What are the benefits/drawbacks of using thorium in nuclear power plants?


What are the benefits/drawbacks of using thorium in nuclear power plants?

In: Physics


Thorium is a by product of a lot of mining and there is a lot more of it than uranium, so it would be cheap to buy.

Thorium also produce less nuclear waste. When you use Uranium in a Nuclear reactor, you actually use two forms of uranium. In nature Uranium is less than 1% U235 and 99% U238, but for reactor you want to encrich the Uranium to get 3-5% U235, because that’s the U235 that is powering your reactor. Overtime the U235 will be spent, but most of the U238 will still remain, some will have absorbed some neutron, becoming other type of atoms that are more radioactive, it’s a big mess. But with thorium it’s different. Thorium isn’t fissible, meaning you don’t get nuclear reaction out of it. Instead it’s fertile, meaning that it can absorb a neutron, and then become fissile. So you can slowly turn Thorium isn’t fissile material and then use that fissile material for power. The end result is that you can use most of your nuclear fuel, leaving a lot less waste at the end.

Indirectly thorium allow us to use a different type of reactor that is far more safe. Molten Salt reactor use well molten salt as a coolant, instead of water that is normally used. This create two safety measure. The first is that water at those temperature is vapor and vapor expand with a lot of force. If something is wrong with your temperature control there is a risk that you can’t keep your vapor under control and explosion is a risk. The second is that with molten salt reactor they have a salt valve at the bottom of the reactor. If the temperature get too high, the salt will melt leaving the hole at the bottom open, the nuclear fuel will drop down into a emergency dump tank where it will be cooled and stop the reaction.

What are the disadvatange? Well the economics of thorium nuclear reactor are completely theorical. We don’t really know if we can make energy cheaper with this type of reactor. We would need a lot of reasearch and developpement. The industry know how to build, operate and maintain traditional nuclear reactor and each year they improve their models to get more efficient and safer reactor. Putting money into thorium reactor to develop the technology is a risky bet. With traditional nuclear reactor a lot of the initial cost of developpement were paid by governement that wanted to develop this technology for their military, we don’t have nowhere near this amount of money for thorium reactor. Add to this the fact that nuclear reactor are not a triving buisness with all the bad press and public pressure against them. Not a lot of company will be willing to spend a lot of money to develop a reactor that might not even be cheaper than current nuclear reactor.

And it’s not like the safer nuclear reactor will for sure change the public view of nuclear reactor. Nuclear power is the safest power production today and people still fear it. Nuclear is scary for people no matter how safe it actually is.

Thorium is hard to use because you have to irradiate it before it becomes usable nuclear fuel, whereas uranium can be put in reactors without pre-irradiation.

On the other hand thorium can allow breeder-reactor capabilities using slow rather than fast neutrons. This may end up being an advantage over fast-neutron breeders, but it’s unclear at this time. Breeding makes nuclear fuel long-term sustainable, lasting billions of years if it powered the entire world.