Office for Nuclear Regulation

System Based Inspection on Ventilation system and Separation Area Vent Link

Executive summary

Purpose of Intervention

This intervention, conducted at the Licensee’s Sellafield Limited (SL) Cumbria licensed site, was undertaken as part of the 2019/20 intervention plan and the Sellafield sub-division strategy.

Interventions Carried Out by ONR

ONR conducted a System Based Inspection (SBI) of the cell and vessel ventilation (including the link to Separation Area Ventilation (SAV)) system associated with Magnox Reprocessing Facility (MRF). The scope of this inspection considered the operation and maintenance of the ventilation system to abate radioactive discharges and maintain nuclear safety. The delivery of this function is important to maintain safety for MRF and for high hazard and risk reduction operations more generally.

ONR’s SBI process examines evidence to determine compliance against six licence conditions (LCs). These licence conditions (listed below) have been selected in view of their relevance to ensuring nuclear safety and in providing a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

LC 10 requires SL to make and implement adequate arrangements for suitable training of those who have responsibility for any operations that may affect safety.

LC 23 requires SL to produce adequate safety cases to demonstrate the safety of its operations, and to identify the operating conditions and limits necessary in the interests of safety.

LC 24 requires SL to make and implement adequate arrangements for the provision of suitable written instructions for undertaking any operation that may affect safety.

LC 27 requires SL to ensure that, before a system is operated, inspected, maintained or tested, there are suitable and sufficient safety mechanisms, devices and circuits properly connected and in good working order.

LC 28 requires SL to make and implement adequate arrangements for the regular and systematic examination, inspection, maintenance and testing of all plant which may affect safety.

LC 34 requires SL to ensure that its radioactive material and radioactive waste is at all times adequately controlled and contained, and that no leak or escape of that material or waste can take place without being detected.

Explanation of Judgement if Safety System Not Judged to be Adequate

The Licensee has demonstrated that the Structures, Systems and Components (SSCs) which have been inspected as part of the MRF cell and vessel ventilation system are able to fulfil their safety function requirements adequately, in line with the safety case.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

From the areas ONR targeted and the evidence ONR examined during this inspection, I consider that SL has adequately implemented those safety case claims that relate to the MRF cell and vessel ventilation systems. I identified minor shortfalls in relation to LC 34 and LC 28. I raised these as ONR Level 4 Regulatory Issues. I awarded inspection ratings of Green (No formal action) for LCs 10, 23, 24, 27, 28 and 34.

Conclusion of Intervention

I consider that the licensee has a good knowledge of the physical condition of the Structures, Systems and Components reviewed during this inspection and has in place appropriate management controls to ensure on-going safety.

I identified some findings for which I have raised two ONR Regulatory Issues at Level 4 to track SL’s progress of these matters.

Overall, I consider the safety case supporting this system to be adequately implemented.