Context: Hunterston B’s Unit 3, a 490-MWe advanced gas-cooled reactor, has been off line since March 2018, following inspections that identified cracks in excess of the allowable number in the graphite bricks that form the reactor core. Its companion reactor, Unit 4, a 495-MWe AGR, was taken off line in October 2018, also for cracks in the graphite core. While fewer cracks had been identified in Unit 4’s core, experts predicted that the number would soon exceed the established safety limit.
In the summer of 2019, the ONR granted permission for Unit 4 to be returned to service for a period of approximately four months, leading to a continuous run from August to December of that year. The ONR is currently assessing the safety case for Unit 4, and its current expected return-to-service date is September 17. Subject to regulatory approval, EDF is planning for two runs of six months for the unit.
What they’re saying: “I am satisfied that the detailed safety justification provided by the licensee is sufficient to demonstrate that Reactor 3 can operate safely for this period of operation,” said Donald Urquhart, ONR deputy chief inspector. “We applied stringent national and international standards when making our decision, have scrutinized the nature of the cracking observed in Reactor 3, and are satisfied that it will not prevent the reactor from operating safely or impede its ability to be shut down if required during this period of operation.”
Commenting on the decision to initiate the plant’s defueling earlier than scheduled, Simone Rossi, EDF Energy’s chief executive officer, said, “I am extremely proud of all those who have run Hunterston B for more than 40 years. Today’s announcement underlines the urgent need for investment in new, low-carbon nuclear power to help Britain achieve net zero and secure the future for its nuclear industry, supply chain, and workers.”
