3 ms·

Note that this very different to the molten salt LFTR design. With solid fuel it is very hard to prevent protactinium capturing neutrons, which means problems f

Note that this very different to the molten salt LFTR design. With solid fuel it is very hard to prevent protactinium capturing neutrons, which means problems for breeding and waste and probably operational constraints as well. The LFTR is such a beautiful consistent design but it is very different from ordinary reactors. Also the title is inaccurate as different thorium reactors have been designed, built and operated. See MSRE and THTR-300 for example.

msandford 12y ago
I wish I had dug in further. I am substantially less excited now.
swatkat 12y ago
The one mentioned in the article is Heavy Water Reactor with Thorium fuel. Here's its whitepaper: http://www.barc.gov.in/reactor/ahwr.pdf http://www.barc.gov.in/reactor/ahwr.pdf
warfangle 12y ago
The big problem with a molten salt LFTR is the materials necessary for the plumbing. Any metal will become brittle as it is exposed to the radiation emitted from the reactor core. And manufacturing ceramics into the precision pieces called for is not a solved problem. LFTR designs are fantastic, amazing, and solve a lot of problems. There is a lot of materials science to be done to make them viable, though.
- JohnHaugeland 12y ago
  You're confusing issues from pressurized reactors with LFTRs. The reason manufacturing ceramics for pressurized reactors is hard is the pressure and size involved. LFTR can be run at normal pressure at small scale; you can use a kiln as the pressure vessel if you want to. Also, no, not any metal gets brittle; inconel and hastelloy handle radiation quite well for decades at a time, as does good old fashioned nickel. Beyond that, most reactor pressure vessels are a layer of metal then a layer of something that's really good at radiation, then the real pressure vessel, so that the interior layer's brittleness isn't very important. We built and ran LFTRs commercially in the 1950s in New York State and Pennsylvania, before computers became a commercially realistic thing. They provided our grandparents no significant technical challenge. The actual big problem with LFTR is primarily regulatory. The design hasn't been vetted to modern safety standards, which costs hundreds of millions of dollars, and the entities who are nuclear-aware and have that kind of money to throw around tend to be the existing nuclear companies, who can't switch to any other technology because they're deep in the Gilette Razor model, and anything that took out their existing fuel contracts would immediately bankrupt them. There is /zero/ materials science needed to make a LFTR. I don't know where you got that idea. They're substantially easier than what we make today. The average auto body shop can pull it off.
  - warfangle 12y ago
    >You're confusing issues from pressurized reactors with LFTRs. Nope, pretty sure I'm not. I'm well aware that LFTRs run at low (even sub-atmosphere) pressures. >We built and ran LFTRs commercially in the 1950s in New York State and Pennsylvania We never ran LFTRs commercially. If you know otherwise, please cite. I only know of two experimental reactors at the Oak Ridge facility: the Aircraft Reactor Experiment and the Molten-Salt Reactor Experiment. > I don't know where you got that idea. I got that idea from some pretty simple facts about nickel alloys (like Hastelloy N) under neutron bombardment. When you bombard nickel with neutrons, you produce helium. When the helium builds up irregularly, the alloy becomes brittle. You can dope Hastelloy N with titanium or niobium to even out the distribution of helium deposits (this is what ORNL did) but that brings the maximum temperature down to 650C. As well, tellurium (one of the fission products of a LFTR reactor) corrodes the grain boundaries of Hastelloy N. You can reduce this effect by doping it with niobium and keeping the UF4/UF3 ratio to less than 60. You have to trade off lower temperatures with whether or not you want to deal with beryllium toxicity. You can replace BeF2 with a eutectic lithium fluoride/thorium fluoride composition, but that requires an increased temperature of the reactor salts. There are other problems with using beryllium, though - it produces lithium-6, which is a strong neutron poison. You also have to filter out noble element deposits, because they don't form fluorides. There are also serious design challenges with modifying current turbines to work with supercritical CO2 or helium. You can use supercritical steam instead, but it isn't nearly as efficient. You also have to worry about tritium diffusion. It's small enough that it leaks through the heat exchangers. There are issues with the rapid expansion/contraction the graphite moderator, but some are working on graphite pebble designs. Once you throw the corrosive salts, strange reaction byproducts, and neutron bombardment into the mix, I highly doubt that 'the average body shop' could pull off the fabrication of a LFTR style molten salt reactor that could run safely for longer than a week.
    - Gravityloss 12y ago
      I was surprised to hear from GE that a CO2 working fluid power plant using turbine waste heat is a thing nowadays. They have a contractor, Echogen, who provides that part. http://www.cospp.com/articles/print/volume-14/issue-01/features/supercritical-co2-refines-cogeneration.html http://www.cospp.com/articles/print/volume-14/issue-01/featu... http://www.echogen.com/documents/why-sco2-can-displace-steam.pdf http://www.echogen.com/documents/why-sco2-can-displace-steam... In ships, when fuel costs just keep on rising, that starts making sense. (There are other reasons why it might not be good though.) On land power plants, it might make natural gas electricity more competitive against coal with this better efficiency. Though I don't see the keyword supercritical on the Echogen site yet...

msandford 12y ago

I wish I had dug in further. I am substantially less excited now.

swatkat 12y ago

The one mentioned in the article is Heavy Water Reactor with Thorium fuel. Here's its whitepaper: http://www.barc.gov.in/reactor/ahwr.pdf http://www.barc.gov.in/reactor/ahwr.pdf

warfangle 12y ago

The big problem with a molten salt LFTR is the materials necessary for the plumbing. Any metal will become brittle as it is exposed to the radiation emitted from the reactor core. And manufacturing ceramics into the precision pieces called for is not a solved problem. LFTR designs are fantastic, amazing, and solve a lot of problems. There is a lot of materials science to be done to make them viable, though.

JohnHaugeland 12y ago
You're confusing issues from pressurized reactors with LFTRs. The reason manufacturing ceramics for pressurized reactors is hard is the pressure and size involved. LFTR can be run at normal pressure at small scale; you can use a kiln as the pressure vessel if you want to. Also, no, not any metal gets brittle; inconel and hastelloy handle radiation quite well for decades at a time, as does good old fashioned nickel. Beyond that, most reactor pressure vessels are a layer of metal then a layer of something that's really good at radiation, then the real pressure vessel, so that the interior layer's brittleness isn't very important. We built and ran LFTRs commercially in the 1950s in New York State and Pennsylvania, before computers became a commercially realistic thing. They provided our grandparents no significant technical challenge. The actual big problem with LFTR is primarily regulatory. The design hasn't been vetted to modern safety standards, which costs hundreds of millions of dollars, and the entities who are nuclear-aware and have that kind of money to throw around tend to be the existing nuclear companies, who can't switch to any other technology because they're deep in the Gilette Razor model, and anything that took out their existing fuel contracts would immediately bankrupt them. There is /zero/ materials science needed to make a LFTR. I don't know where you got that idea. They're substantially easier than what we make today. The average auto body shop can pull it off.
- warfangle 12y ago
  >You're confusing issues from pressurized reactors with LFTRs. Nope, pretty sure I'm not. I'm well aware that LFTRs run at low (even sub-atmosphere) pressures. >We built and ran LFTRs commercially in the 1950s in New York State and Pennsylvania We never ran LFTRs commercially. If you know otherwise, please cite. I only know of two experimental reactors at the Oak Ridge facility: the Aircraft Reactor Experiment and the Molten-Salt Reactor Experiment. > I don't know where you got that idea. I got that idea from some pretty simple facts about nickel alloys (like Hastelloy N) under neutron bombardment. When you bombard nickel with neutrons, you produce helium. When the helium builds up irregularly, the alloy becomes brittle. You can dope Hastelloy N with titanium or niobium to even out the distribution of helium deposits (this is what ORNL did) but that brings the maximum temperature down to 650C. As well, tellurium (one of the fission products of a LFTR reactor) corrodes the grain boundaries of Hastelloy N. You can reduce this effect by doping it with niobium and keeping the UF4/UF3 ratio to less than 60. You have to trade off lower temperatures with whether or not you want to deal with beryllium toxicity. You can replace BeF2 with a eutectic lithium fluoride/thorium fluoride composition, but that requires an increased temperature of the reactor salts. There are other problems with using beryllium, though - it produces lithium-6, which is a strong neutron poison. You also have to filter out noble element deposits, because they don't form fluorides. There are also serious design challenges with modifying current turbines to work with supercritical CO2 or helium. You can use supercritical steam instead, but it isn't nearly as efficient. You also have to worry about tritium diffusion. It's small enough that it leaks through the heat exchangers. There are issues with the rapid expansion/contraction the graphite moderator, but some are working on graphite pebble designs. Once you throw the corrosive salts, strange reaction byproducts, and neutron bombardment into the mix, I highly doubt that 'the average body shop' could pull off the fabrication of a LFTR style molten salt reactor that could run safely for longer than a week.
  - Gravityloss 12y ago
    I was surprised to hear from GE that a CO2 working fluid power plant using turbine waste heat is a thing nowadays. They have a contractor, Echogen, who provides that part. http://www.cospp.com/articles/print/volume-14/issue-01/features/supercritical-co2-refines-cogeneration.html http://www.cospp.com/articles/print/volume-14/issue-01/featu... http://www.echogen.com/documents/why-sco2-can-displace-steam.pdf http://www.echogen.com/documents/why-sco2-can-displace-steam... In ships, when fuel costs just keep on rising, that starts making sense. (There are other reasons why it might not be good though.) On land power plants, it might make natural gas electricity more competitive against coal with this better efficiency. Though I don't see the keyword supercritical on the Echogen site yet...