Hunterston Nuclear Power Station - Wet ILW sludge retrieval systems

SCX Special Projects designed and installed a complete handling solution for the removal of sludge from a series of 4m deep sludge bays at Hunterston Nuclear Power Station in Scotland.

During the operating life and initial decommissioning of Hunterston A, wet (mobile) intermediate level waste (ILW) accumulated and must now be retrieved, processed and immobilised, in order to complete the decommissioning. The sludge needs to be pumped through to a process canyon where it is contained within ILW handling 3m3 Nirex drums, which must then be removed from site.

SCX Special Projects provided a series of bespoke equipment to create a complete handling solution for the entire process.

Bespoke sludge retrieval rig for Hunterston Nuclear Power Station

SCX Special Projects’ bespoke sludge retrieval rig lowers the sludge removal pump via a chain fed from a 1.25 tonne chain hoist. Capable of then slewing through 180° to access the full interior of the bays, the system is mounted on a carriage which traverses the width of the bay on rails.

Bespoke lifting frame for sludge retrieval crane

Once the sludge is removed, a bespoke lifting frame with a 3.2 tonne hoist then lifts the entire arm and carriage system out of the bay where it is washed down by a spray ring and then traverses across to the next bay to continue the process. A tailor-made storage frame houses the rig when not in use.

Semi-automatic, 10-tonne waste handling crane

Meanwhile, SCX Special Projects’ semi-automatic 10 tonne waste handling crane brings the empty 3m3 Nirex drums into the process canyon and sets them down into pre-determined start positions with a repeatability of ±5mm. The drums travel the length of the canyon on a conveyor as they are filled and sealed with the pumped out waste. The crane then removes them from the process canyon and deposits them into a cross-site transport (XST) vehicle. The entire operation is overseen from a remote control room complete with CCTV.

Unique four pole twist-lock grapple for sludge retrieval

The specially designed lifting grapple, created by SCX Special Projects for the handing of both 3m3 Nirex ILW drums and boxes, incorporates a unique four pole twist-lock grapple that is controlled and monitored by a series of limit and proximity switches. A main ‘floating’ actuator controls the twist locks, but in the event of a failure, a secondary recovery actuator overrides the first, ensuring the load can be appropriately set down before the system is retrieved from the containment area for maintenance.

Rendering of SCX Special Projects' wet ILW sludge retrieval crane

The crane is a modular design, developed by SCX Special Projects for use in the handling of nuclear ILW packages in both process plant applications and long-term storage solutions throughout the nuclear decommissioning arena. Absolute laser measurement provides a positional resolution of ±1mm, and the crane incorporates a recovery winch system so it can be rescued from the containment area in the event of long travel failure.

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SCX Special Projects Ltd

Roman Ridge Road, Sheffield, S9 1GA, United Kingdom

t:  +44 (0)114 262 6199