Raising the Kursk

Divers say it's too dangerous to enter the Kursk

By BBC News Online's Kate Goldberg

Russia must now decide what to do with the ruins of its devastated nuclear submarine, the Kursk, lying at the bottom of the Barents Sea.

The options are costly and complicated. It could take two to three weeks just to plan the operation, and is likely to cost in excess of $100m.

If they proceed too hastily, it could go disastrously wrong, leaking radioactive material into the sea.

The bodies of the 118 crew have not yet been recovered, and Norwegian divers say it is too dangerous to go into the submarine.

Appeal for help

No single country on its own can handle such an operation

Deputy Prime Minister Ilya Klebanov

Options for salvaging the vessel - and recovering the bodies - include dragging the submarine to shallower waters, refloating it, or sealing it off to prevent radioactive leaks.

Moscow is seeking international help in funding the operation.

"No single country on its own can handle such an operation," said Deputy Prime Minister Ilya Klebanov, who has been put in charge of the vessel's future.

With winter fast approaching, some experts say the vessel must be moved within the next month, before bad weather sets in.

The logistics

Weight: 25,000 tonnes est.

Length: 155 metres

Depth: 108 metres

Cost of salvage: up to $100m

However, others argue that it would be better to wait until next summer, when more information is available.

It normally takes at least three months for a submarine's nuclear reactors to cool down, and attempts to move the vessel too early could crack the hull, releasing radioactive matter, according to Nils Bohmer of the Bellona Foundation.

"It's vital to ascertain the condition of the reactors first," he told BBC News Online.

"I'm very afraid of any decision being taken to move the vessel when so little information is available."

The options

The Rubin research centre in Saint Petersburg, which developed the Kursk, is already studying ways of salvaging the submarine.

• Refloat:The 155-metre vessel could be lifted with the help of cables attached to platforms or by giant air cushions, and then towed back to base, according to Admiral Vladimir Kuroyedov.

  Another radical option being considered is to strap balloons made of a special hi-tech fibre along the hull, and pump them with enough air to raise the estimated 25,000 tonne vessel to the surface.

  The relatively shallow depths - of just over 100 meters - at which the Kursk is lying make the option of refloating the submarine fairly feasible, according to Paul Beaver of Jane's Information Group.

• Chop up: If the Kursk is too damaged to stay intact, experts say the wreckage could be sawn into pieces to be hoisted individually. Or the reactor compartment alone could be lifted out - although this would again require special, very expensive, equipment.

• Move to shallow waters: Alternatively, it could be dragged to shallower waters. This may be a short-term option used to recover the bodies before winter. However, the journey could still be dangerous.

• Seal off reactors and leave: Some experts are saying that the safest option would be to hermetically seal the submarine, preventing radioactive leakage. The wreckage could then be left at the bottom of the sea.

  The Russians have developed a special biological gel, which was used when the Soviet submarine, the Komsomolets, sank in 1989. The gel is said to block all cracks, and has the advantage of being lighter than conventional materials. Russian specialists claim that this material works effectively for 500 years. However, it is also very expensive.

Marine graves

The Kursk is the sixth nuclear submarine to sink since the 1960s.

Two of the sunken submarines have been American, the other three Russian - buried at depths of up to 4,800 metres.

Most of them have been left on the seabed because of the huge expense of lifting them.