The Nuclear Decommissioning Authority

 

The world's two oldest operating Magnox power stations are continuing to safely generate electricity beyond their scheduled closure dates after a huge amount of innovative work and a dedicated team effort.

The revenue from Oldbury, in Gloucestershire, and Wylfa, on Anglesey, contributes a significant level of funding to assist with decommissioning. In the past financial year, 2009-2010, the plants provided enough energy for more than 1.5 million homes and earned well over £300 million in revenue.

The UK's 11 Magnox plants represent the first generation of nuclear power stations, with all but two now closed and at various stages along the road to decommissioning.

Oldbury was planned to close in December 2008 and Wylfa in March 2010, dates that were originally set to meet reprocessing milestones at Sellafield. Subsequent adjustments to the programme, which postponed the scheduled start of de-fuelling, brought an opportunity to revisit these dates and consider extending the life of the plants – providing it could be achieved safely and with the consent of the nuclear regulators and the Government.

Both have already been granted initial extensions, Oldbury to mid-2011 and an additional nine months for Wylfa to December 2010.

As both plants have already operated for around 40 years, extending generation further has necessitated demonstrating that issues relating to ageing equipment, limited fuel stocks – manufacture of Magnox fuel has ceased - and safety have been comprehensively addressed.

At Oldbury, one of the main aspects was the condition of the graphite bricks that house the fuel elements and moderate the nuclear reaction. Over time, the graphite's density changes and has the potential to affect operations. An extensive programme of physics research, sampling, inspection and assessment of the graphite core has enabled the development of a strong safety case.

Meanwhile, the team has also demonstrated that standard refuelling practices can be modified to improve generating efficiency, by shuffling fuel within the reactor to use remaining fuel most efficiently, while partially irradiated elements can be retained to avoid the need for fresh fuel. 

At Wylfa, extensive programmes of internal reactor inspections and repair work have been essential, along with detailed reactor physics studies to ensure the optimum use of remaining fuel.

The NDA has asked Magnox North to prepare a safety case for extended generation at Wylfa until 2012. A decision is expected from the nuclear regulators by the end of the year.

• More information on Oldbury
• More information on Wylfa
• More information on Magnox North Ltd