Executive summary
Date(s) of inspection
- July 2026
Aim of inspection
This inspection is targeted at a key hazard within Legacy Ponds, the D Bay Sludge. Removal of this sludge is directly linked to KDM M18 and the associated KPM is currently rated red.
Sludge removal currently relies on the commissioning of a new high performance pump system. This activity has suffered various delays and is still ongoing.
This inspection will allow ONR to test and gain confidence in the delivery of a key high hazard and risk reduction activity. It will also enable forward looking insights into the general commissioning capability in FGMSP, where KDM delivery relies on many new capabilities being brought on line in a timely manner.
This inspection will take place during the learning plan stage of the HPP commissioning process, prior to handover to operations.
Subject(s) of inspection
- LC21 - Commissioning - Rating: Green
Key findings, inspector's opinions and reasons for judgement made
The inspection examined Sellafield Ltd’s implementation of Licence Condition 21 commissioning arrangements for the High Performance Pump (HPP) installation in D Bay at the First Generation Magnox Storage Pond (FGMSP). The HPP is an important enabling system for D Bay sludge retrieval and associated hazard and risk reduction. D Bay is a concrete wet bay structure containing significant sludge inventory and mixed beta/gamma waste, with sludge arising from historical corrosion products and Rotary Skip Wash outlet material. Sellafield identified D Bay as a significant radiological hazard in the Separation Area, with high contact dose rates. Sellafield Ltd explained that previous sludge retrieval methods, including the eductor system installed in 2016, had delivered poor yield.
ONR sampled Sellafield’s commissioning governance, competence arrangements, technical decision-making, temporary commissioning aids, configuration control, operating instruction validation, and plant implementation through discussion, records review and a plant visit. Overall, ONR judged that Sellafield had established a structured commissioning approach for the HPP, including staged testing, review of commissioning documentation through the Commissioning Document Approval Committee (CDAC), escalation through commissioning and safety committees where appropriate, and close involvement of operations personnel. ONR was satisfied with the competence of the commissioning personnel sampled and noted beneficial co-location of operators and commissioning staff, which should support operational learning and handover.
ONR identified several matters for follow-up and advice. In particular, ONR asked questions about the basis for the claim that there are no nuclear safety functions associated with the HPP commissioning tests, including the role of associated relief valves, interlocks, low-level trips, overpressure protection, SCADA cut-outs and interfaces with supporting plant and pipework. Sellafield provided an explanation for its position, including that the HPP replaces the previous end effector and that relevant claims may sit elsewhere in the wider system. The site inspector will follow this up with Sellafield’s safety case team to confirm the position. ONR also advised Sellafield to formalise the terms of reference for the daily technical decision-making / learning plan meeting, and to improve the specificity of commissioning worksheet documentation, including pressure units and acceptance tolerances. ONR further noted that historical configuration knowledge issues had contributed to SCADA-related commissioning difficulties, reinforcing the importance of robust configuration control and knowledge management as the HPP progresses into the learning plan phase and eventual handover to operations.
Conclusion
Based on the evidence sampled, ONR judged that Sellafield has implemented a structured and generally effective commissioning process for the HPP at FGMSP, with staged testing, commissioning document approval, review of results, involvement of operations, SQEP commissioning personnel and escalation routes for faults and abnormal findings. ONR was satisfied with the competence of commissioning personnel sampled and noted positive features including operator involvement, use of offsite testing, and the staged approach to the learning plan. ONR also noted that the learning plan success criteria provide a clear basis for judging progression, while recognising that the first 25 batches will only provide an indicative assessment rather than a full demonstration of sustainable success.
ONR gave advice based on observations, including identified opportunities to strengthen technical decision-making governance, commissioning worksheet quality, configuration control, knowledge management, and tracking of actions arising from assurance processes.
ONR concluded that adequate LC21 arrangements were being implemented for the HPP commissioning activities sampled, and that it is therefore appropriate to rate this inspection GREEN.