The Swiss nuclear power plants were built to last 40 years. But because the expansion of renewable energies is stalling, they are expected to remain on the grid for 60 years or even longer. How is that supposed to work? A visit to Leibstadt, the largest nuclear power plant in Switzerland.
The steam from the 144-meter-high cooling tower appears to mix with the low-hanging clouds. The crows that glide past the huge concrete building seem tiny. In the visitor center at the Leibstadt nuclear power plant, a group of young people walk through the exhibition, slightly bored. On the first floor of the circular glass building, power plant manager André Hunziker awaits us in a large meeting room. We meet him to ask him a simple question: How do you actually renovate a nuclear power plant?
The question is very topical. When the Leibstadt nuclear power plant began operations on December 15, 1984, it was assumed that it would be over after 40 years. That would be in almost exactly eight months. But now things look completely different. The system, built between 1974 and 1984, will run significantly longer.
And not just her. The same applies to the other Swiss nuclear power plants: 60 is the new 40 – at least. Even the plant in Beznau, one of the oldest nuclear power plants in the world, has recently been testing an operating life of over 60 years. If you ask around in the industry, it is said that lifespans of 80 years are possible for the plants in Leibstadt and Gösgen – the two largest Swiss nuclear power plants.
Nuclear power plant as a supporting pillar
The reason for this development: The expansion of renewable energies is not progressing quickly enough, and at the same time we need more electricity. This makes the existing nuclear power plants into long-term pillars of supply – especially in winter, when they produce up to 50 percent of the electricity required. For the electricity giants Axpo and Alpiq, the main owners of the nuclear power plants, the so-called long-term operation of the plants is the dominant topic.
But how is it possible to keep such a highly complex facility like a nuclear power plant running for so much longer than originally thought? And: What about security if the operating time is extended so much?
Power plant manager André Hunziker took three hours to explain all of this. Before he goes through his 40-page set of slides, coffee and cake are served. The Aargau native has been working in the energy industry for decades. For years he operated gas turbines all over the world for the then BBC. He has been working in Leibstadt since 2011. Before he took over management of the plant in 2023, he was head of the electrical engineering department and responsible for a wide range of projects that are relevant to long-term operation.
Plan and build relentlessly
If you look over the nuclear power plant on this cloudy day, it looks like an unchanging monolith, with hardly a soul in sight. But the impression is deceptive, as it quickly becomes clear in conversation with Hunziker: the facility is constantly being planned and built.
The reactor is shut down for inspection once a year. Every May, the additional parking lot nearby fills up. The facility’s 500 permanent employees are joined by 1,000 more from suppliers and external companies.
During the standard overhaul, many machines are dismantled, checked for damage and aging, maintained and reassembled, weld seams are X-rayed, measurements are taken and much more. “Many parts of a nuclear power plant are dismantled and reassembled once a year – this doesn’t happen with any other technical facility of this size,” says Hunziker.
This takes at least 25 days. But currently 30 to 35 days are necessary. The reason: “We want to invest a lot more in long-term operation,” says Hunziker. Over 200 projects are pending: more modern monitoring of radiation, increased digitalization, the use of robots or improvements in electronics and machines.
Milliardeninvestition
Around 1 billion francs will be needed for this over the next ten years. This means the plant will be able to operate for at least 60 years, says Hunziker. In order to handle all the projects, he wants to hire 70 additional employees this year and next. Finding staff is difficult but doable, says the power plant manager. The image of nuclear energy has improved among young people – “and which industry today can guarantee jobs for twenty, thirty or even more years”?
The situation with a nuclear power plant is much more complicated than, for example, with a house where the owner has to decide whether to demolish it or even renovate it. For example, the law requires operators to continuously monitor the aging of their system. Every ten years they must also submit a comprehensive analysis to the supervisory authority, called a “periodic security review”.
The penultimate inspection included almost 20 federal folders, which employees personally brought to the Federal Nuclear Safety Inspectorate in Brugg AG. The supervisory authorities did not hesitate: their first answer was around 400 pages long. The documents can now be submitted digitally. The last inspection dates from 2022 and also includes an additional safety certificate for the long-term operation of Leibstadt from the 40th year of operation.
There are also other requirements, such as the so-called obligation to retrofit, which many other countries, unlike Switzerland, do not have. Operators must follow the international development of nuclear technology. If you come across new technologies somewhere that reduce the risk posed by your system, you must implement them.
There is only one restriction: the retrofitting must be “appropriate,” according to the law. This means: The effort must be justifiable in relation to the security gain. The obligation to retrofit means that Swiss nuclear power plants are safer than comparable, non-retrofitted plants abroad, says Hunziker.
Looking into the crystal ball
The Leibstadt nuclear power plant also has its own internal planning tool to assess long-term operation. It’s called “operational duration management”. With every project that the experts tackle, they ask themselves: How exactly do we have to carry it out so that we can achieve a lifespan of 60 or more years? And above all: what about the economics?
The economic viability, in turn, depends heavily on future electricity prices. And that makes planning like looking into the crystal ball: electricity prices can only be reliably predicted a few years in advance, if at all. The operators of nuclear power plants, on the other hand, have to start planning key projects a decade before a project is implemented.
This can be seen in an essential part of the system: the diesel generators. The nuclear power plant has several of them. They can be fired up immediately to power security systems in an emergency. Only: The Leibstadt nuclear power plant has to replace them because the manufacturer will only service the machines for a few more years. “If we couldn’t replace them adequately, we would have to shut down our nuclear power plant at the beginning of the next decade,” explains Hunziker.
Hunziker and his people are already evaluating other suppliers who meet the high requirements for devices for use in nuclear power plants. But the change takes a lot of time: “We had to allow eight to ten years to replace the diesel generators,” says the power plant manager. For example, the supervisory authority wants proof that the new type of device is at least as safe as the one that was previously used.
Problem spare parts
Similar complex questions arise in almost every one of the 200 ongoing projects. For example when purchasing machines. The specialists have to consider how they can ensure that they have enough spare parts for the remaining operating life. If too few are available, operators run the risk of having to shut down machines earlier than planned – and as a result, in extreme cases, the entire nuclear power plant. One solution is to stock enough spare parts. Another: to conclude contracts for the delivery of spare parts.
The reliability and service life of nuclear power plant components can also be increased through increased maintenance. For example, sensitive parts are replaced more often than absolutely necessary. Or important system parts are completely replaced and modernized straight away – the “maximum solution,” as Hunziker explains. One example is the control technology with which the nuclear power plant is monitored and controlled: When the plant went online in 1984, this was analog. Now it is completely digitalized.
According to Hunziker, one thing is clear: safety is the top priority. Projects that reduce safety would have “no chance” with the supervisory authority anyway, he says.
Nuclear heart
In a nuclear power plant you can “replace more or less everything,” as Hunziker explains. However, there is one area where this is not possible: the reactor pressure vessel, the nuclear heart of the plant. The reactor pressure vessel in Leibstadt is made of at least 15 centimeters thick steel and is surrounded by 1.5 meter thick reinforced concrete walls. If it no longer meets the safety requirements, it cannot be replaced and operations will have to stop, says Hunziker.
But how do you know whether the reactor pressure vessel is suitable for long-term operation? This is ensured with regular ultrasound tests. Material samples that come from the original manufacturing process are also installed in the reactor pressure vessel. They are arranged in such a way that they are subject to even greater stress than the materials of the pressure vessel itself. They are periodically removed and compared with identical, unirradiated material samples to identify changes. Similar processes are used for components such as cables. The concrete, another possible weak point, is also monitored.
The three hours are long over and the visitor center has emptied. Hunziker calls up the last slide, then closes his computer. The result of the clarifications is clear: “There is nothing wrong with long-term operation of our system.” And these achieve comparable safety standards to newly built nuclear power plants – thanks to the improvements that have already been made and those that are currently being planned.