Office for Nuclear Regulation

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System Based Inspection – SBI 22 – Essential Electrical System

Executive summary

Purpose of intervention

The purpose of this intervention was to undertake a Licence Condition (LC) compliance inspection at EDF Nuclear Generation’s (NGL’s) Sizewell B power station in line with the planned inspection programme contained in the Sizewell B Integrated Intervention Strategy (IIS) for 2014/15.

Interventions Carried Out by ONR

As part of this intervention, we carried out a system based inspection (SBI) of the Essential Electrical System.  Through examination of this system we performed compliance inspections against Licence Conditions LC 10: Training; LC23: Operating rules; LC24: Operating instructions; LC27: Safety mechanisms, devices and circuits; LC28: Examination, inspection, maintenance and testing. The inspections were based on sampling the implementation of the arrangements in place at the station against each licence condition. 

This intervention also included a compliance inspection against LC 12 duly authorised and other suitably qualified and experienced persons.

Other matters of a routine nature that are deemed unlikely to have a significant effect on nuclear safety, and which are being addressed routinely under the licensee’s arrangements, were also covered during the inspections.

Explanation of Judgement if Safety System Not Judged to be Adequate

From this inspection, we judge that overall the safety provisions applicable to the Essential Electrical System meet the requirements of the safety case and are adequate. Further details are provided below.

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

An SBI of the Essential Electrical System was carried out to judge the adequacy of the implementation of station arrangements to ensure that the system can perform its requisite safety function. In deciding if suitable and sufficient measures have been put in place for this safety system, these inspections consider compliance with a number of licence conditions to test the adequacy of the arrangements implemented. The standard consideration of LCs during SBIs include LCs 10, 23, 24, 27, 28 & 34, with some added or excluded depending on their applicability. In this case, LC34 that relates to leakage and escape of radioactive material and waste is not applicable to the Essential Electrical System and therefore has been deemed not applicable to the inspection.

During the course of this SBI it was found that NGL has adequately implemented their arrangements to ensure that the essential electrical supplies system is maintained and operated in accordance with the safety case  in  the areas sampled during the inspection. The inspection identified a number of areas for potential improvement, and although none gave rise to significant concern, the station has agreed to take action to address them.

In summary, the outcome from the safety inspection of the essential electrical supplies system is that the arrangements and their implementation are deemed to be adequate, and therefore we have given IIS ratings of 3 (adequate) in respect of LCs 10, 23, 24, 27 and 28.

A compliance inspection of LC12 was carried out at Sizewell B, to assess whether the arrangements and their implementation are considered to meet the requirements of the licence condition. During the inspection station confirmed that the main reference document identifying duly authorised persons (DAP) did not include all roles for which DAP authorisation is required. The implementation of the arrangements during the refuelling outage 13 was examined and it was concluded that station followed its process described in the role and training manuals required for authorisation of the DAPs referenced in the documents we inspected. In view of this we have rated this element of the inspection rating through the IIS as 3 (adequate).

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

Conclusion of Intervention

After considering all the evidence examined during the sample inspections undertaken against LCs 10, 23, 24, 27 and 28, we considered that the essential electrical systems met the requirements of the safety case.

From the information gathered and evidence obtained during this intervention, no matters have been identified that are likely to have significant impact on nuclear safety on the station at this time. Therefore we consider that no additional regulatory action arising from this visit is necessary currently, and the interventions for Sizewell B power station, set out in the Integrated Intervention Strategy, should continue to be implemented as planned.