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

When faced with the task of retrieving ILW sludge and other items from Sellafield's wet storage bays, including the additional difficulty of restricted physical access, SCX Special Projects had to apply the best of its mechanical and electrical expertise.

Following the development of a prototype to test the concept of a mast-mounted manipulator to reach into the pits and extract the waste, SCX delivered two handling systems that demonstrate our innovation in solving the nuclear waste handling challenge.

The Challenge

Sellafield has a series of wet storage bays from which intermediate level waste (ILW) needs to be removed. The waste pits contain a variety of material from sludge to large items, the latter needing to go through a size reduction process before export.

Access to the pits is via a very restricted opening, so a mechanical means of entering the bay and reaching into its far corners was needed. A remote control handling solution was essential too, with safety and recovery systems to mitigate handling risks and mechanical failure.

The Solution

SCX Special Projects engineered, built and installed two waste retrieval systems, one for each storage bay. These were developed following an initial feasibility study on whether a telescopic mast could be used to reliably remove differently sized waste items from beneath the water.

A mast and crane work in tandem on the same gantry to deploy a range of tools into the wet pits. The crane opens and replaces the bay covers, while the tooling mast downsizes and extracts waste from the bays, which is then placed in a container, sealed and removed from site.

Load arrest and recovery

  • The 5-tonne true vertical lift crab unit is fitted with a MotoSuiveur load arrest device
  • In the event of a hoist failure, the MotoSuiveur safely arrests the load within 30° of hoist barrel rotation, equivalent to just 21mm hook drop
  • Long and cross travel recovery is via slow-speed winches, plus low-friction jockey wheels that help clear the crab’s integrated seismic anti-uplift brackets

 

Fine control from a safe distance

  • A remote SCADA control station gives a real-time display of the mast and crane hook position, via a series of laser and absolute encoder systems
  • CCTV provides visual confirmation of the system’s operation, while safety interlocks and operating boundaries keep all motions within safe limits
  • An independent Engineered Protection System monitors the overall system performance

 

Handling innovation

  • The telescopic mast is hydraulically driven via a multistage cylinder, with a chain hoist backup for recovery
  • The sections are automatically deployed and retracted during normal operation, but each stage can be individually controlled for ease of decontamination
  • A Brokk hydraulic manipulator uses a range of tooling to downsize and extract ILW and sludge, and is gimbal-mounted to the end of the mast

 

Let's talk more about bespoke nuclear waste handling

The challenge of decommissioning the UK's nuclear power plants is a significant one, spanning a multitude of disciplines. Mechanical handling of irradiated materials is a prime example. It requires high integrity mechanical and electrical systems that are safe, reliable and fit-for-purpose.

We bring decades of experience to help solve your handling challenges - talk to us today.
 

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SCX Special Projects Ltd
Roman Ridge Road,
Sheffield, S9 1GA
Tel: +44 (0)114 262 6199
Email: info@scx.co.uk