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Convection cooling efficiency is mostly dictated by the delta in temperature between the hot and cold source. Coolant temperature in the core is in the 300C ballpark. So the river going from 20 to 30C is roughly a 0.3% change in cooling efficiency.

For your car, coolant temperature is typically in the 80-90C range. So the same change in external temperature would be a loss of ~10% of cooling efficiency. Still, cars have no issue running in 30C temps, and IME you have to go up to 45 to really need specialized cars.

So if you car can swallow 40C and >10% efficiency loss without a sweat, a NPP will have 0 issue using 30C water to cool their cores.

by voakbasda7 hours ago|

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Begs the question: coul reactors use radiative air cooling? Channel the water through a huge radiator and transfer the heat to the air

by HPsquared3 hours ago|

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The temperatures aren't high enough to do that (or air cooling) efficiently enough. Some experimental designs for high temperature operation would have that as a possibility (e.g. molten salt reactor designs). I think a Chinese research project is looking into air cooling for nuclear power in dry regions.

by namibj1 hours ago|

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There's also the potential of co-locating non-evaporative cooling with CO2-scrubbing using a strong KOH solution in the big cooling towers and regenerating the hydroxide with calcium hydroxide (regular process done in kraft process paper mills, though they use NaOH with slightly favoured properties over KOH). KOH is very hygroscopic; it does not have to be humid for a barely-still-liquid solution to actually dehumidify in the process.

Or, if that's too much effort for them, use e.g. LiBr or other such atmospherically-stable salt that can maintain humdity equilibrium with dry ambient air.

The reason for even involving a water-based solution at all is because you can spray it or at least run it over dense corrugation (sheets alternating orientation, but overall with the channels roughly pointed upwards) "packed beds" with free contact between the coolant and the air, instead of having to maintain a barrier layer between the two (typical car/computer radiators, but also AC coils), which notably saves you from even a potential for a there-required barrier layer to leak and from having to clean such a barrier layer. If you make the corrugations large enough and have some simple mesh filters in the intake path that you just roughly shake/rinse/blow/brush off every once in a while, you can prevent particles larger than a rice grain from getting to the coolant in the first place and wash/rinse all the sand grain and smaller dust particles down into the coolant sump where their densities are far better matched (than air vs. dust) and volume flow is much easier to handle/filter.

The big part of these is still that they don't require active fan ventilation to cool radiators, which would be a substantial increase in critical electrical power needed after a SCRAM to keep the core from melting down; vs. the passive evaporative cooling towers and the KOH/LiBr non-humidifying variant I mentioned.

by masklinn6 hours ago|

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Not really, a large reactor is way too power dense. An EPR reactor has a thermal output of 4.6GW. And the tertiary is cooling steam turbines so it's below boiling, you'd need something like 10 sqkm worth of surface, per reactor, with an environment cool enough that this could actually radiate.

Even using industrial air-cooling design you'd need on the order of a million sqm or two (for reference a good quality computer heatsink is about a third of a square meter worth of fins)

by philipkglass4 hours ago|

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The German THTR-300 reactor operated with air cooling:

https://en.wikipedia.org/wiki/THTR-300

But it was admittedly a huge cooling system for a reactor that only produced 750 megawatts of thermal energy.