Office for Nuclear Regulation

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Hinkley Point B - Follow-Up Visit - Corrosion Under Insulation/Concealed Systems Intervention

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a follow up inspection of certain arrangements implemented at Hinkley Point B power station (HPB) 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 HPB during a previous inspection in May 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 the ONR Delivery Management Group Lead for Engineering and an additional Structural Integrity Inspector. The inspection took place on 30 November 2016 and involved discussions with a number of EDF 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

The objective of the inspection was to judge the adequacy of revised arrangements at HPB relating to management for corrosion of their concealed pipework. HPB has implemented these revisions in order to complete actions raised during a previous inspection visit in May 2016.

These actions related to providing ONR with details of the revised structure at HPB 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

I am satisfied that HPB is implementing adequate arrangements to manage the integrity of concealed pipework. I have sampled corrosion management working group meeting minutes that demonstrate a suitable level of detailed discussions relating to corrosion remediation and identified a number of key actions for resolution, with clearly identified responsibilities.

Following my review of their revised internal engineering instructions, I am satisfied that HPB are addressing the key issues to consider when sentencing degraded pipework and structures.

I am satisfied that process of prioritising corrosion remediation explained by the Corrosion Co-ordinator and Mechanical Lead, in conjunction with monitoring, will provide a suitable level of oversight to enable the effective remediation of corrosion related defects.

I am satisfied that process described by HPB to address category 3 and 4 corrosion demonstrates a pragmatic approach for the remediation of currently less significant corrosion before it progresses to become a challenge to system integrity.

I am satisfied that HPB has made significant progress in sentencing and prioritising corrosion related defects. The Corrosion Co-ordinator confirmed that the station aim is to understand the condition of all significant concealed pipework by the end of 2017.

Conclusion to Intervention

I am satisfied that the actions raised in my previous visit to HPB in May 2016 and monitored via ONR regulatory issue number 4511 can now be considered closed.

Based upon review of sampled documentation, discussions with station engineers and plant walk downs, we judged that the arrangements and their implementation, associated with concealed pipework and corrosion under insulation currently conform to a Green rating.

As a result of our visit, I  have the following recommendations: