Executive summary
Date(s) of inspection
- September 2026
Aim of inspection
The aim of the inspection is to verify that Sellafield Ltd. has taken sufficient measures to transition from upper tier to lower tier COMAH status.
Subject(s) of inspection
- COMAH - Control of Major Accident Hazards Regulations 2015 - Rating: Green
Key findings, inspector's opinions and reasons for judgement made
I conducted a Lower tier COMAH verification inspection at Sellafield Ltd. The inspection sought to examine the dutyholder's arrangements for moving from an upper tier COMAH site to a lower tier COMAH site. This is primarily by the dutyholder reducing their dangerous substance thresholds. The inspection was completed by the COMAH competent authority (CA), a collaborative approach between the Office for Nuclear Regulation (ONR) and the Environment Agency (EA).
A remote engagement was carried out in advance of the site inspection to take the opportunity to sample any key documentation. Areas sampled included:
- Changes to the major accident prevention policy
- Status of the extant COMAH safety report
- Management of change documentation
- Changes to the organisational management system
- Measures in place to ensure lower tier status is not breached
- Changes to consequence assessment
- Competency arrangements
- Changes to emergency arrangements and pollution prevention
The site intervention centered on the reduction and control of key dangerous substances that are either named or have the appropriate classification and labelling to be considered ‘COMAH substances.’
The areas of site sampled were:
- the inactive tank farm (ITF)
- the Salt Evaporation and Medium Active Storage (SEMAS)
- the Effluent Plant Services Building (EPSB)
- the Effluent Plant Maintenance Facility (EPMF)
- the Solvent Treatment Plant (STP)
- the Electrical Distribution Network Upgrade Project (EDNUP)
Regulatory judgement was based on determining compliance against COMAH 2015, including the associated guidance L111.
Conclusion
Based on the pre-inspection information and the site intervention, I judged that the arrangements for the reduction of dangerous substances (nitric acid) and the transition from Upper Tier COMAH to Lower Tier COMAH are adequate. The dutyholder was able to provide evidence of work completed and future activities to ensure they remain as a Lower Tier site for the foreseeable future.
Based on my sample, a rating of GREEN (no formal action) has been assigned to the inspection.