Office for Nuclear Regulation

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PF&S (PP1) - System Based Inspection (SBI) of the Leakage Detection System in PMF (N)

Executive summary

Purpose of intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by the ONR Sellafield, Decommissioning, Fuel and Waste Programme. The inspection plan PP1 for the plutonium finishing and storage facilities (PF&S) details a strategic programme of regulatory inspections which includes a System Based Inspection (SBI) of the leakage detection system in the site's plutonium management facilities (north) buildings.

The purpose of this inspection was for the ONR to determine the adequacy of implementation of the safety case made for the Plutonium Leak Detection System. This system is responsible for detecting any leakage of plutonium from the plant into a glove box or into the cell areas outside of the glove boxes before sufficient material can collect to cause a criticality incident. The protection systems that guard against this are therefore important to nuclear safety.

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

Interventions Carried Out by ONR

I carried out a SBI of the leak detection system over the course of two days. I was assisted by another ONR site inspector. I was also accompanied on this inspection by SL staff from its internal regulatory organisation. The inspection comprised discussions with SL staff, physical viewing and inspections of targeted structures, systems and components (SSC's), and reviews of SL's records and other safety documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

The safety case supporting this system was judged to be implemented adequately.

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

From the areas I targeted and the evidence I examined during this inspection, I consider that SL has implemented adequately those safety case claims that relate to the leak detection system. In particular, it is my opinion that SL is developing and implementing some good arrangements for the provision of training to its operational staff in leak detection. SL has also taken a proactive engineering approach to leak detection on this plant. Consequently, it is my opinion that an inspection rating of Green (no formal action) is appropriate for compliance against LCs 10, 23, 24, 27, 28 and 34.

Conclusion of Intervention

I consider that the licensee demonstrated 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 concluded that the leak detection system meets the requirements specified for it in SL's safety case and that no early assessment by ONR of the adequacy of this safety case (ahead of when planned as a routine activity) is needed.

I also took the opportunity to sample evidence relating to the completion of a test procedure which SL has developed in response to an ONR Regulatory Issue relating to the detection of chronic leaks. Based on the evidence seen, I will be recommending that this Regulatory Issue should now be closed.