The nuclear power station at Hunterston in North Ayrshire has breached radiation safety rules and suffered five other problems with its safety systems.
One of the nuclear plant’s cooling systems – needed to prevent overheating when a reactor is shut down – developed a fault because of confusion over valves. There were other issues with cooling systems, a fuelling machine and the graphite core.
After a series of other heath and safety incidents ONR accused Hunterston’s operators, EDF Energy, of “a lack of sensitivity to industrial safety events”. The company’s emergency arrangements for coping with a nuclear accident also needed improving, ONR said.
Critics have attacked EDF’s safety record, and called for Hunterston’s two ageing and cracked reactors to be permanently shut down. The reactors are “well past their sell-by date,” they argued.
EDF, however, stressed that none of the incidents had put workers or the public at risk and that “stringent safety levels were maintained at all times”. ONR said that the shortfalls were “relatively low level” but that it took “appropriate regulatory action where necessary”.
Reactor three at Hunterston has an estimated 377 cracks in its graphite core and has been shut down since 9 March 2018. Reactor four, which operated for less than four months in 2019, has been shut since 10 December while its core cracks are further assessed.
EDF is currently aiming to restart both reactors in April but it cannot do so until ONR has said they are safe. Planned restart dates for the reactors have been repeatedly postponed over the last two years.
On 22 October 2019 ONR served an “enforcement letter” on EDF because of a breach of the regulations covering radioactive sources. These are materials emitting radiation used by industry as gauges and for inspections.
“The station had failed to adequately account for and label radioactive sources, which resulted in some sources not being subject to the required leak testing,” ONR said.
“The station has recognised these non-compliances and has provided an appropriate plan of action. The radioactive sources were sealed instrument check sources and did not present a hazard to workers or the public.”
It added: “ONR will carry out an inspection to confirm that the enforcement actions have been carried out satisfactorily.”
While reactor four was running at full power in the last three months of 2019 one of its four cooling systems developed a fault. This “post trip cooling system” was “one of the means by which cooling is provided to the reactor when it is shut down”, explained ONR.
EDF had to fix the problem within 31 days otherwise the reactor would have to be switched off. “The investigation established that the isolation of a faulty valve position indicator for the coolant feed system had also isolated the valve actuator control,” said ONR.
“It had previously been understood that the valve position indicator and actuator were supplied from separate electrical supplies.”
The faulty indicator was repaired and it was confirmed there was “sufficient redundancy” as three of the four post trip cooling systems remained operational, ONR added.
“This event did not compromise nuclear safety. Corrective action is being taken to ensure subsequent configuration control.”
There is a need to enhance the operability of the EDF corporate emergency arrangements. Office for Nuclear Regulation
ONR also raised “two regulatory issues of low significance” with EDF about cooling systems, but required no formal action to be taken. One concerned an “incomplete maintenance record card” and the other was because the potential for radioactive tritium in cooling water had not been fully described.
There were also issues with “unauthorised settings” on fuelling equipment and modelling of the mechanical strength of parts of the graphite core. In both cases ONR said that nuclear safety was maintained.
ONR added: “From the evidence sampled, the inspector was satisfied that the events reported during the period, had been adequately investigated and appropriate event recovery actions identified.”
But ONR also stressed the need for improvements in EDF’s approach to conventional health and safety. “A number of industrial safety events highlighted where continued focus on safety is required,” ONR said.
“The station reflected on the causes, which included a lack of sensitivity to industrial safety events, personal accountancy and fuller application of the organisational learning process. A continued commitment to existing improvement plans was expressed by the station.”
In addition ONR required EDF to re-run an emergency exercise conducted on 17 October 2019. This was meant to test responses to a nuclear accident “under security lockdown conditions” with the Civil Nuclear Constabulary (CNC), which polices nuclear power stations.
ONR said: “The exercise was challenging and showed that there is a need to enhance the operability of the EDF corporate emergency arrangements in conjunction with the CNC response procedures.”
Friends of the Earth Scotland argued that the Hunterston B reactors should shut instead of trying to struggle on. “This is a remarkable catalogue of failures, especially from a company entrusted to run probably the most dangerous industry in the country,” said the environmental group’s director, Dr Richard Dixon.
“Losing track of radioactive sources, not understanding how crucial valves work and not paying proper attention to health and safety are pretty strong indictments of EDF fitness to run Hunterston B. The reactors are well past their sell-by date.”
Peter Roche, an Edinburgh-based nuclear consultant, agreed. “These latest revelations really should be the final nail in the coffin for these two reactors,” he said.
“They need to be closed as soon as possible to protect the public from potential accidents caused by cracks in the graphite core, whilst EDF draws up a just transition for the workforce.”
The Scottish Greens also called for alternative jobs for the Hunterston workforce. “The one reliable thing about Hunterston nuclear power station is the inevitability of safety concerns getting worse,” said the party’s MSP, Ross Greer.
“This cannot go on. Yet again, the Office for Nuclear Regulation drags its heels on decisions about restarting cracked reactors while local residents’ concerns only grow.”
Instead of restarting Hunterston, the transition of local jobs into safer and cleaner alternatives should already be underway, Greer argued. “Decommissioning the plant alone will provide jobs for the current workforce for years, whilst eliminating the danger which comes from keeping it running.”
These latest revelations really should be the final nail in the coffin for these two reactors. Peter Roche, nuclear consultant
EDF Energy emphasised that the reactors were safe, and promised improvements. “It is important to be clear that there was, at no time, a risk to workers or the public in connection to these incidents,” said a company spokesperson.
“Nuclear safety is EDF’s priority and Hunterston B power station has a proactive reporting culture, informing the ONR about even very lowest level incidents. We work to strict operating rules and our safety-related site equipment has strength in depth.”
The EDF spokesperson added: “Our stringent safety levels were maintained at all times, but our open reporting culture ensures we now can identify areas where improvements can, and will, be made.”
According to the Office for Nuclear Regulation, every safety incident should be reported. “The UK has a robust nuclear regulatory regime and nuclear operators are required to adhere to the highest standards of safety and security,” said an ONR spokesperson.
“We expect and encourage sites to report all safety incidents to us and the shortfalls detailed in these particular reports are relatively low level. However we consider every event reported to us and will take appropriate regulatory action where necessary to ensure the safety of workers and the public.”
The spokesperson told The Ferret: “As regards ‘sensitivity to industrial safety events’, our site inspector is referring to the sort of conventional health and safety incidents that occur at all large industrial sites. This comment does not refer to nuclear safety concerns and instead involved events related to slips, trips and other minor injuries.
“However it is true to say that this is an area where we want to see improvements and this broader issue was highlighted by our chief nuclear inspector in his annual report where he encouraged the wider industry to apply increased focus in the area of conventional health and safety.”
ONR is awaiting further information from EDF on the cracks in the graphite cores of the Hunterston reactors. They will only be allowed to restart “if we are satisfied that it is safe to do so”, ONR said.
The report on Hunterston B by the Office for Nuclear Regulation
Photo thanks to EDF Energy.