Office for Nuclear Regulation

Sellafield Ltd. Nuclear licensed site - System Based Inspection of PFCS Ventilation System 

Executive summary

Purpose of Intervention

This intervention, conducted at the Licensee’s Sellafield Limited (SL) Cumbria licensed site, was undertaken as part of the 2018/19 intervention plan and the Sellafield sub-division strategy.

Interventions Carried Out by ONR

ONR conducted a System Based Inspection (SBI) of the Pile Fuel Cladding Silo (PFCS) ventilation system (including argon supply). The scope of this inspection considered the operation, maintenance and structural integrity of the ventilation and argon inerting systems’ ability to abate radioactive discharges, prevent combustion and maintain nuclear safety. The delivery of this function is important to the safety of PFCS, and for high hazard and risk reduction operations more generally.

ONR’s SBI process examines evidence to determine compliance against six key 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.

LC10 requires SL to make and implement adequate arrangements for suitable training of those who have responsibility for any operations that may affect safety.

LC23 requires SL to produce an adequate safety cases to demonstrate the safety of its operations, and to identify and implement operating conditions and limits necessary in the interests of safety.

LC24 requires SL to make and implement adequate arrangements for the provision of suitable written instructions for undertaking any operation that may affect safety.

LC27 requires SL to ensure that, before a system is operated, inspected, maintained or tested, all safety mechanisms, devices and circuits are properly connected and in good working order.

LC28 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.

LC34 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 Pile Fuel Cladding Silo (PFCS) 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 PFCS Ventilation and Argon Inerting System. I did identify several minor improvements that could be made. On balance, I awarded inspection ratings of Green (No formal action) for LCs 10, 24, 27, 28 and 34.

I did however identify some more significant concerns in relation to LC23; in particular the management and implementation of safety cases not being appropriately controlled to ensure that the information provided by the safety case is current and visible to ensure compliance. On balance, I applied an inspection rating of Amber (Seek improvement) for LC 23 to reflect this. These shortfalls have been raised as a Regulatory Issue which will be managed as part of normal regulatory business.  

Conclusion of Intervention

No matters were identified as requiring immediate regulatory attention during the conduct of the system based inspection.

I have applied an inspection rating of Amber (Seek improvement) for LC 23.

I have applied an inspection rating of Green (No formal action) for LCs 10, 24, 27, 28 and 34.

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