Office for Nuclear Regulation

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Dungeness B - Corrosion Management Intervention

Executive summary

Purpose of Intervention

The purpose of this intervention was to conduct an inspection to establish the adequacy of arrangements implemented under the site corrosion management programme. The work was carried out as part of the Office for Nuclear Regulation (ONR) planned intervention task sheet TS027 - "Management of Corrosion - Concealed and Buried Systems" and task sheet TS023 - "Management of Storage Tanks and Vessels".

I carried out this inspection accompanied by the ONR Dungeness B site inspector and two additional Structural Integrity Inspectors. The inspection took place from the 7th to the 9th of November 2017, and involved discussions with a number of EDF Energy Nuclear Generation Limited's (NGL) employees responsible for the operation and safety of the plant. A targeted plant walk down of the systems selected for sampling was also undertaken.

Interventions Carried Out by ONR

The primary aim of the inspection was to perform a follow up visit to assess the adequacy of revised management arrangements related to the corrosion management programme, in response to a number of actions raised from previous ONR inspection which identified shortfalls with respect to the management and prioritisation of corrosion related plant inspections and subsequent defect remediation activities.

Additionally, ONR took the opportunity to review the adequacy of the licensee's arrangements for managing plant material condition of storage tanks and buried pipework that are important for safety, against the requirements of LC 28.

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

With respect to the primary aim of the inspection to review the licensee's progress in response to ONR's previous regulatory engagement, I am content that for the items sampled on nuclear safety significant systems; DNB has demonstrated it has a process to effectively manage significant corrosion related defects. They were also able to show that known significant corrosion that could challenge nuclear safety has been remediated. I consider DNB has been able to demonstrate that their corrosion management team is established and embedded, with reasonable levels of oversight and governance. Therefore I consider that action 16-011-02 contained in Regulatory Issue 4385 can be closed. From my discussions with station staff and sampling of their corrosion defect database, I do not consider that DNB has demonstrated a robust means of the recording of judgements made in relation to the prioritisation of corrosion defect remediation. Therefore action 16-011-03 within Regulatory Issue 4385 remains open.

With respect to the additional aim of the inspection on the management of buried pipework and storage tanks important for safety, I am broadly satisfied that the licensee has adequate arrangements in place for managing examination, inspection maintenance and testing. My inspection has identified a number of areas for improvement, however I am satisfied that the licensee is already taking the necessary steps to address my concerns through the implementation of revised processes and procedures to improve their understanding of plant material condition as part of the fleetwide corrosion management programme.

Conclusion of Intervention

In terms of the overall intervention, on balance and from the information sampled, I judge that the arrangements for the management of corrosion of concealed systems at Dungeness B, currently conform to an AMBER rating, against the requirements of LC28.

From the information sampled, I judge that the licensee's arrangements for the management and understanding of plant material condition of tanks, vessels and buried pipework at Dungeness B, currently conform to a GREEN rating with no formal action necessary, against the requirements of LC28. Whilst ONR is satisfied that Dungeness B has demonstrated an understanding of plant material condition for buried pipework important for safety, further information has been sought with regards to the ECWS discharge pipework replacement project.

Recommendations

I propose the following recommendations as a result of this intervention: