Actinide target sample preparation method based on Fe / Ti-Nb ratio optimization and application

Abstract

The application belongs to the technical field of accelerator mass spectrometry (AMS) measurement, and particularly relates to an actinide AMS target sample preparation method based on Fe / Ti-Nb ratio optimization, which comprises sample separation and purification, coprecipitation, dry mixing and target pressing steps. The dosages of the coprecipitation carrier and the conductive matrix are synergistically controlled to improve the detection efficiency of the target nuclide. Specifically, the coprecipitation carrier is iron and / or titanium, the conductive matrix is niobium powder, the iron carrier addition amount is controlled to be 0.4-0.5 mg, the titanium carrier addition amount is controlled to be 0.08-0.12 mg, and the niobium powder addition amount is controlled to be 3-6 mg. The carrier selection is optimized, the coprecipitation effect is stabilized under the condition of ensuring the conductivity, and the detection efficiency is improved. The provided ratio range is based on experimental research, has good repeatability, and is suitable for the high-sensitivity AMS detection requirements of super-trace multiple actinides.

Description

Technical Field

[0001] This invention belongs to the field of accelerator mass spectrometry (AMS) measurement technology, specifically relating to a method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization. This method optimizes the type and amount of carrier and the ratio of conductive matrix to improve the performance of target nuclides (such as Pu isotopes). 237 Np, 241 Am、 244 A target preparation method for detecting transuranic nuclides (Cm, etc.) with high efficiency. It can be applied to scenarios involving the detection of transuranic nuclides, such as environmental monitoring, nuclear science research, and radioactive waste analysis. Background Technology

[0002] Accelerator mass spectrometry (AMS) technology has the advantage of high sensitivity in the detection of trace actinide nuclides (such as Np and Pu), and its detection performance largely depends on the target preparation process. In existing technologies, the target nuclide is usually immobilized on a support (such as Fe or Ti) by hydroxide coprecipitation, and then mixed with a conductive matrix (such as Nb powder) and pressed into a target to form a target sample that can be sputtered by an ion source.

[0003] Existing AMS target preparation methods typically have the following technical characteristics:

[0004] 1) Most methods use a single type of support (such as Fe or Ti), and the amount added is often based on experience, lacking research on the optimal amount for different nuclide systems. In particular, the synergistic effects of different coprecipitants on coprecipitation efficiency, conductivity, and mixing uniformity with Nb powder have not been systematically investigated.

[0005] 2) Existing methods use a wide range of carrier dosages. A common practice is to use a high dose (e.g., 1-5 mg) to ensure complete precipitation of the nuclide. However, this does not fully consider the problems caused by excessive precipitation, over-dilution of the target nuclide, and uneven mixing with the conductive matrix, which affect the final ionization and transport efficiency.

[0006] 3) As a commonly used conductive matrix, the amount of Nb powder is usually fixed or adjusted only within a small range (e.g., 5-6 mg), and there is a lack of systematic research on the matching relationship between it and the amount of carrier precipitation. Especially under the condition of high carrier dosage, the amount of Nb powder has not been optimized accordingly, resulting in discontinuity of conductive network or decreased sputtering stability.

[0007] Due to the aforementioned existing technical features, the existing AMS target preparation methods often suffer from the following problems: low detection efficiency, large differences in detection efficiency between different nuclides, a sharp drop in detection efficiency when using high carrier amounts, and insufficient repeatability and stability of the target preparation methods. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention aims to provide an optimized AMS target preparation method. This method, through systematic control of the type and amount of Fe and / or Ti support and its ratio with the niobium (Nb) powder conductive matrix, aims to achieve the desired target actinide nuclides (such as Pu isotopes, ...). 237 Np, 241 Am or 244 Maximize detection efficiency (e.g., Cm).

[0009] To achieve the above objectives, this invention provides a method for preparing actinide AMS target samples based on optimized Fe / Ti-Nb ratios. The method includes sample separation and purification, co-precipitation, drying and mixing, and target pressing steps. The amounts of the co-precipitation support and the conductive matrix are synergistically controlled to improve the detection efficiency of the target nuclide. Specifically, the co-precipitation support is iron and / or titanium, the conductive matrix is ​​niobium powder, and the amount of iron support added is controlled at 0.4-0.5 mg, the amount of titanium support added is 0.08-0.12 mg, and the amount of niobium powder added is controlled at 3-6 mg.

[0010] Furthermore, in a specific embodiment, in the above-described method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization, if the co-precipitation support is iron and titanium, the mass ratio of the iron support to the titanium support is in the range of 4:1 to 5:1.

[0011] Furthermore, in a specific embodiment, in the actinide AMS target preparation method based on Fe / Ti-Nb ratio optimization as described above, the mass ratio of the precipitate generated in the co-precipitation step to the niobium powder ranges from 1:3 to 1:6.

[0012] Furthermore, in a specific embodiment, the method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described above, wherein the actinide nuclides include... 237 Np, 239 Pu、 240 Pu、 241 Pu、 242 Pu、 241 Am、 243 Am or 244 At least one of Cm.

[0013] Furthermore, in a specific embodiment, the method for preparing actinide AMS targets based on Fe / Ti-Nb ratio optimization as described above, wherein the actinide is... 237 Np and 242 The amount of iron carrier added is controlled at 0.4-0.5 mg, the amount of titanium carrier added is controlled at 0.10-0.12 mg, and the amount of niobium powder added is controlled at 5-6 mg.

[0014] Furthermore, in a specific embodiment, the method for preparing actinide AMS targets based on Fe / Ti-Nb ratio optimization as described above, wherein the actinide is... 241 Am and 244 Cm, control the amount of iron carrier added to be 0.4-0.5mg, and the amount of titanium carrier added to be 0-0.1mg.

[0015] Furthermore, in a specific embodiment, the method for preparing actinide AMS targets based on Fe / Ti-Nb ratio optimization as described above is applied to the simultaneous detection of ultra-trace actinides in environmental and biological samples.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. Improved detection efficiency: By limiting the amount of Fe carrier to a low level (≤0.5mg), the dilution effect of the nuclide caused by excessive precipitation and the problem of uneven mixing with Nb powder are effectively avoided, thus improving detection efficiency. 237 Np and 242 The detection efficiency of Pu can be improved by more than an order of magnitude compared to the high carrier dosage (≥3mg) scheme.

[0018] 2. Optimize the selection of the support: It was found that Fe support is superior to Ti support in terms of conductivity, while Ti support has a higher co-precipitation ability. The Fe:Ti mass ratio range is 4:1 to 5:1 to ensure stable co-precipitation effect while ensuring conductivity.

[0019] 3. Determine the amount of conductive matrix Nb powder to be in the range of 3-6 mg. This will provide sufficient conductivity and sample loading while avoiding dilution of the target nuclide by excessive Nb powder, thus ensuring stable sputtering and efficient ionization of the ion source.

[0020] 4. The provided formulation range is based on experimental research, has good repeatability, and is suitable for ultra-trace applications. 237 Np, 239 Pu、 240 Pu、 241 Pu、 242 Pu、 241 Am、 243 Am or 244 The need for high-sensitivity AMS detection of various actinide nuclides such as Cm. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the preparation of actinide accelerator mass spectrometry (AMS) target samples using a coprecipitation method. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] The terms “comprising”, “including”, etc., as used herein indicate the presence of the steps, features, operations, or components, but do not preclude the addition of one or more other steps, features, operations, or components.

[0026] The procedure for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization is as follows: Figure 1 As shown.

[0027] A method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization includes the following steps:

[0028] Step 1: Add 0.4 mg Fe and 0.1 mg Ti to the target nuclide test solution (volume 15 ml, concentration on the order of f g / ml) isolated and purified from the sample, and mix well;

[0029] Step 2: Add concentrated ammonia to adjust the pH to 7-8, co-precipitate Pu and Np in the test solution of the target nuclide, and let stand for 30 minutes;

[0030] Step 3: Centrifuge, remove the supernatant, wash the precipitate once with ultrapure water, and retain the precipitate;

[0031] Step 4: Wash the precipitate with methanol, centrifuge, and remove the supernatant;

[0032] Step 5: Remove the precipitate and dry it at 100℃ for 12 hours;

[0033] Step 6: Add 3-6 mg of high-purity Nb powder, mix well, and prepare the target sample.

[0034] Example 1

[0035] against 242 Pu、 237The preparation of Np AMS target samples was improved by adjusting the ratio of Fe, Ti support and Nb powder. 237 Np and 242 The detection efficiency of Pu was determined. The results showed that the type and amount of carrier, as well as its ratio with Nb powder, jointly determined the final detection efficiency.

[0036] Table 1. Pu / Np detection efficiency under different target preparation schemes

[0037]

[0038] As shown in Table 1, for samples 1 and 2, when 1 mg of carrier was used, the amount of precipitate generated by the Ti carrier was slightly higher than that of the target sample prepared with the same mass of Fe carrier, but the corresponding... 237 Np detection efficiency (1.19×10) -4 However, the precipitation efficiency was lower than that of Fe support. This indicates that in AMS target preparation, the amount of precipitate generated by Fe and Ti supports during the co-precipitation step may not be the main influencing factor, and the difference in precipitation efficiency is not significant; however, the physicochemical properties of the support, especially its conductivity and its effect on the uniformity of the sputtering matrix, jointly affect the detection efficiency. Clearly, Fe has better conductivity than Ti.

[0039] As shown in the data of samples 3-7 in Table 1, when the Fe dosage is 0.4 mg, a small amount of Ti is retained to ensure precipitation efficiency. 237 Np and 242 The detection efficiency of Pu reached its highest level; when the Fe dosage was increased to 0.5 mg, the detection efficiency slightly decreased to 4.24 × 10⁻⁶. -4 (Np); However, when the Fe dosage is further increased to 3 mg and 5 mg, the precipitation amount increases significantly, causing severe nuclide dilution and uneven mixing with Nb powder, resulting in a decrease in detection efficiency. It can be seen that excessive carrier will cause a loss of detection efficiency.

[0040] As shown in the data for samples 8, 5, and 9 in Table 1, the amount of conductive matrix Nb powder also requires a specific ratio. With a fixed Fe dosage of 0.5 mg, when the Nb powder dosage increases from 3 mg to 5 mg, 242 The Pu detection efficiency did not change significantly; however, when the Nb powder dosage increased to 9.81 mg, 242 The detection efficiency of Pu actually decreased by about 35%, indicating that excessive Nb powder can affect charge transport efficiency by diluting the target nuclide.

[0041] This invention optimizes 242 Pu、 237When preparing Np targets, the ratio of Fe and Ti carriers to Nb powder in the conductive matrix is ​​0.4-0.5 mg of Fe and 0.10-0.12 mg of Ti, with approximately 5-6 mg of Nb powder. This combines the advantages of high ionization efficiency of Fe carrier and strong co-precipitation enrichment ability of Ti carrier. While ensuring co-precipitation efficiency and operability of target preparation, the detection efficiency is improved by about 2 times compared to using 1 mg of Fe as the carrier.

[0042] Example 2

[0043] For the preparation of target samples for curium (Cm) and americium (Am) nuclides in accelerometer mass spectrometry (AMS) measurements, this invention significantly improves the accuracy by systematically adjusting the ratio of iron (Fe), titanium (Ti) supports to niobium (Nb) conductive matrix. 244 Cm and 243 The detection efficiency of Am was assessed. The results indicate that the type and amount of carrier used are key factors determining detection performance.

[0044] Table 2. Detection efficiency and differentiation coefficient of Am / Cm under different target preparation schemes.

[0045]

[0046] As shown in the data for samples 1 and 6 in Table 2, when the total amount of carrier added is 1 mg, the amount of precipitate generated using pure Ti carrier is relatively large, but its corresponding... 243 Am detection efficiency was significantly lower than that using 1 mg of pure Fe support. This indicates that the physicochemical properties of the support, such as conductivity, have a greater impact on ionization efficiency than the difference in co-precipitation ability.

[0047] As shown in the data of samples 3-7 in Table 2, when the amount of Fe carrier is 0.5 mg, 243 Am and 244 The detection efficiency of Cm reached its peak. However, when the Fe dosage increased to 1 mg, the detection efficiency began to decline; when the Fe dosage was further increased to 3 mg, the detection efficiency dropped sharply to 4.5 × 10⁻⁶. -5 (Am) and 9.4×10 -5 (Cm) verified the necessity of low Fe dosage.

[0048] Furthermore, within the optimized range of low carrier dosage, 243 Am and 244 The differentiation coefficient (Am / Cm) of Cm remains relatively stable, indicating that this method does not introduce a significant nuclide fractionation effect while improving absolute efficiency, which is beneficial for the high-precision determination of nuclide ratios.

[0049] This invention optimizes the carrier ratio for Am and Cm target sample preparation, explicitly proposing the use of 0.4-0.5 mg of Fe as the primary carrier, while controlling the addition of Ti to 0-0.1 mg as an auxiliary. This approach fully leverages the high conductivity of Fe, while simultaneously allowing for the adjustment of precipitation physical properties with a small amount of Ti. Compared to the conventional method using 1 mg of Ti as the carrier, this method, while ensuring effective nuclide enrichment and convenient target sample preparation, can achieve [significant improvement in efficiency]. 243 Am and 244 The detection efficiency of Cm is improved by about 4-6 times.

[0050] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. Thus, the invention also intends to include such variations and adaptations if they fall within the scope of the claims and their equivalents.

[0051] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of protection of the present invention should be defined by the claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization, comprising sample separation and purification, co-precipitation, drying and mixing, and target pressing steps, characterized in that, The dosage of coprecipitation support and conductive matrix is ​​synergistically controlled to improve the detection efficiency of target nuclides. Specifically, the coprecipitation support is iron and / or titanium, the conductive matrix is ​​niobium powder, the iron support is added at 0.4-0.5 mg, the titanium support is added at 0.08-0.12 mg, and the niobium powder is added at 3-6 mg.

2. The method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in claim 1, characterized in that, If the coprecipitation support is iron and titanium, the mass ratio of the iron support to the titanium support is in the range of 4:1 to 5:

1.

3. The method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in claim 1, characterized in that, The mass ratio of the precipitate generated in the co-precipitation step to the niobium powder ranges from 1:3 to 1:

6.

4. The method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in claim 1, characterized in that, The actinide nuclides include 237 Np, 239 Pu、 240 Pu、 241 Pu、 242 Pu、 241 Am、 243 Am or 244 At least one of Cm.

5. The method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in claim 4, characterized in that, If the actinide nuclide is 237 Np and 242 The amount of iron carrier added is controlled at 0.4-0.5 mg, the amount of titanium carrier added is controlled at 0.10-0.12 mg, and the amount of niobium powder added is controlled at 5-6 mg.

6. The method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in claim 4, characterized in that, If the actinide nuclide is 241 Am and 244 Cm, control the amount of iron carrier added to be 0.4-0.5mg, and the amount of titanium carrier added to be 0-0.1mg.

7. The application of the method for preparing actinide AMS target samples based on Fe / Ti-Nb ratio optimization as described in any one of claims 1-6, characterized in that, The method was applied to the simultaneous detection of ultra-trace actinide nuclides in environmental and biological samples.

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