6 ms·
The topic is small modular reactors, which are defined as reactors producing less than 300 MW. The Voyager RTGs generate "a few hundred watts" (https://en.wiki
by killjoywashere 7y ago
The topic is small modular reactors, which are defined as reactors producing less than 300 MW.
The Voyager RTGs generate "a few hundred watts" (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...).
The Virginia class submarines use a GE S9G, which produces 150 MWt. Power output is a mix of electric and shaft torque (https://en.wikipedia.org/wiki/S9G_reactor https://en.wikipedia.org/wiki/S9G_reactor)
The Los Angeles class submarines use a GE S6G, which produces 165 MWt (https://en.wikipedia.org/wiki/S6G_reactor https://en.wikipedia.org/wiki/S6G_reactor), power output is a mix of electric and shaft torque.
The Ohio class submarine uses an S6G, rated at 220 MWt (https://en.wikipedia.org/wiki/S8G_reactor https://en.wikipedia.org/wiki/S8G_reactor).
The Nimitz class aircraft carrier use two Westinghouse A4Ws, which produce 550 MWt each (https://en.wikipedia.org/wiki/A4W_reactor https://en.wikipedia.org/wiki/A4W_reactor). Power output is a mix of electric and shaft torque.
Chernobyl had 4 RBMK-1000 reactors which produced 3200 MWt each producing 1000 MWe (https://en.wikipedia.org/wiki/RBMK https://en.wikipedia.org/wiki/RBMK)
Hinkley Point B has 2 reactors at 2 x 1494 MWt, 2 x 655 MWe (https://en.wikipedia.org/wiki/Hinkley_Point_B_Nuclear_Power_Station https://en.wikipedia.org/wiki/Hinkley_Point_B_Nuclear_Power_...)
Fukushima has multiple reactors, mainly four 784 MWe GE BWRs (https://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Power_Plant https://en.wikipedia.org/wiki/Fukushima_Daiichi_Nuclear_Powe...).
So, you're looking pretty solidly at things on the scale of a fast attack submarine after shielding, turbine, management and maintenance systems, etc.
These are of course not on Wikipedia's list of SMR designs: https://en.wikipedia.org/wiki/List_of_small_modular_reactor_designs https://en.wikipedia.org/wiki/List_of_small_modular_reactor_...
- SECProto 7y agoNuclear submarines use highly enriched uranium as a fuel. That's not a practical thing to use in civilian reactors.
- acidburnNSA 7y agoYou 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 agoThat sounds like defeating the selling point of those small reactors? Can it still be cost effective with such short service cycles?
- akvadrako 7y agoI don’t think he means the plant needs to be rebuilt, just that the fuel doesn’t last as long.
- lrem 7y agoRight, 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 agoBig 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 agoWell, 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 agoUS (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.
- Baneofbatman 7y agoDo you know how efficiency and safety scales with power output and size? If you're building a new power plant why not just install a bunch of A4W reactors that have been well proven instead of designing and building bigger reactors?
- foota 7y agoMight be easier to monitor and control one reactor than many?
- bsder 7y ago> If you're building a new power plant why not just install a bunch of A4W reactors that have been well proven instead of designing and building bigger reactors? The naval reactors are not built to be refueled, as I understand it.
- liability 7y agoFission reactors (not RTGs) can be much smaller than an SSN. A Los Angeles class is 110m long but the Losharik is 60-70m long. And Status-6/Kanyon supposedly something like 25m by 1.5m, which is enormous for a torpedo but very tiny compared to an SSN.
- tempsolution 7y agoInteresting, wouldn't it make A LOT of sense for the US government, or any government to heavily invest in this space, since it get two flies with one stone (i.e. better energy for land AND sea AND potentially space)?
- erentz 7y agoI wondered about this myself. As another commenter pointed out naval plants use a more enriched uranium which IIRC allows them to run the reactors for 20+ years without needing to refuel. One other way of thinking about it though is that this is evidence we can have a program to make specialized small modular reactors fairly economically. So we shouldn’t be so skeptical about proposals we do it for civilian use.
- jabl 7y ago> this is evidence we can have a program to make specialized small modular reactors fairly economically. It is? I would imagine that the advantages of nuclear power for submarines are so great that militaries would gladly pay 100 times more than would be acceptable for civilian power without blinking. (I do think SMR's are promising for civilian applications, I just don't think that nuclear submarines are a good argument for the potential economic benefits.)
- erentz 7y agoWell I mean, one of the new submarines cost something like $2 billion. The reactor can’t be more than a 20% of the total cost. So no it’s not anything like 100 times more. It’s probably practically economically viable for civilian power as is. It just needs necessary modifications and housing for land based use. And permission to use the higher enrichment uranium. The fact you don’t need to refuel it for 20 years might be a bonus because the military can build them, lock them up, ship them to site, they produce power for 20 years, then they ship them back for refueling or decommissioning.
- jabl 7y ago
- pbourke 7y agoWow - you could conceivably use a Nimitz carrier to power a city.
- tonyarkles 7y agoThanks for this! I was curious to see how much power different reactors produced vs. our (Saskatchewan) current generation capacity. https://www.cer-rec.gc.ca/nrg/ntgrtd/mrkt/nrgsstmprfls/sk-eng.html https://www.cer-rec.gc.ca/nrg/ntgrtd/mrkt/nrgsstmprfls/sk-en... That says we're at around 4500MW right now, the majority of it coming from coal and natural gas (16% renewable). With a 300MW capacity per SMR, it wouldn't take too many of these to cover our base load. That page also suggests that we have 890MW worth of hydroelectric capacity, but I suspect that it only works when things are frozen? (I'm not sure why that capacity, which would be 19.6% on its own, isn't counted in the 16% renewable...)