Kursk meltdown threat eases, but long-term menace remains

A spokesman for the Norwegian Radiation Protection Authority said on Wednesday that the normal levels indicate that the crew of the Kursk

successfully shut down the vessel’s nuclear reactors before it hit the seabed.

The Norwegian authority has been regularly monitoring the radiation levels in the air and water around the stricken vessel through a network of permanent monitoring stations in northern Norway, to determine whether abnormal radiation has been released into the environment.

A "worst case scenario" envisaged in the days after the announcement of the sinking of the Kursk was that an uncontrolled chain reaction in the engine compartment could cause enough heat to melt the outer casing, releasing molten fuel onto the seabed. Speculation focussed on whether the two reactors had been shut down in time, and if they had not, on whether the submarine’s automatic cooling system would function sufficiently to prevent one or other of the reactors cracking in the heat, allowing sea water to surge in.

An assertion by Russian navy spokesmen that the reactors had been shut down was thrown into doubt when other official statements about the sinking of the Kursk proved later to be unfounded. A report on NTV private television earlier on Wednesday that meteorologists in Murmansk had detected a rise in radiation levels on the Barents Sea coast caused alarm, but was rapidly denied.

The Russian Navy’s Chief of Staff Viktor Kravchenko dismissed the reports, as did Norway’s Bellona Foundation and the Radiation Protection Authority. A spokesman for the Authority said Norwegian divers had taken samples during last Monday’s attempted rescue operation, both inside and outside the hull of the submarine and that "none of these shows any leakage from the nuclear reactors."

However, the danger of radioactive pollution — which could wipe out the local fishing industry on which Murmansk depends — remains. An expert with Bellona warned last week that even when a submarine reactor is shut down, a significant amount of heat is still produced by radioactive decay.

If the convection system designed to cool the reactors has been disrupted by the crash on the seabed, there would be a danger of a reactor cracking, he said. The incoming seawater would produce a plume of radioactive water on the current. Another expert with the Greenpeace environmental protection group noted that the convection could well be badly effected because the vessel was lying on the seabed on its side.

The heat produced by radioactive decay will remain a source of danger for several weeks, experts say. The Komsomelts, a nuclear-powered submarine which sank in the Barents Sea in 1989 in some 2,000 metres of water, is reported to be leaking radioactive material slightly but not contaminating fishing grounds. Several environmental groups have called for the Kursk, lying in much shallower water, to be lifted from the seabed to avert possible contamination. But technical experts have warned that this could cause an even greater disaster if the strain of the lifting caused the vessel to break up and spill its reactors into the sea.