Increased risk of a nuclear submarine accident

A serious fault has been found which could affect 12 submarines. As a result the risk of an accident occuring on a nuclear submarine is higher than the Navy has previously estimated. One of these submarines, HMS Triumph, is about to return to service without its reactor having been inspected. There is an urgent need to revise the Clyde Public Safety Scheme and other schemes to take account of this.

The problem on HMS Tireless

There was a serious reactor accident on HMS Tireless on 12th May when the submarine was between Sicily and North Africa. Cracks appeared in the reactor coolant circuit and coolant escaped in the form of steam. The Guardian on 28 October quoted an authorative source as saying that the reactor had been "at the very point of failure", in other words it came close to a meltdown. HMS Tireless arrived in Gibraltar on 19th May and the local population was told that it would only be there for a short time and would then sail to Devonport where it would be repaired.

In late June the MoD announced that they had changed their plans and that the submarine would be repaired in Gibraltar harbour. This was opposed by the majority of local residents. The Gibraltar government appointed several independent nuclear experts to advise them. When the MoD refused to provide information to these experts the Gibraltar government formally opposed the repair. This forced the Navy to disclose classified information. In due course the panel of experts reported that they were satisfied with the repair as planned and the Gibraltar Government gave their approval.

On 21 October the situation changed dramatically when the MoD admitted that the problem on HMS Tireless was much more serious than they had expected. They had initially said that there was a 2 mm crack. They now admitted the cracks were at least ten times bigger. Crucially the cracks affected the main coolant pipe and were possibly the result of metal fatigue. The defect is very close to the reactor pressure vessel.

The Navy will not have a revised plan for the repair ready and tested until the end of January at the earliest. The Gibraltar government have deferred judgement on the new repair plan. The Spanish nuclear safety organisation CSN has been briefed on the problem by the MoD. In a public report the CSN said that they are concerned about whether the new repair plan will be successful. Juan Manuel Kindelan, the president of CSN, has told the Spanish press that he is concerned that there could be another leak in the reactor when it is started up again.

The local authorities responsible for Spanish towns adjacent to Gibraltar and the Andalusian parliament have formally opposed the repair of the submarine in Gibraltar.

"Tireless" problem on other submarines

The MoD released a list of submarines on which signs of the "Tireless" defect had been found. This included 5 of the 7 Trafalgar class submarines based in Devonport and 2 of the 5 Swiftsure class submarines based at Faslane (HMS Superb and HMS Splendid). It is believed that, with the exception of HMS Tireless, the list was based not on any physical examinations, but on looking at data from inspections made years earlier.

The report by the Spanish experts, CSN, said that there was a "design fault" and a "generic problem". This almost certainly reflects what they were told by the Royal Navy.

On 21st October the MoD announced that all Trafalgar and Swiftsure class submarines, 12 in total, would be withdrawn from service for checks.

HMS Triumph

HMS Triumph was sent home to Devonport from the Mediterranean and it docked on 27th October. Then on 1st November, Geoff Hoon announced that HMS Triumph was "clear of the flaw" and would return to operations shortly. This must have been the result of political and operational pressure. It would not have been possible to inspect the reactor in this timescale. With HMS Tireless it took 5 months to examine the reactor.

The same failure which almost resulted in a meltdown on HMS Tireless could recurr on HMS Triumph. The Defence Minister said that HMS Triumph would be used in support of Trident and so it is likely to sail in Scottish waters and to visit Faslane.

Clyde Public Safety Scheme

The Clyde Public Safety Scheme was drawn up by the Navy in association with local authorities. Its main purpose is to safeguard the public in the event of a submarine reactor accident.

The scheme says that "The overall probability of an accident severe enough to require the countermeasure of evacuation beyond 550 m from the accident submarine is assessed to be less than once in 50,000 years of reactor operations." These and other probability assessments were made without taking account of the current generic defect on Trafalgar and Swiftsure submarines. The severity and nature of the problem on HMS Tireless would suggest that the risk of an accident is significantly higher than has been assumed. As a result the countermeasures proposed in the safety scheme and the areas which could be affected should be revised. The same would apply to other submarine safety schemes.

The MoD cannot reasonably claim that the Clyde Public Safety Scheme provides adequate protection for the public in the event of a visit to the Clyde from HMS Triumph.

Trident

The MoD claim that the defect does not affect Trident submarines directly. Trident submarines have a reactor which is different but was based on that on older submarines. It is possible the problem could affect Trident. The Navy's policy towards HMS Triumph suggests that operational considerations are being put first. This policy could explain why Trident would appear to be unaffected.

John Ainslie, Scottish CND, 9 November 2000