Uranium was an awful decision for power generation, chosen only because it could also be used in weapons.
Thorium is a waste product in mining, and it only comes in one naturally-occurring isotope, so it doesn't need expensive enrichment like uranium.
Thorium reactors follow the U-233 decay chain, and run entirely as a liquid, low-pressure system, which can be diluted easily and, if necessary, mixed with boron for complete emergency control.
Conventional uranium fuel comes as metallic rods - which cannot be diluted. High-pressure uranium reactors should be universally retired - they are expensive and unsafe.