A uranium-aluminum alloy for uranium-molybdenum-technetium targets and its preparation method

Abstract

This invention discloses a uranium-aluminum alloy for uranium-molybdenum-technetium targets and its preparation method. The uranium content in the uranium-aluminum alloy is 25.4 ± 2.0 wt%. The impurity content of the uranium-aluminum alloy meets the following requirements: B ≤ 1 μg / g, Cd ≤ 2 μg / g, Li ≤ 8 μg / g, C ≤ 600 μg / g, Cr ≤ 240 μg / g, Cu ≤ 100 μg / g, Fe ≤ 1000 μg / g, Ni ≤ 250 μg / g, and Gd ≤ 0.25 μg / g. The density of the uranium-aluminum alloy is 3.0–3.4 g / cm³. 3 The uranium-aluminum alloy comprises Al, UAl3, and UAl4 phases. The preparation method of the uranium-aluminum alloy includes the following steps: first, heating to 1190-1220℃ within 50-80 minutes; then holding at 1190-1220℃ for 57-63 minutes; then cooling naturally to 990-1030℃; finally, tilting and casting into a mold at 350-500℃, followed by annealing the prepared ingot under vacuum at 580-640℃ for 10-25 hours. This invention enables the production of uranium-aluminum alloys with controllable composition, density, phase, and microstructure through induction melting-tilt casting-annealing, meeting production requirements. 99 Requirements for uranium-aluminum alloy targets for Mo.

Description

Technical Field

[0001] This invention belongs to the field of uranium metallurgy technology, specifically relating to a uranium-aluminum alloy for uranium-molybdenum-technetium targets and its preparation method. Background Technology

[0002] Uranium-aluminum alloy targets are used to produce 99Mo isotopes via reactor fission. Utilizing the property of 235U fission to produce 99Mo (yield of 6.06%), irradiating the uranium-aluminum alloy target in a reactor can achieve a specific activity of 10,000 Ci / g (370 TBq / g). This method is suitable for large-scale production of high-specific-activity 99Mo products, and subsequently for the production of the medical radioactive isotope 99mTc. Low-enriched uranium is beneficial for nuclear non-proliferation; therefore, using uranium-aluminum alloy targets to produce 99Mo via fission has become the main technical route for 99Mo production both domestically and internationally.

[0003] The uranium-aluminum alloy target uses uranium-aluminum alloy as the core for producing 99Mo. The uniformity of uranium element distribution, density, and impurity content are key indicators of the uranium-aluminum alloy, with compositional uniformity being the most critical performance parameter. Significant density differences exist between metallic aluminum and uranium, and between metallic aluminum and uranium-aluminum compounds. Under liquid conditions, this easily leads to incomplete uranium-aluminum reaction and significant density segregation, affecting the performance of the uranium-aluminum alloy. Therefore, achieving uniform density and composition in the uranium-aluminum alloy is challenging, making compositional uniformity control a crucial technology. Furthermore, considering the requirements of subsequent target processing on the microstructure and properties of the uranium-aluminum alloy, the microstructure needs to be controlled through annealing processes to regulate its mechanical properties.

[0004] Currently, the most commonly used method for preparing uranium-aluminum alloys is centrifugal casting. This method has the advantage of fast cooling speed, resulting in good compositional uniformity. However, the production throughput is small, and the ingot shape is limited to cylindrical parts, which cannot meet the needs of mass production of uranium-aluminum alloy ingots of various shapes.

[0005] The tilt casting method has the advantages of large throughput and unrestricted ingot shape, but due to the slow cooling rate, it is prone to compositional segregation. Therefore, the control technology of compositional uniformity in the preparation of uranium-aluminum alloys by tilt casting is a key technology that needs to be mastered. Summary of the Invention

[0006] To address the above shortcomings, the purpose of this invention is to provide a uranium-aluminum alloy for uranium-molybdenum-technetium targets and its preparation method. Based on the requirements for the composition, density, phase composition, and microstructure of the uranium-aluminum alloy for producing 99Mo uranium-aluminum alloy targets, an induction melting-tilt casting-annealing preparation process was designed. This induction melting-tilt casting-annealing process can prepare uranium-aluminum alloys with composition, density, phase composition, and microstructure that meet the requirements for uranium-aluminum alloy targets.

[0007] The technical solution of the present invention is as follows:

[0008] A uranium-aluminum alloy for use in uranium-molybdenum-technetium targets, wherein the uranium content in the uranium-aluminum alloy is 25.4 ± 2.0 wt%.

[0009] The impurity content of the uranium-aluminum alloy meets the following requirements: B≤1μg / g, Cd≤2μg / g, Li≤8μg / g, C≤600μg / g, Cr≤240μg / g, Cu≤100μg / g, Fe≤1000μg / g, Ni≤250μg / g, and Gd≤0.25μg / g.

[0010] The density of the uranium-aluminum alloy is 3.0-3.4 g / cm³. 3 .

[0011] The phases of the uranium-aluminum alloy are Al, UAl3, and UAl4.

[0012] A method for preparing uranium-aluminum alloy for uranium-molybdenum-technetium targets includes four steps;

[0013] Step 1, Ingredients: Based on the target aluminum content of 74.6 wt%, add an appropriate excess of 0.1-0.5 wt% aluminum;

[0014] Step 2, Induction Melting: First, heat the temperature to 1190-1220℃ within 50-80 minutes; then hold the temperature at 1190-1220℃ for 57-63 minutes; then stir mechanically for 15-20 minutes each time, for a total of 3-4 times; then cool down naturally to 990-1030℃.

[0015] Step 3, Casting: Pour the casting into the mold, with the mold temperature at 350-500℃;

[0016] Step 4, Annealing: 580-640℃, hold under vacuum for 10-25 hours.

[0017] In step three, the casting method is tilt casting, and the tilt casting temperature is 600-900℃.

[0018] In step three, a flow divider is provided above the mold. The flow divider has 3-5 holes with a diameter of Ф5-9mm.

[0019] In step three, the inner diameter of the mold is Ф30-100mm, the outer diameter is Ф80-120mm, and the height is 200-350mm.

[0020] In step three, a flow divider is provided above the mold. The flow divider has 3-5 holes with a diameter of Ф5-9mm.

[0021] In step three, the inner diameter of the mold is Ф30-100mm, the outer diameter is Ф80-120mm, and the height is 200-350mm.

[0022] The beneficial effects of this invention are as follows:

[0023] A designed induction melting-tilt casting-annealing process for uranium-aluminum alloy was employed. By designing parameters such as melting temperature, pouring temperature, pouring speed, mold temperature, and annealing time and temperature, the problems of internal porosity and compositional segregation in the ingot were solved. The resulting uranium-aluminum alloy had a uranium content of 25.4±2.0wt%, and impurity contents meeting the following requirements: B≤1μg / g, Cd≤2μg / g, Li≤8μg / g, C≤600μg / g, Cr≤240μg / g, Cu≤100μg / g, Fe≤1000μg / g, Ni≤250μg / g, Gd≤0.25μg / g. The density was 3.0-3.4g / cm3, and the phases were Al, UAl3, and UAl4. Its composition, density, phases, and microstructure all met the requirements for manufacturing 99Mo uranium-aluminum alloy targets. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for preparing uranium-aluminum alloy for uranium-molybdenum-technetium targets according to the present invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] 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.

[0027] A uranium-aluminum alloy for use in uranium-molybdenum-technetium targets, wherein the uranium content in the uranium-aluminum alloy is 25.4 ± 2.0 wt%.

[0028] The impurity content of the uranium-aluminum alloy meets the following requirements: B≤1μg / g, Cd≤2μg / g, Li≤8μg / g, C≤600μg / g, Cr≤240μg / g, Cu≤100μg / g, Fe≤1000μg / g, Ni≤250μg / g, Gd≤0.25μg / g;

[0029] The density of the uranium-aluminum alloy is 3.0-3.4 g / cm³. 3 ;

[0030] The phases of the uranium-aluminum alloy are Al, UAl3, and UAl4;

[0031] A method for preparing uranium-aluminum alloy for uranium-molybdenum-technetium targets includes four steps;

[0032] Step 1, Ingredients: Based on the target aluminum content of 74.6 wt%, add an appropriate excess of 0.1-0.5 wt% aluminum.

[0033] Step 2, Induction Melting: First, heat the temperature to 1190-1220℃ within 50-80 minutes; then hold the temperature at 1190-1220℃ for 57-63 minutes; then stir mechanically for 15-20 minutes each time, for a total of 3-4 times; then cool down naturally to 990-1030℃.

[0034] Step 3, Casting: Pour the casting into the mold, with the mold temperature at 350-500℃;

[0035] Step 4, Annealing: 580-640℃, hold under vacuum for 10-25 hours.

[0036] In step three, the casting method is tilt casting, and the tilt casting temperature is 600-900℃.

[0037] In step three, a flow divider is provided above the mold. The flow divider has 3-5 holes with a diameter of Ф5-9mm.

[0038] In step three, the inner diameter of the mold is Ф30-100mm, the outer diameter is Ф80-120mm, and the height is 200-350mm.

[0039] According to the induction melting-tilt casting-annealing method proposed in this invention, multiple uranium-aluminum alloy ingots were manufactured and inspected. The results are as follows:

[0040] Table 1. Results of composition and density analysis of uranium-aluminum alloy

[0041]

[0042] It is evident that the uranium-aluminum alloy prepared by the induction melting-tilt casting-annealing process proposed in this invention meets the technical requirements in terms of composition and density.

[0043] Metallographic and scanning electron microscopy observations were performed on the microstructure of the uranium-aluminum alloy, and XRD was used to detect the phases. The test results showed that the phases were Al, UAl3, and UAl4. The microstructure was characterized by UAl3 and UAl4 dispersed in the Al matrix, with no residual U phase, indicating that the reaction was sufficient during the melting process. After annealing, the dendritic eutectic structure underwent a spheroidization transformation, indicating that the annealing process achieved control over the microstructure and properties.

[0044] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0045] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the 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.

[0046] 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.

[0047] The accompanying drawings of the embodiments disclosed in this invention only involve the methods involved in the embodiments of this disclosure. Other methods can be referred to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A uranium-aluminum alloy for uranium molybdenum rhenium target, the uranium content in the uranium-aluminum alloy is 25.4±2.0wt%, characterized in that: the impurity content of the uranium-aluminum alloy satisfies B≤1μg / g, Cd≤2μg / g, Li≤8μg / g, C≤600μg / g, Cr≤240μg / g, Cu≤100μg / g, Fe≤1000μg / g, Ni≤250μg / g, Gd≤0.25μg / g; the phase of the uranium-aluminum alloy is Al, UAl3, UAl4.

3. A preparation method of a uranium-aluminum alloy for uranium molybdenum rhenium target, comprising four steps, characterized in that: step one, batching: based on the target value of aluminum content of 74.6wt%, aluminum is appropriately excessive by 0.1-0.5wt%; step two, induction melting: first heating, heating to 1190-1220℃ within 50-80min; then holding, holding at 1190-1220℃ for 57-63min; then stirring, performing mechanical stirring, 15-20min each time, a total of 3-4 times, then cooling, naturally cooling to 990-1030℃; step three, casting: casting into a mold, the mold temperature is 350-500℃; step four, annealing: 580-640℃, holding under vacuum for 10-25h. In the step three, the casting mode is tilting casting, and the tilting casting temperature is 600-900℃.

2. A uranium-aluminum alloy for a uranium-molybdenum-technetium target as defined in claim 1, characterized in that: The uranium-aluminum alloy has a density of 3.0-3.4 g / cm 3 . In the step three, a shunt disc is arranged above the mold, the shunt disc is provided with 3-5 holes, and the shunt disc hole diameter is Ф5-9mm. In the step three, the mold inner diameter is Ф30-100mm, the outer diameter is Ф80-120mm, and the height is 200-350mm. In the step three, a shunt disc is arranged above the mold, the shunt disc is provided with 3-5 holes, and the shunt disc hole diameter is Ф5-9mm. In the step three, the mold inner diameter is Ф30-100mm, the outer diameter is Ф80-120mm, and the height is 200-350mm. ​ 4. A method of producing a uranium-aluminum alloy for a uranium-molybdenum-technetium target according to claim 3, characterized in that: ​ 5. The method of claim 3 wherein the uranium-aluminum alloy is prepared by the steps of: providing a uranium-aluminum alloy; and heat treating the uranium-aluminum alloy to produce a uranium-aluminum alloy having a grain size of less than 100 microns. ​ 6. A method of making a uranium-aluminum alloy for a uranium-molybdenum-technetium target as defined in claim 3, wherein: ​ 7. A method of making a uranium-aluminum alloy for a uranium-molybdenum-technetium target as defined in claim 4, wherein: ​ 8. A method of producing a uranium-aluminum alloy for a uranium-molybdenum-technetium target according to claim 7, characterized in that: ​

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