Calder Hall applies for decommissioning

The world's first commercial nuclear power station, Calder Hall on the Sellafield site, has applied to the Nuclear Installations Inspectorate for consent to be decommissioned. Opened in 1956, the plant ceased generating electricity in March 2003.

The decommissioning project will have three main phases, over a considerable period of time. First, the main buildings of the complex will be removed, apart from the reactor buildings themselves. These will be modifed to remove ancilliary equipment and re-clad. This phase is expected to take about ten years.

The reactor buildings, including the reactors themselves, their concrete biological shields and the main gas ducts, will then be left, probably for around a century, for the radioactivity inside the reactors to subside to safe levels. The site will continue to be managed and maintained during this period. Only at this point will the reactors be dismantled - another ten-year project.

The initial phase, known as Care and Maintenance Preparations, involves the demolition of the cooling towers, turbine halls, workshops, stores and radioactive workshops. Building debris produced during the project will be used to fill the holes left by removal of the buildings; other non-radioactive waste, such as glass, scrap metal and asbestos, will be recycled if possible, or sent to landfill or specialist waste disposal.

Of the radioactive waste, the small amount of intermediate-level material generated will be handled on-site at Sellafield, and the low-level waste sent to the Drigg disposal facility. The plant's boilers will then be laid down close to the reactor building, and all the remaining structures modified to ensure that they are secure and weatherproof.

This process is designed to ensure that minimal human intervention is needed during the 100-year Care and Maintenance Programme on the reactor buildings, which contain four Magnox reactors, each consisting of a graphite core inside a cylindrical steel pressure vessel contained within a thick concrete biological shield. The only active work expected to be necessary during this period is the replacement of exterior cladding.

The British Nuclear Group, which carries out nuclear clean-up in the UK, has prepared a 30-page non-technical environmental summary of the environmental impact of the decommissioning, including all three phases.

This is now the subject of a three-month public consultation period. If permission for the project is granted, work will begin on the non-nuclear parts of the site in December, with the removal of fuel expected to begin in 2007.