A wide-energy gamma-ray standard plane source and a preparation method thereof

Abstract

The application discloses a wide-energy gamma ray standard surface source and a preparation method thereof, and aims at solving the technical problems that the existing radioactive sources cannot meet high-precision measurement due to short service life, uneven distribution of radioactive sources, and self-absorption, etc. The wide-energy gamma ray standard surface source comprises a radioactive source carrier, a sealed shell and a sealed cover. The radioactive source carrier is laid on the bottom of the sealed shell, and radioactive nuclides are attached to the radioactive source carrier. 226 Ra 226 The activity of Ra is not less than 5*10 4 Bq. The sealed cover is tightly pressed on the radioactive source carrier, and the gap between the sealed cover and the sealed shell is sealed by sealing glue, so that the radioactive source carrier is sealed between the sealed shell and the sealed cover.

Description

TECHNICAL FIELD

[0001] The present application relates to a gamma-ray standard plane source, in particular to a wide-energy gamma-ray standard plane source and a preparation method thereof. BACKGROUND

[0002] It is known that the gamma-ray energy involved in nuclear data measurement is as high as 2000-3000 keV, such as 138 the high-energy gamma of Xe is 1768.26 keV, 88 the high-energy gamma of Kr is 2392.11 keV, and therefore the high-energy region of the energy spectrum measurement device must be calibrated for efficiency before accurate data can be obtained in measurement. For a traditional energy spectrum measurement detector in a laboratory, a standard source capable of covering a wide energy range is usually prepared by using 152 Eu, 24 Na and 57 Co and the like to calibrate the energy and efficiency. However, this method has the following two problems: (1) although 152 Eu has a long half-life and can be used for a long time, its gamma-ray energy range is relatively narrow, with the highest energy being only 1408.08 keV; and (2) 24 Na and 57 Co have gammas covering up to 2754 keV, but their half-lives are relatively short, and 24 Na and 57 Co have to be produced and prepared each time calibration is performed, which is cumbersome, inefficient, costly, and particularly passive for users who do not have production facilities. In addition, even 152 Eu has a half-life of 12.7 years, and the service life of the standard source made therefrom is only 10-20 years, which is not conducive to long-term use of the standard source in a laboratory.

[0003] Currently, there are some literature reports on experimental calibration methods for gamma-ray detection efficiency above 1500 keV. The main two methods are: one is a calibration method based on prompt high-energy gamma rays; and the other is a calibration method for calibrating high-energy gamma-ray efficiency based on high-energy gamma rays of daughter nuclides after transient equilibrium of natural radioactive series. In 2005, Li Derong et al. used 66 Ga as a transition to calibrate the detection efficiency of the detector in the energy range of 516 keV-7414 keV by using high-energy prompt gamma in 37 Cl(n,γ) reaction, but the fitting value in the high-energy region deviates from the measured value by generally more than 5%, and this method requires a neutron source to complete the calibration work, which is very costly; and 66The half-life of Ga is only 9.4h, so the above method cannot meet the long-term use of the laboratory. In 2006, researchers selected an analytically pure alumina (Al2O3) as a simulated matrix, and matched the long-lived nuclide 226 Ra to prepare a standard solid source. Because of the addition of 226 Ra is too small to be used as a calibration source for low-energy gamma rays. In 2017, researchers based on 226 Ra and 232 Th in soil, using 226 Ra daughter 214 Bi and 232 Th daughter 208 Tl prepared a standard solid source containing high-energy gamma rays (2448keV and 2614keV), completed the high-energy gamma ray efficiency calibration of the detector, and was used for the monitoring of the primary coolant water of a pressurized water reactor. Both of the above methods use a bulk source mode, which has the problems of mixing inhomogeneity and self-absorption uncertainty caused thereby, and the uncertainty caused by the shape of the standard source itself is large, and is not suitable for high-precision measurement in the laboratory. SUMMARY

[0004] The purpose of the present application is to provide a wide-energy gamma ray standard surface source and a preparation method thereof, so as to solve the technical problems that the existing radioactive sources have a short service life, or cannot meet high-precision measurement due to factors such as uneven distribution of the radioactive source and difficulty in accurately calibrating self-absorption.

[0005] In order to achieve the above purpose, the present application provides a wide-energy gamma ray standard surface source, which is characterized by comprising a radioactive source carrier, a sealed shell and a sealing cover.

[0006] The sealed shell is in the shape of a barrel;

[0007] The radioactive source carrier is laid on the bottom of the sealed shell, and the radioactive nuclide attached thereto is 226 Ra; 226 The activity of the 4 Ra is greater than or equal to 5x10 Bq;

[0008] The sealing cover is covered in the sealed shell, and is pressed on the radioactive source carrier, and the gap between the periphery of the sealing cover and the sealed shell is sealed with sealing glue, so that the radioactive source carrier is sealed between the sealed shell and the sealing cover.

[0009] Further, the radioactive source carrier is made of filter paper, and has a thickness of less than 0.5mm and a diameter of 10-70mm.

[0010] Further, the sealing cover comprises a conical frustum-shaped cover body and a cylindrical cover handle.

[0011] The big end of the cover is in contact with the radioactive source carrier, and the small end is coaxially connected with the cover handle.

[0012] Further, the total thickness of the radioactive source carrier and the bottom of the sealed shell is less than or equal to 2mm.

[0013] Meanwhile, the application also provides a preparation method of the wide-energy gamma ray standard plane source.

[0014] Step 1, preparing a sealed shell in the shape of a barrel and a sealed cover according to the design requirements;

[0015] Step 2, laying the radioactive source carrier on the bottom of the sealed shell;

[0016] Step 3, dropping the solution containing Ra nuclides on the radioactive source carrier according to the predetermined amount; 226

[0017] Step 4, placing the sealed shell in a ventilated place, so that the solution containing Ra nuclides is dried and adheres to the radioactive source carrier; 226

[0018] Step 5, inserting the sealed cover into the sealed shell until the sealed cover is tightly attached to the radioactive source carrier;

[0019] Step 6, coating sealing glue in the gap between the sealed shell and the sealed cover, so as to seal the radioactive source carrier between the sealed shell and the sealed cover, and obtaining the wide-energy gamma ray standard plane source after the sealing glue is solidified, and the preparation is completed.

[0020] Further, step 3 is specifically:

[0021] dividing multiple squares on the radioactive source carrier, and dropping the solution containing Ra nuclides in each square according to the predetermined amount by using a pipette. 226

[0022] Further, the following inspection steps are included:

[0023] Step 7, placing the prepared wide-energy gamma ray standard plane source for a first predetermined time;

[0024] Step 8, placing the wide-energy gamma ray standard plane source on the measurement position of the energy spectrum measurement device to start measurement, setting the duration of each measurement as a second predetermined time, and measuring at least 6 times to obtain measurement data;

[0025] Step 9, comparing the standard deviation of the measurement data with the preset data deviation reference value;

[0026] ​​​If the standard deviation of the measurement data is less than or equal to the preset data deviation reference value, then the wide-energy gamma-ray standard surface source is qualified.

[0027] If the standard deviation of the measurement data is greater than the preset data deviation benchmark value, the wide-energy gamma-ray standard surface source is unqualified, and the process should be repeated in step 1.

[0028] Furthermore, in step 7, the first preset time is at least 30 days;

[0029] In step 8, the second preset time is 1 to 5 days.

[0030] Furthermore, in step 8, the solid angle of the energy spectrum measuring device relative to the wide-energy gamma-ray standard surface source is less than 0.5 sr.

[0031] The beneficial effects of this invention are:

[0032] 1. In this invention, because 226 The half-life of Ra is 1.6 × 10⁻⁶. 3 In [year], this invention adopted 226 The gamma standard surface source prepared by Ra can be prepared once and used for a long time, which significantly improves work efficiency.

[0033] 2. The present invention employs 226 Ra nuclide, 226 After Ra reaches equilibrium with its decay products, it emits gamma rays with a wide energy range, covering 53.23 keV to 2447.7 keV, which significantly improves the energy calibration of high-energy gamma rays and can generally meet the needs of laboratory measurements.

[0034] 3. In this invention, the total thickness of the radioactive source carrier and the bottom of the sealed shell is less than or equal to 2 mm, and 226 The Ra nuclide is uniformly attached to the radioactive source carrier, making the standard surface source very thin, with low absorption of gamma rays and uniform absorption, making it easy to accurately calibrate the absorption coefficient.

[0035] 4. The method for preparing a wide-energy gamma-ray standard surface source provided by this invention can ensure a more uniform distribution of the radioactive source and a smaller uncertainty in the activity determination value, thereby obtaining more accurate measurement data.

[0036] 5. The standard surface source structure provided by this invention is simple and has reliable and safe performance. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of an embodiment of a wide-energy gamma-ray standard surface source according to the present invention.

[0038] Icon labels:

[0039] 1 - radioactive source carrier, 2 - sealed shell, 3 - sealed cover, 31 - cover body, 32 - cover handle, 4 - sealing glue. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0041] The present application provides a wide-energy gamma ray standard plane source, according to the principle of transient equilibrium of parent-daughter decay of radium 226 Ra, the gamma rays emitted by multiple decay daughters of radium 226 Ra covering a wide energy range (53.23keV-2447.7keV energy region) are ingeniously utilized. Because 226 The half-life of radium 3 Ra is 1.6×10 226 years, the emission rate of each gamma ray in the standard plane source prepared thereby will not change significantly in a short period of time, and the standard plane source can be used for a long time. The present application also utilizes this principle to propose a testing method for testing whether the standard plane source is qualified.

[0042] The specific scheme is as follows:

[0043] As shown in Figure 1 , the wide-energy gamma ray standard plane source comprises a radioactive source carrier 1, a sealed shell 2, a sealed cover 3, and sealing glue 4. The sealed cover 3 comprises a conical frustum-shaped cover body 31 and a cylindrical cover handle 32. The large end of the cover body 31 is in contact with the radioactive source carrier 1, and the small end is coaxially connected with the cover handle 32. The radioactive source carrier 1 is laid on the bottom surface of the sealed shell 2, the cover body 31 is located above the radioactive source carrier 1 and inside the sealed shell 2, and the sealing glue 4 is filled in the gap between the sealed cover 3 and the sealed shell 2.

[0044] The radioactive source carrier 1 is filter paper with a thickness of less than 0.5mm. Radioactive nuclide 226 Ra, 226 Ra with an activity of not less than 5×10 4 Bq is attached to the radioactive source carrier 1. The filter paper of the radioactive source carrier 1 is divided into squares, and radioactive nuclide 226 Ra is uniformly attached in each square to ensure the uniformity of the wide-energy gamma ray source.

[0045] The thickness of the radioactive source carrier 1 is less than 0.5 mm, and the wide-energy gamma ray standard source provided by the present application is not a volume source but a surface source. The external diameter of the wide-energy gamma ray standard source is 25-76 mm, and the thickness of the bottom of the wide-energy gamma ray standard source is not greater than 2 mm (the total thickness of the radioactive source carrier 1 and the sealing shell 2), and the absorption effect on gamma rays is small.

[0046] The sealing shell 2 and the sealing cover 3 are made of organic glass, which has a small mass absorption coefficient and the advantages of simple structure, safety and reliability; the sealing shell 2 and the sealing cover 3 are not connected by threads, avoiding the storage of gaseous decay sub-nuclei in the gap between the threads 226 Gaseous decay sub-nuclei of Ra 222 Rn, a volume source, but the cover 31 is provided in a conical frustum structure, and the gap between the cover 31 and the inner wall of the sealing shell 2 is sealed by the sealing glue 4, so that the gaseous decay sub-nuclei of Ra 222 Rn are blocked within the range of the radioactive source carrier 1, ensuring the surface source structure.

[0047] The specific preparation steps are as follows:

[0048] Prepare 0.1 mm thick filter paper as the radioactive source carrier 1, prepare a circular sealing shell 2 and a circular sealing cover 3 made of organic glass, the outer diameter of the latter matches the inner diameter of the former, the inner diameter of the sealing shell 2 is 25 mm; prepare 704 silicone as the sealing glue 4, and prepare a coaxial high-purity germanium detector with a relative efficiency of 40%. 5 Bq 226 Prepare 0.5 mL of a solution of Ra nuclides and a pipette, and prepare a coaxial high-purity germanium detector with a relative efficiency of 40%.

[0049] The preparation steps of the wide-energy gamma ray standard surface source are as follows:

[0050] (1) Cut the radioactive source carrier 1 filter paper into a circle with a diameter matching the inner diameter of the circular sealing shell 2, and then lay it flat on the inner bottom surface of the sealing shell 2;

[0051] (2) Use a pipette to drop 8×10 4 Bq of a solution containing 226 Ra nuclides (hereinafter referred to as 226 Ra solution) onto the radioactive source carrier filter paper;

[0052] (3) Place the sealing shell 2 containing the 226 Ra solution in a ventilated place and dry it;

[0053] (4) Insert the sealing cover 3 from the upper part of the sealing shell 2 until it is close to the radioactive source carrier filter paper;

[0054] (5) Apply 704 silicone to the gap between the sealing cover 3 and the sealing shell 2 until it is cured.

[0055] After the standard surface source is prepared, its effectiveness needs to be verified, and the verification steps are as follows:

[0056] (1) The prepared wide-energy gamma ray standard surface source is left for 30 days;

[0057] (2) Then the standard surface source is placed 25 cm above a coaxial high-purity germanium detector with a relative efficiency of 40%, a measurement time of 1 day is set, and 20 sets of measurement data are obtained by continuous measurement for 20 days;

[0058] (3) The data deviation reference value is set to 1%;

[0059] (4) The obtained 20 sets of measurement data are processed, if the count rate standard deviation of main gamma rays such as 609 keV, 352 keV, 1120 keV and 1724 keV is less than or equal to the preset reference value 1%, the prepared wide-energy gamma ray standard surface source is considered to be qualified, otherwise it is unqualified and needs to be prepared again.

[0060] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this, any change or replacement within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A wide-energy gamma-ray standard surface source, characterized in that: It includes a radioactive source carrier (1), a sealed housing (2), and a sealed cover (3); The sealing housing (2) is cylindrical; The radioactive source carrier (1) is laid flat at the bottom of the sealed shell (2), and a radioactive nuclide is attached to it. 226 Ra; the 226 Ra activity greater than or equal to 5 × 10 4 Bq; The sealing cap (3) is installed inside the sealing housing (2) and presses on the radioactive source carrier (1). The gap between the periphery of the sealing cap (3) and the sealing housing (2) is sealed with sealant (4), so that the radioactive source carrier (1) is sealed between the sealing housing (2) and the sealing cap (3).

2. The wide-energy gamma-ray standard surface source according to claim 1, characterized in that: The radioactive source carrier (1) is made of filter paper with a thickness of less than 0.5 mm and a diameter of 10-70 mm.

3. The wide-energy gamma-ray standard surface source according to claim 1 or 2, characterized in that: The sealing cap (3) includes a frustum-shaped cap body (31) and a cylindrical cap handle (32); The large end of the cover (31) is in contact with the radioactive source carrier (1), and the small end is coaxially connected to the cover handle (32).

4. The wide-energy gamma-ray standard surface source according to claim 3, characterized in that: The total thickness of the bottom of the radioactive source carrier (1) and the sealed housing (2) is less than or equal to 2 mm.

5. A method for preparing a wide-energy gamma-ray standard surface source, used to prepare the wide-energy gamma-ray standard surface source according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Prepare a cylindrical sealed shell (2) and a sealing cap (3) according to the design requirements; Step 2: Lay the radioactive source carrier (1) flat at the bottom of the sealed shell (2); Step 3: Add the predetermined amount of [a substance] to the radioactive source carrier (1). 226 Solution of Ra nuclide; Step 4: Place the sealed housing (2) in a ventilated area so that the contents... 226 The Ra nuclide solution was air-dried and attached to the radioactive source carrier (1); Step 5: Insert the sealing cap (3) into the sealing housing (2) until the sealing cap (3) is tightly attached to the radioactive source carrier (1); Step 6: Apply sealant (4) to the gap between the sealed shell (2) and the sealed cover (3) to seal the radioactive source carrier (1) between the sealed shell (2) and the sealed cover (3). After the sealant (4) is cured, a wide-energy gamma-ray standard surface source is obtained, and the preparation is completed.

6. The method for preparing a wide-energy gamma-ray standard surface source according to claim 5, characterized in that, Step 3 specifically involves: Divide the radioactive source carrier (1) into several squares on an even scale, and use a pipette to drop a predetermined amount of [a substance] into each square. 226 Solution of Ra nuclide.

7. The method for preparing a wide-energy gamma-ray standard surface source according to claim 6, characterized in that, It also includes the following inspection steps: Step 7: Let the prepared wide-energy gamma-ray standard surface source stand for the first preset time; Step 8: Place the wide-energy gamma-ray standard surface source on the measurement position of the energy spectrum measurement device to start the measurement. Set the duration of each measurement to the second preset time, and perform at least 6 measurements to obtain measurement data. Step 9: Compare the standard deviation of the measurement data with the preset data deviation benchmark value; If the standard deviation of the measurement data is less than or equal to the preset data deviation reference value, then the wide-energy gamma-ray standard surface source is qualified. If the standard deviation of the measurement data is greater than the preset data deviation benchmark value, the wide-energy gamma-ray standard surface source is unqualified, and the process should be repeated in step 1.

8. The method for preparing a wide-energy gamma-ray standard surface source according to claim 7, characterized in that: In step 7, the first preset time is at least 30 days; In step 8, the second preset time is 1 to 5 days.

9. The method for preparing a wide-energy gamma-ray standard surface source according to claim 7 or 8, characterized in that: In step 8, the solid angle of the energy spectrum measuring device relative to the wide-energy gamma-ray standard surface source is less than 0.5 sr.

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