SGs dismantled at Mülheim-Kärlich

Above: Decommissioning of steam generators in confined spaces

THE MULHEIM-KARLICH NUCLEAR POWER plant, a 1300MW pressurised water reactor, is located in Rhineland-Palatinate in Germany. The reactor operated for just 13 months between 1987 and 1988 before being shut down.

Decommissioning work has been underway at the power plant since 2004. Energy provider RWE, headquartered in the German city of Essen, commissioned industrial services provider Bilfinger to dismantle the unit’s two steam generators in 2017.

Bilfinger successfully completed the project in December 2020.

“The safe and successful completion of the project shows that our concept for nuclear decommissioning is effective. It allows our customers to efficiently dismantle major components of former nuclear power plants,” says Tom Blades, CEO of Bilfinger.

“Together with our customer RWE, we have been able to overcome all the challenges of this complex task in a spirit of partnership”.

Bilfinger says that as decommissioning of first generation nuclear power plants was not a priority during planning, the tight space conditions create logistical challenges, especially when it comes to the dismantling of large components.

To deal with the difficult conditions in the confined spaces, Bilfinger Noell developed a dismantling concept that met both the stringent safety standards of a plant undergoing decommissioning and RWE’s overall schedule for the process.

The steam generators were dismantled in-situ, avoiding cost-intensive conversion measures and special transports to an offsite location for dismantling.

The steam generators, which were around 23 metres high with a diameter of around 4 meters were dismantled using specialist saws from HILTI, which had been adapted by Bilfinger for use in a nuclear power plant.

Changes to the wire storage, expansion of the cooling system and modification of the decontamination properties were needed to ensure precise application of the powerful saws in the nuclear environment. This meant two portal wire saws could be used as cold cutters in the control area of the plant.

The free release measurement of the dismantled shells of the two steam generators — which make up a large part of the total mass — was completed and the shells were fed into the conventional recycling system. The inner workings of the steam generators — 16,000 finger-thick tubes each— were expertly packaged as radioactive waste in approved containers. They will be transported to an interim storage facility in 2021 before they reach the final storage facility at Schacht Konrad.

“With the dismantling of the steam generators that has now been completed, we are taking another major step forward in the safe and on-schedule decommissioning of our former nuclear power plant in Mulheim-Karlich,” said Nikolaus Valerius, chief nuclear energy officer at RWE Power and technical director of RWE Nuclear.

Expertise incorporated during this project is already being incorporated into other joint dismantling activities at other locations, Bilfinger says.