Hot weather cuts French, German nuclear power output | Hacker News Reader

Hot weather cuts French, German nuclear power output

reuters.com

46 pointstosh72 comments

I think this is a non-problem. At least for France and Germany, peak electricity consumption is in winter, because electric heating is much more common (and needed!) than air conditioning. This seasonal surplus is such that nuclear power plants actually have to reduce their power output in summer. Here is a chart showing a ±30% seasonal variation in nuclear electricity production: https://jancovici.com/wp-content/uploads/2017/10/elec-mensue...

Even if it's a non-problem now it will be a growing one in future and there are a few problems here. Nuclear power makes up 70% of France's electricity, so even if they normally turn off/down some reactors it will become a huge problem if they have to turn many of them off. It's also much easier to plan for a seasonal variance then a weather one, they get much less notification of when rivers will be too hot and when they will cool down again is unpredictable. Finally it undermines the economics of nuclear power, they already take decades to recoup the build cost, if they even can against renewables in future, being able to run even less pushes that further out.

Most importantly it's a warning to other countries considering nuclear, especially equatorial ones where nuclear power is almost non-existent.

Isn't this just a design problem? Surely the temperature we're trying to reduce is much, much higher than "summer river" temps. Seems like a higher flow rate and/or a better heat exchanger would fix this.

How would a more efficient heat exchanger reduce the resulting temperatures of the river water used to dumps the heat? A river full of dead fish is even worse PR than long term radiation danger.

This is specifically a problem with building a nuclear power plant on too small a body of water. The ocean doesn’t have this problem. Neither would the Great Lakes.

Actually it's a problem that arises when you build a nuclear plant next to an intermediate body of water. When the river is too small (or irregular, like the Loire) you build cooling towers on your plant, and you are fine (or at least, you need much more extreme weather conditions to have issues). The problem with plants built on the Rhône is that there is usually enough water in the river for direct cooling, so the designers didn't bother with a cooling tower[1]. But when the water flow is low, you need to stop the plant.

[1]not all of them though, in some cases the Rhône's flow wasn't enough for direct cooling and they went with cooling towers: The Cruas-Meysse plant has cooling towers and it's not affected by the current heatwave. Also, the Bugey and Tricastin plants have a mix of both (2 reactors with direct cooling and two with cooling towers) and only the reactors with direct cooling are affected.

I thought the cooling towers at Tricastin were only for the fuel enrichment part

The problem is regulations. If the river is already hotter than the max temperature allowed as output, then it’s not possible to operate, for regulatory reasons. Temperature delta is on the order of 0.1°C

Interesting how they didn't sell that surplus to South countries as Italy or Spain, where major consumption peaks in Summer due to air cooling systems

They most definitely try. But don't forget that you also have to transfer the electricity from the producer to the consumer. The transmission lines across Europe may not be able to carry that much energy across these distances.

In winter some nuclear power plants also have to be shut down because their cooling rivers are frozen.

Idk about Germany, but this cannot happen in France, the climat is way too warm for that.

Edit: having looked a bit more in details, it looks like even though the rivers can't be frozen to a point it stops the plant from functioning, the water admission systems can (partially) freeze in extreme weather and it happened a few time in France already.

It'd be technically interesting to see how expensive it is to mine the ice and shovel it into directly into the cooling system somehow. It isn't like there is a problem finding heat to melt the ice once it is on site, absorbing waste heat is the whole point.

Freezing rivers are less of a pfroblem in Germany and France, but the rivers can be low on water so that the cooling might be limited in the winter. And there have been winters, where the nuclear production in France was struggling keep up with the heating requirements.

In Finland the nuclear plants are by the sea, I'd imagine this to be at least part of the reason.

Finnish plants have to reduce capacity during hot summers too, but it's because of their environmental requirements: the exhaust water back to the sea must not exceed a given threshold to protect marine life.

It's also because of environmental requirements in France, and I expect in Germany as well.

Nuclear plants could use warmer water, but regulation forbids them from releasing water at a higher temperature than 30°C.

It is a problem, if not a very big one right now. With the climate changing, expect Europe to build out more air conditioning to cope with hotter summers, raising power usage. Dismissing this very real operational problem for the power plants is unwise.

Air conditioning is consuming much less electricity than heating, there's no scenario where it would become greater than the winter usage. And there's only a few reactors affected by this issue, you have this kind of clickbait article every year.

> Air conditioning is consuming much less electricity than heating, there's no scenario where it would become greater than the winter usage.

How about "most people aren't using electricity for heating"? People rarely heat their houses with electricity in Europe, that would be very expensive. It's usually gas or oil boiler, sometimes a coal one.

You have about 50% share of electricity heating in France, it's far from nothing.

Edit: And coal heating is probably close to zero to be honest, that sounds old, even for the countryside. The rest of those 50% would be gas, petrol and wood.

I am so jealous. Here in Kazakhstan we use coal-powered central heating. And here is the kind of air it gives us:

https://b.radikal.ru/b12/1902/bd/a6d615dba25b.jpg

https://d.radikal.ru/d15/1901/1b/ea0e8c26f8d2.jpg

It gets much worse in the evening.

These photos were taken in Almaty, but the situation is the same everywhere (if not worse).

At first I wanted to post this particular photo, but couldn't find it, and now I can't edit the original comment.

https://d.radikal.ru/d17/1812/fd/ed5cc5dcd4c4.jpg

Those pictures look awful, I hope it will improve in the future :/

This is very location dependent. Some nations are almost entirely warming their homes with electricity.

Doesn't have to be greater than winter usage to be problematic. All it takes is several unfortunate events occurring at the same time—the kind of curve ball father time likes to throw occasionally. Say, extra hot weather, little wind which leaves wind power lacking, a few gas power plants out for technical reasons or supply shortage and then throw in baseload nuclear power plants short on water.. Unlikely? Yes, but unlikely events occur all the time. And for something essential as electricity..such a risk should be taken seriously, not dismissed out of hand as a "non-problem"

Well, right now there is extra hot weather, little wind, little installed solar power in France (and reduced solar power output because of the heat) and no problem at all either. There is a lot of spare gas capacity, the gas plants are mostly unused right now, and the nuclear plants are more than able to cope with the power demand, as less than 60% of installed capacity is needed now.

There is really no reason to think there is, or could be any problem in summer in the foreseeable future, since we are already in a worst case situation (highest temperatures ever recorded, basically no renewables used, nuclear as almost the only source of electricity at the moment) that is not problematic.

Agree on most things except on the worst case scenario being constant with time. We should expect things to get worse and plan accordingly.

Most offices are already airconned in Europe. There might still be a bit of market expansion in private homes, but probably not that much - due to cost and urban landscape (old houses that are hard to retrofit for aircon). The landscape is also variegated enough that one can get relief from oppressive heating with little effort (going to seashore/lakeshore/hills).

The problem is two-fold: maintenance scheduled in the summer when the demand is “usually” lower. And stations operating with a river for cooling, where they have severe restrictions on many parameters, including maximum output temperature, which the river itself now goes over during a heatwave, so they need to shut down. It is a paradoxical situation in which the combination of our use of fossil fuels worldwide and inadequate legislation bars us from using a decarbonized energy source.

Also note that PV efficiency goes down with heat, so I fully agree with you that excessive AC reliance is a very real concern. Insulating buildings should be a big priority.

This should also be affecting coal plants, since they also need to exhaust heat via an identical mechanism. Yet the article only mentions nuclear.

That's because you need literally days to get a nuclear plant running again. Coal plants can start within hours.

But do you have numbers on how it's affecting coal plants? Maybe coal plants don't need so much cooling?

Coal plant in hot weather affect the efficiency of cooling water thus the NPHR. Also if you cold start the coal plant, it takes a day sometimes

They don’t necessarily shut the nuclear plants down, they throttle the power output. It isn’t a strict on/off switch, but a controlled reaction. They said two were offline but it wasn’t said why they were offline. (Likely usual maintenance and refueling). You wouldn’t specifically shut down for this reason.

At least in France, a lot of nuclear is operated in load following mode, meaning they can operate at less than 100% power and do semi quick changes.

> That's because you need literally days to get a nuclear plant running again. Coal plants can start within hours.

You don't shut down your nuclear plants, you moderate them up and down.

Unlike e.g. Germany, France's nukes were designed (and are used) for very aggressive load following, reactors can output 30~100% of their rated power and can rate up and down at up to 5%/minute.

Here's a twitter thread on the subject (in french) from early march: https://twitter.com/TristanKamin/status/1102620969808658432

This is a bloke who apparently likes following france's electrical and nuclear networks, roughly speaking on March 4 checking the previous week's data they saw that only 40 out of 50 reactors had been running (= more than 50% of rated power) on sunday, looking at electical demand it had fallen 15GW from early feb to early march (march was quite warm), nukes had dropped 10GW between saturday and sunday: not only was demand low (usually the case on french sundays) wind power had gone crazy. Gas plants were completely shut down (except those used for both electricity and heating), hydro was at the lowest possible level, pumped hydro had pumped all it could.

Checking neighbours, Germany and Austria had spent part of the weekend with sub-zero electricity prices (they were paying surrounding countries to take electricity off of their hands).

From sunday to monday, demand picks up like mad, and the nuke network handled overall increases of 50~100MW/mn over the morning (it still had to be supplemented by hydro and gas as consumption rate of changes exceeded 150MW/mn).

This is the graph of nuclear production changes over the week-end: https://twitter.com/TristanKamin/status/1102625880520699911/... the sunday lows went down below 38GW, the highs on either side are above 50.

The nuclear plant itself can run just fine, but the river water temperature would go up too high, damaging life in it.

Coal plants are air cooled, not water cooled (i.e. they have exhaust), and are not affected.

Is this specific to german’s coal plant ? Since in asia, coal plant are water cooled

All plants are water cooled, the question is if they use a cooling tower, or if they use river water.

Here's the first coal power plant I found on Wikipedia:

https://en.wikipedia.org/wiki/Fossil_fuel_power_station#/med...

Exact same evaporative cooling towers as used in nuclear power plants, which is what you'd expect seeing as they use the same steam turbines to drive their generators.

And a diagram of a generic coal power plant:

https://en.wikipedia.org/wiki/File:Coal_fired_power_plant_di...

Again, water cooled.

Nope. The towers are to reduce water usage and lower the temperature of the water before it is returned to the environment.

https://allthingsnuclear.org/dlochbaum/shh-secrets-of-the-co...

They cool the water, not the plant.

Ars claimed that coal power stations are air cooled, your parent is refuting that by pointing out the cooling towers.

Cooling towers cool water because it was heated up in some way, possibly by cooling the power plant.

He's right, they use the tower to pre-cool the water before using river water to cool it even more.

Coal plants typically only have the tower, and don't use river water.

FWIW plants with cooler towers are not really affected by the heat wave, as an other comment notes the issue is for plants next to intermediate bodies of water (in France that's mostly plants on the Rhone which is a pretty large river): since they were next to a pretty big body of water they were designed without cooling towers, but the combination of warming & body of water not being quite big enough it's possible for the water flow & temperatures to adversely effect cooling and thus require throttling.

From the article you linked: "Waste heat from the condenser is transferred either to the air, or sometimes to a cooling pond, lake or river."

Coal plants can certainly use ponds to cool, but air cooling works just fine for them. Unlike Nuclear Coal can eject most of its heat, as exhaust from burning the coal, into the air.

I have to add, it was a little dishonest of you to link to the one photo with cooling towers, and not to all the other ones that don't have them.

>it was a little dishonest of you to link to the one photo with cooling towers

It's the first picture on the page "Fossil fuel power station", which is the redirect for "coal power plant".

The second photograph is Currant Creek Power Plant, which is a relatively modern (2005) gas-fired plant, which does indeed use air cooling.

The third photograph is the decommissioned coal-fired Carbon Power Plant. Although not clear from the photo, this uses water cooling. The cooling towers are visible here:

https://www.deseretnews.com/article/705396191/New-mercury-st...

The fourth photograph is the decommissioned coal-fired Mohave Power Station. This also uses water cooling, although its cooling towers are shorter and wider than the classic hyperboloid design.

Fifth is the active Taichung Power Plant, coal-fired, also water cooled according to its Wikipedia page.

100% of the photographs of coal power plants on the page reached by searching Wikipedia for "coal power plant" show water-cooled plants. How is my example dishonest?

I see the problem. We are confusing cooling towers with river water cooling, also called "once-through cooling".

Cooling towers are specifically when you don't use river water for cooling.

Your first photo has a large lake in front of it, so clearly they will use that, but the rest don't, they only have the towers.

Nuclear plants almost always use once-through cooling or cooling ponds, but coal plants typically don't, and are unaffected by the heat limits (which are environmental for fish, not technical for power generation).

Edit: Notice how in the diagram you linked there is a river for cooling, but there is no tower? Coal plants will have one or the other, but nuclear uses both, and that's because most of the waste heat from coal goes up the chimney.

I am not confusing anything. In https://news.ycombinator.com/item?id=20532446 you said "Coal plants are air cooled, not water cooled". I simply posted a counterexample. The coal plant is water cooled, and all the other coal plants pictured in the Wikipedia article are also water cooled. You still haven't justified your accusation of this being "dishonest".

>but nuclear uses both

People have already posted multiple examples of nuclear plants that use only one, e.g. https://news.ycombinator.com/item?id=20532670

I don't know how they cope in Germany but there's only 4 coal plants left in France anyway and only one not built near the sea as far as I know. https://fr.wikipedia.org/wiki/Centrale_%C3%89mile-Huchet, this is the only one which would be affected maybe.

How big of a problem is this if nuclear is going to be an option as global temperatures rise?

Will nuclear be shut down so often in the future that we can't depend on it? Similar to the argument folks make against solar(it doesn't work at night).

Power plants are designed are designed to take useful energy by transmitting heat between something hot and something cold. They can be designed to work for any condition of "cold" and a few degrees doesn't change the ability to design.

Problem was these plants were designed for an amount and kind of heat sink which wasn't there for a while. If it became a frequent problem it would be fixed by building alternative heat sinks that worked in more situations.

Water cooled reactors run at about 300C, molten salt around 700C or "much higher", and some designs for gas cooled reactors go over 1000C. The weather being a few degrees hotter or even tens of degrees hotter isn't really going to matter if your cooling system is designed to handle it.

The minimum temperature gap up there is > 250 degrees, taking a few away isn't going to make anything impossible, but it might make some existing plants increasingly unreliable if there are no investments in new plants or upgrades.

this is not an engineering problem, it is a "how much are we willing to affect wild life" problem.

No it's an engineering problem, these plants were designed without cooling towers because it was assumed the direct cooling using river water would be sufficient in all but the rarest cases.

Presumably it's more of a financial/efficiency problem. Pumping water is expensive, less reliable and a heap of maintenance nightmare compared to passive options. You'd avoid it entirely if it was feasible.

> Presumably it's more of a financial/efficiency problem.

It's absolutely a financial decision, but it wasn't a financial problem. Cooling towers are not free but in the grand scheme of building a nuclear plant they're not expensive either (most power stations — including non-nuclear — have cooling towers).

And "Direct cooling" is not a passive option, you're still pumping water from and to the river or body of water in order to condense steam in the secondary circuit. What you're not doing is semi-closed cycling of that water through a cooling tower, you're feeding the condenser straight from the body of water, and sending water back into it more or less directly (possibly having gone through a radiator of some sort to shed some heat).

Don’t forget the PR aspect, and political cost. A lot of people in France believe nuclear power is carbon intensive because of the plume coming out of the towers.

You can always just evaporate the water, reducing the amount of water to around 0.5 m^3/s per GWe.

That's what's normally done when the body of water is too small, you add a cooling tower, cycle the tertiary coolant through it and compensate for evaporation from the water source.

The issue here is that the body of water is "intermediate", so it was large enough the designer felt they didn't need cooling tower as inflow would be sufficient in all but extreme case, except the extreme case is becoming the normal.

It's a problem only for nuclear reactors that use waters from rivers. Nuclear plants near seas don't have this problem.

They’ll have a see rise and tsunami problem

I think we're okay with the tsunami risks in France. And sea rise even in the worst scenario isn't much of a threat either.

here is the deal: the only recorded tsunamis in France are in the English Channel, where the only French coastal power plants are.

This story omits the most important information. What happens to plant and animal life if we raise the river temperature? And what happens if we instead burn more coal in Germany to compensate?

> What happens to plant and animal life if we raise the river temperature?

The entire ecosystem changes, possibly hosting invasives / foreign species and killing the native ones (or becoming inhabitable).

That is why — in france at least but probably not solely — there are pretty strict limits on the allowable difference between input and output water temperatures.

The plants and the fish can die. On the short term, the oxygene content of the water is the problem. The oxygen content decreases with increasing water temperature. So beyond a certain temperature, the oxygene levels can go below the levels required for survival, the animals and plants suffocate. Especially in lakes it can happen, that in these weather conditions basically all fishes can die at the same time. Agitating the water helps to maintain higher oxygene levels.

"Available nuclear power supply was down 1.4%" and for environmental reasons, not engineering oens. So much drama for nothing. If you advocate for renewable in reaction to this article, tell me how much a solar panel drops everyday at night, or a wind turbine when there is no wind.

> Available nuclear power supply was down 1.4 percentage points at 65.3% of total capacity compared with Wednesday.

You left out an important part to the point of being intentionally deceptive, the opening paragraph says it's down 8% overall. If aircon were common that could mean large scale brown outs. As this becomes more common they'll probably need more solar to help with the unreliability of nuclear.

> tell me how much a solar panel drops everyday at night

Nighttime is the easiest problem to solve with solar, it correlates with lower energy use and is an extremely predictable occurrence making it much easier to plan for than weather events.

> or a wind turbine when there is no wind.

Depends on the location and what it's paired with, but wind is almost always available in some capacity.

Let's not pretend nuclear is perfect, even without events like this plants go offline for things like maintenance (TFA mentions 2 that are currently offline), renewables aren't unique in their need to build excess capacity to deal with intermittent availability.

tl;dr:

> High water temperatures and sluggish flows limit the ability to use river water to cool reactors.

> EDF’s use of water from rivers as a coolant is regulated by law to protect plant and animal life and it is obliged to cut output in hot weather when water temperatures rise, or when river levels and flow rates are low.

When I started reading this, particularly the first line quoted above, I was ready to call BS on it, and almost stopped reading. The idea that that the river being a bit warmer would make it ineffective at cooling the reactor was too silly. But then I got to the second quote and realized they just don't want the reactor to make the river any warmer than it already is.

The Wikipedia article for Bugey Nuclear Power Plant says "Some of the cooling comes from direct use of the Rhône water (units 2 and 3) while some is done by the use of cooling towers (units 4 and 5)." Cooling towers use evaporation to remove the heat, and water has high enthalpy of vaporization so they'll probably still work even with warmer input water, but if the direct cooling system is not designed to boil the water then it might fail if the input water is too warm.

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

My thought is that hot and humid air is holding more moisture as it is, so it’s harder to evaporate more into it.

If they’re drawing from the river to evaporate, and flows are sluggish (because of evaporation upstream or lack of precipitation), they also have to draw less when they need more.

I live near https://en.wikipedia.org/wiki/Oyster_Creek_Nuclear_Generatin.... When the plant was running, it would suck in so much water that one river would run backwards, pulling in brackish water from the bay (near the outlet of another river), and depositing the outflow into a different river, which went back into the bay about a mile away. Both the inlet side and outlet side were rich fishing and crabbing grounds. Now that the plant is shut down, both the inlet and outlet are nearly stagnant, and all the seafood is gone. The outlet was a particularly popular fishing spot, because the warmer water both attracted more fish and greatly extended the fishing season (even through the winter, when you couldn't catch much elsewhere).

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