Accelerating the Decommissioning of the Sellafield Pile Fuel Storage Pond Using Innovative Remote Tooling Developed with the Supply Chain - 16437

The Pile Fuel Storage Pond (PFSP) at Sellafield and adjoining de-canning building provided the storage, cooling and de-canning facility for used fuel and isotopes from the two Windscale reactors and later some Magnox fuel from the Calder Hall reactors. Operations ceased in the 1970's and the facilities are now undergoing a programme of accelerated decommissioning. The pond is a sub-divided outdoor storage pond containing skips of irradiated fuel and miscellaneous waste items and the building contains a series of sub-ponds, known as bays, connected underwater to the main pond. The radiation environment and access limitations necessitate the use of remote technology for the decommissioning programme. This paper describes the philosophy and approach and the technology and equipment adopted for the removal and export of key plant equipment and waste items from within the PFSP. In order to progress the project cost effectively and speedily, the Sellafield project team looked for partners in the supply chain with the required experience, expertise and facilities to supply and test 'commercial off-the-shelf' (COTS) or modified proprietary equipment. This COTS approach minimised the need for multiple, expensive and lengthy design and manufacturing tasks associated with bespoke equipment. Sellafield partnered with specialist remote handling contractor, James Fisher Nuclear, and the respective project teams worked closely together at every stage of the project from qualifying requirements, identifying potential solutions, through to development, testing, training and final deployment. Optioneering of potential solutions involved early 'proof of principle' trials in JFN rig hall facilities, utilising existing equipment and plant mock-ups, along with other equipment manufactured in-house. Together the project teams selected the best solution to take forward, adopting a practical and trials based approach, which allowed rapid and cost effective modification of the solution throughout the project with minimal impact on the programme. When the final solution was validated, plant operators then gained familiarity and training on the equipment so they could execute the work efficiently on plant and so minimise their dose uptake. The removal of a Large De-canner is described in detail. This was a significant obstruction to the emptying, modification and re-use of the bay and a key milestone in the clean-up of the PFSP. The de-canners are large and heavy pieces of equipment which weigh 6.5 t each and approximately 6.5 m long. Their removal was further complicated by limited equipment and man access, radiological contamination from de-canning fuel, challenging material properties, unknown equipment condition and complex lifting requirements. Sellafield Ltd and JFN project teams worked closely together to rapidly develop, trial and deploy a succession of adapted 'commercial off-the-shelf' (COTS) tools whilst addressing emerging challenges and completing the overall task on time and budget. The Sellafield and JFN project and design teams provided an underwater: wheel stop removal tool; towing trolley; grinder on a carbon fibre pole, chute cutting 600 mm circular saw and hydraulic 6 t winch. The suite of tools will be reused on the remaining de-canners in the PFSP and First Generation Magnox Fuel Storage Pond (FGMSP) giving cost and programme savings. Each of the tools can also be used, and some have already been, for other tasks in the bay retrievals such as the size reduction of support frames, large steel sections and chemical de-canner preparatory works. The 'learning from experience' acquired during the project was shared by the Sellafield project with other decommissioning projects across the site. (authors)