As in all nuclear projects, safety was the top priority for the construction of a new evaporator unit at the Sellafield nuclear reprocessing site. To accelerate the schedule, civil engineer Costain had developed a modular construction plan. Eleven modules had to be transported to the site before being lifted and installed inside the unit. The safety of the procedure had to be absolutely beyond doubt. So Mammoet killed two birds with one stone by devising a tailor-made four-way gantry system that would deliver precision and safety while saving two months of construction time.
NUCLEAR SAFETY REQUIREMENTS INSPIRE AN OPTIMIZED SCHEDULE.
The gantry system would lift each of the modules to the correct height, from which they would be skidded into the new unit and installed. However, the modules needed to be installed in 11 different locations in the unit. This meant that the entire gantry system had to be moved alongside the unit prior to each installation. Normally, a gantry is jacked-up and down when it needs to be repositioned. But this would be time-consuming if it had to be done 11 times. Therefore, Mammoet came up with the idea of designing and installing the system on permanent skids. That way, the gantry could be skidded without jacking-up the entire system every time it needed to be repositioned. This solution greatly increased the level of efficiency, and saved two months of time during the whole project.
The modules – ranging between 50 and 500 tons – were built at Ellesmere Port near Liverpool. After completion, they were transported to the quay on Mammoet SPMTs. There, they were positioned on a specially-designed barge that could land on the beach near the site as there was no dock facility available. Via an installed ramp and temporary road over the beach, the modules were driven off to the storage area. There they were checked, and then transported to the site for installation. The gantry ¬– 34 meters high, 38 meters wide, and 18 meters long – lifted the modules from the SPMTs to the right level. From there, they were skidded into the evaporator unit for installation.
The last module was lifted and installed in 2013, and the new unit is expected to be operational in 2016.