Radioactive source and preparation method and application thereof

Abstract

The invention relates to the technical field of radioactive source preparation, and particularly discloses a radioactive source and a preparation method and application thereof. The method for preparing the radioactive source comprises the following steps: (1) preparing a raw material solution of an organic film; the raw material solution is prepared from Ba14CO3, acetone, ethylene glycol isooctyl ether and oily polyurethane; the mass volume ratio of Ba14CO3 to acetone is 1: (7-13) g / mL; the volume ratio of the acetone to the oily polyurethane is (0.8-1.2): 1; the mass ratio of the Ba14CO3 to the ethylene glycol isooctyl ether is 1: (0.4-0.6); (2) spin-coating the raw material liquid in an emission window of a radioactive source shell, and curing to form an organic film; and (3) covering the organic film with an aluminum laminated film, and fixing the aluminum laminated film in the radioactive source shell. The radioactive source is simple and convenient to prepare, high in emissivity and good in uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive source preparation, and in particular to a radioactive source and a preparation method and application thereof. Background Art

[0002] Air quality issues are receiving more and more attention. The number of haze days is gradually increasing, affecting people's health. In particular, the inhalation of PM2.5 particles is very harmful to human health. It has been listed as one of the must-measure items for ambient air quality. The β-ray automatic monitoring instrument is a commonly used PM2.5 monitoring equipment, which can accurately measure the concentration of PM2.5 in the air. The half-life of C-14 is 5730 years, and C-14 can emit pure β rays with a maximum energy of 156.5keV. The maximum range of β rays emitted by C-14 in the air is 22cm. Since C-14 is a low-toxic nuclide and will not cause harm to humans, C-14 has been widely used in PM2.5 monitoring.

[0003] The principle of the β-ray automatic monitoring instrument to monitor PM2.5 concentration is to use a C-14 β-radiation source to emit β-rays through the filter membrane that collects PM2.5 particles, and analyze the PM2.5 particle concentration through the attenuation of the β-rays after passing through the filter membrane. Among them, the emissivity of the C-14 β-radiation source is an important factor affecting the accuracy of PM2.5 monitoring results.

[0004] The conventional preparation method of C-14 β standard source is to first prepare C-14 methacrylic acid monomer, then polymerize it into methyl methacrylate, and then coat the methyl methacrylate on an aluminum plate to make an organic thin film radioactive source. The conventional method faces the following problems: (1) The process of preparing C-14 methacrylic acid monomer is complicated, the yield is low, and the risk of radioactive contamination during the preparation process is high; (2) The reaction activity of methacrylic acid monomer to methyl methacrylate is low, and it is necessary to increase the temperature and add a catalyst, which is easy to produce radioactive aerosols; (3) Methyl methacrylate will solidify quickly when coated on aluminum sheet, and the coating thickness is not easy to control, resulting in poor uniformity of the radioactive source, which cannot meet the use requirements of β-ray automatic detection instruments; (4) Since the specific activity of C-14 methacrylic acid monomer is relatively low, the thickness of the organic film will result in a large blocking of β particles, which is suitable for making some low-emissivity standard sources, but cannot meet the high-emissivity requirements of β-ray automatic monitoring instruments. Therefore, it is necessary to further study the preparation of radioactive sources. Summary of the invention

[0005] One of the objects of the present invention is to provide a new and convenient method for preparing a C-14 β radiation source with high emissivity and high uniformity.

[0006] The present invention provides a method for preparing a radioactive source, comprising: (1) A raw material solution for preparing an organic membrane; the raw material solution includes Ba 14 CO3, acetone, ethylene glycol isooctyl ether and oily polyurethane; Ba 14 The mass volume ratio of CO3 to acetone is 1: (7-13) g / mL; the volume ratio of acetone to oily polyurethane is (0.8-1.2): 1; Ba 14 The mass ratio of CO3 to ethylene glycol isooctyl ether is 1:(0.4-0.6); (2) spin coating the raw material liquid in the emission window of the radiation source housing and curing to form an organic film; (3) Covering the organic film with an aluminum-plated film, and fixing the aluminum-plated film in the radiation source housing.

[0007] The present invention has found that it is difficult to obtain a uniform coating (organic film) when radioactive organic materials are compounded in the radiation source shell, thus affecting the detection effect. To this end, the present invention has been exploring and finally found that when a specific surfactant and oily polyurethane are combined with acetone to carry out Ba 14 When CO3 is dispersed, Ba 14 CO3 is evenly dispersed, and a highly uniform coating is obtained during spin coating. Furthermore, when the raw material solution of the present invention is used for spin coating, uniformity can be maintained even when the coating is very thin, thereby reducing the obstruction to β-particle emission by reducing the thickness of the organic film itself.

[0008] In the present invention, the chemical formula of the oily polyurethane is (C 10 H8N2O2·C6H 14 O3) n , the range of n is 500~20000.

[0009] In the method of the present invention, the spin coating is carried out under vacuum, first at 1000-1500 rpm for 10-15s, then at 4000-5000 rpm for 60-70s, preferably, first at 1000 rpm for 10s, then at 4000 rpm for 60s.

[0010] The spin coating method of the present invention is advantageous for obtaining a uniform organic film.

[0011] In the method of the present invention, the thickness of the cured organic film is 300-600 μm; the thickness of the aluminum-plated film is 10-30 μm.

[0012] In the method of the present invention, the method for preparing the raw material liquid of the organic membrane comprises: firstly 14 CO3, ethylene glycol isooctyl ether, and acetone twice the formula amount are mixed and stirred in the presence of grinding media, and then mixed and stirred with oily polyurethane.

[0013] The mixing method of the present invention is conducive to uniform mixing of the components. Acetone is easy to volatilize at room temperature, so the present invention preferably adds acetone twice the amount of the formula to avoid the volatilization of acetone during mixing and stirring, which makes the acetone content in the final raw material liquid insufficient and affects the effect of subsequent spin coating.

[0014] In the method of the present invention, the stirring time for each time is 28-32 minutes; the grinding medium is zirconia ceramic balls of various particle sizes; preferably, the particle sizes of the zirconia ceramic balls include 1 mm, 3 mm and 5 mm; more preferably, each 20 mL of acetone includes 10 zirconia ceramic balls with a diameter of 1 mm, 5 zirconia ceramic balls with a diameter of 3 mm, and 5 zirconia ceramic balls with a diameter of 5 mm.

[0015] In the method of the present invention, the radiation source housing includes a pressure ring and a radiation source loading platform, a first groove is provided on the radiation source loading platform, a second groove is provided at the bottom of the first groove, the second groove is connected to the first groove, and the inner diameter of the second groove is smaller than the inner diameter of the first groove; the first groove is used to load the aluminum-plated film, and the second groove is used to load the organic film; the pressure ring can be nested and fixed in the first groove, and is used to fix the aluminum-plated film in the first groove; after the pressure ring is nested and fixed in the first groove, the inner wall surface of the pressure ring is flush with the inner wall surface of the second groove, exposing the organic film loaded in the second groove.

[0016] In the method of the present invention, the first groove is cylindrical, with a depth of 1-1.5 mm and a diameter of 5-30 mm; the second groove is cylindrical, with a depth of 0.5-0.8 mm and a diameter of 3-28 mm; the pressure ring is a ring tube structure, with a height of 1-1.5 mm, an inner diameter of 3-28 mm and an outer diameter of 5-30 mm; And / or, the radiation source loading platform is cylindrical as a whole, with a height of 10-30mm (preferably 8-20mm) and an outer diameter of 15-50mm, and the outer wall of the radiation source loading platform has a thread; a mounting hole is provided on both sides of the first groove of the radiation source loading platform, which is circular, with a depth of 1-1.5mm and a diameter of 1-2mm, for fixing the radiation source on the instrument; preferably, the cross-sections of the first groove and the second groove are concentric circles; the first groove is located at the center of the radiation source loading platform.

[0017] The radiation source shell of the present invention has a simple structure and is easy to assemble. The aluminized film can be fixed by placing the aluminized film above the first groove of the radiation source loading platform, pressing the aluminized film from above with a pressure ring, and then cutting off the excess aluminized film exposed at the edge of the pressure ring.

[0018] The present invention also provides a radiation source, which is prepared by the above method.

[0019] The present invention also provides an organic film as described above.

[0020] The organic film of the invention can emit beta particles and can be used in various detection fields.

[0021] The present invention also provides application of the above-mentioned radioactive source or organic film in detecting PM 2.5 particles.

[0022] The beneficial effects of the present invention are at least: The method of the present invention is simple in process, and the prepared β plane source has small β particle loss, and the β particle surface emission rate can reach 10 6 s -1 The organic film has good firmness, high utilization rate of radioactive nuclides, high uniformity (the deviation of each part is less than 3%), safety and reliability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the C-14 β radiation source of the present invention.

[0024] Figure 2 This is a real picture of the source shell of the C-14 β radiation source of the present invention.

[0025] Figure 3 This is a physical picture of the C-14 β radiation source after preparation of the present invention. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0027] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources or prepared according to conventional methods in the art. Oily polyurethane was purchased from Shenzhen Yoshida Chemical Co., Ltd., product number E1401. The main equipment and reagents involved in the present invention are shown in Tables 1 and 2.

[0028] Table 1

[0029] Table 2

[0030] Example 1

[0031] This embodiment provides a method for preparing a radioactive source, which is as follows: (1) 1g of Ba 14 The CO3 raw material was placed in a concave bottom glass bottle, and 20 mL of acetone and 0.5 g of ethylene glycol isooctyl ether were added. Then, two magnets with a diameter of 10 mm and 10 zirconia ceramic balls with a diameter of 1 mm, 5 with a diameter of 3 mm, and 5 with a diameter of 5 mm were added. The zirconia ceramic balls were used as grinding media. The mixture was stirred with a magnetic stirrer for 30 minutes to obtain a uniformly distributed carbonate powder suspension. Then, 10 mL of oily polyurethane was added and magnetic stirring was continued for 30 minutes to finally obtain a raw material solution (subsequently used for the preparation of organic membranes, containing 10 mL of acetone).

[0032] (2) Take 10 μL of the raw material liquid and use a liquid scintillation spectrometer to measure the activity value A0. According to the activity value A1 of the radioactive source, calculate the usage amount V1 of the raw material liquid, V1=A1 / A0×10 μL / B; wherein B is the barrier coefficient of the organic film and the aluminum-plated film. In this embodiment, A1 is 100 μCi, A0 is 0.8 μCi, and B is 0.37.

[0033] (3) A radiation source shell is used for the preparation of a radiation source. The radiation source shell includes a pressure ring and a radiation source loading platform. A first groove is provided at the center of the radiation source loading platform. The first groove is cylindrical, has a depth of 1 mm, and has a diameter of 8 mm. A second groove is provided at the bottom of the first groove. The second groove is connected to the first groove. The second groove is cylindrical, has a depth of 0.5 mm, and has a diameter of 6 mm. The inner diameter of the second groove is smaller than the inner diameter of the first groove. The first groove and the second groove are combined to form a stepped structure. The cross-sections of the first groove and the second groove are concentric circles. The first groove is used to load the aluminum-plated film, and the second groove is used to load the organic film.

[0034] The radiation source loading platform is cylindrical in shape, with a height of 8 mm and an outer diameter of 20 mm. There are threads on the outer wall of the cylinder for assembly with other components that need to be installed with radiation sources. A mounting hole is provided on both sides of the first groove of the radiation source loading platform, which is circular, 1 mm in depth and 1.5 mm in diameter, for mounting the radiation source on the instrument.

[0035] The pressure ring is a ring tube structure with a height of 1 mm, an inner diameter of 6 mm, and an outer diameter of 8 mm. The pressure ring can be tightly matched with the first groove and nested and fixed in the first groove to fix the aluminum-plated film in the first groove. After the pressure ring is nested and fixed in the first groove, the inner wall surface of the pressure ring is flush with the inner wall surface of the second groove, exposing the organic film loaded on the bottom of the second groove.

[0036] The raw material liquid of V1 prepared according to the method of step (1) was added to the second groove (emission window) of the radiation source loading platform. The bottom of the radiation source loading platform after the raw material was glued with double-sided tape and fixed on the turntable of the thin film spin coater. Then, vacuum was evacuated. The low-speed coating time was set to 10 s and the rotation speed was 1000 rpm. The high-speed coating time was set to 60 s and the rotation speed was 4000 rpm. After the spin coating was completed, the source shell was placed under an infrared lamp for 10 minutes for curing to obtain an organic film with a thickness of 300 μm.

[0037] (4) Use a cutter to cut a 10 μm thick aluminum film on the anti-cutting board, place the aluminum film on the first groove of the radiation source loading platform, use a pressure ring to press down from the top of the aluminum film, and then cut off the excess aluminum film exposed at the edge of the pressure ring. The pressure ring carrying the aluminum film is nested and fixed in the first groove, the inner side wall and bottom end face of the first groove are covered with the aluminum film, and the organic film in the second groove is sealed under the aluminum film.

[0038] (5) Gently wipe the radioactive source with alcohol cotton to remove contaminants. After drying, place the radioactive source in the measurement tray of the α or β rapid measuring instrument for activity measurement. The activity value must be within the range of 0.85~1.15A1 to be qualified.

[0039] (6) Surface contamination and leakage inspection shall be carried out afterwards. The measured value of surface contamination shall be lower than the required value of 200Bq as stipulated by the national standard.

[0040] (7) Finally, conduct an appearance inspection to ensure that the surface is smooth, flat and free of damage.

[0041] The schematic diagram of the radiation source is shown in Figure 1 . See the actual picture of the radiation source shell Figure 2 The actual picture of the radioactive source after preparation is shown in Figure 3 .

[0042] Experimental Example 2

[0043] This experimental example tests the radioactive source prepared by spin coating in Example 1, as follows: 1. Experiment on the blocking law of self-absorption and aluminum coating

[0044] According to the liquid scintillation spectrometer measurement results, the emissivity of 50 μL of raw material solution is 561500 s -1, the theoretical value measured by the α, β activity rapid measurement instrument should be 28075cps. The α, β activity rapid measurement instrument was used for measurement at 3 cm, and the detection efficiency of the instrument was about 5%. The results are shown in Table 3. The actual measured value of the organic film prepared by the spin coating method of Example 1 of the present invention is 20.21% less than the theoretical value, mainly because the organic film blocks the emission of a part of the β particles after curing. The blocking rate of 10μm thick aluminum film for β particles is about 17%. The measured value of the instrument after the aluminum film is sealed is 17706cps, and the actual emissivity is 3.54×10 5 s -1 The aluminum coating ensures safety performance without excessively blocking beta particles.

[0045] Table 3 Experimental results of self-absorption of organic films and barrier law of aluminum films

[0046] 2. Parallel experiment

[0047] Ten radioactive sources were prepared by the spin coating method of Example 1, and the activity was measured using an α and β activity rapid measuring instrument. The results are shown in Table 4. The deviation range was calculated to be -4.61% to +5.11%, all within the expected index range of -15% to +15%.

[0048] Table 4 Parallel experiment of radioactive sources prepared by spin coating

[0049] 3. Surface contamination and leakage inspection

[0050] According to the method of Example 1 of the present invention, 10 radioactive sources were prepared and tested. The results are shown in Table 5. It can be seen that the maximum value of the surface contamination and leakage test is 16 Bq, which is far lower than the national standard of 200 Bq. Therefore, it can be proved that the C-14 β radioactive source prepared by the spin coating method of Example 1 has good sealing performance.

[0051] Table 5 Surface contamination and leakage test results

[0052] Experimental Example 2

[0053] This experimental example uses an α and β activity rapid measurement instrument to measure at 3 cm (the detection efficiency of the instrument is about 5%), and compares the experimental data of the radioactive source prepared by the spin coating method of Example 1 of the present invention with the traditional method (see Chapter 9 Application of Radioactive Standard Sources Section 3 Preparation Method of Carbon-14 and Hydrogen-3 Standard Sources in Sun Shuzheng's "Preparation and Application of Radioactive Sources"), as follows: 1. Comparison of the barrier efficiency of organic films prepared by traditional method and spin coating method

[0054] The blocking rate results of the organic film are shown in Table 6. The actual measured value of the emissivity of the organic film prepared by the conventional method is 57.11% less than the theoretical value, mainly because the conventional method uses C-14 methacrylic acid monomer, the specific activity range of this isotope raw material is 10~15mCi / g, and the low specific activity will lead to the thickness of the organic film. In addition, the thickness of the organic film prepared by the conventional method is not uniform, and the thick part of the organic film blocks more β particles. The actual measured value of the emissivity of the organic film prepared by the spin coating method in Example 1 of the present invention is 20.21% less than the theoretical value, and the organic film blocks the emission of a part of the β particles after curing.

[0055] Table 6 Comparison of the barrier efficiency of organic films prepared by traditional method and spin coating method

[0056] 2. Comparison of experimental data on the parallelism of radioactive sources prepared by traditional method and spin coating method

[0057] Ten radioactive sources were prepared by the conventional method and the spin coating method, and the activity was measured by using an α and β activity rapid measuring instrument. The statistical results are shown in Table 7. The deviation range of the activity of the radioactive sources prepared by the conventional method is -18.33% to +20.42%, and the activity of four radioactive sources is not within the expected index range of -15% to +15%. The deviation range of the activity of the radioactive sources prepared by the spin coating method in Example 1 of the present invention is -4.61% to +5.11%, all of which are within the expected index range of -15% to +15%.

[0058] Table 7 Comparison of experimental data of parallelism of radioactive sources prepared by traditional method and spin coating method

[0059] 3. Comparison of the highest emissivity of radioactive sources prepared by traditional method and spin coating method (directly measured using α and β activity rapid measuring instrument)

[0060] The highest emissivity of the radioactive source prepared by traditional methods is 3.33×10 5 s -1 , which cannot meet the highest use requirements of the β-ray automatic monitoring instrument. The maximum emissivity of the radiation source prepared by the spin coating method in Example 1 of the present invention is 1.57×10 6 s -1 , which fully meets the highest use requirements of β-ray automatic monitoring instruments. The comparison results are shown in Table 8.

[0061] Table 8 Comparison of the maximum emissivity of the radioactive source prepared by the traditional method and the spin coating method

[0062] 4. Test results of uniformity of radioactive sources prepared by traditional method and spin coating method

[0063] The uniformity of the radioactive source characterizes the quality characteristics of the prepared radioactive source. The present invention uses a self-made measuring device to measure the uniformity of the radioactive source. The device consists of a stainless steel base and an upper cover. The upper cover opens at an angle of 30°. The upper cover can be rotated on the base to expose different positions of the radioactive source. The edge of the base is marked with scales. A piece is taken out from the prepared radioactive source to measure its uniformity. The organic film area of ​​the radioactive source is divided into 12 areas by staggered parallel lines (parallel lines in the same direction are equally spaced). Each area is measured three times to obtain the average value. The measurement time of each measurement area is 60s. Finally, the relative standard deviation of the counts of the 12 areas is calculated. The results are shown in Table 9. As can be seen from Table 9, the relative standard deviation of the radioactive source prepared by the spin coating method in Example 1 of the present invention is 1.05%, and the relative standard deviation of the radioactive source prepared by the traditional method is 8.04%. The uniformity of the radioactive source prepared by the spin coating method in Example 1 of the present invention is significantly better than that of the radioactive source prepared by the traditional method.

[0064] Table 9 Results of uniformity test of radiation source

[0065] Note: 1 # The radiation source is the radiation source prepared by the spin coating method in Example 1 of the present invention; # The radioactive source is prepared by traditional methods.

[0066] 5. Test results of the firmness of organic films prepared by traditional method and spin coating method

[0067] The emissivity of the organic film prepared by the traditional method is 2.68×10 4 s -1 The emissivity of the organic film prepared by the spin coating method of Example 1 is 2.53×10 4 s -1 The organic film was wiped 30 times with a cotton ball moistened with deionized water, and then the emissivity of the organic film after wiping was measured. The emissivity of the organic film prepared by the traditional method after wiping was 2.23×10 4 s -1 , the loss rate is 16.79%; the emissivity of the organic film prepared by spin coating after wiping is 2.47×10 4 s -1 The loss rate is 2.37%. Therefore, the firmness of the organic film prepared by the spin coating method is better than that of the organic film prepared by the traditional method. The specific results are shown in Table 10.

[0068] Table 10 Test results of the firmness of organic films prepared by conventional methods and spin coating methods

[0069] Example 2

[0070] This embodiment provides a method for preparing a radioactive source. The preparation method is basically the same as that of Embodiment 1, except that in step (1), Ba 14 The amount of CO3 raw material used is 1g, the amount of acetone used is 14mL, the amount of ethylene glycol isooctyl ether used is 0.6g, the amount of oily polyurethane used is 5.85mL, and the stirring time is shortened to finally obtain 7mL of acetone in the raw material liquid.

[0071] The structure of the radiation source housing is the same as that of Example 1, except that the first groove is cylindrical, with a depth of 1.5 mm and a diameter of 30 mm. The second groove is cylindrical, with a depth of 0.8 mm and a diameter of 28 mm. The radiation source loading platform is cylindrical as a whole, with a height of 20 mm and an outer diameter of 45 mm. The mounting hole has a depth of 1.5 mm and a diameter of 2 mm. The pressure ring is a ring tube structure, with a height of 1.5 mm, an inner diameter of 28 mm and an outer diameter of 30 mm.

[0072] When the organic film is formed by spin coating, the low-speed coating time is set to 15s, the rotation speed is 1500 rpm, the high-speed coating time is set to 70s, the rotation speed is 5000 rpm, and after the spin coating is completed, the source shell is placed under an infrared lamp for 10 minutes for curing to obtain an organic film with a thickness of 600μm. The thickness of the aluminum film on the organic film is 30μm.

[0073] The final radioactive source was tested and the results showed that the parallelism range of the radioactive source was -3.98%~+4.75%, and the relative standard deviation of the uniformity was 0.92%.

[0074] Example 3

[0075] This embodiment provides a method for preparing a radioactive source. The preparation method is basically the same as that of Embodiment 1, except that in step (1), Ba 14 The amount of CO3 raw material used is 1g, the amount of acetone used is 26mL, the amount of ethylene glycol isooctyl ether used is 0.4g, the amount of oily polyurethane used is 16.25mL, and the stirring time is shortened to finally obtain 13mL of acetone in the raw material liquid. The structure of the radiation source shell is the same as that of Example 1.

[0076] The final radioactive sources were tested and the results showed that the parallelism of the radioactive sources (10 pieces) ranged from -5.46% to +5.88%, and the relative standard deviation of uniformity was 1.21%.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a radioactive source, which is substantially the same as Example 1, except that ethylene glycol isooctyl ether in the raw material liquid is replaced by fatty acid glyceride (wherein the fatty acid is C14 carboxylic acid).

[0079] The final radioactive sources were tested and the results showed that the parallelism of the radioactive sources (10 pieces) ranged from -8.75% to +9.68%, and the relative standard deviation of uniformity was 3.56%.

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing a radioactive source, which is substantially the same as Example 1, except that ethylene glycol isooctyl ether in the raw material liquid is replaced by sodium dodecylbenzene sulfonate.

[0082] The final radioactive sources were tested and the results showed that the parallelism of the radioactive sources (10 pieces) ranged from -10.21% to +11.53%, and the relative standard deviation of uniformity was 6.56%.

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing a radioactive source, which is substantially the same as Example 1, except that the oily polyurethane in the raw material liquid is replaced with an epoxy resin (molecular weight 3000-5000, epoxy value 0.25-0.45 mol / kg).

[0085] The final radioactive sources were tested and the results showed that the parallelism of the radioactive sources (10 pieces) ranged from -15.25% to +16.34%, and the relative standard deviation of uniformity was 13.21%.

[0086] Comparative Example 4

[0087] This comparative example provides a method for preparing a radioactive source, which is substantially the same as that of Example 1, except that the acetone content in the final raw material liquid is 15 mL, and the volume ratio of acetone to the oily polyurethane is 1.5:1.

[0088] The final radioactive sources were tested and the results showed that the parallelism of the radioactive sources (10 pieces) ranged from -12.45% to +13.78%, and the relative standard deviation of uniformity was 8.79%.

[0089] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a radioactive source, characterized in that: include: (1) A raw material solution for preparing an organic membrane; the raw material solution includes Ba 14 CO3, acetone, ethylene glycol isooctyl ether and oily polyurethane; Ba 14 The mass volume ratio of CO3 to acetone is 1: (7-13) g / mL; the volume ratio of acetone to oily polyurethane is (0.8-1.2): 1; Ba 14 The mass ratio of CO3 to ethylene glycol isooctyl ether is 1:(0.4-0.6); (2) spin coating the raw material liquid in the emission window of the radiation source housing and curing to form an organic film; (3) Covering the organic film with an aluminum-plated film, and fixing the aluminum-plated film in the radiation source housing.

2. The method according to claim 1, characterized in that The spin coating is carried out under vacuum, first at 1000-1500 rpm for 10-15 s, and then at 4000-5000 rpm for 60-70 s.

3. The method according to claim 1 or 2, characterized in that: The thickness of the cured organic film is 300-600 μm; the thickness of the aluminum-plated film is 10-30 μm.

4. The method according to any one of claims 1 to 3, characterized in that: The method for preparing the raw material liquid of the organic membrane comprises: firstly 14 CO3, ethylene glycol isooctyl ether, and acetone twice the formula amount are mixed and stirred in the presence of grinding media, and then mixed and stirred with oily polyurethane.

5. The method according to claim 4, characterized in that The stirring time for each time is 28-32 minutes; the grinding media are zirconia ceramic balls of various particle sizes; preferably, the particle sizes of the zirconia ceramic balls include 1 mm, 3 mm and 5 mm; more preferably, each 20 mL of acetone includes 10 zirconia ceramic balls with a diameter of 1 mm, 5 zirconia ceramic balls with a diameter of 3 mm, and 5 zirconia ceramic balls with a diameter of 5 mm.

6. The method according to any one of claims 1 to 5, characterized in that: The radiation source housing includes a pressure ring and a radiation source loading platform, a first groove is provided on the radiation source loading platform, a second groove is provided at the bottom of the first groove, the second groove is connected to the first groove, and the inner diameter of the second groove is smaller than the inner diameter of the first groove; the first groove is used to load the aluminum-plated film, and the second groove is used to load the organic film; the pressure ring can be nested and fixed in the first groove, and is used to fix the aluminum-plated film in the first groove; after the pressure ring is nested and fixed in the first groove, the inner wall surface of the pressure ring is flush with the inner wall surface of the second groove, exposing the organic film loaded in the second groove.

7. The method according to claim 6, characterized in that The first groove is cylindrical, with a depth of 1-1.5mm and a diameter of 5-30mm; the second groove is cylindrical, with a depth of 0.5-0.8mm and a diameter of 3-28mm; the pressure ring is a ring tube structure, with a height of 1-1.5mm, an inner diameter of 3-28mm and an outer diameter of 5-30mm; And / or, the radiation source loading platform is cylindrical as a whole, with a height of 10-30mm and an outer diameter of 15-50mm, and the outer wall of the radiation source loading platform has a thread; a mounting hole is provided on both sides of the first groove of the radiation source loading platform, which is circular, with a depth of 1-1.5mm and a diameter of 1-2mm; preferably, the cross-sections of the first groove and the second groove are concentric circles; the first groove is located at the center of the radiation source loading platform.

8. A radiation source, characterized in that: The method is prepared by any one of claims 1 to 7.

9. An organic film, characterized in that: As claimed in any one of claims 1 to 5.

10. Use of the radioactive source according to claim 8 or the organic film according to claim 9 in detecting PM 2.5 particles.

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