In 2024, nuclear power plant operators (NPPs) in Switzerland complied with the approved operating conditions. There were 34 reportable nuclear safety events in the year under review, all of which were classified by ENSI as Level 0 on the International Nuclear and Radiological Event Scale (INES).
Emissions of radioactive material from nuclear installations into the environment were once again well below the approved limits during the year under review. Protection of the public and the environment against the effects of radiation was ensured at all times.
Increased number of events
The number of reportable events at operating NPPs increased from 11 last year to 33 in the current year. There were 14 events at Beznau NPP, compared with 7 last year. The increase was partly due to three events resulting from irregularities in the external power supply. Another four events were linked to age-related leaks: three in the chemical and volume control system and one in a feedwater tank. The leaks occurred on components that were installed during the construction of Beznau NPP without being subject to nuclear regulations and were only later assigned to a nuclear safety class following changes to those regulations. ENSI is closely monitoring this issue as part of its regulatory activities.
Gösgen NPP recorded ten events, compared with eight the previous year. Two events involving the ingress of foreign material contributed to the higher number. ENSI addressed this issue as part of an inspection.
The number of events at Leibstadt NPP also increased compared with the previous year, rising by two to a total of nine. Two of the events occurred during the filling of waste containers as part of the solidification of radioactive residues. Leibstadt NPP performed an analysis and used the findings to optimise operations at the solidification plant.
Mühleberg NPP, which is currently undergoing decommissioning, recorded one reportable event in 2024.
The Zwilag Central Interim Storage Facility recorded two events, both of which were rated INES Level 0. The Paul Scherrer Institute and the École Polytechnique de Lausanne recorded no reportable events.
Radioactive waste management
At the end of November 2024, the National Cooperative for the Disposal of Radioactive Waste (Nagra), submitted its general licence applications to the Swiss Federal Office of Energy for a deep geological repository in the North of Lägern site area (canton of Zurich) and an encapsulation plant in Würenlingen (canton of Aargau). ENSI is responsible for the safety assessment and, as a first step, checked the applications for completeness during the year under review.
In preparation for its ongoing assessment work, ENSI examined the relevant technical issues and incorporated them into its regulatory research. This research is being carried out in collaboration with various experts from universities, research institutions and private companies.
