Office for Nuclear Regulation

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Inspection of the Mechanical aspects of the Maintenance conducted during the 2014 Dungeness B Reactor 21 Periodic Shutdown

Executive summary

Purpose of intervention

This report records the findings of my intervention visit to Dungeness B Nuclear Power Station during the 2014 reactor 21 Periodic Shutdown. The intervention was undertaken to confirm the adequacy of the work conducted by the Licensee to comply with the requirements of Licence Condition 28, examination, inspection, maintenance and testing. I was accompanied on my visit by a second ONR (Office for Nuclear Regulation) mechanical inspector.

Interventions carried out by ONR

I undertook on-site meetings and plant inspections with relevant staff from NGL and their contractors to determine the adequacy of the work being undertaken on Reactor 21 in complying with the requirements of Licence Condition 28. The activities examined were selected due to their significance to nuclear safety, with due consideration being given to any fleet wide interventions and included:

The inspection was supported by visits to the following areas:

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Key findings, Inspector's opinions and reasons for judgements made

ONR are pursuing the issue of adequate Foreign Material Exclusion (FME) and working standards for the maintenance of mechanical engineering plant important to safety across the EDF NGL fleet (ONR Issue 729). During the inspection I noted that a considerable amount of work has been undertaken to improve conditions in the CRA maintenance facilities however, some observations and potential areas for improvement were highlighted.

With respect to the GC maintenance facilities I am satisfied that the new facility is an improvement in segregating appropriate components, although some observations and potential areas for improvement were discussed.

I consider that the Station has adequate arrangements in place to monitor control rod drop performance and it is acceptable for the Station to follow its due process in this area; noting that the results will be provided to ONR in the 28 day report.

Due to previous fuelling machine faults the overhaul of a number of the CRAs has had to be deferred via a Category 2 EC. No ONR action is considered necessary at this stage as the Station has adequate plans in place to recover the situation.

The above topics were a chosen sample of mechanical engineering work pertinent to supporting the issuing of Consent to restart the reactor. During the inspection the work and procedures sampled were found to be generally adequate and completed to appropriate standards.

One issue has been raised associated with the plug unit closure elastomer seal material anomaly that requires completion prior to the return to service of R21. This has been shared with the Licensee and will be tracked via the Project Inspector's Outage action tracker. I will track this issue as part of my assessment of the reactor restart.

Conclusion of intervention

I judged that Dungeness B nuclear power station personnel were conducting their inspections in line with the pre-periodic shutdown intentions documentations and were dealing adequately with any defects or anomalies found.

Subject to satisfactory completion of the issue identified with the plug unit closure elastomer seals, I am content to support a Consent for restart of R21 following Statutory Outage 015.

Based on my intervention, I conclude that the licensee has performed the work to an adequate standard. I judge that an IIS rating of 3 is appropriate.

The actions placed during this intervention will be tracked via the Action tracker in place for Reactor 21 2014 outage. This ensures that all actions related to the outage are captured in one location. The Return to Service actions will be closed out prior to consent for re-start being granted. The non-return to service actions will be turned into a single level 3 issue which will be owned by the site inspector. The action I placed during this intervention was: