Office for Nuclear Regulation

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System Based Inspection (SBI) of the Pile Fuel Storage Pond (PFSP) Electrical Systems at Sellafield

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, Decommissioning, Fuel and Waste Programme.  In accordance with that Strategy, a System Based Inspection (SBI) of the electrical system within the Pile Fuel Storage Pond (PFSP), its associated Local Sludge Treatment Plant (LSTP) and Drum Filling Plant (DFP) was planned and undertaken in July 2017. The purpose of this inspection was for ONR to examine whether the licensee’s safety case claims in respect of this system have been adequately implemented.

This inspection comprised an examination of the electrical systems within PFSP and its associated LSTP and DFP. The electrical systems are important to nuclear safety in that they provide power to equipment that may affect safety as well as providing power to systems required to deliver the hazard and risk reduction operations in PFSP.

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 this SBI over the course of two days. I was assisted by two ONR specialist inspectors with expertise in the field of electrical engineering and fault studies respectively. I was also supported on this inspection by SL staff from its internal regulatory group. 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

I judge the safety case supporting this system to be adequately implemented.

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

Based on the areas targeted and the related evidence examined during this inspection, I consider that SL has adequately implemented those safety case claims that relate to the Pile Fuel Storage Pond’s, associated Local Sludge Treatment Plant’s and Drum Filing Plant’s electrical systems. I found the SL personnel involved in the inspection were knowledgeable, professional and demonstrated good situational awareness throughout. I consider the general condition of electrical equipment and associated plant rooms to be adequate. However, I also identified several minor improvements that could be made.  These will be followed up during ONR’s future routine regulatory engagements. In my opinion, these do not detract from the overall inspection conclusions. As such, on balance, I award an inspection rating of Green (No Formal Action) for LCs 10, 23, 24, 27, 28 and 34.

In the course of this inspection there were no significant concerns identified with the adequacy of the licensee’s safety case for this system that would necessitate an earlier than planned assessment by ONR.

During the course of the inspection SL was unable to provide adequate evidence that the sampled staff had completed all their required training but committed to do so post inspection.  However, overall, I judge this shortfall to be minor.

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

I consider that the License has adequately implemented those safety case claims that relate to the PFSP, associated LSTP and DFP electrical systems, has a good understanding and control of the physical condition of the Structures, Systems and Components and has in place appropriate management controls to ensure on going safety.

I have, however, identified a number of minor areas for improvement. I have therefore raised a number of ONR Regulatory Issues at level 4 to track SL’s progress of these matters.

Overall, on balance, I consider the safety case supporting this system to be adequately implemented.