Office for Nuclear Regulation

Analytical Services nuclear ventilation system

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 Programme.

In accordance with that Strategy, a system based inspection of the Analytical Services (AS) ventilation system was planned for March 2015.  The purpose of this inspection was for the ONR to confirm the adequacy of implementation of the licensee’s safety case claims in respect of this system.

As part of our system based inspections, we examine evidence of the adequate implementation of six licence conditions.  These licence conditions (listed below) have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for system based inspection.

Interventions Carried Out by ONR

I carried out a two-day, on-site, system based inspection of the ventilation system within AS, with technical support from a Control and Instrumentation (C&I) specialist.  The inspection comprised discussions with SL staff, a plant walk down and reviews of plant records and other documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

The ventilation system was judged to be adequate.

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

From the evidence made available to me during this inspection, I consider that SL has implemented adequately those claims within the facility safety case that relate to the ventilation system.

In terms of management of the system’s physical condition, I consider that SL is working to improve its understanding of the system health, and has improved its control and delivery of maintenance and inspection over the last 18 months.  This was particularly evident during the plant walk down.  There is also some evidence that SL has started to develop a proactive approach to asset care for this system. Nevertheless, I consider that SL still has work to undertake before it has a full understanding of asset condition within the ventilation system, but I note the planned and funded programme of improvements which gives me confidence that this will be achieved.

Based on discussions with facility staff during this inspection, I consider that SL has a reasonable understanding of the underlying causes of events that are experienced within the ventilation system, and that on the whole, it has used this understanding to direct where to prioritise remedial work within the facility.

I identified that a key safety claim on the ventilation system is based on operator response to loss of facility ventilation.  The relevant safety case claim focuses on the ability of the facility to cease operations and evacuate the building in a timely manner, should the ventilation system not be available.  During this inspection, I identified evidence that the protocol driving that evacuation decision was not always clearly understood, and that the operational monitoring supporting that decision is not clear and consistent.  I have raised a Regulatory Issue to track SL’s progress in addressing this shortfall.  

I also identified a number of areas of good practice within this inspection, notably within the provision of arrangements for the identification and control of radioactive leakage and escape from the system, where effective trending and a challenging checking culture are embedded.  These areas of good practice have, consequentially, attracted higher IIS ratings.  

Conclusion of Intervention

From the evidence sampled during this inspection, I judge that the licensee has implemented adequately the relevant claims within the safety case, and that, with one exception, there was evidence that the formal arrangements for all the licence conditions I inspected against were also implemented adequately.

I have however identified one area (LC24) where SL has agreed to make improvements.  I have raised an ONR Regulatory Issue in order to track SL’s progress in this regard.