The painfully slow process of dismantling ex-Royal Navy nuclear submarines

There are currently 20 former Royal Navy nuclear submarines awaiting disposal in Rosyth and Devonport. They do not represent a great hazard but maintaining them safely while they await dismantling is a growing drain on the defence budget. Nuclear submarines are arguably Britain’s most important defence assets but the failure to promptly deal with their legacy has been a national scandal. Although there has been discussion and consultation going back years, only recently has there been action to actually start the disposal process.



Plans for the safe and timely disposal of nuclear submarines should have been drawn up as far back as the 1970s but successive governments have avoided difficult decisions and handed the problem on to their successors. RN submarines were designed so the Reactor Pressure Vessel could be removed from the hull. Other nations cut the entire reactor compartment out of the submarine and transport it to land storage facilities. The US has successfully disposed of over 130 nuclear ships and submarines since the 1980s. The Russians have disposed of over 190 Soviet-era boats (with some international assistance) since the 1990s while France has already disposed of 3 boats from their much smaller numbers.

The first Royal Navy nuclear submarine, HMS Dreadnought decommissioned in 1980, has now been tied up in Rosyth awaiting disposal longer than she was in active service.

As any householder knows, It is sensible practice to dispose of your worn out items before you replace them with new ones.

The capacity to store more boats at Devonport is limited, every further delay adds to cost that will have to come from a defence budget that is much smaller in real terms than when the boats were conceived at the height of the Cold War. Apart from the attraction of deferring costs in the short-term, a major cause of delay has been the selection of a land storage site for the radioactive waste. It has also taken time to develop a method and ready the facilities needed to undertake the dismantling project.

Afloat storage

While awaiting dismantling, decommissioned submarines are stored afloat in a non-tidal basin in the dockyard. Classified equipment, stores and flammable materials are removed together with rudders, hydroplanes and propellers while the hull is given treatments to help preserve its life. The 7 submarines in Rosyth have all had their nuclear fuel rods removed but of the 13 in Devonport, 9 are still fuelled. This is because in 2003 the facilities for de-fuelling were deemed no longer safe enough to meet modern regulation standards and the process was halted. Submarines that have not had their fuel rods removed have the reactor primary circuit chemically treated to guarantee it remains inert and additional radiation monitoring equipment is fitted.

More than £16m was spent between 2010-15 just to maintain these old hulks alongside, and costs are rising. Apart from regular monitoring, the hulks need to be hauled out of the basin for occasional dry docking for inspection and repainting to protect the hull from corrosion. All this effort and expense is a drain on precious resources for no direct gain. Responsible care of the growing number of hulls means they pose little risk to the local population, but a tiny risk does remain. This makes some people living nearby uneasy and provides another grievance for those idealogically opposed to nuclear submarines and Trident.

The good news is that the Submarine Dismantling Project (SDP) finally started in 2016. HMS Swiftsure is in number 2 dry dock in Rosyth and will be the ‘pathway’ project to prove the dismantling process. Disposal of the eventual total of 27 boats will cost at least £10.4bn over 25 years and continue into the 2040s. The MoD Disposal Services Authority (DSA) is in consultation with Babcock (with owns both the Rosyth and Devonport sites) to agree on the final timescales and costs for the project. The task at Rosyth is easier with just 7 submarines that all had their fuel removed some time ago.

Preparing the sites

Work has been continuing at Devonport over the last few years on the De-fuel, De-equip and Lay-up Preparation (DDLP) project which centred on preparing number 14 Dock for submarine dismantling. This work had to be done concurrently with the initial decommissioning work on HMS Turbulent and HMS Tireless and the refits of HMS Trenchant and HMS Talent in number 15 dock. In the early 2000s a major upgrade to the nuclear refitting facilities was completed (Project D154), to support both the maintenance and future dismantling of submarines. The giant 80-ton crane at the centre of the Submarine Refit Complex that used to dominate the dockyard skyline was used for lifting reactor components but this has been dismantled and replaced with a safer and more efficient Reactor Access House (RAH). The RAH is a moveable enclosure that spans the dock and is mounted on rails on the dock walls. Number 14 and 15 dock floors were raised, multi-cellular, impact resistant caissons now seal the dock entrances and new isolating submarine cradles have been installed along with seismically qualified dockside cranes.

For fuelling or de-fuelling operations, the RAH is placed over the submarine reactor compartment and provides a stable, protected area that houses the crane and de-fuelling tools from which the operators can work safely. The RAH concept has been used successfully at across the basin in number 9 dock for refuelling the Vanguard class for some years.

As the only site that can de-fuel submarines, Devonport is well equipped to undertake dismantling work and it’s facilities now meet the latest Office of Nuclear Regulation (ONR) standards. In addition to the docks, there is the only seismically-qualified railway in the UK and the Low-Level Refuelling Facility (LLRF) which can store spent reactor cores and fuel rods, prior to being sent for storage at Sellafield.

In July 2017 the MoD announced that URENCO Nuclear Stewardship Ltd at Capenhurst in Cheshire has been selected as the interim site for storing the nuclear waste. The Reactor Pressure Vessels (RPV) removed from the submarines are classed as Intermediate Level Waste (ILW) and will be stored in purpose-built buildings above ground. They will eventually be moved to a permanent underground Geological Disposal Facility (GDF) that is supposed to be constructed in the UK, sometime after 2040.

The dismantling process in simple terms

Once the submarine is in the dry dock, the first main task will be to remove the two steam generators through holes cut in the top of the pressure hull and into containers suspended from the RAH. Then the primary circuit pipework, pressuriser and coolant pumps can then be removed. The Reactor Pressure Vessel (RPV) head is classed as LLW and is removed separately and a temporary head put in place. The primary shield tank (PST) which surrounds the RPV has to be drained of hazardous chemicals before the RPV is then attached to a lifting cradle in the RAH. The RPV is then lifted out and placed in a special container ready on the dock bottom. Once the RPV is sealed in the container, it is lifted onto a transporter to be taken away. The remaining parts of the PST are also removed and cut up into manageable sizes. All liquids and materials removed during the process have to be sorted, segregated, size-reduced if necessary and packed into appropriate containers ready to be stored, reprocessed or recycled.

Scrapped on site?

Only about 1% of each submarine comprises the more radioactive ILW. Around 4 % is LLW and 5% is non-radioactive hazardous waste. The remaining 90% is mostly steel that can be sold for recycling. (Depending on the class of boat, anything between 3,000 – 7,000 tons). As yet, there has been no public announcement about how the submarines will be broken up, once the hazardous components have been removed. The pressure hull will have to be cut open in places for the NSRP removal and if the hulks were going to be transferred elsewhere, more work to make them seaworthy would be needed. Submarines are notoriously difficult to tow, even when manned and with a working steering gear. There is very little ship-breaking done now in the UK (most ex-naval vessels are scrapped up in Turkey) so it is almost certain the hulks will have to be broken up at Devonport and Rosyth and the scrap metal taken away by sea.

Limited options

Government has admitted there is a shortage of expertise available for the Submarine Dismantling Project. There is plenty of competition from the civil sector which is occupied decommissioning old nuclear power stations. The SDP is a very necessary but rather unglamourous task and may struggle to attract engineers who have the opportunity to work on more exciting projects. Faced with limited budgets and personnel, the MoD has little option but to proceed at this very slow pace. Until the work on HMS Swiftsure is completed the MoD is reluctant to commit to a timetable but says current assumptions are that on average, one submarine will be dismantled every 12 – 18 months at each site from 2022. Let us hope faster progress can be made otherwise, whatever the future of Devonport Naval Base, the dockyard could still be disposing of Vanguard class submarines in the 2050s.

The blame for this situation cannot be laid at the door of today’s politicians, rather it is the fault of many administrations, going back several decades. In the civil nuclear industry, operators are required by law to put aside funds and make plans during the life of the plant to pay for decommissioning. It would be prudent if a similar principle was applied by the MoD to all new nuclear submarine construction.

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