Pile fuel cladding silo retrievals at Sellafield

KUKA Systems UK has designed and developed a robotic system to help remove radioactive waste from the six-story Pile Fuel Cladding Silo at the Sellafield nuclear site in Cumbria.

It follows a series of studies and reports that were conducted between KUKA, Cavendish Nuclear and Sellafield. Together, they explore the feasibility of several system design variations, supported by simulation models, to deal with the removal of significant radioactive waste and transferring it into containers for safe interim storage.

These digital twins mirrored all elements of the robot equipment and periphery, and the physical assets within the waste container handling facility. Optioning and risk reduction exercises were conducted on the various concepts, until a workable solution was identified.

The robot system has the capability to remove bolts from the lid of the waste container at Sellafield and place them into a bolt storage rack. The waste container is then moved to a separate area where the lid is removed, and the container is filled with waste.

When the waste container is full, the lid is placed back in position and is moved back into the robot cell. The robot then deploys a felt swab, whereby the lid seal area of the container is swabbed. The swab is then analysed to determine that no contamination is present around the lid seal. If the waste container is clean, the bolts are then replaced by the robot and each bolt tightened to a pre-determined torque. The container is then exported from the WCHF.

The automated bolting and swabbing processes are KUKA’s standard process, which can be applied to future projects within the nuclear and other industry sectors.

The robot cell comprises:

• A KUKA KR150 six axis industrial robot mounted on a fabricated support pedestal - the robot is fitted with an automatic tool changing device that enables the nut running tool, used for bolt removal and the swab gripping tool to be deployed.
• A tool storage rack, allowing safe storage of the robot tooling when not in use.
• A bolt storage rack, allowing storage of the waste container lid bolts when they have been removed.
• Swab cassette storage stand, which provides storage of one hundred felt swabs, ready for collection by the robot, when required.
• A programmable logic control system provides complete control of the robot cell and safe operation by way of safety interlocks.

The cell was designed, built and tested at KUKA Systems UK.  Plant operating staff were trained on the use of the equipment once pass-off trials were completed. Equipment was then dismantled, delivered and installed in its intended location at the Sellafield site. Active waste retrieval began in late 2019, known as the Early Retrievals Project. Next stage ‘Full Retrievals’ will soon commence.

The pile fuel cladding silo retrievals project was an exciting concept for KUKA Systems UK.  It involved many hours of innovative development, detailed design and in-depth investigation and evaluation. All in all, it further strengthens KUKA’s presence within the nuclear sector.

For more information on KUKA Systems UK.

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