Here in Switzerland during some heatwaves they have to shut down nuclear plants too because the river water is too warm and adding warm water to it would kill the fish.

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petre 9 hours ago | parent | next [-]

Would a cooling pond with controlled discharge into the river maybe mitigate this problem? One could also cycle the water from the cooling pond through the plant's cooling loop. The worse that could happen is evaporate the water from the cooling pond which is gets replaced with new water (sans fish) from the river.

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topspin an hour ago | parent | next [-]

> Would a cooling pond with controlled discharge...

There are any number of methods of dealing with this. Using natural bodies of water is a lower cost (thus highly popular) method of sinking heat. Palo Verde has been operating 3 large reactors in the Sonoran Desert in Arizona since the 1970s. There is no reason in engineering or physics that a power reactor must be highly sensitive to any particular lake, river or ocean's temperature. This is strictly about money, being cheaper to rely on a big "free" heatsink, and leaving too little margin for changing conditions.

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wcoenen an hour ago | parent | prev | next [-]

Nuclear plants can run with those hyperboloid cooling towers as the sink for waste heat. They are just a lot more expensive to build, run and maintain compared to using river water.

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Choco31415 3 hours ago | parent | prev | next [-]

There's plenty of work happening with adapting non evaporative cooling loops for data centers. Maybe that can be applied here too, even if to mitigate some of the cooling needed?

	▲	2 hours ago \| parent [-]
		[deleted]

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downrightmike an hour ago | parent | prev [-]

making modern websites not 100's of megabytes heavy would go a long way

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number6 10 hours ago | parent | prev [-]

And it's not cold enough to cool the reactor

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masklinn 10 hours ago | parent | next [-]

The reactor absolutely is not going to care, it’s the tertiary cooling circuit cooling for the steam turbines, it will have cooked off everything downstream long before it’s an issue.

This is entirely an ecological and safety concern.

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seszett 10 hours ago | parent | prev | next [-]

No that's never the problem, even 40°C intake is cool enough to cool a reactor, it's all just a question of returned water temperature that can be harmful to a river if too high (generally the limit in Europe is set to 30°C).

	▲	masklinn 7 hours ago \| parent [-]
		It can vary by the river too (e.g. I remember Switzerland pulling back a reactor around 25 intake), and iirc there’s an absolute limit on the outflow (you don’t want to boil alive the stuff just off of the plant) and a relative one a bit downstream (you can’t heat the river to 20 when it’s freezing). These heatwaves reduce the margin from both directions, a hotter intake means you have less margin on the outflow, and the lower flow rate means there’s less water to dilute that outflow. And apparently for that specific plant there’s also the water level not even reaching the intake.

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dredmorbius 4 hours ago | parent | prev | next [-]

The principle cooling mechanism is vapourisation.

The heat of vapourisation for water, converting liquid to steam, is 40.66 kJ/mol, or 2257 J/g. It takes a lot of energy to boil off water.[1]

That compares with the latent heat of liquid water, the energy required to heat one unit of water by one degree, which is 4.2 J/g*K (where K is the delta temperature in Kelvin).

Raising the temperature of input by, say, 10 degrees, would only reduce the cooling factor by less than 2%.

________________________________

Notes:

1. Which is why live steam is so dangerous. Steam condensing will release a huge amount of thermal energy, making steam burns especially harmful.

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shakow 9 hours ago | parent | prev | next [-]

Absolutely wrong. A difference of a couple degrees is not going to hamper cooling a reactor that is running at many hundred degrees.

Just imagine what it would spell for your car otherwise.

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ZeroGravitas 8 hours ago | parent [-]

I think both nuclear steam and car engines are affected by high ambient temp, gas and coal engines too.

That is after all why they bring in water or air to car radiators, to cool them.

Probably only a single percent or so for a few degrees change though.

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shakow 8 minutes ago | parent | next [-]

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.

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voakbasda 6 hours ago | parent | prev [-]

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

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HPsquared 2 hours ago | parent | next [-]

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.

	▲	namibj 10 minutes ago \| parent [-]
		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.

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masklinn 5 hours ago | parent | prev [-]

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)

	▲	philipkglass 2 hours ago \| parent [-]
		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.

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VLM 2 hours ago | parent | prev [-]

OP is correct, the people making fun of OP don't have an engineering background.

The pressure of a condenser at 90F (hot summer day) is about 1/20th of an atmosphere and ... pretty obviously the pressure of a condenser at 212F is about one atmosphere. You can't just arbitrarily decide to change the low pressure side of a turbine like that, its not going to turn out well. You could, in theory, design an entire thermal plant coolant loop to deal with the condenser running at 1 atm instead of 1/20th atm but most will not.

There are also heat flow rate issues where the higher the delta V the higher the watts. Regardless of condenser pressure issue above, if a heat exchanger can pull 1 MW across a 150 degree delta-V then if you run the cold side much warmer at only 15 degrees delta V it can only "pull" 0.1 MW of heat. Its surface area doesn't magically get bigger LOL. Remember that for every watt of electricity you get to dump around three watts of thermal heat. If you lose 9 MW of cooling power you lose 3 MW of output electrical power. You have to move more heat than non-engineers expect, to generate electricity.

Its a simplification, but for various reasons they like to design the hot side as hot as possible, so if you lose 100F of cooling you can't keep the same power output and simply run the hot side 100F hotter than normal and keep the same flow rate. Absolutely nothing good will come from overheating it like that.

You could engineer a thermal plant (thermal as in coal, nuclear, burning recyclables and biowaste, anything to make steam) that runs at an ideal hot side of 212F and let the hot side literally boil water in a pool. However, they don't make plants like that IRL and trying to force it under those conditions would turn out very bad... The first thing that comes to mind is gunk buildup and higher corrosion rates. Steel (generically speaking) corrodes in water about twice as fast per every 20C increase, so turning a cold water plant into a water boiler would to first approximation cause about a year's worth extra corrosion per month. Could be designed around, but I would not want to cowboy a nuke and just try it. Some of those parts are very expensive; even if you can safely run the plant and replace the corroded parts at a substantially accelerated rate, the cost of power due to corroding the cold side parts might make the power too expensive even if its "safe enough", making it cheaper to just shut down. Moving large amounts of water (or air) is extremely expensive, both capex and opex, so an additional 10x higher once in awhile here and there could be a lot of money...