Isn't this the same way fission products are removed from any spent fuels? This "spallation" you mention I'm not familiar with, do you mean
that radioactive nuclei can be shattered by neutrons and transmute to less radioactive isotopes? But can't just the opposite occur too; that stable nuclei absorb neutrons and are transmuted to dangerously radioactive ones? I know that in U235 fission a great possible number of different and dangerous fission products can result. Is Thorium fisson different in this respect? I guess what I don't understand is why is Thorium fission fundamentally different from Uranium or Plutonium fission and why should that alter the character of fission fragments left over. Is it just the nature of Thorium fission that its wastes are less dangerous?