Executive summary
Date(s) of inspection:
December 2025
Aim of inspection
Organisational learning (OL) is subject to enhanced regulatory attention at Sellafield Ltd, and learning from high potential events and precursors (HiPos) has been highlighted by ONR as a particular area of concern. This inspection aims to evaluate the adequacy of Sellafield Ltd’s OL response to HiPos occurring at the nuclear licensed site.
Subject(s) of inspection
- LC7 - Incidents on the site - Rating: Amber
- LC17 - Management systems - Rating: Amber
- Management of Health and Safety at Work Regulations - Rating: Amber
Key findings, inspector's opinions and reasons for judgement made
I, the Leadership and Management for Safety specialist inspector at the Sellafield Site in Cumbria who leads on the regulation of organisational learning (OL), supported by a Nuclear Safety site inspector, undertook a themed inspection with a focus on high potential events and their precursors (HiPos). The inspection covered Nuclear Site Licence Condition (LC) 7, LC17 and Regulation 5 of the Management of Health and Safety Regulations 1999 (MHSWR99).
The purpose of LC7 is to ensure that the licensee implements adequate arrangements for the notification, recording, investigation and reporting of incidents occurring on the site that are significant for nuclear safety. The purpose of LC17 is to ensure that the licensee establishes and implements management systems which give due priority to nuclear safety. The purpose MHSWR99 Regulation 5 is to ensure that the dutyholder implements arrangements for the effective planning, organisation, control, monitoring and review of the preventive and protective measures in place. The scope of MHSWR99 includes all health and safety, it is not restricted to nuclear safety.
The purpose of the intervention was to seek assurance that Sellafield Limited is: reliably identifying HiPos; appropriately sentencing them; and undertaking investigations that are adequate in terms of identifying root causes. A HiPo is an incident or near miss that, while not resulting in actual harm or significant consequences, had the potential, under slightly different circumstances, to lead to a serious safety/operational impact. HiPos were targeted because on a licensed nuclear site, they are particularly important sources of OL as they can reveal latent weaknesses in systems, processes, or human performance that, if left unaddressed, could contribute to future events with more severe outcomes.
The inspection sampled four HiPo events, selected in most instances through a manual review of events over a defined period, three of which related to nuclear or radiological safety while the fourth related to a conventional safety event; of these, two were investigated, of which only one was investigated using a method suitable for identifying root causes. Neither investigation led to actions which targeted systemic, Enterprise-wide factors
LC7 - Incidents on the site
I found that Sellafield Limited does not have established arrangements for identifying HiPos for nuclear and radiological safety events, and that the recommendations concerning sentencing of condition reports (CRs) contained within Sellafield Limited's performance improvement arrangements are unworkable in practice, so deviation from them has been normalised. Therefore, I have concluded that the Sellafield Limited has deficient LC7 arrangements for compliance with legal requirements and I rate LC7 as Amber (Seek Improvement).
LC17 - Management Systems
I found no evidence that the OL arrangements are subject to line 1 assurance checks. Line 2 assurance checks do take place but these have not targeted the sentencing and investigation activities that are critical to ensuring that HiPos are identified and investigated, and that lessons are learned and shared. Line 1 and 2 assurance activities are a basic and essential element of quality management arrangements. Therefore, I have concluded that the Sellafield Limited has deficient LC17 arrangements for compliance with legal requirements and I rate LC17 as Amber (Seek Improvement).
Regulation 5 of MHSWR99 - Arrangements
Performance measurement, in particular investigation of accidents and incidents, is a vital part of the arrangements required to ensure that the preventive and protective measures in place for health and safety are effective. I found evidence that the shortfalls described above for LC7 and LC17 were not confined to nuclear or radiological safety. Sellafield Limited's arrangements for investigating accidents and incidents are not sufficient to identify the OL that may be associated with HiPos and realise the benefits in terms of improving overall risk management. Therefore, I have concluded that the Sellafield Limited has deficient arrangements for compliance with legal requirements associated with MHSWR99 Regulation 5 and I rate this as Amber (Seek Improvement).
Generally, I found that there is also a widespread misunderstanding amongst Sellafield Limited personnel of what the root cause of an incident is, which results in a failure to recognise when root causes of incidents have not been identified and further investigation is required, and failure to adequately explore systemic and Enterprise-wide factors when undertaking investigations and identifying remedial actions.
I did find evidence that the behaviours and skills of Sellafield's Site Sentencing Authority personnel, and the good relationship they have established with facilities, makes a positive contribution to Sellafield Ltd's PI arrangements.
Conclusion
I will consider the LC7, LC17 and MHSWR Regulation 5 deficiencies in the context of the wider Sellafield Limited activities and against ONR's Enforcement Guidance. Importantly, from the evidence I gathered, I am satisfied that these issues do not represent a material increase in risk to workers or the public at this time.