Dounreay Site Restoration Ltd

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The retrieval plant

One of the biggest projects in the Dounreay clean-up is the retrieval from the shaft and silo of historic wastes.

These wastes need to be brought to the surface, segregated, characterised and conditioned in a form that makes them safe for storage.

Following successful completion of the first phase of shaft decommissioning - its hydraulic isolation - work started on the ground enabling works for construction of the waste retrieval facilities, known as D3200.

Artist's impression of the retrieval plant (in the foreground)

Concept designs have been developed for the waste retrieval, treatment and storage facilities.

A key feature in the project team's approach to this has been their intention to use equipment and techniques already in use by other industries, such as adopting the methods of the water treatment and mining industries to treat the solid wastes.

Separate headworks will be needed above each facility and a combination of industrial grabs and robotic mechanisms lowered into the shaft and silo to recover the waste.

Water levels in each facility will be lowered progressively as more of the waste is recovered.

At the surface, the retrieved waste will be processed inside a series of cells.

The process line will include remotely-operated equipment for shredding and screening the debris, cutting large items and characterising its composition and radioactivity.

Once sorted, the solids will be compacted and liquids thickened. The waste will be mixed with cement in 500-litre drums, enabling it to be stored safely as intermediate-level waste.

All of this work will be carried out by remote control from behind thick shielding to protect workers from the hazards.

In addition to the waste in the shaft and silo, D3200 will also condition some other wastes from the site. These are:

* “contact handleable” intermediate-level waste currently held in above-ground drum stores

* graphite

* other wastes that cannot be processed in a proposed new intermediate-level waste treatment plant

In March 2010, DSRL announced a delay to this project until the conclusion of the NDA competition for the site. Click here to read the announcement.