Office for Nuclear Regulation

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Follow-up inspection at Dungeness B

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a follow up inspection of certain arrangements implemented at Dungeness B power station (DNB) to manage the integrity of concealed pipework. The visit took place to establish the adequacy of arrangements implemented as a result of actions placed on DNB during a previous inspection in April 2016. The work was carried out as part of the planned intervention task sheet TS015 – “Pipework - Material Condition – Corrosion under Insulation and Concealed/Buried Systems”.

I carried out this inspection accompanied by an additional Structural Integrity Inspector. The inspection took place on 10 & 11 January 2017 and involved discussions with a number of EDF Energy Nuclear Generation’s (NGL) employees responsible for the operation and safety of the plant; plant walk downs were also undertaken.

Interventions Carried Out by ONR

This inspection visit was intended to establish the adequacy of the revised arrangements to manage corrosion of concealed pipework at DNB following a previous intervention in April 2016.  The previous intervention identified a number of concerns with regard to the management of corrosion of concealed pipework and left actions to re-visit the station to assess the revised processes.

These actions related to providing ONR with details of the revised arrangements at DNB to manage the integrity of concealed pipework and to provide a demonstration of how sentencing and remediation of defects found on all pipework is conducted. I concentrated my intervention on items I judged important to nuclear safety, focussed upon Structural Integrity.

The inspection reviewed the revised procedures and sampled compliance arrangements for selected systems against licence condition (LC)28 (examination, maintenance, inspection and testing) to judge the adequacy of the arrangements in place.

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

It is clear from the current visit that the station had initially made only very limited progress to address the concerns identified during our previous inspection visit in April 2016.  A number of reasons were given for this, but progress has only been made since October 2016 following an internal NGL corrosion assist visit.  Since October 2016, the station has taken a number of steps to address some of the shortfalls identified in our previous inspection visit.  For example, the corrosion management team is now completely different from the team seen in April 2016; a new investment delivery post has been created and steps have been taken towards coordinating the various examination requirements applied by the station.  The station has also identified all the historic un-remediated corrosion related defects and is beginning to prioritise addressing this backlog of work.

This new commitment is encouraging and the station now appears to be taking the management of corrosion much more seriously. However, the revised management arrangements have only recently been put in place and cannot be fully tested; the inspection regime has yet to be shown to be adequate; and much of the necessary remedial work has to be completed.  

Revised management arrangements.  It is too soon to test these arrangements; however, I already have specific concerns with regard to the extra responsibilities which have been allocated to the new Corrosion Coordinator (CC) in addition to those associated with corrosion.  It is not clear how these additional duties are compatible with the CC role when the site does not yet have mature, embedded arrangements, there is a significant backlog of work to address and the individual has limited experience of the station.  Given the new commitment of the station to this work, it is not clear why the station should consider this to be tenable. It has been noted at interventions at the licensee’s other sites that the CC tends to hold multiple roles, including FAC coordinator, PSSR coordinator, pipe inspection lead and system engineering roles. In these cases, it has generally been noted that the CC has significant plant experience and has held a number of relevant roles previously, to complement the duties required under CTS/031.

Training. There is was no evidence provided that the CC had attended the site training course on corrosion awareness. To account for this, the CC has received training from the fleet corrosion coordinator and was able to demonstrate an awareness of corrosion. Attendance of the training course provided by NGL would provide demonstrable evidence of appropriate training and provide useful experience of planning and delivering the course for site audiences in the future, to promote an understanding of the specific important corrosion issues on DNB power station.

Inspection regime.  One of the major challenges identified at the last inspection visit was that the site have undertaken a range of inspection activities on concealed systems over time and that the consistency, control and coverage of that work is difficult to establish.  These concerns were reinforced in the current visit where it was found that degradation of pipework in the Essential Cooling Water (ECW) system in the services basement had only recently been identified.  However, considering the risk category of the system, corrosion awareness training content and communication of OPEX from across the fleet, this should have been identified earlier.  Also, during the review of the Emergency Generation system the arrangements to identify a scope of inspection, produce plant walkdown reports, involvement by the System Engineer, categorisation and recording of degradation and process oversight was not consistent with, or as effective as, arrangements demonstrated elsewhere in the fleet.

Remedial Work.  The other major challenge posed by the site undertaking a range of inspection activities over a period of time is that the defects identified by these inspections have not been remediated in an effective manner, there is a significant backlog. It was recognised at my last inspection in April 2016 that the remediation of corrosion related defects was not effective.  Whilst it is encouraging that the Work Management team have now reviewed all recorded and un-remediated corrosion related defects at DNB and there is evidence that some work is now starting to be progressed, the number of potentially significant defects is large and I am disappointed that more evidence of remedial work was not available.  It is also notable that some of the remediation had initially been identified a number of years ago, and its condition today could be worse.  Therefore, it is not clear that DNB fully understands the current condition of its systems.

Conclusion to Intervention

DNB falls short of where I would have expected them to be at this stage following our visit in April 2016 and in comparison with the progress made by the rest of the fleet.  DNB were therefore unable to demonstrate that they are fully taking ownership of the challenges posed to the station from corrosion. I remain concerned that the site is not yet able to demonstrate that the threat posed by the corrosion of concealed systems is being adequately managed.

I am also not satisfied that DNB has provided sufficient evidence to close actions 16-011-02 and 16-011-03 raised in my previous visit in April 2016 and monitored via ONR issue number 4385.

I have identified recommendations for DNB to provide evidence to demonstrate how they will address these concerns.

Based upon a review of sampled documentation, discussions with station engineers, plant walk downs and compared to progress made elsewhere within the fleet, we judged that the arrangements and their implementation, associated with concealed pipework and corrosion under insulation currently conform to a Red rating. In accordance with ONR guidance on the application of a Red inspection rating, the findings from this intervention inspection will be processed through the enforcement management model (EMM) to determine the most appropriate enforcement action.

Following my inspection, I have made the following recommendations:

Recommendation 1: DNB should develop and implement a targeted plan to effectively manage corrosion of its concealed systems and communicate this plan to ONR within 3 months.

The plan should address the following:

Recommendation 2: ONR should revisit DNB at an appropriate time to assess if the necessary actions have been completed to address our concerns.

Recommendation 3: The current issue number 4385 should be revised to reflect the findings from this inspection and its level increased from 4 to 2.