[ExI] Could Thorium solve our energy problem?

[John Clark]

On Jul 10, 2010, at 6:31 PM, Brent Neal wrote:

>> There is no way you could get complete uranium fission with the pressurized light water reactors we use today
> 
> Yes, that's correct. I also stated that you can use uranium in a molten salt reactor, where the conversion efficiency is identical to that of thorium.

Yes but the chemistry is much more complicated. If you use Uranium you need to constantly separate the Uranium from the Plutonium in the liquid fuel, but that's extremely hard complex and expensive to do because Uranium and Plutonium are chemically very similar. If you use Thorium you also need to constantly separate the Thorium from the Uranium 233 in the liquid fuel, but that's easy to do, just bubble Florine through it.

Probably if you want to go with Uranium 238 and use it all up the only practical way is to use a liquid metal fast neutron reactor, which I hate because they can change state so fast that if you make a mistake you have no time to react and you're in a world of hurt before you know what hit you; the fact that they use molten sodium as a coolant does not add to there appeal. Molten sodium burns when in contact with the air and explodes in the presents of water. After a short time in operation this hot liquid sodium becomes intensely radioactive.  And that's not just a theoretical danger, in 1996 a leak in a sodium pump destroyed the newest and largest breeder reactor in Japan, if it wasn't in a containment building it could have been a human disaster. It's already an economic disaster of several hundred million dollars.

And besides, no matter what you do if you insist on using up all the Uranium in your reactor you're going to end up with a Plutonium based economy. And I just don't like Plutonium. 

>>  if at random you picked one cubic meter of rock anywhere in the Earth's crust you would find about 12 grams of Thorium in it. if placed in a liquid Thorium reactor 12 grams would produce the energy equivalent of 37 tons of coal, enough to power one person's western middle class lifestyle for about a decade. 
> 
> This is true. You are however neglecting to account for the energy needed to extract said thorium

I don't know how much energy it would take to extract 12 grams of Thorium from a random cubic meter of rock but I doubt it's more than the energy required to give a person a middle class lifestyle for a decade. And with all the high grade Thorium deposits around it would be a very long time before we even bothered to try.

  John K Clark




> (a common layperson mistake, which leads to people believing things like corn based ethanol are good ideas) in your computation.  If the energy return is less than 10:1, then you are still disadvantaged relative to solar, geothermal, etc.  And CSP has a EROEI of as much as 100:1, depending on which solar plant you're talking about and whether its trough-based or tower-based, etc.
> 

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