23 May Mammoet has lifted multi-ton reactor plug for DD

Success: The massive metal plug that sealed Denmark's largest research reactor DR3 has been successfully removed and replaced with a lid. Due to intense radiation from the reactor tank, this historic operation has been meticulously planned over recent years. DD commends the collaboration with Mammoet and Bladt Industries.

TThe plug – technically referred to as the top shield plug (TSP) – provided a hermetic seal for the radioactive tank, akin to a thermos stopper. Weighing 22 tons, its underside exhibits significant radioactivity following over 40 years of reactor operation. Consequently, it was imperative to lift and shield the plug in a single, continuous motion. The instant the plug was raised, a movable lid was deployed over the tank to provide new shielding, thereby ensuring the continuous containment of the intense radiation.

Confined Space
Part of the challenge was the confined space. The reactor tank is encased within a square concrete tower, measuring 6 x 6 meters in width and 10.5 meters in height. The tower is situated in a tall, cylindrical hall with only a few meters of working space towards the walls. Cranes and lifting equipment therefore had to be transported in component parts and assembled on site. The Dutch heavy-lift company Mammoet has successfully completed this historic task for Danish Decommissioning. Mammoet has on several occasions lifted and removed entire reactor tanks from nuclear power plants across Europe. Furthermore, the company is tasked with installing the new roof on the concrete sarcophagus encapsulating the Chernobyl plant. They have also undertaken specialized operations such as salvaging the nuclear submarine Kursk from the Arctic seabed.

Specialized Equipment
Bladt Industries in Aalborg has custom-fabricated the movable lid and the shielding containers into which the reactor plug has been lowered. For safety, the shielding consists of two containers – a cylindrical one within a square one – each of which would have provided sufficient shielding independently.

“We have experienced exceptionally good collaboration with Bladt Industries, who delivered precisely what we required, and with Mammoet, who operate with great professionalism, speed, and thoroughness. There were numerous safety-critical details associated with this lift, and I am truly satisfied with the performance of both our own employees and Mammoet,” states Project Manager Per Holtzmann Søndergaard from Danish Decommissioning.

Robotic Cutting
Now that the reactor plug has been removed and securely shielded, Danish Decommissioning will commence cutting the reactor tank itself from the inside. This will be accomplished using a robotic arm through hatches in the new lid.