the core at any one time is miniscule compared to a LWR, so even if there WERE a catastrophic event and the fissionables were released they effect would be marginal compared to the radioactive MESS you have with a plant like Fukishima. Bottom line man.. they freaking guy that owned the patent (read that as the acclaimed inventor of) nuclear power said LFTR was far better, both in efficiency and safety. And that was with 1950's tech. I imagine we could do a bit better now.
If I sound stupid, it's not me talking....