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Problem on Tireless in Gibraltar undermines safety case for all submarines

Scottish CND today called for the reactors on all submarines to be shut down. The recent accident on HMS Tireless undermines the safety case for all British nuclear submarines.

On 12th May there was a loss of coolant accident on HMS Tireless in the Mediterranean. This was caused by a crack in a weld in the primary coolant circuit. The submarine then sailed to Gibraltar under auxiliary power. Initially the Navy planned to tow it from there to Devonport. In June they announced that they planned to repair the reactor at the berth in Gibraltar. Gibraltar is entirely unsuitable for this, most of the population live within the 2 km safety zone around the berth. There has been strong opposition both in Gibraltar and in the adjacent region of Spain.

Independent nuclear consultant John Large is travelling to Gibraltar to carry out an investigation into the risks of repairing the submarine for Peter Caruana, chief minister of the Gibraltar Government. John Large told the Glasgow based Sunday Herald:

"I am suspicious about why the submarine can't come back under tow. Rough weather and running out of diesel are not very plausible reasons. It may be that the loss of coolant was more serious than they admitted. If there was a big loss of coolant, the hull would be compromised. .. We don't know if the faulty weld had been redone during HMS Tireless's recent refit. A weld is incredibly critical. If you have a weld failure on a reactor it is critical. The welds are sonic-checked. If one fault got through, then there is a likelyhood that other could have."

There has been a previous occassion when a nuclear submarine was towed a long distance. In August 1990 HMS Conqueror was towed from Faslane to Devonport where the vessel was scrapped.

A spokesman for the chief minister in Gibraltar said that the MoD had to jump through two hoops - "They have to convince the government that repairs will be safe. Secondly they have to convince public opinion."

Captain Hurford, Chairman of the Naval Nuclear Regulatory Panel, is in Gibraltar and has spoken to the local press. There are three crucial points he has admitted:

(1) They don't know what caused the problem. He said "we still don't know precisely why this failed".

(2) This is the first time there has been an accident like this. He said "The Navy has had nearly 40 years' experience with nuclear submarines .. and without a defect of this sort."

(3) This accident has implications for the safety of other submarines. He said "we are doing a lot of checks on other submarines to investigate this particular area."

The accident is probably the most serious which has happened on a British nuclear submarine at sea. The temperature and pressure in the primary coolant circuit are so high that if there is a crack then coolant is lost very quickly. This can result in damage to the integrity of the reactor compartment and to the fuel core. They were lucky to avoid a catastophic release of radiation into the atmosphere.

The safety case for all submarines has been affected by this accident. Tireless completed a refit at Devonport in June 1999. During the refit there would have been inspections of welds in the primary circuit using ultrasound and other methods. The system for carrying out these inspections and analysing the results appears to have failed. This has implications for the safety of all welds in the reactors of all submarines. This in turn fundementally undermines the safety case of all submarines. This includes the Trident boats. Although the Trident's have never been into a refit, there would have been similar checks on welds during construction at Barrow.

As there are implications for other submarines, and as the cause of the accident is as yet unknown, the Navy should keep the reactors on all submarines shut down, which means keeping them in port, while this problem is thoroughly investigated.

A 1992 Navy training manual says that the risk of a loss of coolant accident is 1 in 10,000 years of reactor operations. The type of accident described in the manual is one in which there is a breach in the primary coolant circuit which results in damage to the fuel core and to the reactor compartment. On Tireless there was a breach of the coolant circuit, it is not clear if there has been damage to the core or reactor compartment. However it came close enough to indicate that the figure of 1 in 10,000 years should be revised. These Navy calculations are the basis on which the Navy's Clyde Public Safety Scheme has been drafted. If the probability of this type of accident is higher than was previously assumed, then the emergency plans have to be revised.

There are signs that the problem is affecting other submarine operations. The Navy has admitted that only one, HMS Triumph, of the seven Trafalgar class submarines is at the moment operational. On Wednesday three Tridents were in Faslane, the fourth will be on patrol. Of the five Swiftsure class only one is at sea. They are also working on or inspecting the reactor on HMS Superb at Faslane, as the reactor firm, Rolls Royce and Associates, are alongside it in force.

Two recent issues have emerged in Gibraltar -

The MoD fire service is not able to provide full cover for the submarine as it is regularly assigned to the airport, leaving the civil fire service providing primarly fire cover for Tireless.

On 29 July it was reported in the Gibraltar Chronicle that members of the TGWU are seeking support of the district committee to start industrial action against the repairs on Tireless.

Regular updates on the Tireless story are available at:

www.panorama.gi and www.iberianews.com