[M-AG38_2PO1] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

[MAG38-P05] An approach to chemical reactions in the atmosphere

*Tomoo AOYAMA¹, Yasutaka WAKAZUKI¹ (1.Center for Research in Isotopes and Environment Dynamics, University of Tsukuba)

Keywords:atmospheric reaction, SPM, L-particle

1. IntroductionWe discuss an approximate approach to simulate time series reactions in the atmosphere. At first, we write a reaction at definition time-t, as A+B=C. Next, we suppose that densities of the compounds are written by Gaussians. The Gaussian is a solution for general small particles diffusion processes. The time-t is discrete about the interval is dt. If 2 particles of compound A and B are interacted within the interval, the reaction reaches equilibrium, and a compound C is generated.2. DescriptionsConsidering properties of the atmosphere, we adopt Gaussian having different parameters for the horizontal and vertical directions.GA{A}(r,z)=QA{A}exp{-αA (r-rA)²-βA(z-zA)²}, (1)The suffix A corresponds to compound A. The Q is density and the unit is [M/volume] of compounds. In case of uncertain compounds chemically, it is replaced by [kg/volume]. A vector r is for x- and y-coordinates, and z is for z-coordinate. The function exp(whose arguments is 3-dimensional distance) is a kind of the volume. Eq. (1) is a relation of [M]; that is, a reaction equation, which is defined at any time.The α and β (which are positive) are diffusion parameters and they depend with elapsed time from the generation. The dependency is very complex and the evaluation is difficult. In the puff-model approach, it is calculated by many turbulence parameters. However; we wonder that model is significant in case of very diffused case. We wish to adopt Lagrangian particles (L-particles), where alpha-beta-parameters are not, and effects of the turbulence are expressed by random numbers.L-particles are a finite volume of the air, and have no shape. Therefore; we redefine it to be Gaussian. The multiply of Gaussians is a Gaussian; it is an appropriate function to express reactions.Under the representation, alpha-beta-parameters are fixed coefficients to define a unit volume. They are a kind of mesh intervals. The re-defined Gaussians are moved by meteorological fields, as if they were L-particles. The Gaussian is like as a mesh-unit in Euler approach, which has a finite volume. They are in a space, and are moved by wind fields; however, they are not arranged orderly in Euler approach. Here, if the arrangement is introduced as following;A transformation between L-particle and Euler-mesh:Q(mesh coordinates)=Integral{GA(r,z)G(on mesh)dv}, {GA(r,z)}-->{Q(on mesh)}.The transformation seems to be usable to evaluate diffused mist.3. ReactionsIn an interval time, chemical equilibrium is, Keq=[C]/([A][B]). (2)For every times,QA(t+dt)=QA(t)-QC(t), QB(t+dt)=QB(t)-QC(t), (3)rA (t+dt)=rA (t)+{u,v}Adt+Rand(), (4)ZA (t+dt)=ZA (t)+{w}Adt+Rand(), (5)Where, a vector {u,v,w} is wind speeds. Rand() is normal distributed random numbers.In another reaction, A+B=C+D, we get,Keq=([C][D])/([A][B]), (6)Since the distributions of C and D are same at the first step,GC=GD=(KeqGAGB)^0.5. (7)4. Progress of the researchWe try to simulate some reactions in the atmosphere now.