PSI - Issue 36

Volodymyr Sydorenko et al. / Procedia Structural Integrity 36 (2022) 318–325 Volodymyr Sydorenko, Sergiy Yeremenko, Viola Vambol et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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4

based on mathematical and statistical dependencies of deflation factors; deflation models based on the results of studies of the physical nature of soil aerodynamics and climatic factors (Poberezhny et al., (2017)). The latter is closest to an adequate description of the processes of propagation of combustion products. However, in terms of their functioning, all these deflation models are ambiguous and can be classified into three main groups: 1) deflation forecast based on mathematical and statistical dependencies of deflation factors; 2) deflation based on the results of studies of the physical nature of soil aerodynamics and climatic factors; 3) forecasting the transport of radionuclides during deflation. A distinctive feature of such models is the use of nonparametric coefficients, which are usually subjective. This, in turn, is reflected in the calculations when predicting the transport of radioactive substances. Most of the known models do not take into account the peculiarities of soil differences; they do not contain information on the granulometric composition of the soil, which is a rather important indicator. A real description of such processes can be modeled using a mathematical tool that takes into account the rise and atmospheric transfer of radioactive aerosol in calculations, that is, it most fully takes into account the physical essence of the R С P deflation after a forest fire and gives its objective parametric assessment in the form of a module. But to date, such a theoretical model is unknown. The closest to a real description of such processes can be a forecasting model using the results of experimental studies. Experimental studies of a radioecological nature, the main of which are the distribution of the specific activity of radionuclides in the structural fractions of soils of different genetic types, as well as special aerodynamic studies, will make it possible to use these results for a model for predictive calculations of the transfer of radioactive matter. In this case, the proposed approach is based primarily on the fact that the nature of deflation parameters, such as radioactivity, maximum wind speed, duration of dust storms, etc., is essentially revealed. The description of the distribution of radionuclides in the air after a forest fire assumes the use of the Gaussian statistical model and the model of turbulent diffusion (Newstand (1985)). For each category of atmospheric stability (according to the Pasquill- Guyford classification), the surface concentration of the point emission of the RСP was determined by the expression:

1

N

 = = 1 i

q

  

 

  

  

y

h

2

2

i

exp

exp

C

−

=

−

(1)



i

2

2

u   

y

y

2

2











y z

where С - surface concentration of a point release of radioactive combustion products; q i – amount of release of the i-th radionuclide; u – average wind speed; у – coordinate of the calculated point; h – height of the emission source; σ у , σ z – standard deviations of the RСP in the Y and Z directions for a certain category of atmospheric stability. The maximum concentration of RPL in the surface layer will be determined by the formula:

q

 =  max

C

i

(2)

h   

i

y z

To obtain the dependence of the concentration of their impurities in the atmosphere, it is enough to perform the integration procedure expression (2) over the area of the RPS emission source, and then we obtain the formula: