Interserve, the international support services and construction group, has completed works on W8920 – the UK's largest nuclear evaporator module. In Interserve's four-year involvement in the project, the industrial team has built 11 modules for the Sellafield nuclear site.

Weighing over 520 tonnes and standing 27 metres tall, module W8920 is three times larger than any of the other 10 modules, all built by Interserve. Under the contract awarded by Costain, the modules have been fully fabricated in Interserve's off-site facility in Ellesmere Port; a dedicated facility spanning 230,000 square feet - the equivalent to three Wembley football pitches.

All 11 modules have been transported to site by road and sea – a first for the Sellafield site. Crossing over the M53 to reach the barge for sea transportation, W8920 is one of the heaviest loads to ever be delivered by road in the UK. Through months of logistical planning with contractors, stakeholders, local police and road crews, which included a scheduled closure of the M53, W8920 travelled on a self-propelled modular transporter (SPMT) to be delivered to the specialist barge moored at Manchester Ship Canal.


With a focus on environmental impact, Interserve used a specialist shrink-wrapping technique, which is waterproof, lighter and decreases the volume of environmentally non-friendly materials. This reduced transportation costs significantly and saving over 100 tonnes in final packaged weight - ensuring the load would not exceed the maximum capacity of the M53 road bridge.

Module W8920 is the culmination of four years of Interserve's specialist fabrication, welding and pipefitting expertise as Guy Bruce, Managing Director – Industrial at Interserve explained: "The last module has truly tested established engineering practices. Everything about it has been on a significant scale, from the complex design and construction of the bespoke stainless steel scaffolding, to the five and a half kilometres of pipework installed, to the 8,100 individual pipe butt, support and fabrication shop welds.

"This is the first time that the nuclear sector has chosen to pre-fabricate modules of this size and scale off-site, and most days we've had up to 15 nuclear-specialist welders and 20 fitters working on the module simultaneously; a combined total of more than 80,000 hours.

"Project scale hasn't been the only complexity however. The modules have had to comply with nuclear build level one standards, requiring the most stringent health and safety practices in a highly-controlled environment, quality of workmanship and strict traceability of materials and welds to be adhered to.

"Each weld was radiographed using x-ray and pressure tested to ensure complete integrity of the pipework and vessels contained within the module. Interserve ensured that we retained existing specialist skills from the local area, breaking the myth that these specialist skills do not exist in the UK."

(CD)