5 ms·

It’s a good system, but the main problem comes from the same source, the fact that you’re dealing with a pool of molten salt. Maintenance on a reactor vessel is

It’s a good system, but the main problem comes from the same source, the fact that you’re dealing with a pool of molten salt. Maintenance on a reactor vessel is never without challenges, but the problems with servicing a molten salt (or something like a Pb-Bi eutectic) are still a financial and practical roadblock to widespread adoption.

Blackthorn 8y ago
This more than anything else is likely the biggest reason these reactors never took off, they're certainly safer from meltdowns, but now instead of piping water we have to pipe an incredibly caustic molten salt! The challenge hasn't gone away, it's just shifted.
- Gibbon1 8y ago
  I remember reading about issues with storage of the waste from a molten salt reactor. A problem discovered was the radiation was producing fluorine gas from the metal fluorides.
  - DennisP 8y ago
    Not all MSRs use fluoride salts. At least three companies are working on fast reactors using chloride salts.
    - XMPPwocky 8y ago
      I'd prefer superheated chlorine gas to superheated fluorine gas, in the same sense that I'd rather have an angry weasel in my pants than a grizzly bear, but...
      - DennisP 8y ago
        It's not superheated if it's just slow emissions from waste, as mentioned above. A pipe leak in the reactor itself doesn't create a lot of gas. It's molten salt at atmospheric pressure. It drips out and solidifies as it cools. An advantage of MSRs is that the troublesome fission products (like iodine, cesium, and strontium) don't leak out as gases, like they do from conventional reactor cores; instead they are chemically bound in the salt.
        toufiqbarhamov 8y ago
        That’s both an upside (as you’ve described), and a downside because the already challenging environment of molten salt becomes increasingly radioactive making servicing even harder than the chemical and thermal environment of the salt make it. You also have to carefully monitor the salt, and a lot of the probes and other means of monitoring it tend to rapidly degrade in the molten salt. It’s another issue that feels like the answer involves new materials that have a much longer life in situ, so that the inevitable maintence is infrequent. It’s a very promising technology, but it isn’t mature yet.
        DennisP 8y ago
        Reactor design can also mitigate these problems. Terrestrial Energy and Thorcon use small sealed reactor cores that get replaced every few years. Moltex uses a pool design, where everything is immersed from above in a pool of coolant salt, and can be pulled out and replaced as necessary. The actual fuel is isolated in vertical rods. At least three companies use chloride salts. According to a presenter from Elysium, in the absence of water the chloride salt is less corrosive to stainless steel than water is. I certainly agree that the technology isn't mature, since we don't have any production reactors yet. But we're making good progress, especially in Canada where regulation of new nuclear technology is more rational than in the U.S.
        toufiqbarhamov 8y ago
        Canada is such an amazing contrast to the US in that area, true. I wish people here had a better understand of just how necessary nuclear power is if we want to survive to ever reach the hoped-for “clean energy future.”

Blackthorn 8y ago

This more than anything else is likely the biggest reason these reactors never took off, they're certainly safer from meltdowns, but now instead of piping water we have to pipe an incredibly caustic molten salt! The challenge hasn't gone away, it's just shifted.

Gibbon1 8y ago
I remember reading about issues with storage of the waste from a molten salt reactor. A problem discovered was the radiation was producing fluorine gas from the metal fluorides.
- DennisP 8y ago
  Not all MSRs use fluoride salts. At least three companies are working on fast reactors using chloride salts.
  - XMPPwocky 8y ago
    I'd prefer superheated chlorine gas to superheated fluorine gas, in the same sense that I'd rather have an angry weasel in my pants than a grizzly bear, but...
    - DennisP 8y ago
      It's not superheated if it's just slow emissions from waste, as mentioned above. A pipe leak in the reactor itself doesn't create a lot of gas. It's molten salt at atmospheric pressure. It drips out and solidifies as it cools. An advantage of MSRs is that the troublesome fission products (like iodine, cesium, and strontium) don't leak out as gases, like they do from conventional reactor cores; instead they are chemically bound in the salt.
      - toufiqbarhamov 8y ago
        That’s both an upside (as you’ve described), and a downside because the already challenging environment of molten salt becomes increasingly radioactive making servicing even harder than the chemical and thermal environment of the salt make it. You also have to carefully monitor the salt, and a lot of the probes and other means of monitoring it tend to rapidly degrade in the molten salt. It’s another issue that feels like the answer involves new materials that have a much longer life in situ, so that the inevitable maintence is infrequent. It’s a very promising technology, but it isn’t mature yet.
        DennisP 8y ago
        Reactor design can also mitigate these problems. Terrestrial Energy and Thorcon use small sealed reactor cores that get replaced every few years. Moltex uses a pool design, where everything is immersed from above in a pool of coolant salt, and can be pulled out and replaced as necessary. The actual fuel is isolated in vertical rods. At least three companies use chloride salts. According to a presenter from Elysium, in the absence of water the chloride salt is less corrosive to stainless steel than water is. I certainly agree that the technology isn't mature, since we don't have any production reactors yet. But we're making good progress, especially in Canada where regulation of new nuclear technology is more rational than in the U.S.
        toufiqbarhamov 8y ago
        Canada is such an amazing contrast to the US in that area, true. I wish people here had a better understand of just how necessary nuclear power is if we want to survive to ever reach the hoped-for “clean energy future.”