Mühleberg decommissioning on track

The plant - comprising a single 373 MWe boiling water reactor - began operations in 1972 and was shut down on 20 December 2019. Dismantling operations began on 6 January 2020. However, it has only been considered permanently out of service since 15 September 2020 when its operating licence was replaced by a decommissioning order.

Mühleberg will be dismantled in three decommissioning phases (SP). SP1 lasts until all the plant's fuel assemblies have been removed, which is expected in 2024. The Swiss Federal Nuclear Safety Inspectorate (ENSI) approved SP1 in June 2020. SP2 ends with the lifting or clearing of controlled zones, probably around 2030. SP3 includes work to demonstrate that the system is no longer a source of radiological hazard, which is scheduled for 2031.

The removal of the plant's fuel assemblies to the Zwilag interim storage facility in Würenlingen started as planned in April 2022 and will take about two years. The first two of a total of eight fuel removal campaigns have been successfully completed, with 102 of Mühleberg's 418 fuel assemblies already transferred to Zwilag. There they were successfully reloaded into two Castor storage casks.

Large parts of the plant, such as the turbines and generators, have been removed from the turbine building to make room for facilities for handling dismantled material. In the reactor building, several hundred tonnes of material above the reactor have been removed. In addition, the systems that have become obsolete are being dismantled at many points in the reactor and turbine buildings. In the past two and a half years, 4800 tonnes of material have been dismantled.

In anticipation of the fuel transfer being completed by early 2024, BKW submitted its application to ENSI at the end of June for the second decommissioning phase.

During that phase, all remaining plant components that have come into contact with radioactivity will be dismantled, treated and cleaned. These include, for example, the reactor pressure vessel, parts of the containment or the fuel element storage pool that is no longer required.

By the end of 2030, Mühleberg will be free of radioactive material, with conventional dismantling set to begin in 2031. BKW plans to submit an application for conventional dismantling to the authorities by 2027.

The site is expected to available for other uses from 2034 onwards.