Office for Nuclear Regulation

Sellafield - High Level Waste Plant - Waste Vitrification Plant - Lines 1 and 2 - Containment System

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 system inspected; the containment system within the Waste Vitrification Plant (WVP). The scope of this inspection was confined to Lines 1 + 2 of the WVP only, Line 3 was in a forced outage following a contamination event in November 2013.

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

ONR carried out a two-day, on-site team inspection, delivered by three ONR specialist inspectors and the ONR site inspector. Members of Sellafield Limited's internal regulator function were also involved in the inspection.

Explanation of Judgement if Safety System Not Judged to be Adequate


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

The inspection team reviewed the system planned for inspection; containment, and decided that containment of Highly Active Liquor (HAL), the most significant hazard on the plant, should be the focus of the inspection.

Given the adequacy of the documentation reviewed, and the clear links between claims made within the safety case, and the documentation in use by the plant operators, I consider that the safety case implementation is sufficient, and shows a clear line between higher claim and facility operation in normal and fault condition. Therefore, within the system boundary specified by this inspection, and noting that the evidence is extracted from a sample-based approach to inspection, the WVP containment safety case is considered adequately implemented.

I have identified an issue with the management of temporary Plant Modification Proposals (PMP) within the sample examined; the issue is manifest as a lack of training and awareness. Given that the sampled evidence includes this finding, I consider that an IIS rating of 4 (below standard) against Licence Condition 10 is appropriate. Additionally, I consider it appropriate that the licensee should review all extant temporary PMPs within WVP to confirm if these findings exist elsewhere. I have raised an Issue (Level 4) to monitor completion of this action.

Sellafield Limited presented an overview of WVP operations, and associated operating rules, covering surveillance monitoring, operator rounds, and alarm management and operator instructions. This provided a clear overall picture with no obvious defects, and I consider that an IIS rating of 3 (adequate) against Licence Condition 23 is appropriate.

We judged that the scope and content of sampled operating instructions were adequate, and of a quality expected for the management of HAL. On this basis, I consider that an IIS rating of 3 (adequate) against Licence Condition 24 is appropriate.

Based on inadequate evidence in support of the maintenance status of the sampled safety mechanisms, together with the status of the claimed temperature alarm, I consider that an IIS rating of 4 (below standard) against Licence Condition 27 is appropriate. As part of the quarterly regulatory engagement forum for WVP, the licensee presents a summary of maintenance issues that are being activity resolved. I believe that it would be proportionate to expect that the licensee actively manages the issues identified within that forum, and do not consider it appropriate to raise a regulatory Issue at this time.

I consider that the maintenance evidence, as sampled, shows a complete documentation trail for completed maintenance, as defined in the PMS or equivalent. I note that the basis on which the non-maintainable status of one Safety Mechanism (SM) is presented is less than adequate; this issue is addressed within my judgement of LC27 compliance. Given that all required maintenance has been completed as required and recorded effectively (given the administrative error identified above has already been addressed), I consider that an IIS rating of 3 (adequate) against Licence Condition 28 is appropriate.

I (the site inspector) consider that the evidence of containment function and performance, as sampled, indicates an adequate confinement performance, given that evidence captured in support of other LC (specifically against Control & Instrumentation (C&I) shortcomings) will be addressed under a formal Issue or at the next Level 4 regulatory engagement meeting. Given the confidence gained within the civil engineering inspection activities, I consider that an IIS rating of 3 (adequate) against Licence Condition 34 is appropriate.

Conclusion of Intervention

Overall, based only on the sampling undertaken, I consider that Sellafield Limited has demonstrated that it has a suitable safety case, adequately implemented for the containment of HAL within the WVP facility.