Office for Nuclear Regulation

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Sellafield PF&S OU (PP1) - System Based Inspection - PMF(N) Ventilation System

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all regulator interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by the ONR Sellafield, Decommissioning, Fuel and Waste Division. The inspection plan PP1 for the Plutonium Finishing and Storage facilities Operating Unit (PF&S OU) details a strategic programme of regulatory inspections which includes a System Based Inspection (SBI) of the Ventilation System in PMF(N).

The purpose of this inspection is for ONR to examine whether the licensee's safety case claims in respect of the PMF(N) ventilation system have been adequately implemented. The ventilation systems in the PMF(N) stores are responsible for providing a flow of cooling air to remove the decay heat generated by the material contained in the stores. The ventilation systems also contribute to confinement of radioactive substances.

ONR's SBI process examines evidence to determine compliance against six licence conditions (LC). 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 conducted a System Based Inspection of the Store X and Store X extension ventilation systems in PMF(N) over the course of two days. I was assisted by the ONR Nominated Site Inspector and an ONR Mechanical Engineering Specialist Inspector. The inspection comprised discussions with SL staff, physical viewing and inspection of targeted structures, systems and components (SSC) through a plant walk-down and examination of a sample of operational documents and records. The inspections were carried out in accordance the following ONR inspection guidance:

Explanation of Judgement if Safety System Not Judged to be Adequate

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

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 adequately implemented the safety case claims which relate to the Store X and Store X extension ventilation systems.

I judge that the facility's implementation of the site's arrangements for the six Licence Conditions is good in many areas. For example, the staff interviewed had a good knowledge of the existing arrangements and the state of the plant and equipment provided good evidence to this effect.

I took confidence from the improvements SL has made to the ventilation systems, and the use of system health reports produced by the Ventilation Technical Support Group (VTSG).

In the course of my inspection I did not identify any significant concerns with the adequacy of the licensee's safety case for this system that would necessitate an earlier than planned assessment by ONR.

Conclusion of Intervention

My inspection outcome was shared and accepted by the licensee as part of normal inspection feedback.

I concluded that the PMF(N) Store X and Store X extension ventilation systems meet the requirements specified in SL's safety case and it is my opinion that an inspection rating of Green is appropriate for compliance against the Licence Conditions 10, 23, 24, 27, 28 and 34.