Britain has eight remaining nuclear power stations, which typically generate about a fifth of the country’s electricity. They have been operated since 2009 by EDF, the French power company that owns 80 per cent. Centrica, the British Gas owner, owns the other 20 per cent. All bar one of the existing stations, including Hinkley Point B, comprise twin advanced gas-cooled reactors, or AGRs, built between the 1960s and the 1980s. All the AGRs are scheduled to close permanently between 2023 and 2030, but all also have graphite cores that bring their lifespans into doubt. “They will all at some stage exhibit some form of cracking towards the end of life,” Richard Bradfield, chief technical officer for generation at EDF Energy, said. “There are two irreplaceable components on an advanced gas-cooled reactor: the graphite and the boilers. Even from day one back in the 1960s, it was always going to be, ‘Which is going to win?’” At Hunterston B in North Ayrshire, Hinkley Point B’s sister station, the graphite is damaged more severely. At an inspection in March 2018, EDF found more cracks than it expected in one of the reactors. Its restart date, originally scheduled for later that year, has been delayed repeatedly pending approval from the Office for Nuclear Regulation. The other reactor, which was found in October 2018 to be slightly less cracked, has been allowed to run for only four months since. To restart them, EDF must prove that control rods can still be inserted through the graphite to safely shut down the reactors, even in the event of a huge earthquake. “We describe it as a once-in-10,000-year event; an earthquake magnitude such that has never been seen in UK and would have to be pretty much on top of the power station,” Mr Bradfield, 53, said. EDF has spent more than £200 million on tests, inspections and creating quarter-scale models of the reactor cores that are shaken to mimic a quake to try to prove that the graphite is safe. Recently it submitted a new safety case to the regulator for the most severely cracked Hunterston reactor, which it hopes will be approved in July to allow the next six months of operation. That may pave the way for approval for the second reactor and, later in the year, for Hinkley Point B, which has “pretty much the same safety case”. A third plant, Dungeness B in Kent, has been offline for different safety issues since the late summer of 2018, when repairs needed to steam pipes were identified. EDF then discovered that further work that was needed to tackle corrosion on the boiler and it has repeatedly delayed the restart. Mr Bradfield said that the boiler design at Dungeness was “very different” to the other AGRs and probably would be the life-limiting factor for the plant. However, he said that the issues were “manageable” and that the company aimed to present a safety case shortly to seek to restart in September.
Times 9th June 2020 read more »