Reactor 4 at EDF-owned Hunterston B power station is safe to begin operating again despite having a cracked core, the Office for Nuclear Regulation (ONR) has stressed.
The ONR today (20 August) announced that EDF has been given the go-ahead to operate the reactor for the next four-month operation period.
A team of specialist inspectors from EDF’s own internal independent nuclear assurance team, the Nuclear Safety Committee, as well as the ONR, conducted the investigations after reactors 3 and 4 were taken offline last year.
Specifically the inspections focused on whether the cracking observed in the reactor’s graphite core would compromise safety requirements. The assessment concluded that an “adequate safety case” has been provided to allow a further 16.025 terawatt days operation period.
In addition, EDF has worked with academics from the University of Bristol to research a range of scenarios including how the core would be affected by extreme conditions such as a large magnitude earthquake.
In total, £125 million of research in collaboration with other UK universities has been invested.
Cracked graphite cores – What the ONR says
Over time during reactor operation, the graphite bricks age and their properties change due to interaction with the radiation environment and the reactor coolant. This can lead to the graphite losing weight and the development of cracks in the graphite bricks, both of which are well-known phenomena and have been the subject of significant interest by the industry, academics and the regulators for many decades.
Donald Urquhart, ONR deputy chief inspector, said: “We have made the decision to allow Reactor 4 at Hunterston B to return to service, following a long and detailed assessment of the safety case submitted by EDF Energy.
“My team of expert inspectors, along with an independent panel of graphite experts, have worked for a number of years on the issue of cracking and shrinkage within graphite cores.
“The licensee, EDF Energy, has completed an extensive programme of work to analyse the condition of the graphite cores at Hunterston B and other reactors in the UK to increase their knowledge and provide sufficient evidence to ensure safe operation.
“I have met with many of our interested stakeholders during the course of our assessment and I recognise that this is an emotive issue, but let me reassure you – it is ONR’s statutory role to examine the evidence objectively and make our decisions based on that.
“Nuclear safety remains our utmost priority and we would only allow a reactor to re-start with clear evidence that it remains safe for workers and the public.”
According to EDF the power station avoided 1.3 million tonnes of carbon emissions in 2018, equivalent to taking 590,000 cars off the UK roads for a year.
The safety case for the return to service of Reactor 3 at Hunterston B has been submitted to the ONR for their consideration.