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Trident delay caused by reactor safety concerns

Defence Board (09)62Scottish CND has gained unique access to a document which explains why the British Government has delayed the Initial Gate decision on Trident Replacement.   In November 2009 the Defence Board, the highest non-Ministerial group in the MoD, considered a paper on the Successor Submarine Project. Following an Internal Review under the Freedom of Information Act a heavily redacted copy of the 30-page document was released to Scottish CND.  The paper argues for a 12 month delay in the programme so that the MoD could gather "assured evidence" on which they would base their decision on what type of reactor to use for the replacement for the Vanguard class submarine.  It also reveals that there are serious safety concerns about all submarines that are currently in service in the Royal Navy. This was reported in the Guardian and broadcast on Channel 4 News on Thursday 10 March.

The MoD are considering two "families of designs" for the new nuclear-armed submarine:

(1) Adapt Astute - This includes one option using the current PWR2 reactor as planned for Astute boat 5, and another option with a modified reactor, PWR2b.  This modified version would incorporate changes to "improve platform safety and survivability".

(2) Derived Submarine - This would have a new PWR3 reactor.  The propulsion (reactor) system is described as "based on a modern US plant" and as "based on a US design but using UK reactor technology".  This design would include technologies based on those in Astute but updated to "improve availability, reliablity and maintainability".

A significant part of the paper presented to the Defence Board was a report from Commodore Andrew McFarlane, the Defence Nuclear Safety Regultor (DNSR).  Commodore McFarlane presents a forceful argument why the MoD must keep risks As Low As Reasonably Practicable (ALARP).  He says that there is a requirement to comply with best practice and argues that when looking at new systems which will be in service well into the future then the higher standard of best practice should be adopted.

He then says that the current design of British nuclear submarines "falls significantly short of benchmarked good practice".  While much of the detail of his argument has been redacted, it is clear that this assessment is based on comparing British nuclear reactor design with civil practice and with US Navy standards. 

Information on current US reactor specifications has only recently been available to the Royal Navy. America provided Britain with one nuclear reactor for HMS Dreadnought in the 1960s but for most of the last 40 years they refused to hand over details of how the reactor technology has developed. This situation has changed within the last 5 years. In 2008 Commodore Steve Dearden, Director Nuclear Propulsion MoD, gave an interview which referred to the revival of US-UK submarine reactor cooperation - “We had an initial exchange, the US then effectively stood to one side, we developed a capability, they moved on and then we came back together after a period of time.  We have a fairly robust technical exchange currently”. 

The Defence Board paper confirms that co-operation on submarine reactors has revived, providing the Royal Navy with a better indication of the standards used by the US Navy -

"In recent years the opportunity for greater technology interchange with the US and greater benchmarking with the UK civil nuclear power generation industry has allowed more comparison."

US reactor technology has moved a long way since the Westinghouse S5W reactor supplied for HMS Dreadnought.  A new form of reactor, using a passive cooling system, was developed for the S5G design. This was demonstrated on a land-based prototype and then on USS Narwhal.  From this the Department of Energy created the S8G design which is used on Ohio class Trident submarines.  A further variant, S9G, was developed for the Virginia class.

These American reactors can operate without coolant pumps. This makes them quieter and also means that they are less susceptible to an accident.  British reactors need a back-up power system to run the coolant pumps if the reactor shuts down.

Commodore McFarlane points out that current Royal Navy submarines "compare poorly with these benchmarks".  He highlights two particular safety concerns:

(1) Control of submarine depth.  There are two ways that the depth of the submarine is altered.  One is by adjusting  ballast and the second is by driving the boat forward under power and changing the angle of the diving planes.  It is thought that the latter is the primary method used on modern nuclear submarines. The precise problem with British submarines is not explained, but the concern may be that a loss of power, from a reactor that requires cooling pumps, could result in the submarine continuing on an uncontrolled dive.  The Commodore's report says that this risk is "orders of magnitude" greater than a Loss of Coolant Accident.  The implication is that, when it comes to the risk of loss of depth control, Royal Navy submarines are far more dangerous than their American equivalents.

(2) Loss of Coolant Accident (LOCA).  The Commodore presents the dangers of a LOCA in a more dramatic way than documents produced for local authority submarine accident safety schemes.  He starts by saying that "All pressurised water reactors are potentially vulneralbe to structural failing" resulting in "a release of highly radioactive fission products".  He then says that the submarine hull "may" contain the majority of this radioactive material, implying that it might not.  This section is heavily redacted, but it is likely that he argued that the risk of a LOCA would be substantially reduced if a passive-cooling-system reactor, like PWR3 was used.

This report has implications beyond the Trident replacement decision for submarines that are currently in service and the Navy's plans for the Astute class. The MoD have already allocated over £6 billion to the Astute programme and the total cost for seven boats is likely to reach £10 billion.  After running aground on the Isle of Skye the first boat, HMS Astute, has been handed over to the Royal Navy (five years late), but it is still not in operational service.  If the PWR2 is "significantly below benchmarked good practice" then why are new boats, which will be in service for 30 years, being built with this type of reactor ?

With regard to the replacement for the Vanguard class, Defence Minister Liam Fox told Parliament on 16 February that "the precise configuration of the reactor is still under consideration", implying that the MoD have still not decided whether they are adopting PWR2 or PWR3. 

In another written answer Mr Fox revealed that a total of £905 million was allocated for the Concept Phase of the new submarine, from 2007 until 2011. This included £254 million to extend the Concept Phase (the newly released report gives a similar figure of £261 million), and £59 million for "United States High Steam Generators and technology" allocated in April 2009 (this should probably be High Pressure Steam Generators).  The latter is a further indication that the PWR3 option is dependent on US technology.

David Cameron is caught between a rock and a hard place. He can either put sub-standard reactors in the new submarines or spend unquantified millions on a new design. But there is a third way. He could show real leadership and scrap this ridiculous project.







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