Americium dioxide isotope heat source pellet crushing and recycling treatment device and method

Abstract

The invention discloses a device and a method for crushing and recycling americium dioxide isotope heat source pellets. The device comprises a crushing container tank body, a mechanical arm and an uncovering wrench, the sealing cover is installed on the crushing container tank body through threaded connection, the interior of the sealing cover is a hemispherical structure sealing cover, the interior of the crushing container tank body is a hemispherical structure sealing cover, and a grinding cavity is formed by the sealing cover and the crushing container tank body; the uranium-titanium alloy grinding ball is located in the grinding cavity. Through specific atmosphere pre-sintering treatment, pellet crushing and powder mixing, the particle size of the powder is greatly reduced, the specific surface of the powder and lattice distortion of the powder are increased, the re-sintering activity of the powder is improved, the sintering temperature is reduced in the material recycling and sintering process, volatilization of americium dioxide under the high-temperature condition is prevented, and the sintering quality of americium dioxide is improved. The repeated utilization of the americium dioxide powder is realized. In addition, the material of a crushing container is optimized in the mechanical crushing link of the pellets, introduction of impurities in the mechanical crushing process is avoided, and meanwhile, the phase change problem of americium dioxide at high temperature is avoided through doping of uranium.

Description

Technical Field

[0001] This invention relates to the field of radioactive pellet recycling technology, specifically to a device and method for crushing and recycling americium isotope heat source pellets. Background Technology

[0002] Americium-241, a radioactive isotope with a relatively long half-life (432.5 years), has wide applications in nuclear energy and radioisotope batteries. However, due to unsatisfactory processing results in pressing and sintering, the prepared pellets do not meet the control requirements in terms of density, strength, size, and appearance integrity. Failure to recycle these waste pellets will result in waste of nuclear materials, reduced utilization, and increased storage pressure on nuclear materials and high-level radioactive waste. Currently, dry and wet processes are mainly used domestically and internationally to process waste ceramic pellets from nuclear fuel or radioisotope heat sources. Wet processes are not only complex but also generate large amounts of radioactive liquid waste, resulting in high processing costs. In contrast, dry processes are simpler and less expensive, making them one of the most effective methods for recycling waste pellets from radioisotope heat sources. Traditional crushing methods mainly rely on mechanical methods (such as ball milling). While traditional mechanical crushing (ball milling) can refine the powder, it requires a high total volume of pellets and is ineffective for small batches. Given the strong radioactivity of americium dioxide, the operation must be carried out in a protective glove box. However, existing glove boxes are limited by space size and shielding capabilities, making it difficult to support large-scale processing, and the total mass of chips that can be processed in a single batch is severely limited. In view of this, this patent proposes a method for crushing and recycling americium dioxide radioactive isotope heat source pellets, achieving breakthroughs through three innovations: First, after pre-sintering in a specific atmosphere, crushing and mixing processes significantly reduce powder particle size (increasing specific surface area and lattice distortion), enhance re-sintering activity, lower the reuse sintering temperature, and effectively suppress high-temperature volatilization of americium dioxide. Second, addressing the limitations of glove box space and shielding capability, the container structure and materials are optimized to meet the needs of small-sized pellets and small-batch processing while solving the problems of excessively large and unevenly distributed powder particles in traditional mechanical crushing, ensuring that particle size indicators meet standards and avoiding the introduction of impurities such as Fe, C, Si, and Ca. Third, uranium doping stabilizes the AmO2 lattice structure, preventing cracking during re-sintering. Fourth, the use of uranium-titanium alloy as the container material provides excellent gamma-ray shielding performance, protecting the hands, eyes, and other critical areas of operators and significantly reducing radiation dose. Summary of the Invention

[0003] This invention proposes a method for crushing and recycling americium dioxide radioisotope heat source pellets. The aim is to provide a small-batch, high-efficiency crushing and recycling method suitable for high-radioactivity americium dioxide (AmO2) waste pellets. Under strictly controlled glovebox operating conditions, by optimizing the atmosphere pre-sintering process, designing a dedicated small-volume crushing container, and using shielding materials, three core objectives are achieved: developing a crushing container structure adapted to small-batch processing needs, resolving the contradiction between the high throughput requirements of traditional grinding technology and radioactive protection limitations; ensuring that the particle size, distribution, and purity of the crushed powder meet the resintering index requirements, thereby improving reuse activity; and suppressing phase transition cracking through uranium doping and reducing personnel radiation dose through shielding materials, ultimately achieving green, safe, and high-recovery-rate reuse of americium dioxide waste pellets.

[0004] The technical solution of the present invention is as follows: A crushing and recycling device for americium dioxide isotope heat source core includes a crushing container tank, a robotic arm, and a cap-opening wrench; a sealing cap is installed on the crushing container tank via a threaded connection, the inside of the sealing cap is a hemispherical structure sealing cap, the inside of the crushing container tank is a hemispherical structure sealing cap, and the two form a grinding chamber; uranium-titanium alloy grinding balls are located in the grinding chamber.

[0005] The upper part of the sealing cap and the lower part of the crushing container were respectively perforated.

[0006] The cap opening wrench includes a sealing cap wrench clamping rod, a locating pin, and a crushing tank wrench clamping rod.

[0007] The robotic arm includes a vibrating arm, a gripping mechanism, and a tightening button; the gripping mechanism is located at the end of the robotic arm and fixes the crushed container. After the crushed container is placed into the gripping mechanism, the tightening button locks it in place.

[0008] The sealing cap and the crushing container are both made of uranium-titanium alloy with a hardness of 450-455 HV. The uranium-titanium alloy grinding balls are made of uranium-titanium alloy with a titanium content of 0.70-0.72 wt%, a grinding ball hardness of 450-455 HV, and a grinding ball size of 15 mm-20 mm.

[0009] A method for crushing and recycling americium dioxide isotope heat source pellets includes the following steps:

[0010] Step 1: Pre-sinter the americium isotope heat source core in an atmosphere of hydrogen and argon mixture; complete the first crushing process of the core.

[0011] Step 2: Mechanical crushing of americium dioxide isotope heat source core blocks; Weigh the core blocks crushed in Step 1 and place them into the crushing container tank, and at the same time load one uranium-titanium alloy grinding ball. The sealing cap is installed on the crushing container tank through a threaded connection, and the crushing container tank is vibrated by a robotic arm to perform grinding.

[0012] Step 3: Powder mixing; Obtain the powder from Step 2, add zinc stearate as a binder to mix and agglomerate the powder produced in Step 2.

[0013] In step one, a dry, flowing hydrogen-argon mixture is used, with a hydrogen content of 5wt% to 6wt%, and the gas flow rate is controlled at 2.5L / min to 6L / min. The pre-sintering temperature of the americium isotope heat source core is 800℃ to 1200℃, the holding time is 3h to 8h, and the heating and cooling rates are selected as 10℃ / min to 15℃ / min.

[0014] In step two, the grinding vibration frequency is set to 40Hz to 60Hz, and the grinding time is set to 15min to 45min.

[0015] In step two, after grinding is completed, sampling and analysis are performed according to the powder particle size sampling standard. If the powder particle size D50 ≤ 1 μm, the crushing process is completed; if the powder particle size D50 ≥ 1 μm, step two is repeated until the powder particle size D50 ≤ 1 μm.

[0016] In step three, 0.5 wt% to 0.8 wt% zinc stearate binder is added, and the powder generated in step two is mixed and agglomerated using a roller mixer.

[0017] The significant advantages of this invention are as follows: Through specific atmosphere pre-sintering treatment, core block crushing, and powder mixing, this invention significantly reduces powder particle size, increases powder specific surface area and powder lattice distortion, and improves the powder's resintering reactivity. During the material reuse sintering process, the sintering temperature is lowered, preventing the volatilization of americium dioxide under high-temperature conditions, thus enabling the reusability of americium dioxide powder. Furthermore, the optimized material of the crushing container in the core block mechanical crushing process avoids the introduction of impurities such as Fe, C, Si, and Ca during mechanical crushing. Simultaneously, uranium doping prevents the phase transformation problem of americium dioxide at high temperatures, preventing core block cracking during resintering. By optimizing the container structure, dead zones are avoided during the grinding and cleaning processes, solving problems such as large powder particle size and uneven particle size distribution in traditional mechanical crushing processes, enabling the crushing and reuse of substandard core blocks. In addition, the uranium-titanium alloy material provides shielding for personnel during operation, effectively protecting hands and eyes, reducing radiation exposure, and greatly protecting personnel health.

[0018] This invention features a concise process that produces no radioactive waste liquid. It effectively crushes americium oxide heat source chips, ensuring that the particle size of substandard heat source chip powder meets process requirements. This improves powder flowability and resintering reactivity, enabling the reusability of americium oxide powder and saving manpower and resources, resulting in significant economic benefits. Furthermore, the use of a uranium-titanium alloy chip crushing container in the mechanical crushing stage solves problems such as impurity introduction and substandard powder performance in traditional mechanical crushing processes. Simultaneously, uranium doping prevents the phase transition of americium dioxide at high temperatures, preventing cracking during resintering and achieving the crushing and reuse of substandard americium-241 radioactive isotope heat source chips. Attached Figure Description

[0019] Figure 1 Schematic diagram of the process structure of this invention;

[0020] Figure 2a Schematic diagram of the crushing container structure;

[0021] Figure 2b Schematic diagram of the crushing container structure;

[0022] Figure 3 Schematic diagram of uranium-titanium alloy grinding ball structure;

[0023] Figure 4 Schematic diagram of the cover-opening wrench structure;

[0024] Figure 5 Diagram illustrating the use of the cover-opening wrench;

[0025] Figure 6 A robotic arm that shakes and crushes containers;

[0026] In the diagram: 1. Sealing cap; 2. Crushing container body; 3. Threaded connection; 4. Hemispherical structure tank body; 5. Hemispherical structure sealing cap;

[0027] 6. Sealing cap wrench clamping rod; 7. Positioning pin; 8. Crushing tank wrench clamping rod; 9. Positioning pin; 10. Vibrating arm; 11. Clamping mechanism; 12. Tightening button. Detailed Implementation

[0028] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0029] The terminology used in one or more embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of one or more embodiments of this application. The singular forms “a,” “the,” and “the” used in one or more embodiments of this application and in the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” used in one or more embodiments of this application refers to and includes any or all possible combinations of one or more associated listed items.

[0030] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this application, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this application, and similarly, second may also be referred to as first.

[0031] A density of 85%–90% TD is considered suitable for americium oxide fuel pellets. However, due to the easy volatilization and loss of americium dioxide during high-temperature sintering, it is difficult to increase the pellet density and strength by raising the sintering temperature and extending the holding time. Alternatively, the resintering reactivity of the powder can be improved by reducing the powder particle size to submicron levels and increasing the powder specific surface area. However, because high-temperature sintered ceramicized americium oxide pellets have very high hardness and strength, it is difficult to achieve submicron-level powder through traditional mechanical crushing. Previous grinding and crushing experiments have shown that the median particle size of the crushed pellets after sintering is only about 3.5 μm, corresponding to a maximum sintered pellet density of 81% TD, which cannot meet the density requirements of the heat source pellets. To reduce the particle size of the sintered core block powder to the submicron level, the following principle can be utilized: As temperature increases, the dissociation pressure of metal oxides increases, reducing their affinity for oxygen. During sintering in a reducing atmosphere, the americium dioxide core block loses oxygen atoms, transforming its crystal structure from a face-centered cubic to a close-packed hexagonal structure. This structural volume expansion leads to core block cracking or breakage, thus achieving the initial core block crushing process. Then, mechanical crushing methods are used for secondary powder crushing, further reducing the powder to the submicron level.

[0032] The specific technical content of the present invention will now be described with reference to the accompanying drawings;

[0033] A device for crushing and recycling americium dioxide isotope heat source core includes a crushing container tank 2, a robotic arm, and a lid-opening wrench;

[0034] like Figure 2aAs shown in Figure b, the sealing cap 1 is installed on the crushing container tank 2 via a threaded connection 3. The interior of the sealing cap 1 is a hemispherical sealing cap 5, and the interior of the crushing container tank 2 is also a hemispherical sealing cap 5. Together, they form a grinding chamber without dead corners, with an effective crushing space of approximately 50ml and a length-to-diameter ratio of 1.2:1. This prevents materials from accumulating in dead corners during the grinding and cleaning processes.

[0035] Preferably, both the sealing cap 1 and the crushing container body 2 are made of uranium-titanium alloy (containing 0.70 to 0.72 wt% Ti) with a hardness of 450 to 455 HV.

[0036] Preferably, the wall thickness of the crushing container 2 is 5-10mm, which gives the crushing container high strength and ensures that it can withstand great impact and pressure during the crushing process of the core block.

[0037] Specifically, the upper part of the sealing cap 1 and the lower part of the crushing container tank 2 are respectively perforated (4 holes each for the sealing cap 1 and the crushing container tank 2, and the holes are distributed in a cross shape). The hole diameter is 3mm and the depth is 3mm, which are used for the wrench to hold the cap after grinding.

[0038] like Figure 3 As shown, the uranium-titanium alloy grinding ball is located in the grinding chamber. The material is uranium-titanium alloy, with a titanium content of 0.70-0.72 wt%, a grinding ball hardness of 450-455 HV, and a grinding ball size of 15 mm-20 mm. Unlike traditional grinding methods, this invention uses only one grinding ball, while traditional grinding usually uses multiple small grinding balls. The advantage of using a large-size, high-quality grinding ball is high-energy impact and strong penetration, thereby achieving more thorough powder crushing.

[0039] like Figure 4 , 5 As shown, the cap-opening wrench includes a sealing cap wrench clamping rod 6, a locating pin 7, and a crushing container wrench clamping rod 8. Because the crushing container 2 and the sealing cap 1 are sealed by a threaded connection, finer powder can enter the threaded connection between the crushing container 2 and the sealing cap 1 during the core crushing process, making the cap-opening process difficult. Therefore, a special cap-opening wrench was designed. It is made of 304 stainless steel and is approximately 20cm long.

[0040] Specifically, the operating principle is as follows: the positioning pins of the sealing cap wrench clamping rod 6 and the crushing tank wrench clamping rod 8 are respectively locked in any hole of the sealing cap 1 and the crushing container tank 2 (whichever is convenient to operate), to determine the fulcrum position. The sealing cap wrench clamping rod 6 and the crushing tank wrench clamping rod 8 are rotated with a large range of motion to obtain a small stroke, thereby saving effort and realizing the opening step.

[0041] like Figure 6As shown, the robotic arm that shakes the crushed container 2 includes a vibrating arm 10, a clamping mechanism 11, and a tightening button 12. The clamping mechanism 11 is located at the end of the robotic arm to fix the crushed container 2, while the tightening button 12 is also located at the end of the robotic arm to securely lock the crushed container 2 after it is placed into the clamping mechanism 11, preventing any movement or loosening.

[0042] Specifically, the operating principle is as follows: the crushing container 2 is installed in the designated position of the clamping mechanism 11, and then the button 12 is manually tightened to lock it firmly and prevent any movement. After confirming that the container is securely fixed, the equipment is turned on, the drive system is started, and the vibrating arm 10 begins to move horizontally left and right at high frequency and short strokes, which drives the container and its internal materials and grinding balls to vibrate violently left and right synchronously, thereby achieving effective crushing of the core blocks.

[0043] A method for crushing and recycling americium dioxide isotope heat source pellets includes the following steps:

[0044] Step 1: Pre-sinter the americium isotope heat source core in a reducing atmosphere;

[0045] Dry flowing Ar+H2 (hydrogen content 5wt%~6wt%) was used, with the gas inlet and outlet flow rate controlled at 2.5L / min~6L / min. The pre-sintering temperature of the americium isotope heat source core was 800℃~1200℃, the holding time was 3h~8h, and the heating and cooling rates were selected as 10℃ / min~15℃ / min. This ensured that the crystal structure of the americium isotope heat source core changed from cubic to hexagonal close-packed structure during the pre-sintering process, and the volume expanded (about 1.25~1.5 times), which led to the core cracking or breakage, thus completing the first core crushing treatment.

[0046] Step 2: Mechanical crushing of americium dioxide isotope heat source core

[0047] A secondary crushing process is performed on the crushed core blocks and powder obtained in step 1 using an americium isotope heat source core block crushing and recycling device. Five to eight substandard core blocks are weighed at a time and placed into the crushing container tank 2. Simultaneously, one uranium-titanium alloy grinding ball with a diameter of 15mm to 20mm is added. The sealing cap 1 is installed on the crushing container tank 2 via a threaded connection 3. The crushing container tank 2 is then vibrated by a robotic arm 10 to perform grinding. The grinding vibration frequency is set to 40Hz to 60Hz, and the grinding time is 15min to 45min. After grinding, samples are taken for analysis according to the powder particle size sampling standard. If the powder particle size D50 ≤ 1µm, the crushing process is complete; if the powder particle size D50 ≥ 1µm, step 2 is repeated until the powder particle size D50 ≤ 1µm.

[0048] Step 3: Powder Mixing

[0049] After obtaining the powder from step 2, add 0.5wt%–0.8wt% zinc stearate as a binder, and then use a roller mixer to mix and agglomerate the powder to improve its flowability and pressing performance. A roller mixer is selected as the mixing equipment, with a mixing speed of 150 rpm–350 rpm, a mixing time of 0.5 h–1.5 h, and a filling factor of 0.25%–0.35%. After mixing, the powder particles are nearly spherical, and the loose powder density is 1.5 g / cm³. 3 ~2.2g / cm 3 .

[0050] The particle size of the powder from the initial crushing was measured using a powder particle size analyzer, with a median average particle size of approximately 25.93 μm. To further reduce the powder particle size, mechanical crushing was performed on the powder again, and the particle size of the crushed powder was measured simultaneously, with a median average particle size of approximately 0.874 μm.

[0051] The powder particle size test results are shown in the table below:

[0052] Table 1 Powder particle size detection results

[0053]

[0054] Finally, the powder, after secondary crushing, was mixed, spheroidized, pressed, and sintered to obtain americium oxide core blocks again. These blocks exhibited good appearance integrity, without cracks or breakage. Random samples were taken to measure the sintered density of the core blocks, with an average density of 87.1% TD, meeting the technical requirements. Specific results are as follows:

[0055] Table 2 Core Density Test Results

[0056]

[0057]

[0058] The above description is only 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.

[0059] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0060] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0061] The preferred embodiments disclosed above are merely illustrative of this application. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this application. These embodiments are selected and specifically described in this application to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to better understand and utilize this application.

Claims

1. A device for crushing and recycling americium isotope heat source pellets, characterized in that: Includes a crushing container tank (2), a robotic arm, and a wrench for opening the lid; a sealing cover (1) is installed on the crushing container tank (2) by a threaded connection (3), the inside of the sealing cover (1) is a hemispherical structure sealing cover (5), the inside of the crushing container tank (2) is a hemispherical structure sealing cover (5), and the two form a grinding chamber; uranium-titanium alloy grinding balls are located in the grinding chamber.

2. The americium dioxide isotope heat source core crushing and recycling device according to claim 1, characterized in that: The upper part of the sealing cap (1) and the lower part of the crushing container (2) were respectively perforated.

3. The americium dioxide isotope heat source core crushing and recycling device according to claim 1, characterized in that: The cover opening wrench includes a sealing cover wrench clamping rod (6), a positioning pin (7), and a crushing tank wrench clamping rod (8).

4. The americium dioxide isotope heat source core crushing and recycling device according to claim 3, characterized in that: The robotic arm includes a vibrating arm (10), a clamping mechanism (11), and a tightening button (12); wherein the clamping mechanism (11) is located at the end of the robotic arm to fix the crushing container (2), and after the crushing container (2) is placed into the clamping mechanism (11), the tightening button (12) locks it.

5. The americium dioxide isotope heat source core crushing and recycling device according to claim 1, characterized in that: The sealing cap (1) and the crushing container (2) are both made of uranium-titanium alloy with a hardness of 450-455HV. The uranium-titanium alloy grinding ball is made of uranium-titanium alloy with a titanium content of 0.70-0.72wt%, a grinding ball hardness of 450-455HV, and a grinding ball size of 15mm-20mm.

6. A method for crushing and recycling americium dioxide isotope heat source core, using the apparatus described in claim 5, characterized in that: Includes the following steps: Step 1: Pre-sinter the americium isotope heat source core in an atmosphere of hydrogen and argon mixture; complete the first crushing process of the core. Step 2: Mechanical crushing of americium dioxide isotope heat source core blocks; weigh the core blocks crushed in Step 1 and put them into the crushing container tank (2), and at the same time put in one uranium-titanium alloy grinding ball. The sealing cap (1) is installed on the crushing container tank (2) through threaded connection (3). The crushing container tank (2) is vibrated by a robotic arm to perform grinding. Step 3: Powder mixing; Obtain the powder from Step 2, add zinc stearate as a binder to mix and agglomerate the powder produced in Step 2.

7. The method for crushing and recycling americium dioxide isotope heat source core block according to claim 6, characterized in that: In step one, a dry, flowing hydrogen-argon mixture is used, with a hydrogen content of 5wt% to 6wt%, and the gas flow rate is controlled at 2.5L / min to 6L / min. The pre-sintering temperature of the americium isotope heat source core is 800℃ to 1200℃, the holding time is 3h to 8h, and the heating and cooling rates are selected as 10℃ / min to 15℃ / min.

8. The method for crushing and recycling americium dioxide isotope heat source core block according to claim 6, characterized in that: In step two, the grinding vibration frequency is set to 40Hz to 60Hz, and the grinding time is set to 15min to 45min.

9. The method for crushing and recycling americium dioxide isotope heat source core block according to claim 6, characterized in that: In step two, after grinding is completed, sampling and analysis are performed according to the powder particle size sampling standard. If the powder particle size D50 ≤ 1 μm, the crushing process is completed; if the powder particle size D50 ≥ 1 μm, step two is repeated until the powder particle size D50 ≤ 1 μm.

10. The method for crushing and recycling americium dioxide isotope heat source core block according to claim 6, characterized in that: In step three, 0.5 wt% to 0.8 wt% zinc stearate binder is added, and the powder generated in step two is mixed and agglomerated using a roller mixer.

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