Executive summary
Date(s) of inspection
- June 2026
Aim of inspection
This intervention was undertaken across the AWE Nuclear Security Technologies Explosives Business Unit (XBU) and aligns with the Office for Nuclear Regulation (ONR) 2026/27 integrated intervention strategy for the weapons sub-division.
The activity supports Theme 1 'Sustaining Improved Safety Performance' as set out within ONR's XBU regulatory engagement plan and links with the key regulatory objective (KRO) and the below desired regulatory outcomes (DRO):
- DRO1.1 - Risk informed and targeted engagements (RITE) interventions, against the key themes, will be undertaken throughout the AWE Plc business on a sampling basis, both as BAU and on a reactive basis.
- DRO4.1 - ONR will deliver its regulatory oversight against the Weapons 2026/27 IIS plan of interventions to gain confidence of AWE Plc’s performance in routine regulatory attention.
- DRO4.4 - ONR will continue collaboration with EA, DNSR and HSE Explosive Directorate deliver the effective joint regulation of both sites.
The purpose of this inspection was to assess the adequacy of arrangements for managing risks associated with activities involving nitrocellulose NC, and to determine whether these arrangements are being effectively implemented to ensure that risks are reduced as low as practicable, and compliance with the Explosive Regulations 2014 (ER 2014).
The specific aims of this inspection were to:
- Confirm that responsibilities and accountabilities for activities relating to NC are clearly defined, understood and discharged (People).
- Verify that facilities, plant and equipment used for storage/processing are suitable, maintained and consistent with arrangements (Plant).
- Confirm that procedures, instructions and stock management (QMAS) provide effective control of explosive risks and enable traceability and compliance (Process).
Subject(s) of inspection
- Explosive Regulations 2014 - Rating: Amber
Key findings, inspector's opinions and reasons for judgement made
The ONR inspection team attended the XBU, which is located on the AWE Aldermaston nuclear licensed site on 10 June 2026 to undertake this inspection of management, handling and control of nitrocellulose (NC). The joint inspection team comprised an inspector from the Defence Nuclear Safety Regulator (DNSR), an explosive specialist from the Health and Safety Executive (HSE), and the site inspector.
A number of documents were requested in advance of the inspection and these were received in a timely manner and were sampled as part of preparation activities. The inspection followed a high-level scope that had been proposed by ONR and shared with XBU in advance of the inspection.
The inspection targeted the adequacy of arrangements for managing and controlling risks associated with activities NC, to determine whether these arrangements were being effectively implemented to ensure that risks are reduced as low as practicable, and compliance with the Explosive Regulations 2014 (ER 2014).
Elements of good practice were identified as part of the inspection. For example, the implementation of a centralised inventory management system (QMAS) with strengthened pre-movement checks, active management and reduction of explosive holdings, and generally appropriate facility condition and labelling standards.
Areas for improvement were identified in relation to the clarity of work instructions, custodianship assurance processes, and the robustness of inventory management controls, and the tracking and implementation of improvement actions, with associated regulatory advice shared with the dutyholder.
A shortfall was identified and raised with the dutyholder in relation to the following area: a lack of demonstrable evidence to confirm that legacy NC is being maintained and managed in accordance with AWE's arrangements, and previous enforcement requirements.
Based on the areas sampled, a significant shortfall was identified during this inspection and an AMBER rating (Seek Improvement) was awarded. An ONR Regulatory Issue has been raised to ensure that the identified shortfall is adequately addressed by the dutyholder.
Conclusion
This inspection identified a significant shortfall with respect to aspects relating to the management and control of nitrocellulose.
This inspection was rated AMBER (Seek Improvement).
This rating is in line with the established ONR guidance as follows:
- Significant or systematic failure to implement or meet compliance arrangements.
- Deficient arrangements for compliance with legal requirements.
This shortfall has been shared with the dutyholder as a ‘Finding’ and an ONR Regulatory Issue has been raised to track resolution.