Defuelling starts at Sizewell

17 August 2009

The first flask of used fuel has been dispatched by rail from the Sizewell A nuclear power plant in Suffolk, UK, to be reprocessed at the Sellafield plant in Cumbria. The two-unit plant was permanently shut down on 31 December 2006.


Sizewell A (Magnox South)
Sizewell A (Image: NDA)
The removal of fuel from Sizewell A was expected to start shortly after the reactor shut down and had been expected to be completed this month. However, "challenges presented at the Sellafield reprocessing plant have resulted in fewer flasks being available. Generating sites are given priority which is why Sizewell's defuelling has been delayed."


Owners of Sizewell A the Nuclear Decommissioning Authority (NDA) said that since the plant's shutdown several small-scale decommissioning projects have been completed, including the removal of pipebridges, which previously connected the boilers to the turbines, and also the removal of redundant pond equipment.


According to the NDA, defuelling "is the start of a key phase in the site's decommissioning plan and its eventual completion, planned for 2012, will represent a huge milestone for the site. The flask dispatch program will continue for the next three years until all the fuel, which is currently stored safely in Sizewell's twin reactors, has been shipped to Sellafield for processing."


Paul Wilkinson, director of the Sizewell A site commented: "We are very pleased to have started defuelling. Our fuel accounts for around 99% of the total radioactivity at Sizewell A so this is a big step towards removing the site's most significant hazard."


During its operational lifetime, over 3000 fuel flasks have been sent by rail to Sellafield from Sizewell A. The NDA said that it will take some 310 flasks to clear the inventory of fuel still on the site. The purpose-built flasks are heavily shielded, being constructed from forged steel more than 30 centimetres thick. Each flask weighs more than 50 tonnes and holds up to 2.5 tonnes of fuel.


The Sizewell A plant houses two 210 MWe (net) Magnox gas-cooled reactors. Construction of the plant started in 1961, with Sizewell A1 starting commercial operation in March 1966 and A2 starting six months later. Both units shut down at the end of 2006 having generated a combined 105 TWh of electricity over their lifetimes.


Once defuelling has been completed around 2012, the plant will be prepared for being placed in 'care and maintenance' status, where the reactor buildings will be left for some 85 years to allow radiation levels to drop significantly before eventual dismantling and decontamination activities occur. Final site clearance of the plant will be completed by March 2110.


Sizewell A is adjacent to the Sizewell B plant, which comprises an 1188 MWe pressurised water reactor (PWR) that began operating in February 1995 and is due to shut down around 2035. The Sizewell site is one of two sites favoured by Electricité de France (EdF) for new nuclear power plants in the UK, the other being Hinkley Point in Somerset.