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Comment by Gravityloss | Hacker News Reader

Ordinary nuclear reactors have cooler temperatures than coal fire. So it's not straightforward to just replace that part and keep the rest like the steam turbine and generator.

One could have high temperature reactors like pebble bed, that would be a better fit but they are more exotic and experimental.

Didn't read the article because I won't subscribe to WSJ. They have been an anti climate science platform.

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> Didn't read the article because I won't subscribe to WSJ. They have been an anti climate science platform.

Sadly, the reporting side of the WSJ and "WSJ Opinion" are basically two entirely different universes lumped under the same brand / subscription umbrella. Clearly there's a significant share of subscribers who like the opinion pieces so the Journal has historically chosen not to do away with them, but I keep hoping they will kill or spin off that business. In fact, as a subscriber I was asked not too long ago to fill out a survey about WSJ Opinion and whether I think it adds or subtracts value from my subscription. I'm not sure these types of decisions are best informed by the results of online surveys but wanted to note that just FYI...

I signed up for the WSJ when they had a holiday special and I think I pay something like $5 / month for a year

The WSJ is owned by the Murdochs. If anything, you should hope they spin off the news business, and keep the opinion side. Sadly, I suspect they acquired the former to lend an air of legitimacy to the latter.

I don't believe that is the case. I have been reading the WSJ since the 1980's, before it was acquired by Murdoch, and the Op-Ed section back then was already way to the right of most mainstream media, and the WSJ news gathering organization. I don't think that Murdoch has improved the quality of the WSJ, but he has not changed Op-Ed editing.

On any opinion poll, I always write that I will pay for a subscription to the first major newspaper that gives me a 'no opinion/editorial' option.

I believe they were extra ordinary hard to cancel, like the NYTimes, for and the best tip if you ever consider cancelling was to just cease payments through PayPal or your creditcard. This saves you the lovely trip to a sales rep and whatnot.

Are you sure about that? From what I could find reactors are in the 500-1000°C [1][2] while coal turbines are in the 540-600°C range [3]. This is about the small modular reactors which I think are HTGR and run a bit hotter AFAICT (i.e. closer to 1000°C). Seems pretty close regardless.

Do you have anything I can read up about regarding nuclear reactors having cooler temperatures than what coal fire generates?

[1] https://www.iaea.org/sites/default/files/publications/magazi...

[2] https://www.sciencedirect.com/science/article/pii/S173857331...

[3] https://www.sciencedirect.com/topics/engineering/coal-fired-...

Yes they're right about it. Your first link says that water-cooled reactors can produce steam up to about 300 °C, which is accurate.

The hottest outlet temperature today from a nuclear reactor is about 1000 °C from HTTR in Japan, but that's fairly exotic.

There have been hotter outlets back in the NERVA nuclear rocket days. Also exotic.

Good read is this one: https://www.iaea.org/publications/8692/advances-in-nuclear-p...

- "There have been hotter outlets back in the NERVA nuclear rocket days. Also exotic."

Though, those were rocket engines with a design lifespan of several minutes. It's not possible to sustain temperatures like that, is it? (I am not an engineer).

I remember reading that one of the NTR test firings saw bits of molten corium flying out in the exhaust plume.

Jet engines get way hotter for sustained periods of time: https://aviation.stackexchange.com/questions/74362/how-hot-d...

(And the crazy thing is, if you think about it, they are also gas turbines! The bough I guess perhaps your question was more specific to the reactor itself)

Am I misreading your link? I see temperatures listed "only" up to 2,000 K; but the successful NTR tests went up over 2,500 K. (Excluding the failed ones that melted, of course).

- "The average exit gas temperature was 2,550 K (2,280 °C), the highest ever recorded by Project Rover. The chamber temperature was 2,750 K (2,480 °C), another record."

https://en.wikipedia.org/wiki/Project_Rover

There's also one notable difference: internal combustion turbines see their highest temperatures in the gas phase, which is somewhat insulated from the turbine blades (by weird fluid dynamic effects I don't understand). No solid material needs to withstand the peak temperature.

https://en.wikipedia.org/wiki/Turbine_blade#Film_cooling

I was focusing on turbine elements with temperatures well in excess of 1000 deg C, which is much higher than the temperatures described above.

Indeed, exhaust gases are even hotter.

I believe turbine elements are cooled by grouch internal channels these days, which is quite mind blowing.

300° C. Nuclear reactors are pretty cold, for thermal generation. As I understand it, this is because the cooling system has to remain liquid, and you can only pressurize+heat water so much before it turns to steam (or becomes prohibitively expensive to contain).

Yup. Most of the UK's reactors are an unusual gas-cooled design which does produce steam temperatures similar to coal power plants, but that's pretty much unique to the UK and also a technological dead end - there were apparently enough engineering headaches that they didn't end up a clear win over standard pressurised water reactors and no-one's built any based on that design since.

Working fluid temperature is much lower than the coal fire, and it's limited by the material science considerations of the piping and turbine, not by the reaction temperature. You are not going to see systems employing steam hotter than 550 degrees C.

The only integration points of the old coal plants are the transmission lines, location footprint, access to power generation employees. Steam and temperature aren't in play.

It seems to be much more common to re-use old coal plant locations as grid-scale energy storage sites.

That's a more realistic approach.

That would mean investing in new coal plant steam turbines now would be a dead end.

They are very expensive things.

Would you not reuse the generator itself? What about the turbine that drives it?

You would. You might need to screw around with a few of the compressor stages to get peak efficiency on the cooler steam source but that's by no means rocket science.

You can still read WSJ articles by posting the link into archive.ph.

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