Assessment of Ecological Risk to Biota of Stepovoi Bay of the Kara Sea after Hypothetical Accidental Contamination.

A dynamic mathematical model of the accumulation of radionuclides in the marine biota of Stepovoi Bay was carried out for the scenario of a hypothetical accident with a spontaneous chain reaction with a submerged K-27 submarine. The dynamic model MARINA II was used to calculate the transfer of radionuclides with water masses and the transition to the bottom sediments of the bay. The modeling results were applied to calculate the dynamics of the radiation dose rate for the marine biota of Stepovoi Bay and to assess the environmental risk for the hypothetical accident scenario considered. The predicted radioactive contamination of water is determined mainly by 137Cs and 90Sr, and contamination of bottom sediments, by 137Cs, 90Sr, and 151Sm. The averaged contamination of sediments by 137Cs in this scenario is predicted at a level that is significantly lower than the criterion for attribution to solid radioactive waste. Model assessments have shown that the maximum levels of accidental 137Cs and 90Sr in the fish of Stepovoi Bay was reached one year after a single release, and it does not exceed the established hygienic standards. The highest risk index in the accident scenario considered was estimated for a marine mammal (provided that the animal is permanently located in the bay) and amounted to 0.07. Negative radiation effects are not expected to occur for the ecosystem of StepovoI Bay at this level of environmental risk. The obtained value of the generalized indicator of radioecological safety indicates a weak radiation effect on the ecosystem of the bay for a marine mammal in Stepovoi Bay. [ABSTRACT FROM AUTHOR]