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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?"
Chernobyl was a graphite moderated water-cooled reactor. Any commercial nuclear plant in the U.S. is a water-moderated and water-cooled reactor.
Despite the normal perception of the word, a "moderator" actually increases the nuclear activity in a fission plant since it slows-down ("moderates") neutrons and therefore increases the probability that the neutrons cause a fission event. In Chernobyl, the coolant (water) was blown away in the pressure explosion, but the moderator (graphite) remained in place which led to the runaway meltdown.
By contrast at Three Mile Island & Fukushima, the loss of coolant led to a meltdown (literally heat causing melting to occur), but since the water moderator was also missing, the accidents did not lead to a runaway that was anywhere near as severe as Chernobyl. If Fukushima had included a pressure vessel of the same caliber as the one used at TMI, then hardly any radioactivity would have been released during the Fukushima accident.
AntiFA: An abbreviation for Anti First Amendment.
Weinbergs team at Oak Ridge managed to work with the Fluoride salts. They used high-nickel alloys (Hastelloy N) which were able to resist the F salts. Other manufacturers have alloys of similar make up - I believe a Czech group are developing their own at the moment due to difficulty of supply from Haynes - google MONICR. The problems are not trivial, but they are surmountable.
Prohibitive corrosion is a common misconception about this type of reactor. The U.S. built an experimental MSR in the 60's and ran it for 5 years. According to the results section of the wikipedia article about the experiment, the corrosion was negligible: http://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment#Results
The article indicates that Adm. Rickover didn't like molten salt / sodium cooled reactors because the "Navy knew how to handle water". In reality, Rickover's nuclear program tried both approaches. The Nautilus (SSN-571) used a boiling water reactor, and the Seawolf (SSN-575) used a sodium cooled reactor. Both were built, both went to sea, and both performed reasonably well. But the sodium-cooled reactor turned out to be harder to maintain than the boiling water reactor, and couldn't be run at full capacity because of some design problems. so after a year, Seawolf was returned to the yards and converted to a boiling water reactor.
That was very typical of the military approach of the period - fully develop several alternatives, operate them, then dump the losers. The history of 1950s jet fighters is a striking example.
U-232 is also produced in LFTR reactors, and is HELLACIOUSLY radioactive. You can't work around U-232 with just a glove-box - you're gonna get a tan that way. It also poisons the reaction of a U-233 bomb, so you've got to separate it out, so you're back to centrifuges and the like, and you're gonna have to throw out the contaminated and radioactive centrifuges when you're done as well.
Meldroc, Waster of Electrons