Possibility of estimating radioactive fallout by modelling atmospheric processes

The deposition of radioactive wastes like precipitation is formed as a result of the settling of long-lived explosion products from the atmosphere. If the parameters of the explosion (intensity, geometry, type of explosion and etc.) form a qualitative composition of radioactive products, then the effect of the meteorological infl uence are fi nally reduced to transport and change of the concentration of radioactive contamination.

The paper suggests methods and means for solving Scattering of radioactive impurities is determined by stratifi cation, turbulence and other parameters of the atmosphere, the direction and speed of their spatial distribution -the parameters of the direction and speed of the wind.
Particles with sizes less than 10-12 microns moving at a speed identical to that of vertical movements (≈1cm /s) precipitate on the Earth's surface either in the turbulent motion of air masses (dry deposition), or by washing out sediments (wet and wet sediments) [1].
Assuming, in accordance with the well-known idea of Taylor and Schmidt [2], that the process of turbulent diffusion is equivalent to the process of molecular diffusion, one can obtain the next formula for the vertical turbulent heat fl ux in the surface layer of air.
where  is the air density (typical value is around 1.23 × 10 -3 g/cm 3 The following symbols are introduced into the equation (4): If there is a movement of radionuclides in several parallel (by altitude) layers, then the equation (4) can be generalized to the case of n set of meteorological and physical parameters, The solution of the equation (5) is well known. Neglecting one of the solutions that will give rise physically incorrect result, we obtain the following expression for the excess concentration of radioactive particles in the atmosphere (more detailed see in [4]) where △ is the coeffi cient that determines the intensity of deposition of radioactive fallout (RF) and expressed through meteo-and physical parameters of the atmosphere in the form The analysis of the formula (7) implies a very simple conclusion: the higher the wind speed, the greater the distance from the emission source from which the radioactive particles will be carried away. In this sense, the most undesirable option for studied process is a constant by altitude wind both in direction, and in value. In this case, all radionuclides independently on their mass characteristics (chemical element, mass, isotope and etc.) will be concentrated in one place and in the form of RF fall onto the Earth's surface.
More preferable looks the option when the wind speed is different by altitude thereto the lower the altitude, the lower the wind speed. In this case, the zone of contamination of the terrain with heavy radionuclides will not be so wide, since heavy RF will fall down in areas near the source of pollution is located.
The zone of contamination with light radionuclides, on the contrary, will be more extensive. A priori, it will be very diffi cult to draw a conclusion about, when the total intensity of radiation contamination will be less or, conversely, more. It all depends on fact, which radionuclides were polluted into the atmosphere at the time of the explosion. The determination of the form of the function △n (z) makes it possible to estimate the degree of contamination of the zones of interest to us by radionuclides.
Since within the framework of our model we assume that there are n layers of radionuclides in the atmosphere, the total contamination per unit time and per unit length of the surface under consideration will be determined from the formula provided below. As a result of pollution of the RF on a regional and global scale, it is necessary to use ground-based and remote methods and means of observation. The most effective use of radar remote sensing systems (RSS) in conjunction with optoelectronic equipment [5,6]. The most benefi t of radar RSS is the absence of weather and time (day/night) restrictions [7] for getting information.
Radar means for detecting radioactive meteorological 4. Development of special algorithms for processing refl ected radar signals [8].

Conclusion
In this paper the main factors of formation of radioactive wastes in the form of precipitation are revealed. On the basis of turbulent diffusion, a method has been demonstrated for the transport of contaminants, both regionally and globally.
A model for moving radionuclides in several parallel (altitudes) atmospheric layers is proposed. The model takes into account the meteorological parameters determining the intensity of radioactive waste deposition. The model can be applied to any territory and predict radioactive pollution of the territory; it's necessary just include into the model meteo -and terrain/landscape specifi cations of the territory under research.