Comment Re: Thorium Sanity Clause (Score 1) 174
Generally we've discovered that very high neutron fluxes (thermal, fast or a mixture of the two) in restricted volumes required for high levels of breeding in reactors and the attendant high temperatures tend to break things, cause leaks and fires and expensive shutdowns. At the same time reactors that work on the basis of moving fuel around (mostly pebble-bed designs) have not had a happy time of it even with lower neutron fluxes and larger working volumes in the core compared to out-and-out breeder designs. LFTR combines both of these iffy concepts.
Steam pipes leak all the time in light-water reactors, usually in the steam generators in the case of PWRs. This isn't a radiological problem as the cooling/moderating water isn't radioactive as it never comes in direct contact with the fuel and its waste isotopes which are ceramic pellets housed in sealed tubes. The steam loop runs at about 400 deg C or thereabouts at high pressure. In the case of LFTR and other breeder designs the coolant loop is at up to 700 deg C at which point most steel alloys have lost half their tensile strength compared to room temperature. Breeders that have broken their cooling loops in the past released molten sodium or helium but this had never came in contact with the fuel or its waste products so it was not particularly a radiological hazard. This is not the case with LFTR, of course.