Office for Nuclear Regulation

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Planned System Inspection – Containment Systems

Executive summary

Purpose of intervention

The purpose of the intervention was to carry out planned inspections in accordance with the integrated inspection schedule for Sizewell A.

Interventions Carried Out by ONR

I carried out a systems inspection of the Containment Systems, specifically focussing on Ventilation and effluent systems.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A

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

I consider that the containment systems inspected meet the safety case functions and are being operated in accordance with the safety case.

Good practice was observed in the format and content of Plant Operating Instructions, which were clear, well-structured and made good use of images. These clearly translated the safety case requirements on to the plant.

To support the Post De-fuelling Safety Case, Sizewell A has developed a safety measure substantiation document. This explicitly confirms that Safety mechanisms have been considered for LC27 compliance, but that none are required. I considered this document good practice in providing clarity on safety measures and safety mechanisms considered and safety measures implemented to support the safety case and meet LC27 compliance.  

One minor shortfall was identified with the clarity of the alignment between limits and conditions and assumptions in the safety case, with those in the fault schedules, however as these limits were clearly visible in operational plant instructions with adequate margin for safety, I was satisfied this is not a safety concern; more one of document clarity.

Conclusion of Intervention

Overall judged that the systems adequately meet their safety case functions and are being operated in accordance with the safety case. I found no issues that significantly affect safety, or that required further regulatory intervention.