Energy - Part 2: Thorium Reactors

After World War II the United States government poured a lot of money into developing nuclear power. As is the case with most new technology there were several methods being developed. We are familiar with Uranium reactors. They are the reactors used world wide. The other technology being developed at that time was a nuclear reactor based on Thorium-232. Due to a number of factors, one of which was the ability to use Uranium reactors to make materials for nuclear weapons, the Thorium reactor research was fully canceled in 1973. Another reason was light water uranium reactors worked well in submarines.

Uranium reactors can work well, but they have several major issues. They operate under pressure, so if something happens to the pressure containment vessels you get an explosion of radioactive material. Chernobyl and Fukushima are examples of this happening. Modern reactor designs have a lot of protections against this happening, but it is still a risk. Secondly, nuclear reactors operate by turning Uranium into Plutonium. Which you can make bombs out of. Now, if you want nuclear bombs that is great, but if you don't and you don't want anyone else to either that creates a new problem to manage.

Thorium reactors operate differently. They use liquid fuel instead of solid. They are not water cooled so there is not pressurized water ready to cause massive hydrogen explosions. This leads to a number of advantages for Thorium reactors.

1. They have an "strong negative temperature coefficient of reactivity." That means that the hotter the reactor gets the worse it is a running a nuclear reaction. That means that you can't overheat the reactor because if you do it begins to shut itself down. Additionally the designs developed have a salt plug that if the reactor gets too hot will automatically melt the plug and drain the fuel out into a storage tank shutting the reactor down completely. In the reactor built in the 50's the researchers would allow the reactor to overheat every Friday afternoon so the reactor would shut down for the weekend.
2. The molten fluorides used in the reactor are chemically stable and impervious to radiation. That means there is no decay due to burning or decomposition. There are no violent explosions upon contact with water or air that Uranium reactor's sodium coolant has to deal with.
3. As I said before, LFTRs operate at low pressures. Equivalent to the pressures experienced in a home water system. So no pressure explosions.
4. They are easy to control. In solid fuel reactors Xenon-135 builds up in the fuel and makes control difficult. Molten fuel reactors allow the Xenon to escape eliminating the issue.
5. Thorium reactors have very high heat capacities and the coolant and fuel are inseparable. So a large quantity of coolant will accompany any leak if one develops. Also, if an accident does happen the heat capacity can handle significant heat fluctuations.
6. The inevitable nuclear waste that comes from the Thorium process degrades to a safe level in 300 years. That's a long time, but compared to 24,000 years for Uranium reactor waste it's not long at all. The second part of that is the overall quantity of waste produced is massively less making disposal significantly easier. 
7. Making a nuclear bomb out of Thorium is basically impossible making the risk of nuclear proliferation very low.
8. Finally, Thorium is EVERYWHERE. You have thorium in your yard. Mines dump tons of the stuff as unused byproducts of their mining operations. And once you have it you don't have to do any special refining to get it ready to use. You just dump it in. Compared to the very involved processes required for Uranium that's a good deal.

All that being said, we really should develop Thorium reactors. The safety and simplicity of Thorium really should be examined. Especially given the extremely low environmental impact.