An important piece of new kit has been installed in the Pile Fuel Storage Pond (PFSP) known as the Sludge Retrieval Hood (SRH). The SRH, together with a Remotely Operated Vehicle, sucks up sludge from pond floor.
The PFSP was the very first nuclear fuel storage pond at Sellafield built in 1948 and sludge in the form of corrosion products and wind blown material has been accumulating in this open air pond ever since.
Decommissioning of the PFSP has been hampered by the layer of sludge on the pond floor and within the metal skips containing both fuel and miscellaneous wastes. The SRH, together with the Skip Tipper, Skip Washer and Sludge Corral, provides the pond with full capability for sludge to be retrieved and placed into modern containment, prior to it being processed through the Local Sludge Treatment Plant.
“It is quite exciting to see the plant make the transition into full blown retrieval operations. Getting the plant to this stage has however been a series of challenges,” said Head of Programme Acceleration, Steve Cottam.
“Equipment was initially designed for the legacy pond based on existing drawings and plant records, but we quite often discovered that the conditions were not as expected, and sometimes had to make last minute modifications to equipment. Even now we still find unexpected things!”
Sludge retrieval is carried out in two main ways depending upon whether the skips are empty or contain fuel or radioactive waste. Firstly, the skips are processed through the Skip Tip and Skip Wash stations, which removes bulk sludge from inside the open topped skips. The empty skips are then removed via the Blindwash and East Washdown areas, enabling them to be taken out of the pond, wrapped and disposed of. Whereas skips containing inventory are moved to a cleared area of the pond floor, to await retrieval at a later date.
By moving skips round the pond, the team will be able to work their way down the full length of the pond floor removing sludge – a project which is expected to take five years to complete.
Sludge removed from both the skips and pond floor is transferred into the Sludge Corral, where it will be stored pending treatment through the Local Sludge Treatment Plant, currently in the inactive commissioning phase.