Shaft & Silo
The shaft and silo are historic higher activity waste stores that are no longer in use.
The shaft is 65 metres deep and 4.6 metres in diameter. The silo is a concrete box set into the ground, with a capacity to store 720m³ of unconditioned higher activity waste.
The shaft and silo decommissioning programme comprises the design, build, operations and eventual removal of limited life plant and facilities necessary to retrieve, treat and package the waste from within the shaft and silo.
The first phase of decommissioning the shaft – hydraulic isolation – was completed in 2006 and was recognised by a number of industry awards.
Based on the current plan, construction of the new facilities will begin in 2020 and waste retrieval operations in 2024.
‘Headworks’ facilities will be constructed over the shaft and silo containing remote handling equipment to retrieve the waste.
Waste from the shaft will be retrieved using an industrial overhead travelling crane with a selection of grabs and buckets. This crane will be assisted by a remotely operated platform using manipulators with cutting tools.
The waste treatment area will be located at the shaft. Waste from the silo will be transferred in a shielded container to the waste treatment area for further processing.
In the waste treatment area, waste will be size reduced by an industrial shredder. Waste unsuitable for shredding will be size reduced by remotely operated vehicles.
The waste will go through a water separation process using a vibrating screen and settling tank, to separate the waste into three streams: solid, sludge and liquid effluent.
- Solid waste will be loaded directly into a 200 litre drum
- Sludge waste will be solidified by adding cement powder inside a drum
- Liquid effluent will be filtered and transferred to a new effluent treatment plant
The waste drums will be characterised and compacted to reduce the volume of waste, before being stacked inside a stainless steel container ready for final storage on site.