Office for Nuclear Regulation

Dungeness B Power Station - Electrical Outage Inspection

Executive summary

Purpose of intervention

This report covers an inspection at EDF Energy Nuclear Generation Limited’s (EDF Energy NGL) Dungeness B site. The inspection considered the electrical activities undertaken as part of the 2015 Statutory Outage on Reactor 22 as well as reviewing of actions in response to previous inspections.

Interventions Carried Out by ONR

As part of this intervention, I carried out compliance inspections against Licence Condition (LC) 28, ‘Examination, Inspection, Maintenance and Testing’ and LC 30, ‘Periodic Shutdown’.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

In respect of the outage, routine maintenance activities are in progress with the work generally ahead of the programme. For those activities undertaken, no significant issues have been identified. The replacement of key transformers is on-going with no issues expected. The remaining maintenance activities are routine, again with no expectation of issues. A review of a sample of the maintenance paperwork showed that the activities had been completed and correctly signed off.

I confirmed that EDF Energy NGL had addressed all the actions I had raised at previous electrical interventions and they were all satisfactorily closed.

I was advised that the maintenance of one 415V non-nuclear safety related switchboard during this outage had previously been repeatedly deferred. Although I noted that EDF Energy NGL committed to complete this work during this outage, from a conventional safety perspective, I did not consider the repeated deferral an acceptable situation. I have raised regulatory actions with the licensee to ensure the prescribed maintenance is completed on this and all the remaining relevant switchboards on site.

In respect of the site walkdown, the condition of the site was generally good with only a few defect tags, all of a minor nature, observed.

Conclusion of Intervention

In general, I am content with the progress the licensee is making with their electrical power LC30 activities in support of the outage. I consider that the licensee is delivering against its planned outage activities. As a result, I consider that an IIS Rating of 3 is appropriate in this case.

Due to the issue in relation of the deferred switchboard maintenance, I consider that an IIS Rating of 4 is appropriate in respect of LC28 compliance.