EDF Energy has extended an outage at its Hunterston B-2 reactor in Scotland to 5 August as it continues to investigate cracks in its graphite core.The 495-MW advanced gas-cooled reactor (AGR), which began commercial operation in March 1977, was scheduled to come back online on 22 July. It has been offline since October after routine inspections found cracks in its graphite core and the restart has been delayed several times since.