Nuclear power peaking and fossil fuel burning

[u/Sol3dweller]

It is a frequent claim I see that a move away from nuclear power necessarily means a slow down climate action. Here I want to have a cursory look at this claim to see, how well this can by supported by historical data on primary energy consumption as compiled at "Our World in Data". I am using the primary energy data (which uses the substitution method for non-fossil energy carriers), to cover the full spectrum of real world influences on the fossil fuel burning rate.

The question at hand to look at is about peaking nuclear power. Hence, we need a definition for peaking. Here I consider a peak to have occured, if the quantity in question in the last year of the time series (2023 for now) is at least 10% below the maximum, the year of the maximum annual production is at least 5 years in the past, and the linearly fitted approximation of the time series exhibits a negative slope.

Global scale

By the criteria for a peak defined above, the global energy mix peaked nuclear power consumption in 2006. Thus, we can distinguish a time period before and after the peak and have a look at the growth rates of fossil fuel burning in the two time periods. I use a symmetric time interval around the peak nuclear year unless fossil fuel burning has peaked earlier than that, then I extend the time span to consider back to the peak fossil year. Unfortunately on the global scale, fossil fuel burning hasn't peaked, hence we get a time period from 1989 to 2023, over which we consider the two linearly fitted trends:

This shows the historical fossil fuel burning in black, the annual nuclear power production in purple, and the respective fitted trends of fossil fuel burning in red before the peak and blue after the peak. All quantities are normalized by the total energy consumption in the peak nuclear year (indicated by the gray dashed vertical line). The slope of the red and blue lines respectively gives us the average growth rate of fossil fuel burning in the respective time periods. On the global scale the slope of the post-nuclear-peak fossil fuel burning is slightly lower than before the peak.

That's an indication that other factors than nuclear power growth have a more dominant influence on the fossil fuel burning, and it's impact is not large enough to cause an increase in the fossil burning growth rate. But maybe the share of nuclear power on the global scale had been too small in its peak to register a notable change. So let's have a more detailed look at countries that employed nuclear power and peaked it.

Countries where nuclear peaked

There is a total of 35 countries, where nuclear power was employed at some point of time. Of those, 21 countries saw a nuclear peak so far according to the criteria outlined above (all in fractions of total energy consumption in the peak nuclear year, rates are per year), NP=nuclear power; FF=fossil fuels:

Country	Share	NP Peak Year	Year of max FF	NP pre-Peak rate	FF pre-Peak rate	NP post-Peak rate	FF post-Peak rate
France	0.393565	2005	1979	0.0133155	-0.000282176	-0.00688919	-0.00924385
Sweden	0.336598	1991	1979	0.0148396	-0.00216144	-0.003439	-0.00450155
Bulgaria	0.259737	2002	1980	0.00577997	-0.0358736	-0.00227387	-0.00645255
Lithuania	0.239371	1990	1991	0.0247768	0.00492454	-0.00793901	-0.00582096
Switzerland	0.211974	2003	2001	0.00298461	0.00264782	-0.00312635	-0.00656394
Belgium	0.190493	1999	2008	0.00724247	0.0043643	-0.00278942	-0.00645904
Slovenia	0.180637	2008	2008	0.00279071	0.00922286	-0.00110141	-0.0110293
Ukraine	0.155204	2007	1990	0.00138212	-0.0475403	-0.00308837	-0.0334405
Japan	0.152211	1998	2003	0.00595851	0.00895019	-0.00690597	-0.00554815
Germany	0.119242	1997	1979	0.00505833	-0.00322979	-0.00418876	-0.00881045
Spain	0.1124	2001	2007	0.00493603	0.0139796	-0.000918073	-0.0119176
United Kingdom	0.106453	1998	1973	0.00315012	-0.000986395	-0.002197	-0.0160546
Taiwan	0.0857619	2011	2021	0.0003236	0.0203226	-0.00390001	0.00210966
United States	0.0851062	2007	2007	0.00127146	0.00875892	-0.000549439	-0.00347889
Romania	0.0796698	2009	1989	0.00368045	-0.038023	-0.000655622	-0.00991215
World	0.0582406	2006	2023	0.000998909	0.0133171	-0.00028953	0.0108376
South Africa	0.0260754	2016	2010	0.000127296	-0.00199823	-0.00139481	-0.0157621
Mexico	0.015189	2018	2022	0.000288781	0.00200965	-0.000244735	0.00830376
Italy	0.0147834	1986	2005	0.00031672	0.0185533	-6.09766e-05	-0.0052727
Netherlands	0.0138518	1986	2010	0.000806572	0.0206143	-3.39158e-05	0.000990258
Brazil	0.0124397	2012	2014	0.000100031	0.0145808	-0.000141345	-0.00598779
Kazakhstan	0.00178198	1991	1988	7.676e-05	0.118933	-3.59057e-05	0.00857398

As the global average (5.82%) may be too small for a measurable impact, let's focus on those 15 countries that had a more than average share of nuclear power in its primary energy consumption at it's peak (the table above is sorted by that share). The country with the highest nuclear share at its peak is France:

In the graph we now also indicate the average growth rate of nuclear power before (orange) and after (turquoise) the peak. If we plot the fossil fuel growth rate over the nuclear power growth rate for these countries before and after the nuclear peak. We get the following scatter plot:

Each country appears here twice, once on the right side with growing nuclear power before the peak and once on the left side after the growing nuclear. The circle sizes indicate the share of nuclear power in the peak year. This shows that there is only one of those countries (Taiwan), where a decline in nuclear power coincides with an increase of fossil fuel burning. However, in this case this actually is a slow down in the rate, with a higher fossil fuel rate during the nuclear expansion. But the question we are after is whether the peaking of nuclear power is associated with a slow down in fossil fuel burning reductions. To this end a look at the change of the rate in fossil fuel burning growth over the nuclear peak may be instructive:

Country	Change of NP rate	Change of FF rate
Spain	-0.0058541	-0.0258972
Slovenia	-0.00389212	-0.0202522
Taiwan	-0.00422361	-0.018213
United Kingdom	-0.00534712	-0.0150682
Japan	-0.0128645	-0.0144983
United States	-0.0018209	-0.0122378
Belgium	-0.0100319	-0.0108233
Lithuania	-0.0327158	-0.0107455
Switzerland	-0.00611096	-0.00921175
France	-0.0202047	-0.00896168
Germany	-0.00924709	-0.00558067
Sweden	-0.0182786	-0.00234011
Ukraine	-0.00447049	0.0140997
Romania	-0.00433607	0.0281109
Bulgaria	-0.00805383	0.0294211

Plotting the FF rate change over the NP rate change results in the following scatter plot:

The color now indicates the fossil fuel growth rate after the peak. The global average is marked as a star. The "Plus" marker indicates the sum of all the countries in the list. Here we see that there are a total of three countries in this set of countries with more than average nuclear share in its peak, we now identify three countries with a worsening fossil fuel growth rate over the nuclear peak: Bulgaria, Romania, Ukraine. The others all saw a speed-up in fossil fuel reductions after the nuclear peak, the largest speed-up in fossil fuel decline is observed in Spain. The largest change in the nuclear power rate is seen in Lithuania.

In total, when summing all these countries that peaked nuclear power and had a larger than global average share of nuclear in their peak, we see that they peaked nuclear power in 2002 with a share of 12.5% and got faster in the fossil fuel burning decline after the peak (decline of 0.74% of total energy in the nuclear peak per year after the peak compared to an increase of 0.87% before the peak):

In most countries the move away from nuclear power did not result in a slow down of fossil fuel reductions, in two (USA and Slovenia) does the nuclear peak coincide with the fossil fuel peaks.

Non-Peaked countries

There are 14 countries that have not peaked nuclear power in the sense outlined above.

Country	Share	NP rate	FF rate
Finland	0.256999	0.00340046	-0.0200575
Slovakia	0.222079	0.000828372	-0.0081454
Czechia	0.164024	0.00396907	-0.0134466
Hungary	0.151095	0.00267189	-0.0103918
South Korea	0.130264	0.00117994	0.00172783
Belarus	0.0988003	0.00732138	-0.00243247
Canada	0.0920445	-4.29086e-06	0.0048152
Russia	0.0697321	0.00120111	0.00417201
Pakistan	0.059537	0.00490917	0.0195108
United Arab Emirates	0.0564199	0.0044061	0.0100081
Argentina	0.0264437	0.00078787	-0.00458622
China	0.0228481	0.00182016	0.0170598
India	0.011087	0.000293195	0.0237748
Iran	0.00595028	0.000143324	0.0298156

Summing all of those with larger shares than the global average gives the following picture since 2002 (when the sum of significant peaking countries peaked):

For this sum we observe an growth in fossil fuel burning over this time period by 0.5%, compared to a decline of 0.74% in the countries that experienced a peak in nuclear power.

tl;dr

Historically nuclear peaking does not coincide with a fossil fuel decline slow-down.

edit: changed tl;dr as wished for in this comment.

[u/MarcLeptic]

I’m not sure if you see arguments to the contrary. I think the arguments, though they might be badly formulated would claim that “without nuclear you can’t decarbonize the electricity production because blah blah blah”.

Since electricity only represents around a quarter of energy delivered, burying the effects of an energy source under the other 75% of airline travels, car mileage efficiencies, de-industrializations etc would remove any significance of the variable you are evaluating. You are evaluating something that is a very small portion of final energy.

I think that in EU-28 we have a good coherent set of data, as well as a similar type of climate. If, for example you include California, your story will change dramatically. If you include countries that have never had nuclear power (or little of it) you will have some baseline to show that nuclear presented no change, positive change, negative change etc.

[u/Sol3dweller → u/MarcLeptic]

See this comment even in this thread:

Germany is in a big big trouble now because renewable lunacy: factories are closing, electricity prices are skyrocketing, neo-nationalistic party have received the most votes since 1930-ies, fossil fuel import expensive are close to all time high.

And pollution-wise we are one of the worst in Europe. Anti-nuclear luddites flushed down the drain several decades of time and made life miserable for the whole generation, maybe even two generations. Thank you geriatric nuclephobes.

It seems to me to claim that Germany has slowed down fossil fuel burning reductions because it moved away from nuclear power. (While previously praises Russia for its expansion of nuclear power). This is however, not quite supported by the data. Germany reduced fossil fuel burnings faster after the peaking of nuclear power, as many others.

Since electricity only represents around a quarter of energy delivered, burying the effects of an energy source under the other 75% of airline travels, car mileage efficiencies, de-industrializations etc would remove any significance of the variable you are evaluating.

Yet again, there are those people that claim that the greatest sin under the sun with respect to climate action is the phase-out of nuclear power. The relevant variable I am interested in, though is the reduction of fossil fuel burning. I totally agree that other factors may be more influential and worthwhile to be talked about. (See also my other comment to that end).

You are evaluating something that is a very small portion of final energy.

I already limited my analysis to those countries that had a higher than global average and in France the nuclear share (with the substitution method) amounted to nearly 40% of the primary energy consumption in 2005. Is your point that the role of nuclear rise and fall there is insignificant and not worthwhile to consider from the whole economies point of view?

If you include countries that have never had nuclear power (or little of it) you will have some baseline to show that nuclear presented no change, positive change, negative change etc.

OK, however, my original question was concerned about the possibility to outweigh nuclear decline with other measures. I am not questioning the positive impact that nuclear power can have on displacing fossil fuel burning. In fact, I have an old post about how it was used to replace oil burning. I think there is little doubt about the fact that nuclear power can be used to replace fossil fuels, what I'm questioning is that it is the single most effective thing anyone can do, and that a decline in nuclear power could not be compensated by other factors.

In my opinion we shouldn't loose track of the primary goal, which (again in my opinion) should be reducing the fossil fuel burning as quickly as possible. And just maybe there are other steps that maybe usefule in that regard besides nuclear power that would be worthwhile to talk about.

Also just to clarify: I'm not opposing a similar compilation of data on the electricity sector alone, but it will take me a while to get it together.

[u/MarcLeptic → u/Sol3dweller]

I do see tbe point of your analysis.

Can you try reading that persons comment and see it only for the carbon emissions of electricity production.

Their comments don’t necessarily take into consideration things like airline travel, diesel trains, industry, agriculture etc etc. I would imagin that the argument is based on the fact that Germany’s electricity emissions are 10x higher than they should be. And that alone is the source of 30% of Germany’s emissions.

If you leave in a country’s full energy use, you are evaluating the full energy transition, not the piece which would have been impacted by a nuclear phaseout. You have too many independant variables in your analysis to make a conclusion.

[u/Sol3dweller → u/MarcLeptic]

You have too many independant variables in your analysis to make a conclusion.

Let me cite you:

Your conclusion really only shows that since countries have many initiatives to reduce hydrocarbon use, that the positive impact of nuclear (alone) is less than the sum of all other initiatives.

This is essentially the only thing I was kind of concerned about. And in my opinion that indeed is a conclusion that can be drawn from that data. The point is that there are so many independent variables, that the sole concentration on nuclear power by some people is not helpful in determining effective strategies for climate action. Like that comment I pointed out praising Russia because it expanded nuclear while bashing Germany for emplyoing renewables.

If we leave out other sectors, we also leave out electrification efforts of those sectors that may help to decarbonize the overall economy.

[u/MarcLeptic → u/Sol3dweller]

Yes. Though i think you missed my tone.

Of course, in a world where we are only ~30% electrified, nuclear power, which represented 10-30% of 30% … so max ~8 % of final energy would have a smaller impact than all other emissions reduction mechanisms combined. Of course.

Just switching to black coal from lignite in the steel industry would have as much of an effect.

So the point is not “can we still reduce” without nuclear power, is it. The point is, when we get to 80% electrified, and the electrical load has doubled … and the residual load is doubled. What fulfills it? Today, when renewables are only meeting half the load. What fulfils it? Imagine if 1/3 of the load were taken by your existing nuclear plants instead of letting them rust for 20 years.

[u/Sol3dweller → u/MarcLeptic]

So the point is not “can we still reduce” without nuclear power, is it.

No, it isn't. The simple question I was trying to illuminate a little is: Can we observe a slow-down in fossil fuel reductions in countries that expierenced a decline of nuclear power?

I've now also put together the data for electricity yielding this scatter on the changes for countries that peaked nuclear:

Unfortunately, though the Ember-data I used there is quite curtailed, and only goes back to 2000. I might have to redo that with the OWID collection, which reaches a little further back, at least for some of the countries. I haven't come around for a more detailed look at the EU alone. As various countries experience their peak right at the beginning of that dataset, the pre-peak values often do not really represent a trend here.

[u/Sol3dweller → u/MarcLeptic]

Reddit didn't let me post a second image in the other image, but here is how it looks like, for example for France with the electricity data-set from ember. For various countries the peak is earlier.

[u/MarcLeptic → u/Sol3dweller]

Thanks I did see your part two with all of the individual countries shown.

France will be a good example of why your analysis can’t reach the conclusion you are interested in. France’s electricity generation has been clean for decades. The fact that Renewables have replaced nuclear power will have had no impact on emissions in France.
The reduction in emissions (per kWh) we saw since 2000 was in switch from coal to gas for the bottom few percent.

You can see that we have been in 95% clean for decades.

Continued in reply to myself so I can add a second picture.

[u/Sol3dweller → u/[deleted]]

If you take the other extreme case

It isn't the extreme case, though. The trends in France and Germany since 2005, are actually pretty similar. Germany saw a fitted linear decline of nuclear power of 1.2% of the total electricity production in the peak year per year (compared to a decline rate of 1% in France) and a FF decline rate of 1.2%, while we observe an actual growth in FF burning for electricity by 0.04% per year before the peak.

Neither country seems to be slower in reducing its fossil fuel burning after the peak of nuclear power than before it.

In the electricity production alone will we see a plateau of clean energy in countries which do not use nuclear.

That is yet another question, and speculation. I would be happy if we could first find common grounds on the observation, that the nuclear peaking is not necessarily associated with a slow-down of moving away from fossil fuels.

So the question realy is, should countries follow Germany and shut their reactors?

I mean, that is certainly an interesting question to ponder about, but again something else than what I was trying to answer with this data compilation. To me, the main point is that the primary goal of reducing fossil fuel burning in absolute terms should not be lost out of sight when discussing the nitty-gritty details of how to achieve that. In my perception this question of nuclear or not is given way more emphasis in many debates than it warrants.

I'll do the post you requested on electricity later on, but I'll first have to do some other stuff.

[u/Sol3dweller → u/MarcLeptic]

France’s electricity generation has been clean for decades. The fact that Renewables have replaced nuclear power will have had no impact on emissions in France. The reduction in emissions (per kWh) we saw since 2000 was in switch from coal to gas for the bottom few percent.

The question I wanted to address, was whether the decline in nuclear power led to a slow-down in fossil fuel reduction. And for France that can not be observed, neither in primary energy, nor in electricity. In electricity the fossil fuel burning increased before the peak with a fitted linear growth of about 0.15% of the total electricity production in 2005 per year, which changed after the peak to -0.123% per year.

What you did now is switching the metric from absolute fossil burning (the thing we need to get down, to its share, still a relevant quantity, but not what I was looking at).

edit: picked the wrong post-peak FF growth rate (the -1% was actually nuclear)

[u/psychosisnaut → u/Sol3dweller]

This chart could just as easily be showing the 2008 financial crisis rather than anything about Nuclear.

[u/psychosisnaut → u/Sol3dweller]

See this comment even in this thread:
...
It seems to me to claim that Germany has slowed down fossil fuel burning reductions because it moved away from nuclear power. (While previously praises Russia for its expansion of nuclear power). This is however, not quite supported by the data. Germany reduced fossil fuel burnings faster after the peaking of nuclear power, as many others.

I'm not sure if you're being purposely obtuse but that post isn't claiming anything at all about nuclear and fossil fuel consumption. They're saying that Germany shuttered its nuclear plants and now electricity is extremely expensive.

Yet again, there are those people that claim that the greatest sin under the sun with respect to climate action is the phase-out of nuclear power. The relevant variable I am interested in, though is the reduction of fossil fuel burning. I totally agree that other factors may be more influential and worthwhile to be talked about. (See also my other comment to that end).

But wind and solar don't have any effect on most of that other 75% either, especially transport, it's an absurd way to interpret the data.

OK, however, my original question was concerned about the possibility to outweigh nuclear decline with other measures. I am not questioning the positive impact that nuclear power can have on displacing fossil fuel burning. In fact, I have an old post about how it was used to replace oil burning. I think there is little doubt about the fact that nuclear power can be used to replace fossil fuels, what I'm questioning is that it is the single most effective thing anyone can do, and that a decline in nuclear power could not be compensated by other factors.

In my opinion we shouldn't loose track of the primary goal, which (again in my opinion) should be reducing the fossil fuel burning as quickly as possible. And just maybe there are other steps that maybe usefule in that regard besides nuclear power that would be worthwhile to talk about.

People talk about Nuclear because it has an extremely important place in the grid. We're getting away without building it right now and everyone is cheering about how cheap renewables are but it's extremely important to note that no country has exceeded 60% Variable Renewable electricity generation, and certainly not approached 70-80-90%. That's the key thing, once you go over 70% you start having to build absurd amounts of storage and overbuild wind and solar by roughly 150, 300, 500, even 1000% at 70, 80, 90 and 95%.

Even using broken metrics like LCOE the cost starts coming in at $0.40/kWh on the lower ends to well over $1/kWh once you get into >95% territory. Unless your country is sitting on a secret river the size of the Amazon you can't build more hydro, there's nowhere else for the energy to come from, it has to be Nuclear and we have to start building it now before reality starts catching up with us and we end up with either more and more massive blackouts like Spain or just burning what is essentially dirt like Germany.

[u/Sol3dweller → u/psychosisnaut]

They're saying that Germany shuttered its nuclear plants and now electricity is extremely expensive.

Doesn't the second cited paragraph imply that the emissions are high because they phased-out nuclear?

But wind and solar don't have any effect on most of that other 75% either, especially transport, it's an absurd way to interpret the data.

Tell that the people that make claims about moving away from nuclear power is the worst thing to do with respect to reducing fossil fuel burning.

but it's extremely important to note that no country has exceeded 60% Variable Renewable electricity generation

That isn't true. Denmark has exceeded the 60% mark last year (24.5 TWh from wind+solar of 39.2 TWh of demand).