Office for Nuclear Regulation

Sellafield Site – Inspection ID: 52152

Date(s) of inspection

  • October 2023

Executive summary

Aim of inspection

The purpose of this inspection is to gain assurance that Mixed Oxide Demonstration Facility is compliant with Sellafield’s arrangements for Licence Conditions 23, 24 and 26.

Subject(s) of inspection

  • LC23 – Operating rules – Rating: Green
  • LC24 – Operating instructions – Rating: Green
  • LC26 – Control and supervision of operations – Rating: Green

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

The Plutonium Contaminated Material (PCM) Radiological Safety Case for MDF was suspended following the 2015 Long Term Periodic Review (LTPR) as a number of operations within HAZAN C3.11 were no longer required. This meant that there were no PCM drum movement/exports allowed to the Engineering Drum Storage (EDS). There was discrepancy between Radiological and Criticality Clearance Certificate (CCC) where CCC was not updated to suspend PCM operation, which resulted in historical PCM drums being exported from MDF to EDS outside of the safety case. In June 2022, PCM movement was reintroduced in an updated safety case to enable the MDF to maintain the glove ports, bag out the PCM waste in the gloveboxes into 200L PCM drums and export these to EDS via an approved waste route. This enables essential maintenance activities and support the delivery of Post Operational Clean Out (POCO) and decommissioning projects within the building. ONR sought assurance of this updated safety case and its implementation through a nuclear site licence condition inspection.

ONR undertook a planned intervention on 3-4 October 2023 at the Sellafield Mixed Oxide (MOX) Demonstration Facility (MDF). The intervention focussed on the reintroduced PCM Safety Case and compliance with Licence Conditions (LC) 23 (Operating Rules), LC 24 (Operating instructions) and LC 26 (Control and Supervision) and their implementation of the safety case. The inspection team comprised the Site Inspector and Fault Studies Specialist Inspector. The inspection included discussions with Sellafield Ltd personnel, review of records, documents and processes and a targeted walk down of the facility. ONR looked at the golden thread regarding the current Safety Case (SC), Criticality Clearance Certificate (CCC), Operational Clearance Certificate (OCC), Operating Rule Compliance Checksheet (ORCC) and required Operating Instructions (rOIs). Furthermore, ONR sampled work packages, reviewed Condition Reports (CRs), assessed control and supervision of the workforce including DAPs operation Logs, operational and/or conservative decision making cases (ODMs/CDMs), how personal was appointed and the relevant training records.

From the evidence sampled, I judged that Sellafield Ltd. had adequately implemented the safety case for PCM movement and the following Licence Conditions were rated as green (no formal action): LC 23 (Operating Rules), LC24 (Operating instructions) and LC26 (Control and Supervision).


On the basis of evidence sampled during the inspection, I judge that Sellafield Ltd. has adequately implemented the safety case within the MDF and is compliant with the requirements of LCs 23, 24 and 26. I have assigned an inspection rating of green (no formal action) in respect of these LCs.