- Site: Sellafield
- IR number: 21-138
- Date: December 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 Sellafield Ltd’s safety case claims for the ventilation and secondary off gas system for High Level Waste Plant (HLWP). These ventilation systems support the containment and cooling safety functions. The inspection scope excluded areas that are subject to major improvement projects (oversight for these projects is provided by an ONR Sellafield Project Inspector), and specified areas that have been subject to recent regulatory inspection or assessment.
Interventions Carried Out by ONR
On the 1st and 2nd December 2021, ONR and the Environment Agency carried out a joint planned two-day inspection of the HLWP vessel ventilation and secondary off gas systems on Waste Vitrification Plant (WVP) Lines 1 and 2 (L1&2). The inspection team was led by the ONR Site Inspector, an ONR Control and Instrumentation Specialist and an Environment Agency Site Inspector.
In order to determine the adequacy of the licensee’s implementation of the safety case claims in respect of these systems, ONR 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 cases and sampling 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.
I inspected compliance in the HLWP facilities against the following LCs by using the current versions of the applicable ONR inspection guidance documents:
- LC 10 – Training (NS-INSP-GD-010)
- 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
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 Sellafield Ltd has adequately implemented the requirements of the safety case for the inspected HLWP ventilation and secondary off gas systems, and I was satisfied that the facility understood the importance of these systems in the safety case.
Evidence was seen that Sellafield Ltd is subjecting the ventilation systems to an adequate level of Examination, Inspection, Maintenance and Testing (EIMT) undertaken, and controlled and supervised by suitably trained personnel. The evidence included completed EIMT records, training records, 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, to provide adequate containment of radioactive contamination. The evidence included sampling of the audit trail from the safety case clearance certificates through to the operating and EIMT Instructions. 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.
Whilst some minor opportunities for improvement were identified 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 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 judged that HLWP 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.