Executive summary
Date(s) of inspection:
June 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), 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 ventilation 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
- LC 23 - Operating rules - Rating: GREEN
- LC 27 - Safety mechanisms, devices and circuits - Rating: GREEN
- LC 28 - Examination, inspection, maintenance and testing - Rating: AMBER
- LC 34 - 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 between 11 and 12 June 2025 by the ONR’s site inspector for SNM and supported by one mechanical engineering specialist inspector, the SNM project inspector, one developing mechanical engineering inspector and one developing internal hazards specialist inspector.
The inspection involved a planning phase and a site visit, which comprised discussions with Sellafield Limited personnel, a review of a targeted sample of Sellafield Limited’s documentation, and a plant walkdown of the ventilation systems at SNM (N) facilities.
From a mixture of sampling records, discussions with Sellafield Limited personnel and a plant visit, 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 limits and conditions, as specified within the current safety cases, in relation to SNM (N) ventilation systems.
For LC27, I was satisfied that key Safety Mechanisms, Devices and Circuits (SMDC) had been identified in the safety case, 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 has been 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) and plant maintenance schedules (see RI-12616).
For LC28, whilst I was satisfied that examination, inspection, maintenance and testing of those SMDCs sampled have being undertaken in an appropriate and timely manner, I identified a number of shortfalls against the LC28 compliance expectations including:
The adequacy of the inspection and maintenance arrangements specifically to TBoM for the 22” duct.
The delivery of the requisite inspections and maintenance for the 22” duct, the B209 South plenum ductwork, the B299 vortex amplifiers and the B209 gloveboxes in-bleed filters replacement.
The condition of the B209 South plenum which was badly affected by corrosion.
The accuracy of the System Health Reports. Whilst a number of projects have been approved and target dates of completion provided, there are several high risk scored problem statements with “Redress Pending”. Several due dates have already past the stated due dates and no new dates provided.
I therefore rated the LC28 ventilation compliance inspection Amber and I will seek improvement from the Licensee in this area.
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, 27, and 34 specifically to ventilation system. I found, however, a number of shortfalls against compliance with LC28.
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, 27, and 34, and an inspection rating of Amber for LC28 is merited here.
For the Amber rating, I will raise an enforcement decision record to seek improvement in this area. One L3 regulatory issue has been raised, RI-12618.
I also raised one L4 regulatory issue to monitor the progress of alignment of the ES with the CC and PMS, RI-12616.