Uniper Nuclear Services - a subsidiary of Germany's Uniper Group - has been contracted by Swiss utility BKW to dismantle, disassemble and package the two moisture separator reheaters (MSRs) at the Mühleberg nuclear power plant in Switzerland.

(Image: Uniper)

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. Mühleberg is the first nuclear power plant in Switzerland to be decommissioned.

In September 2020, the decommissioning of Mühleberg began with the first of three decommissioning phases. During this first phase, among other things, the MSRs assigned to the two turbo groups with the associated systems, structures and components are to be dismantled, disassembled and packaged.

MSRs are installed after high-pressure or intermediate-pressure turbines. Their purpose is to reheat cycle steam and remove cycle steam moisture. A moisture separator reheater has a length of about 13 metres and a diameter of about 4.1 metres. The total dismantling mass of this project is about 180 tonnes. The work on site is scheduled to start in May this year, with completion set for the first quarter of 2024.

"In order to be able to dismantle the two moisture separator reheaters, we have developed a concept that takes into account the limited space conditions on site and has a high proportion of semi-automated mechanical dismantling techniques for the protection goal-oriented design," said Uniper Nuclear Services Managing Director Michael Bächler.

The dismantling of large components and the parallel reassembly and packaging in a separate work area are intended to speed up the decommissioning work on site, Uniper said. The work areas around the moisture separator reheaters are first housed and an additional crane is brought in to handle the dismantled parts. In this way, mainly self-sufficient dismantling processes are to be made possible.

Mühleberg will be dismantled in three decommissioning phases. The first phase lasts until all the plant's fuel assemblies have been removed, which is expected in 2024. The second phase ends with the lifting or clearing of controlled zones, probably around 2030. The third phase includes work to demonstrate that the system is no longer a source of radiological hazard, which is scheduled for 2031. The site is expected to available for other uses from 2034 onwards.