RU2620333C1 - Method of administration of aircraft radiation surveys with the use of a helicopter-free helicopter of a helicopter type - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of airborne exploration of a terrain using a helicopter-type unmanned aerial vehicle is to measure the dose rate at a flight altitude and bring its value to the altitude of interest using the dose rate over the radioactively contaminated terrain from the measurement height. The determination of the magnitude of the reduction in the attenuation of gamma radiation by the air layer is carried out by establishing the dependence of the dose rate on the measurement height, compiled from the measurement results in a vertical flight above the surveyed radioactively contaminated terrain.

EFFECT: increasing the reliability of conducting radiation investigation of the terrain contaminated with radioactive substances.

3 dwg, 4 tbl

Description

1. The technical field to which the invention relates.

The invention relates to the field of detecting the radiation situation by technical means of aerial radiation reconnaissance of the terrain (VRRM) and can be used to create promising and use the existing technical means of VRRM.

2. The level of technology

A known method of conducting BPM, based on the registration of gamma rays by a detector located on the aircraft. The method is based on bringing the results of measurements of gamma radiation dose rate values at the height of radiation reconnaissance (RR) to a height of 1 m using recalculated altitude coefficients and is implemented in aircraft dose rate meters of the IMD-31 and IMD-32 type [1, 2].

However, the conversion factors significantly depend on the energy of gamma rays, the topography, the underlying surface, the state of the atmosphere (air temperature, humidity, etc.), vegetation cover and other factors [3]. Since the indicated parameters are either unknown or known with a certain error, the results of the conversion of the measured radiation levels have an error corresponding to a change in these parameters. Besides this, there are only a limited number of similar technical complexes of PP.

A known method of accounting for the attenuation factor K (h) of gamma radiation by an air layer, the thickness of which corresponds to the flight height of the aircraft, implemented in a specialized GO-21 aerial radiation reconnaissance complex, by manually setting the sub-band switch to fixed positions [4]. This method has low reliability, since information on the parameters of the emergency release, including the radionuclide composition and the spectrum of gamma radiation, as well as meteorological data, are not taken into account when measuring the dose rate.

There is a known method of conducting SRM in the area of an accident at a nuclear reactor with depressurization of the active zone, which consists in measuring the gamma radiation dose rate values at a flight altitude and bringing the values obtained to a height of 1 m above the earth's surface [5].

The specified method also has low reliability, since its implementation does not take into account errors due to the characteristics of the area of the RR (relief, underlying surface, meteorological conditions, etc.), which can significantly affect the results of exploration. Acceptable values of the measurement error due to the unknown radionuclide contamination composition are provided at relatively low survey heights. This makes it difficult to use this method in terrain conditions that differ from the plain. In addition, the considered method does not allow for air density, which leads to an additional measurement error.

This method is selected as a prototype, since it has the greatest similarity with the described method.

3. Disclosure of invention

от высоты h над радиоактивно загрязненной местностью (РЗМ). Зависимость

определяют при вертикальном полете во время нахождения беспилотного летательного аппарата в поле гамма-излучения над РЗМ. Данная особенность позволяет при ведении разведки учитывать ряд частных погрешностей измерения, зависящих от спектра гамма-излучения, состояния атмосферы, рельефа местности, вида подстилающей поверхности, наличия и высоты растительного покрова и других особенностей местности.The method of conducting VRM using an unmanned aerial vehicle of a helicopter type is to measure the gamma radiation dose rate at a height of flight and bring its value to the height of interest using the real dose rate dependence

from height h above radioactively contaminated area (REM). Dependence

determined during vertical flight while the unmanned aerial vehicle is in the gamma radiation field above the rare-earth metals. This feature allows for reconnaissance to take into account a number of particular measurement errors, depending on the gamma-ray spectrum, the state of the atmosphere, the terrain, the type of underlying surface, the presence and height of the vegetation cover and other terrain features.

The technical result is to increase the reliability of the management of the area contaminated with radioactive substances.

Currently, more than 40 countries of the world have their own nuclear industry, nuclear power plants, mobile, ship, research, space and other nuclear power plants. As practice shows, accidents at such radiation-hazardous facilities happen from the moment humanity began to use nuclear energy for its own purposes. This fact places high demands on the existing and developing systems and means of the RR both in reliability and in the speed of obtaining data on the parameters of radioactively contaminated areas and objects.

One of the main tasks of the local area’s location is to detect and most reliably determine the parameters of rare-earth metals and various objects in the shortest possible time, which will allow for timely and targeted activation of a set of measures to protect the population from the effects of ionizing radiation.

A significant increase in the efficiency of the RR is associated with the development of technical means of airborne missile defense. Among the advantages of these tools, one can single out the possibility of examining territories with any degree of radioactive contamination, the possibility of reconnaissance of terrain impassable for ground reconnaissance equipment, as well as a significant reduction in the time spent on gathering intelligence information.

At the same time, the methodological basis for the measurement of all existing airborne VRPM devices remains unchanged throughout the history of their development. Its essence lies in the fact that in order to determine the radiation dose rate at a certain point, it is necessary to measure the dose rate above this point at the flight altitude of an unmanned aerial vehicle and multiply the measured value by the magnitude of the attenuation of gamma radiation by the air layer between the flight altitude and the altitude under study. The magnitude of the attenuation factor K (h) shows the ratio of the desired dose rate to the measured

where K (h) is the magnitude of the attenuation of gamma radiation by an air layer;

- мощность дозы на интересующей высоте;

- dose rate at the height of interest;

- мощность дозы, измеренная на высоте полета.

- dose rate measured at flight altitude.

The magnitude of the attenuation factor will vary in accordance with the dependence of the dose rate over REM on the measurement height. At the same time, many factors will influence this dependence, the most significant of which are the energy of gamma rays, the state of the atmosphere, the topography, the underlying surface, the vegetation cover, as well as the presence and characteristics of objects in the surveyed area.

When implementing analog methods, these parameters are either not taken into account or are taken into account with a certain error, therefore, the results of the conversion of the measured dose rates have a significant error.

So, for example, in the method selected as a prototype, it is proposed to determine the attenuation factor K (h) using the expression for the dose rate from a flat isotropic gamma radiation source located in an infinite homogeneous air-equivalent medium, converted for the case of complex radionuclide contamination [5 ]

Where

K _p - constant, depending on the choice of units;

A _i is the activity of the i-th isotope in the reactor core, Bq;

K _vi is the output of the ith isotope from the reactor core in an accident of the first class, rel. units;

K _γij is the differential quantum yield per decay for the jth line of the i-th isotope;

E _ij is the energy of quanta of the jth line of the i-th isotope, MeV;

σ _{a ij} is the linear coefficient of energy absorption, m ^-1 ;

S is the area of radioactive contamination, m ² ;

h - reconnaissance height, m;

μ _ij is the linear attenuation coefficient of the radiation, m ^-1 ;

r is the distance from the elementary radiation source to the point of location of the radiation detector, m;

B _d - dose accumulation factor;

R is the distance from the projection point of the radiation detector to the surface to the elementary radiation source, m

Calculation of K (h) using formulas (1) and (2) does not take into account the totality of factors characterizing the real conditions in the area of reconnaissance, which can significantly affect the measurement results.

The gamma radiation field above an area contaminated with radioactive isotopes differs from the gamma field of an idealized flat isotropic source located in an infinite air environment. This difference is due to [6]:

- the influence of the substance of the underlying surface, which differs in density and atomic composition from air;

- the presence of irregularities in the underlying surface;

- the presence of vegetation;

- a change in air density depending on temperature, pressure and humidity in real conditions.

Consider the influence of these factors on the field of gamma radiation over REM in natural conditions.

When the ionizing radiation source is located at the interface, consisting of substances of different densities with a small atomic number Z, in a layer with a lower density (the case of the water-air and ground-air interface), the dose rate of gamma radiation of the source near it (μr <1 ) more than for a homogeneous medium, due to an increase in backscattering from a denser medium. With increasing distance from the source (μr >> 1), the difference in dose rate values for these cases decreases.

для плоского изотропного источника и энергии E=1,25 МэВ с учетом подстилающей поверхности (сплошная линия) и без нее (пунктирная линия) от радиуса плоского круглого источника R для разных высот измерения: h=1 м (линия 1.1), h=10 м (линия 1.2), h=50 м (линия 1.3), h=100 м (линия 1.4).The figure 1 shows the relationship

for a planar isotropic source and energy E = 1.25 MeV, taking into account the underlying surface (solid line) and without it (dashed line) from the radius of a flat circular source R for different measurement heights: h = 1 m (line 1.1), h = 10 m (line 1.2), h = 50 m (line 1.3), h = 100 m (line 1.4).

показывает вклад мощности дозы от круглой площадки радиусом R в суммарную мощность дозы от площадки бесконечного радиуса.Attitude

shows the contribution of the dose rate from a round site of radius R to the total dose rate from a site of infinite radius.

From figure 1 it is seen that the underlying surface affects the value of the dose rate above the radiating surface, especially for small heights, the error in measuring the dose rate in this case reaches 15%.

The effect of the microrelief on the distribution of gamma radiation in the surface layer of the atmosphere is mainly due to the screening of the protrusions of the soil of the radiation arriving at the observation point from individual zones.

Consider the elementary site dS, located at a distance R from the projection of the observation point on the earth's surface. The angle between the plane of the earth's surface and the line connecting the site dS with the observation point is denoted by β, i.e. β = arcctg (R / h), where h is the height of the observation point.

The factor taking into account the influence of the microrelief on the radiation of the elementary site dS (or a point source located on this site) is denoted by

- мощность дозы излучения от элементарной площадки dS при наличии микрорельефа;Where

- radiation dose rate from the elementary site dS in the presence of a microrelief;

- мощность дозы излучения от элементарной площадки dS при отсутствии микрорельефа.

- radiation dose rate from the elementary site dS in the absence of a microrelief.

If, when calculating the effect of the microrelief, the function χ (β) introduced above is used, then the correction coefficient K _Н (h), which takes into account the effect of earth irregularities on the dose rate of gamma radiation from the surface as a whole, can be expressed by the formula

where l (h, cos θ) is the angular distribution of the dose rate;

χ '(cos θ) = χ (β); for cos θ <0, it is assumed that χ '(cos θ) = 1;

In work [3], descriptions of calculations and model experiments to determine the effect of the microrelief on the gamma radiation field over rare-earth metals are given, the main results of which are presented in table 1.

The gamma field above the rare-earth metals covered with grass or forest cover differs from the gamma field of a site free of vegetation. This difference is due to the shielding ability of biomass covering the contaminated surface.

To calculate the effect of vegetation on the reliability of the RR, we used a model of radioactive contamination with a uniform distribution of radioactive fallout on the earth's surface.

We assume that there are no fundamental differences between the influence of grass cover, shrubs and forest stands on the gamma field. The difference will only be in the quantity and nature of the distribution of biomass in the area.

The absorbing medium, if the airborne radioactive waste is conducted over a contaminated area covered with forest vegetation, consists of two layers: an air layer (almost equal in mass to the air layer from the surface of the earth to the measurement point) and the wood layer. Then the dose rate at the measurement point is determined by the formula

- мощность дозы, измеренная на высоте полета;Where

- dose rate measured at flight altitude;

- мощность дозы на интересующей высоте;

- dose rate at the height of interest;

K (h) is the magnitude of the attenuation of gamma radiation by a layer of air;

K _l (h) is the dose rate shielding coefficient at the point of measurement with a layer of wood.

Table 2 shows the values of the gamma-radiation shielding coefficients for an infinite surface source and plantings of different types and ages at E = 0.7 MeV. Shielding factors mainly depend on tree sizes and density of forest stands. The size of the trees is characterized by age, and the density of plantings - by the degree of bonitet (growth conditions).

Table 2 shows that forest vegetation can attenuate gamma radiation (E = 0.7 MeV) up to three times. Thus, the shielding ability of forest vegetation can have a significant impact on the accuracy and reliability of intelligence obtained in the process of conducting aerial PP.

Let us consider the effect of the state of the atmosphere on the gamma-field over REM.

As you know, the air density ρ depends on the pressure p, temperature t and humidity W. In turn, the attenuation coefficient of gamma radiation by air and, accordingly, the dose rate at a height h above REM depends on the air density.

The figure 2 shows the dependence of the conversion coefficients K _B (h), taking into account the state of the atmosphere, on humidity (W, g / m ³ ), density (ρ, g / m ³ ), pressure (p, mmHg at t = 0 ° С and t = 20 ° С) and temperature (t, ° С at p = 760 mm Hg) of air for dose rate when measured at different heights: h = 100 m (line 2.1), h = 200 m (line 2.2), h = 300 m (line 2.3).

From figure 2 it can be seen that the conversion coefficient K _B (h) for the dose rate changes slightly when the water content in the air changes (with thick fog, the humidity is ~ 1.0 g / m ³ , with heavy rain ~ 4.0 g / m ³ ) A temperature shift from minus 30 to 30 ° C changes the value of the conversion factor by 25-60%, and a drop or increase in pressure by 50 mm Hg - by 8-20% depending on the height of the PP. The change in this coefficient for the intensity of primary gamma radiation is even more significant. For measurements in mountainous regions, where the earth’s surface is at a higher altitude, accounting for pressure is even more significant [3].

, мощность дозы на земной поверхности (например, на высоте h_o=1 м)Using the above data on the influence of real conditions on the gamma radiation field, it can be determined by the dose rate measured at the flight altitude

dose rate on the earth's surface (for example, at a height of h _o = 1 m)

- мощность дозы, измеренная на высоте полета;Where

- dose rate measured at flight altitude;

- пересчетный высотный коэффициент с высоты h на высоту h_o для идеально ровной поверхности и стандартной атмосферы;

- recalculated altitude coefficient from height h to height h _o for a perfectly flat surface and a standard atmosphere;

K _P (h) - correction factor, taking into account the influence of the underlying surface;

K _N (h) is a correction factor that takes into account the effect of unevenness on the earth's surface;

K _L (h) is a correction factor that takes into account the effect of vegetation (mainly forest) cover;

To _p (h) is a correction factor that takes into account the influence of atmospheric pressure;

K _T (h) is a correction factor that takes into account the influence of air temperature;

K _W (h) is a correction factor that takes into account the effect of air humidity.

According to the results of calculations of the effect of real conditions on the results of aerial PP, the gamma-radiation fields over REM are modeled as close as possible to the real ones by taking into account the influence of the considered factors on the distribution of gamma-radiation.

, мР/ч) от высоты измерения (h, м) для крайних случаев, когда исследуемые факторы максимально (линия 3.1) и минимально (линия 3.3) ослабляют гамма-излучение от РЗМ, а также аналогичная зависимость для идеализированного плоского изотропного источника, находящегося в бесконечной воздушной среде (линия 3.3). Все три случая рассмотрены для одинаковой равномерной площадной плотности радиоактивного загрязнения.The figure 3 presents the dependence of the dose rate (

, mR / h) on the measurement height (h, m) for extreme cases when the studied factors maximally (line 3.1) and minimally (line 3.3) attenuate gamma radiation from rare-earth metals, as well as a similar dependence for an idealized planar isotropic source located in infinite air environment (line 3.3). All three cases were considered for the same uniform areal density of radioactive contamination.

Figure 3 shows that the dependence of the dose rate on height, characterizing all possible variants of the transformation of the field of ionizing radiation by the terrain, will pass between line 3.1 and line 3.3.

Table 3 shows the values of relative errors for cases when the real conditions of the airborne radioactive receiver maximally and minimally weaken the gamma radiation from rare earth metals at various heights of reconnaissance.

4. The implementation of the invention

от высоты h над радиоактивно загрязненной местностью (РЗМ). Зависимость

определяют при вертикальном полете во время нахождения беспилотного летательного аппарата в поле гамма-излучения над РЗМ. Данная особенность позволяет при ведении разведки учитывать ряд частных погрешностей измерения, зависящих от спектра гамма-излучения, состояния атмосферы, рельефа местности, вида подстилающей поверхности, наличия и высоты растительного покрова и других особенностей местности.The method of conducting VRM using an unmanned aerial vehicle of a helicopter type is to measure the gamma radiation dose rate at a height of flight and bring its value to the height of interest using the real dose rate dependence

from height h above radioactively contaminated area (REM). Dependence

determined during vertical flight while the unmanned aerial vehicle is in the gamma radiation field above the rare-earth metals. This feature allows for reconnaissance to take into account a number of particular measurement errors, depending on the gamma-ray spectrum, the state of the atmosphere, the terrain, the type of underlying surface, the presence and height of the vegetation cover and other terrain features.

от высоты h над РЗМ. Для этого указанную зависимость

предложено определять при вертикальном полете беспилотного летательного аппарата во время его нахождения в поле гамма-излучения над обследуемой местностью путем измерения мощности дозы и соответствующей высоты на всей траектории вертикального полета от поверхности земли до максимальной высоты, на которой планируется вести PP. Скорость взлета зависит от требуемой точности измерения и от времени измерения измерителя мощности дозы. После этого полученную зависимость предложено аппроксимировать и использовать для нахождения величины кратности ослабления ионизирующего излучения слоем воздуха между высотой измерения и высотой, для которой пересчитывается мощность дозы.To eliminate the above errors, it is proposed to bring the dose rate value measured at flight height to the dose rate at the height of interest using the real dose rate dependence

from height h above REM. For this, the indicated dependence

It is proposed to determine during vertical flight of an unmanned aerial vehicle while it is in the gamma radiation field above the surveyed area by measuring the dose rate and the corresponding height along the entire vertical flight path from the earth's surface to the maximum height at which PP is planned to be conducted. Take-off speed depends on the required measurement accuracy and on the measurement time of the dose rate meter. After that, it was proposed to approximate the obtained dependence and use it to find the magnitude of the attenuation coefficient of ionizing radiation by an air layer between the measurement height and the height for which the dose rate is recalculated.

In the future, with a significant change in the parameters affecting the dependence of the dose rate on the measurement height, in order to increase the reliability of the PP, it is necessary to repeat the vertical flight to make a more relevant dependence.

From figure 3 (line 3.1) it is seen that in the presence of a forest cover and a rugged topography, the dose rate with an increase in the measurement height initially increases (from the surface of the earth to the height of the forest cover), then decreases. In this case, to increase the reliability, it is necessary to approximate the dependence of the dose rate on the height of its measurement at two intervals of heights. In addition, in the presence of forest cover, radioactive substances immediately after precipitation will be concentrated in the upper layer of the crown, then, under the influence of precipitation and wind, the pollution density will be transferred to the earth's surface, after which radioactive particles will penetrate into the soil. Therefore, in the presence of forest cover, it is necessary to distinguish between dependencies that describe the change in dose rate with a change in measurement height for areas separated by the upper boundary of the forest cover.

To determine the number of points for measuring the dose rate for vertical flight, the dependences of the relative standard deviation of the approximation on the number of points for measuring the dose rate for vertical flight at an altitude of 300 m were compiled. These dependences were calculated for the most common conditions, the average values of the calculation results are presented in table 4 .

Table 4

Thus, the analysis showed that a set of factors characterizing the actual conditions of the SRM is capable of significantly affecting the measurement results, both overstating and underestimating them. Existing methods of conducting BPM may have a significant error, since in their implementation not all of these features are taken into account. The proposed method will significantly improve the accuracy of the RR of the terrain, which will maximally reliably determine the parameters of rare earth metals and various objects in the shortest possible time and thus promptly and purposefully put in place a set of measures to protect the population from exposure to ionizing radiation.

5. Brief Description of the Drawings

для плоского изотропного источника и энергии E=1,25 МэВ с учетом подстилающей поверхности (сплошная линия) и без нее (пунктирная линия) от радиуса плоского круглого источника R для разных высот измерения:The figure 1 shows the relationship

for a planar isotropic source and energy E = 1.25 MeV, taking into account the underlying surface (solid line) and without it (dashed line) from the radius of a circular circular source R for different measurement heights:

1.1 h = 1 m

1.2 h = 10 m

1.3 h = 50 m

1.4 h = 100 m

показывает вклад мощности дозы от круглой площадки радиусом R в суммарную мощность дозы от площадки бесконечного радиуса.Attitude

shows the contribution of the dose rate from a round site of radius R to the total dose rate from a site of infinite radius.

From figure 1 it is seen that the underlying surface affects the value of the dose rate above the radiating surface, especially for small heights, the error in measuring the dose rate in this case reaches 15%.

The figure 2 shows the dependence of the conversion coefficients K _B (h), taking into account the state of the atmosphere, on humidity (W, g / m ³ ), density (ρ, g / m ³ ), pressure (p, mmHg at t = 0 ° С and t = 20 ° С) and temperature (t, ° С at p = 760 mm Hg) of air for dose rate when measured at different heights:

2.1 h = 100 m

2.2 h = 200 m

2.3 h = 300 m

From figure 2 it can be seen that the conversion coefficient K _B (h) for the dose rate changes slightly when the water content in the air changes (with thick fog, the humidity is ~ 1.0 g / m ³ , with heavy rain ~ 4.0 g / m ³ ) A temperature shift from minus 30 to 30 ° C changes the value of the conversion factor by 25-60%, and a drop or increase in pressure by 50 mm Hg - by 8-20% depending on the height of the PP. The change in this coefficient for the intensity of primary gamma radiation is even more significant. For measurements in mountainous regions, where the surface of the earth is at a higher altitude, accounting for pressure is even more significant.

, мР/ч) от высоты измерения (h, м) для крайних случаев, когда исследуемые факторы максимально (линия 3.1) и минимально (линия 3.3) ослабляют гамма-излучение от РЗМ, а также аналогичная зависимость для идеализированного плоского изотропного источника, находящегося в бесконечной воздушной среде (линия 3.3). Все три случая рассмотрены для одинаковой равномерной площадной плотности радиоактивного загрязнения.The figure 3 presents the dependence of the dose rate (

, mR / h) on the measurement height (h, m) for extreme cases when the studied factors maximally (line 3.1) and minimally (line 3.3) attenuate gamma radiation from rare-earth metals, as well as a similar dependence for an idealized planar isotropic source located in infinite air environment (line 3.3). All three cases were considered for the same uniform areal density of radioactive contamination.

Figure 3 shows that the dependence of the dose rate on height, characterizing all possible variants of the transformation of the field of ionizing radiation by the terrain, will pass between line 3.1 and line 3.3.

BIBLIOGRAPHY

1. Meter dose rate IMD-31. Technical description and instruction manual. - 132 p.

2. The complex IMD-32. Technical description and user manual ЖШ1.289.459 ТО. - M.: SIC SNIIP, 1997 .-- 85 p.

3. Israel Yu.A., Stukin E.D. Gamma radiation from radioactive fallout. - M .: Atomizdat, 1967 .-- 224 p.

4. Technical description and operating instructions for the GO-21 device. - 87 p.

5. Pat. 2554618 RF, IPC ⁷ G01T 1/169. The method of conducting airborne radiation reconnaissance. / R.N. Sadovnikov, D.V. Frolov; Applicant and patent holder FGBU 33TSNIIII MO RF. - No. 2013154167/28, 2001113992; claimed 05.12.2013 05.22.01; published on June 27, 2015, bull. Number 18. - 9 p.

6. Israel Yu.A. "Proceedings of the USSR Academy of Sciences, geographic series", No. 7, 1964

Claims (1)

A method of conducting aerial radiation reconnaissance of an area using an unmanned aerial vehicle of a helicopter type, which consists in measuring a dose rate at a flight altitude and bringing it to a height of interest using the dependence of the dose rate over a radioactively contaminated area on the measurement height, characterized in that the attenuation factor is gamma radiation with a layer of air is carried out by establishing the dependence of the dose rate on the measurement height, compiled by m measurement in vertical flight over the surveyed radioactively contaminated area.

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