Executive summary
Date(s) of inspection
- December 2025
Aim of inspection
In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Strategy, each year ONR performs a series of planned inspections to seek assurance of compliance against selected licence conditions, targeted at those facilities with significant importance to nuclear safety. One such inspection was undertaken at Special Nuclear Materials Value Stream North facilities (SNM (N)) within the Sellafield site in West Cumbria to sample evidence of implementation of Sellafield Limited's arrangements for compliance with Licence Condition (LC) 23 (Operating rules), 24 (Operating instructions), 27 (Safety mechanisms, devices and circuits), 28 (Examination, inspection, maintenance and testing) and 34 (Leakage and escape of radioactive material and radioactive waste) specifically to FL4 mechanical and control and instrumentation systems, in order to inform a regulatory judgement regarding the licensee’s compliance with its legal duties under the nuclear site licence.
Subject(s) of inspection
- LC23 - Operating rules - Rating: GREEN
- LC24 - Operating instructions - Rating: GREEN
- LC27 - Safety mechanisms, devices and circuits - Rating: GREEN
- LC28 - Examination, inspection, maintenance and testing - Rating: GREEN
- LC34 - Leakage and escape of radioactive material and radioactive waste - Rating: GREEN
Key findings, inspector's opinions and reasons for judgement made
The inspection was undertaken on 3 and 4 December 2025 by the SNM site inspector, a mechanical engineering specialist inspector, a control and instrumentation specialist inspector and a safeguards inspector. The inspection was also attended by a developing internal hazards specialist inspector.
The inspection targeted compliance against Licence Condition (LC) 23 (Operating rules), 24 (Operating instructions), 27 (Safety mechanisms, devices and circuits), 28 (Examination, inspection, maintenance and testing) and 34 (Leakage and escape of radioactive material and radioactive waste) specifically to Finishing Line 4 (FL4) mechanical and control and instrumentation systems. The inspection also targeted compliance against The Nuclear Safeguards (EU Exit) Regulations 2019 (NSR19). This inspection record captures evidence pertinent to LC23, 24, 27, 28 and LC34 compliance, whereas evidence relevant to NSR19 is in IR-53947.
The inspection involved a planning phase and a site visit, which included discussions with relevant Sellafield Limited personnel, review of records, sampling of information contained within electronic databases and other documentation, and a plant walkdown.
From a mixture of sampling records and discussions with Sellafield Limited personnel, I concluded the following:
No significant matters were identified that required immediate regulatory attention.
For LC23, I was satisfied that Sellafield Limited have adequately implemented the safety case and have identified suitable limits and conditions in relation to FL4 mechanical and control and instrumentation systems.
For LC24, I was satisfied that Sellafield Limited have suitable operating instructions in place and appropriately used.
For LC27, I was satisfied that key Safety Mechanisms, Devices and Circuits (SMDC) had been identified in the safety case, in relation to FL4 mechanical and control and instrumentation systems, and those sampled could be located on plant and were properly connected and in good working order to deliver the safety function. One Level 4 (i.e. lowest level) Regulatory Issue raised to allow ONR to monitor progress in addressing the identified minor shortfall relevant to alignment of the Engineering Schedule (ES) with the Clearance Certificates (CC), Maintenance Instructions (MI), and plant maintenance schedules (see RI-12850 Action 1).
For LC28, I was, overall, satisfied that examination, inspection, maintenance and testing of those SMDCs sampled have being undertaken in an appropriate and timely manner. I identified, however, the following anomalies:
- No inspection of the overpack filters has been undertaken as stated in the Technical Basis of Maintenance (TBoM). This was recognised as a gap by the licensee and provided me with assurance that the system will continue to provide its function. I raised one Level 4 Regulatory Issue to monitor the review and update of the TBoM, development of a MI for the filter inspection, and update the plant maintenance schedule (see RI-12850 Action 2).
- The System Health Report for FL4 has been outdated and a number of actions are outstanding. The report highlighted a cracked window in addition to the window visibility being degraded. Sellafield Limited believe that the current facility will not support a full second round of repack. Sellafield Limited provided me with assurance that window visibility is reviewed continuously and a more rigorous housekeeping is in place. I raised a Level 4 Regulatory Issue to review and approve all outstanding actions in the System Health Report (see RI-12851).
For LC34, I was satisfied with the SMDSs in place, including their maintenance, in demonstrating compliance against leakage and escape of radioactive material and waste.
Conclusion
On the basis of the evidence sampled at the time of the inspection, I found that SNM North is compliant with the licensee’s corporate arrangements for LC23, 24, 27, 28 and 34 specifically to FL4 mechanical and control and instrumentation systems.
Taking all of the above into account, and noting the ONR guidance on inspection ratings, it is my opinion that, on balance, an inspection rating of Green (i.e. no formal action) for Licence Condition 23, 24, 27, 28 and 34 is merited here.