Sellafield - Inspection ID: 53950 | Office for Nuclear Regulation

Executive summary

Date(s) of inspection

November 2025

Aim of inspection

ONR Nuclear Safeguards Inspectors will conduct an accountancy focussed compliance inspection of the Sellafield Ltd. Magnox Reprocessing Operations, Material Balance Area (MBA) QS03 on the 19^th of November 2025. The purpose of this inspection is to seek evidence in support of Sellafield Ltd.’s compliance with The Nuclear Safeguards (EU Exit) Regulations 2019 (NSR19).

This MBA has been targeted for the following reasons:

Magnox reprocessing operations have now ceased operations and the area is in Post Operational Clean Out (POCO). As such, nuclear material that was previously attributed to hold-up is expected to be recovered during clean-out operations.
Regulatory intelligence gathered from routine assessment of accountancy reporting under NSR19 Regulation 12(1-2) and 14 has indicated Material Unaccounted For (MUF) in QS03 to be an area of interest. This is due to the change in operations in the area, and the accountancy reports reflecting a change from a loss of material to a gain of material.
ONR believe there is a higher risk of loss of control of Qualifying Nuclear Material (QNM) in areas such as QS03, which aligns with ONR’s Risk-Informed Targeted Engagement (RITE) approach to planning inspections.

Subject(s) of inspection

FSE 4 Reporting, Anomalies, and Investigations - Rating: GREEN
FSE 6 Measurement Programme and Control - Rating: GREEN
FSE 9 Material Balance - Rating: GREEN
NSR19 Reg03 - Declaration of basic technical characteristics - Rating: GREEN
NSR19 Reg06 - Accountancy and control of qualifying nuclear material - Rating: GREEN
Overall Inspection Rating - Rating: GREEN

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

This intervention sought evidence that the declared Material Unaccounted For (MUF) in the Sellafield Ltd. Magnox Reprocessing Material Balance Area (MBA) QS03 is underpinned by suitable statistical evaluation and can be traced back to accurate operating and accounting records. ONR sought evidence that the arrangements for Nuclear Material Accountancy and Control for Safeguards (NMACS) described in the Basic Technical Characteristic (BTC) and Accountancy and Control Plan (ACP) for material balance evaluation were appropriate and being adequately implemented by those with NMACS responsibilities for the MBA. ONR also sought assurance that any non-zero inventory differences declared in the MBA were being appropriately evaluated and that arrangements were in place to investigate any significant breaches of target values.

To inform my judgements on the adequacy of the arrangements and implementation of NMACS, I utilised the Safeguards Technical Assessment Guidance (TAG), the Safeguards Technical Inspection Guidance (TIG) and Fundamental Safeguards Expectations (FSEs) as described in the ONR guidance for Nuclear material Accountancy, Control and Safeguards (ONMACS).

I held discussions with Sellafield Ltd. staff with responsibilities for NMACS, reviewed nuclear materials control and accountancy (NMCA) documentation and local instructions, and conducted an in-depth verification of source documentation used for NMACS which underpinned the MUF and associated obligation changes declared by Sellafield Ltd.

I noted a minor shortfall against ONMACS FSE 10, as quality assurance and control checks were not being adequately implemented. I have raised a Regulatory Issue [RI-12872] for Sellafield Ltd. to address this shortfall.

I noted a minor shortfall against FSE 9 of ONMACS, and the requirements set out in NSR19 Schedule 1, part 1, template I-C, paragraphs 23-26, where quantitative assessment of Inventory Difference (ID) is no longer being carried out in the area. I have raised a Regulatory Issue [RI-12873] for Sellafield Ltd. to address this shortfall.

I noted a minor shortfall against the Nuclear Safeguards (EU Exit) Regulations 2019 Regulation 3, as the BTC for QS03 does not accurately reflect the plant’s change in status from operation into Post Operational Clean Out (POCO). I have raised a Regulatory Issue [RI-12863] for Sellafield Ltd. to address this shortfall.

Based on the sampled evidence during the course of the intervention at Magnox Reprocessing (QS03), I judge that there were no significant shortfalls identified during this intervention. Sellafield Ltd. have adequate arrangements in place to meet the expectations set out in FSEs 4, 6 and 9, and that these arrangements are suitable to meet the requirements of NSR19 Regulations 3, 6 and schedule 1, part 1, template I-C, paragraphs 23-26, however, these arrangements are not being implemented as described following the plant operations change to POCO.

Overall I rated this intervention GREEN.

Conclusion

During this intervention I noted that QA checks were not being adequately implemented. These observations constitute a shortfall against the ONMACS FSE 10. I have therefore raised a Level 4 Regulatory Issue [RI-12872] for Sellafield Ltd. to address this shortfall.

Level 4 Regulatory Issue [RI-12872]: Inadequate implementation of quality assurance and control checks in Magnox Reprocessing (QS03).

From the evidence sampled, I judged that Sellafield Ltd. have suitable arrangements in place to meet the regulatory expectations set out in FSE 9 of ONMACS, and the requirements set out in NSR19 Schedule 1, part 1, template I-C, paragraphs 23-26, however, these are not being implemented as described. This constitutes a minor shortfall and as such, I have raised a Level 4 Regulatory Issue [RI-12873] for Sellafield Ltd. to address the shortfall.

Level 4 Regulatory Issue [RI-12873]: ONR’s regulatory expectation under FSE 9, is that Sellafield Ltd. should be conducting quantitative analysis of IDs. Sellafield Ltd. should either produce and implement statistical analysis and update associated documentation, or, provide ONR a technical document evidencing that qualitative analysis is a sufficient level of control for this area.

During this intervention I noted a minor shortfall against NSR19 Regulation 3, as the BTC for QS03 requires an update to reflect the current POCO status of the plant. This was previously raised as Regulatory Advice in a February 2024 QS03 intervention and was not addressed. I also noted that the ACP did not reflect the plant’s POCO status. I have therefore raised a Level 4 Regulatory Issue [RI-12863] for Sellafield Ltd. to address the shortfall.

Level 4 Regulatory Issue [RI-12863]: The QS03 BTC and ACP require updates to reflect the POCO status of the plant. Sellafield Ltd. should produce and implement a plan to update the BTC and ACP appropriately.

Based on the sampled evidence, I judge that there were no significant shortfalls identified during this intervention. Sellafield Ltd. have adequate arrangements in place to meet the regulatory expectations of FSEs 4, 6 and 9 and the requirements of NSR19 Regulations 6 and schedule 1, part 1, template I-C, paragraphs 23-26, however, minor shortfalls with compliance with these arrangements have been identified following the plant operations change to POCO, and three Level 4 Regulatory Issues have been raised.