Is it not possible to only run nuclear power plants when there is not enough renewable energy available?

Starting up a nuclear power plant is a complex process that takes several days. A great number of parameters must be optimised to perfectly manage the chain reaction in the reactor.

For example, the nuclear fuel must be properly positioned, the chemical composition of the water in the reactor must be correct down to the millilitre, the right pressures and temperatures must be achieved, etc. Our nuclear power plants are designed as so-called "baseload plants" and are intended to produce electricity stably and safely all year round, regardless of weather conditions.

However, our nuclear power plants are still complementary to renewable energy. For the past few years, our experts, under the supervision of the Federal Agency for Nuclear Control, have been conducting thorough safety studies. These studies showed that, within certain limits, their power output can be temporarily reduced if there is a lot of renewable energy available. This is called "modulation." This modulation is currently happening on a regular basis, by the way.

Certain power plants are allowed to drop 25% in power output up to 5 times per year for up to 6 hours. Other power plants are capable of dropping up to 50% in power output, up to 30 times, every 18 months for up to 72 hours. To do this in a perfectly safe way, however, it is necessary to start the necessary preparations at least 24 hours in advance. Sometimes additional constraints apply that make modulations temporarily impossible for a particular plant, such as a maintenance that needs to be done or the duration that the fuel is in the reactor. 

In conclusion, our nuclear power plants and renewable energy can go hand in hand and stand strong together in the fight against climate change.

Our nuclear power plants are intended to produce electricity stably and safely all year round, regardless of weather conditions.