On 7 April 1989 the Soviet nuclear submarine 'Komsomolets' sank in the Norwegian Sea about 185 km southwest of the Bear Island at bottom depth of about 1700 m. Potential sources of radioactive contamination are the reactor and the nuclear warheads. A Komsomolets Foundation has been established consisting of the Russian constructor
of the submarine, a Dutch salvaging consortium and some environmentally oriented
parties. The goal of this foundation is to get international financial support
for its plans to either salvage the submarine totally, to salvage the torpedo
part or to seal off the torpedo part of the submarine. A report from an expert
working group to Norwegian Minister of Foreign Affairs, however, concludes that
the best solution is to leave "Komsomolets" where it is.
Radioactive components in the wreck which may be dissolved and spread in the
water masses, include cesium-137 and strontium-90. Insoluble plutonium will
settle in the sediments and remain in the vicinity of the wreck. The present
study is dealing with the most likely pattern of the distribution of radioactive
elements in the water masses if a leakage from the wreck occurs. The study is
based on hydrographic observations, current measurements and numerical models.
By assessing the potential radioactive pollution from "Komsomolets",
it is concluded that the sunken nuclear submarine represent a minor radioactive
pollution problem for the following reasons:
• the great depth where the possible release of radioactive material will
take place,
• the relatively small amount of radioactive material available for release,
• the enormous water masses available for dilution,
• the additional "chemical /biological dilution" (the radioactive
isotopes of strontium and cesium are only a very small fraction of the total
amount of these elements in sea water. The biological uptake will reflect this
ratio between the radioactive and the non-radioactive isotope)
• the relatively biologically inactive plutonium will be confined to particulate
form in the sediments close to the release point
The distribution of possible radioactivity in the water masses will be along
isopycnic surfaces. The radioactive components will be spread by the pulsating
current in the area, but they will remain in the deep water and gradually be
diluted as they are dispersed from the source. It is not likely that watermasses
to any measurable extent will rise from the depth of about 2000 m to the surface.
If so, the concentration will only be a small and insignificant fraction of
the contion near the wreck. Even assuming that the submarine might represent
a 10 MWatt heat source, a hot plume possible containing radioactive material,
would rise to a maximum height of about 500 m above the bottom. The radioactive
components will therefore gradually be dispersed in the deep water masses of
the Nordic Seas and the Arctic Ocean, which has a volume in the order of 10
million km3. The deep water which is advected out of the area, flows as bottom
water across the deeper passages in the Greenland-Scotland Ridge to sink into
the abyssal depths in the Atlantic from where it spreads in the deep circulation
of the world oceans. Residence time in this system is assessed to range from
a few to about 15 centuries.
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