The purpose of this intervention was to undertake a Licence Condition (LC) 28 compliance inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Dungeness B (DNB) power station, in line with the planned inspection programme. This intervention is one of a number of LC28 compliance inspections performed by ONR during the periodic shutdown of DNB Reactor 21 (R21) to inform the ONR decision whether to issue a license instrument granting consent for the return to service of DNB R21 following its 2017 statutory outage. This intervention specifically focused on arrangements for graphite core examination, trepanning and gas chemistry.
I visited DNB on 11 and 12 July, alongside my colleagues. The first day was to review the graphite inspection and trepanning arrangements taken by NGL during the periodic shutdown. During the second day of the visit, we have reviewed the gas chemistry control process with the station chemist (GB) and discussed the gas bypass plant control arrangements with the system engineer (MW). During my inspection, I have considered the following items:
At the time of my visit, the licensee had completed all five fuel channels planned for inspection and the 12th graphite sample was being retrieved from the first trepanned fuel channel. There was nothing to suggest that the licensee could not meet the target requirements within the planned schedule. An assessment report will be produced subsequently to consider whether the work performed was sufficient and whether the findings are consistent with the current safety case. I have listed the key findings from this inspection below:
After my discussion with the system engineer, I consider that further plant improvements may still be achieved at DNB. For example, the operating regime of the gas bypass plant could be reviewed against other AGRs. I will consider this issue further as part of my assessment of the DNB third Periodic Safety Review.
Based on the sampling undertaken as part of this intervention, I did not identify any significant shortfall in NGL’s inspection arrangements. I am therefore satisfied that the LC 28 arrangements in place are adequate and have been adequately implemented. I judge that the licensee is in a good position to complete its full scheduled programme of graphite inspections. I have therefore given this inspection an ONR rating of Green - adequate.
A forthcoming assessment report will consider whether the results are consistent with the graphite safety case, once the inspection schedule has been completed and make a recommendation with regard to the return to service of DNB R21.