- Site: Sellafield
- IR number: 21-118
- 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 at key safety significant systems. The purpose of this inspection was for ONR to determine the adequacy of implementation of Sellafield Limited’s safety case claims for the Special Nuclear Material’s (SNM) Sellafield Mixed Oxide Plant (SMP). SMP no longer produces Mixed Oxide (MOX) fuel but has special nuclear materials present. The inspection covered the storage of special nuclear material contained both within stores, and within the non-operational SMP itself. The scope focused on the ventilation systems. Effective ventilation of the stores and plant relates to the fundamental safety functions of cooling, containment and indirectly control (criticality).
On the 9 and 10 Nov 21, we carried out a planned two-day inspection of SMP. The ONR Site Inspector was supported by specialists from the following technical disciplines;
- Mechanical Engineering, and
- Electrical and Control and Instrumentation.
To determine the adequacy of the licensee’s implementation of the safety case claims in respect of these systems, we examined evidence to verify the adequacy of the implementation of Sellafield Ltd’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.
The inspection involved reviewing the applicable claims in the safety case 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.
Interventions Carried Out by ONR
We inspected compliance 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)
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
Evidence was seen that Sellafield Ltd is subjecting the ventilation systems to an adequate level of Examination, Inspection, Maintenance and Testing (EIMT), which is undertaken, controlled and supervised by suitably trained personnel. The evidence included completed EIMT records, training records, system health reports, and a physical walk down of accessible areas of the plant.
From the evidence sampled, I judged that Sellafield Ltd had adequately implemented the safety case limits and conditions specified within the safety case. The evidence included sampling of the audit trail from the safety case clearance certificates through to the operating and EIMT Instructions; completed operating rounds and surveillance sheets, and the control room log. From a combination of inspecting EIMT records and the plant walk down, evidence was seen that suitable and sufficient safety mechanisms, devices and circuits are properly connected and in good working order.
Evidence was seen that suitably trained Duly Authorised Persons (DAPs) had been appointed for the control and supervision of the operations. I saw sufficient evidence to be able to judge that the plant operators were suitably trained. SNM are in the process of improving their approach to identifying the minimum training requirements for operators and demonstrating this has been achieved. I have raised a Level 4 Regulatory Issue to oversee SNM’s plans for completing this work.
As is usual, some minor opportunities for improvement were identified during the inspection that resulted in regulatory advice, and SNM raising some condition reports in line with its internal processes. Overall, I found LCs 10, 23, 24, 27, 28 and 34 to be adequately implemented in relation to the systems inspected. Consequently, it is my opinion for this system based inspection that 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 SNM has adequately implemented the relevant claims in the safety case and that the formal arrangements for LCs 10, 23, 24, 27, 28 and 34 are being adequately implemented. Overall, I judge that the safety system adequately fulfils the requirements of the safety case.