While reading about them, I did some web searches and found a really good article, by the Slow Facts guy, Rob Morse. While that previous article is in an engineering magazine and written for folks with that background, the Slow Facts article is more like something you'd present to a friend who is adamantly against nuclear power. Thorium is two elements below (to the left of) Uranium in the periodic table, but is much more common; about as common as tin. It's estimated we have about a thousand year supply of Thorium in the US alone. All current nuclear reactors in this country, at least, are Uranium fission-based reactors. Comparatively, Thorium reactors:
Unlike conventional light water reactors, cooled by regular water as the name implies, they're cooled by molten fluoride salts (Liquid Fluoride Thorium Reactors - LFTRs). Molten salt baths are exotic to most folks, but are used in heat treating metals so there's over a century of industrial experience with using them safely. They are low pressure systems and since there's no steam (no water) a steam explosion is impossible. As a class, these liquid fluoride reactors are passively safe, which means the system can respond without human intervention. They can even respond to some things without intervention of any kind at all. The plant will respond properly even without an active control system. How? For example, the molten salt is cooled to keep its temperature at the desired operating point. As it heats up, the nuclear reactions slow down. That means an accident caused by loss of cooling is essentially impossible.
- Are safer
- Produce less radioactive waste, and waste that is easier to provision for
- Are easier to install, and easier to find a site for
- Can be smaller and less expensive
- Are more secure: Thorium can't be used to make a bomb
Only one reactor has ever been built that could qualify as a reactor representative of the third phase of the plan, and that was the final core of the Shippingport Atomic Power Station in Pennsylvania. The experiment was called the Light Water Breeder Reactor and involved using thorium/U-233 fuel in a repurposed pressurized water reactor. The experiment was a success and showed that just as much U-233 could be produced as was consumed.This experiment was in the early 1960s. 1960s! So why can't we build one now? The usual: regulations. Regulations have changed and no developer is going to bet the money required (a billion? hundreds of millions?) that a politician's promise is any good. Meanwhile, in the rest of the world, developing Thorium energy is a major goal in India.