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Comment by vlovich123 | Hacker News Reader

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-...

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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.

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