Office for Nuclear Regulation

Highly Active Liquor Evaporation and Storage (HALES) facility – System Based Inspection (SBI) of the Cooling Water (CW) Automatic Isolation System (AIS)

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 Systems Based Inspection (SBI) of the HALES Automatic Isolation System (AIS) was planned for April 2015.  The purpose of this planned 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 all system based inspections, we examine evidence of the adequate implementation of six pre-defined 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.

ONR is currently undertaking an assessment of the licensee’s safety case covering future operation of Evaporator C within the HALES facility.  The areas for inspection were therefore also influenced by the need to gain evidence in support of this assessment.   

Interventions Carried Out by ONR

I carried out a two-day, on-site, system based inspection of the HALES AIS, with technical support from a Control and Instrumentation (C&I) specialist, and two Project inspectors from the ONR SL Programme.  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 AIS 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 AIS.  Additionally, the licensee is continuing to refine and develop more effective plant operating rules and limits, with a related benefit in terms of operator awareness and understanding. 

As part of the scope of this system based inspection, I have considered if the safety case that is the subject of this inspection might require an ONR assessment of adequacy in a timeframe shorter than normally planned.  Based on the information gathered during this SBI, I have no reason to recommend an early assessment of the safety case for this system.

Based on discussions with facility staff during this inspection, I consider that SL has adequate training in place to deliver an effective response to system alarms, from both a public and plant operator safety perspective.  There was evidence of a good awareness of plant parameters, the means of ascertaining them, and a reasonable level of wider understanding of which plant indications could be drawn upon with confidence in an emergency.

I did however identify a number of shortfalls in the effective delivery of maintenance for parts of the AIS in this inspection.  Given these shortfalls include a lack of adherence to formal procedures and the use of uncontrolled guidance, they give rise to wider concerns in regard to the adequate supervision of the maintenance team.

Conclusion of Intervention

From the evidence sampled during this inspection, I judge that the licensee has implemented adequately the relevant claims within its safety case, and that, with two exceptions, there was evidence that the formal arrangements for all the licence conditions against which I inspected are also being implemented adequately.

I have identified one area (spanning both LC24 and LC28) where there was evidence of significant shortfalls against compliance with the licensee’s own arrangements, against which SL has agreed to make improvements.  As such I have awarded an IIS rating of 4 (Below Standard) against LC24 (operating Instructions) and an IIS rating of 5 (Significantly Below Standard) against LC28 (Examination, inspection, maintenance and testing).  In view of these ratings I have raised an ONR Regulatory Issue in order to track SL’s progress in rectifying this shortfall.