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Croatian Meteorological Journal, Vol. 43 No. 43/2, 2008.

Original scientific paper

AN ANALYTICAL NON-STATIONARY DISPERSION-DEPOSITION MODEL

Marcelo Caputo ; Comisión Nacional de Energía Atómica Bariloche, Río Negro, Argentina
Marcelo Gimenez ; Comisión Nacional de Energía Atómica Bariloche, Río Negro, Argentina
Claudio Padra ; Comisión Nacional de Energía Atómica Bariloche, Río Negro, Argentina

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Abstract

In this work an atmospheric dispersion-deposition model to describe the radionuclides concentration after a hypothetical
nuclear accident is presented. The developed model has two parts. The first one describes the concentration due to the material
released after an arbitrary period from a given source. The second one describes the concentration change during the current period
due to the dispersion of the material that is in the atmosphere. Here the solution for the first part is presented.
A non-stationary analytical solution is obtained from the atmospheric diffusion equation. The model solves the transport (convection-diffusion) equation in which the contaminant settling is explicitly incorporated. Regarding the boundary conditions, it is assumed a null diffusion through the mixed layer top and an albedo at the ground level. From the general solution obtained for the contaminant concentration the Gaussian plume formula is derived as a particular case when it is assumed a stationary point source, vd =0 (total reflection) and vs,=0 (without settling). Assuming vd ≠ 0 and vs,= 0, is compared with the Source Depletion Model (SoDM) and with the Surface Depletion Model (SuDM). The agreement is excellent when comparing with the SuDM, which is the exact solution for the diffusion equation when the settling is modeled only in the boundary condition. Two additional cases are presented, the former is the steady state solution: vd ≠ 0 and vs, ≠ 0, and the last one is a non-stationary simulation with a transport time of 3600 s with vd ≠ 0 and vs, ≠ 0. For the last case, two Erf functions appear in the solution as result of time integration that model the plume front traveling in the atmosphere.
This new contaminant transport model describes the concentration evolution in a more realistic way, representing the plume falling.
This is an improvement respect to the known dispersion-deposition models (SoDM, SuDM).

Keywords

Atmospheric Dispersion-Deposition model; Analytical solution of atmospheric diffusion equation

Hrčak ID:

64332

URI

https://hrcak.srce.hr/64332

Publication date:

12.12.2008.

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