Office for Nuclear Regulation

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System Based Inspection (SBI) of Utilities Infrastructure Containment Systems (INF06) on Sellafield Ltd.'s nuclear licensed sites at Sellafield, Cumbria

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 ONR's Sellafield Programme. In accordance with that Strategy, a System Based Inspection (SBI) of the Utilities Infrastructure Containment System was planned and undertaken in July 2016. The purpose of this inspection is for ONR to examine whether the licensee's safety case claims in respect of this system important to safety have been adequately implemented.

This scope of this inspection activity comprised the Containment Systems under the control of the Infrastructure organisation. These comprise three Highly Active (HA) / Medium Active (MA) pipebridges under the jurisdiction of Utilities. Utilities are responsible for the secondary containment features associated with these pipebridges, although the primary containment remains the responsibility of the associated facilities (and is therefore outside the scope of this inspection). The scope of the inspection also covered the Low Active (LA) drain from the NNL Central Laboratory. These containment systems are important to nuclear safety as they confine radioactive substances. Their continued safe operation is also important to hazard and risk reduction across the site more generally. The scope of the inspection also included ducts and trenches across the site from a general condition perspective, noting that these contain important services and also form part of the site's water drainage arrangements. Both these aspects have an association with nuclear safety.

ONR's System Based Inspection 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.

Interventions Carried Out by ONR

I carried out this SBI of the Utilities Infrastructure Containment System over the course of three days. I was assisted by technical support from an external consultant with expertise in the field of mechanical engineering. I was also supported 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, and review of SL's records and other safety documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

I judge the safety case supporting this system 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 those safety case claims that relate to the Utilities Infrastructure Containment System. In particular, SL has undertaken a significant amount of intrusive maintenance and refurbishment work for the active pipebridges under the responsibility of Infrastructure in recent years, to ensure their continued safe operation. SL also has in place a detailed surveillance regime going forwards targeted at specific locations. As such I awarded inspection ratings of Green (No Formal Action) for LCs 10, 24, 28, and 34.

I have not awarded any rating for LC23 during this inspection. SL has not declared any Operating Rules for this system. I have nevertheless reviewed the limits and conditions SL is applying to control safety for this system, and my regulatory consideration is encompassed within my rating for LC24 above.

I have not awarded any rating for LC27 during this inspection, since I judged this licence condition was not sufficiently relevant to the system under consideration.

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.

During the course of the inspection SL was unable to provide adequate responses to my questions associated with the apparent hazard from a chemical tank above one of the pipebridges, and also associated with the lightning protection system for the pipebridges. Though I judge any shortfall here to likely prove to be modest, I have raised a Regulatory Issue to track SL's responses to my questions, which I will review in due course.

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 appropriate management controls in place to ensure on-going safety. A regulatory issue has however been raised to track SL's responses to questions of detail raised in the inspection.