R. Heling, M. Zheleznyak, W. Raskob

The Hydrological Dispersion Module (HDM) of the RODOS (real-time on-line decision support) system for nuclear emergency management in Europe has been is developed at IMMSP, Kiev, Ukraine; NRG, The Netherlands; FZK, Karlsruhe, Germany; SPA “TYPHOON”, Obninsk, Russia; IPEP, Minsk, Belorussia, and NCSR “Demokritos”, Athens, Greece. Initial testing and customisation work was performed by NPPRI, Slovakia. The hydrological model chain of RODOS was outlined covering processes, such as runoff of radionuclides from watersheds following deposition from the atmosphere (RETRACE), transport of radionuclides in river systems (1-D model RIVTOX) and the radionuclide behaviour in lakes, reservoirs and estuaries (the radioecological box model LAKECO, the 2-D model COASTOX, and the 3-D model THREETOX). The main results of the HDM are simulated concentrations of radionuclides in water following the atmospheric fallout. HDM provides also the supplementary possibility to simulate radionuclides transport in aquatic systems following a direct release of radioactive material into water. The output from the HDM is transferred into the aquatic food chain and dose model FDMA (part of RODOS) to assess the main exposure pathways. The various hydrological models of HDM have to be adapted during the RODOS implementation phase taking into account the specific properties of the hydrological network in the area of implementation. Key-Words: Hydrological dispersion models, radionuclides, lakes, reservoirs, estuaries, runoff, Chernobyl