Checking in with … Regina Betz

Sol Kislig, ProClim: Regina Betz, you are co-author of the report “Prospects for Nuclear Energy in Switzerland,” which was published in early July 2025. How do the greenhouse gas emissions of nuclear power plants compare to those of renewable energies?

Regina Betz: Nuclear power plants (NPPs) and renewable energies perform quite similarly in terms of greenhouse gas emissions. Precise calculations depend on many assumptions. We therefore tend to give trends rather than figures. According to Zhang and Bauer (2018), greenhouse gas emissions from nuclear power arise primarily from uranium mining and enrichment. These emissions also depend on the country from which the uranium is imported. For Russia, which is the international leader in the production of nuclear fuel rods, only limited data is available. However, it can roughly be said that, in terms of greenhouse gas emissions, nuclear power plants are on average slightly worse than hydropower, especially river power plants, similar to wind power, but slightly better than photovoltaics.

What is the current status of nuclear energy use in Europe and worldwide?

The latest report from the International Energy Agency (IEA) (2025) shows that new nuclear power plants are currently being built mainly in Russia and China, but only a few in Western countries. In Europe, however, the first two Generation III nuclear power plants—which have similar technology to Leibstadt but a better safety concept—have recently been completed in Finland and France, and two more are under construction in England. There are a few concrete projects in Eastern Europe, while other projects in Western Europe have recently been postponed for several years or until further notice. According to the IEA, the extent to which nuclear power plants will play a role globally also depends on the extent to which governments will provide financial and political support for new nuclear power plants. In France, where the energy mix currently consists of around 70% nuclear power generation and 25% renewable energies, nuclear power is set to continue playing an important role in the future. At the same time, however, replacing the existing 50 or so nuclear power plants within the next 25 years represents a major economic and industrial challenge.

Are nuclear power plants suitable for balancing fluctuations in renewable energies and the additional demand in winter?

When it comes to balancing fluctuations in renewable energies, the possibilities of nuclear power plants are limited. Technically speaking, nuclear power plants can reduce their output, for example when there is strong sunlight. However, they are slower than, for example, hydroelectric storage power plants or batteries, and can only reduce output by up to 50-70%. In addition, any reduction in output puts mechanical strain on the plant and contributes to material fatigue, especially in the lower load range. However, modern reactors can withstand a very high number of such load cycles. From an economic point of view, it is also important to note that frequent reductions in output reduce the overall utilization of nuclear power plants. This can increase the cost per kWh of electricity produced, which has a negative impact on its economic efficiency.

In winter, nuclear power plants can compensate for the seasonally lower generation from hydropower and solar energy. It is possible that higher electricity prices in winter could then also compensate for the potential loss of revenue in summer. It becomes disadvantageous for nuclear power plants if negative prices form on the electricity market in summer as a result of overproduction. These would then even mean expenses, as nuclear power plants cannot completely shut down their production at short notice, as mentioned above.

In view of the heatwave of recent weeks and the associated high air and water temperatures: Are there potential dangers for nuclear power plants due to advancing climate change?

One potential challenge is posed by nuclear power plants that use river water for cooling and then discharge it back into the river. After cooling, the water is several degrees warmer, which can exceed the critical limit for aquatic life in the river if the initial water temperature is high. In Switzerland, however, this only affects the Beznau nuclear power plant, which requires river cooling on a large scale. The Leibstadt and Gösgen nuclear power plants have cooling towers: these require less water for cooling and do not discharge water back into the river. These nuclear power plants are therefore less susceptible to the effects of climate change, particularly in terms of lower water levels and higher temperatures in rivers.

A key component in achieving Switzerland's climate targets by 2050, and thus net zero emissions by 2050, is the electrification of transport and heating. In addition, the demand for electricity from data centers is rising steadily. Are renewable energies sufficient to meet this growing demand, or do we need (new) nuclear power plants?

This question was not the subject of the report; our focus is on nuclear energy. However, there are many studies – including Energy Perspectives 2050+ – that show that we can in principle meet our electricity demand in 2050 without new nuclear power plants. To be fair, it must be said that very few studies currently consider new nuclear power plants as an option at all, because new construction is currently prohibited by law. In studies that allow for nuclear power plants (e.g., NEA Nuclear Energy Agency, 2022, or Darudi et al., 2025), the results vary depending on assumptions about, for example, the costs of a new nuclear power plant, the possibilities for importing electricity, or future electricity prices. Unfortunately, these assumptions are not always presented transparently in the studies.

Of course, whether the electricity agreement with the EU is approved in a referendum also plays a key role here. With this agreement, Switzerland remains part of a large supply system that can respond to growing demand with a variety of technologies and power plants. Without the EU electricity agreement, large nuclear power plants in particular have a problem because they need new reserve power plants to be built in case of an unplanned outage.

The report mentions that a new nuclear power plant cannot go into operation in Switzerland before 2050. Why, then, is nuclear energy even being discussed in the context of net zero targets?

The energy strategy does not currently include nuclear power in its plans to achieve net zero by 2050. And the long time horizon until a nuclear power plant could potentially be built shows that we must do everything we can in the short and medium term to significantly expand renewable energies. In principle, however, nuclear power plants can be an option for a climate-neutral electricity supply, even after 2050, provided there is political will and the population is willing to help finance them.

It is important to us to use our report to show what steps and decisions are needed on a possible path toward a new nuclear power plant. This is a complex process, starting with various necessary legislative changes, through approvals and financing, to construction. Several approvals are required and objections are possible, meaning that a new construction project could fail at various stages. Last but not least, it requires players in the economy who are willing to take on such a project with the associated risks. We would risk a major electricity shortage if we relied on a new nuclear power plant.