As part of the International Arctic Seas Assessment Project (IASAP) of IAEA, a working group was created to model the dispersal and transfer of radionuclides released from radioactive waste disposed of in the Kara Sea and bays of Novaya Zemlya and to assess the radiological impact. Existing models were extended, and new models developed to incorporate several features of the area (including ice formation and transport) which present modelling challenges. An extensive inter-model comparison involving both compartmental and 3-D hydrodynamic models was then carried out. Finally, the radiological impact was assessed based on several release scenarios prepared by the IASAP Sources working group. These included 'best estimate' release, 'plausible worst case' and 'worst case' scenarios. Collective dose as well as individual dose to identified populations were calculated. This paper reviews the models developed, highlights the general features of the inter-comparison and discusses the radiological impact assessment and conclusions based on it.

Concentrations of 137Cs were determined in surface and sub-surface waters sampled in 1994, from the Norwegian Coastal Current, Norwegian Sea, Barents Sea, Fram Strait, Greenland Sea and the Iceland-Faroe Gap. Additional surface samples were taken from the Iceland-Faroe Gap in 1995. The data were compared with previous measurements from the region. Concentrations in the south-western Barents Sea continued to decline, a trend matched by the decrease in the release of reprocessing waste. The flux of 137Cs into the Barents Sea in 1994 was estimated to be 300–400 TBq, including 100–200 TBq of fallout origin. The calculations were based on both contemporaneous hydrographic observations and published transport estimates. A further 120–180 TBq of 137Cs, of non-fallout origin, was estimated to have been transported through Fram Strait into the Polar Ocean.

As part of the International Arctic Seas Assessment Project (IASAP) of the International Atomic Energy Agency (IAEA), a working group was created to model the dispersal and transfer of radionuclides released from radioactive waste disposed of in the Kara Sea. The objectives of this group are: (1) development of realistic and reliable assessment models for the dispersal of radioactive contaminants both within, and from, the Arctic ocean; and (2) evaluation of the contributions of different transfer mechanisms to contaminant dispersal and hence, ultimately, to the risks to human health and environment. With regard to the first objective, the modelling work has been directed towards assessment of model reliability and asone aspect of this, a benchmarking exercise has been carried out. This paper briefly describes the benchmark scenario, the models developed and used, and discusses some of the benchmarking results. The role of the exercise within the modelling programme of IASAP will be discussed and future work described.