Method for detecting activity concentration of 238U and 232Th in trona ore

Abstract

The invention discloses a method for detecting the activity concentration of 238U and 232Th in trona ore, and belongs to the technical field of inspection and detection. Comprising the following steps: S1, sample processing; grinding the trona ore at the temperature of less than 50 DEG C until the particle size is less than 100 meshes, drying, and immediately sealing and storing; s2, sample digestion; the method comprises the following steps: wetting a sample with water, dropwise adding hydrochloric acid until a violent reaction is stopped, evaporating to dryness, sequentially adding concentrated hydrochloric acid, concentrated nitric acid, hydrofluoric acid and perchloric acid, carrying out stepped heating dissolution and acid removal, and finally extracting with nitric acid to a constant volume; s3, measuring the mass concentration of the solution by a mass spectrometry method; measuring the mass concentration of 238U and 232Th in the solution by adopting inductively coupled plasma mass spectrometry and taking Re as an on-line internal standard; s4, calculating a result; and obtaining the activity concentration of the natural radionuclides 238U and 232Th in the measured trona ore through the mass-activity relation coefficient of the radionuclides.

Description

Technical Field

[0001] This invention relates to the field of testing and inspection technology, and in particular to a natural alkali ore. 238 U and 232 Methods for detecting Th activity concentration. Background Technology

[0002] Natural alkali ore is a mineral resource rich in carbonates (such as sodium bicarbonate and sodium carbonate). During its mining, processing, and utilization, it is necessary to remove naturally occurring radioactive nuclides (such as sodium carbonate, sodium bicarbonate, etc.). 238 U and 232 The activity concentration of Th was measured to assess its radiation safety risks and environmental impact.

[0003] However, due to the unique physicochemical properties of natural alkali ore: firstly, the sodium bicarbonate it contains is easily decomposed at temperatures above 50°C, and the ore is also hygroscopic, causing conventional sample processing methods such as high-temperature drying and open storage to lead to changes in composition or sample deterioration; secondly, its main component is carbonate, which reacts violently with concentrated acid to release carbon dioxide, easily causing solution splashing and sample loss, and the silicon in the ore needs to be removed to prevent the analyte elements mixed with silicates from being undetectable; in addition, it contains... 238 U and 232 The activity concentration of Th is extremely low, and conventional detection methods (such as high-purity germanium gamma spectroscopy) are not sensitive enough.

[0004] Therefore, conventional radionuclide detection methods have significant limitations in application, and there is still a lack of methods specifically designed for the characteristics of natural alkali ore. 238 U and 232 Th activity concentration detection method. Summary of the Invention

[0005] The purpose of this invention is to address the significant limitations of existing conventional radionuclide detection methods due to the unique physicochemical properties of natural alkali ore (sodium bicarbonate is easily decomposed at high temperatures and deliquescent, carbonates react violently with concentrated acids, silica matrix interference, and extremely low activity of the target nuclide), and the lack of targeted detection methods. Therefore, this invention proposes a method for detecting radionuclides in natural alkali ore. 238 U and 232 Methods for detecting Th activity concentration.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a natural alkali ore 238 U and 232 The method for detecting Th activity concentration includes the following detection steps: S1. Sample processing: Grind the natural alkali ore at <50℃ until the particle size is less than 100 mesh, dry it and then seal it for storage immediately. S2, sample digestion; first, wet the sample with water, add hydrochloric acid dropwise until the reaction stops violently, evaporate to dryness, then add concentrated hydrochloric acid, concentrated nitric acid, hydrofluoric acid and perchloric acid in turn, dissolve and chase acid by stepwise heating, and finally extract with nitric acid to constant volume; S3, mass spectrometry method for measuring the mass concentration of the solution; using inductively coupled plasma mass spectrometry, Re as an online internal standard, measuring the mass concentration of U and Th in the solution 238 U and 232 Th in the solution; S4, result calculation; multiplying the net mass concentration of U and Th measured by the mass spectrometry method by the solution constant volume, dividing by the original sample mass, and multiplying by the mass-activity relationship coefficient of the radionuclide, to obtain the activity concentration of the natural radionuclides U and Th in the measured natural soda ore 238 U and 232 Th in the measured natural soda ore. 238 U and 232 Th in the measured natural soda ore.

[0007] In some embodiments, the step S1 specifically includes: Grinding is carried out by using a corundum jar-maifan ball vibration grinder, running in intermittent grinding mode, stopping for 1 min every 3 min of grinding; The drying temperature is 45℃, and the time is 4h; Sealed storage uses a plastic bottle, and the packaging is completed within 30 min after grinding.

[0008] In some embodiments, the digestion operation in the step S2 specifically includes: S21, weighing 0.2000 sample, adding 2ml high-purity water to wet; S22, adding 1+1 hydrochloric acid dropwise until no bubbles are generated, and evaporating to dryness at low temperature; S23, adding 2ml concentrated hydrochloric acid, 6ml concentrated nitric acid, 5ml hydrofluoric acid and 1ml perchloric acid in turn; S24, heating to dissolve at 140℃ for 2h, and then increasing the temperature to 230℃ until the white smoke disappears; S25, extracting the residue with 5ml 1+3 nitric acid, and constant volume to 50ml.

[0009] In some embodiments, the mass spectrometry detection in the step S3 meets: Tuning selection 238 U, 232 Th as the detection mass number; The online internal standard is 10μg / L Re solution, and the monitoring mass number is 185; Before measurement, a calibration curve is established, and the sample blank is detected synchronously.

[0010] In some embodiments, the isotopic abundance in the standard solution is set according to the following rules: 238U abundance is 0.992742 when not specified; 232 Th abundance is 1 when not specified.

[0011] In some embodiments, the amount of hydrofluoric acid added in step S2 is 5ml, which is used to remove the silicon substrate in the form of SiF4.

[0012] In some embodiments, the total recovery rate is controlled at 97%-103% by adding 0.50ug 238 U and 1.00ug 232 Th standard solution to achieve quality control.

[0013] In some embodiments, in step S4, the unit of the net mass concentration is ng / ml, and the solution volume is 50ml.

[0014] In some embodiments, in step S4, the mass-activity relationship coefficient is: 1ng 238 U is converted into radioactivity 1.2437E-5Bq, 1ng 232 Th is converted into radioactivity 4.0719E-6Bq.

[0015] In some embodiments, in step S2, the reaction is carried out in a 100ml Teflon beaker with a cover, and the spatter is controlled by adding acid step by step through the cover.

[0016] Compared with the prior art, the present application provides a detection method for the activity concentration of 238 U and 232 Th in natural soda ore.

[0017] 1、The present application controls the temperature rise of grinding (<50℃) by intermittent grinding (1min stop for every 3min operation) + corundum tank - agate ball (low thermal conductivity)”, combined with low temperature drying at 45℃, to avoid the decomposition of sodium bicarbonate; at the same time, the sample is immediately transferred into a plastic bottle for sealing after processing, to isolate the external humidity and solve the problem of deliquescence, so as to ensure the stability of the matrix components related to U and Th in the sample, avoid the loss or deterioration of target nuclides caused by the processing process, and provide a reliable sample basis for subsequent detection. 238 U and 232 Th related matrix components stable, avoid the loss or deterioration of target nuclides caused by the processing process, and provide a reliable sample basis for subsequent detection.

[0018] 2, The application controls the reaction rate of carbonate and acid by "water wetting -> dropwise adding 1+1 hydrochloric acid", cooperates with a beaker with a cover to reduce the risk of splashing; subsequently, concentrated hydrochloric acid, nitric acid, hydrofluoric acid (silicon removal, generating SiF4 volatilization), and perchloric acid (promoting decomposition) are sequentially added, and complete dissolution of the sample is ensured through stepwise heating (140 DEG C dissolution, 230 DEG C acid removal). Both sample loss caused by violent reaction and matrix interference are eliminated through silicon removal by hydrofluoric acid and the synergistic effect of multiple acids, ensuring 238 U and 232 Th completely enter the solution, improving the accuracy of subsequent measurement.

[0019] 3, The application selects a mass spectrometry method with higher sensitivity, corrects matrix effect and instrument fluctuation through "online Re internal standard (10 ug / L, mass number 185)", combines "calibration curve + sample blank deduction" to capture weak signals, ensures measurement accuracy at low concentration, realizes accurate measurement of extremely low activity nuclides, and verifies the high accuracy of the method through the full-process standard addition recovery rate (97%-103%) of 59 groups of samples, solving the technical problems that cannot be detected by conventional methods.

[0020] 4, The whole process from sample processing to result calculation is designed for the characteristics of natural soda ore, and each step parameter is clear (such as grinding particle size, reagent dosage, heating temperature, etc.), and the repeatability and stability of the method are verified through a large number of measured data. Form a complete and popular detection scheme, fill the technical blank of 238 U and 232 Th activity concentration detection in natural soda ore, and provide reliable technical support for its mining, processing and environmental risk assessment.

[0021] Other advantages, objects and features of the application will be described in the subsequent description; and to some extent, it will be obvious to those skilled in the art based on the study of the following; or can be taught from the practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the method of the application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the application will be described in detail below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all.

[0024] Referring to Figure 1 A method for detecting 238 U and 232A method for detecting the activity concentration of Th, comprising the following detection steps: S1, sample processing; since the sodium bicarbonate contained in the trona ore will decompose at a temperature higher than 50℃, the temperature needs to be strictly controlled during sample grinding and drying.

[0025] The specific operation is as follows: the trona ore sample is ground to less than 100 mesh by a vibration grinder (corundum jar - agate ball) to ensure sample uniformity and meet the subsequent digestion requirements; the grinding process is intermittent grinding, and the instrument is stopped for 1 min every 3 min; then it is dried in a 45℃ oven for 4 hours, and then sealed in a plastic bottle for storage before testing.

[0026] Among them, by adopting the method of "intermittent grinding", the heat accumulation generated by the friction of the equipment during grinding is reduced, and the decomposition of sodium bicarbonate caused by local temperature exceeding 50℃ is avoided; at the same time, corundum jar - agate ball is selected as the grinding part, which has low thermal conductivity, further reducing the risk of temperature rise during grinding. The drying temperature in the oven is kept at 45±2℃, which is lower than the critical value of 50℃, which not only ensures the drying of the sample, but also strictly avoids the decomposition of sodium bicarbonate caused by high temperature, and ensures the stability of the target components (including Th related matrix) in the sample. 238 U、 232 Th related matrix).

[0027] At the same time, since the trona ore has the characteristics of easy deliquescence, after the sample is ground and dried in step S1, because the plastic bottle has good sealing performance, it can isolate the external humidity; therefore, the operation requirement of "immediately transferred into a plastic bottle for sealing storage" shortens the time of the sample exposed to the air to the maximum, avoids its deliquescence caused by absorbing water, and ensures the consistency and representativeness of the sample state in the subsequent digestion and measurement links.

[0028] In summary, step S1 solves the sample loss or deterioration problem caused by the special physical and chemical properties of trona ore from two aspects of temperature control (anti-decomposition) and sealing time (anti-deliquescence), which provides a basic guarantee for the accuracy of subsequent detection.

[0029] S2, sample digestion; since the main component of the sample is carbonate, direct addition of concentrated acid will cause sample spatter, so it is necessary to add hydrochloric acid drop by drop after wetting with water and gently shake the beaker to allow carbon dioxide to slowly precipitate; the introduction of other acids is to make the sample decompose completely and Si to generate SiF4 to remove.

[0030] The specific procedure is as follows: Accurately weigh 0.2g of sample (accurate to 0.0001g) and place it in a 100ml polytetrafluoroethylene beaker with a lid. Add 2ml of high-purity water to moisten the sample. Add 1+1 hydrochloric acid dropwise while gently shaking the beaker until the violent reaction stops. Then, evaporate the sample to dryness on a hot plate at low temperature. Add 2ml of concentrated hydrochloric acid, 6ml of concentrated nitric acid, 5ml of hydrofluoric acid, and 1ml of perchloric acid in sequence. Place the beaker on a hot plate and heat at 140℃ for 2 hours to dissolve the sample. Then, raise the temperature of the hot plate to 230℃ until the white fumes stop. Use 5ml of 1+3 nitric acid to extract the residue with warm heat. Rinse the beaker and lid with pure water. Transfer the entire solution to a 50ml volumetric flask. After cooling, dilute to volume with pure water and shake well. This solution is the test solution.

[0031] S3, mass spectrometry method for measuring the mass concentration of the solution; due to the presence of natural alkali ore 238 U and 232 The activity concentration of Th is relatively low, generally between 0.00n-0.0nBq / g, making it difficult to measure using other methods such as high-purity germanium gamma spectroscopy. Therefore, this invention chose a more sensitive mass spectrometry method for measurement.

[0032] The specific operation is as follows: Start the instrument according to the conditions specified in the instrument manual, preheat for 30 minutes, and then perform tuning. Select a uranium mass number of 238, a thorium mass number of 232, and a Re solution with an online internal standard of 10 μg / L (select a mass number of 185 during measurement). Measure the calibration curve, sample blank, and sample solution sequentially to obtain the concentration of Re in the solution. 238 U and 232 Net mass concentration of Th (ng / ml); of which, in the standard solution 238 U and 232 For Th isotope abundance reference standard material certificates, such as those for natural uranium and thorium, if the isotope abundance is not specified, then [the relevant standard material certificate should be used]. 238 The isotopic abundance of U is 0.992742. 232 The isotopic abundance of Th is 1.

[0033] S4. Result calculation, i.e., activity concentration conversion; since mass spectrometry measures mass concentration, it is necessary to convert the radioactivity concentration based on the relationship between the mass and activity of the radionuclide.

[0034] Specifically, it refers to measurements obtained using mass spectrometry. 238 U and 232 The net mass concentration of Th (ng / ml) multiplied by the final volume of the solution (50 ml), divided by the original sample mass, and then multiplied by the mass-activity coefficient of the radionuclide (1 ng / ml). 238 U converted to radioactivity is 1.2437E-5 Bq; 1 ng232 Th converted to radioactivity (4.0719E-6 Bq) to obtain the measured natural alkali ore natural radionuclide 238 U and 232 Th activity concentration (Bq / g).

[0035] The measured sample and the overall standard addition recovery rate are shown in Table 1 below Table 1 In summary, the present application controls the grinding temperature rise (<50℃) by intermittent grinding (3min running and 1min stopping) + corundum tank + agate ball (low thermal conductivity), combined with low-temperature drying at 45℃ to avoid sodium bicarbonate decomposition; at the same time, the sample is immediately sealed in a plastic bottle after processing, which isolates the external humidity and solves the deliquescence problem, ensuring the stability of the matrix components related to U and Th in the sample, avoiding the loss or deterioration of the target nuclides caused by the processing process, and providing a reliable sample basis for subsequent detection. 238 U and 232 Th-related matrix components are stable, avoiding loss or deterioration of target nuclides caused by the processing process, and providing a reliable sample basis for subsequent detection.

[0036] By controlling the reaction rate of carbonates and acid through "wetting with water → adding 1+1 hydrochloric acid drop by drop", and reducing the risk of splashing with a beaker with a lid, and then adding concentrated hydrochloric acid, nitric acid, hydrofluoric acid (to remove silicon, generating SiF4 volatilization), and perchloric acid (to promote decomposition), and ensuring complete dissolution of the sample through stepwise heating (140℃ dissolution, 230℃ acid removal), it can not only avoid sample loss caused by violent reaction, but also eliminate matrix interference through the synergistic effect of hydrofluoric acid and multiple acids, ensuring that U and 238 U and 232 Th completely enter the solution, improving the accuracy of subsequent measurement.

[0037] By selecting a more sensitive mass spectrometry method, correcting matrix effects and instrument fluctuations through "online Re internal standard (10μg / L, mass number 185)", and capturing weak signals through "calibration curve + sample blank deduction", the measurement accuracy at low concentration is ensured, and accurate measurement of extremely low activity nuclides is achieved. The overall standard addition recovery rate of 59 groups of samples (97%-103%) can verify the high accuracy of the method, and solve the technical problems that cannot be detected by conventional methods.

[0038] The present application is designed for the characteristics of natural alkali ore from sample processing to result calculation, and the parameters of each step are clear (such as grinding particle size, reagent dosage, heating temperature, etc.), and the repeatability and stability of the method are verified through a large number of measured data. A complete and generalizable detection scheme is formed, filling the technical gap in the detection of U and 238 U and 232The activity concentration detection technology of Th provides reliable technical support for mining, processing and environmental risk assessment.

[0039] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be encompassed within the protection scope of the present application.

[0040] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

Claims

1. A method for the determination of the activity concentration of U and Th in a trona ore, characterized in that 238 U and 232 Th activity concentration, characterized in that The method comprises the following detection steps: S1, sample processing; grinding the natural soda ore to a particle size of less than 100 mesh at a temperature of less than 50 DEG C, and immediately sealing and storing after drying; S2, sample digestion; first, wetting the sample with water, adding hydrochloric acid dropwise until the reaction stops, evaporating to dryness, and then adding concentrated hydrochloric acid, concentrated nitric acid, hydrofluoric acid and perchloric acid in sequence, dissolving and removing acid by stepwise heating, and finally extracting with nitric acid and diluting to volume; S3, the mass concentration of the solution is measured by a mass spectrometry method; the mass concentration of Re in the solution is measured by inductively coupled plasma mass spectrometry with Re as an online internal standard 238 U and 232 Th. S4, Result calculation; measured by mass spectrometry 238 U and 232 The net mass concentration of Th multiplied by the solution constant volume, divided by the original sample mass, multiplied by the mass-activity relationship coefficient of the radionuclide, gives the natural radionuclide activity concentration in the measured natural potash ore 238 U and 232 Th activity concentration.

2. A method of determining the content of uranium in a trona ore according to claim 1, wherein the trona ore is selected from the group consisting of trona, nahcolite, and mixtures thereof. 238 U and 232 A method of detecting the activity concentration of thorium, characterized in that, The step S1 specifically comprises: The grinding is performed by using a corundum jar-maifan ball vibration grinder, and the intermittent grinding mode is used, and the grinder is stopped for 1 min every 3 min; The drying temperature is 45 DEG C, and the time is 4 h; The sealing storage uses a plastic bottle, and the sealing is completed within 30 min after grinding.

3. A natural trona ore according to claim 1 or 2, wherein 238 U and 232 A method for detecting the activity concentration of Th, characterized in that The digestion operation in the step S2 specifically comprises: S21, weighing 0.2000 sample, and wetting with 2 ml high-purity water; S22, adding 1+1 hydrochloric acid dropwise until no bubbles are generated, and evaporating to dryness at low temperature; S23, adding 2 ml concentrated hydrochloric acid, 6 ml concentrated nitric acid, 5 ml hydrofluoric acid and 1 ml perchloric acid in sequence; S24, heating and dissolving at 140 DEG C for 2 h, and then increasing the temperature to 230 DEG C until the white smoke disappears; S25, extracting the residue with 5 ml 1+3 nitric acid, and diluting to 50 ml.

4. A method of determining the content of sodium carbonate in trona ore according to claim 1. 238 U and 232 A method for detecting the activity concentration of thorium, characterized in that, The mass spectrometric detection in the step S3 meets the following conditions: Tuning selection 238 U、 232 Th as the detected mass number; The online internal standard is a 10 ug / L Re solution, and the monitored mass number is 185; Before measurement, a calibration curve is established, and the sample blank is detected synchronously.

5. A method of determining the concentration of U and Th in a trona ore according to claim 4. 238 U and 232 A method of determining the activity concentration of U and Th, characterized in that, The isotopic abundance in the standard solution is set according to the following rules: 238 U abundance 0.992742 when not specified; 232 Th abundance taken as 1 if not indicated.

6. A method of determining the presence of a natural trona ore according to claim 1, wherein the ore is selected from the group consisting of trona, nahcolite, and mixtures thereof. 238 U and 232 A method of detecting the activity concentration of U and Th, characterized in that, The amount of hydrofluoric acid added in the step S2 is 5 ml, which is used to remove the silicon matrix in the form of SiF4.

7. A method of determining the presence of a natural trona ore according to claim 1, wherein the ore is characterized by: 238 U and 232 A method of detecting the activity concentration of Th, characterized in that, Overall spike recoveries were controlled between 97% and 103% by adding 0.50 μg 238 U and 1.00 μg 232 Th standard solution to verify the correctness.

8. A method of determining the content of a trona ore according to claim 1, wherein the trona ore is selected from the group consisting of: 238 U and 232 A method of detecting the activity concentration of Th, characterized in that, In the step S4, the unit of the net mass concentration is ng / ml, and the solution dilution volume is 50 ml.

9. A method of determining the content of a trona ore according to claim 8, wherein the trona ore is selected from the group consisting of: 238 U and 232 A method of detecting the activity concentration of Th, characterized in that, In step S4, the mass-activity relationship coefficient is: 1 ng 238 U converted to radioactivity 1.2437E-5 Bq, 1 ng 232 Th converted to radioactivity 4.0719E-6 Bq.

10. A method of determining the presence of a natural trona ore according to claim 1, wherein the natural trona ore is selected from the group consisting of: 238 U and 232 A method of detecting the activity concentration of Th, characterized in that, In the step S2, the reaction is carried out in a 100 ml polytetrafluoroethylene beaker with a cover, and the spattering is controlled by adding the acid in steps through the cover.

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