Office for Nuclear Regulation

Rolls Royce Submarines Limited (RRSL) – Inspection ID: 51955

Executive summary

Date(s) of inspection:

  • September 2022

Aim of inspection

The purpose of this inspection was for ONR to examine the adequacy and application of the external flood preparedness and protection for the RRSL Raynesway nuclear licensed sites to gain confidence in the Raynesway site response to flooding events.

Subject(s) of inspection

  • LC23 – Operating rules – Rating: Green

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

RRSL was able to provide a comprehensive overview of the Raynesway flooding hazard in accordance with the inspection scope. Through presentations, discussions with staff, and plant and area walkdowns RRSL provided evidence that the river flooding hazard is modelled, monitored and controlled in accordance with the description in the safety case.

The river level alerts and on-site preparation were established to be robust.

The procedures in response to river level alerts were shown to be well understood and updated in accordance with operating experience.

The RRSL staff and contractors spoken to were able to demonstrate an understanding of their role in the delivery of actions in response to river level warnings and a wider understanding of the site flooding response and safety case.

The overall judgement from the inspection is that RRSL provided an adequate demonstration of its processes and preparedness for a site flood due to the river Derwent. The scope of the inspection was met.


I judge that RRSL provided an adequate demonstration of its processes and preparedness for a site flood due to the river Derwent. The information provided on flood modelling and alerts and the procedures controlling the response were supported by the experience of the operational staff. There was a good understanding of the site response in accordance with the safety case demonstrated by all staff and contractors we met during the intervention.

I judge that the hazard definition is robust and welcome the commitment to ensure that the modelling remains appropriate by engaging on the changes to local flood defences and adoption of updated climate change impacts through UKCP18.

I judge that RRSL demonstrated the on-site equipment to be available for use in accordance with its procedures and that the on-site procedures are well understood and practiced by facility and site staff and that the procedures incorporate lessons learnt from the site response to flood warnings.

In my opinion, RRSL has implemented adequate arrangements for licence condition 23 – Operating rules, with regard to river flooding, meeting the regulatory expectations set out in the relevant inspection guides.

Based on the sample taken, I rate LC23 as GREEN (no further regulatory action). I have not identified any issues significant enough to warrant raising a regulatory issue.

  • “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.”