New cracks found in one of the reactors at EDF’s Hunterston B nuclear power station were expected and don’t pose a safety concern, according to the firm.
The 460MW reactor returned to service on Sunday evening after it was given approval to restart by the Office for Nuclear Regulation (ONR) on October 1, but EDF said the fissures in two of the 3,000 graphite fuel bricks that make up its No 4 core were discovered during a periodic shutdown since 1 August 2014 and are known about by the regulator.
The plant in Ayshire, Scotland, has two advanced gas-cooled reactors, came online in 1976. It was due to close in 2016, but EDF has already extended its working life to 2023.
Station director at Hunterston B Colin Weir said: "Every time we take the reactor out of service for planned maintenance we inspect the graphite core which is made up of around 6,000 bricks.
“During the current Hunterston outage we found two bricks with a new crack which is what we predicted during Hunterston B's lifetime as a result of extensive research and modelling.
“It will not affect the operation of this reactor and we also expect that a few additional cracks will occur during the next period of operation. The small number of cracked bricks found during routine inspection is in line with our expectations, the findings have no safety implications and are well within any limits for safe operation agreed with our regulator.”
In August EDF had to shut down four of its nuclear reactors in the UK as a precautionary measure after a defect was found in its aging Heysham 1 reactor, but the firm said last month that it had resolved the problem and would be able to restart the reactors between the end of October and December following approval from the ONR.