Mammoet Moves Four 300t Steam Generators in Germany

Mammoet completed the transport and load-out of four 300-tonne steam generators from the decommissioned Unterweser Nuclear Power Plant in Germany, using SPMTs and a tightly controlled two-hour tidal lifting window.

The operation formed the second phase of a project that began in 2024, when Mammoet engineered the removal of the four steam generators from the reactor building in one piece. The latest scope, carried out on behalf of Orano NCS, moved the components from the power plant to an overseas vessel for shipment to Cyclife’s nuclear waste treatment facility in Sweden.

Each steam generator measured approximately 20 metres long and 4.5 metres in diameter.

An original plan to use the power plant quay was abandoned because strong tides would have required dredging. Instead, the project team selected a former ferry ramp at Kleinensiel, around five kilometres from the plant.

Each generator travelled overnight on two 12-axle-line SPMT units. Road permits restricted movements to between 22:00 and 06:00, while the load-out itself was governed by the River Weser’s tidal range of up to three metres.

“The tide had to be high enough so that the sheerleg crane could get close enough to the ramp, but we also had to be mindful of the SPMTs not getting submerged in water,” said Tom Schladitz, Project Manager at Mammoet.

Using forecast water-level data, Mammoet identified an optimum lifting window of just two hours, between 09:00 and 11:00.

The ferry ramp presented another challenge, with a 4.2-degree downward gradient that exceeded the SPMTs’ ability to level themselves even at full jack stroke. Mammoet therefore constructed a temporary ramp over the existing structure, allowing the transporters to remain horizontal and preventing a shift in the steam generators’ centre of gravity during lifting.

At the ramp, a floating sheerleg crane lifted each generator from the SPMTs and transferred it to the nearby overseas vessel.

Two SPMT sets were used in rotation, with a temporary parking area near the ferry ramp enabling the next generator to be prepared while the previous unit was being loaded out.

All four transports were completed over four consecutive nights. Missing either the overnight transport slot or the two-hour lifting window would have added an additional day to the programme and increased vessel and crane charter costs.

“We planned this transport for over a year, so it was incredible to see all that preparation pay off and us deliver another successful project for our client,” said Tom Schladitz, Project Manager at Mammoet.