A test method for determining the ratio of oxygen to uranium in microgram quantities of uranium dioxide powder and pellets

Abstract

The application provides a test method for determining the oxygen-uranium ratio in trace uranium dioxide. The trace uranium dioxide sample is subjected to thermal gravimetric analysis to obtain a thermal gravimetric analysis curve. The specific process of the thermal gravimetric analysis comprises the following steps: a) under a protective atmosphere, the sample is subjected to first constant temperature treatment at a first temperature; b) under the protective atmosphere, the sample is heated to a second temperature at a first heating rate, and the sample is subjected to second constant temperature treatment at the second temperature; c) under an oxygen atmosphere, the sample is heated to a third temperature at a second heating rate, and the sample is subjected to third constant temperature treatment at the third temperature; finally, based on the thermal gravimetric analysis curve, the oxygen-uranium ratio in the trace uranium dioxide is calculated based on the minimum mass and the maximum mass of the sample. The application reduces the sample size and the crucible size, reduces the cost and is economic and environmentally friendly. The trace sample test reduces the radiation dose of the experimenter and the risk of internal irradiation caused by inhalation into the body.

Description

Technical Field

[0001] This invention belongs to the field of oxygen-uranium ratio analysis and detection technology of trace uranium dioxide, and relates to a test method for determining the oxygen-uranium ratio in trace uranium dioxide, particularly a test method for determining the oxygen-uranium ratio in trace uranium dioxide powder and pellets. Background Technology

[0002] Current technologies for determining the oxygen-uranium ratio of uranium dioxide powder and pellets typically use 1–2 g of uranium dioxide powder and 3–6 g of uranium dioxide pellets. This method involves large sample volumes, requiring large crucibles, resulting in low instrument accuracy, high testing costs, and poor environmental performance. Furthermore, uranium dioxide powder, being a radioactive material, generates alpha rays during testing, which can harm the human body; the larger the sample volume, the greater the radioactive contamination.

[0003] Therefore, finding a more suitable detection method for trace amounts of uranium dioxide that can solve the aforementioned technical problems in existing technologies has become one of the urgent problems to be solved by many front-line researchers and R&D companies in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide, particularly a method for determining the oxygen-uranium ratio in trace uranium dioxide powder and pellets. This invention can determine trace uranium dioxide samples, reducing sample volume and crucible size, lowering costs, and is both economical and environmentally friendly. Trace sample testing reduces the radiation dose to laboratory personnel and the risk of internal radiation exposure from inhalation.

[0005] This invention provides a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide, comprising the following steps:

[0006] 1) Perform thermogravimetric analysis on trace amounts of uranium dioxide samples to obtain thermogravimetric analysis curves;

[0007] The specific procedure for thermogravimetric analysis includes the following steps:

[0008] a) Under a protective atmosphere, the sample is subjected to a first isothermal treatment at a first temperature;

[0009] b) Under a protective atmosphere, the sample is heated to a second temperature at a first heating rate, and then subjected to a second isothermal treatment at the second temperature.

[0010] c) Under an oxygen atmosphere, the sample is heated to a third temperature at a second heating rate, and then subjected to a third isothermal treatment at the third temperature.

[0011] 2) Based on the thermogravimetric analysis curves obtained in the above steps, the oxygen-uranium ratio in trace amounts of uranium dioxide is calculated using the minimum and maximum masses of the sample.

[0012] Preferably, the mass of the trace uranium dioxide sample is 30–100 mg;

[0013] The instrument used for thermogravimetric analysis includes a TGA8000 thermogravimetric analyzer.

[0014] Preferably, the uranium dioxide sample comprises uranium dioxide powder and / or uranium dioxide pellets;

[0015] The protective atmosphere includes nitrogen and / or an inert gas.

[0016] Preferably, the first temperature is 25–35°C;

[0017] The duration of the first isothermal treatment is 5 to 30 minutes.

[0018] Preferably, the first heating rate is 5–15 °C / min;

[0019] The second temperature is 120–180°C.

[0020] Preferably, the second isothermal treatment takes 5 to 30 minutes;

[0021] The second heating rate is 5–15 °C / min.

[0022] Preferably, the third temperature is 500–900°C;

[0023] The duration of the third isothermal treatment is 60–180 min.

[0024] Preferably, the minimum mass is a uranium dioxide sample that has lost surface water to constant weight after dehydration;

[0025] The highest quality is a fully oxidized uranium dioxide sample.

[0026] Preferably, the trace amount of uranium dioxide sample reaches a fully oxidized state at 500–800°C.

[0027] Preferably, during the process of heating to the third temperature at the second heating rate, the thermogravimetric curve shows a trend of slow decrease and continuous slight increase in mass after reaching the highest mass value.

[0028] The highest quality value is the highest quality in step 2).

[0029] This invention provides a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide, comprising the following steps: First, a trace amount of uranium dioxide sample is subjected to thermogravimetric analysis (TGA) to obtain a TGA curve. The specific TGA process includes the following steps: a) Under a protective atmosphere, the sample is subjected to a first isothermal treatment at a first temperature; b) Under a protective atmosphere, the temperature is increased to a second temperature at a first heating rate, and the sample is subjected to a second isothermal treatment at the second temperature; c) Under an oxygen atmosphere, the temperature is increased to a third temperature at a second heating rate, and the sample is subjected to a third isothermal treatment at the third temperature. Finally, based on the TGA curve obtained from the above steps, the oxygen-uranium ratio in the trace amount of uranium dioxide is calculated using the minimum and maximum masses of the sample. Compared with the prior art, this invention creatively designs a method for determining the oxygen-uranium atomic ratio of trace uranium dioxide powder and pellets. Using a high-precision thermogravimetric analyzer, samples of approximately 30–100 mg of uranium dioxide powder and pellets are tested to obtain the corresponding thermogravimetric curves, and the oxygen-uranium ratio is calculated.

[0030] Unlike existing methods that require testing large quantities of samples, this invention uses a method with extremely small sample sizes to obtain stable and reliable oxygen-to-uranium ratio values ​​for uranium dioxide powder and pellets. This invention reduces sample size and crucible dimensions, lowering costs and being both economical and environmentally friendly. Micro-sample testing reduces the radiation dose to laboratory personnel and the risk of internal radiation exposure from inhalation. Compared to conventional methods where uranium dioxide samples require 2 hours at 800°C to achieve complete oxidation, this invention, due to its very small sample size (approximately 50 mg), achieves complete oxidation at 500°C under a pure oxygen flow. This significantly shortens the testing time and improves efficiency. The detection method provided by this invention is simple, environmentally friendly, highly controllable, and reproducible, making it more suitable for large-scale promotion and application. Attached Figure Description

[0031] Figure 1 Thermogravimetric curve of uranium dioxide powder tested by the testing method provided by the present invention. Detailed Implementation

[0032] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0034] The purity of all raw materials used in this invention is not particularly limited. Preferred purity is analytical grade or that commonly used in the field of uranium dioxide oxygen-uranium ratio detection.

[0035] This invention provides a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide, comprising the following steps:

[0036] 1) Perform thermogravimetric analysis on trace amounts of uranium dioxide samples to obtain thermogravimetric analysis curves;

[0037] The specific procedure for thermogravimetric analysis includes the following steps:

[0038] a) Under a protective atmosphere, the sample is subjected to a first isothermal treatment at a first temperature;

[0039] b) Under a protective atmosphere, the sample is heated to a second temperature at a first heating rate, and then subjected to a second isothermal treatment at the second temperature.

[0040] c) Under an oxygen atmosphere, the sample is heated to a third temperature at a second heating rate, and then subjected to a third isothermal treatment at the third temperature.

[0041] 2) Based on the thermogravimetric analysis curves obtained in the above steps, the oxygen-uranium ratio in trace amounts of uranium dioxide is calculated using the minimum and maximum masses of the sample.

[0042] The present invention first performs thermogravimetric analysis on a trace amount of uranium dioxide sample to obtain a thermogravimetric analysis curve.

[0043] In this invention, the mass of the trace uranium dioxide sample is preferably 30-100 mg, more preferably 45-85 mg, and even more preferably 60-70 mg.

[0044] In this invention, the instrument used for thermogravimetric analysis preferably includes a TGA8000 thermogravimetric analyzer.

[0045] In this invention, the specific process of thermogravimetric analysis includes the following steps:

[0046] a) Under a protective atmosphere, the sample is subjected to a first isothermal treatment at a first temperature;

[0047] b) Under a protective atmosphere, the sample is heated to a second temperature at a first heating rate, and then subjected to a second isothermal treatment at the second temperature.

[0048] c) Under an oxygen atmosphere, the sample is heated to a third temperature at a second heating rate, and then subjected to a third isothermal treatment at the third temperature.

[0049] The present invention first subjectes the sample to a first isothermal treatment under a protective atmosphere and at a first temperature.

[0050] In this invention, the uranium dioxide sample preferably comprises uranium dioxide powder and / or uranium dioxide pellets, more preferably uranium dioxide powder or uranium dioxide pellets.

[0051] In this invention, the protective atmosphere preferably includes nitrogen and / or an inert gas, more preferably nitrogen or an inert gas.

[0052] In this invention, the first temperature is preferably 25-35°C, more preferably 27-33°C, even more preferably 29-31°C, and specifically 30°C.

[0053] In this invention, the time for the first isothermal treatment is preferably 5 to 30 minutes, more preferably 10 to 20 minutes, more preferably 10 to 19 minutes, and specifically 10 minutes.

[0054] The present invention further heats the sample to a second temperature at a first heating rate under a protective atmosphere, and then performs a second isothermal treatment on the sample at the second temperature.

[0055] In this invention, the first heating rate is preferably 5 to 15 °C / min, more preferably 7 to 13 °C / min, even more preferably 9 to 11 °C / min, and specifically 10 °C / min.

[0056] In this invention, the second temperature is preferably 120-180°C, more preferably 130-170°C, even more preferably 140-160°C, and specifically 150°C.

[0057] In this invention, the second isothermal treatment time is preferably 5 to 30 minutes, more preferably 10 to 25 minutes, even more preferably 10 to 20 minutes, and specifically 10 minutes.

[0058] The present invention then heats the sample to a third temperature at a second heating rate under an oxygen atmosphere, and then performs a third isothermal treatment on the sample at the third temperature.

[0059] In this invention, the second heating rate is preferably 5 to 15 °C / min, more preferably 7 to 13 °C / min, even more preferably 9 to 11 °C / min, and specifically 10 °C / min.

[0060] In this invention, the third temperature is preferably 500-900°C, more preferably 600-800°C, even more preferably 700-800°C, and specifically 800°C.

[0061] In this invention, the time for the third isothermal treatment is preferably 60-180 min, more preferably 80-160 min, even more preferably 100-140 min, and specifically 120 min.

[0062] Finally, based on the thermogravimetric analysis curves obtained from the above steps, the present invention calculates the oxygen-uranium ratio in trace amounts of uranium dioxide using the minimum and maximum masses of the sample.

[0063] In this invention, the minimum mass is preferably a uranium dioxide sample that has lost surface water to a constant weight after water loss.

[0064] In this invention, the highest quality is preferably a fully oxidized uranium dioxide sample.

[0065] In this invention, the trace amount of uranium dioxide sample is preferably fully oxidized at 500–800°C, more preferably at 500–700°C, even more preferably at 500–600°C, and specifically at 500°C.

[0066] In this invention, during the process of heating to the third temperature at the second heating rate, it is preferable that the thermogravimetric curve shows a trend of slow decrease in mass followed by a continuous slight increase after reaching the highest mass value.

[0067] In this invention, the highest mass value is preferably the highest mass in step 2).

[0068] This invention aims to complete and refine the overall technical solution, better ensure the accuracy and stability of the testing method, and further improve the effectiveness of testing for trace amounts of uranium dioxide. Specifically, the testing method for determining the oxygen-uranium ratio in trace uranium dioxide powder and pellets may include the following:

[0069] 1) Within the testable range of the high-precision equipment, weigh samples of different weights (30-100mg) for testing, and determine the optimal weighing weight of the sample based on the obtained thermogravimetric curve.

[0070] 2) Select different heating programs (including initial temperature, heating rate, holding time, etc.) for testing to determine the temperature and time points at which the sample loses surface water and completes oxidation, so as to determine the optimal heating program.

[0071] 3) Then, different atmospheres (protective atmosphere and pure oxygen flow) are selected for testing to determine the optimal oxidation atmosphere and finally determine the best testing method.

[0072] The present invention provides a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide powder and pellets. The method designed in this invention for determining the oxygen-uranium atomic ratio in trace amounts of uranium dioxide powder and pellets uses a high-precision thermogravimetric analyzer to test samples of approximately 30–100 mg of uranium dioxide powder and pellets, obtaining corresponding thermogravimetric curves and calculating the oxygen-uranium ratio.

[0073] Unlike existing methods that require testing large quantities of samples, this invention uses a method with extremely small sample sizes to obtain stable and reliable oxygen-to-uranium ratio values ​​for uranium dioxide powder and pellets. This invention reduces sample size and crucible dimensions, lowering costs and being both economical and environmentally friendly. Micro-sample testing reduces the radiation dose to laboratory personnel and the risk of internal radiation exposure from inhalation. Compared to conventional methods where uranium dioxide samples require 2 hours at 800°C to achieve complete oxidation, this invention, due to its very small sample size (approximately 50 mg), achieves complete oxidation at 500°C under a pure oxygen flow. This significantly shortens the testing time and improves efficiency. The detection method provided by this invention is simple, environmentally friendly, highly controllable, and reproducible, making it more suitable for large-scale promotion and application.

[0074] To further illustrate the present invention, the following describes in detail a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide provided by the present invention, in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0075] Test equipment: PE TGA8000 thermogravimetric analyzer

[0076] Example 1

[0077] A sample of 54.588 mg of uranium dioxide powder was weighed and tested under different atmospheres. Figure 1 The temperature is increased using the heating program, and the thermogravimetric curve is detected.

[0078] a) Under nitrogen atmosphere, the sample was subjected to a first isothermal treatment at 30°C for 10 min;

[0079] b) Under nitrogen atmosphere, the temperature is increased to 150°C at a heating rate of 10°C / min, and the sample is subjected to a second isothermal treatment at this temperature for 10 min.

[0080] c) Under an oxygen atmosphere, continue heating to 800°C at a heating rate of 10°C / min, and at this temperature, perform a third isothermal treatment on the sample for 120 min.

[0081] See Figure 1 , Figure 1 Thermogravimetric curve of uranium dioxide powder tested by the testing method provided by the present invention.

[0082] Figure 1 Thermogravimetric curves of a uranium dioxide powder sample with a mass of 54.588 mg under different atmospheres, using the heating programs shown in Figures 1) to 5).

[0083] from Figure 1 The initial mass of the sample was 54.588 mg. Under a nitrogen atmosphere, the surface water was lost, resulting in uranium dioxide powder (m1) of constant weight after dehydration, which was 54.524 mg. Oxidation was then carried out under an oxygen atmosphere, reaching complete oxidation at approximately 500 degrees Celsius, resulting in the highest mass (m2) of 56.439 mg. With increasing temperature and time, the mass of the crucible slowly increases; therefore, after reaching the highest mass, the thermogravimetric curve shows a trend of slow decrease followed by a continuous slight increase in mass.

[0084] The oxygen-uranium atomic ratio of uranium dioxide powder and pellets is calculated based on the values ​​of m1 and m2. The technical process is as follows:

[0085] The oxygen-uranium ratio is calculated using the following formula (1):

[0086]

[0087] in:

[0088] W1—Net weight of uranium dioxide sample, g;

[0089] W2—Weight of the uranium dioxide sample after oxidation to uranium octoxide, in g;

[0090] I1—The total weight of all impurity element oxides in one gram of uranium dioxide, in grams;

[0091] I2 — the total weight of all impurity element oxides in one gram of uranium dioxide, in grams;

[0092] mA1—Molecular weight of uranium octoxide / 3 times the atomic weight of oxygen;

[0093] mA2 — Molecular weight of uranium dioxide / atomic weight of oxygen.

[0094] Where W1 corresponds to the weight of the sample after losing surface water in the thermogravimetric curve, and W2 corresponds to the weight of the sample after heat preservation. The atomic weight of uranium is calculated according to formula (2) based on the sum of the products of the isotope enrichment of each uranium in the sample and its mass number:

[0095] m U =234.0409×( 234U%)+235.0439×( 235 U%)+236.0457×( 236 U%)+238.0508×( 238 U%)(2)

[0096] Because uranium dioxide powder and pellets inherently contain some impurity elements, these impurities will oxidize and increase in weight after oxidation in an oxidizing atmosphere. The impurity elements in uranium dioxide mainly include metallic impurities and gaseous impurities (C, H, O, N). During oxidation, gaseous impurities are converted into gases and released, while metallic impurities are transformed from a reduced state into metal oxides.

[0097] To avoid the influence of changes in the weight of impurity elements, the specific values ​​of I1 and I2 can be calculated based on the oxide form and conversion factor of the impurity elements. However, the total impurity content in nuclear-grade uranium dioxide powder samples is usually less than 1500 ug / g, and the values ​​of I1 and I2 generally do not have a significant impact on the oxygen-uranium atomic ratio of the sample. Therefore, when calculating the oxygen-uranium atomic ratio of uranium dioxide powder and pellets, changes in the content of impurity elements are usually ignored.

[0098] The present invention provides a detailed description of a method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide powder and pellets. Specific examples have been used to illustrate the principles and implementation methods of the invention. These embodiments are merely illustrative to aid in understanding the method and core ideas of the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for determining the oxygen-uranium ratio in trace amounts of uranium dioxide, characterized in that, Includes the following steps: 1) Perform thermogravimetric analysis on trace amounts of uranium dioxide samples to obtain thermogravimetric analysis curves; The specific procedure for thermogravimetric analysis includes the following steps: a) Under a protective atmosphere, the sample is subjected to a first isothermal treatment at a first temperature; b) Under a protective atmosphere, the sample is heated to a second temperature at a first heating rate, and then subjected to a second isothermal treatment at the second temperature. c) Under an oxygen atmosphere, the sample is heated to a third temperature at a second heating rate, and then subjected to a third isothermal treatment at the third temperature. 2) Based on the thermogravimetric analysis curves obtained in the above steps, the oxygen-uranium ratio in trace amounts of uranium dioxide is calculated using the minimum and maximum masses of the sample.

2. The testing method according to claim 1, characterized in that, The mass of the trace uranium dioxide sample is 30–100 mg; The instrument used for thermogravimetric analysis includes a TGA8000 thermogravimetric analyzer.

3. The testing method according to claim 1, characterized in that, The uranium dioxide sample includes uranium dioxide powder and / or uranium dioxide pellets; The protective atmosphere includes nitrogen and / or an inert gas.

4. The testing method according to claim 1, characterized in that, The first temperature is 25–35°C; The duration of the first isothermal treatment is 5 to 30 minutes.

5. The testing method according to claim 1, characterized in that, The first heating rate is 5–15 °C / min; The second temperature is 120–180°C.

6. The testing method according to claim 1, characterized in that, The second isothermal treatment lasts for 5 to 30 minutes. The second heating rate is 5–15 °C / min.

7. The testing method according to claim 1, characterized in that, The third temperature is 500–900°C; The duration of the third isothermal treatment is 60–180 min.

8. The testing method according to claim 1, characterized in that, The minimum mass is a uranium dioxide sample that has lost surface water to constant weight after dehydration; The highest quality is a fully oxidized uranium dioxide sample.

9. The testing method according to claim 1, characterized in that, The trace amount of uranium dioxide sample reached a fully oxidized state at 500–800°C.

10. The testing method according to claim 1, characterized in that, During the process of heating to the third temperature at the second heating rate, the thermogravimetric curve shows a trend of slow decrease and continuous slight increase in mass after reaching the highest mass value. The highest quality value is the highest quality in step 2).

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