Office for Nuclear Regulation

System Based Inspection of Sellafield MSSS Essential Services

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all interactions with the Sellafield Limited (SL) 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 Magnox Swarf Storage Silo (MSSS) Essential Services, have been adequately implemented.

This intervention was undertaken by an ONR inspection team comprising electrical engineering, C&I, mechanical and site inspection specialists.

Interventions Carried Out by ONR

On the 29th to 31st October 2019 I performed a planned safety case informed system based inspection (SBI) of the MSSS Essential Services to judge performance against safety functional requirements. Through sampled examination of the arrangements made for the MSSS Essential Services, 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 Structures, Systems and Components (SSC) inspected as part of the MSSS Essential Services 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

I concluded that limits and conditions of operation for the MSSS Essential Services were adequately specified and linked to the facility safety case.  Operational documentation sampled provided satisfactory evidence of compliance with these limits.  I concluded that procedures sampled provided appropriate instructions for the operation and testing of the relevant equipment.  I found that Sellafield had developed and implemented a comprehensive maintenance programme for the MSSS Essential Services equipment and that the condition of the plant items examined was considered adequate.

 In addition, I obtained evidence of the linkage between the MSSS Essential Services safety case and the Sellafield site electrical utilities safety case, including the permanent provision for the connection of mobile emergency generation.

Overall I judged that arrangements for management of the MSSS Essential Services 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.  Two Level 4 regulatory issues were raised during this SBI.

Conclusion of Intervention

From the evidence sampled during the inspection, I consider that the Sellafield MSSS Essential Services adequately meet 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.