May 2nd Heavyweights lift Risø's reactor plug

They have raised the kursk nuclear submarine from the bottom of the arctic ocean and erected an overturned 80-ton crane at the Lindø shipyard after the 1999 hurricane. Now Dutch Mammoet with its muscle cranes must pull up a giant metal plug from Risø's largest research reactor.

IIthese weeks Danish Decommissioning is planning a challenging operation, which will be the only one of its kind in Denmark. A 22 tonne shielding prop, sitting in the tank of Denmark's largest research reactor, will be lifted. This requires special cranes and a large safety contingent.

The plug - known in the trade as a top shield plug or TSP - seals the radioactive tank tightly, like the stopper in a thermos flask. It has to be lifted and removed so that Danish Decommissioning can cut open the reactor vessel itself from the inside. The moment the plug is lifted, a movable lid is rolled over the tank as a new shield, so that the powerful radiation is constantly sealed in.

Part of the challenge is the limited space. The reactor tank is cast into a square concrete tower that is 6 x 6 metres wide and 10.5 metres high. The tower stands in a high, cylindrical hall with only a few metres of working space facing the walls. Dutch heavy lifting company Mammoet are specialists in this kind of work and were self-selected to do the job for Danish Decommissioning.

Mammoet has repeatedly lifted and removed entire reactor tanks from nuclear power stations around Europe. In addition, the company is tasked with placing the new roof on the concrete sarcophagus that encapsulates the Chernobyl plant.