7 ms·

> A notable improvement of Gen III+ systems over second-generation designs is the incorporation in some designs of passive safety features that do not require a

> A notable improvement of Gen III+ systems over second-generation designs is the incorporation in some designs of passive safety features that do not require active controls or operator intervention but instead rely on gravity or natural convection to mitigate the impact of abnormal events. > Generation III+ reactors incorporate extra safety features to avoid the kind of disaster suffered at Fukushima in 2011. Generation III+ designs, passive safety, also known as passive cooling, requires no sustained operator action or electronic feedback to shut down the plant safely in the event of an emergency. Many of the Generation III+ nuclear reactors have a core catcher. If the fuel cladding and reactor vessel systems and associated piping become molten, corium will fall into a core catcher which holds the molten material and has the ability to cool it. This, in turn protects the final barrier, the containment building. https://en.wikipedia.org/wiki/Generation_III_reactor#Developments https://en.wikipedia.org/wiki/Generation_III_reactor#Develop...

moffkalast 4y ago
The ahem warp core ejection system.
- themaninthedark 4y ago
  That's what Chernobyl had!
  - ethbr0 4y ago
    In Soviet Russia, reactor core ejects building! (Couldn't resist. Accept downvotes. I'm sorry)
    - derac 4y ago
      Honestly this is nostalgic. Reminds me of reading slashdot :)
      - ethbr0 4y ago
        It's certainly been a minute since early Slashdot. :)
  - Manuel_D 4y ago
    The key innovation is ejecting the core downward into a contained vessel, instead of upward into the sky (to be pedantic, it was the lid of the chernobyl reactor that shot upward, the core subsequently started to burn).
robotnikman 4y ago
>Many of the Generation III+ nuclear reactors have a core catcher. If the fuel cladding and reactor vessel systems and associated piping become molten, corium will fall into a core catcher which holds the molten material and has the ability to cool it. Wow, that's actually pretty cool
- p1mrx 4y ago
  I don't think it's true for the AP1000: https://inis.iaea.org/collection/NCLCollectionStore/_Public/47/078/47078912.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/... "Integrity of the Reactor Vessel is protected by surrounding it with water in the event of a threat of core melting, and therefore no core catcher is required" In other words "we don't need a core catcher because we promise to keep refilling the boiled-off water after a blackout." There are other reactor designs that can safely shut down without any human action.
  - wahern 4y ago
    According to this, https://www.nrc.gov/docs/ML1117/ML11171A340.pdf https://www.nrc.gov/docs/ML1117/ML11171A340.pdf, the two design alternatives are "dry cavity" (aka "core catcher") and "wet cavity". But the dry/wet distinction is a little misleading as according to this paper, https://www.kns.org/files/pre_paper/37/17S-854%EC%9D%B4%EC%A0%95%EC%9E%ACI.pdf https://www.kns.org/files/pre_paper/37/17S-854%EC%9D%B4%EC%A..., both alternatives require cooling water. The dry cavity design relies on indirect cooling--the water contacts the sacrificial layer ("catcher")--whereas in the wet cavity design the water directly contacts the core material, which has still effectively been "caught" in the cavity beneath the reactor vessel. I'm not sure what all the pros and cons are for each approach, except that the wet cavity design has a higher risk of a steam explosion because of the direct water contact. But this seems to be addressed by containment structures designed for higher pressures. EDIT: The succinct comparison of each approach is in the introduction to the second paper: "Some plants adopted the 'dry cavity' to enhance the spreading of the core melt on the cavity floor as well as to remove the steam explosion risk, while other plants use pre-flooding strategy to make the 'wet cavity' in order to enhance the coolability after RPV failure or to reduce the RPV failure probability."

moffkalast 4y ago

The ahem warp core ejection system.

themaninthedark 4y ago
That's what Chernobyl had!
- ethbr0 4y ago
  In Soviet Russia, reactor core ejects building! (Couldn't resist. Accept downvotes. I'm sorry)
  - derac 4y ago
    Honestly this is nostalgic. Reminds me of reading slashdot :)
    - ethbr0 4y ago
      It's certainly been a minute since early Slashdot. :)
- Manuel_D 4y ago
  The key innovation is ejecting the core downward into a contained vessel, instead of upward into the sky (to be pedantic, it was the lid of the chernobyl reactor that shot upward, the core subsequently started to burn).

robotnikman 4y ago

>Many of the Generation III+ nuclear reactors have a core catcher. If the fuel cladding and reactor vessel systems and associated piping become molten, corium will fall into a core catcher which holds the molten material and has the ability to cool it. Wow, that's actually pretty cool

p1mrx 4y ago
I don't think it's true for the AP1000: https://inis.iaea.org/collection/NCLCollectionStore/_Public/47/078/47078912.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/... "Integrity of the Reactor Vessel is protected by surrounding it with water in the event of a threat of core melting, and therefore no core catcher is required" In other words "we don't need a core catcher because we promise to keep refilling the boiled-off water after a blackout." There are other reactor designs that can safely shut down without any human action.
- wahern 4y ago
  According to this, https://www.nrc.gov/docs/ML1117/ML11171A340.pdf https://www.nrc.gov/docs/ML1117/ML11171A340.pdf, the two design alternatives are "dry cavity" (aka "core catcher") and "wet cavity". But the dry/wet distinction is a little misleading as according to this paper, https://www.kns.org/files/pre_paper/37/17S-854%EC%9D%B4%EC%A0%95%EC%9E%ACI.pdf https://www.kns.org/files/pre_paper/37/17S-854%EC%9D%B4%EC%A..., both alternatives require cooling water. The dry cavity design relies on indirect cooling--the water contacts the sacrificial layer ("catcher")--whereas in the wet cavity design the water directly contacts the core material, which has still effectively been "caught" in the cavity beneath the reactor vessel. I'm not sure what all the pros and cons are for each approach, except that the wet cavity design has a higher risk of a steam explosion because of the direct water contact. But this seems to be addressed by containment structures designed for higher pressures. EDIT: The succinct comparison of each approach is in the introduction to the second paper: "Some plants adopted the 'dry cavity' to enhance the spreading of the core melt on the cavity floor as well as to remove the steam explosion risk, while other plants use pre-flooding strategy to make the 'wet cavity' in order to enhance the coolability after RPV failure or to reduce the RPV failure probability."