Babcock’s role in the Pile Fuel Storage Pond (PFSP) project is to assist in delivering the plant and systems required to safely retrieve and export the intermediate level waste that has accumulated as sludge. This latest milestone involves the completion of a Local Sludge Treatment Plant (LSTP) which will provide interim storage for sludge removed from the pond. Babcock has managed the design, build and commissioning of the LSTP as well as the nuclear safety case for the plant’s construction and operation.
The plant was handed over to Sellafield on 30 March 2012, ten months ahead of schedule. The early completion of the project is in line with Sellafield’s commitment to accelerate the decommissioning of its high hazard projects.
Babcock was awarded a contract in 2005 to design, supply, manufacture, construct, install and commission a suite of plant and equipment as part of Sellafield’s PFSP programme. The PFSP is the world’s largest open-air fuel pond and Sellafield’s oldest, having begun operations in 1952. It was originally built for cooling irradiated fuel from the Windscale Piles reactors before reprocessing, and was subsequently modified to allow it to receive spent fuel from the Magnox reactors at Calder Hall. An adjoining decanning plant was used for removing the fins and other metallic components surround the fuel elements. When decanning stopped in the early 1960s the pond continued to be used as storage for fuel and operational waste. Being open to the environment the pond has seen a gradual accumulation of sludge and debris and dealing with this high priority waste stream has been the focus of the work being delivered.
In other parts of the workstream Babcock has designed, built and delivered a Local Effluent Treatment Plant (LETP) to aid clean-up of the pond water. The company has also delivered a suite of bespoke plant and equipment to enable the retrieval of the sludges from the pond floor, including equipment such as a skip tip machine, skip wash machine, remotely operated vehicles, and an in-pond corral to accumulate the sludges to be pumped to the LSTP for processing and storage.
The LSTP is the latest project to be completed. This has involved the construction of a new plant to the north of the pond, comprising an overbuilding containing four secondary containment cells. These contain a sludge thickening and sentencing module and three Buffer Storage Tanks (BSTs) together with their associated pump modules, sampling systems and control systems. Sludge is pumped in batches from the pond to the thickener vessel where it is allowed to settle. The thickened sludge will then be transferred to one of the BSTs and the supernate from the settled sludge returned to the pond.
Where possible Babcock designed the LSTP plant to be manufactured in modules with final assembly on-site at Sellafield – an approach that has reduced construction time and will also reduce eventual decommissioning costs.
In relation to PFSP portfolio Babcock Senior Project Manager Paul Smith commented: “This has been a suite of challenging projects, and we are delighted to have successfully completed, commissioned and handed over the LSTP plant, as the latest phase in our work with Sellafield on the PFSP project. A lot of hard work has gone in from Babcock and Sellafield both from a technical perspective and also pioneering new methods of working with the client, such as the integrated site delivery team, to achieve this early completion date. We have successfully delivered all eight customer milestones for this project ahead of schedule, and we are now looking to build on the successes to date as we continue to work with Sellafield on the PFSP programme under the Design Services Alliance (DSA)”.
Key to the forward overall PFSP decommissioning programme is the design and construction of an export facility for the sludges, which will include solutions for removal of the accumulated sludges from the LSTP, the residual fuels and the bulk solid intermediate level waste. These will all be developed jointly with Babcock and Sellafield Limited as part of the DSA.
Derek Carlisle, Sellafield Limited Head of Projects for the PFSP Programme commented: “The successful completion of the LSTP project so far ahead of the contract schedule is entirely due to the professionalism and dedication to the project demonstrated by the combined Babcock / Sellafield Limited team. Design and construction of a large facility so close to an ageing nuclear plant will always be challenging. Success is only achieved when all parties commit fully to ‘shared success’ delivery models. This way of working has been embraced by the project resulting in a project being delivered ahead of time, within budget, and with an excellent safety record. We look forward to working with Babcock on future phases of the PFSP programme.”