Recently, an editor from Handelsblatt wrote to me in a comment on LinkedIn that nuclear power plants would not help with the energy transition, stating that nuclear power plants would not be controllable and would not help us with the energy transition.
Now I felt challenged and researched what the controllability of nuclear power plants actually looks like, since it was written that the controllability of nuclear power plants is not given, as it is with gas-fired power plants and one could thus justify the construction of new gas-fired power plants.
Now, people still seem to think that nuclear power plants are magical technology, but ultimately it's just a thermal power plant, like gas and coal, only the form of energy is different. To control a nuclear reactor, there are control rods, these are moved out of the reactor so that nuclear fission can occur, this causes the water to heat up and then drive a steam turbine, which then produces electricity via a generator. If you want to reduce the output of the nuclear reactor, you move the control rods back into the reactor, thereby reducing the output and controlling the reactor.
Not that complicated, is it?
Nuclear power plants are controllable
KIT, the Karlsruhe Institute of Technology, has developed a PDF document from July 2016 / Fallback (WebArchive) how flexibly nuclear power plants can be operated. And the following paragraph can be found there:
From their operating manuals
that power changes in the range close to the nominal power (this is the
highest output that can be achieved when operated as intended)
to up to 10 % per minute are possible.
This is significantly faster than, for example, with
Coal-fired power plants State of the art
(between 2.5 and 4 %/min). Only Gas turbines are equipped with 12 %/min still
can be regulated more quickly.
So the logical question arises here: why argue that nuclear power plants do not help with the energy transition if they can be regulated more quickly than coal-fired power plants, which keep the electricity grid running in Germany when there is not enough imported electricity or insufficiently good weather for solar and wind?
And then you argue that nuclear power plants are not flexibly controllable and gas-fired power plants are, so you have to build 40-50 gas-fired power plants now so that you can phase out coal in 7 years, in 2030.
For a 2% faster regulation per minute, while nuclear power plants are 2.5-4 times faster than coal.
Instead of operating 8 nuclear power plants in Germany with low CO2 emissions, you would rather build 40-50 gas-fired power plantswhich cause more CO2, will later burn hydrogen, which does not even exist yet and it is questionable where it will come from in large quantities from renewable energies in order to be able to supply 40-50 gas-fired power plants throughout Germany...
France's nuclear power plants show how controllability works, because there they cover the base load and can be operated variably, not volatile according to the mood of the weather, otherwise according to consumer demand. The advantage is that if enough renewable energy is supplied, the output of the nuclear power plants can be reduced, which saves fuel, and if there is less energy from renewable sources, several hundred megawatts of power can be provided within a few minutes without the need for batteries.
However, it must also be said that a nuclear reactor is a complex system that cannot simply be switched on and off. And so the load following capability is dependent on the current power, so the power increases from 20 % to 100 % by only 2 %/minute. Whereas the power can be increased by 10 %/minute from 80 % to 100 %.
It also depends on whether you have a boiling water reactor or a pressurized water reactor.
For the NPP Isar 2 the following power gradients were defined in the operating manual: 2 % per minute for power changes in the range from 20 to 100 % of the rated power, 5 % per minute in the range from 50 to 100 % of the rated power and 10 % per minute in the range from 80 to 100 % of the rated power.[14]
Nuclear power plants are therefore well suited for base load and stable output, but less suitable for absorbing peak loads, where gas-fired power plants can show their real strength and regulate output more quickly.
The picture shows the Cattenom nuclear power plantReactor 2, which was running at low power on November 13 and then ramped up further in the evening when energy demand increases because people come home and heat their homes more.
In the picture: Cattenom nuclear power plant, reactor 2, from November 13, 2023, here it goes to the detail page of nuclear-monitor.fr
Further information:
Technical and Economic Aspects of Load Following with Nuclear Power Plants (OECD NEA, PDF)
English 
German 
French 
Czech