[bruce511]

Nuclear proponents argue that renewables (solar, wind) are not base-load, and nuclear is. They are correct.

But the people building power generation are doing it on a for-profit basis. Since solar is cheaper to deploy, faster to deploy, simpler to maintain and so on, that's what for-profit people build.

In other words, on the one hand you have large generators, requiring years of planning & permitting, a decade of construction, endless court battles from the anti-nuclear folks, generating returns 15 years from now, competing with the exact opposite (cheap, quick to build, beloved by eco folks, easy to run and maintain, off the shelf parts etc).

From a capital point of view its a no brainer. Capital follows profit, and solar is very profitable.

Nuclear may be good policy. Base Load may be very desirable. But unless govt is putting up the capital it just won't get funded. (Nuclear plants are being built, like in China, but using govt capital, which sees a return in more than just cash terms.)

There are lots of strong arguments for Nuclear. But Nuclear proponents need to address the capital requirements above all. Until the capital problem is solved, every other argument is useless.

[PaulHoule]

One radical answer that question which is often neglected for the facile "regulations" explanation is that we quit building coal burning power plants at the same time we quit building nuclear plants because the steam turbine and heat exchanger cost too much compared to natural gas plants.

If that's really the case then a Gen 4 reactor that runs at higher temperature, uses printed circuit or other advanced heat exchangers and a Brayton cycle gas turbine could win on the capital cost but it's easier said than done. There's not a lot of hope I think the LWR but the BWRX300 is at least trying to do it by deleting the heat exchanger and the only way you're going to get costs down radically will be by deleting things. Commercial Gen 4 reactors are at least 20 years out and we should have gotten started 20 years ago.

[philipkglass]

One radical answer that question which is often neglected for the facile "regulations" explanation is that we quit building coal burning power plants at the same time we quit building nuclear plants because the steam turbine and heat exchanger cost too much compared to natural gas plants.

The timing undermines this theory. The US added one nuclear reactor to the grid in 1996 then zero until 2016 (sort by first grid connection date here):

https://pris.iaea.org/PRIS/CountryStatistics/CountryDetails....

The US built an additional 58 coal generating units between 1995 and 2009 (see section "Age comparison of coal plants"):

https://www.gem.wiki/Existing_U.S._Coal_Plants

Combined cycle natural gas units were already cheaper to build in 1995, but the gradually rising natural gas prices over the next ~12 years meant that coal could still compete on cost for electricity generation. The cheap fuel for coal units counterbalanced the slower, more expensive construction process. It wasn't until fracked natural gas drove fuel prices down that coal unit construction ended in the US.

[jabl]

A lot of the natural gas plants are combined cycle, which includes a steam Rankine bottoming cycle.

[perihelions]

I don't see how this isn't dispositive on the economics question. That markets (overwhelmingly) choose to build combined-cycle natural gas plants, choose to add the Rankine bottoming cycle, means the marginal cost of the steam turbine is *less* than the marginal cost of the fuel saved by the efficiency gain. That's the case even in the USA; and natural gas elsewhere in the industrial world is integer-multiples more expensive.

The natural gas plants without steam turbines are precisely the load-following plants that run for a fraction of the time (or at a fraction of their capacity); the relative weight of capital vs. fuel costs is inverted. (Or those, like xAI in Memphis, which are rapidly assembled in rushed desperation. I wonder if that will be a trend in the datacenter boom: designs limited, not by costs under normal market conditions, but bottlenecks affecting rushed projects. Nuclear SMR's would seem to be worst at this—the designs they expect to use haven't even been built yet!)

[PaulHoule]

Yes, and the bottoming steam turbine is 1/3 the size of a steam turbine rated for the full power output so… radical capital cost reduction.

It isn’t just the turbine but the heat exchangers, in a PWR the ‘steam generators’ are water-water heat exchangers that are usually larger in volume than the reactor vessel. Many LMFBRs had two stages of heat exchangers (sodium-sodium and sodium-water) even larger heat on the water though SuperPhenix has relatively affordable secondary heat exchangers and never had them catch on fire.

[jabl]

> Yes, and the bottoming steam turbine is 1/3 the size of a steam turbine rated for the full power output so… radical capital cost reduction.

It's a cost reduction, but likely not radical when talking about a nuclear power plant. For a cost breakdown of a nuclear plant see

https://world-nuclear.org/information-library/economic-aspec...

So the "conventional island", which would include the steam turbines, condensers, generators etc. is about 15% of the cost. Reduce that to a 1/3 the size, and cost drops to 5% of the total, a savings of 10%. Probably even not that much, since a steam turbine 1/3 the size probably costs more than 1/3 the cost of a "1/1" size turbine. And then the remaining 2/3 of the power output would have to be generated some other way, so would shift cost somewhere else. Of course, some part of the cost of the nuclear island can be attributed to steam production as well. In any case, all in all I don't see this as making or breaking the economics of a nuclear plant. The issues that cause nuclear plant costs to skyrocket lie elsewhere (and no, just blaming regulations is overly simplifying it as well, though a popular scapegoat).

(I'm not sure, but I suspect what's making coal non-competitive with gas isn't so much the steam turbines, but rather that there's more labor and machinery involved in burning coal than gas, from mining, transportation, pulverizers, and then all kinds of exhaust gas treatment used at least in the civilized world, ash handling etc.)

> It isn’t just the turbine but the heat exchangers, in a PWR the ‘steam generators’ are water-water heat exchangers that are usually larger in volume than the reactor vessel.

Yes, that's true. The BWRX300, which of the current crop of SMR's is probably the one with the most realistic prospects of actually being built somewhere, is a BWR, and the maker claims one reason for the supposedly good economics is that they have spent a lot of effort on minimizing construction cost and equipment needed. We'll see, I guess. I think historically the economics of BWR's vs PWR's is mostly a wash.

> Many LMFBRs had two stages of heat exchangers (sodium-sodium and sodium-water) even larger heat on the water though SuperPhenix has relatively affordable secondary heat exchangers and never had them catch on fire.

The follow-up ASTRID project, which never left the drawing board, used a sodium-air (or might have been nitrogen, to avoid issues with trace contaminants in air since it was all closed cycle anyway?) heat exchanger and Brayton cycle turbomachinery, to avoid any potential issues with sodium and water. I think it was supposed to have slightly lower thermal efficiency than an equivalent steam plant, but maybe somewhat lower capital cost.

[credit_guy]

When a big tech wants to build some huge datacenters, where they plan to put hundreds of thousands of ultra-expensive GPUs, they want to run those GPUs as close to 100% of the time as possible. Every hour the GPUs don't run costs them money. From the point of view of Microsoft, having an SMR next to a datacenter makes perfect sense. Solar and wind can do the job, if coupled with batteries and/or natural gas. But than you need a grid operator. If all you need is electricity for a datacenter, and you don't care about being connected to the rest of the grid, then you want as simple a solution as possible. And an SMR promises to be just that, a turn-key solution to get continuous and constant electricity.

[bruce511]

I think "promises" is the key word there. Data centre's want power, as you say, but they want it now, not 15 years from now.

So yes, when SMR's are "off the shelf" (aka from "order" to producing) , including permitting, construction etc, within a couple years then they are appealing.

I don't think we're quite there yet.

[credit_guy]

Sure. But this is why what Microsoft did here was just a hedge. It did not cost them much (if anything at all) to become a member of the World Nuclear Association. If the SMRs become reality a few years down the road, and if the demand for datacenters increases significantly because of the increased use of LLMs, then they stand to benefit a lot. If either of this does not pan out, then what's the risk for Microsoft?

[johncolanduoni]

The point of the baseload argument isn’t the “desirability” of power sources that can provide baseload, it’s the necessity. Renewables that can be scaled up (i.e. not niche cases like geothermal) are all too inconsistent to replace the entirety of generation without storage. Other tactics like long range transmission can reduce the amount of storage needed but not eliminate it. Fully replacing generation with renewables isn’t just unprofitable without storage, it’s impossible.

Storage is making great strides but for it to get good enough to fully convert the grid we need qualitative advances in the underlying technology, not just manufacturing scale driving down prices.

[pfdietz]

There is necessity with baseload plants: they have to be run at high capacity factor or else their economics go all to hell. This is especially true of nuclear where capex dominates. So describing something as "baseload" is actually describing a defect: it's a generation technology that cannot be practically dispatched.

[johncolanduoni]

It’s only a defect if you try to make the grid 100% nuclear, just like solar’s variation is only a defect if you try to go 100% solar. It’s not a competition where either is likely to “win”, they’re just two different tools for power generation.

[bryanlarsen]

It wouldn't be a defect if it was complementary to solar. But it's the same defect as solar/wind, so it is a defect.

[johncolanduoni]

How is it the same defect? Nuclear plants can run all the time and have to if they have any hope of recouping investment. Solar can’t run all the time but is super cheap so it doesn’t have to. You still need responsive capacity but even if you keep natural gas around for that you’ve made a massive dent in fossil fuel usage - bigger than solar or nuclear could do without the other.

[bryanlarsen]

Both nuclear & solar produce power at times when it's not wanted. Same defect.

If you were building a grid from scratch in a typical American region, and you were aiming for lowest cost, you'd overbuild solar enough that it handles 100% of demand on a sunny evening, add enough wind to handle 100% of demand on a dark + windy evening, then add about 3 days of battery storage. That'll supply you over 95% of your energy needs.

But that's not 95% of the power, it's 100% of the power 95% of the time. So you also need to supply 100% of the power 5% of the time somehow else. That's not 100% of peak, since peak is during air conditioning demand when solar works, but 100% of almost peak.

The cheapest way to do that is low efficiency single cycle natgas. CCS natgas is 1/20th the cost of nuclear, and single cycle is about half the cost of CCS.

So if you make 2.5% of that nuclear, you've doubled the cost. And you've saved a few hours worth of carbon emission, 2.5% of 5%.

If you want to be carbon-neutral, you use syngas instead of natgas. Yes, syngas is 6X as expensive, but fuel is not the main cost of a peaker plant running <= 5% of the time.

[bruce511]

Of course electricity at night is highly desirable. But there are no economic incentives to build it.

From a purely financial point of view, base load is not appealing. Whereas cheap solar is appealing. If I have a billion$ to invest, I know which one I'm choosing. I'm maximizing return, not "societal good". Which is why govt is best placed to build base load, since they optimize for societal good, not profit.

To make base load appealing to investors we need expensive power at night. But that's countered by local battery storage.

To be clear, this is not a "what we need" argument. It's a capital argument. Private Power suppliers chase profit, and there's more profit in daytime power than nighttime power.

[johncolanduoni]

> Of course electricity at night is highly desirable. But there are no economic incentives to build it.

Wait, what? Who is going to accept having no power at night at their house? Ignoring the fact that the intra-utility trade does provide a direct economic incentive, nobody is going to live somewhere the power companies can’t keep the lights on 24 hours a day most days (in the developed world anyway).

[bruce511]

You're looking at this from the consumer point of view. But consumers provide income, not capital.

Consumers may, or may not, have a choice of power providers. They can choose to "accept" what is on offer, or remove themselves from the grid. But they have very little negotiating power.

Actually it's pretty easy for (residential and office consumers to spend their own capital on batteries and inverters. Most homes consume (or can be set to consume) reasonably low power at night. A 20 kw/h battery will cover most homes easily.

(Solar panels aren't necessary for this.)

The capital cost, and savings therefrom, put a hard limit on what suppliers can charge for night time power. And of course storage is just as attractive to suppliers. (More capital-attractive than say a nuclear plant.)

As consumers we are used to simply announcing our needs. And assuming companies will expend any capital necessary to meet those needs. In practice it doesn't work that way, as rural phone/internet/cable consumers will testify.

Once you see electricity generation as a capital issue, not a consumer issue, things get clearer.

[ZeroGravitas]

The point of separating electricity artificially into "baseload" and "peaking" was the quirk of engineering that made coal and nuclear cheaper if you ran them flat out.

In a world where both solar and wind are massively cheaper, that entire paradigm collapsed. Even more so when you can reuse the same hydro and gas that was working as peaking as "firming" to complement the new model.