It depends how they are designed. Same as regular uranium reactors. Thorium isn’t a reactor fuel after all, it’s what you use to breed more fuel. The actual fuel is still uranium. Thorium turns into uranium-233 then that is the fuel. Normal reactors use uranium-235. Both isotopes can be made to be passively safe.

Literally nothing you just said is correct.

That is already a thing and it’s called concentrated solar power. Basically aim a shit load of mirrors at a target to heat it, run some working fluid through the target and use that to make steam to turn a turbine. There are a few power plants that use it but in general it has been more finicky and disruptive to the local environment than traditional PV panels would be.