Towards a unified modeling system of predicting the transport of radionuclides in coastal sea regions

Abstract

We present in this talk a recent progress in developing a unified modeling system of predicting three-dimensionaltransport of radionuclides coupled with multiple-scale circulation, wave and suspended sediment modules, keepingin mind the application to coastal sea regions with non-uniform distribution of suspended and bed sediments ofboth cohesive and non-cohesive types. The model calculates the concentration fields of dissolved and particulateradionuclides in bottom sediment as well as in water column. The transfer of radioactivity between the water columnand the pore water in the upper layer of the bottom sediment is governed by diffusion processes. The phasechange between dissolved and particulate radionuclides is written in terms of absorption/desorption rates and distributioncoefficients. The dependence of distribution coefficients is inversely proportional to the sediment particlesize. The hydrodynamic numerical model SELFE that solves equations for the multiple-scale circulation, the waveaction and sand transport on the unstructured grids has been used as a base model. We have extended the noncohesivesediment module of SELFE to the form applicable to mixture of cohesive and non-cohesive sedimentaryregimes by implementing an extended form of erosional rate and a flocculation model for the determination ofsettling velocity of cohesive flocs. Issues related to the calibration of the sedimen application to coastal sea regions with non-uniform distribution of suspended and bed sediments ofboth cohesive and non-cohesive types. The model calculates the concentration fields of dissolved and particulateradionuclides in bottom sediment as well as in water column. The transfer of radioactivity between the water columnand the pore water in the upper layer of the bottom sediment is governed by diffusion processes. The phasechange between dissolved and particulate radionuclides is written in terms of absorption/desorption rates and distributioncoefficients. The dependence of distribution coefficients is inversely proportional to the sediment particlesize. The hydrodynamic numerical model SELFE that solves equations for the multiple-scale circulation, the waveaction and sand transport on the unstructured grids has been used as a base model. We have extended the noncohesivesediment module of SELFE to the form applicable to mixture of cohesive and non-cohesive sedimentaryregimes by implementing an extended form of erosional rate and a flocculation model for the determination ofsettling velocity of cohesive flocs. Issues related to the calibration of the sedimen