Office for Nuclear Regulation

Sellafield – Inspection ID: 52156

Date(s) of inspection

  • November 2023

Executive summary

Aim of inspection

The aim of this inspection is to seek assurance that SL’s arrangements for compliance with LC35 (Decommissioning) are adequately implemented within the Sellafield Remediation Value Stream and specifically the Prototype Fast Reactor (PFR) Plant (B277) on Sellafield Ltd.’s nuclear licensed site at Sellafield, Cumbria.

Subject(s) of inspection

  • LC35 – Decommissioning – Rating: Green

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

This LC35 inspection covered the plan for decommissioning the B277 PFR facility, with particular focus on the decommissioning of the C5 containment cell, and its implementation. The inspection confirmed that the project is being progressed in line with relevant Sellafield Ltd arrangements, and has a structured programme of work to fully decommission the C5 containment cell to a defined end-state.

The project team demonstrated drive to progress the project and work was found to be progressing adequately. There was evidence of a ‘decommissioning mindset’ open to exploring opportunities to accelerate the project where possible. The project team recognised challenges, such as establishing sufficient teams of operators trained to work in air-fed suits in a C5 environment and to carry out adequate characterisation of the facility to inform the development of plans to manage wastes that will arise from the decommissioning and were addressing them appropriately.

The C5 containment cell has an Examination, Inspection, Maintenance, Inspection and Testing regime covering the structure and the seals on the large number of penetrations. This was found to have some shortfalls,  but was justified as ALARP. Work is planned to improve the sealing of these penetrations.
The inspection was rated green.


On the basis of the evidence sampled at the time of the inspection, I judge that there is an adequate plan for the decommissioning of the B277 C5 containment cell that is being progressed in line with the relevant Sellafield Ltd arrangements. The decommissioning work is being progressed appropriately.

Noting the ONR guidance on inspection ratings, it is my opinion that an inspection rating of Green (no formal action) is appropriate.