Shrink Wrapping the UK's Largest Nuclear Project: 11 Modules, 100 Nautical Miles, Zero Failures

Industrial Transport Covers · Nuclear

Key Facts

• Client: Costain / Interserve
• Project: Sellafield Evaporator D — UK's largest nuclear project
• Scope: Shrink wrap transport covers for 11 modules over 2 years
• Largest module: Module 920 — 525 tonnes, 27m × 7m × 12m
• Journey: Ellesmere Port to Sellafield beach via barge Terra Marique
• Result: 100% success — no sheeting failures, no water ingress

The Problem

Evaporator D at Sellafield is the largest nuclear project ever undertaken in the United Kingdom. The facility, built to treat highly active liquid radioactive waste so that it can be vitrified turned to glass and safely stored, was constructed under a £300 million contract awarded to Costain.

To solve the logistical problem of building on an active, space-constrained nuclear site, Costain and construction partner Interserve took an unprecedented approach: the entire facility would be pre-fabricated as eleven separate modules at a purpose-built five-acre factory at Ellesmere Port in Cheshire, then transported to Sellafield by sea. It was the first use of modular construction for a process plant anywhere on the Sellafield site.

The engineering challenge was formidable. The largest module Module 920 weighs 525 tonnes and stands 12 metres high, 27 metres long and 7 metres wide. Inside it alone are over 5,000 metres of high-integrity stainless steel pipework, 23 vessels, and precision fabrications built to nuclear quality standards.

The journey from Ellesmere Port to Sellafield covered 100 nautical miles of open sea aboard the specialist heavy-lift barge Terra Marique, followed by a beach landing and a road movement across a purpose-built bridge over the River Ehen.

Any salt water entering the modules during that journey into the stainless steel pipes, welds and precision fittings could trigger stress corrosion and compromise the long-term safe operation of the facility. The consequences of a water ingress event extended well beyond repair costs: programme delays on the UK's most significant nuclear construction project were simply not acceptable.

Whatever protection solution was chosen, it had to be guaranteed not approximate, not adequate under normal conditions, but certain.

The Solution

After months of evaluation, including on-site demonstrations of the industrial shrink wrap process, Costain and Interserve selected shrink wrap as their preferred transport protection.

The decision was not straightforward. Because the Evap D modules had no solid external cladding they were open structural frames carrying internal process equipment there was a concern that even a drum-tight heat-shrunk membrane could be pushed inward by high winds into the large voids behind, causing damage to the pipework and fittings inside.

The solution was a purpose-designed system never previously used in this application. A geotechnical HDPE mesh a product originally designed for underground soil stabilisation was draped around the full perimeter of each module and secured to the structural frame using woven strapping. This formed an external support structure just inside the shrink wrap layer.

Working from cherry pickers and elevated platforms, 12-metre-wide sheets of 300 micron shrink wrap were then hung over the mesh, heat-welded together at every joint, and heat-shrunk drum-tight.

The final element made the system genuinely robust. A small hole was made through the shrink wrap membrane every square metre across the entire surface, and a Velcro tie was passed through each hole and around the mesh behind. Each hole was then sealed with tape to restore the weatherproof barrier.

The result was a membrane that was simultaneously heat-shrunk tight and mechanically tied back to the support structure at one-metre intervals two independent retention systems acting together across every square metre of surface area.

All eleven modules were wrapped at the Ellesmere Port facility before road movement to the Manchester Ship Canal and loading onto the Terra Marique. The barge then navigated the 100 nautical miles to Sellafield, using four 360° water thrusters to position within a predetermined lay-down area marked by buoys, deploying ramps for a direct roll-on/roll-off offload across 80 metres of foreshore on to Sellafield beach.

The Result

All eleven modules were delivered successfully between 2011 and September 2013. Over a two-year programme, not a single sheet of shrink wrap failed and not a single instance of water ingress was recorded in any module.

The project stands as the most demanding transport protection assignment ever undertaken using industrial shrink wrap. The combination of marine exposure, open-frame module geometry, nuclear quality standards and zero-tolerance for failure produced a solution the mesh-backed, Velcro-tied membrane system that has since informed Rhino's approach to other high-consequence transport cover projects.

Evaporator D was subsequently completed and became operational at Sellafield. The shrink wrap covers were removed on arrival at site, with the film taken off for recycling.

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