Office for Nuclear Regulation

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HALES C5 Vessel Ventilation - System Based Inspection (SBI)

Executive summary

Purpose of intervention

The purpose of this intervention was for the Office for Nuclear Regulation (ONR) to undertake a System Based Inspection (SBI) to confirm the adequacy of the safety claims made in respect of the C5 vessel ventilation system within the Highly Active Liquor Evaporation and Storage (HALES) facility at Sellafield.

This system was selected for inspection as it delivers a number of key safety functions within the HALES facility, and it is central to the management of hydrogen build-up within the HAST vessels, and to the control of Highly Active Liquor (HAL) temperature.

As part of this SBI, we also examined evidence of Sellafield Limited's (SL's) compliance with the following licence conditions (LCs):

Interventions Carried Out by ONR

We carried out a two-day, on-site team inspection, delivered by two ONR specialist inspectors and the ONR WEDD site inspector. SL's internal regulator was not involved in this inspection, but had recently completed a readiness review of the HALES ventilation system.

Explanation of Judgement if Safety System Not Judged to be Adequate

This Safety System was judged to be adequate.

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

We judged, from the evidence provided, that there is a clear link between the safety case for this system, and the operating documentation in use within the facility. We considered that training arrangements were adequately implemented, noting that the facility had identified some shortfalls in the scope of related training material.

The operating documentation (Rules and Instructions) were cross-referenced to and from the safety case, and we identified evidence of effective adherence to operation documentation on a number of separate occasions during our inspection. However, we identified that the Operating Rules inspected were not set out in a manner that supported operator control, and so placed an action on the licensee to address this shortfall, which we will track as a formal Issue. Nevertheless we considered that the supporting documentation provided sufficient operator guidance for safe management of the facility.

All sampled safety mechanisms were in good working order, were appropriately controlled and maintained, and were identified within relevant plant operating documentation, as well as being physically identified on plant, where appropriate. We noted that wider system component health had been identified as poor in some areas by SL's system health engineer, but that there is a programme in place to improve the material condition.

We judged that the plant areas inspected were being maintained to a good standard, and that plant husbandry and leak management approaches ensure that, should leaks occur, they would be quickly identified and rectified.

Conclusion of Intervention

The safety case for the HALES C5 vessel ventilation sub-system has been adequately implemented. With the exception of the specific shortfall in the use of Operating Rules, for which an ONR Issue has been raised, the arrangements for all related LC were judged to be adequately implemented.