27 Jun 14

Update on Dungeness B graphite bricks

Every three years we thoroughly inspect the graphite core as part of our statutory outage.

At Dungeness B, we have used the information from a continuing programme of monitoring, inspection and physical sampling of the graphite core to assess the state of the core. This knowledge feeds in to modelling and analysis which give us the knowledge to allow us to safely increase the limit of weight loss within the core from 6.2% to 8%.

As time goes on we will continue to collect data, build this into our models and calculations and ensure our safety margins are robust and appropriate.

EDF Energy remains focused on achieving a ten-year life extension for Dungeness B which we hope to confirm by the end of the year. To ensure that safety margins continue to be sufficient, we have developed a programme of modifications which will feed in to the plant lifetime extension proposals and enable safe operation to 2028.

Martin Pearson, station director at Dungeness B said: “The increase in weight loss limits has been based on an extensive programme of modelling and sampling. The limits are set at conservative levels and still include wide safety margins. This gives us the knowledge and confidence that the reactors are well within safe limits of operation.”

Background information:

The two advanced gas-cooled reactors at Dungeness B, along with our other AGR power stations, are made up of thousands of graphite bricks. This graphite core acts as a moderator – something that slows down fast neutrons sustaining the nuclear reaction.

We know how graphite behaves over time, and expect to see cracks and a loss of mass as part of the normal ageing process. This is a phenomenon known about and anticipated for within the safety regulations.

Those safety regulations are set very conservatively, well within wider safety margins, so we can be absolutely confident that the reactors remain safe to operate even when they appear to be close to the current limit.