Thorium is the way to go. You have to really mess things up on purpose to have a radioactive meltdown with a thorium reactor.
Well, that’s a relief.
Thorium isn't a reactor fuel. thorium-232 is a fertile isotope that can absorb a neutron become thorium-233. Thorium-233 then decays by beta (electron) emission to become protactinium-233 which decays by beta emission to become uranium-233. The uranium-233 is then used to "fuel" the reactor. The Molten Salt Reactor design discussed in the article is a Thorium-Uranium breeder reactor. Its relative insensitivity to "melt down" is the molten salt coolant and solvent for the fuel and seed material. Although the Molten Salt Reactor Experiment (MSRE) demonstrated proof of concept there was a serious problem identified for long term operation. Fluoride induced inter granular stress corrosion in the Hastelloy N alloy used in the MSRE. Also the time for the production of usable amounts of U-233 is considerably longer than the similar uranium-238 to plutonium 239 production in Liquid Metal Fast Breeder Reactors (LMFBR).