Office for Nuclear Regulation

System Based Inspection (SBI) of the Nuclear Fire Protection Systems on 9 Dock

Executive summary

Purpose of Intervention

This System Based Inspection (SBI), conducted at the Devonport Royal Dockyard Limited (DRDL) Devonport licensed site, was undertaken as part of the 2018/19 intervention plan and propulsion sub-division strategy.

The SBI targeted the nuclear fire safety/protection systems (fire prevention, protection and suppression) on 9 dock; sampling the primary circuit decontamination building and associated systems, and general dockside, to confirm the adequacy of implementation of the licensee’s safety case in respect of the identified systems.

Interventions Carried Out by ONR

The SBI covered the following Licence Conditions (LCs):

The inspection assessed the applicable nuclear safety case claims for the control of fire hazards on the 9 dock through a combination of document reviews, discussions with DRDL and ship staff, and facility inspections to determine compliance against the selected LCs. For LC 34 it was identified that in the current operational node there are no direct radiological consequences related to the leakage and escape, should a fire occur in 9 dock and impact the nuclear safety systems sampled, therefore a decision was made to not assess LC34 during the inspection.

Explanation of Judgement if Safety System Not Judged to be Adequate

The licensee has demonstrated that the Safety Systems, Structures and Components (SSCs) that have been sampled as part of the fire protection systems, are able to fulfil the safety functional requirements adequately, in line with the safety case. 

Key Findings, Inspector's Opinions and Reasons for Judgements Made

The following finding was identified during the system based inspection and will be raised as a formal Regulatory Issue.

This finding related to a specific shortfall against LC24, where the licensee was unable to provide clear demonstration that adequate arrangements and controls are in place to manage the location and distribution of combustible materials and ignition sources (fixed and transient), on 9 Dock. The absence of adequate arrangements and controls does not align with Relevant Good Practise (RGP), and in our opinion this shortfall could impact nuclear safety systems. ONR Technical inspection Guide (TIG) ‘LC24 Operating Instructions’ (NS-INSP-GD-024, Revision 3), paragraph 4.2 states that “operating instructions produced under this licence condition should ensure that operations that may affect safety are adequately controlled”. To reflect this it was deemed appropriate to rate LC 24 ‘Operating Instructions’ as ‘Amber’.

Whilst some minor issues were observed against LCs 10, 23, 27 and 28; these items were not considered to have a nuclear safety significance and were fed back to the licensee during the intervention. These are raised as observations to inform the licensee’s future operations on the Devonport site. As such, inspection ratings of Green were awarded for these License Conditions.

Conclusion of Intervention

From the evidence gathered during this SBI; noting the finding cited earlier and minor issues identified, the ONR inspection team judged that the fire detection, protection and suppression systems meet the requirements of the safety case, and their implementation is deemed adequate.

One regulatory issue is to be raised to address the shortfall relating to the management of combustible materials and ignition sources.  The minor observations which did not have nuclear safety significance have been raised with the licensee for their consideration.