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Magnox Winfrith Dragon – Nuclear Polar Crane Refurbishment

The decommissioning of a reactor and its supporting systems requires a high-integrity lifting solution to safely remove debris as the reactor is slowly taken down. At the Winfrith Magnox power station, the original polar crane sat in a confined space above the ‘Dragon’ reactor. However, the crane was neither designed nor suited to the task of decommissioning. SCX Special Projects was called in to refurbish and upgrade the polar crane, and to provide Winfrith with safe, reliable nuclear lifting.

The Challenge

SCX Special Projects’ expertise was called upon to refurbish a 25-tonne polar crane over the Dragon reactor at Winfrith Nuclear Power Station. The refurbishment would enable the crane to become a vital piece of equipment for decommissioning the facility, including the reactor itself.

The main challenge for SCX was to replace old equipment with new, while navigating the extremely
limited space over the reactor, with no other crane to utilise.

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Winfrith Polar Crane Bespoke nuclear crane handling solution
Winfrith Polar Crane Bespoke nuclear crane handling solution

The Solution

SCX performed a full refurbishment of the crane, including: a structural analysis of the original polar crane bridge; engineering and installing a replacement 25-tonne SWL crab unit; adding an auxiliary 5-tonne hoist; replacing the polar travel drives; and upgrading the entire EC&I system.

The upgrades have given Winfrith a long-term nuclear lifting and handling solution capable of fulfilling its decommissioning plans safely, reliably and efficiently.

Technical Details

Replacing the crab
  • The replacement crab unit has two high-integrity hoists: a 25-tonne SWL main hoist for lifting larger loads, and a 5-tonne SWL auxiliary hoist to undertake routine handling duties
  • There was limited space above the reactor to refit the polar crane, so the bespoke crab is modular in design
  • The crab is lifted and manipulated into position piece-by-piece via a temporary A-frame and pulley system, then reconstructed on the crane’s bridge
Enhancing control
  • A combined power and control slip-ring replaced an umbilical design, improving flexibility, efficiency and safety
  • The new PLC controlled system is operated by either remote pendant or via a touch-screen HMI (human-machine interface)
  • Multiple encoders and sensors provide feedback on the crane’s position, the hoist height, and the current load, all displayed on the HMI
Ensuring safety
  • Secondary drive units are fitted onto the primary gearboxes to provide backup power should one drive fail
  • Dual calliper emergency disk brakes are mounted directly onto the rope drums of both the 5-tonne and 25-tonne hoists
  • Overspeed relays, overload relays, shaft relays and a collision protection system ensure that the crane stays
    within its predefined safe working limits

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