Office for Nuclear Regulation

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Hinkley Point B and Hunterston B

24 February, 2017

The Office for Nuclear Regulation has today published its assessment of the Periodic Safety Review (PSR) for two of Britain’s nuclear power stations, alongside an update of EDF Energy Nuclear Generation Ltd’s (EDF) revised graphite core safety case.

Following a high level of interest in graphite core aging in AGR reactors ONR, the nuclear safety and security regulator, has taken the step to announce its conclusions

As part of its robust and extensive inspection and assessment regime, ONR confirms that EDF has carried out an adequate Periodic Safety Review for the Hunterston B power station in Ayrshire and Hinkley Point B power station in Somerset.

To comply with a nuclear site licence, a periodic review – a comprehensive study of plant safety – is carried out every ten years to justify continued safe operations. This requirement means that the site licence company regularly reviews and reassesses safety at nuclear sites, making improvements where necessary. ONR assesses this review to ensure it has been rigorous in underpinning a further period of plant operations.

ONR has also accepted EDF’s revised graphite core safety case for both sites, but has included a number of recommendations as part of this acceptance. These significant assessments were directly relevant to our decisions in relation to the PSR.

The revised safety case provides new limits and conditions of operation in response to keyway root cracking of the graphite in the core, which is an expected part of the aging process as reactors get closer to their end of life. Acceptance of the safety case is also reliant on a revised inspection and monitoring strategy.

Dr Richard Savage, Chief Nuclear Inspector said: “From our extensive review of the safety case processes and procedures, we confirm that EDF has justified future operations for the period through to end of generation (currently 2023) and defueling activities to 2027.

“However, ONR’s confirmation is subject to their operations being supported by a detailed understanding of the condition of the core at each reactor must undertake regular inspections and assessment of the graphite cores to demonstrate that it remains within the limits and conditions defined in the safety case.

“Our assessments in a range of technical disciplines, along with our frequent specialist inspections, and discussions with external experts, led ONR to make a number of recommendations with the aim of improving future safety cases. This includes the requirement for NGL to prepare a safety case for the graphite core, defining the safety limits marking end-of-generation.

“We are here to hold the nuclear industry to account and ensure that duty holders operate in a safe and secure manner. This is always at the forefront of our thinking and we will continue to make certain that any safety case remains adequate and that the safety of operations is confirmed through our ongoing assessments and inspections.”