Babcock has completed a Local Sludge Treatment Plant (LSTP) to provide interim storage for sludge removed from the Sellafield, UK Pile Fuel Storage pond.

Local sludge treatment plant pump & valve bulge operating floor

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.

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.

Babcock 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.

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.

FilesReactor-by-reactor Fukushima Daiichi restoration progress summary as of 12 April, from JAIF
Elevation cutaway view of crane structure

Date: Tuesday, 17 April 2012
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