Office for Nuclear Regulation

VDMP Battery Tank Vulcanisation review

Executive summary

Purpose of Intervention

This intervention, conducted at the Licensee’s Devonport Royal Dockyard Limited (DRDL) Devonport licensed site, was undertaken to conduct a readiness review of the equipment and procedures required for the steam vulcanisation of the Vanguard battery tank lining, which would support the close out of decision record ONR-OFD-DR-18-009.  This activity is new to DRDL and requires the supply of low pressure steam into a large sealed compartment. The safety case for these operations has been categorised as ‘B’ on the basis of conservative fault modelling.

Interventions Carried Out by ONR

This inspection examined the adequacy of DRDL’s arrangements to ensure that risks associated with the steam vulcanisation process have been reduced so far as is reasonably practicable.

The inspection covered the steam supply and equipment from the point of take-off from the site steam ring main, through the pressure reducing stations to the battery tank compartment; including procedural controls, isolation and safety arrangements.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

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

From the evidence obtained from DRDL during this inspection, I am of the opinion that the Licensee is making adequate arrangements and preparations for the conduct of the battery tank steam vulcanisation process.

The inspection found that the safety documents relating to the battery tank steam vulcanisation process were adequate, and identified the arrangements required to ensure that gross over-pressurisation of the battery tank could not occur.

Whilst the safety devices were considered appropriate and were available, the steam supply rig had not been fully reassembled at the time of inspection, and an action has been placed on the DRDL internal regulator to confirm the correct configuration prior to use.

A small number of improvements to test form governing the vulcanisation process were highlighted during the inspection.  Given the nature of these amendments, no specific regulatory follow-up activity is required.

In my opinion there is an adequate Plant Manager’s Hold Point to control the requirements prior to the operational use of the steam supply rig. ONR intends to monitor the progress of the preparations in forthcoming routine site interventions.

Conclusion of Intervention

No matters were identified as requiring immediate regulatory attention during the inspection.

Adequate preparations have been made by the Licensee for the battery tank vulcanisation, and I am satisfied that the Licensee’s arrangements will ensure that the risks associated with the activity are being appropriately managed.

The decision record relating to the battery tank vulcanisation could not be fully closed out by this readiness inspection and further verification will be conducted by ONR when the plant and arrangements are in a suitable operational condition.