Mammoet has developed a custom solution to replace steam generators at Framatome’s Flamanville FA1 Nuclear Power Plant, in Normandy, France.

Maintenance and engineering work inside a nuclear facility is particularly difficult as activities must comply with strict safety regulations, and buildings are often decades old, with little done during the construction process to remove larger elements. As such, Mammoet was approached by the French nuclear company Framatome, owned by Électricité de France (EDF), Mitsubishi Heavy Industries, and Assystem, five years ago, to develop an engineering solution.

Mammoet was asked to design a method to safely lift each steam generator from their cubicles, and rotate and manoeuvre the steam generators into a position so that they could be skidded out of the building for decommissioning. The operation would then be reversed for the installation of the new steam generators. The main challenge was taking these generators out safely in one piece. This was necessary because of possible contamination and also meant less downtime for the plant.

The operation

Each 1300 MW unit steam generator measured 25 metres long, 6.5 metres in diameter, and 520 metric tonnes per unit. A 3D computer-rendered model of the inside of the reactor building was used to develop a plan of action. A lifting trolley, installed on a polar crane, was used for lifting and tailing the steam generators. A supporting mast was needed to reinforce the centre of the polar crane, then a separate device was used for down-ending and tailing the steam generators. Finally, the saddles and skidding tracks were used to manoeuvre the generators in and out of the reactor building.

Olivier Vanesse, nuclear activities manager and Project Director from Mammoet, France, stated: “The facilities and infrastructures inside the reactor buildings are such that you cannot simply make a basic tailing operation. You need to be able to steer the steam generator, you need it to rotate. There are a number of steps that need to happen in order to move each of them through the main hatch. (…) you need to use a support in the middle of the polar crane to ensure that during the tailing process it has enough capacity – constraints and deflections-wise.”