Office for Nuclear Regulation

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SBI09 - Transformers, grid systems and main electrical systems

Executive summary

Purpose of Intervention

The primary focus of this intervention was a planned System Based Inspection (SBI) of the EDF Energy Nuclear Generation Ltd (EDF NGL) Hartlepool (HRA) power station transformers, grid systems and main electrical systems, which was undertaken as part of the planned intervention strategy for the Operating Facilities Division (OFD) of the Office for Nuclear Regulation (ONR).

The work was carried out by the ONR HRA Site Inspector, two ONR Electrical Inspectors and an ONR Organisational Capability Inspector, in line with the planned inspection programme contained in the HRA Integrated Intervention Strategy (IIS).

Interventions Carried Out by ONR

During this intervention we performed a SBI of the transformers, grid systems and main electrical systems to establish whether they are able to adequately fulfil their safety functional requirements in line with the safety case; the overall safety requirement of which is to ensure that electrical power is distributed to safety systems and plant under normal and abnormal operating conditions.

During this intervention ONR Inspectors examined EDF NGL’s compliance with the following nuclear site licence conditions (LCs) which are applicable provisions of the Energy Act 2013:

LC 34 (leakage and escape of radioactive materials) was not included in the SBI as it was judged by ONR that it was not applicable to this system. 

In addition, we undertook a progress review of ONR Regulatory Issue (RI) 5982 (Lightning Protection System; Level 4) and RI 5894 (Electrical Supplies to Fuel Oil Centrifuges; Level 3).

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

Not applicable.

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

During the course of this SBI, it was found that Hartlepool power station has arrangements to ensure that the transformers, grid systems, and main electrical system are inspected, maintained and, as necessary, operated in accordance with the safety case. The arrangements examined complied with the licensee’s legal duties 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. These observations were minor in nature and none were judged to be compliance issues, hence no regulatory follow-up is considered necessary.

In summary, the SBI of transformers, grid systems, and main electrical system, inspected for LCs 10, 23, 24, 27, and 28, is rated as Green on the basis that relevant good practice was met and any identified deficiencies in compliance arrangements were of minor significance. No intervention rating has been assigned to LC 34 as this LC was not deemed applicable to this SBI

The key findings by Licence Condition of our SBI of the transformers, grid systems and main electrical systems are:

In relation to Regulatory Issue (RI) 5982 (Lightning Protection System; Level 4) and RI 5894 (Electrical Supplies to Fuel Oil Centrifuges; Level 3), we were satisfied that adequate progress has been made by EDF NGL to resolve outstanding ONR concerns and recommended closure of both RIs.

Conclusion of Intervention

From the evidence sampled during this SBI against LCs 10, 23, 24, 27 and 28, we judged that the transformers, grid systems and main electrical systems fulfil their associated safety case requirements and therefore assigned inspection ratings of Green (no formal action).

We noted that the CRS control person authorisation training record for HV switching operations was a potential gap and this will be further investigated by the ONR Site Inspector through regulatory engagement with site.

We considered that progress made by EDF NGL in resolving RIs 5982 (Level 3) and 5894 (Level 4) is adequate for closure of both RIs.

A new RI (L4) was raised for EDF NGL to consider the status of the Liquid Neutral Earth Resistor (LNER) maintenance routine, with respect to the Maintenance Schedule and respond to ONR.

There were no findings from this intervention that could significantly undermine nuclear safety at HRA. At present, no additional regulatory action is needed over and above the planned interventions at HRA power station, as set out in the HRA IIS.