Office for Nuclear Regulation

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Sizewell B - SBI19 Essential Power Supply System

Executive summary

Purpose of Intervention

This was a planned inspection of EDF Energy Nuclear Generation Ltd.’s (NGL’s) Sizewell B power station, undertaken as part of the planned intervention strategy for the Operating Facilities Division (OFD) of the Office for Nuclear Regulation (ONR). I (the Sizewell B nominated site inspector) carried out the inspection with an electrical engineering specialist inspector.

The work was carried out in-line with the planned inspection programme contained in the Sizewell B Integrated Intervention Strategy (IIS).

Interventions Carried Out by ONR

We performed a safety case informed systems based inspection (SBI) of the essential power supplies system to judge the system performance against its safety function. The function of the essential power supplies system is to provide a reliable, on demand, power supply for all necessary electrical loads during post trip operation for all essential post trip operations. Through examination of the system, compliance inspections were performed against the following License Conditions (LC) which are applicable provisions of the Energy Act 2013:

The ONR site inspector also carried an inspection to evaluate compliance with LC14 (Safety Documentation) and met with personnel to review the licensee’s progress against issues recorded on the ONR issues database.

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Explanation of Judgement if Safety System Not Judged to be Adequate

From the areas sampled during this inspection, we judged that the overall the essential power supplies system met the requirements of the safety case.

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

From the system based inspection on the essential power supplies system we concluded that:

The principal focus of my LC14 inspection was to evaluate implementation of NGL’s arrangements to deal with Safety Case anomalies. I am satisfied that NGL have developed and implemented a graded approach for the production of documentation assessing the impact of such anomalies. One administrative non-compliance was noted in respect to implementation of the NGL’s safety case health review process. NGL have committed to address this issue which will be tracked via an entry on the ONR issues database.  Notwithstanding this issue, overall I judge that the following inspection rating against LC14 is appropriate: Green.

Conclusion of Intervention

There are no findings from this intervention that could significantly undermine nuclear safety. At present, no additional regulatory action is needed over and above the planned interventions at Sizewell B power station.