阅读说明：本技术 反演污染区虚拟点位置和边界的技术方法及设备 (Technical method and equipment for inverting position and boundary of virtual point in polluted area ) 是由 田自宁 刘林月 龙斌 陈亮 刘文彪 王雪梅 韩斌 田言杰 李惠彬 王保丹 欧阳晓 于 2021-07-14 设计创作，主要内容包括：本发明公开了反演污染区虚拟点位置和边界的技术方法及设备,包括热区虚拟点源、沙土、沙土衰减层、探测器、虚拟点探测器、面源、面源的虚拟点源、地面和空气,所述虚拟点源为体源或面源或混合源的虚拟点源,其发射的射线要经过沙土、地面、空气才能到达探测器,所述沙土为虚拟点源的埋深沙土,其位置在虚拟点源与探测器之间,本发明利用就地HPGeγ谱仪有效前面积原理建立方程组,通过解方程获得虚拟点位置,从而进一步反演污染区边界参数,该方法实用性较强,本发明由于使用了CZT探测器,密度高,体积小,在1.0m距离可视为点探测器,本发明借助两层和目标对象一致的沙土衰减层,建立了方程组,达到测量目标参数的目的。(The invention discloses a technical method and equipment for inverting the position and boundary of a virtual point in a pollution area, which comprises a hot area virtual point source, sandy soil, a sandy soil attenuation layer, a detector, a virtual point detector, a surface source, a virtual point source of the surface source, ground and air, wherein the virtual point source is a virtual point source of a source or a surface source or a mixed source, the emitted rays can reach the detector only through the sandy soil, the ground and the air, the sandy soil is buried sandy soil of the virtual point source, and the position of the sandy soil is between the virtual point source and the detector, an equation set is established by utilizing the effective front area principle of an in-situ HPGe gamma spectrometer, and the virtual point position is obtained by solving the equation, so that the boundary parameter of the pollution area is further inverted, the method has strong practicability, because the CZT detector is used, the density is high, the volume is small, the detector can be regarded as a point detector at a distance of 1.0m, the invention utilizes two sandy soil attenuation layers consistent with a target object, an equation set is established to achieve the purpose of measuring target parameters.)

1. The equipment for inverting the positions and boundaries of virtual points in a pollution area comprises a virtual point source (1) and is characterized in that: the virtual point source (1) is a virtual point source of a source or a surface source or a mixed source, rays emitted by the virtual point source can reach the detector (4) only through sandy soil (2), the ground (8) and air (9), the sandy soil (2) is buried sandy soil of the virtual point source, the thickness of the sandy soil is a parameter to be required, and the position of the sandy soil is between the virtual point source (1) and the detector (4); the sandy soil (2) and the sandy soil attenuation layer (3) have the same components, and the position of the sandy soil attenuation layer is between the sandy soil (2) and the detector (4); in a detection mode of a sandy soil surface pollution area, a surface source (6) is placed at a certain position below the detector (4), and the radius of the surface source (6) is a parameter to be obtained.

2. The apparatus for inverting locations and boundaries of virtual points in a contamination zone of claim 1, wherein: the sandy soil attenuation layer (3) is two layers with the same thickness.

3. The apparatus for inverting locations and boundaries of virtual points in a contamination zone of claim 1, wherein: in a detection mode of a certain buried depth pollution area, the detector (4) is an in-situ HPGe gamma spectrometer, and the position of a virtual point detector (5) is generally given by experimental calibration or a semi-empirical formula.

4. The apparatus for inverting locations and boundaries of virtual points in a contamination zone of claim 1, wherein: a virtual point source (7) of the surface source is arranged below the surface source (6), and the detector (4) can be a CZT detector or a ground HPGe gamma spectrometer in the measurement mode.

5. The technical method for inverting the positions and the boundaries of the virtual points in the polluted area is characterized by comprising the following steps of: the technical method comprises the following operation steps:

the method comprises the following steps: scanning the position of a virtual point source (1) in a certain buried depth pollution area (hot area) and calculating the activity;

in the in-situ gamma spectrometer measurement, a measurement object is generally positioned under the sand and soil on the ground, the measurement object can be a single source or a surface source or a point source, or can be a plurality of sources or surface sources or point sources positioned at different depths, or a mixed source of the sources; meanwhile, the shape of the source or the surface source is indefinite, the measuring object is extremely complex, and all the whole source items are virtualized into a point source, so that the measurement of the source items is converted into the measurement of a virtual point source (1);

step two: let the buried depth of the virtual point source 1 be d, the activity be A (Bq), and the gamma ray intensity be P_γThe effective front area of the HPGe detector (4) to the gamma ray (energy is E) of the characteristic of the radioactive source is S₀(ii) a The linear attenuation coefficient of the sandy soil (2) to the gamma ray is mu_s(ii) a In order to achieve the purpose of measurement, an equation set is established, and a sandy soil attenuation layer (3) is required to be added between sandy soil (2) and a detector (4);

step three: measuring the thicknesses of the sand attenuation layers (3) which are respectively placed at two times as x and 2 x; the counting rates of the characteristic gamma-ray total energy peaks of a certain nuclide measured twice are respectively n₁And n₂(ii) a According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀For the virtual point detector position, the formula (1) is divided by the formula (2):

the solution of formula (3) is:

the general virtual point detector (5) is at a distance d from the end cap of the detector₀Can be expressed as:

wherein RD and HD are radius and thickness of the detector, and linear attenuation coefficient and density are of the detector crystal;

step four: the thickness x of the sand soil attenuation layer 3 is 2.5cm, and the position of a virtual point detector (5) of the coaxial HPGe detector according to the reference document is d₀4.31cm, the linear attenuation coefficient of the standard substance is mu_s＝0.286；²⁴¹The distance between the Am-81# point source and the detector (4) is 20cm, and the actual thickness of the sandy soil (2) is 2.5 cm; the counting rate is 16.23cps when one sand attenuation layer (3) is arranged, the counting rate is 4.86cps when two sand attenuation layers (3) are arranged, and n is₁/n₂16.23/4.86 ═ 3.34; the thickness d of the sandy soil (2) can be calculated by substituting the data into the formula (4), and the difference between the thickness d of the sandy soil (2) and the actual thickness d of the sandy soil is 0.3cm (12%), so that the technical method can effectively search and measure the position of the virtual point source (1);

step five: when the position of the virtual point source (1) is known, the activity of the virtual point source can be obtained by using a standard point source relative measurement method; when a standard point source is buried into sand soil with the depth d, the activity concentration is denoted as Act (Std), the count C is denoted as C (Std), and the activity concentration Act (u) of the unknown virtual point source 1 is:

step six: sand surface contamination zone (hot zone) boundary inversion

The measurement object sandy soil surface pollution area (hot area) can be generally simplified into a surface source (6), and the measurement of the surface source (6) can be converted into the measurement of a virtual point source (7) of the surface source, such as a measurement model shown in fig. 3;

step seven: the CZT detector (4) and the in-situ HPGe detector (4) are used twice respectively to measure the characteristic gamma ray full energy peak counting rate of a certain nuclide to be n respectively₁And n₂(ii) a The linear attenuation coefficient of air (9) to gamma rays is mu_a(ii) a According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀The position of a virtual point detector (5) of the CZT detector (4) can be generally set to 0; d₀₁The virtual point detector (5) position for the in situ gamma spectrometer 335A; dividing formula (7) by formula (8):

the solution (9) has:

6. the technical method for inverting the position and the boundary of the virtual point of the polluted region according to claim 5, wherein the technical method comprises the following steps: in the fifth step, the counting of the standard point source needs to be measured, namely, the measurement is performed once, the unknown virtual point source (1) needs to be measured three times according to the mode, therefore, the activity of the unknown virtual point source (1) needs to be determined four times in total, for the radioactivity measurement, a measurement object can be converted into the measurement of the virtual point source (1), so that the complex measurement object can be simply processed, the measurement analysis is performed on the virtual point source (1), the position and activity information of the virtual point source (1) is researched, and the position and activity information of the source and the surface source is further researched.

7. The technical method for inverting the position and the boundary of the virtual point of the polluted region according to claim 5, wherein the technical method comprises the following steps: in the sixth step, the distance between the virtual point source (7) of the surface source and the surface source (6) is d, and the parameter is generally measured twice.

Technical Field

The invention relates to a position and boundary calibration technology of a source item of a neutral source or a surface source or a mixed source in a pollution area in the field of nuclear technology application, in particular to a technical method and equipment for inverting the position and the boundary of a virtual point in the pollution area.

Background

In-situ gamma spectrometry, the measurement object is typically located on the surface of or under sand. The measuring object can be a surface source or a point source, or can be several surface sources or point sources located at different depths, or a mixed source of the surface sources and the point sources; meanwhile, the shape of the body source or the surface source is not fixed, and the distribution is extremely complex. At present, the measurement of position boundary and activity concentration of the system at home and abroad cannot be solved well at all. This problem is slowly solved as the virtual point source principle is proposed. The subject is a solution and a technical method which are provided based on the virtual point source principle aiming at the problem. The general idea is to virtualize all the above source items into a point source, so that the measurement of the source items is converted into the measurement of a virtual point source.

Aiming at the problems, a local gamma spectrometer is mainly used for fixed-point measurement or scanning measurement at a certain height at home and abroad. Due to the complex source item condition, the detection efficiency is not accurate in scale, and the data error is large. In-situ sampling is also typically followed by comparative measurement analysis using laboratory gamma spectrometers.

The invention discloses a radioactive region determination method with the patent application number of ZL201410264383.3 based on the virtual point detector principle, and the method is completely different from the method in the invention in the principle that the virtual point source position is determined mainly based on the inverse distance square law, and the method is based on the effective front area principle of an in-situ HPGe gamma spectrometer. The invention adds CZT detector when measuring the virtual point source of the surface source, and adds two layers of sandy soil attenuation layers on the design for the measurement of the virtual point source of the source or the surface source or the mixed source with a certain buried depth.

Disclosure of Invention

The invention aims to provide a technical method and equipment for inverting the positions and boundaries of virtual points in a pollution area, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a technical method and apparatus for inverting the position and boundary of a virtual point in a pollution area comprises a virtual point source, wherein the virtual point source is a virtual point source of a source or a surface source or a mixed source, rays emitted by the virtual point source can reach a detector only through sandy soil, ground and air, the sandy soil is buried depth sandy soil of the virtual point source, the thickness of the sandy soil is a parameter to be required, and the position of the sandy soil is between the virtual point source and the detector; the sandy soil and the sandy soil attenuation layer have the same components, the position of the sandy soil attenuation layer is between the sandy soil and the detector, in a detection mode of a sandy soil surface pollution area, a certain position below the detector is provided with a surface source, and the radius of the surface source is a parameter to be obtained.

As a further scheme of the invention: the sandy soil attenuation layer is formed by two layers with the same thickness.

As a still further scheme of the invention: in a detection mode of a certain buried depth pollution area, the detector is an in-situ HPGe gamma spectrometer, and the position of the virtual point detector 5 is generally given by experimental calibration or a semi-empirical formula.

As a still further scheme of the invention: a virtual point source of the surface source is arranged below the surface source, and the detector can be a CZT detector or a ground HPGe gamma spectrometer in the measurement mode.

The technical method for inverting the positions and the boundaries of the virtual points in the polluted area comprises the following operation steps:

the method comprises the following steps: scanning the position of a virtual point source in a certain buried depth pollution area (hot area) and calculating the activity;

in-situ gamma spectrometry, the measurement object is generally located under the sand and soil on the ground, and the measurement object may be a single source or a surface source or a point source, or may be several sources or surface sources or point sources located at different depths, or a mixed source of the sources; meanwhile, the shape of the source or the surface source is not fixed, the measurement object is extremely complex, all the whole source items are virtualized into a point source, and thus the measurement of the source items is converted into the measurement of a virtual point source, as shown in fig. 1;

step two: let the buried depth of the virtual point source be d, the activity be A (Bq), and the gamma ray intensity be P_γThe effective front area of the HPGe detector 4 to the gamma ray with the characteristic of the radioactive source (the energy is E) is S₀(ii) a The linear attenuation coefficient of the sandy soil to the gamma ray is mu_s(ii) a In order to achieve the purpose of measurement, an equation set is established, and an attenuation layer is required to be added between sandy soil and a detector; its two-time laboratory measurement mode, as shown in fig. 2;

step three: measuring the thicknesses of the sand attenuation layers which are respectively placed at two times to be x and 2 x; the counting rates of the characteristic gamma-ray total energy peaks of a certain nuclide measured twice are respectively n₁And n₂. According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀For the virtual point detector position, the formula (1) is divided by the formula (2):

the solution of formula (3) is:

general virtual point detector distance d from detector end cap₀Can be expressed as:

where RD and HD are the radius and thickness of the detector, and the linear attenuation coefficient and density are of the detector crystal.

Step four: the thickness x of the arranged sandy soil attenuation layer is 2.5cm, and the position of the virtual point detector of the coaxial HPGe detector is d according to the reference document₀4.31cm, the linear attenuation coefficient of the standard substance is mu_s＝0.286。²⁴¹The distance between the Am-81# point source and the detector is 20cm, and the actual thickness of the sandy soil is 2.5 cm. The counting rate is 16.23cps when one sand attenuation layer is arranged, the counting rate is 4.86cps when two sand attenuation layers are arranged, and n is₁/n₂16.23/4.86-3.34. The sand thickness d can be calculated by substituting the data into the formula (4) to be 2.2cm and the actual difference is 0.3cm (12%), which proves that the technical method can effectively search and measure the position of the virtual point source.

Step five: when the position of the virtual point source is known, the activity can be obtained by using a standard point source relative measurement method. A standard point source can be used to be buried into sand soil with the depth d, the activity concentration is marked as Act (Std), the count C is marked as C (Std), and the activity concentration Act (u) of the unknown virtual point source 1 is:

step six: sand surface contamination zone (hot zone) boundary inversion

The measurement object sand surface contamination zone (hot zone) can be generally simplified into a surface source, and the surface source measurement can be converted into a virtual point source measurement of the surface source, such as the measurement model shown in fig. 3.

Step seven: the CZT detector and the in-situ HPGe detector are used twice respectively to measure the characteristic gamma ray full energy peak counting rate of a certain nuclide as n₁And n₂(ii) a The linear attenuation coefficient of air to gamma ray is mu_a(ii) a According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀The position of a virtual point detector of the CZT detector can be generally set to 0; d₀₁Is the virtual point detector position of the in situ gamma spectrometer 335A. Dividing formula (7) by formula (8):

the solution (9) has:

as a still further scheme of the invention: in the step five, the technical method needs to measure the counting of the standard point source, namely, the measurement is carried out once, and the unknown virtual point source needs to be measured three times according to the mode, so that the activity of the unknown virtual point source can be determined by measuring four times in total. For the radioactivity measurement, the measurement object can be converted into the measurement of the virtual point source 1, and thus the complicated measurement object can be simply processed. And (3) carrying out measurement analysis on the virtual point source, researching the position and activity information of the virtual point source 1, and further researching the position and activity information of the source and the surface source.

As a still further scheme of the invention: in the sixth step, the distance from the virtual point source of the surface source to the surface source is d, and the parameter is generally measured twice.

Compared with the prior art, the invention has the beneficial effects that:

1. the method utilizes the effective front area principle of the in-situ HPGe gamma spectrometer to establish an equation set, and obtains the position of a virtual point by solving the equation, thereby further inverting the boundary parameter of the pollution area;

2. because the CZT detector is used, the density is high, the volume is small, and the CZT detector can be regarded as a point detector at a distance of 1.0 m;

3. according to the invention, an equation set is established by means of two sandy soil attenuation layers consistent with a target object, so that the purpose of measuring target parameters is achieved.

Drawings

FIG. 1 is a schematic diagram of the hot zone virtual point source in-situ measurement in the technical method and equipment for inverting the position and boundary of the virtual point in the pollution zone.

FIG. 2 is a schematic diagram of a laboratory equivalent measurement of virtual point source positions in a hot zone in a technical method and equipment for inverting virtual point positions and boundaries of a pollution zone.

FIG. 3 is a schematic diagram of inversion of hot zone boundary measurements in a technical method and apparatus for inverting virtual point locations and boundaries of a polluted zone.

Shown in the figure: the system comprises a hot-area virtual point source 1, sandy soil 2, a sandy soil attenuation layer 3, a detector 4, a virtual point detector 5, a surface source 6, a surface source virtual point source 7, the ground 8 and air 9.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Referring to fig. 1-3, in the embodiment of the present invention, a technical method and an apparatus for inverting a virtual point position and a boundary of a pollution area include a hot area virtual point source 1, a sand 2, a sand attenuation layer 3, a detector 4, a virtual point detector 5, a surface source 6, a surface source virtual point source 7, a ground 8, and air 9, where the virtual point source 1 is a virtual point source of a source, a surface source, or a mixed source, a ray emitted therefrom can reach the detector 4 only through the sand 2, the ground 8, and the air 9, the sand 2 is buried depth sand of the virtual point source, the thickness of the sand 2 is a parameter to be required, and the position of the sand is between the virtual point source 1 and the detector 4; the sandy soil 2 and the sandy soil attenuation layer 3 have the same components, and the sandy soil attenuation layer 3 is two layers with the same thickness and is positioned between the sandy soil 2 and the detector 4; in a detection mode of a certain buried depth pollution area, the detector 4 is an in-situ HPGe gamma spectrometer, the position of a virtual point detector 5 is generally given by an experimental calibration or a semi-empirical formula, in the detection mode of the sand and soil surface pollution area, a surface source 6 is arranged at a certain position below the detector 4, the radius of the surface source 6 is a parameter to be solved, a virtual point source 7 of the surface source is arranged below the surface source 6, and in the measurement mode, the detector 4 can be a CZT detector or a terrestrial HPGe gamma spectrometer;

the technical method comprises the following operation steps:

the method comprises the following steps: scanning the position of a virtual point source 1 in a certain buried depth pollution area (hot area) and calculating the activity;

in-situ gamma spectrometry, the measurement object is generally located under the sand and soil on the ground, and the measurement object may be a single source or a surface source or a point source, or may be several sources or surface sources or point sources located at different depths, or a mixed source of the sources; meanwhile, the shape of the source or the surface source is not fixed, the measurement object is extremely complex, all the whole source items are virtualized into a point source, and thus the measurement of the source items is converted into the measurement of a virtual point source 1, as shown in fig. 1;

step two: let the buried depth of the virtual point source 1 be d, the activity be A (Bq), and the gamma ray intensity be P_γThe effective front area of the HPGe detector 4 to the gamma ray with the characteristic of the radioactive source (the energy is E) is S₀(ii) a Line attenuation system of sandy soil 2 to gamma rayNumber mu_s(ii) a In order to achieve the purpose of measurement, an equation set is established, and a sandy soil attenuation layer 3 is required to be added between sandy soil 2 and a detector 4; its two-time laboratory measurement mode, as shown in fig. 2;

step three: measuring the thicknesses of the sand attenuation layers 3 which are respectively placed at two times as x and 2 x; the counting rates of the characteristic gamma-ray total energy peaks of a certain nuclide measured twice are respectively n₁And n₂. According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀Is the virtual point detector position. Dividing formula (1) by formula (2):

the solution of formula (3) is:

the general virtual point detector 5 is at a distance d from the detector end cap₀Can be expressed as:

where RD and HD are the radius and thickness of the detector, and the linear attenuation coefficient and density are of the detector crystal.

Step four: the thickness 3x of the provided sandy soil attenuation layer is 2.5 cm. According to reference [2]]The position of a virtual point detector 5 of the coaxial HPGe detector is d₀＝4.31cm, linear attenuation coefficient of standard substance of mu_s0.286 (calculated according to the master's monton card calculation model).²⁴¹Am-81# point source is at a distance of 20cm from the detector 4, and the actual thickness of the sandy soil 2 is 2.5cm (assumed unknown). The counting rate is 16.23cps when one sand attenuation layer 3 is arranged, the counting rate is 4.86cps when two sand attenuation layers 3 are arranged, and n is₁/n₂16.23/4.86-3.34. The thickness d of the sandy soil 2 can be calculated to be 2.2cm by substituting the data into the formula (4), and the difference between the thickness d and the actual thickness d is 0.3cm (12%), so that the technical method can effectively search and measure the position of the virtual point source 1;

step five: when the position of the virtual point source 1 is known, the activity can be obtained by using a standard point source relative measurement method. A standard point source can be used to be buried into sandy soil with the depth d, the activity concentration is marked as Act (Std), the count C is marked as C (Std), and the activity concentration Act (u) of the unknown virtual point source 1 is:

the technical method needs to measure the counting of the standard point source, namely, the measurement is carried out once, the unknown virtual point source 1 needs to be measured three times according to the mode, and therefore, the activity of the unknown virtual point source 1 can be determined by measuring four times in total. For radioactivity measurement, we can convert the measurement object into the measurement of its virtual point source 1, so that the complex measurement object can be processed simply. Measuring and analyzing the virtual point source 1, researching the position and activity information of the virtual point source 1, and further researching the position and activity information of a source and a surface source of the virtual point source;

step six: sand surface contamination zone (hot zone) boundary inversion

The measurement object sandy soil surface contamination zone (hot zone) can be generally simplified into a surface source 6, and the measurement of the surface source 6 can be converted into the measurement of a virtual point source 7 of the surface source, such as the measurement model shown in fig. 3. Where the virtual point source 7 of the area source is at a distance d from the area source 6, two measurements are typically required to obtain this parameter.

Step seven: two times respectively makeMeasuring the characteristic gamma ray total energy peak counting rate of a certain nuclide as n respectively by using a CZT detector 4 and an in-situ HPGe detector 4₁And n₂(ii) a The linear attenuation coefficient of air 9 to gamma ray is mu_a(ii) a According to the attenuation law of the medium to gamma-rays, n₁And n₂The following relationships exist:

wherein d is₀The position of the virtual point detector 5, which is the CZT detector 4, may be set to 0 in general; d₀₁For the virtual point detector 5 position of the in situ gamma spectrometer 335A, the result is obtained by dividing equation (7) by equation (8):

the solution (9) has:

this project uses²⁴¹Am large area source 6 (equivalent radius is 45.5cm, activity is 8436400Bq) is subjected to a verification experiment; the CZT detector 4 used was of dimensions 15mm x 7.5mm, placed above the central axis of the large area source 6 with a detection distance of 100cm, measured 20000s, counted 727968 (0.23%). Because the CZT crystal is small and high in density, and is far away from a plane source, the CZT crystal can be directly virtualized into a point detector 5.

In situ gamma spectrometry 335A (crystal diameter 54.5mm, length 57.1mm), measurement 100s, count 45452 (0.49%). The position of the virtual point detector 5 of the in situ gamma spectrometer 335A is calculated by equation (10) to be 2.44cm (generally referring to the distance of the virtual point detector 5 from the end face of the detector). From the above data, the virtual point source can be obtained by the calculation of equation (9)The 7 position was 103.4cm, and this was substituted into a fitted curve of the area source radius and the virtual point position thereof (fitting function y-0.1083 · x²+27.83·^x-1676，R²0.998 where x is the virtual point source position/m and y is the area source radius/m) the available area source radius is 43.7cm, 1.8cm (4.0%) from the true value, confirming that the technique is effective.

The references and data are as follows:

[1]Z.B.Alfassi,F.Groppi,M.L.Bonardi,O.Presler,1U.German.SHORT COMMUNICATION.Journal of Radioanalytical and Nuclear Chemistry,Vol.268,No.3 (2006)639–640

[2] tianjingning, Liuwenbiao, Chenwei, Longbin, von Tiancheng, Wang Xuemei, and Ouyangping are based on virtual point source efficiency scale technology of virtual point detector, strong laser and particle beam in 3 months, 30 rd volume, 3 rd volume, 2018

[3] Tian Ching, Jiaming Yan, Li Hui Bin, Zhi Wei, Ju Ling Jun, Shen Mao quan, Yangxing Yan, Yanlin, von Tiancheng soil sample gamma spectrum analysis self-absorption correction technique study radiation protection No. 1, No. 30, No. 1 of 2010: 54-62

[4] Tiansuning is based on the radioactive body source passive efficiency scale technology of the virtual source principle to study the doctor's paper of Qinghua university in 2016 year 7.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and modifications of the invention can be made, and equivalents may be substituted for elements thereof without departing from the scope of the invention.