What happens inside a nuclear reactor?

The BBC has learnt that a vital safety limit at the Dungeness B nuclear power station is being raised to extend the life of the reactor.

Without the rule change, made by the Office of Nuclear Regulation, the plant would have had to shut down, perhaps within as little as a year.

The new, higher limit means it should be able to continue generating for another four.

The BBC's Rob Broomby spoke to Professor Paul Mummery of Manchester University to find out about the changes taking place to graphite bricks inside the reactor.