Office for Nuclear Regulation

System Based Inspection (SBI)

Executive summary

Purpose of Intervention

The purpose of this intervention was to conduct a remote system based inspection (SBI) of EDF Energy Nuclear Generation Ltd.’s (NGL’s) Torness Power Station specifically on the combined emergency generation, and short break supplies systems, no break systems, transformers, grid and main electrical systems that support the function of the gas circulators. This was undertaken as part of the planned intervention strategy for the operating facilities division (OFD) of Office for Nuclear Regulation (ONR).

The intervention was carried out, remotely, by a team consisting of electrical specialist inspectors, an external hazard specialist inspector, a fault analysis inspector, a quality and supply chain specialist inspector and supported by ONR’s Torness site inspector.

The intervention was carried out remotely due to ONR requirements 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.

Interventions Carried Out by ONR

The ONR inspection team performed a remote safety case informed SBI of the combined emergency generation, and short break supplies systems, no break systems, transformers, grid and main electrical systems to judge the systems’ performance against their safety functions. A function of these systems is to provide the infrastructure for electricity supply to Torness gas circulators under normal operations and in the event of an electrical supply interruption or a grid derived disturbance. At Torness there are redundant and diverse electricity supplies to the gas circulators for these purposes. The redundant and diverse electricity supplies are achieved through (i) the transformers, grid and main electrical systems and (ii) in the event of an electrical supply interruption or a grid derived disturbance system through the emergency generation, short break supplies and no break systems. Through remote examination of these systems, compliance inspections were performed against the following Licence Conditions (LC) which are provisions of the Energy Act 2013:

The remote inspections were based on sampling the implementation of the licensee’s arrangements provided by EDF NGL against the LCs. The objective of the remote inspection 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 remote inspection, I judged that the implementation of the arrangements for the combined electrical systems that support the function of the gas circulator main motors met the requirements of the safety case and was adequate.