Office for Nuclear Regulation

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Phase 1 Benchmarking visit to Sizewell B Power Station as part of the Corrosion Under Insulation / Concealed Systems Intervention

Executive summary

Purpose of intervention

The purpose of this intervention was to conduct a benchmark inspection of the arrangements in place at Sizewell B power station (SZB) to manage the integrity of concealed pipework, with an emphasis placed upon how corrosion is managed. The work was carried out as part of the planned intervention task sheet TS015 - "Pipework - Material Condition - Corrosion Under Insulation (CUI) and Concealed/Buried Systems".

I carried out this inspection accompanied by an ONR Structural Integrity Inspector. The inspection took place on 20 and 21 July 2016 and involved discussions with a sample of EDF Nuclear Generation Limited's (NGL's) employees responsible for the operation and safety of the plant. A plant walk down was also undertaken.

Interventions Carried Out by ONR

The objective of the inspection was to obtain information relating to the licensee's arrangements for managing corrosion of their concealed pipework, in order to identify any areas of positive operational experience, or shortfalls against our expectations. I concentrated my intervention on items I judged important to nuclear safety, focussed upon Structural Integrity.

The inspection reviewed the procedures, roles and responsibilities of staff associated with the licensee's corrosion management programme and sampled compliance arrangements against license conditions (LC) LC10 (training) and LC28 (examination, maintenance, inspection and testing) to judge the adequacy of the arrangements in place.

Explanation of Judgement if Safety System Not Judged to be Adequate

We judged that the arrangements and their implementation, associated with concealed pipework and CUI currently conform to a green rating, in accordance with the ONR inspection rating guidelines.

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

The licensee demonstrated that there is a well-managed process in place at SZB to establish the integrity of concealed pipework, particularly relating to external corrosion and CUI. At the time of our visit, there were several work packages in the process of being completed across the site in alignment with the site Material Condition Programme. We judged that there is a consistent resource being allocated to manage and facilitate the examination, inspection, maintenance and remediation activity in accordance their programme.

In our opinion, the Material Condition Programme Lead (MCPL) and Material Condition Programme Co-ordinator (MCPC) demonstrated a good understanding of their responsibilities and provided evidence that these duties are being fulfilled adequately at SZB site, in line with the licensee's Company Technical Specifications (CTS). We identified several areas that we considered to be of a good standard with regards to the maturity of the Material Condition programme, which included the sharing of operational experience across the fleet and a good level of training and engagement with staff.

We judged the quality of the corrosion awareness training that has been rolled out across site to be good, with notable areas relating to the use of targeted corrosion examples for SZB site, corrosion focussed plant walk down training and the intention to provide training to station operations staff, which is beyond that required by the CTS.

Records and inspection results for selected areas of pipework with nuclear safety significance were selected for review and judged to be adequate against the requirements of LC28.

Conclusion of Intervention

From the scope of our inspection and the information that we have sampled, we judge that the arrangements and implementation of SZB site's corrosion management under the Material Condition Programme currently conform to a green rating, for the examination, inspection, maintenance and testing of pipework that may affect safety.

SZB have demonstrated that adequate processes are in place to manage the integrity of their concealed pipework with relation to corrosion under insulation, and in some instances, demonstrated that activities were being undertaken that were in excess of those required by the CTS.

No further actions or issues were identified as part of this inspection. One recommendation was made for ONR to continue monitoring the good progress being made at SZB site, through engagement with the licensee's central technical organisation (CTO) as part of ONR's ongoing fleet wide intervention on corrosion and ageing management. This may include a further site visit to SZB in 12-18 months to observe the completed work packages being undertaken as part of the Material Condition Programme.