Office for Nuclear Regulation

System Based Inspection (SBI) - Ventilation Systems for Special Nuclear Materials North (SNM(N))

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 systems for Special Nuclear Materials North (SNM(N)) facilities. 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 14th and 15th January 2020, ONR carried out a planned two day inspection of the SNM(N) ventilation system utilising specialists from the following technical disciplines:

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 SNM(N) facilities against the following LCs by using the current versions of the applicable ONR inspection guidance documents:

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 SNM(N) facilities ventilation systems, and I was satisfied that the facility understood the importance of these systems in the safety case.   

Sellafield Ltd has a number of processes in place for monitoring the condition of these systems, which are summarised in system health reports.  From my inspection, I considered that there was sufficient evidence that issues identified by the facility were being appropriately identified and acted upon. I reminded Sellafield Ltd of the importance of continuing to do this on a routine basis.   

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 SNM(N) 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.