The German UfG consortium – comprising Uniper Nuclear Services GmbH, Framatome GmbH and GNS Gesellschaft für Nuklear-Service mbH – has won the contract to dismantle and package the reactor pressure vessel, including the vessel head and insulation, at Switzerland’s Mühleberg NPP (KKM – Kernkraftwerk Mühleberg).

The 373 MWe boiling water reactor plant, some 15 kilometres from the Swiss capital Bern, began operation in 1972 and provided 5% of Switzerland’s electricity. Swiss energy group BKW (formerly Bernische Kraftwerke) decided to close the plant in 2013 for economic reasons and it was disconnected from the grid in December 2019. In 2020 its operating licence was replaced by a decommissioning order.

The consortium will be responsible for dismantling and packaging the reactor pressure vessel (RPV) including calotte and stand frame; the RPV lid; the control rod drive housing; and the RPV insulation with brackets and plates. The total amount of material to be removed is about 270 tonnes. Work is expected to begin at the end of 2025.

UfG’s technology includes the mechanical pre-dismantling of the RPV in the installation position into the largest possible segments. Thermal post-dismantling and packaging for storage then follows.

Decommissioning taking place in three phases. The first phase (planned for 2021-24) includes removal of all fuel assemblies with highly radioactive components from inside the reactor being dismantled and packaged under water. In March 2023, Uniper Nuclear Services – a subsidiary of Germany's Uniper Group – was contracted by BKW to dismantle, disassemble and package the two moisture separator reheaters at Mühleberg. BKW completed defuelling in September 2023.

During the second phase, from 2025, all remaining parts of the system that came into contact with radioactivity will be dismantled. These include the reactor pressure vessel, parts of the containment container or the fuel element storage pool that is no longer required.

All dismantled components will be sorted, cleaned if possible, checked for radioactivity and packed. Cleaned and released material will be landfilled as normal waste or recycled where possible. Building structures that may have come into contact with radioactivity during operation will be inspected and cleaned to ensure that there is no radioactivity left. KKM will submit an application to the authorities for conventional dismantling by 2027. This phase will end with the lifting or clearing of controlled zones. By the end of 2030, KKM should be free of radioactive material and, if no more radiological hazards are identified, the authorities will release the site for new use.

The final phase should demonstrate that the site is no longer a source of radiological hazard. Depending on whether the area will be used for industrial or natural purposes, the area will be available for further use from 2034.

Image: Signing of the contract (courtesy of Uniper)