OSNews

The liquid Th232 is fertile so it needs to be bred to Protactinium and then to U235 by adding a small starter source of slow thermal neutrons from a fissile material like U232, U235 or Pu239 which could come form weapons or power plant wastes. Or you could just use a neutron beam powered by protons hitting lead, an energy amplifier.

Once it starts, Th232 => Prot => U235 => fission energy + moderated slow thermal neutrons and back to more Th232 => Prot => U235 .......

The loop gains is 2 or so but is self moderated back by the fluoride salt.

There is only a tiny amount of U235 in the loop at any time, it breeds itself as it follows the load slowly but surely consuming the Th232 and replacing it with the fission products of the self procreating U235. Just 1 ton of Th232 gives 3GW/yr thermal power and 1 ton of interesting waste, (almost 1 ton, remember e=mcc).

See Kirk Sorenson for the story.

In Fukushima the reactor did shut down properly, but had no extra water from the backup deisel to cool the reactor with, hence the chain of events.

The LFTR is completely self moderating for load and if it overheats it shuts down by melting its own bath plug. As it drains it cools in a few hours since it is always in liquid fluoride salt form. No emergency devices or computers or people or power needed. To restart, heat the bath tub/pan and start the pumps up. The heat from the tiny amount of U235 in the salt is exchanged with a steam or helium or CO2 turbine.

Modern passive Uranium designs like the AP1000 will copy some of the same ideas but really most active reactors are an accident waiting to happen with probability in the 1 in 1000..s of years per site unless they are passive by design. A few active reactors is safe, but 1000s of them is begging, so the next generation must all be passive by design and I'm sure they will be. Even better if the LFTR would replace the U235 cycle as it is maybe 100* more efficient with the fuel.