Office for Nuclear Regulation

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System Based Inspection (SBI) of Utilities (Electrical Distribution) (INF01) on Sellafield Ltd.’s nuclear licensed sites at Sellafield, Cumbria

Executive summary

Purpose of intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by ONR’s Sellafield Programme.  In accordance with that Strategy, a system based inspection (SBI) of the site electrical distribution system was planned and undertaken in February 2016.  The purpose of this inspection is for ONR to examine whether the licensee’s safety case claims in respect of this system important to safety have been adequately implemented.

This inspection activity targeted the site electrical distribution system. Although there is no direct nuclear hazard associated with this system (in that it does not directly confine nuclear matter), it provides a key support function to facilities on the licensed site which do confine such nuclear matter. Furthermore, these facilities make claims within their safety cases regarding the reliability of the electrical distribution system.  As such, the site electrical distribution system is a system important to nuclear safety.

ONR’s system based inspection process examines evidence to determine compliance against six key licence conditions (LCs). These licence conditions (listed below) have been selected in view of their relevance to ensuring nuclear safety and in providing a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

Interventions Carried Out by ONR

I carried out a system based inspection of the electrical distribution system over the course of three days. I was assisted by technical support from three specialist inspectors with expertise in the fields of Human Factors and Electrical Power Engineering. I was also supported on this inspection by SL staff from its internal regulatory organisation. The inspection comprised discussions with SL staff, physical viewing and inspections of targeted structures, systems and components, and reviews of SL’s records and other safety documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

The safety case supporting this system was judged to be implemented adequately.

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

From the areas I targeted and the evidence I examined during this inspection, I consider that SL has implemented adequately those safety case claims that relate to the site electrical distribution system. In particular, SL is developing and implementing some good arrangements for the provision of training of its staff, and has recently procured a switchboard training simulator.  As such I awarded IIS ratings of 3 (adequate) for LCs 10, 27, and 28 and a rating of 2 (good standard) for LC34.

However, we also identified two specific areas for improvement.  The first relates to the adequacy of the safety classification of the electrical distribution Telecontrol system, which we consider to be a system important to safety.  The second relates to the adequacy of SL’s present arrangements for reconnecting grid supplies following a loss of offsite power. These two findings led to me awarding IIS ratings of 4 (below standard) for LCs 23 and LC 24 and to raise two ONR Regulatory Issues in order to track SL’s progress in resolving these shortfalls

Conclusion of Intervention

 I consider that the licensee has a good knowledge of the physical condition of the structures, systems and components reviewed during this inspection and has in place appropriate management controls to ensure on-going safety.

I have, however, identified two specific areas for improvement, which require appropriate attention from the licensee. I have therefore raised two ONR Regulatory Issues.