Office for Nuclear Regulation

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Sellafield PMF(S) FL6 Control System Systems Inspection

Executive summary

Purpose of intervention

The intervention was undertaken in the Thorp Finishing Line 6 (FL6) facility to assess the adequacy of the FL6 control and instrumentation system.

Interventions Carried Out by ONR

This was a system-based inspection undertaken against the licence conditions listed in Table A above, incorporating:

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

The key findings from the intervention are as follows, broken down by Licence Condition:

LC 10 Training: Rating 3 (Adequate)

Overall the procedural training arrangements were good, however personnel on the plant were not aware of the difference between Safety Related Equipment (SRE) and Safety Mechanism (SM) designated equipment nor of the importance of performing independent checks of alarms rather than relying on the Distributed Control System (DCS).

LC 23 Operating Rules: Rating N/A

Not inspected. There were no readily identifiable operating rules that applied specifically to the control and operating system.

LC 24 Procedures: Rating 4 (Below Standard)

Training and SQEP (Suitably Qualified and Experienced Personnel) procedures were good. However, plant operational procedures were being updated and at the time of the inspection the production of the alarm response sheets had not been completed, and the operator instructions were not readily accessible in the control room.

LC 27 Safety Mechanisms, Devices and Circuits: Rating 4 (Below Standard)

Some additional basket safety measures identified as lesser safety significance shortfalls in the LTPR (Long Term Periodic Review) have not yet been implemented. There is also an outstanding issue from the LTPR regarding the need to improve the quality of the protection arrangements for the return of CML (Condensate Mother Liquor) to THORP, in order to control the risk of a criticality in this area. This issue does not appear to be progressing due to a lack of clear ownership of the issue between THORP and FL6.

LC 28 Maintenance: Rating 4 (Below Standard)

An appropriate management re-organisation has been implemented to improve the maintenance performance and especially the backlog reduction. However no adjustment has been made to the periodicity and frequency of outages as was discussed at the previous inspection and the current re-start following outage has increased the backlog levels significantly. The levels of routine and breakdown maintenance backlog remain at an elevated level.

LC34 Leakage and containment of radioactive matter: Rating 3 (Adequate)

Appropriate arrangements are in place for identifying loss of containment and identifying the potential spread of contamination.

Conclusion of Intervention

As inspected, the FL6 control and instrumentation system was functional and fit for purpose. Several issues relating to fault response and operator training are recognised by the licensee and are being worked on. The issue regarding the provision of adequate mitigation measures for the return of CML needs to be progressed. These and other lower level matters raised in this report will be followed up as routine regulatory business.