Office for Nuclear Regulation

This website uses non-intrusive cookies to improve your user experience. You can visit our cookie privacy page for more information.

Dungeness B - Meeting to discuss corrosion under insulation

Executive summary

Purpose of Intervention

The purpose of this intervention was to for the ONR Deputy Chief Inspector and Director, Operating Facilities Division and myself to visit Dungeness B Power Station (DNB) on 23 May 2017 so that the EDF Energy Nuclear Generation (NGL) Region 2 Chief Nuclear Officer (CNO) could provide a response to ONR’s previous letter Ref. DNB 71285/R relating to the management of Corrosion under Insulation (CUI) at DNB. This letter had placed a number of actions on DNB, namely:

Complete a review of the organisation and effectiveness of the corrosion management team, to take full account of the experience and workloads of the individuals concerned, to confirm that sufficient resources are available to manage the effective delivery of a corrosion management strategy.

To undertake a review of the current range of plant inspection processes being utilised to ensure that these are fully aligned and; where appropriate, identify suitable areas for improvement. ONR require demonstration that any areas of improvement are being adequately pursued.

A thorough review of the corrosion related defect backlog to identify any immediate remedial actions that may be required and to develop a longer term plan to address the outstanding items.

The development and implementation of a strategy for remediation of new and emergent corrosion related defects.

The provision and implementation of a plan to provide assurance on the current condition of the plant.

Interventions Carried Out by ONR

The inspection considered the response given by NGL’s CNO against the actions identified in ONR letter Ref. DNB 71285/R and Licence Condition (LC)28 (examination, maintenance, inspection and testing) to judge the adequacy of the arrangements in place to manage corrosion of concealed systems at DNB.

The visit consisted of an introductory discussion with the DNB Station Director and NGL CNO, followed by a presentation by the DNB Engineering Manager, a plant walk down and close out session with the station lead team.

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

I am content with the level of governance and oversight applied to corrosion management at DNB, both locally and at corporate level. NGL should ensure that the current corrosion management process at DNB is sustainable, continuing to receive the appropriate level of attention, resource and funding.

DNB demonstrated that it has applied considerable attention and resource in implementing a team based approach to managing corrosion. However, further improvements are required relating to how DNB records judgements and decisions concerning the prioritisation of corrosion related defects.

During the plant walk down, several areas of improved plant material condition were noted. However, in a number of areas visited during the plant walk down, small unresolved leaks from plant were observed, we were informed that the plant did not have nuclear safety significance. DNB should ensure that defects on systems with a consequential effect on plant with nuclear safety significance are addressed before work in an area is considered complete. The reasons for leaving any defects unresolved should be identified and recorded.

At the time of our visit pipework inspection resource was provided by one Bureau Veritas Engineer Surveyor. I am aware that he also carries out the role of PSSR Competent Person. I consider that these additional obligations may challenge the effectiveness of the corrosion related inspection plan if not carefully monitored and managed by DNB. I also note that the INA phase one visit in April 2017 identified that not all key roles in the organogram were filled. Whilst I am encouraged that DNB has now demonstrated that the team is fully resourced, I would have expected it to be in place prior to the INA visit in April.

Overall, I judge that NGL were able to demonstrate that they have responded adequately to the actions raised in the letter, although this should be subject to further monitoring by ONR, via updates to the existing Regulatory issue number 4385.

Conclusion to Intervention

Based upon review of sampled documentation, discussions with NGL personnel, 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 Green rating.

Following our inspection, I have made the following recommendations: