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Integrated Mast & Crane Rig for Nuclear Decommissioning - Sellafield Nuclear Power Station

SCX Special Projects has created a combined mast and crane waste retrieval system for use in the decommissioning of part of Sellafield Nuclear Power Station.

Initially, the client requested a feasibility study to investigate whether a telescopic mast could be used to remove intermediate level waste (ILW) from a series of wet storage bays. The concept was theoretically justified and proven using prototypes. SCX Special Projects then developed the design over several methodical stages of trials, testing and refinement into the optimum solution, to meet not only the original requirements, but also the client’s evolving expectations as the project progressed.

The final solution comprises two near-identical tool deployment mast and crane rigs, each covering two of the wet bays. On each rig, the crane and mast work in tandem; the crane removes and subsequently replaces the bay covers whilst the mast and its tooling down-sizes and then extracts the waste from the bays, which is then removed from site in a sealed container.

Hydraulically driven telescopic mast

The telescopic mast is hydraulically driven via a multistage cylinder. The sections are automatically deployed and retracted during normal operation, but each stage can be individually controlled ensuring ease of decontamination via an integral internal and external wash-down facility.

A torque controlled chain hoist, on permanent standby in case of any failure in the hydraulic lifting system, tracks the mast’s movement to provide immediate recovery of the mast and cylinder in the unlikely event of a breakdown or power failure.

Crab unit fitted with a MotoSuiveur (MS) emergency safety brake

The 5 tonne true vertical lift crab unit is fitted with a MotoSuiveur (MS) emergency safety brake which tracks the operation of the hoist mechanism. In the event of a sudden load drop or overspeed condition the MS safely arrests the load within 30° of hoist barrel rotation, equivalent to just 21mm drop in load height.

Close up of integrated mast crane and rig

In the event of either a long or cross travel breakdown, recovery is provided by low-powered slow-speed recovery winches and a series of low-friction, hydraulically lowered jockey wheels which jack up the failed end carriage within the clearance of the seismic anti-uplift brackets.

Remote control system for crane with SCADA and CCTV

The remotely located control station utilises real-time SCADA displays to inform the operator of the live position of the mast and crane hook, via a series of laser and absolute encoder systems. CCTV provides visual confirmation of the system’s operation.

In addition to normal safety interlocks and operating boundaries, a totally independent Engineered Protection System monitors the overall system performance.

Brokk hydraulic manipulator on integrated mast and crane

The mast deploys a Brokk hydraulic manipulator which uses a range of tooling to down-size and extract ILW and sludge. The mast is gimbal mounted to prevent the Brokk exerting excessive loads on the building or supporting structure. SCX’s bespoke-designed 16-way hydraulic hose reeler provides flexible power delivery to the Brokk.

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SCX Special Projects Ltd
Roman Ridge Road,
Sheffield, S9 1GA
Tel: +44 (0)114 243 1142
Email: info@scx.co.uk
An SCX Company