Rain scavenging of a radioactive aerosol atmospheric precipitation

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Kustov Maksim Vladimirovich, National University of Civil Protection of Ukraine, Candidate of technical science, Associate professor E-mail: maksim_kustov@mail. ru Kalugin Vladimir Dmitrievich, National University of Civil Protection of Ukraine, Doctor of chemistry professor Levterov Alexander Antonovich, National University of Civil Protection of Ukraine, Candidate of technical science, chief researcher
Rain scavenging of a radioactive aerosol atmospheric precipitation
Abstract: Processes of rain scavenging of radioactive particulate matter have been studied by means of mathematical models. Trapping process by a rain-drop of radioactive particulate matter has been analyzed for the first time taking into account superficial properties and occurrence charge. It has been determined that occurrence of charge appreciably influences for microparticles with a r^& lt-0,1m. It has been that the most part of radioactive particles have the sizes in the range of 0,1−10 microns consequently for them intensity of rain scavenging will be the smallest.
Keywords: Fukushima, Chernobyl, Nuclear plant accident, Radioactive particles, Radioactivity-induced charge, Radioecology, Rain-drop, Coagulation, Intensity of excretion.
Discharge into the atmosphere of radioactive mater significantly deminish the contamination area and the
radiation level. It has occurred because of sorption by
can be expected at emergence of major accidents on facilities of nuclear power engineering. A large amount of gaseous and aerosol radioactive matter is spewed into the atmosphere at the emergency depressurization of a nuclear reactor [1].
Radioactive matter getting into upper troposphere under the influence of convective airflows extend on long distances.
The sizes and form of a zone of pollution are governed by weather conditions, a district landscape, existence of vegetation, density of buildings and some other factors. Atmospheric precipitation in a accident zone
drops of water of radionuclides.
Process sorptions intensity of radionuclides and rain scavenging intensity of the atmosphere from radionuclides depend on its state of aggregation, dispersion and physical and chemical properties of a radioactive particle [2- 3- 4].
Considering sorption process by drops of precipitation of radioactive aerosol particles all solid particles in preference to water can be separated on soluble and insoluble (hydrophobic and hydrophilic). Insoluble fuel particles compound the main part of radioactive dust. (Fig. 1.).
Fig. 1. SEM backscattered images of Zr-U-containing hot particles and inclusions in Chernobyl fuel particles (a) Sectional view of fuel particles (b) appearance of fuel particles [5]
Insoluble hydrophilic particles penetrate into water/an insoluble radioactive particle. drop volume with a velocity corresponding to their de- Penetration of the insoluble radioactive particles ad-
gree of hydrophily. Their bulk diffusion has been deter- sorbed on a surface of a drop will be less, than at soluble
mined by coefficient of a superficial tension on border particles due to their lower velocity.
Insoluble hydrophobic particles accumulate on the drop surface. Particles due to high surface tension don'-t penetrate into drops. In this connection the free surface of a rain-drop will decrease as time goes by owing to slow down in radioactive particles intensity of trapping.
Besides, at the radioactive radiation there is an ionization ofnearby molecules of air to the subsequent accumulation of charge on a surface of radioactive particle. It has been determined [6]. On a surface of particles accumulates 60 elementary charges owing to this effect.
Therefore, the accounting of the electrostatic has to be a necessary condition by consideration of sorption of radioactive particles rain-drops. Trapping of radioactive aerosols an atmospheric precipitation can be related to gravitational coagulation. Here the main method of removal of dangerous radioactive aerosols from the atmosphere has been given. The mechanism of gravitational coagulation consists in trapping by a coarse rein-drop of fine radioactive particles when falling. The fine aerosol particles with a radius of r and concentration of n (r)
i rp v rp'-
soar in air. It becomes under the influence of airflows (V0 «0). The drops of precipitation the size rd with some velocity V of under the influence of gravity move down. The stream of air flows round a coarse drop and entrains fine aerosol particles when falling.
As aerosol particles have weight other than zero that inertial forces affect them. forces trend to retain a rectilinear path. The probability of collision of a coarse drop with a fine particle of an aerosol (coefficient of trapping of K) is dependent from the size of drop and
particle and viscosity of the environment (n) and movement velocity.
Quantity of the aerosol particles attached to a raindrop will be defined as:
N = nR (+ r)2 Vr) ¦ n (Kp)drp. (1) 4 0
Most often the theory of similarity for determination of coefficient Kg of trapping (for creation of semi-empirical models) has been used.
In article [4] the model for definition of Kg which take into account Reynolds and Stokes and Schmidt'-s numbers has been suggested. However, this model doesn'-t take into account influence of particle charge. In article [7- 8] the first attempt of numerical modeling of coagulation process of the charged aerosol has been made:
4a qq
K = g 1 -v
a =
(o2
rp
s0nrd rrpux u = 2 Pi,
00 r, ?
9 n
V rd y
(2)
where ?0 — an electric constant- n — dynamic viscosity of air- p — drop density- u? — the potential falling speed of drops- g — gravitational acceleration.
According to (1) intensity of coagulation depends from the sizes of rain-drops, the sizes of radioactive particles, their concentration and trapping coefficient. Calculation of trapping coefficient will be executed taking into account existence of charge at the interacting particles (2).
0. 75
Kf
0. 25
100
Fig. 2. Influence of the charge of a rain-drop and radioactive particle (ne) and the sizes of a radioactive particle (r) on intensity of coagulation at rd = 1 mm, Kn ^ 0
Fig. 3. Dependence of intensity of rain scavenging of aerosol radioactive matter (dn /dT, rrp = 5 |jm, n0 =106 m-3) from intensity of precipitation (r, dNd/di)
We will assume equal in sign a charge of a rain-drop and a radioactive particle. on Fig. 1 results of estimated calculations of trapping efficiency have been introduced. From the dependence presented on Figl it is possible to see that at gravitational coagulation efficiency of particles trapping rises with increase in the sizes of radioactive particles.
Coarse particles have big inertial forces. Therefore, these particles don'-t push off the airflow which is flowing round the falling rain-drops.
It should be noted that at the expense of a lag effect of particles influence of a mutual charge to 10 4 elementary charges essentially only to fine particles. Influence of electrostatic forces will decrease with increase of size radioactive particles. Therefore, influence of a charge on intensity of gravitational coagulation for coarse particles (micron r100) can be neglected.
Radioactive particles will have the smallest intensity of atmosphere purification with a size in the range 0,110 mkm. It has been detected the analysis of calculation results.
In this connection with that thermal diffusion influences particles with such sizes insignificantly. Air drag grows. Thus it isn'-t enough inertial forces of a particle for overcoming of an airflow which flows round rain-drop.
Therefore particles of such sizes move round a raindrop without contacting to it. It should be noted, that the bulk of the radioactive particles released into the
atmosphere has been formed by particles the size of 0,1−10 micron [5].
Intensity of rain scavenging depends on precipitations intensity and dispersion of an aerosol and its concentration in air subject to a trapping efficiency.
Therefore intensity of rain scavenging of aerosol radioactive matter has been modeled (Fig. 2) by means of (1).
On (Fig. 2) dependence increase of efficiency of rain scavenging with increase of precipitation intensity has been shown. Thus the intensity increase of rain scavenging with stream increase dispersion at identical intensity of precipitation has been watched. It has been explained by increase of a free surface of drops and smaller velocity of the flowing round airflow. This repulsion of radioactive particles reduces by trajectories of flight of a drop.
Conclusions: 1. Existence of charge on a surface of a radioactive particle has been considered. It is essential only to fine particles with rrp& lt-0,1 micron. For coarser particles the taking into account of charge in the range up to 104 elementary charges can be neglected. 2. For particles ofthe average sizes (0,1 10 microns) purification intensity of the atmosphere with precipitation will be the smallest. These particles are the bulk of a radioactive aerosol in the atmosphere. 3. The purification intensity ofthe atmosphere of radioactive particles will be the maximal at the large area of a free surface of drops and low velocity of the flowing round airflow of fine precipitation.
References:
1. NRA. 2011. Readings of Environmental Radiation Level by emergency monitoring (March 2011). http: //radioactivity. nsr. go. jp/en/list/207/list-201 103. html [Accessed 19. 11. 15.].
2. Fuchs N. A. The Mechanics of Aerosols, Dover Publications, 1989. — P. 421.
3. Greenfield S. M. Rain scavenging of radioactive particulate matter from the atmosphere. Journal ofMeteorology. -1957. — № 14, — P. 115−123, doi: 10. 1175/1520−0469 (1957)014.
4. Slinn W. G. N. Precipitation scavenging, in: Atmospheric Science and Power Production, edited by: Randerson, D., Doc. D0E/TIC-27 601, Tech. Inf. Cent., Off. Of Sci. and Tech. Inf U. S. Dep. Of Energy, Washington, D. C. 1984. — P. 466−532.
5. Kashparov V. A., Lundin S. M., Khomutinin Yu. V. Soil contamination with 90Sr in the near zone of the Chernobyl accident. J. Environ. Radioactiv. — 2001. — № 56. P. 285−298. doi: 10. 1016/S0265−931X (00)00207−1.
6. Kim Y. -H., Yiacoumi S., Tsouris C. Surface charge accumulation of particles containing radionuclides in open air, J. Environ. Radioactiv. — 2015. — № 143. P. 91−99, doi: 10. 1016/j. jenvrad. 2015. 02. 017.
7. Pauthenier M., Cochet R. Evolution d'-une gouttelette d'-ean chargee dans un nuage a temperature positive, Rev. gen. elec., 1953. — № 62. P. 255−262.
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Madenov Berdimurat Dauletmuratovich, Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan, junior scientific researcher, the Laboratory of Phosphate fertilizers E-mail: igic@rambler. ru Namazov Shafoat Sattarovich, Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan, Doctor of Sciences, Professor, head of the Laboratory of Phosphate fertilizers E-mail: igic@rambler. ru Seytnazarov Atanazar Reypnazarovich, Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan, Doctor of Science, leading specialist of the Laboratory of Phosphate fertilizers E-mail: igic@rambler. ru Reymov Ahmed Mambetkarimovich, Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan, Doctor of Science, Deputy of scientific study of the Institute of General and Inorganic Chemistry of AS RUz
E-mail: igic@rambler. ru Beglov Boris Mihaylovich,
Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan, academician of AS RUz, Doctor of Sciences, Professor, leading specialist of the Laboratory of Phosphate fertilizers
E-mail: begloff@mail. ru
Nitrogen-phosphate fertilizers based on ammonium nitrate melt and nodule phosphorite from Kara-Kalpakistan
Abstract: The investigations on obtaining of the thermostable nitrogen-phosphate fertilizers based on ammonium nitrate melt and Kara-Kalpakistan'-s phosphorite at weight ratios of ammonium nitrate: phosphorite flour from 100:

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