The Nuclear Decommissioning Authority

The world's first commercial nuclear power station, Calder Hall, has started to remove the spent fuel from its reactors in a programme which will take up to six years.

Calder Hall was formally opened at the Sellafield site by the Queen in 1956, watched by scientists and statesmen from 40 different countries as well as an audience of several thousand people.

Hailed as a ground-breaking development for the country, the four reactors generated electricity until 2003 and paved the way for the 10 Magnox plants that were subsequently built in the following decades.

Its initial output of 168MW eventually rose to 220MW following technical modifications, enough to power around 100,000 typical households. As the Magnox design improved, more modern stations became more efficient, with the most up to date, Wylfa, generating more than 1,000MW and able to provide power for 40% of Wales.

The Calder Hall defuelling programme builds on the successful demolition of the cooling towers in 2007 and the removal, over five years, of 2,300 tonnes of asbestos. The fuel elements will be removed from the reactors and transferred to reprocessing facilities on the Sellafield site. When the programme is complete, the reactors and associated infrastructure will be progressively decommissioned to enable the site to enter into a 'care and maintenance' phase.

Mark Steele, the NDA's Interim Head of Programme for Sellafield, said:

"Calder Hall is a name synonymous with nuclear power and its contribution as a pioneer of the industry cannot be overstated.

"The defuelling of Calder Hall is a key part of our overall programme of safely decommissioning the first fleet of UK nuclear power stations. This current stage builds on the successful cooling tower demolition and asbestos strip. I congratulate the team on safely and successfully reaching this milestone and look forward to continued progress."

Further north, meanwhile, Chapelcross in Scotland has now passed the halfway stage in removing its 38,075 fuel elements. The first flask containing spent fuel was sent to Sellafield for reprocessing in April 2009, after the regulators gave formal permission for the work to start, with an expected completion date of March 2013.

More than 19,000 fuel elements have now been removed from the four reactors in 128 flasks, each containing an average of 144 elements. Approximately 250 shipments will be needed to complete the defuelling.

Co-ordination keeps deliveries on track

Defuelling is a complex, lengthy process that takes place over a period of years and represents a major element in addressing the NDA's highest hazards: spent fuel contains 99% of a site's radioactive inventory.

Detailed co-ordination of all activities is required to ensure a smooth sequence of transports and efficient operation of the reprocessing facilities at Sellafield. Known as the Magnox Operating Programme, or MOP, timeframes and targets have been established for each site, with regular reviews to take account of significant changes.

Much of the infrastructure and plant at Sellafield date back many years and breakdowns do impact on performance. To address this, an ambitious and comprehensive improvement programme has been developed.

A stronger partnership between all participating sites has improved progress dramatically over the last 18 months with some significant challenges faced and overcome including significant issues with the availability of fuel transport flasks and the impact of unplanned stoppages in reprocessing.

The MOP, now at version 8, is currently being updated to reflect a need to recognise variations in defuelling and reprocessing performance - such as dealing with potential plant or equipment failure - that could affect timescales. MOP9 is due to be finalised later this year.