| Let's look at the worst possible case for molten salt reactors and imagine that somehow the reactor gets cracked wide open. With a solid-fueled reactor, you need enough fuel for 18 months (the normal refueling cycle). With liquid fuel you can add a little bit of fissionable material as often as you want, so your fuel has barely enough reactivity to keep your plant operating. With solid fuel, the fission products build up over that 18 months. With liquid fuel, three things happen: - Noble gases bubble right out of the fuel to an outgas system. You get a tank of xenon and krypton. You can take that away to secure storage as often as you like. - Some metallic fission products plate onto collectors. - The major fission products we worry about are cesium, strontium, and iodine. In conventional reactors they're gases, but in MSRs they bond very strongly into fluoride salts. Optionally we can remove them as we go. So in our imaginary catastrophe there's not enough reactivity for a big excursion, there's less decay heat than in a conventional reactor, and most of the radioactive stuff is liquid that quickly cools to solid rock. There's nothing to drive any kind of explosion, since it's all chemically stable and at atmospheric pressure. It's worth noting that Fukushima's reactor survived a 9.0 earthquake without significant physical damage. It was the loss of electric power that took it out, and that's a problem molten salt reactors don't have at all. |