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Nuclear submarines use highly enriched uranium as a fuel. That's not a practical thing to use in civilian reactors.

acidburnNSA 7y ago
You can still make that size reactor with low-enriched fuel. It just doesn't last 30 years like it does in subs. Instead, it lasts 3-5 years.
- lrem 7y ago
  That sounds like defeating the selling point of those small reactors? Can it still be cost effective with such short service cycles?
  - akvadrako 7y ago
    I don’t think he means the plant needs to be rebuilt, just that the fuel doesn’t last as long.
    - lrem 7y ago
      Right, but the sales pitch I've seen somewhere (probably here) was pretty much "bury one in your back yard and enjoy free electricity for your community for decades" (two decades, if I remember correctly). This does not fit here, I'm just trying to reconcile.
  - jabl 7y ago
    Big civilian reactors refuel every 12-18 months, roughly. No reason why smaller reactors couldn't do the same. Very long refueling cycles make sense for stuff like remote areas etc., but for "normal" stuff where the thing is connected to a grid with a lot of other generators there's not that much value in it.
  - acidburnNSA 7y ago
    Well, small reactors have never been cost effective. In the 1950s we built lots of small reactors and they were terribly cost ineffective. We scaled up specifically to make them cost effective. Today pro-small nuclear people are thinking economies of mass production can beat out economies of scale. Having read a lot of the history on this topic I don't think we quite know how to make this happen yet. What we know works is economies of scale + economies of mass production, like when France decarbonized their entire electric grid by standardizing on large PWRs and building 58 of them in 15 years.
jabl 7y ago
US (and British, but they apparently use US tech so it's the same) submarines run on weapons grade uranium. Other nations use less enriched. France runs on 7%, Russia apparently 30-40% enriched. But yes, there are certainly other reasons too why submarine reactors wouldn't be a sensible choice for civilian use.

You can still make that size reactor with low-enriched fuel. It just doesn't last 30 years like it does in subs. Instead, it lasts 3-5 years.

lrem 7y ago
That sounds like defeating the selling point of those small reactors? Can it still be cost effective with such short service cycles?
- akvadrako 7y ago
  I don’t think he means the plant needs to be rebuilt, just that the fuel doesn’t last as long.
  - lrem 7y ago
    Right, but the sales pitch I've seen somewhere (probably here) was pretty much "bury one in your back yard and enjoy free electricity for your community for decades" (two decades, if I remember correctly). This does not fit here, I'm just trying to reconcile.
- jabl 7y ago
  Big civilian reactors refuel every 12-18 months, roughly. No reason why smaller reactors couldn't do the same. Very long refueling cycles make sense for stuff like remote areas etc., but for "normal" stuff where the thing is connected to a grid with a lot of other generators there's not that much value in it.
- acidburnNSA 7y ago
  Well, small reactors have never been cost effective. In the 1950s we built lots of small reactors and they were terribly cost ineffective. We scaled up specifically to make them cost effective. Today pro-small nuclear people are thinking economies of mass production can beat out economies of scale. Having read a lot of the history on this topic I don't think we quite know how to make this happen yet. What we know works is economies of scale + economies of mass production, like when France decarbonized their entire electric grid by standardizing on large PWRs and building 58 of them in 15 years.

jabl 7y ago

US (and British, but they apparently use US tech so it's the same) submarines run on weapons grade uranium. Other nations use less enriched. France runs on 7%, Russia apparently 30-40% enriched. But yes, there are certainly other reasons too why submarine reactors wouldn't be a sensible choice for civilian use.