Office for Nuclear Regulation

Devonshire Dock Complex (Barrow) – Inspection ID: 50929

Executive summary

Date(s) of inspection:

  • November 2022

Aim of inspection

This was a planned intervention to evaluate the adequacy of the arrangements for licence condition 22 (modification or experiment on existing plant) and their implementation at BAE Systems Marine Limited (BAESML). BAESML undertakes changes in key nuclear safety case elements as the build stages of the submarines progress; correct configuration control through appropriate LC22 arrangements is important in ensuring nuclear safety is maintained.

The intervention was conducted on-site by the ONR nominated site inspector for BAESML, utilising relevant good practice from ONR-INSP-GD-022 revision 7. The inspection was undertaken along with an inspector from the Defence Nuclear Safety Regulator.

Subject(s) of inspection

  • LC 22 – Modification or experiment on existing plant – rating: Green

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

Based on my sample, I judge that BAESML has a robust process in place for the categorisation and approval of site modifications, though its arrangements for this process are somewhat complex. BAESML is already undertaking a programme of improvement in this area.

The use of a site-wide ‘heat map’ to track the potential cumulative effect/risk of open modifications in key areas of the site represents best practice.

Some opportunities for improvement were identified during the inspection, such as provision of a training/mentoring process for design change sponsors/authors, guidance on the threshold between temporary and permanent modifications, and sufficient detail in the change application database to allow tracking of the current stage of each modification.

Examination of ONR-selected modification forms revealed no significant issues. None of the findings in the inspection presented an immediate or direct risk to nuclear safety.


Based on the sample inspected, I rate the LC22 intervention as GREEN – ‘No Formal Action’. This rating is in line with the established ONR guidance.

  • “Relevant good practice generally met, or minor shortfalls identified, when compared with appropriate benchmarks.”
  • “No significant shortfalls identified in the delivery of safety, safeguards or security functions.”