- Site: Sellafield
- IR number: 21-130
- Date: November 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 for ONR to determine the adequacy of implementation of safety case claims for the nuclear ventilation system in the Central Lab (CL). The CL is operated by the National Nuclear Laboratory (NNL) as a tenant on the Sellafield site.
The primary objective of this inspection is to form a view on the adequacy of the implementation of the nuclear ventilation system safety case within the Central Lab (CL), and to gain assurance that the safety system fulfils its safety function.
Interventions Carried Out by ONR
On 10th and 11th November 2021, I carried out a planned two-day inspection of the Stores utilising two specialists from the following technical disciplines;
- Radiological Protection (RP)
- Fault Studies (FS)
In order to determine the adequacy of the licensee’s implementation of the safety case claims in respect of these systems, I examined evidence to verify the adequacy of the implementation of NNL’s arrangements for 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.
I inspected compliance in the CL 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)
- LC34 – Leakage and Escape of Radioactive Material and Radioactive Waste (NS-INSP-GD-034)
The inspection involved reviewing the applicable claims in the safety cases and then sampling suitable evidence to determine compliance against the selected LCs on the plant. This was achieved through a combination of document reviews, plant inspections and discussions with operators and maintenance staff.
Explanation of Judgement if Safety System Not Judged to be Adequate
This safety system is judged to be adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From the evidence sampled, I judged that SL had adequately implemented the safety case limits and conditions specified within the safety case. Furthermore, I was satisfied that the facility adequately understood the limits and conditions and their importance in the safety case.
From the compliance records sampled, I considered the facility had adequately complied with the operating rules, operating instructions and maintenance instructions. However, I noted some minor shortfalls in the operator round records and maintenance records, for which I provided regulatory advice.
Evidence was seen that suitable and sufficient safety mechanisms, devices and circuits are properly connected and in good working order.
Evidence was seen that NNL is subjecting the CL to an adequate level of Examination, Inspection, Maintenance and Testing (EIMT) by suitably trained personnel.
Overall, I found LCs 10, 23, 24, 27, 28 and 34 to be adequately implemented in relation to the nuclear ventilation system inspected. Consequently, it is my opinion that for this system based inspection a rating of GREEN - No formal action is appropriate for LCs 10, 23, 24, 27, 28 and 34.
Conclusion of Intervention
From the evidence sampled during the inspection, I judge that the CL has adequately implemented the nuclear ventilation safety case and followed the Sellafield Ltd arrangements for LCs 10, 23, 24, 27, 28 and 34. Overall, I judge that the nuclear ventilation system in the CL adequately fulfils the required safety function as claimed in the safety case.