Office for Nuclear Regulation

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Sizewell B - LC28 Compliance Inspection - Structural Integrity

Executive summary

Purpose of Intervention

This report records the findings of an intervention visit to the Sizewell B Nuclear Power Station during the 2017 periodic shutdown. The intervention was undertaken to confirm the adequacy of the work conducted by the licensee, EDF Energy Nuclear Generation Limited (NGL), to comply with the requirements of Licence Condition 28, examination, inspection, maintenance and testing.

Interventions Carried Out by ONR

I undertook on-site meetings and plant inspections with relevant staff from NGL to determine the adequacy of the work being undertaken on the reactor in complying with the requirements of Licence Condition 28. I concentrated my intervention on items I judged important to nuclear safety, focussed on structural integrity.

I sampled aspects of the inspection programme undertaken during the periodic shutdown on reactor systems that comprise of a pressure boundary with a nuclear safety significance.

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

I visited site approximately one third of the way through the periodic shutdown. The status of the inspections highlighted satisfactory progress on the surface and volumetric inspection programme, with 85 out of the 342 inspections completed at the time of this inspection.

I sampled the inspection work that had been undertaken as part of the surface and volumetric inspection programme, looking at both the inspection work itself and the categorising of the results, and was satisfied with what I found.

I undertook a plant walk down during my visit, escorted by an inspection engineer. NGL staff were able to provide satisfactory explanations of both the operation of the systems and the inspection/maintenance of the systems planned or already performed during the periodic shutdown.

I discussed progress on examinations and inspections undertaken by the Pressure Systems Safety Regulations (PSSR) Competent Person (CP) during the periodic shutdown. The work was progressing to plan and no significant issues had been found to date.

I discussed the progress of the flow assisted corrosion (FAC) programme to date. No adverse findings were reported and progress appeared to be reasonable given the timing of our inspection.

An emergent issue relating to the discovery of a leak in steam generator "D" had been found during the outage. I discussed this with several site staff to better understand the intentions of NGL in regards to its repair, particularly in terms of determining the root cause of the leak. This will be reported separately in a stand-alone assessment report.

Conclusion of Intervention

I judge that, at the time of my visit to the Sizewell B nuclear power station, personnel were conducting their inspections in line with the pre-outage intentions documentation and associated inspection specifications. The Licensee appears to be adequately managing any defects or anomalies identified.

I will use the minutes from the remaining SIPs and where practical, dial in to these meetings to monitor for any emerging issues from the inspections that have yet to be completed and report on this in my structural integrity assessment report on the return to service of Sizewell B following its 2017 periodic shutdown.

I will report my findings relating to the steam generator "D" drain line defect in a separate assessment report.

Based on my intervention to date, I conclude that the licensee has performed the work to an adequate standard. I propose that an inspection rating of green is appropriate.

Excluding the consideration of the defect observed in steam generator "D", I support a request under Licence Condition 30 to return Sizewell B to operation following its 2017 periodic shutdown. I will formally conclude this extant matter within a separate assessment report.