What about thorium reactors?,(reply>), I'm not sure what you mean by radioactive helium. 3He and 4He are stable and all other isotopes have a life of less than a second. You might mean radioactive hydrogen, i.e. tritium.,(reply>), @ReddwarfIV<br>MSRs can work with uranium too. But thorium has other advantages, like not making plutonium.,(reply>), @Miku Chan Uranium reactors, you mean. The difference is that uranium reactors need a lot of expensive safety equipment. Theoretically, if an MSR went into a melt-down condition, the fuel would burn through a plug at the bottom of the reactor and fall into a vat of coolant or something. You then empty the vat and replace the plug, so your reactor is ready for more molten salts.,(reply>), @ReddwarfIV Fission boilers don't melt down either. At least as long as you don't turn off the safeties or get a giant tsunami showering over your plant. :),(reply>), @ThatSaneGuy Well, there's also the advantages of thorium's availability, storability, and the fact that MSRs do not melt down.