Office for Nuclear Regulation

Sellafield – Inspection ID: 52607

Date(s) of inspection

  • November 2023

Executive summary

Aim of inspection

To determine whether the safety systems, structures and components associated with the Pile Fuel Cladding Silo (PFCS) are able to adequately fulfil their safety duties (safety functional requirements), in line with claims made within the safety case.

Subject(s) of inspection

  • LC10 – Training – Rating: Green
  • 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
  • Overall Inspection Rating – Rating: Green

Key findings, inspector’s opinions and reasons for judgement made

ONR carried out a planned two-day system based inspection (SBI) of the PFCS ventilation system  on the 14 and 15 November, 2023. The inspection team comprised the Site Inspector for MSSS, Mechanical and Radiation Protection Specialist Inspectors and a Fault Studies Inspector.  The inspection included discussions with Sellafield Ltd. personnel, review of records, documents and processes and a targeted walk down of the facility.

PFCS arrangements and compliance against the following LCs were inspected as part of the SBI:
LC10 – Training; Given that the evidence confirmed that the training was sufficient to allow effective operation of the ventilation system, it was considered that the arrangements for this licence condition have been implemented adequately resulting in a green inspection rating (No Formal Action). Regulatory advice was given where it was identified that the PFCS ArgonSystem Overview training was outstanding for the majority of the maintenance team that this training should be completed.

LC23 – Operating Rules; The evidence sampled confirmed that the required Operating Instructions (rOIs) are available, clearly identify safety case requirements and are meaningful to operators resulting in a green inspection rating for this licence condition.

LC24 – Operating Instructions; It was judged that the operator instructions sampled included the instructions necessary to ensure that rOIs are implemented confirming that  the  arrangements for this licence condition have been implemented adequately.

LC27 – Safety Mechanisms, Devices and Circuits; From the sample of the licensee’s arrangements and substantiating documentation, the Licence Condition was rated green as it was judged that that suitable and sufficient safety mechanisms, devices and circuits are properly connected and in good working order.

LC28 – Examination, Inspection, Maintenance and Testing; Adequate examination, maintenance, inspection, and testing had been carried out based  on the documentation examined, discussions and the plant walkdown undertaken resulting in a green inspection rating for this licence condition. Regulatory advice was provided that Sellafield Ltd. should prioritise system health report recommendations to ensure that the ventilation systems remain in a sufficient condition to meet the lifetime demands of the facility as a whole.

LC34 – Leakage and Escape of Radioactive Materials and Radioactive Waste; Confidence was gained in the abatement system resulting in a green rating for this licence condition.  However, regulatory advice was given that Sellafield Ltd. should review and keep live the Note For the Record (NFR) – “PFCS Environment Case Note For the Record: Review of aerial discharge monitoring associated with Early Retrievals” to reflect learning requirements and outcomes, and actions established to address the two original recommendations within the NFR, and to consider both the off-gas, and the extract lines in the review of the actions.  Health physics monitoring surveys should also be reviewed as part of the facilities lead and learn approach to retrievals.

From the evidence sampled, I judged that the PFCS ventilation system adequately meets the requirements specified within the safety case. Furthermore, I was satisfied that the facility adequately understood the limits and conditions and their importance in the safety case.


Overall, I found LCs 10, 23, 24, 27, 28 and 34  to be adequately implemented in relation to the systems inspected.

Consequently, it is my opinion that for this system-based inspection a rating of Green – No formal action is appropriate for LCs 10, 23, 24, 27, 28 and 34.  The ventilation system within PFCS is judged to be adequate.