Comment by lazide

Thorium 232 is barely fissile - it has a net negative neutron balance during fission. Uranium-233 is similarly neutron absorbing (half the time).

So you can’t run a reactor with just Thorium 232, and maintaining a decent fuel balance can be tricky once you start due to odd fission neutron ratios between the parent fuels and daughter products and long time delays (half life wise) until you get Uranium-233. About 30 days half life.

Certainly not impossible, but pretty awkward compared to other options.