Office for Nuclear Regulation

Inspection of Electrical related aspects - SBI 07,  SBI 08 and SBI 09

Executive summary

Purpose of Intervention

The purpose of this intervention was to conduct a series of inspections at EDF Energy Nuclear Generation Ltd.’s (EDF Energy NGL’s) Heysham 1 Power Station which covers the electrical engineering activities being undertaken on plant and equipment as part of the ongoing Reactor 1 statutory outage. The inspections were undertaken as part of the planned intervention strategy for the operating facilities division of Office for Nuclear Regulation (ONR).

This intervention record considers the key findings, inspectors’ opinions and judgements made during a series of electrical engineering inspections made over the Reactor 1 statutory outage period; bringing them together to cumulatively record the significant findings, overall judgements, conclusions and inspection ratings from the relevant electrical engineering inspections.

Interventions Carried Out by ONR

The inspections covered a sample of the electrical engineering plant and equipment that form the Reactor 1: short break supplies system; no break system; transformers, grid and main electrical system; and emergency generation system. Hereinafter these systems will be referred to as the electrical systems.

The inspections were undertaken by ONR’s Operating Reactors electrical specialist inspectors, supported by ONR’s Heysham 1 Reactor 1 Statutory Outage project inspector. The ONR inspection team performed a series of inspections of the Heysham 1 electrical systems.  These inspections were used to judge the electrical systems’ performance against their safety functions and the adequacy of maintenance activities completed during the Reactor 1statutory outage.

The inspections were carried out remotely due to ONR arrangements that have been developed in order to comply with the restrictions imposed by Her Majesty’s Government (HMG) in response to the 2020 COVID-19 pandemic. Site-based facility walk-downs were undertaken by EDF NGL’s independent nuclear assurance function to inform my judgements.

Through remote examination of the electrical systems, an assessment of adequacy was made on: the safety case functional requirements and how they were being fulfilled; the configuration of the systems; and compliance with the Licence Conditions (LC) that form a systems based inspection and which are provisions of the Energy Act 2013:

The inspections were based on sampling the implementation of the licensee’s arrangements against the LCs and their outage intentions documentation.  The objective of the inspections was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements.

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 inspections carried out, I judged that the implementation of the arrangements for the statutory outage and the electrical systems sampled met the requirements of the safety case and were adequate.

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

From this intervention, I consider that EDF Energy NGL demonstrated that they have arrangements to ensure that the electrical systems sampled are inspected, maintained and operated in accordance with the safety case.  In my opinion, the arrangements examined complied with the licensee’s legal duties on the areas sampled during the inspection.  The inspections did identify a number of areas for potential improvement, and although judged that none gave rise to significant concern, relevant EDF Energy NGL staff have agreed to take action to address them.

The inspections of the electrical systems inspected for compliance with the arrangements for LCs 10, 23, 24, 27, and 28, were rated as ‘green’ on the basis that relevant good practice was met and any identified deficiencies in compliance arrangements were of minor significance.

Conclusion of Intervention

From the evidence sampled during the inspections, I consider that the Heysham 1 electrical systems and their associated arrangements are in line with regulatory expectations for LCs 10, 23, 24, 27, and 28.  Further, I consider that the aspects of the electrical systems sampled as part of this intervention met the requirements of the safety case.

In relation to the electrical engineering aspects associated with the Reactor 1 statutory outage there were no current issues that have been identified from the sample of the work thus far that should affect the return to service of Reactor 1, subject to the completion of the planned and emergent work.  There were no findings from these inspections that I viewed could significantly undermine nuclear safety.