Nuclear vs wind+solar+storage American edition 1

[BridgeSmith]

The molten medium in a nuclear reactor, regardless of the type of medium, serves to transfer the heat produced by the reactor core to where it's used to produce steam. That's it. It is not the fuel. Molten salt reactors, light water reactors, etc. can be fueled by Thorium or Uranium; if I understand correctly, technically, they're all fueled by Plutonium.

Thorium reactors reactors are safer because a Thorium reaction is not self-sustaining, and requires a breeder reactor to produce the free neutrons that sustain the reaction. So, if the reactor loses power, the reaction stops and there is no core meltdown, unlike a Uranium nuclear reactor, where the reactions continue until the fuel is exhausted or removed.

Molten salt reactors can be considered safer than light water reactors, or more dangerous, depending on your perspective. The molten salt/Sodium/etc. is very toxic, and solidifies when it cools. This makes stealing materials for a nuclear weapon or a dirty bomb, virtually impossible.

Thorium fueled power plants are also apparently unsuitable for harvesting weapons grade Plutonium, which is why it was not the chosen alternative when the US started building nuclear power plants. The nuclear arms race was going full-tilt, and they needed a source of material for nuclear weapons.