An americium radioisotope heat source and encapsulation device, method

Abstract

A p-americium radioisotope heat source and its encapsulation device and method are disclosed, comprising a heat source core, a shielding layer, a cladding, and a composite material layer. The heat source core is located within the shielding layer, which includes a shielding barrel and a shielding cover. The shielding layer is located within the cladding, which includes a cladding end cap and a cladding tube, welded together. A nanoporous component is welded and fixed to the middle of the cladding end cap, and a butterfly spring is placed between the shielding cover and the cladding end cap. The cladding is located within the composite material layer, which includes a composite material end cap and a composite material cladding. A heat-conducting column is located at the lower end of the cladding tube, extending beyond the composite material cladding. This invention significantly improves the overall performance of the p-americium isotope heat source encapsulation through the design of a breathable cladding structure, the integration of the shielding layer, and the synergistic optimization of automated processes. By installing a vent on the cladding, helium gas generated by material decay is released, preventing internal gas accumulation that could lead to high-pressure rupture of the cladding.

Description

Technical Field

[0001] This invention relates to the field of radioactive isotope heat source technology, specifically to an americium radioactive isotope heat source and its packaging device and method. Background Technology

[0002] In deep space exploration (such as lunar bases, long-term Mars missions, and exoplanet exploration), extreme Earth environment research (such as polar regions, deep seas, and high-altitude permafrost zones), and special enclosed facilities, maintaining stable operating temperatures for critical equipment or systems is a core prerequisite for ensuring mission success and reliable equipment operation. These environments face harsh conditions such as prolonged extreme cold (below -200°C), long periods without sunlight, and drastic temperature fluctuations, significantly limiting the sustainability, reliability, energy efficiency, and system complexity of methods relying on external heat sources or conventional electric heating. Radioactive isotope heat sources generate stable heat through decay, directly providing continuous, reliable, and non-invasive basic thermal support for target equipment or systems. Americium isotope heat sources possess significant advantages such as simple structure, long lifespan (hundreds of years), maintenance-free operation, and extremely strong environmental adaptability (operating in vacuum, extreme cold, and radiation environments), making them ideal for providing essential basic thermal support for precision instruments in extreme environments, preventing them from aging or degrading due to low temperatures.

[0003] The design of americium isotope heat sources must prioritize safety. On one hand, it's crucial to ensure that radioactive materials inside the heat source do not leak or escape in the event of extreme accidents such as impacts or explosions. On the other hand, the raw materials used in americium isotope heat sources undergo alpha decay, releasing helium gas. The pressure exerted by this released helium on the cladding must be considered throughout the entire lifespan of the heat source. Therefore, the design phase of an americium isotope heat source must consider its safety throughout all stages of production, transportation, installation, use, extreme accidents, and recovery.

[0004] During the production and manufacturing stage of americium isotope heat sources, due to the special nuclear properties of americium isotopes, extremely high requirements are placed on the packaging process of americium isotope heat sources: it is necessary to achieve hermetically tight packaging in a very small space, efficient radiation shielding, ensure no leakage during long-term operation of the heat source, withstand extreme environmental tests, and minimize the risk of radiation exposure to operators in highly radioactive environments.

[0005] Existing encapsulation technologies for isotope heat sources generally employ a traditional design combining a double-layer metal cladding with an external shielding layer. While the double-layer metal cladding provides some degree of safety, it increases the manufacturing process and the likelihood of weld failure at the inner and outer cladding seams. Furthermore, the external shielding design significantly increases the volume and weight of the americium isotope heat source, which is unacceptable for some specialized applications and fails to meet the miniaturization requirements. For helium generated during the decay of americium heat source materials, a fully enclosed cladding design is often used, trapping the helium inside. However, long-term use can lead to high-pressure rupture of the cladding, posing a safety hazard. In addition, traditional cladding welding relies heavily on manually operated argon arc welding equipment. For small, thin-walled claddings with diameters less than 10mm and wall thicknesses less than 0.5mm, uneven heat input can easily cause deformation or micropore defects.

[0006] In summary, existing americium isotope packaging technologies have certain limitations in miniaturization, helium handling, lightweight shielding layers, and automated welding. An innovative device and method are needed to achieve a highly reliable, low-quality, and automated packaging solution through structural reconstruction and process innovation. Summary of the Invention

[0007] The purpose of this invention is to address the core problems in americium isotope heat source encapsulation technology, such as shielding mass redundancy, long-term helium release from the fuel, and low success rate of welding small-sized thin-walled cladding. This invention provides an americium radioactive isotope heat source and its encapsulation device and method. The invention involves designing a vented cladding structure, placing the shielding layer inside the cladding, and designing tooling to achieve automated welding. Through structural innovation and process optimization, this invention overcomes the technical bottlenecks of americium core block encapsulation, providing a systematic solution for the highly reliable, lightweight, and safe application of americium isotope heat sources.

[0008] The technical solution of the present invention is as follows: an americium radioactive isotope heat source device, comprising a heat source core, a shielding layer, a shell, and a composite material layer; wherein the heat source core is located in the shielding layer; the shielding layer includes a shielding barrel and a shielding cover; the shielding layer is located in the shell, the shell including a shell end cap and a shell tube, the shell end cap and the shell tube being welded together, and a nanoporous component being welded and fixed in the middle of the shell end cap, and a butterfly spring being placed between the shielding cover and the shell end cap; the shell is located in the composite material layer, the composite material layer including a composite material end cap and a composite material shell, and a heat-conducting column at the lower end of the shell tube, the lower end of the heat-conducting column extending out of the composite material shell.

[0009] There is a gap between the heat source core and the shielding layer; the diameter of the shielding cover is smaller than the top of the shielding barrel, thus leaving a gap at the top of the shielding layer; there is a gap between the composite material end cap and the composite material shell; so that the gas generated by the heat source core passes through the gap and the nanoporous components and is discharged outside the device.

[0010] The shielding layer is made of tungsten or lead.

[0011] The heat source pellets are americium dioxide fuel pellets.

[0012] The composite material layer is made of a composite material with low thermal conductivity and has a certain strength.

[0013] An americium radioactive isotope heat source encapsulation device includes a clamping device, a welding device, and a mandrel; the clamping device clamps the cladding tube; the mandrel presses against the cladding end cap; and the welding heat source generated by the welding device welds the cladding end cap and the cladding tube together.

[0014] The welding position is located in the welding chamber.

[0015] The clamping device is fixed by the mechanical chuck of the welding device, the top head and the flange are connected by bolts, and the flange is connected to the welding chamber by bolts.

[0016] The top head has a hollow concave structure, which allows the top head to press tightly against the end cap of the casing without touching the nanoporous components on the end cap.

[0017] A method for encapsulating an americium radioactive isotope heat source involves adjusting the position of the welding heat source and the weld at the welding point using a welding device. Once the optimal position is found, the welding chamber is filled with helium. A mechanical chuck drives the cladding end cap and cladding tube to rotate at a uniform speed, and the welding device simultaneously generates the welding heat source and begins welding.

[0018] The significant advantages of this invention are: through the synergistic optimization of the cladding ventilated structure design, the built-in cladding shielding layer, and the automated process, the overall performance of the americium isotope heat source encapsulation is significantly improved. By installing vents in the cladding, helium gas generated by material decay is released, preventing internal gas accumulation that could lead to high-pressure rupture of the cladding. The built-in tungsten shielding layer not only meets radiation shielding standards but also significantly reduces the radiation dose to personnel during assembly and welding. The self-designed tooling enables automated cladding welding, solving the quality problems of traditional manual welding and the radiation dose issues for operators during the welding process. This device and method provide a lightweight and highly reliable americium isotope heat source encapsulation solution for deep space, deep sea, and polar exploration scenarios. Attached Figure Description

[0019] Figure 1 3D disassembly diagram of the heat source; Figure 2 3D Disassembly Diagram of Heat Source Figure 3 Schematic diagram of automated welding fixture for casing; Figure 4 Schematic diagram of the cladding welding clamping device.

[0020] The markings in the diagram and their corresponding component names are as follows: 1- Composite material end cap; 2- Nanoporous component; 3- Sheathed end cap; 4- Butterfly spring; 5- Shielding cover; 6- Heat source core block; 7- Shielding barrel; 8- Sheathed tube; 9- Heat-conducting column; 10- Composite material sheath; 21-Mechanical chuck; 22-Clamping device; 23-Welding device; 24-Master head; 25-Flange; 26-Welding chamber. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The specific technical content of the present invention will now be described with reference to the accompanying drawings; like Figure 1 , 2 As shown, the americium isotope heat source of the present invention includes a heat source core 6, a shielding layer, a shell, and a composite material layer. The heat source core 6 is located within the shielding layer. The shielding layer includes a shielding barrel 7 and a shielding cover 5, and the diameter of the shielding cover 5 is smaller than the top of the shielding barrel 7, thus leaving a gap at the top of the shielding layer. The shielding layer is located in the shell, which includes a shell end cap 3 and a shell tube 8. The shell end cap 3 and the shell tube 8 are welded together. A nanoporous component 2 is welded and fixed in the middle of the shell end cap 3. The nanoporous component 2 can allow the internal gas to pass through. A butterfly spring 4 is placed between the shielding cover 5 and the shell end cap 3 to limit the displacement of the shielding cover 5 and the heat source core block 6. The shell is located in the composite material layer, which includes a composite material end cap 1 and a composite material shell 10. The lower end of the shell tube 8 has a heat-conducting column 9, and the lower end of the heat-conducting column 9 extends out of the composite material shell 10. There is a gap between the composite material end cap 1 and the composite material shell 10. Specifically, tungsten or lead is added to the shielding layer; Specifically, after the welding between the end cap 3 and the tube 8 is completed, the airtightness of the cladding and the non-destructive testing of the weld quality are carried out. After the test results meet the standards, the next step is carried out. The heat conduction table 9 is placed inside the composite material shell 10, and then the cladding is placed on the heat conduction table 9. The composite material shell 10 and the composite material end cap 1 are connected by threads to complete the assembly of the americium heat source.

[0025] The heat source pellet 6 is an americium dioxide fuel pellet. While decaying and releasing heat, it also releases helium. If helium continuously accumulates inside the casing, the internal pressure will increase, potentially causing the casing to rupture under pressure. Furthermore, the reserved gas storage space in the casing increases the consumption of heat source casing material, further increasing the mass and volume of the isotope battery, which is detrimental to overall weight and capacity reduction and improving specific power. Therefore, there is a gap between the heat source pellet 6 and the shielding layer, and the diameter of the shielding cover 5 is smaller than the top of the shielding barrel 7, thus leaving a gap at the top of the shielding layer; the nanoporous component 2 allows the internal gas to permeate out; and there is a gap between the composite end cap 1 and the composite casing 10, so the helium produced by the heat source pellet 6 can escape. Considering the radioactivity (mainly gamma rays) of americium dioxide and the redundancy of shielding weight, a shielding layer is added in the middle of the cladding. This design has the following advantages: 1. Placing the tungsten metal shielding layer between the inner and outer cladding reduces the size and weight of the shielding layer; 2. In traditional designs where the shielding layer is outside the cladding, the dose during the assembly and welding of the heat source cannot be avoided. However, with the tungsten metal shielding layer inside the cladding, the dose during the assembly and welding of the outer cladding can be greatly reduced, minimizing the dose harm to operators; 3. Furthermore, the shielding layer can conduct heat during welding, protecting the heat source core block 6. Under extreme accident conditions (such as heat source re-entry into the atmosphere and ablation, impact, fire, and deep-sea pressure), the composite material layer withstands enormous mechanical impact, high-temperature ablation, high pressure, and corrosion. The use of composite materials with low thermal conductivity provides a degree of insulation, and when combined with designed heat-conducting devices, reduces heat loss in non-target directions, achieving heat collection. The composite material itself possesses sufficient strength to provide mechanical support and protection for the internal fuel and cladding, resisting external impacts and loads.

[0026] like Figure 3 , 4As shown, an americium radioactive isotope heat source packaging device includes a clamping device 22, a welding device 23 (the heat source system for welding is not limited to tungsten inert gas welding, laser welding, electron beam welding, etc.), and a ejector pin 24; the clamping device 22 is fixed by the mechanical chuck 21 of the welding device, and the clamping device 22 clamps the cladding tube 8; the ejector pin 24 presses against the cladding end cap 3, and the welding gun fixed on the welding gun fixing device 23 welds the cladding end cap 3 and the cladding tube 8 together; Specifically, the head of the top 24 has a hollow concave structure, so that while the top 24 presses tightly against the end cap 3, it will not touch the nanoporous component 2 on the end cap 3, thus protecting the surface of the nanoporous component 2 from damage. The top head 24 and the flange 25 are connected by bolts, and the flange 25 is connected to the welding chamber 26 by bolts. All connections are sealed connections to ensure the sealing of the welding chamber 26.

[0027] During welding, the heat source (electric arc, laser beam, electron beam, etc.) generated by the welding device 23 acts on the welding point. The range of the heat source generated by the welding device 23 can be controlled by fine adjustment. After the americium isotope heat source is assembled in a helium environment, welding is completed in the welding chamber 26. Specifically, the assembled cladding tube 8 is mounted on the clamping device 22, the mechanical chuck 21 drives the cladding tube 8 to rotate at a uniform speed, and the welding device 23 simultaneously emits the welding heat source to start welding. In particular, if tungsten inert gas welding (TIG welding or WTAW welding) or laser welding is used, helium protective gas should be filled into the welding chamber 26 (to prevent helium leakage during welding, which would prevent the weld from meeting the standard during subsequent helium mass spectrometry leak detection). If electron beam welding is used, it is necessary to ensure that the fit between the cladding tube 8 and the cladding end cap 3 is an interference fit to ensure that the cladding contains a certain amount of helium. This operation is also to ensure the effectiveness of subsequent helium mass spectrometry leak detection.

[0028] The welding position is located in welding chamber 26; The processes of argon purging, rotation of the mechanical chuck 21, and start-up and shutdown of the welding device are all controlled by automated programs to ensure consistency across multiple welding processes. After welding is completed, the assembly is reverse-engineered based on the installation steps. Figure 2 The device is used to inspect the quality of welds.

[0029] 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.

[0030] 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.

[0031] 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 of other embodiments.

[0032] 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 generating americium radioactive isotopes, characterized in that: It includes a heat source core (6), a shielding layer, a shell, and a composite material layer; wherein the heat source core (6) is located in the shielding layer; the shielding layer includes a shielding barrel (7) and a shielding cover (5); the shielding layer is located in the shell, the shell includes a shell end cap (3) and a shell tube (8), the shell end cap (3) and the shell tube (8) are welded together, and a nanoporous component (2) is welded and fixed in the middle of the shell end cap (3), and a butterfly spring (4) is placed between the shielding cover (5) and the shell end cap (3); the shell is located in the composite material layer, the composite material layer includes a composite material end cap (1) and a composite material shell (10), and the lower end of the shell tube (8) has a heat-conducting column (9), the lower end of the heat-conducting column (9) extends out of the composite material shell (10).

2. The americium radioactive isotope heat source device according to claim 1, characterized in that: There is a gap between the heat source core (6) and the shielding layer; the diameter of the shielding cover (5) is smaller than the top of the shielding barrel (7), thus leaving a gap at the top of the shielding layer; there is a gap between the composite end cap (1) and the composite shell (10); so that the gas generated by the heat source core (6) passes through the gap and the nanoporous component (2) and is discharged outside the device.

3. The americium radioactive isotope heat source device according to claim 2, characterized in that: The shielding layer is made of tungsten or lead.

4. The americium radioactive isotope heat source device according to claim 3, characterized in that: The heat source pellet (6) is an americium dioxide fuel pellet.

5. The americium radioactive isotope heat source device according to claim 3, characterized in that: The composite material layer is made of a composite material with low thermal conductivity and has a certain strength.

6. A packaging device for an americium radioactive isotope heat source, used for packaging the device of claim 4, characterized in that: It includes a clamping device (22), a welding device (23), and a top head (24); the clamping device (22) clamps the shell tube (8); the top head (24) presses against the shell end cap (3), and the welding heat source generated by the welding device (23) is used to weld the shell end cap (3) and the shell tube (8).

7. The americium radioactive isotope heat source encapsulation device according to claim 6, characterized in that: The welding position is located in the welding chamber (26).

8. The americium radioactive isotope heat source encapsulation device according to claim 7, characterized in that: The clamping device (22) is fixed by the mechanical chuck (21) of the welding device, the top head (24) and the flange (25) are connected by bolts, and the flange (25) is connected to the welding chamber (26) by bolts.

9. The americium radioactive isotope heat source encapsulation device according to claim 8, characterized in that: The top (24) has a hollow concave structure, so that while the top (24) presses against the end cap (3), it will not touch the nanoporous component (2) on the end cap (3).

10. A method for encapsulating an americium radioactive isotope heat source, using the apparatus described in claim 8 to weld and encapsulate the end cap (3) and the tube (8), characterized in that: The welding device (23) adjusts the position of the welding heat source and the weld at the welding point. After finding the optimal position, the welding chamber (26) begins to be filled with helium. The mechanical chuck (21) drives the shell end cap (3) and the shell tube (8) to rotate at a constant speed. The welding device (23) generates the welding heat source simultaneously and starts welding simultaneously.

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