RU2620449C2 - Method for determining location of point gamma-ray source on ground - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method for determining location of the point gamma-ray source on the ground is to measure the dose rates of the gamma- ray during the flight, herewith the measurement is performed by the gamma-ray detector with the collimator in the form of a circular conical slit placed on the basis of the unmanned aircraft, in three successive stages : vertical take-off of the aircraft at the determined point on the ground to the height at which the radiation sensor is triggered, followed by the geometric determination of the area in the form of a ring centered at the take-off point; the second take-off from any point inside the first ring with the repetition of all operations of the first stage and the geometric definition of the intersection points of the two rings; approaching at low altitude to one of the points identified in the second stage for the exact determination of the source location on the ground.

EFFECT: increased search efficiency of the point source ionizing radiation on the large territory.

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Description

The invention relates to the field of detection of radiation conditions, and in particular to methods of searching and detecting sources of ionizing radiation (III), and is intended to search for point sources of gamma radiation.

Search and localization of point sources of gamma radiation of high activity is one of the important tasks in eliminating the consequences of radiation accidents. These can be fragments of structural elements of nuclear reactors, storage facilities for radioactive waste, spent fuel elements, and other small-sized radioactive objects. In addition, there are cases of loss of control over sources of ionizing radiation as a result of unauthorized disposal, loss or theft [1].

A known method for determining the position of a point source of gamma radiation. Its essence lies in the fact that pre-measure the dose rate of gamma radiation at points along the perimeter of the area within which the source is located. The points with the smallest, largest and two with average values of the dose rate are determined. Then two straight-line reconnaissance routes are planned, which are segments connecting the point of minimum dose rate with the points where average values are observed. At points lying on these segments, measurements of dose rate values are carried out, and dependences of dose rate changes along reconnaissance routes are constructed. Using the established dependencies, points with maximum values are determined on the routes, and at these points two perpendiculars to the corresponding route lines are built. The intersection point of these perpendiculars is found, which indicates the position of the ionizing radiation source [1].

The disadvantages of this method include the complexity of the search and preparation for it. Also, the fact of radiation exposure is not ruled out, since the movement is carried out near the III. In addition, there may be cases of searching for III in difficult terrain, for example, in mountains or swamps. In case of major radiation accidents, such as the destruction of a nuclear power unit, the search for point sources in a radioactively contaminated area will take a long time with a significant health hazard for the dosimeter.

There is another way to search and detect sources of gamma radiation in conditions of uneven radioactive contamination. The method consists in registering radiation with three detectors located on the platform of a mobile robot (MP). One of the detection units is a search one and consists of two detectors separated by a screen. The second detection unit is detectable. It is a detector located on the MP manipulator [2].

The disadvantage of this method is the long search time of a point III in a large area. In addition, the terrain significantly affects the movement of MP. Large folds of terrain and ravines completely hamper the movement of the MP and make it difficult to control.

At present, to solve the problems of searching and detecting sources of gamma radiation in the arsenal of the compounds and military units of the Russian Chemical Forces Defense Forces, designed to eliminate the consequences of radiation accidents, the complex of radiation reconnaissance and search of IIR (KRPI) adopted in 2000 is located. The complex includes aerial and ground-based radiation reconnaissance equipment, which is mounted on the basis of the Mi-8 and BTR-80 helicopters [2]. The method of searching and determining the location of local sources of gamma-neutron radiation, implemented in this complex, is selected as a prototype, as it bears the greatest resemblance to the claimed method. The complex is effective for searching highly active III in a large area. The technical characteristics of the helicopter do not allow descent to the ground to measure dose rate. Aerial radiation reconnaissance equipment is not sensitive to inactive III at high altitude. In addition, a significant disadvantage of the complex is its high cost and large weight and size characteristics.

The technical result achieved in the claimed invention is that the coordinates of the location of the point III are determined in hard-to-reach areas without involving manned aircraft.

The specified technical result is achieved in that the determination of the coordinates of the location of the point III is carried out using the target load installed on an unmanned aerial vehicle (UAV) of a helicopter type. The target load diagram is presented in figure 1. Measurement of the dose rate during the flight is carried out using a gamma-ray detector 1 with a collimator 2 in the form of a circular conical-shaped slit. Thus, radiation from a plot of land in the form of a ring, as shown in figure 2, can enter the detector. Measurements are carried out in three successive stages. During measurements at the first stage, an UAV with a target load carries out a vertical rise from a given point on the ground until it reaches the height at which the radiation detection sensor is triggered. When lifting, the UAV scans a portion of the earth's surface along expanding concentric rings. With increasing flight altitude, the radius of the ring increases proportionally. In the event of a sharp increase in the dose rate, the UAV's altitude is fixed and, using geometric constructions, a ring is determined on the ground with the center at the take-off point, which in turn passes through the point where the source is located. In the future, to determine the location of the point source, the second measurement stage is carried out, where the UAV flies along a vertical path above a point chosen arbitrarily inside the first ring with the repetition of all operations of the first stage. As a result of the second flight, a second ring is constructed, also passing through the source. The intersection points of the two rings, as shown in figure 3, are points of the likely location of the source. For a final determination of which of the two points the source is located, it is enough to fly at a low height to one of them and establish the fact of the presence or absence of a source in it.

The described method can also be implemented on a uniform radioactively contaminated area (REM). In this case, in the absence of III, the measurement results will change in accordance with the dependence of the dose rate on the height, which is shown in figure 4. This dependence is described by formula 1.

where P is the dose rate measured by the detector when located at a height h from the radioactively contaminated area, R / h;

k is a constant depending on the units of measurement. In the case when the pollution density σ is measured in MeV / (cm ² ⋅ s) and the exposure dose rate in R / h is considered, then k = 5.0910 ^-2 R ⋅ cm ³ ⋅ s / (h ⋅ MeV);

σ is the surface density of the contamination of the area, MeV / (cm ² ⋅ s);

σ _a , μ are the linear absorption and scattering coefficients of γ radiation in air, respectively, cm ^-1 ;

r is the radius of the ring, cm;

h is the height of the detector, cm;

E is the initial energy of gamma rays, MeV;

b is the width of the ring, see

If there is a point source in the REM site under study, the detector will record an excess of the dose rate that does not correspond to the dependence described by formula 1. On the graph, the moment of registration of the III will correspond to the extremum point, as shown in figure 5.

The determination of the location of a point source on a uniform REM is carried out similarly to the algorithm described above.

The proposed technical solution allows the operational search for a point source of ionizing radiation over a large area with relatively low material costs.

The invention is illustrated by the following drawings.

The figure 1 presents a diagram of the target load on the UAV, where

1 - gamma radiation detector;

2 - collimator.

The figure 2 presents a diagram of the scanning site.

The figure 3 presents a scheme for determining the location of III.

The figure 4 presents a graph of the dependence of the dose rate on the height of the detector on a uniform radioactively contaminated area.

The figure 5 presents a graph of the dependence of the dose rate on the height of the detector on a uniform radioactively contaminated area with a point source.

BIBLIOGRAPHY

1. Pat. 2481597 Russian Federation, IPC G01T 1/169. A method for determining the position of a point source of gamma radiation [Text] / Bykov A.V., Vasiliev A.V., Sadovnikov R.N., Tyryshkin S.N .; Applicant and patent holder Federal budget institution “33 Central Research Institute” of the Ministry of Defense of the Russian Federation / publication of a patent on 05/10/2013

2. Pat. 2195005 Russian Federation, IPC G01T 1/169. A method for searching and detecting sources of gamma radiation in conditions of uneven radioactive contamination [Text] / Solovy SN, Alimov NI, Perevozchikov AN; Glukhov Yu.A.; Andrievsky E.F .; Applicant and patent holder military unit 61469 / publication of the patent December 29, 2002

3. The Ministry of Defense of the Russian Federation. Order No. 569 On the adoption of the complex of radiation reconnaissance and the search for ionizing sources of the KIPI for supply to the RF Armed Forces [Text]: the order was approved by the First Deputy Defense Ministry on December 1, 2000. - M.: Ministry of Defense of the Russian Federation, 2000 .-- 3 p.

Claims (1)

A method for determining the location of a point source of gamma radiation on the ground, which consists in measuring the dose rate of gamma radiation during the flight, characterized in that the measurements are made by a gamma radiation detector with a collimator in the form of a circular conical-shaped slit located on the basis of an unmanned aerial vehicle, three consecutive stages: the vertical elevation of the apparatus from a given point on the ground until it reaches the height at which the radiation detection sensor is triggered, followed by geometric nical determining portion in a ring shape centered at take-off; the second rise from any point inside the first ring with the repetition of all operations of the first stage and the geometric determination of the intersection points of both rings; approach at low altitude to one of the points identified in the second stage, to accurately determine the location of the source on the ground.

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