[cauch]

Just a guess (I'm not the previous user), but I guess you need to look at the space _per GWh_?

If a big nuclear reactor takes 10x more space but has 20x more capacity, then it means not having much space favors the big nuclear reactor rather than building 10 small ones that will take twice more space.

(and same for the time)

[john_strinlai]

its probably my fault for not making myself clear. i mean when the available space is constrained to a specific amount of space that cannot be exceeded.

just picking random numbers:

i have 1 square mile available. a big reactor takes 4 square miles. i cannot fit a big reactor, despite the bigger reactor being more efficient.

[cauch]

well, I don't think that there is a real problem of "1 square mile is available but not 4 square miles" (this is a different sentence than "there is not enough space"). Especially as small reactor also need to be placed very specifically. So even then, it is still possible that the advantage is for big nuclear plant, as they are still more compact per GWh.

[john_strinlai]

>"1 square mile is available but not 4 square miles" (this is a different sentence than "there is not enough space").

how are these different? one is an example, one is general, but they communicate the exact same point. if you have something that requires 4 sq. miles, you cannot fit it into a place that is 1 sq. mile in size because there is not enough space to fit it.

>as they are still more compact per GWh.

i am really struggling here... if i cannot fit something large, whether the large thing is "more compact per GWh" does not matter. i only have so much physical space to work with. if its too big, its too big.

for a more easily visualized example, you cannot fit a reactor from three mile island into a submarine. efficiency doesnt come into the equation, because physical space constraints get in the way first.

[cauch]

> how are these different?

Well, if you have 1000 places of 1 square mile and 0 space of 4 square miles, the available space is 1000 square miles. If you have 100 places of 4 square miles, the available space is 400 square miles.

You cannot say that the first sentence means the same thing that the second sentence, and you cannot say that "there is not enough space" is only something you can say in the first-sentence situation and not in the second-sentence situation.

Maybe what you meant to say is not "there is not enough space", but "there is plenty of small space but not a lot of large space" (which I doubt is true in the real world: space occupancy is usually regrouped in dense areas, leaving non-dense areas).

> if i cannot fit something large ... i only have so much physical space to work with

First, the idea that, for a domestic power plant, you only have limited space, seems very unrealistic. The real world is not a submarine or a 7/11: you want your power plant at the periphery of cities, not squeezed between 2 buildings in the middle. There is only disadvantage of doing so: you cannot distribute high power lines from the middle of the city safely, you probably need facilities to deal with the fuel, probably need water for cooling, probably need a security perimeter as you have around any typical factory, the cost of the square meter is more expensive, ...

But secondly, you need the power plant to produce some power. If your country needs X GWh, and you need either 1 large power plant of 4 square miles or 10 SMR of 1 square mile and you just have few places where you can put a power plant, the "the unit itself is more compact" does not matter . I only have so much physical space to work with. If the surface needed to get X GWh using SMR is too big, it's too big.

> you cannot fit a reactor from three mile island into a submarine

Yep. Similarly, you cannot fit a SMR in a bicycle. But how is that relevant? In real life, domestic power plant do not have the constraints of being in thigh places (on the opposite, it is better for a power plant to be in regions that also happen to not have thigh places).

[john_strinlai]

>Maybe what you meant to say is not "there is not enough space", but "there is plenty of small space but not a lot of large space"

my bad, i forgot i was on HN where this type of pedantry is the national sport. it sure sucks any tiny little bit of enjoyment one might get out of having a conversation. it's evident from the rest of your comment you knew exactly what i meant.

>First, the idea that, for a domestic power plant, you only have limited space, seems very unrealistic [...] But how is that relevant? In real life, domestic power plant do not have the constraints of being in thigh places

part of the point of SMRs is to be able to have them in space-constrained places where you otherwise cannot build a large facility. that's the appeal! google and meta aren't looking at them so they can power san fransisco or the country with multiple GW. they want to power a datacenter. i can think of other examples of space-constrained places where an SMR is appealing and a traditional facility is impossible, but you've managed to kill any interest i had in having a conversation.