Method for determining specific activity of plutonium solution and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TSINGHUA UNIVERSITY
- Filing Date
- 2026-03-20
- Publication Date
- 2026-04-24
Smart Images
Figure CN121917481A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nuclear material analysis technology, specifically to a method and application for determining the specific activity of plutonium (Pu) solution. Background Technology
[0002] Plutonium, as an important nuclear material, is widely found in spent nuclear reactor fuel, nuclear fuel reprocessing products, and nuclear facility-related waste. It typically exists in a mixture of multiple isotopes (such as...). 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 Specific activity (the radioactivity per unit mass of a substance) is a core parameter characterizing the radioactivity of plutonium solutions. Accurate determination of the composition of various isotopes (such as Plutonium, etc.) is crucial for accurate measurement. 238 Pu、 239 Pu、 240 The specific activity of mixed plutonium solutions (Pu) is of great significance for the safe management of nuclear materials, the compliant disposal of nuclear waste, and the assessment of radiation risks.
[0003] Existing methods for determining the specific activity of mixed plutonium solutions mainly include mass spectrometry, alpha spectrometry, and activity balance methods.
[0004] Mass spectrometry (such as thermal ionization mass spectrometry and inductively coupled plasma mass spectrometry) can calculate the total specific activity by determining the abundance of each isotope and combining it with the known specific activity of a single isotope. This method essentially uses compositional analysis and weighted summation for detection and calculation, and its accuracy is highly dependent on the precise determination of the isotopic abundance in the sample. However, for samples of unknown origin or with missing historical data (such as nuclear facility decommissioning waste and nuclear accident emergency samples), whose isotopic composition is completely unknown, mass spectrometry must rely on complex chemical separation and purification and expensive instruments to obtain abundance data, and the operation cycle is long, making it difficult to meet the needs of rapid on-site analysis.
[0005] Alpha spectroscopy can distinguish isotopic contributions by measuring the characteristic alpha-ray spectra of different isotopes. However, its operation is relatively cumbersome, limited by the low efficiency of alpha-ray detection, and requires precise identification and counting correction of spectral peak positions. This is especially problematic when multiple isotopes are present in the sample or when interference from other actinide nuclides is present (e.g., 2³). 9 Pu and² 40 The alpha particle energies of Pu are extremely close, and the spectral peaks overlap significantly, making spectral analysis extremely difficult and resulting in an inability to accurately distinguish the activity contributions of each isotope.
[0006] The activity balance method relies on historical data from the nuclear fuel production or processing process (such as reactor burnup, cooling time, etc.). Therefore, for decommissioned waste or samples of unknown origin, complete historical traceability information is usually difficult to obtain, rendering this method unsuitable.
[0007] Therefore, how to accurately and quickly determine the specific activity of mixed plutonium solutions without needing to analyze the isotopic composition is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0008] This invention aims to at least partially address one of the technical problems in related technologies. To this end, this invention provides a method and application for determining the specific activity of plutonium solutions. By combining liquid scintillation counting with ultraviolet-visible spectrophotometry, a combination of "activity response" and "concentration response" is achieved. This allows for the establishment of multi-dimensional calibration relationships using standard plutonium solutions with known specific activities, enabling accurate and rapid determination of the specific activity of mixed plutonium solutions with unknown isotopic compositions. This invention is simple to operate, fast and efficient, and has high measurement accuracy. Furthermore, it does not require obtaining the isotopic composition of the plutonium solution to be tested, nor does it require complex sample pretreatment, thus overcoming the shortcomings of related technologies in terms of adaptability to multi-isotopic systems, efficiency in field application, and cost control.
[0009] To achieve the above objectives, the present invention provides the following technical solution: A first aspect of the present invention provides a method for determining the specific activity of a plutonium solution, comprising: A plutonium solution with a known specific activity of A1 was used as a standard solution, and the liquid scintillation count rate of the standard solution was determined and denoted as C1. The second-order guide spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order guide spectrum of the standard solution was determined and denoted as S1. The liquid scintillation count rate of the test solution is determined and denoted as C2; The second-order guide spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution was determined and denoted as S2. The specific activity A2 of the test solution is calculated using the following formula:
[0010] Wherein, A2 represents the specific activity of the test solution in Bq / g; S1 represents the peak area (nm) of the characteristic absorption peak of tetravalent plutonium in the second-order guided spectrum of the standard solution; S2 represents the peak area (nm) of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution; V1 represents the volume / mL of the standard solution used to test the liquid flash count rate; V2 represents the volume / mL of the solution to be tested when the liquid flash count rate is measured; C1 represents the liquid scintillation count rate of the standard solution in cpm; C2 represents the liquid scintillation count rate of the test solution in cpm; A1 represents the specific activity of the standard solution in Bq / g.
[0011] By adopting the above technical solution, a multi-dimensional calibration relationship can be established using standard samples with known specific activities. This combines the "activity response" of liquid scintillation counting with the "concentration response" of ultraviolet-visible spectrophotometry, enabling precise and rapid determination of the specific activity of a test solution with an unknown isotopic composition. This invention eliminates the need for isotopic composition measurement of unknown samples, transforming the complex and difficult step of "determining isotopic abundance" into the simple step of "determining spectral peak area." This avoids the shortcomings of traditional mass spectrometry, which requires analyzing the isotopic composition of the test solution itself, resulting in high equipment dependence, complex operation, and long processing times. It also overcomes the deficiencies of traditional methods in terms of adaptability to multi-isotopic systems, efficiency in field applications, and cost control.
[0012] According to an embodiment of the present invention, the above-described measurement method may further include at least one of the following additional technical features: According to an embodiment of the present invention, the standard solution comprises 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 One or more of Pu.
[0013] Preferably, the standard solution is a single isotope plutonium solution, the single isotope plutonium solution comprising... 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 Any of the following in Pu, preferred 242 Pu.
[0014] According to an embodiment of the present invention, the method for obtaining the specific activity A1 of the standard solution includes at least one of mass spectrometry, alpha spectroscopy, activity balance method, and theoretical calculation method.
[0015] In some embodiments, the theoretical calculation method includes calculating the specific activity A1 of the standard solution using the following formula:
[0016] in: A1 represents the specific activity of the standard solution in Bq / g; λ represents the decay constant, λ = ln2 / T 1 / 2 ; N A This represents Avogadro's constant, approximately 6.02214076 × 10⁻⁶. 23 mol -1 .
[0017] M represents the molar mass of the isotope in the standard solution (g / mol).
[0018] According to an embodiment of the present invention, the standard solution is a plutonium solution with a known isotopic composition.
[0019] In some embodiments, the specific activity A1 of the standard solution is calculated by weighted summation using the following formula:
[0020] Wherein, A1 represents the specific activity of the standard solution in Bq / g; A i The specific activity of each isotope in the standard solution is expressed as Bq / g. R i This indicates the mass percentage of each isotope in the standard solution.
[0021] According to an embodiment of the present invention, both the standard solution and the test solution are plutonium perchloric acid (HClO4) solutions.
[0022] According to an embodiment of the present invention, the concentration of perchloric acid in the standard solution and the test solution is ≥1 mol / L.
[0023] According to an embodiment of the present invention, the standard solution has the same concentration of perchloric acid as the test solution.
[0024] According to an embodiment of the present invention, the test solution comprises 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 One or more of Pu.
[0025] Preferably, the test solution is a mixed plutonium solution with unknown isotopic composition.
[0026] According to an embodiment of the present invention, the peak position of the characteristic absorption peak is 460~480 nm.
[0027] According to an embodiment of the present invention, the determination method satisfies at least one of the following conditions: The liquid scintillation count rate is measured within the effective linear measurement range of the liquid scintillation counter; The ultraviolet-visible absorption spectrum was measured within a range where absorbance and concentration were linearly related.
[0028] Preferably, the liquid scintillation count rate is controlled to be 10 to 102. 5 cpm.
[0029] Preferably, the absorbance value is controlled to be between 0.01 and 1.0.
[0030] According to an embodiment of the present invention, the ultraviolet-visible spectrophotometry satisfies at least one of the following conditions: The wavelength range is 200~1400 nm; The spectral wavelength interval is 0.1~1.0 nm; The scan rate is 60~600 nm / min.
[0031] A second aspect of the present invention provides an application of the aforementioned measurement method in nuclear fuel cycle, nuclear facility decommissioning, or nuclear safety regulation.
[0032] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0033] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The test results are those of the standard solution described in Example 1 of this invention, wherein... Figure 1 In the image, (a) is the UV-Vis absorption spectrum of the standard solution. Figure 1 (b) in the figure is the absorbance-liquid scintillation count rate relationship curve of the standard solution. Figure 1 (c) in the figure represents the second-order guide spectrum of the standard solution. Figure 1 In the figure, (d) is the curve showing the relationship between the second-order conduction absorption peak area and the liquid scintillation count rate of the standard solution. Figure 2 The test results are those of the test solution described in Example 1 of this invention, wherein... Figure 2 In the image, (a) is the UV-Vis absorption spectrum of the solution to be tested. Figure 2 (b) in the figure is the absorbance-liquid scintillation count rate relationship curve of the test solution. Figure 2 (c) in the figure represents the second-order guide spectrum of the test solution. Figure 2 In the figure, (d) is the curve showing the relationship between the second-order conduction absorption peak area and the liquid scintillation count rate of the solution to be tested. Detailed Implementation
[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0035] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0036] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0037] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.
[0038] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.
[0039] To address the technical challenge of accurately and quickly determining the specific activity of mixed plutonium solutions without needing to analyze isotopic composition, the inventors discovered that liquid scintillation counting (LSC) technology has advantages such as high detection efficiency and the ability to directly measure liquid samples, enabling rapid acquisition of the total radioactivity count of the solution. However, its output data is only the count rate (CPM) and cannot be directly converted into specific activity. Ultraviolet-visible spectrophotometry can effectively eliminate background interference and accurately identify the absorption signal of plutonium ions at characteristic wavelengths, and the intensity of this signal has a good linear relationship with the total molar concentration of plutonium. However, it cannot distinguish the activity contribution of different isotopes.
[0040] Although neither method alone can yield the specific activity of mixed plutonium solutions, the inventors discovered that the characteristic peak area of tetravalent plutonium in the second-order UV-Vis absorption spectrum is linearly correlated with the total molar concentration of plutonium, unaffected by the type of plutonium isotope. By combining the "activity response" of liquid scintillation counting with the "concentration response" of UV-Vis spectrophotometry, a multi-dimensional calibration relationship can be established using standard plutonium solutions with known specific activities, enabling precise and rapid determination of the specific activity of mixed plutonium solutions with unknown isotopic compositions. This invention expands the applicability and accuracy of determining the specific activity of mixed plutonium solutions with unknown isotopic compositions, solving the challenge of determining the specific activity of Pu-containing isotope mixed solutions.
[0041] A first aspect of the present invention provides a method for determining the specific activity of a plutonium solution, comprising: A plutonium solution with a known specific activity of A1 was used as a standard solution, and the liquid scintillation count rate of the standard solution was determined and denoted as C1. The second-order guide spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order guide spectrum of the standard solution was determined and denoted as S1. The liquid scintillation count rate of the test solution is determined and denoted as C2; The second-order guide spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution was determined and denoted as S2. The specific activity A2 of the test solution is calculated using the following formula:
[0042] Wherein, A2 represents the specific activity of the test solution in Bq / g; S1 represents the peak area (nm) of the characteristic absorption peak of tetravalent plutonium in the second-order guided spectrum of the standard solution; S2 represents the peak area (nm) of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution; V1 represents the volume / mL of the standard solution used to test the liquid flash count rate; V2 represents the volume / mL of the solution to be tested when the liquid flash count rate is measured; C1 represents the liquid scintillation count rate of the standard solution in cpm; C2 represents the liquid scintillation count rate of the test solution in cpm; A1 represents the specific activity of the standard solution in Bq / g.
[0043] By adopting the above technical solution, a multi-dimensional calibration relationship can be established using standard samples with known specific activities. This combines the "activity response" of liquid scintillation counting with the "concentration response" of ultraviolet-visible spectrophotometry, enabling precise and rapid determination of the specific activity of a test solution with an unknown isotopic composition. This invention eliminates the need for isotopic composition measurement of unknown samples, transforming the complex and difficult step of "determining isotopic abundance" into the simple step of "determining spectral peak area." This avoids the shortcomings of traditional mass spectrometry, which requires analyzing the isotopic composition of the test solution itself, resulting in high equipment dependence, complex operation, and long processing times. It also overcomes the deficiencies of traditional methods in terms of adaptability to multi-isotopic systems, efficiency in field applications, and cost control.
[0044] According to an embodiment of the present invention, the above-described measurement method may further include at least one of the following additional technical features: According to an embodiment of the present invention, the standard solution comprises 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 One or more of Pu.
[0045] Preferably, the standard solution is a single isotope plutonium solution, the single isotope plutonium solution comprising... 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 Any of the following in Pu, preferred 242 Pu.
[0046] Therefore, a spectral quantitative model can be established using a single isotope solution, eliminating the need to purchase mixed plutonium standard materials with a highly matched isotopic composition to the sample. This significantly reduces reliance on complex, expensive, and difficult-to-obtain mixed isotope standard materials, lowers the difficulty of obtaining standard materials, and improves the universality of the measurement method. It fundamentally avoids the risk of fluctuations in molar absorptivity due to differences in isotope mass, ensuring the accuracy of concentration quantification. Compared to traditional methods that require the preparation of multiple mixed isotope standard points for curve fitting, this invention only requires a single isotope standard solution to complete the calibration of the concentration response factor. This not only significantly reduces the workload of standard solution preparation and the amount of radioactive waste generated, but also simplifies and speeds up the analytical process, which is beneficial for meeting the needs of rapid analysis at nuclear fuel cycles and nuclear facility decommissioning sites. A single isotope standard solution has a definite theoretical value of specific activity (such as through precise calculation by half-life). Using it as a source reference can not only accurately calibrate the detection efficiency of the liquid scintillation counter, but also simultaneously calibrate the concentration response coefficient of the ultraviolet spectrum. This achieves a precise correlation between the two independent metrological systems of "radioactivity" and "molar concentration", ensuring the traceability of the final measurement results.
[0047] According to an embodiment of the present invention, the method for obtaining the specific activity A1 of the standard solution includes at least one of mass spectrometry, alpha spectroscopy, activity balance method, and theoretical calculation method.
[0048] In some embodiments, the theoretical calculation method includes calculating the specific activity A1 of the standard solution using the following formula:
[0049] in: A1 represents the specific activity of the standard solution in Bq / g; λ represents the decay constant, λ = ln2 / T 1 / 2 ; N A This represents Avogadro's constant, approximately 6.02214076 × 10⁻⁶. 23 mol -1 .
[0050] M represents the molar mass of the isotope in the standard solution (g / mol).
[0051] Therefore, the specific activity of a standard solution of a single isotope can be obtained directly through theoretical calculation, avoiding the limitations of measuring instruments, simplifying the measurement steps, and simultaneously calibrating the detection efficiency of the liquid scintillation counter and the concentration response coefficient of the ultraviolet spectrum.
[0052] According to an embodiment of the present invention, the standard solution is a plutonium solution with a known isotopic composition.
[0053] In some embodiments, the specific activity A1 of the standard solution is calculated by weighted summation using the following formula:
[0054] Wherein, A1 represents the specific activity of the standard solution in Bq / g; A i The specific activity of each isotope in the standard solution is expressed as Bq / g. R i This indicates the mass percentage of each isotope in the standard solution.
[0055] According to an embodiment of the present invention, both the standard solution and the test solution are plutonium perchloric acid (HClO4) solutions.
[0056] By adopting the above technical solution, the perchloric acid system can forcibly convert plutonium ions in mixed valence states in the solution into a single Pu(IV) form, which is beneficial for selectively locking the target valence state. This avoids the defects of trivalent plutonium (Pu(III)), tetravalent plutonium (Pu(IV)) and hexavalent plutonium (Pu(VI)) coexisting in the conventional nitric acid system, with overlapping characteristic peaks that change over time. This fundamentally eliminates the spectral drift and quantitative errors caused by the plutonium's own disproportionation reaction. At the same time, perchlorate ions have no characteristic absorption in the visible light region, avoiding background interference from medium anions on the 470 nm characteristic absorption peak, which is beneficial for improving the spectral signal-to-noise ratio and repeatability. It can also enhance the long-term stability of the solution, ensuring that the valence state and concentration of the standard solution do not change during storage and use, providing high-confidence benchmark data for subsequent specific activity calculations.
[0057] According to an embodiment of the present invention, the concentration of perchloric acid in the standard solution and the test solution is ≥1 mol / L, specifically such as 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc.
[0058] This allows the ionic strength of perchlorate to reach a stable plateau region, ensuring that the molar absorptivity of Pu(IV) at its characteristic absorption peak no longer changes with acidity fluctuations, thus eliminating systematic errors introduced by slight differences in acidity between the standard solution and the test solution. This concentration condition also ensures that the solution has sufficient buffer capacity, maintaining a stable chemical environment even if the test sample introduces a small amount of dilution water or impurities, guaranteeing the repeatability and accuracy of spectral measurements.
[0059] According to an embodiment of the present invention, the standard solution and the test solution have the same concentration of perchloric acid. This facilitates the forced conversion of mixed-valence plutonium ions into a single Pu(IV) form, eliminating spectral drift and quantitative errors caused by plutonium's own disproportionation reaction, while simultaneously eliminating matrix interference from perchloric acid, further improving the accuracy of the determination.
[0060] According to an embodiment of the present invention, the test solution comprises 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 One or more of Pu.
[0061] Preferably, the test solution is a mixed plutonium solution with unknown isotopic composition.
[0062] Therefore, this invention is widely applicable to all common plutonium isotopes and any mixtures thereof, without requiring adjustments to the measurement process or calibration model due to differences in isotopic composition, significantly improving its universality for plutonium samples from different sources and under different burnup conditions. Based on the specific response of the spectrum to total molar concentration, this invention avoids interference from isotopic composition variations on quantitative results, ensuring that the specific activity measurement accurately reflects the sample's radioactivity level. This solves the technical challenge of quantitatively determining samples with unknown isotopic compositions in nuclear fuel cycles and nuclear facility decommissioning scenarios.
[0063] According to an embodiment of the present invention, the method for obtaining the second-order derivative spectrum includes: measuring the absorption spectrum of the solution using ultraviolet-visible absorption spectroscopy, and performing a second derivative on the absorbance of the absorption spectrum.
[0064] According to an embodiment of the present invention, the formula for the second derivative is:
[0065] in, The absorbance of the second-order guided spectrum; A represents the absorbance of the absorption spectrum; λ′ is the wavelength / nm of the absorption spectrum.
[0066] In some embodiments, the software used for second derivative processing is Origin software.
[0067] According to an embodiment of the present invention, the peak position of the characteristic absorption peak is 460~480 nm, specifically such as 460 nm, 460 nm, 465 nm, 470 nm, 475 nm, 480 nm, etc.
[0068] This allows us to avoid the characteristic absorption bands of anions in the medium, while also staying away from interference from trace fission products and container leaching impurities in the solution, significantly reducing the impact of complex matrix background on quantitative analysis. This wavelength corresponds to the specific electronic transition absorption peak of Pu(IV). At this wavelength, the molar absorptivity of other plutonium ions such as Pu(III) and Pu(VI) is extremely low, enabling selective identification of the target valence state and eliminating quantitative errors caused by changes in plutonium's own valence state. At this characteristic wavelength, the absorbance of Pu(IV) strictly follows the Lambert-Beer law with its total molar concentration over a wide concentration range. The second-derivative peak area has a high linear correlation coefficient with concentration, and after the second-derivative transformation, the peak position exhibits a sharp and symmetrical peak shape, facilitating automated peak finding and integrated area calculation, thus improving peak area integration accuracy and measurement repeatability.
[0069] According to an embodiment of the present invention, the determination method satisfies at least one of the following conditions: The liquid scintillation count rate is measured within the effective linear measurement range of the liquid scintillation counter; The ultraviolet-visible absorption spectrum was measured within a range where absorbance and concentration were linearly related.
[0070] Therefore, the measurement of the liquid scintillation count rate is performed within the effective linear measurement range of the liquid scintillation counter, which can avoid the failure of detector dead time correction due to excessively high count rate or the introduction of statistical fluctuation error due to excessively low count rate, thus ensuring the accuracy of activity measurement; the measurement of the ultraviolet-visible absorption spectrum is performed within the range where absorbance and concentration are linearly related, which can avoid the concentration quantitative deviation caused by deviation from Lambert-Beer's law, thus ensuring the linear correlation between spectral response and molar concentration.
[0071] Preferably, the liquid scintillation count rate is controlled to be 10 to 102. 5 cpm, specifically 10 cpm, 100 cpm, 1000 cpm, 10000 cpm, 100000 cpm, etc. This ensures the accuracy of liquid scintillation count rate measurement.
[0072] Preferably, the absorbance value is controlled to be between 0.01 and 1.0, specifically such as 0.01, 0.05, 0.1, 0.5, and 1.0. This ensures a linear correlation between the spectral response and the molar concentration.
[0073] According to an embodiment of the present invention, the ultraviolet-visible spectrophotometry satisfies at least one of the following conditions: The wavelength range is 200~1400 nm; The spectral wavelength interval is 0.1~1.0 nm; The scan rate is 60~600 nm / min.
[0074] By adopting the above technical solution, the wavelength range covers the characteristic absorption bands of plutonium ions in all valence states. The 400–800 nm range can be used for quantitative analysis of Pu(IV), while the near-infrared range can be used to monitor interference from other valence states or impurities. The spectral wavelength interval ensures that the fine structure of the characteristic absorption peaks is fully acquired, avoiding peak shape distortion or peak area integration error caused by excessively large wavelength intervals, while also taking into account data acquisition efficiency. The scanning rate can improve measurement throughput while ensuring spectral resolution, avoiding redshift or peak height reduction caused by excessively fast scanning, and ensuring the accuracy and repeatability of spectral data.
[0075] For example, the wavelength range of the absorption spectrum can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, etc.; the spectral wavelength interval can be 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1.0nm, etc.; the scanning rate can be 60nm / min, 80nm / min, 100nm / min, 150nm / min, 200nm / min, 300nm / min, 400nm / min, 500nm / min, 600nm / min, etc.
[0076] A second aspect of the present invention provides an application of the aforementioned measurement method in nuclear fuel cycle, nuclear facility decommissioning, or nuclear safety regulation.
[0077] In some embodiments, the application includes online or offline monitoring of the specific activity of mixed plutonium solutions during spent fuel reprocessing.
[0078] In some embodiments, the application includes the determination of plutonium activity concentration in radioactive waste liquids during the decommissioning of nuclear facilities and the calculation of nuclear material balances.
[0079] In some embodiments, the application includes rapid screening and radioactivity level assessment of plutonium samples from unknown sources in the field of nuclear safety regulation.
[0080] In some embodiments, the application includes quality control and specific activity calibration of plutonium products in nuclear material management.
[0081] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.
[0082] Example 1 A method for determining the specific activity of a plutonium solution, comprising: Take a known concentration 242 Pu solution was used as standard solution 1, and the perchloric acid concentration of the standard solution was 3 mol / L. The specific activity A1 of the standard solution was calculated to be 3.5463 × 10⁻⁶. 10 Bq / mol; The liquid scintillation count rate of the standard solution was determined and denoted as C1; The absorption spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, as shown below. Figure 1 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 1 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the standard solution, as shown in the figure. Figure 1 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the standard solution was measured and denoted as S1; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 1 As shown in (d); Pick 238 Pu、 239 Pu、 240 The mixed plutonium solution of Pu was used as the test solution 1. The perchloric acid concentration of the test solution was 3 mol / L. The liquid scintillation count rate of the test solution was measured and recorded as C2. The absorption spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, as follows: Figure 2 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 2 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the test solution, as shown in the figure. Figure 2 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the test solution was measured and denoted as S2; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 2 As shown in (d); The specific activity A2 of the test solution was calculated according to the following formula, and the results are recorded in Table 1.
[0083]
[0084] Wherein, A2 represents the specific activity of the solution to be tested; S1 represents the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the standard solution; S2 represents the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution; V1 represents the volume of the standard solution used to test the liquid flash count rate; V2 represents the volume of the solution to be tested when the liquid flash count rate is measured; C1 represents the liquid scintillation count rate of the standard solution; C2 represents the liquid scintillation count rate of the solution to be tested; A1 represents the specific activity of the standard solution.
[0085] Example 2 A method for determining the specific activity of a plutonium solution, comprising: Take a known concentration different from the above examples 242 Pu solution was used as standard solution 2. The perchloric acid concentration of the standard solution was 3 mol / L. The specific activity A1 of the standard solution was calculated to be 3.5463 × 10⁻⁶. 10 Bq / mol; The liquid scintillation count rate of the standard solution was determined and denoted as C1; The absorption spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, as shown below. Figure 1 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 1 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the standard solution, as shown in the figure. Figure 1 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the standard solution was measured and denoted as S1; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 1 As shown in (d); Take a composition different from the above embodiments 238 Pu、 239 Pu、 240 The mixed plutonium solution of Pu was used as test solution 2. The perchloric acid concentration of the test solution was 3 mol / L. The liquid scintillation count rate of the test solution was measured and recorded as C2. The absorption spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, as follows: Figure 2 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 2 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the test solution, as shown in the figure. Figure 2As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the test solution was measured and denoted as S2; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 2 As shown in (d); According to the formula The specific activity A2 of the test solution was calculated, and the results are recorded in Table 1.
[0086] Example 3 A method for determining the specific activity of a plutonium solution, comprising: Take a known concentration different from the above examples 242 Pu solution was used as standard solution 3, and the perchloric acid concentration of the standard solution was 3 mol / L. The specific activity A1 of the standard solution was calculated to be 3.5463 × 10⁻⁶. 10 Bq / mol; The liquid scintillation count rate of the standard solution was determined and denoted as C1; The absorption spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, as shown below. Figure 1 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 1 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the standard solution, as shown in the figure. Figure 1 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the standard solution was measured and denoted as S1; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 1 As shown in (d); Take a composition different from the above embodiments 238 Pu、 239 Pu、 240 The mixed plutonium solution of Pu was used as the test solution 3. The perchloric acid concentration of the test solution was 3 mol / L. The liquid scintillation count rate of the test solution was measured and recorded as C2. The absorption spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, as follows: Figure 2 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 2 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the test solution, as shown in the figure. Figure 2 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the test solution was measured and denoted as S2; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 2 As shown in (d); According to the formula The specific activity A2 of the test solution was calculated, and the results are recorded in Table 1.
[0087] Example 4 A method for determining the specific activity of a plutonium solution, comprising: Take a known concentration different from the above examples 242 Pu solution was used as standard solution 4. The perchloric acid concentration of the standard solution was 3 mol / L. The specific activity A1 of the standard solution was calculated to be 3.5463 × 10⁻⁶. 10 Bq / mol; The liquid scintillation count rate of the standard solution was determined and denoted as C1; The absorption spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, as shown below. Figure 1 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 1 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the standard solution, as shown in the figure. Figure 1 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the standard solution was measured and denoted as S1; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 1 As shown in (d); Take a composition different from the above embodiments 238 Pu、 239 Pu、 240 The mixed plutonium solution of Pu was used as the test solution 4. The perchloric acid concentration of the test solution was 3 mol / L. The liquid scintillation count rate of the test solution was measured and recorded as C2. The absorption spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, as follows: Figure 2 As shown in (a) above; establish the absorbance-liquid scintillation count rate relationship curve, as follows. Figure 2 As shown in (b) of the figure; the second derivative of the absorption spectrum is used to obtain the second derivative spectrum of the test solution, as shown in the figure. Figure 2 As shown in (c); the peak area of the characteristic absorption peak of tetravalent plutonium (Pu(IV)) in the second-order conduction spectrum of the test solution was measured and denoted as S2; the relationship curve between the second-order conduction absorption peak area and the liquid scintillation count rate was established, as shown in (c). Figure 2 As shown in (d); According to the formula The specific activity A2 of the test solution was calculated, and the results are recorded in Table 1.
[0088] Table 1. Test results of the standard solution and the test solution described in Example 1.
[0089] from Figures 1-2As shown in Table 1, the second-order peak area of both the standard solution and the test solution is linearly related to the liquid scintillation count rate. The determination method of the present invention does not require the measurement of the isotopic composition of the unknown mixed plutonium solution sample, and can accurately and quickly determine the specific activity of the test solution with unknown isotopic composition, with good accuracy.
[0090] In the description of this specification, the references to terms such as "an embodiment," "some embodiments," "a method of implementation," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0091] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for determining the specific activity of a plutonium solution, characterized in that, include: A plutonium solution with a known specific activity of A1 was used as a standard solution, and the liquid scintillation count rate of the standard solution was determined and denoted as C1. The second-order guide spectrum of the standard solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the standard solution was determined and denoted as S1. The liquid scintillation count rate of the test solution is determined and denoted as C2; The second-order guide spectrum of the test solution was obtained by ultraviolet-visible absorption spectroscopy, and the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution was determined and denoted as S2. The specific activity A2 of the test solution is calculated using the following formula: Wherein, A2 represents the specific activity of the solution to be tested; S1 represents the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the standard solution; S2 represents the peak area of the characteristic absorption peak of tetravalent plutonium in the second-order guide spectrum of the test solution; V1 represents the volume of the standard solution used when testing the liquid flash count rate; V2 represents the volume of the solution to be tested when the liquid flash count rate is measured; C1 represents the liquid scintillation count rate of the standard solution; C2 represents the liquid scintillation count rate of the solution to be tested; A1 represents the specific activity of the standard solution.
2. The determination method according to claim 1, characterized in that, The standard solution includes 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 One or more of Pu.
3. The determination method according to claim 2, characterized in that, The standard solution is a single isotope plutonium solution, which includes... 238 Pu、 239 Pu、 240 Pu、 241 Pu、 242 Any of the following in Pu, preferred 242 Pu.
4. The determination method according to claim 1, characterized in that, Both the standard solution and the test solution are plutonium perchloric acid solutions.
5. The determination method according to claim 4, characterized in that, The concentration of perchloric acid in the standard solution and the test solution is ≥1 mol / L.
6. The determination method according to claim 1, characterized in that, The characteristic absorption peak is located at 460~480nm.
7. The determination method according to any one of claims 1 to 6, characterized in that, The determination method satisfies at least one of the following conditions: The liquid scintillation count rate is measured within the effective linear measurement range of the liquid scintillation counter; The ultraviolet-visible absorption spectrum was measured within a range where absorbance and concentration were linearly related.
8. The determination method according to claim 7, characterized in that, The determination method satisfies at least one of the following conditions: The liquid scintillation count rate is controlled to be 10 to 10. 5 cpm; The absorbance value is controlled to be between 0.01 and 1.
0.
9. The determination method according to any one of claims 1 to 6, characterized in that, The ultraviolet-visible spectrophotometry method satisfies at least one of the following conditions: The wavelength range is 200~1400 nm; The spectral wavelength interval is 0.1~1.0 nm; The scan rate is 60~600 nm / min.
10. The application of the determination method as described in any one of claims 1 to 9 in nuclear fuel cycle, nuclear facility decommissioning, or nuclear safety supervision.