Khand-e mentioned that I should share my thoughts on thorium reactors in my primer on nuclear energy. I swear I'm still working on the primer; it's 2,800 words and climbing; about halfway through the outline.
So, seeing as that's a ways off, I thought I would explain my reservations about thorium power. You may want to watch Kirk Sorensen's presentation on liquid fluoride thorium reactors.
Nuclear fission relies on splitting actinide atoms. There are two actinides which occur naturally on Earth; uranium and thorium. Uranium on earth is about 99.3% uranium-238, and about .7% uranium-235. Except for the tiniest trace amounts, all thorium on Earth is thorium-232. Of these three naturally occurring actinides, only uranium-235 is fissile; that is, only it can sustain a nuclear fission chain reaction.
However, uranium-238 and thorium-232 can be transmutated, or bred into plutonium-239 and uranium-233, respectively, which are man-made fissile isotopes.
There's my first beef right there; it's very slick marketing to claim that thorium, which relatively few people have heard of or have any familiarity, will allow all these nifty reactor design features, but with one exception it doesn't. This is because thorium must be bred into uranium before it will sustain a nuclear chain reaction! Therefore, cool tricks like liquid fluoride cores don't require thorium fuel cycles. Uranium-235 and uranium-233 have identical chemical properties, and the only molten-salt reactor ever built initially used familiar uranium-235 as fuel.
In fact, the only thing that thorium lets you do that can't be done with conventional uranium fuel cycles is the creation of a thermal breeder reactor. Now, I don't want to downplay that; that's pretty damn nifty. Combining the simplicity of a thermal neutron nuclear reactor with the capacity to breed fuel is very slick and useful itself. Kirk Sorensen never mentions it in his presentations on the LFTR concept because his audience is a bunch of fucking peasants who have no idea what the difference between thermal neutrons and fast neutrons is.
That is the biggest problem with how Kirk Sorensen is evangelizing the LFTR; he's sullying himself with the stench of ignorant peasants, routinely coming into contact with the disgusting little vermin and sullying his credibility. Even his blog, where he actually does a pretty good job of addressing some of the more technical problems with the LFTR design, is a writhing hotbed of peasant-speak:
"In nuclear engineering, the fancy term for this feature is the average logarithmic energy decrement per collision. And if that’s not fancy enough, they use a funny Greek letter that looks like a squiggle to represent it. I think the letter is actually called “xi”, but I prefer to call it “squiggle” since that’s what it looks like."
By Mitra, Huitzilopochtli, Kamapua'a and all other gods of upright manly virtue have some fucking pride man! Peasants may be illiterate, sub-human slime, but they are aware of when you're talking down to them (that's why I never bother to hide it). You are not making friends by calling ξ "squiggle." You are not helping peasants to understand the math of neutron mean free travel vis a vis moderator atomic mass by calling ξ "squiggle." Kirk Sorensen, you worked for NASA and you are an aerospace engineer. You don't call ξ "squiggle" because you are retarded; you do not get to work for NASA and be an aerospace engineer if you are retarded. In fact, there are many educated people who can't be arsed to remember the Greek letters. They do not call them "squiggle" in public because it sounds retarded.
The reason he does all this embarrassing crap is that Kirk Sorensen thinks that the key to his glorious, nuclear-powered future is peasants. That's why when he talks about the loss of steam pressure in a pressurized or boiling water reactor, he doesn't mention that this actually stops the reaction cold due to the negative void coefficient of reactivity in all such designs approved for operation in the United States. Peasants don't understand what a "negative void coefficient of reactivity" is, and they would be terrified and confused if you ever mentioned the term to them. This is why he doesn't mention that higher fuel burnup can be achieved in fast neutron reactors, even though his blog betrays the fact that he is perfectly aware of their existence. He's got to keep the message simple, something that peasants can understand. Thorium = good! Old nuclear may have = bad, but thorium = good!
The tragedy of all this is that Kirk Sorensen doesn't realize that all his pandering will get him nowhere. Masses of peasants cannot be galvanized into action to change the future. Peasants are shiftless and lazy, and only too happy to wait and see what happens instead of taking action. That's why they're peasants. Peasants only join the revolution because they were forced to at gunpoint, or because the revolution was about to win anyway. Kirk Sorensen is not forcing peasants to support liquid fluoride thorium reactors at gunpoint; ergo they are useless to him.
Kirk Sorensen was, tragically, misled into believing that you can achieve great things by being nice and agreeable and inoffensive. The Carter Administration banned waste reprocessing and all the fast neutron reactors in the USA have been shut down? No problem! Using speculative thorium fuel cycles, we can get the advantages of fuel reprocessing and breeder reactors without using any of the verboten technologies! Get some grassroots support for the idea, and soon the future will have clean, cheap energy and won't suck anymore!
No, no, no. It doesn't work that way. Your enemies are hippies, and while hippies fold like tissue paper when sprayed with oleoresin capsaicin or beaten with nightsticks, an army of hippies beats an army of peasants every time. That's how useless peasants are. If this LFTR thing ever gets off the ground in a serious way (and I would be tickled if it did), hippies will emerge from the filthy mud pits whence they are bred and descend on you. They'll cherry-pick problems with your reactor design, and if that's too difficult, they'll make them up, and raise such a stink that your beautiful, thorium-powered future is strangled to death by regulatory tape before it even begins.
And that's the real reason thorium is going nowhere in the USA. Hell, that's the real reason that nothing will go anywhere in the USA, until we do something about the hippie problem.