Yay, I want more stuff to breed!
But breeding Thorium should still be less efficient than directly using it in a MSR :p
The MSR could be used as a breeder , so you feed it Thorium 232 (or Uranium 238 ), U233/U235/Pu239 (fissile element, neutron "emitter" element) and it will breed Th232 (or U238 ) into Uranium 233 (or Plutonium 239), while generating some energy through the molten salts.
Th232 and U238 by themselves can't generate energy.
MSR Breeder :
(U233/U235/Pu239) + Th232 or U238 = U233 or Pu239