Nuclear repairs will take many months

There are currently three nuclear powered submarines at Faslane which have been taken out of service and two more are held in Rosyth dockyard. All seven Devonport based submarines are being withdrawn from service, with one of them in Gibraltar. The Navy has realised that there is a fundemental fault on the reactors of all these vessels. Repairs to the submarines will be a long and costly exercise. It is likely that some of them will be scrapped.

The Spanish paper El Pais on 31 October reports that the president of the Spanish Nuclear Safety organisation (CSN), Manuel Kindelan, has said that repairs to the fault found on British submarines could take six, twelve or more months. He also indicated that the main concern is about the danger when the reactor on HMS Tireless is started up at the end of the repair. Tireless is currently in Gibraltar after a nuclear reactor accident. There has been widespread opposition in Gibraltar and Spain to the plans to repair it at the berth in Gibraltar harbour.

The report on the proposals for HMS Tireless contains new details on what is planned. The Navy is considering two options:

(1) To cut out the pipework in the affected area and to design and build a new junction which would then be welded in place.

(2) If a suitable junction cannot be designed and built they will consider rerouting the pipework so that the pipe from the pressuriser joins the main pipe elsewhere, probably further from the Reactor Pressure Vessel. This would be a more substantial change to the reactor design. It would take longer and might affect the functioning of the reactor. As they are dealing with a generic defect on 12 submarines they may consider this a better long term solution. On the other hand the engineers are under pressure to have the problem dealt with as quickly as possible.

The CSN report describes the cause of the problem as a metal fatigue which was the result of a poor design and the fluctuations of temperature. This implies that the defect is caused by the fact that at the junction there is a small pipe joining a larger pipe. When the reactor is started up, running and shut down, the temperature and pressure in the primary circuit goes up and down. These changes will affect the metal in both pipes. The way in which the two pipes of different diameter respond to these changes will be complex. The problem may be greater because of the additional effects of radiation on the metal, particularly given the proximity to the reactor pressure vessel.

The Navy still do not understand the cause of the cracks, so they will be unable to properly decide what to do about them. If they go ahead with their first option this will mean cutting the main pipe close to the reactor pressure vessel and welding this again - the integrity of this weld will be crucial. Under this first option, they are also proposing using a new part for the junction. I am not convinced that this new part can be designed and tested properly in a short period of time. Both of these factors will affect the risks of starting up and testing the reactor - they cannot be certain that the weld or the new join will work.

This would be a major repair if it was carried out during a refit in a dockyard. If it was done in a dockyard either there would be no fuel in the reactor, or there would be a new fuel core, which is far safer. Because they are working with a fuel core which has been in use, the complications of actually carrying out the repair will be greater. They may also be more restricted in their ability to test the system. I think what is proposed will take many months. It is likely that a submarine in Devonport will be repaired first. The most likely candidate is HMS Torbay, which is in a dry dock. It is at the end of a refit. It has a new fuel core on board but the reactor has not yet been started up.

All this suggests a long timescale for the repair. The CSN report says that the repair should be approved by the end of January and could be completed in March. But I notice today that the British Foreign Office are denying that they suggested March or any other date, at the Blair/Aznar meeting. El Pais quotes Kindelan as saying six, twelve or more months. I think this is more likely.

It is possible that the Navy could consider a repair in the dry dock in Gibraltar, but this would not be an easy option. Nuclear submarines are repaired at dry docks at Devonport and Rosyth in Britain. The design of these facilities has been reviewed by the Nuclear Installations Inspectorate (NII). The NII were concerned that the docks were not strong enough to withstand an earthquake - this is a requirement of all civil nuclear facilities. There was particular concern that the gates of the docks would fail in an earthquake of the magnitude considered in nuclear safety criteria. Modifications have been made to the docks to make them stronger.

In addition, a new dry dock is being modified in Devonport so it can be used to repair the larger Trident submarines. This project is two years behind schedule, because of the need to comply with nuclear safety criteria.

While there is a civil dry dock in Gibraltar, it would almost certainly require substantial modifications to bring it up to the standards required to be approved as a nuclear facility. This would take a long time. Modifying the Gibraltar dock would probably be subject to approval from the NII The NII have reluctantly gone along with the proposals for Devonport because this is modifying an existing facility, if it was a new proposal it might not have been allowed, because of the proximity of houses. NII is part of the Health and Safety Executive (HSE), but I am not sure if they have authority in Gibraltar. They might well reject a plan to made the dry dock at Gibraltar a nuclear facility, because of its proximity to houses.

The Royal Navy have no hunter killer submarines to deploy so the Admirals will be demanding that this problem is dealt with as quickly as possible. I think that there will be engineers and scientists involved who know that this is a complicated problem which will take many months to work out, but they will be under pressure to come up with a solution quickly. The Guardian article on 29 Oct suggested that there was friction between the Ministry of Defence and the reactor engineers/designers, Rolls Royce and Associates, over who was to blame for this fiasco. This is not a good climate for them to make a sound decision on the safest way forward

Up to date information on the situation in Gibraltar can be found on iberianews and panorama

John Ainslie, 31 Oct 00