Decomissioning work has been underway at the Mülheim-Kärlich nuclear power plant since 2004. RWE, the energy provider headquartered in the German city of Essen, commissioned industrial services provider Bilfinger to dismantle the two steam generators, each of which weighs 450 tons, in 2017. Bilfinger successfully completed the project in December 2020 - an important milestone for RWE in the decommissioning of the former nuclear power plant.
"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".
The eventual decommissioning of nuclear power plants of this generation was not a priority during their technical planning. Today, 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 of the control area, Bilfinger Noell, a Bilfinger subsidiary in Würzburg, Germany, developed a dismantling concept that met both the stringent safety standards of a plant undergoing decommissioning and RWE's overall schedule for the process.
"In addition to technological expertise, the spirit of partnership that marked the outstanding cooperation with Bilfinger was key to the success of the project," says Nikolaus Valerius, Chief Nuclear Energy Officer at RWE Power and Technical Director of RWE Nuclear. "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 Mülheim-Kärlich".
Application of the innovative technical solution from Bilfinger Noell meant that RWE was spared cost-intensive conversion measures as well as costly special transports to an offsite location for dismantling. The process did, however, require continuous close coordination with the customer for practically every work step in the plant. The activities were carried out "in-situ", i.e. in the installed state, and at the same time as the customer's own dismantling activities. Previous decommissioning processes often required the establishment of suitable transport routes, for example, the enlargement of the equipment hatch - a cost-intensive procedure that has now been eliminated with Bilfinger's dismantling concept. After less than two years of construction site activity, the industrial services provider successfully completed the dismantling of the two steam generators, each of which is around 23 meters high and has a diameter of approximately 4 meters.
The special saws from the manufacturer HILTI that were deployed in Mülheim-Kärlich were adapted and further developed by Bilfinger for the special challenges of being used in a nuclear power plant. Decisive factors for the precise application of the powerful saws were various technical adaptations of the wire storage, the expansion of the cooling system and modification of the decontamination properties. In this way, the 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. These will be transported to an interim storage facility next year before they reach the final storage facility at Schacht Konrad.
With the successful completion of this dismantling project, Bilfinger has reinforced its position as a pioneer in the German dismantling industry. In the future, the company will benefit from the experience gained over the course of this project and from the close cooperation with the customer RWE. This expertise is already being incorporated into other joint dismantling activities at other locations.