- Site: Sellafield
- IR number: 21-114
- Date: October 2021
- LC numbers: 10, 23, 24, 27, 28, 34
Executive summary
Purpose of Intervention
In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Strategy, each year ONR performs a series of planned system based inspections (SBIs) targeted on key safety significant systems. The purpose of this particular inspection was to enable ONR to form a view on the adequacy of the Sellafield Electrical Distribution System in supporting the needs of the site’s security and resilience arrangements. This was demonstrated through the sampling of a representative set of security and safety claims.
On the 26th and 27th of October 2021, I carried out a planned two-day inspection of certain aspects of the Sellafield electrical distribution and security systems. I was assisted in this inspection by the ONR Site Infrastructure Inspector and an ONR Security Inspector.
In order to determine the adequacy of the licensee’s implementation of the safety and security case claims in respect of these systems, I examined evidence to verify the adequacy of the implementation of six pre-defined licence conditions (LCs), as listed below. These LCs have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for SBIs.
Interventions Carried Out by ONR
The inspection involved reviewing the applicable claims in the safety and security cases and then sampling suitable evidence to determine compliance against the selected LCs. This was achieved through a combination of document reviews, plant inspections and discussions with operators and maintenance staff.
I inspected compliance in the Stores against the following LCs by using the current versions of the applicable ONR inspection guidance documents:
- LC 10 – Training (NS-TAST-GD-027)
- LC 23 – Operating Rules (NS-INSP-GD-023)
- LC 24 – Operating Instructions (NS-INSP-GD-024)
- LC 27 – Safety Mechanisms, Devices and Circuits (NS-INSP-GD-027)
- LC 28 – Examination, Inspection, Maintenance and Testing (NS-INSP-GD-028)
- LC 34 – Leakage and Escape of Radioactive Material and Radioactive Waste (NS-INSP-GD-034)
Explanation of Judgement if Safety System Not Judged to be Adequate
The licensee demonstrated that the Safety Systems and Structures inspected as part of this SBI are able to fulfil their safety and security duties adequately, in line with the extant safety and security cases.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From my inspection I concluded that limits and conditions of operation for the Sellafield electrical distribution system were adequately specified and linked to the safety and security cases of the site’s nuclear facilities being served by the electrical utilities. Operational documentation was sampled which provided satisfactory evidence of compliance with these limits. I also concluded that procedures sampled provided appropriate instructions for the operation and maintenance of the relevant electrical equipment, including the backup electrical generators and the mobile diesel alternators. I found that Sellafield had implemented a maintenance programme for the equipment and equipment inspected was found to be in good condition and functioning correctly.
Overall I judged that arrangements for the management and operation of the Sellafield electrical distribution system 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 SBI as the system does not contain any radioactive material. 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, I consider that the Sellafield electrical distribution system adequately meets the claims in the relevant safety and security cases.
There are no findings from this inspection that could significantly undermine nuclear safety or security and resilience.