Nuclear power stations under decommissioning

Chapelcross

Construction of this 200 MW four-reactor Magnox station, the first com­mercial station in Scotland, started in 1955 and it was commissioned in 1959. It is situated near Annan in Dumfries and Galloway (Fig 17.1). It was shut down in 2004 and operated until 2005 by British Nuclear Fuels Ltd. It was then taken into the ownership of the NDA and is currently undergoing decommissioning on contract by Magnox, a wholly owned company of EnergySolutions Inc. (Magnox, 2012a).

Defuelling and preparation for care and maintenance is underway and is estimated to be complete by 2017. Defuelling is the major priority which started in 2008 and is planned to be complete in 2013. This is a key date because the fuel from Chapelcross is required to be at Sellafield for reproc­essing through the Magnox reprocessing plant before that facility is closed and decommissioned.

Owing to its links with historical operations at Sellafield, Chapelcross has a wide range of operational ILW consisting of sludges, inorganic ion exchange resins, ceramic pellets, tritiated oils, desiccants and miscellaneous activated components. This waste is stored in ponds and vaults which were not originally designed or constructed with decommissioning in mind.

Magnox has developed strategies for the management of the accumu­lated operational ILW streams that are to be dealt with during preparation for care and maintenance (Magnox, 2011). The strategies for those ILW streams that will only be dealt with at final site clearance are specifically left undefined at present.

The strategy for the majority of ILW waste streams is to retrieve the ILW, condition it and then package it in high integrity containers that are designed to provide the required shielding. They can be stored in conventionally constructed unshielded buildings. There is some ILW that is associated with past arrangements with Sellafield and this will be returned to Sellafield for treatment. The target date for achieving retrieval and storage of ILW that is not destined to be dealt with at final site clearance is 2016.

Chapelcross has also made the first shipments of metal LLW to the LLWR recycling routes. Decommissioning strategy is to put the station into a long-term care and maintenance regime in 2018 to allow radioactive decay to levels where in the future the final decommissioning and demolition can be undertaken by more conventional methods with less requirement for radiological protection and remote handling methods. This period is planned to continue to around 2090 after which the final decommissioning and demolition would take place up to 2095. LLLE is discharged to sea through a 6 km pipeline to the Solway Firth.

The final packaged volume of HAW is estimated to be around 5,000 m3 and will be stored until a final end-point is identified. Around 75% of this HAW will be ILW graphite (NDA, 2012). Final site clearance will create around a further 30,000 m3 of packaged LLW for disposal.

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