Transport Mechanisms of Radioactive Substances in the Arctic Ocean -Modelling
and Experimental Investigations in the Kara and Barents Seas
In recent years, it became known to the public that the former Soviet Union
had dumped large amounts of radioactive waste in the Arctic Ocean since about
1959. The waste was dumped into the Kara and Barents Seas in liquid and solid
form, sealed in containers, as reactor parts but also as complete ship reactors
including spent fuel. Wrecks of nuclear submarines were dumped near the coast
of Novaya Semlya, in depths less than 50 m. The dumping took place in
contradiction to international rules and conventions as far as the areas,
the depth, the distance to the coast, and the type of waste is concerned.
After initial over-estimation of the total radioactive inventory, the amount
of the waste and the dump site locations are well known, meanwhile. International
pressure and the more open information policy of Russia helped to improve
the situation. Various international fora primarily within the IAEA and the
Arctic Monitoring and Assessment Programme (AMAP) investigated the potential
consequences from these dumping practices. This report is the German contribution
to these international assessments.
The dumped objects in the Kara Sea encompass 17 nuclear ship reactors, seven
of them still carrying spent fuel. Four dump sites are located in small and
shallow fjords at the east coast of Novaya Semlya, and in the Novaya Semlya
Trough, in max. depth of 420 m. The total radioactive inventory was, at the
time of dumping, 37 PBq (Peta-Becquerel = 1015 Bq).
During the project numerous samples from seawater and sediment were analysed
on artificial radionuclides in Arctic waters. This included samples from
the Kara Sea but also samples around the Russian nuclear submarine Komsomolets
sunken in the Norwegian Sea southwest of the Bear Island at a depth of about
1700 m in April 1989. Numerical hydrodynamic models in local, regional and
global scale were used to predict the potential dispersion of released
radionuclides from the dumped wastes and reactors in the Kara Sea.
It could be shown that most of the detected artificial radionuclides originate
both, from the global fallout during the 50s and 60s from atmospheric weapon
tests, and from former discharges from the nuclear reprocessing plants in
western Europe, primarily the Sellafield plant in the UK. A large scale
contamination from the dumped wastes or reactors in the Kara Sea could not
be ascertained. This was also the case for water and sediments close of the
sunken Komsomolets. The investigations included fission and activation products
and plutonium isotopes and other transuranics.
Dispersion simulations based on the inventories under the assumption of various
scenarios showed no long range contamination of adjacent sea areas. Even
under the conditions of unlikely "worst case releases" the predicted activity
concentrations in the European Northern Seas will stay below present or previous
levels originating from global fallout and the Sellafield discharges. In
direct vicinity of the wastes in the bays of Novaya Semlya the expected levels
are significantly higher.