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Comment by Dig1t | Hacker News Reader

Nuclear absolutely has to be part of that carbon neutral equation. Solar and wind are awesome, but they are not “dispatchable”. i.e. they turn off sometimes when the wind stops blowing or the sun isn’t shining. Without tons of batteries, natural gas and coal etc are always going to be used to fill the gaps. Nuclear is the perfect choice to replace those dispatchable sources.

Also, additional nuclear capacity can be used to do things like desalinate ocean water and help alleviate droughts in the future.

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Traditionally, nuclear is not dispatchable either, it's baseload, and in particular these SMRs are not dispatchable. There are a few variable output reactors in France, but they are very expensive. Molten salt reactors could perhaps have a thermal storage component, but...

Nuclear is "firm" in that its always running. This is a good characteristic. I'm more optimistic about advanced geothermal that has been developed in recent years, using the advances in drilling developed for fracking.

If we can use the waste heat from nuclear for something productive, like desalination, then I think it has a much better chance. But coastal communities will also have access to offshore wind, which has really high capacity factors and will be far far cheaper than nuclear could be.

The design we are talking about here has the capability to load follow:

  The unique features of a NuScale plant allow its modules to respond to meet the power generation demand in the evenings by increasing from 20% to 100% power in 96 minutes

[1] https://www.nuscalepower.com/newsletter/nucleus-winter-2019/...

Nuclear reactors aren't fundamentally incompatible with load following: you can stick some control rods in or out and get more or less heat energy distributed to your turbines.

Nuclear power plants are generally used for base load for economic reasons: they are really expensive to build and have close to fixed hourly costs to operate, compared to say natural gas plants which are cheap to build and have operating costs proportional to the amount of gas they burn. Consequently we only build nuclear where we expect it can be utilized pretty much all the time, and we don't optimize nuclear plants for quick scaling up and down.

Thank you! I'm surprised that I've not heard this before, and I never noticed it the many times I've been to NuScale's site.

I'm clearly in left field when it comes to concerns about nuclear, in that I mostly am worried about wasted effort and capital on a tech that I do not foresee being able to keep up, rather than concerns about "safety" or belief that it is in anyway necessary for decarbonization. So I appreciate seeing some new information that make me more hopeful that SMRs will succeed.

> Molten salt reactors could perhaps have a thermal storage component

If you can build one of those economically and deal with the caustic molten salt then you can build a concentrated solar thermal plant with molten salt for storage even more economically with no worries about a nuclear disaster.

While nuclear disasters are acutely catastrophic, they are also exceptionally rare. In the US, nuclear power has 1/100th the deaths per TWh compared to hydro electric, 1/500th oil, and 1/1000th coal.

I really hope the US can adopt a more aggressive approach to using more fuel, even if that means it may be closer to weapons grade at some point in its cycle. This would eliminate a significant amount of waste leaving catastrophic failure as the only real downside.

I would be very happy with a nuclear+solar future (which is currently my present as well).

The last nuclear meltdown was literally a trillion dollar disaster.

Wind and Solar don't have failure modes like that so you don't even have to think about it.

This is why Nuclear tends to get more expensive over time because nobody can accurately calculate the risk of any design decision, so engineers and managers tend to make them more complex over time.

> Traditionally, nuclear is not dispatchable either, it's baseload, and in particular these SMRs are not dispatchable.

Thermally, generally not. But one can design a system so that the steam is not sent to the turbines and so electrical power is not generated.

An array of SMRs is dispatchable even though a single SMR is not. It’s a scheduling problem.

Oh really, what's the ramp rate of this design? I haven't heard anybody claim that ability for SMRs.

What makes an array more dispatchable than a single SMR? I don't follow how that could be possible.

Elsewhere in the thread, credit_guy quotes 20% to 100% in 96 minutes[1].

[1]https://news.ycombinator.com/item?id=32370392

Not sure 96 minutes will be sufficient in all load-following cases (bar a huge and therefore very expensive fleet of reactors). A gas turbine is way ahead here. Moreover in existing reactors the frequency of such adjustments is limited, for example "no more than twice a day, with a minimal 5-hours pause between modulations, and no more than 150 modulations per year". Approaching limits adds maintenance time (at shutdown state). I don't know if SMRs alleviate this, but given the causes I doubt so.

We will likely have sufficient battery storage where 1.5h would be acceptable though not quite ideal. It still requires quite a bit of storage, but its entirely doable for seasonal variations (the harder problem) and perhaps even daily cycles (the lesser problem).

You make it sound like nuclear is the only solution to this problem. It's not. It's merely a very expensive solution to this problem. There are all sorts of storage options being considered currently that each have their own cost profiles. Some of them are very cheap and simple too. And when solar is basically orders of magnitude cheaper in terms of GW/$, you can afford to have quite a lot more of it than you need to compensate for cheap but relatively inefficient storage options and still be cheaper overall.

As I said in my original post, cost is the key driver here and nuclear has a lot to prove.

You say "always", but the technological progress and price curves indicate that within the next 20 years wind and solar (with batteries) are going to outperform any other source of energy generation by such a large factor and become so cost efficient that it would be ridiculous not to use them exclusively.

> they turn off sometimes when the wind stops blowing or the sun isn’t shining.

Spreading production at continental scale has a major beneficial impact, and such a huge grid is highly beneficial to any type of source (even nuclear).

https://www.imperial.ac.uk/news/180592/european-cooperation-...

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