Office for Nuclear Regulation

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System Based Inspection of Sellafield Emergency Generation System

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all interactions with the Sellafield licensed site against ONR's Sellafield, Decommissioning Fuel and Waste (SDFW) strategy for 2019/20.

The purpose of this intervention was to conduct a system based inspection (SBI) to examine whether the licensee's safety case claims, in respect of the Sellafield emergency power generation system, have been adequately implemented.

This intervention was undertaken by an ONR inspection team comprising electrical engineering, chemistry and site inspection specialists.

To promote regulatory efficiency and co-operation, the Environment Agency (EA) was made aware of this inspection and invited to take part.

Interventions Carried Out by ONR

On the 4th and 5th June 2019 ONR performed a planned safety case informed system based inspection (SBI) of the Sellafield emergency generation system to judge its performance against its safety functional requirements. Through sampled examination of the arrangements made for the emergency generation system, ONR inspectors performed compliance inspections against the following Licence Conditions (LC), which are applicable provisions of the Energy Act 2013:

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

The licensee demonstrated that the Safety Systems and Structures inspected as part of the Sellafield emergency generation system are able to fulfil their safety duties (safety functional requirements) adequately, in line with the extant safety case.

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

ONR concluded that limits and conditions of operation for the Sellafield emergency generation system were adequately specified and linked to the safety cases of the site’s nuclear facilities being served by the electrical utilities.  Operational documentation sampled provided satisfactory evidence of compliance with these limits.  ONR concluded that procedures sampled provided appropriate instructions for the operation and testing of the relevant electrical equipment, including the backup electrical generators and the mobile diesel alternators.  ONR found that Sellafield had developed and implemented a comprehensive maintenance programme for the equipment and that there had been improvements in reducing overdue maintenance.

In addition I obtained evidence that the electrical utilities safety case and its implementation had developed considerably since ONR’s previous SBI on the emergency generation system.  These were judged to be adequate.

Overall ONR judged that arrangements for management of the Sellafield emergency generation system broadly  met relevant good practice and awarded an intervention rating of Green (No formal action required) in relation to compliance with LCs 10, 23, 24, 27, and 28. No judgement was made regarding to compliance with LC 34 as this was not judged to be relevant for this system.  Advice was given in respect of opportunities for further improvement to minor compliance shortfalls.  These matters will be followed-up via routine regulatory engagement.  One regulatory issue at Level 4  was raised during this SBI.

Conclusion of Intervention

From the evidence sampled during the inspection, ONR considers that the Sellafield emergency generation system adequately meets the claims in the relevant safety cases.

There are no findings from this inspection that could significantly undermine nuclear safety.  No additional regulatory action is needed over and above the planned Sellafield interventions as set out in ONR’s Integrated Intervention Strategy.