A major milestone has been achieved in the Long Overhaul Period
(Refuel) (LOP(R)) being undertaken by Babcock on HMS Vigilant at
Devonport Royal Dockyard, with the successful completion of
refuelling last week, two years in to the LOP(R) programme.
The refuelling of a nuclear submarine takes around seven months,
from removing the reactor head to access the fuel modules to
replacing the reactor head when refuelling is complete, and
involves nearly 100 highly trained and experienced refuellers. The
extremely complex and demanding procedure is carried out to the
most rigorous of safety standards. Babcock has a considerable depth
of knowledge and breadth of experience in this field, and is the
only company in the country with the facilities and expertise to
undertake open core reactor work on in-service submarines.
The refuel and subsequent reactor commissioning is a critical
component of the three and a half year LOP(R) and dictates the
overall programme duration. This is supported by a major
revalidation of all reactor systems and replacement of major
equipment such as the reactor pressure vessel head, main coolant
pumps, and reactor instrumentation suite.
HMS Vigilant has now been refuelled with Core H, as used in the
new Astute class submarines, providing power for the remainder of
the submarine's operational life, without the need to refuel.
Commenting on this key milestone, Babcock submarine programme
director, Gavin Leckie, said: "Refuelling a nuclear submarine is an
exceptionally demanding project, and the refuel teams have been
working tirelessly to achieve this successfully, to the highest
possible safety standards. The end of the refuel signals the start
of the final phase of the LOP(R) programme with the focus switching
to commissioning submarine systems and reinstating the submarine
structure in readiness for flood-up in the summer. The joint
project team understands the strategic importance of achieving the
key programme milestones in 2011 and is ready for the challenging
year ahead."
The refuelling of HMS Vigilant was successfully completed on
Friday 19 November.
Flood-up will take place in summer 2011 and the LOP(R) will
complete in 2012, following sea trials of HMS Vigilant.
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NOTES TO EDITORS
In addition to the refuel and reactor work, the LOP(R) also sees a
significant number of upgrades to the tactical and strategic
weapons systems, as well as a vital and substantial overhaul of the
propulsion system including main engines, 700KW motor generators,
rehabilitation of the tailshaft and changing of the propulsor, plus
major external represervation work, and upgrades to the
accommodation and mess areas.
More than 2,000 personnel (including 500 skilled technicians and
tradesmen) and 2.2 million manhours are involved in the LOP(R).
The refuelling operation can be split into six main phases. The
first of these is preparation of the submarine to take the
Refuelling Access House (RAH), involving removal of the submarine's
rudder, a large section of the casing (weighing some eight tonnes)
and cutting and removal of a section of the pressure hull. The 700
tonne RAH is then moved over the submarine, ready for the next
phase which involves lifting the reactor compartment tunnel plug to
gain access to the reactor. The teams then detension and remove the
reactor pressure vessel (RPV) head nuts and studs, allowing access
to the main seal membrane, which is cut to allow the RPV head to be
removed. At this stage, the 'stack-up' is bolted on to the RPV core
barrel to allow the water level to be raised, and all operations
thereafter are carried out remotely within the water-filled
stack-up. Fuel modules are removed, the core barrel cleaned and
inspected, and new modules are installed. The final stage is to
remove the stack up, replace the RPV head and weld the main seal
membrane, followed by reinstallation onto the RPV head of new and
refurbished components to operate and drive the control rods.