A radioactive source activity measurement device and method

Abstract

The application discloses a radioactive source activity measuring device and method, and aims at solving the technical problem of poor measuring result precision and high uncertainty of the existing radioactive source activity measurement. Specifically, the device comprises six detectors and a positive cubic container, and the positive cubic container is used for containing the radioactive source to be measured. The internal cavity of the positive cubic container is also in a positive cubic shape, and the side length of the positive cubic internal cavity is d. The center line through the midpoint of the front and back faces of the positive cubic container is defined as the X axis, the center line through the midpoint of the left and right faces is defined as the Y axis, and the center line through the midpoint of the upper and lower faces is defined as the Z axis. The detection surfaces of the six detectors are respectively opposite to and parallel to the six faces of the positive cubic container. The six detectors are respectively the first detector and the second detector with the central axis along the X axis, the third detector and the fourth detector with the central axis along the Y axis, and the fifth detector and the sixth detector with the central axis along the Z axis.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of body source radioactive measurement device, specifically, a kind of radioactive body source activity measurement device and method. BACKGROUND

[0002] Radioactivity activity is one of the key physical quantities of radioactivity measurement.The measured object in many scenarios is a body source with a certain thickness, such as filter sample, soil and rock sample, etc.In measurement, these body sources themselves will form absorption to the gamma rays emitted by the radioactive source contained therein, and the absorption proportion of different medium thickness is different.In addition, whether the radioactive material distribution inside the body source is uniform is also a key factor affecting the accuracy of measurement.In the existing literature, the radioactive body source measurement technology mainly focuses on the key technology research of "how to accurately calibrate efficiency" and "how to prepare uniform body source sample".The patent literature with the name "Method and device for simulating the detection efficiency of a detector by using a virtual source", application number 201410264382.9 discloses a technical solution based on virtual source equivalent technology to equivalent the efficiency of the body source to a point source or a surface source.This technical means of replacing measured efficiency with simulated efficiency is often used in application scenarios with low accuracy requirements;but for high-precision measurement, it is necessary to reduce the uncertainty of measurement results as much as possible, which is the goal that must be adhered to in measurement technology. SUMMARY

[0003] The purpose of the present application is to provide a radioactive body source activity measurement device and method to solve the technical problems of poor accuracy and high uncertainty of existing radioactive body source activity measurement results.

[0004] In order to achieve the above purpose, the present application provides a radioactive body source activity measurement device, which is characterized by comprising six detectors and a right cubic container, the right cubic container is used for containing the radioactive body source to be measured; the internal cavity of the right cubic container is also right cubic, and the edge length of the right cubic internal cavity is d.

[0005] The center line passing through the midpoint of the front and back faces of the right cubic container is defined as the X axis, the center line passing through the midpoint of the left and right faces is defined as the Y axis, and the center line passing through the midpoint of the upper and lower faces is defined as the Z axis.

[0006] The detection surfaces of the six detectors are respectively opposite and parallel to the six faces of the right cubic container; the six detectors are respectively a first detector and a second detector with the center axis along the X axis, a third detector and a fourth detector with the center axis along the Y axis, and a fifth detector and a sixth detector with the center axis along the Z axis.

[0007] Furthermore, the minimum distances between the detection surfaces of the six detectors and the outer surface of the radioactive source to be detected or the inner surface of the regular cube container are all greater than 4.5d.

[0008] Furthermore, the radioactive source to be detected is in a cube shape, and its size is adapted to the inner cavity of the cube container.

[0009] Furthermore, the six detectors are all coaxial radioactive detectors, and the diameter of their detection surface is greater than the side length d of the regular cube-shaped internal cavity.

[0010] Furthermore, the side length d of the regular cube-shaped internal cavity is 1 cm.

[0011] The present invention also provides a method for measuring the activity of a radioactive body source, based on the above-mentioned radioactive body source activity measuring device, characterized in that it includes the following steps:

[0012] Step 1: Place the radioactive source to be tested in the inner cavity of a cube container;

[0013] Step 2: At time t, use the six detectors to measure simultaneously to obtain 6 count rates at time t;

[0014] Step 3: Define the two detectors located on the same axis as the i-th detector and the j-th detector, and define the counting rates of the i-th detector and the j-th detector at time t as n t-i and n t-j , use formula (1) to calculate the activity A of the radioactive source N , a total of three A N Activity measurements, respectively A N1 、A N2 and A N3 :

[0015]

[0016] Among them, P γ is the characteristic γ emission probability, ε i is the detection efficiency of the i-th detector, ε j is the detection efficiency of the jth detector, μ is the dielectric absorption coefficient of the radioactive body source to the characteristic γ-ray;

[0017] Step 4: Put three A N The activity measurement value is calculated according to formula (2) to obtain the average activity value A of the radioactive source. NM :

[0018]

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention is based on the basic principle of calculating radioactive activity by multiplying peak count rates measured by multiple detectors. A cubic container is designed to contain a radioactive body source as the measurement target. The self-absorption path of the rays is standardized. Six detectors simultaneously obtain three sets of measurement data, which are finally averaged to obtain an accurate evaluation value of the body source. This method can significantly reduce measurement uncertainty and improve the measurement accuracy of radioactive body source activity.

[0021] 2. The six detectors in the present invention can obtain data within the same measurement time, saving measurement time and providing a quick way to accurately measure shorter-lived radioactive nuclides. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of a cube container in an embodiment of a radioactive source activity measurement device of the present invention.

[0023] Figure 2 It is a structural schematic diagram of an embodiment of a radioactive body source activity measurement device of the present invention.

[0024] Figure Number:

[0025] 1-first detector, 2-second detector, 3-third detector, 4-fourth detector, 5-fifth detector, 6-sixth detector, 7-cube container. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] An embodiment of the present invention provides a device for measuring the activity of a radioactive body source, Figure 1 and Figure 2 As shown, it includes a cube container 7 and six detectors whose detection surfaces are respectively opposite to and parallel to the six surfaces of the cube container 7.

[0028] The cube container 7 has a side length of 1 cm and is used to hold the radioactive source, so that the entire container forms a regular cube shape. In addition, glue can be used to shape the radioactive source 7 into a regular cube shape. If a cube container 7 is selected, the inner cavity of the cube container 7 is also a regular cube shape, and the side length of the inner cavity is d. The volume of the inner cavity is adapted to the volume of the radioactive source to be contained, so that the radioactive source can fill the cube container 7.

[0029] All six detectors are coaxial radioactive detectors, with a detection surface diameter greater than or equal to 1 cm. The six detectors are arranged coaxially in pairs, forming three detector pairs, with their three central axes perpendicular to each other. If the centerline running through the midpoints of the front and back surfaces of the cube container 7 is defined as the X-axis, the centerline running through the midpoints of the left and right surfaces of the cube container 7 is defined as the Y-axis, and the centerline running through the midpoints of the top and bottom surfaces of the cube container 7 is defined as the Z-axis, then the six detectors are respectively the first detector 1 and the second detector 2, with their central axes arranged along the X-axis; the third detector 3 and the fourth detector 4, with their central axes arranged along the Y-axis; and the fifth detector 5 and the sixth detector 6, with their central axes arranged along the Z-axis. This ensures that the geometric center of the radioactive source coincides with the geometric center of the six detectors, and their three central axes coincide with the central axes of the three detector pairs. The distance between the cylindrical top end face of each detector and the facing surface of the radioactive source is controlled to be greater than 4.5 cm.

[0030] The measurement steps are as follows:

[0031] Step 1: Place the radioactive source to be tested in the inner cavity of the cube container 7.

[0032] Step 2: Define the two detectors located on the same axis as the i-th detector and the j-th detector. At time t, the six detectors measure simultaneously and obtain the counting rates of the six detectors at time t as n. t-1 , n t-2 , n t-i …n t-6 ; The formula is:

[0033]

[0034] Among them, A N is the activity of the radioactive source at time t, P γ is the characteristic γ emission probability, ε i is the detection efficiency of the i-th detector, μ is the dielectric absorption coefficient of the radioactive body source to the characteristic γ-ray, d i is the distance between the radioactive nuclide in the radioactive body source and the surface of the body source in the direction of the i-th detector, and e is a constant.

[0035] Step 3: Take the counting rate n of the two detectors located opposite to each other on the same axis. t-i and n t-j , then the two relative detector count rates are multiplied to obtain:

[0036]

[0037] The activity A of the radioactive source can be obtained by transforming the above formula N for:

[0038]

[0039] This way you can get three A's in total. N Measurement value.

[0040] Step 4: For the three A's obtained in step 3 N The average activity value of the radioactive source is obtained by taking the average value A NM , that is, the evaluation value of the activity of the radioactive body source:

[0041]

[0042] Based on the basic principle of calculating radioactive activity by multiplying the peak count rates measured by multiple detectors, a cube container 7 is designed to contain a radioactive body source as the measurement target. Six detectors simultaneously obtain three sets of measurement data, and finally the average is taken to obtain an accurate evaluation value of the body source. This method can significantly reduce measurement uncertainty and improve the measurement accuracy of radioactive body source activity.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention shall be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for measuring the activity of a radioactive body source, based on a radioactive body source activity measuring device, characterized in that: The radioactive body source activity measuring device comprises six detectors and a cube container (7), wherein the cube container (7) is used to hold the radioactive body source to be measured; the inner cavity of the cube container (7) is also in the shape of a cube, and the side length of the inner cavity of the cube is d; Define the center line passing through the midpoints of the front and back faces of the cube container (7) as the X axis, the center line passing through the midpoints of the left and right faces as the Y axis, and the center line passing through the midpoints of the top and bottom faces as the Z axis; The detection surfaces of the six detectors are respectively opposite to and parallel to the six faces of the regular cube container (7); the six detectors are respectively a first detector (1) and a second detector (2) whose central axes are arranged along the X axis, a third detector (3) and a fourth detector (4) whose central axes are arranged along the Y axis, and a fifth detector (5) and a sixth detector (6) whose central axes are arranged along the Z axis; The minimum distance between the detection surfaces of the six detectors and the outer surface of the radioactive source to be detected or the inner surface of the cube container (7) is greater than 4.5d; The method for measuring the activity of a radioactive body source comprises the following steps: Step 1: Place the radioactive source to be tested in the inner cavity of the cube container (7); Step 2: At time t, use the six detectors to measure simultaneously to obtain 6 count rates at time t; Step 3: Define the two detectors located on the same axis as the i-th detector and the j-th detector, and define the counting rates of the i-th detector and the j-th detector at time t as n t-i and n t-j , use formula (1) to calculate the activity A of the radioactive source N , a total of three A N Activity measurements, respectively, A N1 、A N2 and A N3 : Among them, P γ is the characteristic γ emission probability, ε i is the detection efficiency of the i-th detector, ε j is the detection efficiency of the jth detector, μ is the dielectric absorption coefficient of the radioactive body source to the characteristic γ-ray; Step 4: Put three A N The activity measurement value is calculated according to formula (2) to obtain the average activity value A of the radioactive source. NM :

2. The method for measuring radioactive body source activity according to claim 1, wherein: The radioactive source to be tested is in the shape of a cube, and its size is adapted to the cube-shaped internal cavity of the cube container (7).

3. The method for measuring activity of a radioactive body source according to claim 2, wherein: The six detectors are all coaxial radioactive detectors, and the diameter of their detection surface is greater than the side length d of the inner cavity of the regular cube.

4. The method for measuring activity of a radioactive body source according to claim 3, wherein: The side length d of the regular cube-shaped internal cavity is 1 cm.

Images