The Nuclear Free Local Authorities (NFLA) continues to take a deep interest in the safety of the Hunterston B Reactors 3 and 4 in North Ayrshire. These have now remained closed for some considerable time due to a proliferation of keyway root cracks in their aging cores. The NFLA Secretary and Dr Ian Fairlie recently met with senior staff in the Office for Nuclear Regulation (ONR) to discuss this matter for the short, medium and longer-term.
The Hunterston B reactors are the oldest Advanced Gas Reactors (AGR) remaining in operation in the UK now. The reactors are presently due to close in 2023. Increased concern over their safe operation arises after it was found that Reactor 3 now has an estimated 377 keyway root cracks and Reactor 4 has an estimated 209 keyway root cracks.
At the meeting (1), the ONR noted that it was still considering EDF’s safety case for whether it can reopen Reactor 4 for further operation. An issue that had recently been identified concerned the need for further analysis of the significance of crack openings greater than 1.2 cm wide (i.e. around ½ inch), a small number of which are predicted to occur in the next period of operation. ONR is pursuing further evidence on this matter and is now in detailed correspondence with EDF about such cracks and other safety matters. It may be a few more weeks before a decision will be made.
In terms of Reactor 3, ONR has now received the Safety Case to support its return to service. The main report was over 200 pages long and contains many additional technical references. ONR had started an assessment of this report and it was expected to take a number of months to complete its examination.
A useful part of the meeting was to discuss an approach EDF was developing to define ‘End of Life’ criteria for the AGR reactors, in other words, the maximum levels of core degradation that can be demonstrated to be safe, whilst leaving a significant margin of safety. Such criteria would need to be fully agreed by ONR. These included not only the number of cracked bricks, but also their sizes (i.e. how wide they were) and also the numbers and locations of multiply-cracked barrels (i.e. barrels with 3 or 4 cracks or more stretching from top to bottom). In ONR’s view, these latter issues were likely to be more important than the numbers of cracked barrels. The most important factor was for EDF to demonstrate to ONR that all 81 control rods could be inserted unimpeded, even in a 1 in 10,000 year seismic event.
The NFLA welcomes the openness in its discussions with the ONR on these matters. In the NFLA’s view the two reactors should not be reopened for service but rather closed on the basis of the reactors age and increased evidential degradation to them. Hunterston B should then go into a process of ‘accelerated decommissioning’ that could protect the jobs on site in the short to medium term.
The NFLA’s view is reinforced by the publication of a recent ONR report over four notable safety incidents at Hunterston in recent months.
EDF Energy is currently examining three incidents that took place between April and June, in cooperation with the ONR. The incidents included cooling for a reactor being temporarily lost, a shutdown pump failing and smoke coming from a control room panel. EDF is also investigating a fourth incident from earlier in the year when a power failure prevented cooling gas from being circulated around a reactor. These incidents have just come to light in the latest safety reports on Hunterston B published by the ONR. (2) Whilst there were no radiological consequences from them, this is largely due to the reactors not being in operation. A loss of cooling is of real concern as the consequences of such an eventuality when the reactors are in full operation could have been extremely serious.
NFLA Scotland Convener Councillor Audrey Doig said:
“I welcome the ONR talking with us over such a serious issue as the resumption of the Hunterston B nuclear reactors. In our view, given the reactors are to close in 2023, this should be brought forward and the reactors should not restart. Keyway root cracking is symptomatic of stress in the reactors from their age, and it is much better to be safe than sorry. The other recent safety incidents over the past few months at Hunterston reinforce that view. Jobs could be protected in the short term through a period of accelerated decommissioning and use of the ‘Just Transition’ programme being developed by the Scottish Government for the longer-term.”
Ends – for more information please contact Sean Morris, NFLA Secretary, on 00 44 (0)161 234 3244.
Notes for editors:
(1) The agreed note for the meeting between the NFLA and the ONR is on the NFLA homepage and attached with this media release.
(2) The Ferret investigative journalism service, 2nd August 2019