On 9/16/2012 12:20 AM, John Clark wrote:
On Sat, Sep 15 meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    > in the present case there is no mystery about where the CO2
    comes from and whether it's a natural cycle - it's us.

Probably, but I'm not terribly concerned about it, the increase in CO2 over the last century is really just a blip; in fact at NO time in the last 600 million years has CO2 levels been significantly lower than now and during most of that time it was about 10 times higher than now, sometimes closer to 15 or even 20. And yet life thrived. And I think people sometimes forget that CO2 is not the most important greenhouse gas, water vapor is.

    > I'm giving a talk Monday on why we should be building
    molten-salt thorium reactors to replace the burning of fossil
    fuels for electrical power.

Excellent! I think Liquid Fluoride Thorium Reactors are the best hope for replacing fossil fuels which will run out eventually. Consider the advantages:

*Thorium is much more common than Uranium, almost twice as common as Tin. And Thorium is easier to extract from its ore than Uranium. It would only take 2000 tons of Thorium to equal the energy in 6 billion tons of coal that the world uses each year. There is 120 TRILLION tons of Thorium in the earth's crust and if the world needs 10 times as much energy as we get from just coal then we will run out of Thorium in the crust of this planet in 6 billion years

* A Thorium reactor burns up all the Thorium in it; A conventional light water reactor only burns .7% of the Uranium in it, the U235.

* To burn the remaining 99.3% of Uranium, the U238, you'd have to use a exotic fast neutron breeder reactor, Thorium reactors use slow neutrons and so are inherently more stable because you have much more time to react if something goes wrong. Also breeders produce massive amounts of Plutonium which is a bad thing if you're worried about people making bombs. Thorium reactors produce an insignificant amount of Plutonium.

* Thorium reactors do produce Uranium 233 and theoretically you could make a bomb out of that, but it would be contaminated with Uranium 232 which is a powerful gamma ray emitter which would make it suicidal to work with unless extraordinary precautions were taken, and even then the unexploded bomb would be so radioactive it would give away its presents if you tried to hide it, destroy its electronic firing circuits and degrade its chemical explosives. For these reasons even after 65 years nobody has a Uranium 233 bomb in its stockpile.

*A Thorium reactor only produces about 1% as much waste as a conventional reactor and the stuff it does make is not as nasty, after about 5 years 87% of it would be safe and the remaining 13% in 300 years; a conventional reactor would take 100,000 years.

*A Thorium reactor has an inherent safety feature, the fuel is in liquid form (Thorium dissolved in un-corrosive molten Fluoride salts) so if for whatever reason things get too hot the liquid expands and so the fuel gets less dense and the reaction slows down.

*There is yet another fail safe device. At the bottom of the reactor is something called a "freeze plug", fans blow on it to freeze it solid, if things get too hot the plug melts and the liquid drains out into a holding tank and the reaction stops; also if all electronic controls die due to a loss of electrical power the fans will stop the plug will melt and the reaction will stop.

*Thorium reactors work at much higher temperatures than conventional reactors so you have better energy efficiency; in fact they are so hot the waste heat could be used to desalinate sea water or generate hydrogen fuel from water.

* Although the liquid Fluoride salt is very hot it is not under pressure so that makes the plumbing of the thing much easier, and even if you did get a leak it would not be the utter disaster it would be in a conventional reactor; that is also why the containment building in common light water reactors need to be so much larger than the reactor itself. With Thorium nothing is under pressure and there is no danger of a disastrous phase change so the expensive containment building can be made much more compact.

  John K Clark

I like this conversation! I am interested in the materials required for the vessel and the plumbing. Some kind of ceramic coated titanium or zirconium? Alumina reinforced steel <http://sbir.gsfc.nasa.gov/SBIR/abstracts/09/sbir/phase1/SBIR-09-1-A2.09-8630.html>? A quasi-crystal material coating in the interior of the pipes would be nice to minimize friction and dampen unwanted heat dissipation if such existed that was stable at high temperatures...




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