A radioactive source and a method of manufacturing and use thereof

Abstract

The present application relates to the technical field of radioactive source preparation, and specifically 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 comprises Ba 14 CO3, acetone, ethylene glycol iso-octyl ether and oil-based polyurethane; the mass-volume ratio of Ba 14 CO3 to acetone is 1: (7-13) g / mL; the volume ratio of acetone to oil-based polyurethane is (0.8-1.2):1; the mass ratio of Ba 14 CO3 to ethylene glycol iso-octyl ether is 1: (0.4-0.6); (2) spin-coating the raw material solution in an emission window of a radioactive source shell to form an organic film after solidification; (3) covering an aluminum film on the organic film, and fixing the aluminum film in the radioactive source shell. The radioactive source is simple to prepare, has high emissivity and good uniformity.

Description

Technical Field

[0001] This invention relates to the field of radioactive source preparation technology, and more specifically, to a radioactive source, its preparation method, and its application. Background Technology

[0002] Inhalation of PM2.5 particles is extremely harmful to human health, and it has been listed as one of the mandatory items for monitoring ambient air quality. Automatic beta-ray monitoring instruments are commonly used PM2.5 monitoring devices, capable of accurately measuring the concentration of PM2.5 in the air. C-14 nuclide has a half-life of 5730 years and emits pure beta rays with a maximum energy of 156.5 keV. The maximum range of the beta rays emitted by C-14 nuclide in air is 22 cm. Because C-14 nuclide is a low-toxicity nuclide and does not cause harm to humans, it has been widely used in PM2.5 monitoring.

[0003] The principle behind automatic beta-ray monitoring instruments for PM2.5 concentration is as follows: a C-14 beta-ray source emits beta rays that pass through a filter membrane collecting PM2.5 particles. The PM2.5 concentration is analyzed by measuring the attenuation of the beta rays after passing through the filter membrane. The emissivity of the C-14 beta-ray source is a crucial factor affecting the accuracy of PM2.5 monitoring results.

[0004] The conventional method for preparing C-14 β standard sources is to first prepare C-14 methacrylic acid monomers, then polymerize them into methyl methacrylate, coat the methyl methacrylate onto an aluminum substrate, and make it into an organic thin-film radioactive source. The conventional method faces the following problems: (1) The preparation process of C-14 methacrylic acid monomers is complex, with low yield and a high risk of radioactive contamination during preparation; (2) The polymerization of methacrylic acid monomers into methyl methacrylate has low reactivity, requiring increased temperature and the addition of catalysts, which easily generates radioactive aerosols; (3) Methyl methacrylate will solidify rapidly when coated on an aluminum sheet, and the coating thickness is difficult to control, resulting in poor uniformity of the radioactive source, which cannot meet the requirements of automatic β-ray detection instruments; (4) Due to the relatively low specific activity of C-14 methacrylic acid monomers, a thick organic film will result in significant obstruction of β particles, making it suitable for some low-emissivity standard sources, but not meeting the high-emissivity requirements of automatic β-ray monitoring instruments. Therefore, it is necessary to conduct further research on the preparation of radioactive sources. Summary of the Invention

[0005] One of the objectives of this invention is to provide a new and simple method for preparing C-14β radioactive sources with high emissivity and high uniformity.

[0006] This invention provides a method for preparing a radioactive source, comprising:

[0007] (1) A feed solution for preparing an organic membrane; the feed solution includes Ba 14 CO3, acetone, ethylene glycol isooctyl ether, and oil-based polyurethane; Ba 14 The mass-to-volume ratio of CO3 to acetone is 1:(7-13) g / mL; the volume ratio of acetone to oil-based 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).

[0008] (2) Spin-coating the raw material liquid into the emission window of the radioactive source casing and curing it to form an organic film;

[0009] (3) Cover the organic film with an aluminum-plated film and fix the aluminum-plated film in the radioactive source housing.

[0010] This invention has found that when radioactive organic materials are composited within the casing of a radioactive source, it is difficult to obtain a uniform coating (organic film), thus affecting the detection results. Therefore, this invention has continuously explored and ultimately discovered that using a specific surfactant and oil-based polyurethane in combination with acetone to perform Ba... 14 When CO3 is dispersed, Ba can be better utilized. 14 The CO3 is evenly dispersed, and a highly uniform coating is obtained during spin coating. Furthermore, when spin-coating with the raw material solution of this invention, uniformity can still be maintained even when the coating is very thin. This reduces the obstruction to β-particle emission by reducing the thickness of the organic film itself.

[0011] In this invention, the chemical formula of the oil-based polyurethane is (C 10 H8N2O2·C6H 14 O3) n The range of n is 500 to 20000.

[0012] In the method of the present invention, spin coating is performed under vacuum, first at 1000-1500 rpm for 10-15 seconds, then at 4000-5000 rpm for 60-70 seconds. Preferably, spin coating is first performed at 1000 rpm for 10 seconds, then at 4000 rpm for 60 seconds.

[0013] The spin coating method of the present invention is advantageous for obtaining a uniform organic film.

[0014] In the method of the present invention, the thickness of the cured organic film is 300-600 μm; the thickness of the aluminum-coated film is 10-30 μm.

[0015] In the method of the present invention, the method for preparing the raw material solution for the organic membrane includes: firstly, Ba... 14 CO3, ethylene glycol isooctyl ether, and acetone at twice the amount of the formula are mixed and stirred in the presence of grinding media, and then mixed and stirred with oil-based polyurethane.

[0016] The mixing method of this invention facilitates the uniform mixing of all components. Acetone is easily volatile at room temperature; therefore, this invention preferably adds twice the amount of acetone in the formulation to avoid insufficient acetone content in the final raw material solution due to acetone evaporation during mixing and stirring, which would affect the subsequent spin coating effect.

[0017] In the method of the present invention, the stirring time is 28-32 minutes each time; the grinding medium is zirconia ceramic balls of various particle sizes; preferably, the particle size of the zirconia ceramic balls includes 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.

[0018] In the method of the present invention, the radioactive source housing includes a pressure ring and a radioactive source loading stage. The radioactive source loading stage is provided with a first groove, and a second groove is provided at the bottom of the first groove. The second groove communicates with 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 aluminized film, and the second groove is used to load the organic film. The pressure ring can be nested and fixed in the first groove to fix the aluminized 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.

[0019] 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 coiled 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.

[0020] And / or, the radioactive source load stage is cylindrical in shape, with a height of 10-30mm (preferably 8-20mm) and an outer diameter of 15-50mm, and the outer wall of the radioactive source load stage has threads; a mounting hole is provided on each side of the first groove of the radioactive source load stage, which is circular, with a depth of 1-1.5mm and a diameter of 1-2mm, for mounting the radioactive source on the instrument for fixation; 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 radioactive source load stage.

[0021] The radioactive source housing structure of the present invention is simple and easy to assemble. The aluminum-plated film can be fixed by placing the aluminum-plated film above the first groove of the radioactive source load stage, pressing it down from above with a pressure ring, and then cutting off the excess aluminum-plated film exposed at the edge of the pressure ring.

[0022] The present invention also provides a radioactive source prepared by the above method.

[0023] The present invention also provides an organic membrane, as described above.

[0024] The organic membrane of this invention can emit β particles and can be used in a variety of detection fields.

[0025] The present invention also provides the application of the above-mentioned radioactive source or organic membrane in the detection of PM 2.5 particles.

[0026] The beneficial effects of this invention are at least as follows:

[0027] The method of this invention is simple, and the prepared β-plane source has low β-particle loss and a β-particle surface emissivity of up to 10. 6 s -1 Organic membranes have advantages such as good robustness, high utilization rate of radionuclides, high uniformity (deviation of less than 3% in each part), and safety and reliability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the C-14β radioactive source of the present invention.

[0029] Figure 2 This is a physical image of the source shell of the C-14 β radioactive source of the present invention.

[0030] Figure 3 This is a physical image of the C-14 β radioactive source after its preparation is completed. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available or prepared according to conventional methods in the art. Oil-based polyurethane was purchased from Shenzhen Yoshida Chemical Co., Ltd., product number E1401. The main equipment and reagents involved in this invention are shown in Tables 1 and 2.

[0033] Table 1

[0034]

[0035] Table 2

[0036]

[0037] Example 1

[0038] This embodiment provides a method for preparing a radioactive source, as detailed below:

[0039] (1) Take 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 10 mm diameter magnetic stirrers and ten 1 mm, five 3 mm, and five 5 mm diameter zirconia ceramic balls were added, with the zirconia ceramic balls serving as the grinding medium. The mixture was stirred with a magnetic stirrer for 30 min, resulting in a uniformly distributed carbonate powder suspension. Then, 10 mL of oily polyurethane was added, and the mixture was stirred magnetically for another 30 min to obtain the final raw material solution (which will be used to prepare an organic membrane, containing 10 mL of acetone).

[0040] (2) Take 10 μL of raw material solution and measure its activity value A0 using a liquid scintillation spectrometer. Calculate the amount of raw material solution V1 to be used according to the requirement of the activity value A1 of the radioactive source. V1 = A1 / A0 × 10 μL / B; where B is the blocking coefficient of the organic film and the aluminum film. In this embodiment, A1 is 100 μCi, A0 is 0.8 μCi, and B is 0.37.

[0041] (3) The radioactive source housing is used for the preparation of the radioactive source. The radioactive source housing includes a pressure ring and a radioactive source loading stage. The radioactive source loading stage has a first groove at its center. The first groove is cylindrical, with a depth of 1 mm and a diameter of 8 mm. A second groove is provided at the bottom of the first groove, and the second groove is connected to the first groove. The second groove is cylindrical, with a depth of 0.5 mm and 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 together 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 an aluminum-plated film, and the second groove is used to load an organic film.

[0042] The radioactive source loading platform is cylindrical, with a height of 8 mm and an outer diameter of 20 mm. It has threads on its cylindrical outer wall for assembly with other components that require the installation of radioactive sources. A circular mounting hole, 1 mm deep and 1.5 mm in diameter, is provided on each side of the first groove of the radioactive source loading platform for mounting the radioactive source onto the instrument.

[0043] The pressure ring has a coiled tube structure with a height of 1mm, an inner diameter of 6mm, and an outer diameter of 8mm. The pressure ring is tightly fitted into the first groove and nested within it to fix the aluminum-plated film within the first groove. After the pressure ring is nested and fixed to 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 at the bottom of the second groove.

[0044] Take the raw material liquid of V1 prepared according to the method of step (1) and add it into the second groove (emission window) of the radioactive source load stage. After adding the raw material, stick double-sided tape on the bottom of the radioactive source load stage and fix it on the turntable of the thin film spin coater. Then, vacuum is applied. The low-speed spin coating time is set to 10s and the rotation speed is 1000 rpm. The high-speed spin coating time is set to 60s and the rotation speed is 4000 rpm. After spin coating, place the source shell under the infrared lamp for 10min to cure and obtain an organic film with a thickness of 300μm.

[0045] (4) Cut a 10μm thick aluminum-coated film on the anti-cutting plate with a cutter. Place the aluminum-coated film above the first groove of the radiation source load stage. Press down on the aluminum-coated film from above using a pressure ring. Then cut off the excess aluminum-coated film exposed at the edge of the pressure ring. The pressure ring carries the aluminum-coated film and is nested and fixed in the first groove. The inner sidewall and bottom end face of the first groove are covered with the aluminum-coated film, and the organic film in the second groove is sealed under the aluminum-coated film.

[0046] (5) Wipe the radioactive source gently with an alcohol swab to remove contamination. After drying, place the radioactive source on the measuring tray of the α and β rapid measuring instrument for activity measurement. The activity value is qualified if it is within the range of 0.85~1.15A1.

[0047] (6) Then conduct surface contamination and leakage inspection. The measured value of surface contamination should be lower than the national standard requirement of 200 Bq.

[0048] (7) Finally, conduct an appearance inspection. The surface of the source is smooth and flat, with no damage.

[0049] See the schematic diagram of the radioactive source. Figure 1 See the physical image of the radioactive source shell. Figure 2 A photograph of the completed radioactive source can be found here. Figure 3 .

[0050] Experiment Example 2

[0051] This experimental example tests the radioactive source prepared by spin coating in Example 1, as follows:

[0052] 1. Experiment on the blocking law of self-absorption and aluminized film

[0053] According to the liquid scintillation spectrometer measurement results, the emissivity of 50 μL of the feed solution is 561500 s.-1 The theoretical value measured using a rapid α and β activity measuring instrument should be 28075 cps. The instrument was used at a distance of 3 cm, and its detection efficiency was approximately 5%. The results are shown in Table 3. The actual measured value of the organic film prepared by spin coating in Example 1 of this invention was reduced by 20.21% compared to the theoretical value, mainly because the organic film blocked some of the emission of β particles after curing. The blocking rate of the 10 μm thick aluminized film for β particles is about 17%. After sealing the aluminized film, the instrument measurement value was 17706 cps, and the actual emissivity was 3.54 × 10⁻⁶ cps. 5 s -1 The aluminum-coated film ensures safety performance without excessively blocking β particles.

[0054] Table 3 Experimental results on the self-absorption of organic membranes and the blocking effect of aluminized films.

[0055]

[0056] 2. Parallelism Experiment

[0057] Ten radioactive sources were prepared using the spin-coating method described in Example 1. Activity was measured using a rapid α and β activity measurement instrument, and the results are shown in Table 4. The calculated deviation range was -4.61% to +5.11%, all within the expected range of -15% to +15%.

[0058] Table 4 Parallelism Experiment of Radioactive Sources Prepared by Spin-Coating Method

[0059]

[0060] 3. Surface contamination and leakage inspection

[0061] Ten radioactive sources were prepared according to the method of Example 1 of this invention and tested. The results are shown in Table 5. It can be seen that the maximum value of 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 spin coating method of Example 1 has good sealing performance.

[0062] Table 5. Surface contamination and leakage inspection results

[0063]

[0064] Experiment Example 2

[0065] This experimental example uses a rapid α and β activity measurement instrument at a distance of 3 cm (the instrument's detection efficiency is approximately 5%). The experimental data of the radioactive source prepared by the spin-coating method in Example 1 of this invention are compared with those obtained by the traditional method (see Chapter 9, Application of Radioactive Standard Sources, Section 3, Preparation Methods of Carbon-14 and Hydrogen-3 Standard Sources, in Sun Shuzheng's "Preparation and Application of Radioactive Sources"), as detailed below:

[0066] 1. Comparison of barrier efficiency between organic films prepared by traditional methods and spin coating methods

[0067] The blocking efficiency results of the organic films are shown in Table 6. The actual measured emissivity of the organic films prepared by the conventional method was 57.11% lower than the theoretical value. This is mainly because the conventional method uses C-14 methacrylic acid monomer, whose specific activity ranges from 10 to 15 mCi / g. This low specific activity leads to a thicker organic film, and the thickness of the organic films prepared by the conventional method is also uneven, with thicker areas blocking more β-particles. In Example 1 of this invention, the actual measured emissivity of the organic film prepared by spin coating was 20.21% lower than the theoretical value, indicating that the organic film blocked the emission of some β-particles after curing.

[0068] Table 6. Comparison of barrier efficiency of organic films prepared by traditional methods and spin coating.

[0069]

[0070] 2. Comparison of experimental data on the parallelism of radioactive sources prepared by traditional methods and spin coating methods

[0071] Ten radioactive sources were prepared using both the conventional method and the spin-coating method. Activity measurements were performed using a rapid α and β activity measuring instrument, and the statistical results are shown in Table 7. The calculated activity deviation range for the radioactive sources prepared by the conventional method was -18.33% to +20.42%, with four sources having activities outside the expected range of -15% to +15%. The activity deviation range for the radioactive sources prepared by the spin-coating method in Example 1 of this invention was -4.61% to +5.11%, all within the expected range of -15% to +15%.

[0072] Table 7. Comparison of parallelism experimental data for radioactive sources prepared by traditional methods and spin coating methods.

[0073]

[0074] 3. Comparison of the highest emissivity of radioactive sources prepared by traditional methods and spin coating methods (measured directly using a rapid α and β activity meter).

[0075] The highest emissivity of a radioactive source prepared by conventional methods is 3.33 × 10⁻⁶. 5 s -1This method cannot meet the highest usage requirements of automatic beta-ray monitoring instruments. The highest emissivity of the radioactive source prepared by the spin-coating method in Example 1 of this invention is 1.57 × 10⁻⁶. 6 s -1 It fully meets the highest usage requirements for automatic beta-ray monitoring instruments. The comparison results are shown in Table 8.

[0076] Table 8 Comparison of the highest emissivity of radioactive sources prepared by traditional methods and spin coating method

[0077]

[0078] 4. Results of homogeneity testing of radioactive sources prepared by traditional methods and spin coating methods

[0079] The uniformity of a radioactive source characterizes its quality. This invention uses a self-made measuring device to measure the uniformity of the radioactive source. This device consists of a stainless steel base and a top cover. The top cover has a 30° opening and can rotate on the base, exposing different positions of the radioactive source. The base edge is marked with graduations. A piece of the prepared radioactive source is extracted, and its uniformity is measured. The organic film region of the radioactive source is divided into 12 regions using interlaced parallel lines (parallel lines in the same direction are equally spaced). Each region is measured three times, and the average value is calculated. The measurement time for each region is 60 seconds. Finally, the relative standard deviation of the counts for the 12 regions is calculated. The results are shown in Table 9. Table 9 shows that the relative standard deviation of the radioactive source prepared by the spin-coating method in Example 1 of this invention is 1.05%, while 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 this invention is significantly better than that of the radioactive source prepared by the traditional method.

[0080] Table 9. Results of the homogeneity test of the radioactive source

[0081]

[0082] Note: 1 # The radioactive source is the radioactive source prepared by spin coating in Example 1 of this invention; 2 # The radioactive source was prepared using conventional methods.

[0083] 5. Test results of the adhesion of organic films prepared by traditional methods and spin coating methods

[0084] The emissivity of the organic film prepared by the conventional method is 2.68 × 10⁻⁶. 4 s -1 The emissivity of the organic film prepared by spin coating according to Example 1 is 2.53 × 10⁻⁶. 4 s -1The organic membrane was wiped 30 times with a cotton ball moistened with deionized water, and then the emissivity of the membrane after wiping was measured. The emissivity of the organic membrane prepared by the traditional method after wiping was 2.23 × 10⁻⁶. 4 s -1 The loss rate was 16.79%; the emissivity of the organic film prepared by spin coating after wiping was 2.47 × 10⁻⁶. 4 s -1 The loss rate was 2.37%; therefore, the organic film prepared by spin coating has better adhesion than that prepared by traditional methods. Specific results are shown in Table 10.

[0085] Table 10 Results of the adhesion test of organic films prepared by traditional methods and spin coating methods

[0086]

[0087] Example 2

[0088] This embodiment provides a method for preparing a radioactive source, which is basically the same as that in Example 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, and the amount of oil-based polyurethane is 5.85mL. By shortening the stirring time, the final acetone content in the raw material solution is 7mL.

[0089] The structure of the radioactive source casing is the same as in Embodiment 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 radioactive source load stage is cylindrical in shape, 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 coiled tube structure with a height of 1.5 mm, an inner diameter of 28 mm, and an outer diameter of 30 mm.

[0090] When spin-coating to form the organic film, the low-speed spin coating time was set to 15 seconds at a speed of 1500 rpm, and the high-speed spin coating time was set to 70 seconds at a speed of 5000 rpm. After spin coating, the source shell was placed under an infrared lamp for 10 minutes for curing to obtain an organic film with a thickness of 600 μm. The thickness of the aluminum film coated on the organic film was 30 μm.

[0091] The obtained radioactive source was tested, and the results showed that the parallelism of the radioactive source ranged from -3.98% to +4.75%, and the relative standard deviation of the homogeneity was 0.92%.

[0092] Example 3

[0093] This embodiment provides a method for preparing a radioactive source, which is basically the same as that in Example 1, except that in step (1), Ba14 The amount of CO3 raw material used was 1g, the amount of acetone was 26mL, the amount of ethylene glycol isooctyl ether was 0.4g, and the amount of oil-based polyurethane was 16.25mL. By shortening the stirring time, the final acetone content in the raw material solution was 13mL. The structure of the radioactive source shell was the same as in Example 1.

[0094] The final obtained radioactive sources were tested, and the results showed that the parallelism of the radioactive sources (10 sources) ranged from -5.46% to +5.88%, and the relative standard deviation of the homogeneity was 1.21%.

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing a radioactive source, which is basically the same as that in Example 1, except that the ethylene glycol isooctyl ether in the raw material solution is replaced with fatty acid glycerides (wherein the fatty acids are C14 carboxylic acids).

[0097] The final obtained radioactive sources were tested, and the results showed that the parallelism of the radioactive sources (10 sources) ranged from -8.75% to +9.68%, and the relative standard deviation of the homogeneity was 3.56%.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a radioactive source, which is basically the same as that in Example 1, except that ethylene glycol isooctyl ether in the raw material solution is replaced with sodium dodecylbenzenesulfonate.

[0100] The final obtained radioactive sources were tested, and the results showed that the parallelism of the radioactive sources (10 sources) ranged from -10.21% to +11.53%, and the relative standard deviation of the homogeneity was 6.56%.

[0101] Comparative Example 3

[0102] This comparative example provides a method for preparing a radioactive source, which is basically the same as that in Example 1, except that the oily polyurethane in the raw material solution is replaced with epoxy resin (molecular weight 3000~5000, epoxy value 0.25~0.45mol / kg).

[0103] The final obtained radioactive sources were tested, and the results showed that the parallelism of the radioactive sources (10 sources) ranged from -15.25% to +16.34%, and the relative standard deviation of the homogeneity was 13.21%.

[0104] Comparative Example 4

[0105] This comparative example provides a method for preparing a radioactive source, which is basically the same as that in Example 1, except that the final raw material solution contains 15 mL of acetone, and its volume ratio with oil-based polyurethane is 1.5:1.

[0106] The final obtained radioactive sources were tested, and the results showed that the parallelism of the radioactive sources (10 sources) ranged from -12.45% to +13.78%, and the relative standard deviation of the homogeneity was 8.79%.

[0107] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention 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 feed solution for preparing an organic membrane; the feed solution includes Ba 14 CO3, acetone, ethylene glycol isooctyl ether, and oil-based polyurethane; Ba 14 The mass-to-volume ratio of CO3 to acetone is 1:(7-13) g / mL; the volume ratio of acetone to oil-based 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 into the emission window of the radioactive source casing and curing it to form an organic film; (3) Cover the organic film with an aluminum-plated film and fix the aluminum-plated film in the radioactive source housing.

2. The method according to claim 1, characterized in that, Spin coating is performed under vacuum. First, spin coat at 1000~1500 rpm for 10~15 seconds, then spin coat at 4000~5000 rpm for 60~70 seconds.

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

4. The method according to claim 1 or 2, characterized in that, The method for preparing the feed solution for organic membranes includes: first, Ba... 14 CO3, ethylene glycol isooctyl ether, and acetone (twice the amount of the formula) are mixed and stirred in the presence of grinding media, and then mixed and stirred with oil-based polyurethane.

5. The method according to claim 4, characterized in that, Each stirring session lasts 28-32 minutes; the grinding media consists of zirconia ceramic balls of various particle sizes.

6. The method according to claim 5, characterized in that, The zirconia ceramic balls have particle sizes of 1 mm, 3 mm, and 5 mm.

7. The method according to claim 6, characterized in that, Each 20 mL of acetone contains 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.

8. The method according to claim 1, characterized in that, The radioactive source housing includes a pressure ring and a radioactive source loading platform. The radioactive source loading platform has a first groove and a second groove at the bottom of the first groove. The second groove communicates with 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 aluminized film, and the second groove is used to load the organic film. The pressure ring can be nested and fixed in the first groove to fix the aluminized 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.

9. The method according to claim 8, characterized in that, 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 coiled 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 radioactive source load stage is cylindrical in shape, with a height of 10-30mm and an outer diameter of 15-50mm, and the outer wall of the radioactive source load stage has threads; a mounting hole is provided on each side of the first groove of the radioactive source load stage, which is circular, with a depth of 1-1.5mm and a diameter of 1-2mm.

10. The method according to claim 9, characterized in that, The first groove and the second groove have concentric circles in cross-section; the first groove is located at the center of the radiation source load stage.

11. A radioactive source, characterized in that, It is prepared by the method according to any one of claims 1-10.

12. The use of the radioactive source of claim 11 in the detection of PM 2.5 particles.

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