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Sodium cooled reactors with graphite moderator have not become common for some reasons. There are some issues like sodium burns in contact with air, as does hot

Sodium cooled reactors with graphite moderator have not become common for some reasons. There are some issues like sodium burns in contact with air, as does hot graphite. Potential positive coefficient (unstable) states. But the pressure in the piping could be low, compared to water/steam, so maybe cost could be low and power density high. I think a lot of these plans to retrofit coal plants with nukes are quite overoptimistic. I'm ambivalent since they could be used as reasons to prop up coal plants longer. "See, we should invest in, and get some subsidy for a new steam turbine in our coal plant so it can be used with the graphite-sodium nuke that's going to replace the boiler in 15 years". But on the other hand, we need all potential, even unlikely solutions to replace coal burning.

credit_guy 5y ago
> sodium burns in contact with air Is that so? I think you are confusing air with water here. In contact with air, sodium oxidizes quickly, but it does not burn spontaneously.
- Trouble_007 5y ago
  search: 'sodium leak at nuclear reactor' @DDG : <https://html.duckduckgo.com/html?q='sodium leak at nuclear reactor' https://html.duckduckgo.com/html?q='sodium leak at nuclear r...>
  - Gravityloss 5y ago
    Good idea. "At 19:47 high temperature liquid sodium coolant at one of the three secondary heat exchangers started leaking through a broken thermometer sheath ... on the piping and it ignited on contact with air." https://onlineethics.org/cases/case-1-fire-sodium-coolant-leak-prototype-fast-breeder-reactor-monju https://onlineethics.org/cases/case-1-fire-sodium-coolant-le...
    - credit_guy 5y ago
      That's a good catch. For some reason I was thinking of room-temperature sodium, but of course the liquid sodium from sodium cooled nuclear reactors is hot, and apparently burns in contact with the air. If you read more closely though the article you linked to, you'll see that the complaint there was not the fire in particular (which caused some damage, but no radioactive leaks), but the claim of the plant operators that the plant was "absolutely safe", and the attempt of a cover-up. In other words, the safety of this plant was judged not in comparison with the safety of a conventional water-cooled reactor, but in comparison with an absurd goal of "absolute safety". When people hear the sodium can cause fire when in contact with the air, they immediately remember the spectacular explosions of sodium in contact with water. Then they assume a sodium cooled reactor is a beast that only a madman would contemplate. In reality, sodium cooled reactors are not any worse than water-cooled reactors. All reactors present various challenges, and some of the challenges faced by sodium cooled reactors will be higher, and some lower than those facing water-cooled reactors. But sodium cooled reactors have an absolutely tremendous advantage: most of the fissile material they use as fuel (be it Uranium or Plutonium) does undergo fission and creates fission products, as opposed to actinides. Bottom line: the nuclear waste from sodium cooled reactors (and all types of fast neutron reactors) is much, much more manageable than the nuclear waste of conventional nuclear reactors.
      - Gravityloss 5y ago
        If you use a steam turbines, the sodium would be potentially in contact with water easily, on different sides of the wall in the heat exchanger with a lot of surface area etc. I wonder if you used a CO2 turbine instead...
        Trouble_007 5y ago
        (circa:1957) The Sodium Reactor Experiment : https://en.wikipedia.org/wiki/Sodium_Reactor_Experiment https://en.wikipedia.org/wiki/Sodium_Reactor_Experiment Sodium-Cooled Fast Reactor : https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor

credit_guy 5y ago

> sodium burns in contact with air Is that so? I think you are confusing air with water here. In contact with air, sodium oxidizes quickly, but it does not burn spontaneously.

Trouble_007 5y ago
search: 'sodium leak at nuclear reactor' @DDG : <https://html.duckduckgo.com/html?q='sodium leak at nuclear reactor' https://html.duckduckgo.com/html?q='sodium leak at nuclear r...>
- Gravityloss 5y ago
  Good idea. "At 19:47 high temperature liquid sodium coolant at one of the three secondary heat exchangers started leaking through a broken thermometer sheath ... on the piping and it ignited on contact with air." https://onlineethics.org/cases/case-1-fire-sodium-coolant-leak-prototype-fast-breeder-reactor-monju https://onlineethics.org/cases/case-1-fire-sodium-coolant-le...
  - credit_guy 5y ago
    That's a good catch. For some reason I was thinking of room-temperature sodium, but of course the liquid sodium from sodium cooled nuclear reactors is hot, and apparently burns in contact with the air. If you read more closely though the article you linked to, you'll see that the complaint there was not the fire in particular (which caused some damage, but no radioactive leaks), but the claim of the plant operators that the plant was "absolutely safe", and the attempt of a cover-up. In other words, the safety of this plant was judged not in comparison with the safety of a conventional water-cooled reactor, but in comparison with an absurd goal of "absolute safety". When people hear the sodium can cause fire when in contact with the air, they immediately remember the spectacular explosions of sodium in contact with water. Then they assume a sodium cooled reactor is a beast that only a madman would contemplate. In reality, sodium cooled reactors are not any worse than water-cooled reactors. All reactors present various challenges, and some of the challenges faced by sodium cooled reactors will be higher, and some lower than those facing water-cooled reactors. But sodium cooled reactors have an absolutely tremendous advantage: most of the fissile material they use as fuel (be it Uranium or Plutonium) does undergo fission and creates fission products, as opposed to actinides. Bottom line: the nuclear waste from sodium cooled reactors (and all types of fast neutron reactors) is much, much more manageable than the nuclear waste of conventional nuclear reactors.
    - Gravityloss 5y ago
      If you use a steam turbines, the sodium would be potentially in contact with water easily, on different sides of the wall in the heat exchanger with a lot of surface area etc. I wonder if you used a CO2 turbine instead...
      - Trouble_007 5y ago
        (circa:1957) The Sodium Reactor Experiment : https://en.wikipedia.org/wiki/Sodium_Reactor_Experiment https://en.wikipedia.org/wiki/Sodium_Reactor_Experiment Sodium-Cooled Fast Reactor : https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor