Improvement of the dose assessment tools on the basis of dispersion of the ⁹⁹Tc in the Nordic Seas and the Arctic Ocean

¹ Norwegian Radiation Protection Authority, 1332 Østerås, Norway
² Alfred Wegener Institute for Polar and Marine Research, 120161, 27515 Bremerhaven, Germany
³ Ocean Atmosphere Systems, Schanzenstrasse 36, 0357 Hamburg, Germany
⁴ Institute for Marine Research, University of Hamburg, Bundesstrasse 53, 20146 Hamburg, Germany

Abstract

Compartment models are widely used for the evaluation of radiological consequences to man and biota in the marine environment over large spatial and long temporal scales. The model developed at the Norwegian Radiation Protection Authority (NRPA) is based on a compartment modelling approach that includes terms describing dispersion of radionuclides into oceanic space with time (non-instantaneous mixing in oceanic space). In this paper the latest modification of the NRPA model will be presented. The main improvement concerns the “time of availability” parameters (i.e. the times at which dispersed radionuclides reach compartment boundaries). The modifications have been implemented through the use of a comprehensive ⁹⁹Tc data set collected under the course of the project “RADNOR” and through comparison with the results of simulations provided by the 3D hydrodynamic NAOSIM model. The present version of the NRPA model describes the dispersion of ⁹⁹Tc in the Arctic Ocean and seas with a significantly improved precision for some marine regions. Results of the calculations indicate that defined “time of availability” parameters are in good agreement with transit times observed in the actual marine environment.