Refitting, Refuelling and Maintenance

Nuclear submarines have been worked on at Devonport since the early 1970's. Refuelling refits started in 1979. Devonport Royal Dockyard is the UK's sole refitting and defuelling site for nuclear powered submarines. Devonport's facilities have recently been upgraded to provide refitting and refuelling facilities for Vanguard Class submarines.

A submarine refit is a major programme of diverse tasks drawing on the skills and expertise of the workforce at Devonport. A major refit will take about two years to complete. Typically a submarine remains at sea for eight years and is then refitted. During refit, the submarine's pressure hull is checked for integrity and key mechanical and electrical services are examined and repaired or replaced as necessary. The opportunity may be taken to update the equipment with new technology to enhance operational performance or safety.

Refitting a nuclear powered submarine is more complex and time consuming than refitting a vessel with a conventional propulsion system. This is because radioactivity accumulates within the primary circuit of the reactor and any work in the vicinity of the reactor must be carefully controlled to minimise exposure of the workforce to radiation. Before any work takes place, the primary circuit is remotely decontaminated by flushing the system. This achieves a significant reduction in occupational exposure such that the total dose received is only around one fifth of the dose which would be received if the circuit were not decontaminated. All work in the vicinity of radioactive components is carefully planned, controlled and monitored to ensure that occupational exposure to radiation is reduced to the minimum practicable.

When the refitting programme is completed, all the submarine's systems are subjected to checks and tests to ensure that they are working individually and collectively. The final series of tests is called Power Range Testing (PRT). All the systems, including the reactor, are brought into operation to simulate conditions which will be encountered in service.

In addition to refits, submarines are taken out of service for interim servicing and maintenance programmes which are not as comprehensive as a refit and do not include refuelling.

Submarine Support

The Submarine Support Management Group (SSMG) was formed in 1998 to provide Design Authority In-Service Support (DAISS) to Vanguard, Swiftsure and Trafalgar Class submarines. The group primarily provides a wide range of services to the Submarine Support Integrated Project Team (SUBIPT) under the title Submarine In-Service Support Project. In addition, the group supports other parts of the MOD as well as Commercial Defence Contractors.

DML, acting as Prime Contractor, is supported by BMT and SEA as subcontractors and full risk sharing partners. The teaming arrangement brings together the complementary strengths of submarine support skills, including all activities associated with the refit programme of DML, with the design skills and combat system experience of BMT and SEA.

BMT has extensive experience in both platform and combat system design with a particular emphasis on Naval Architecture. SEA has a well established reputation for providing independent technical and project management support, with particular emphasis on high grade combat systems design.

The majority of SSMG personnel are employed in Bristol with easy access to the main customer bases at Foxhill and Abbey Wood. In addition, SSMG operates satellite offices at HMNB Clyde at Faslane and at DML Devonport.