A uranium-plutonium oxide fuel continuous sintering furnace body

Abstract

A kind of continuous sintering furnace body of uranium-plutonium oxide fuel, including furnace shell, basket, furnace body, furnace shell is located outside, and between basket is protective atmosphere;Furnace body is located inside basket, and it includes insulating layer, hearth, and molybdenum boat is located in hearth;There are two parallel guide rails in the inside of furnace shell, and there are two rollers on the bottom of basket, and basket is placed into furnace shell by two side rollers, and basket is moved in and out of furnace shell by roller;There are basket holes and thermocouple through holes on basket, and thermocouple is inserted into furnace body through thermocouple through hole.The high temperature structure mechanics of the present application is good in stability, and there is no temperature fluctuation and damage, destruction phenomenon, and the rapid integrated replacement of furnace brick in high radiation environment can be realized.Effective reduction of personnel exposure dose, saving labor cost.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel sintering technology, specifically to a furnace body for a continuous sintering furnace of uranium plutonium oxide fuel. Background Technology

[0002] In the nuclear fuel pellet preparation process, the continuous sintering furnace is the core equipment for ensuring production line capacity and product stability, and it is also the most complex piece of equipment. For the first time in China, uranium-plutonium oxide fuel is produced using a continuous sintering furnace, with a sintering temperature reaching 1780℃. Plutonium oxide fuel has extremely high radioactivity and a long half-life. The harsh environment of high radiation and high temperature makes the continuous sintering furnace for uranium-plutonium oxide fuel complex in structure and subject to extremely high safety requirements. Under non-radioactive conditions, the furnace body can be designed as an open type. To consider the furnace's insulation and high-temperature stability, a U-shaped structure is mainly adopted. Furthermore, the continuous sintering furnace is large in volume, allowing furnace bricks to be directly and manually stacked into the furnace body. Replacement of furnace bricks or maintenance can be carried out in the open space.

[0003] The continuous sintering furnace for uranium-plutonium oxide fuel operates in a harsh environment with high radiation and high temperature, significantly different from other continuous sintering furnaces. Specifically: 1) To meet maintenance requirements under high radiation, the overall volume of the sintering furnace must be minimized; 2) Replacing furnace bricks under high radiation requires minimizing the volume and weight of the furnace bricks, and necessitates replacing the entire furnace brick, while simultaneously ensuring uniform temperature field at high temperatures, furnace safety, and high-temperature stability; 3) These requirements for furnace bricks in the continuous sintering furnace for uranium-plutonium oxide fuel differ significantly from those in other continuous sintering furnaces. Therefore, the structure, dimensions, brick replacement method, and high-temperature performance of the furnace body in the continuous sintering furnace for uranium-plutonium oxide fuel are significantly different from other continuous sintering furnaces. This invention patent is the first in China to propose a furnace body layout structure for a continuous sintering furnace for uranium-plutonium oxide fuel. It includes the furnace body structure and performance of a pre-sintering zone, sintering zone, and cooling zone. The furnace bricks have a cylindrical structure, comprising a multi-layered structure including the furnace chamber, insulation layer, brick basket, protective gas gap, furnace shell structure, molybdenum boat, and heating wires, as well as the connection structure of each component. The furnace structure meets the process requirements of a sintering temperature of 1780℃ and uniformity of ±2℃ under high radiation conditions. It meets the safety performance requirements of the sintering furnace, with a brick basket temperature <500℃ and a furnace shell temperature <60℃. The high-temperature structural mechanical stability is good, with no temperature fluctuations, breakage, or damage observed. It facilitates the transfer of waste bricks and replacement with new furnace bricks under high radiation conditions, and enables equipment inspection and maintenance operations under high radiation environments. The overall structure of the brick basket is cylindrical with a tracked trolley at the bottom, and it can withstand temperatures up to 1200℃. This allows for rapid replacement of furnace bricks under high radiation conditions. It can support a furnace brick weight of 3-5 tons. It exhibits good high-temperature mechanical stability, meeting the high-temperature stability requirements of furnace bricks during continuous sintering furnace operation. Summary of the Invention

[0004] The purpose of this invention is to provide a continuous sintering furnace body for uranium-plutonium oxide fuel, meeting the requirements of a sintering temperature of 1780℃ and uniformity of ±2℃ under high radiation conditions. It also meets the safety performance requirements of the sintering furnace, effectively reducing radiation exposure to personnel and saving labor costs.

[0005] The technical solution of the present invention is as follows: A continuous sintering furnace body for uranium-plutonium oxide fuel includes a furnace shell, a wire basket, and a furnace body. The furnace shell is located on the outside, and a protective atmosphere is formed between it and the wire basket. The furnace body is located inside the wire basket and includes a heat insulation layer and a furnace chamber, while a molybdenum boat is located in the furnace chamber.

[0006] There are two parallel guide rails inside the furnace shell, and rollers on both sides of the bottom of the mesh basket. The mesh basket sits in the furnace shell through the rollers on both sides, and the mesh basket moves out and into the furnace shell through the rollers.

[0007] The basket has basket holes and thermocouple penetration holes, through which the thermocouple is inserted into the furnace body.

[0008] The basket contains multiple fixing strips inside.

[0009] There are clips on the bottom of the outer side of the basket, which hold the basket and the furnace body inside the furnace shell.

[0010] There are heating wires inside the furnace.

[0011] It also includes a cooling circulation system, which is located inside the furnace shell.

[0012] The furnace shell is made of 316L stainless steel, and the wire mesh basket is made of 310S stainless steel, both of which are cylindrical.

[0013] The protective atmosphere uses a hydrogen-argon mixture, and the mixture is constantly flowing.

[0014] Both the insulation layer and the furnace chamber are made of alumina bricks, and the density of the alumina bricks used in the furnace chamber is greater than that of the alumina bricks used in the insulation layer. Furthermore, the alumina bricks in the insulation layer and the furnace chamber are stacked without binder, and expansion joints are left between the bricks.

[0015] The furnace bricks used at the top of the furnace have a chelated butt joint structure.

[0016] The significant advantages of this invention are:

[0017] (1) Sintering temperature of 1780℃ under high radiation environment, uniformity ±2℃. Meets the safety performance requirements of sintering furnace, brick mesh temperature <500℃. Furnace shell temperature <60℃.

[0018] (2) The high-temperature structure has good mechanical stability and no temperature fluctuations, damage or destruction have occurred.

[0019] (3) The overall load-bearing capacity of the basket is 3-5 tons.

[0020] (4) The wire mesh basket is resistant to 1200℃. It has good high-temperature mechanical stability, which meets the high-temperature stability requirements of the furnace bricks during the continuous sintering furnace operation.

[0021] (5) The modular design of the furnace brick system enables rapid and integrated replacement of furnace bricks in high-radiation environments. This effectively reduces the radiation dose to personnel and saves labor costs. Attached Figure Description

[0022] Figure 1 Schematic diagram of the two-dimensional layout of the sintering furnace body structure;

[0023] Figure 2 Schematic diagram of the three-dimensional layout of the sintering furnace body;

[0024] Figure 3a Net basket illustration;

[0025] Figure 3b Net basket illustration;

[0026] Figure 4 Two-dimensional structure diagram of a net basket;

[0027] Figure 5 Roller structure diagram;

[0028] Figure 6a Furnace structure diagram;

[0029] Figure 6b Chelated structure of furnace top bricks;

[0030] Figure 6c Structural diagram of the furnace chamber built on the insulation layer;

[0031] Figure 6d Diagram of the furnace lining and insulation layer stacking structure;

[0032] Figure 6e Plan view of the furnace and the insulation layer stacking structure;

[0033] Figure 7 The distribution structure of the heating wires within the furnace chamber;

[0034] Figure 8 Schematic diagram of molybdenum boat

[0035] In the diagram: 1-furnace shell; 2-protective atmosphere; 3-mesh basket; 4-insulation layer; 5-furnace chamber; 6-heating wire; 7-molybdenum boat;

[0036] 11—Wire mesh basket hole; 12—Thermocouple through hole; 13—Fixing strip; 14—Roller; 15—Snap fastener Detailed Implementation

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The specific technical content of the present invention will now be described with reference to the accompanying drawings;

[0041] like Figure 1 As shown, a continuous sintering furnace body for uranium-plutonium oxide fuel includes a furnace shell 1, a wire basket 3, and a furnace body. The furnace shell 1 is located on the outside, and a protective atmosphere 2 is formed between it and the wire basket 3. The furnace body includes an insulation layer 4 and a furnace chamber 5, while a molybdenum boat 7 is located in the furnace chamber 5.

[0042] Specifically, furnace shell 1 is made of 316L stainless steel and is integrally formed. The cylindrical furnace shell structure reduces the number of welds, improving its sealing performance. This is a core indicator for continuous sintering furnaces, requiring extremely high sealing performance for furnace shell 1. The cylindrical furnace body is used instead of a U-shaped one to minimize weight in a high-radiation environment. The cylindrical furnace body is significantly lighter than the U-shaped one, facilitating the inspection, maintenance, and replacement of furnace bricks in a high-radiation environment.

[0043] The protective atmosphere 2 is 20mm thick and consists of a hydrogen-argon mixture. Due to the high radiation dose in the continuous sintering furnace using uranium-plutonium oxide fuel, maintenance and replacement of furnace bricks are required under high radiation conditions, limiting the overall size of the continuous sintering furnace compared to non-radioactive environments. The thermal conductivity of the inert gas used in the sintering furnace is 0.02-0.04 W / m·K. Since both the insulation layer 4 and the furnace chamber 5 use alumina bricks, whose thermal conductivity is 1-1.5 W / m·K, the inert gas has a much lower thermal conductivity than alumina bricks, resulting in better insulation. At the same temperature, the diameter of the continuous sintering furnace using the inert gas layer is approximately 1m, meeting the requirements for miniaturization of the furnace brick system in high-radiation environments. The furnace chamber 5 temperature is 1850℃, the basket 3 temperature is <500℃, and the furnace shell 1 temperature is <60℃. There is a significant temperature gradient between the basket 3 and the furnace shell 1. If an insulation layer were used, the furnace size would increase significantly. Taking into account the maintenance and repair of the sintering furnace under high radiation conditions, as well as the furnace temperature requirements, a protective atmosphere 2 is used between the mesh basket 3 and the furnace shell 1. Due to the heat insulation properties of the protective atmosphere 2, the temperature of the furnace shell 1 can well meet the safety requirements. Excess heat is released through cooling circulating water. The temperature of the furnace shell 1 remains below 60℃ throughout the heating process. The protective atmosphere 2 is a continuously flowing gas, forming a second safety barrier for the furnace body. In the event of abnormal operating conditions, such as power outages or water outages, excess heat is carried away by the flowing gas in the protective atmosphere 2, ensuring that the furnace temperature does not exceed the limit temperature. In addition, increasing the protective atmosphere 2 increases the gas surface area, which is more conducive to ensuring the safety of the sintering furnace temperature.

[0044] As shown in Figure 3-5, the mesh basket 3 has a 12mm aperture and a 3mm thickness for better heat dissipation. Inside the mesh basket 3 are multiple 8mm thick fixing strips 13 to improve the overall load-bearing capacity. The mesh basket 3 can support 3-5 tons of furnace bricks. The actual weight of the furnace bricks is 1-2.5 tons. This meets the stability requirements of the furnace bricks under high-temperature conditions.

[0045] The mesh basket 3 is entirely made of 310S stainless steel, capable of withstanding temperatures up to 1200℃. Thermal calculations show that when the furnace body reaches an operating temperature of 1750℃, the temperature of the outermost insulation layer 4 remains below 500℃. The mesh basket 3 meets both temperature requirements and furnace safety requirements. The mesh basket 3 has mesh basket holes 11 for heat dissipation, reducing its weight, improving heat dissipation efficiency, minimizing deformation, and reducing heat load, thus extending its service life. Three thermocouple through holes 12 are located on the side of the mesh basket 3, ensuring smooth insertion of thermocouples into the furnace cavity for real-time monitoring of furnace temperature distribution. The bottom of the mesh basket 3 has five rollers 14 on each side, totaling ten rollers. The rollers 14 are secured with multi-layer bolts to meet overall load-bearing requirements. The roller screws allow for millimeter-level height adjustment to address inconsistent track wear between the pre-sintering and sintering zones. The mesh basket 3 also allows for overall expansion space.

[0046] The mesh basket 3 enables modular replacement of the furnace bricks, as the high-radiation environment prevents the stacking and replacement of bricks as in non-radioactive environments. The mesh basket 3 facilitates modular brick replacement in this high-radiation environment. Two parallel guide rails exist inside the furnace shell 1, and the mesh basket 3 is seated inside the shell 1 via five rollers on each side. The entire brick system weighs 3-5 tons; the design of the guide rails and rollers significantly reduces the load on the brick system when it enters and exits the furnace.

[0047] The furnace bricks are stacked inside the wire mesh basket 3. They are stacked without adhesive, and their stability is ensured by the geometric structure between the bricks. The basket consists of an insulation layer 4 and a furnace chamber 5, as shown in Figure 6. Expansion joints are left between the bricks. The expansion joint between each brick is 1-2mm to ensure the integrity of the bricks after expansion at high temperatures. The furnace chamber has a rhomboid structure; compared to a U-shaped structure, the rhomboid structure provides a tighter bond and a more stable connection.

[0048] Figure 6b This refers to the chelated joint structure of the furnace bricks used in furnace chamber 5. This ensures the stability of furnace chamber 5.

[0049] Figure 6d The diagram shows the entire furnace body. The orange part in the middle is the furnace chamber 5, and the rest of the gray part is the insulation layer 4.

[0050] Figure 7 This is a structural diagram of heating wire 6, which is arranged inside the furnace chamber 5. The heating wire is made of tungsten-rhenium alloy to ensure the heating temperature of the sintering furnace and the temperature field uniformity within ±1℃. The arrangement diagram is shown below. Figure 7 As shown.

[0051] Figure 8 This is a schematic diagram of molybdenum boat 7, which is located inside furnace 5. Molybdenum boat 7 is a container for loading nuclear fuel, carrying the nuclear fuel and subjecting it to a low-temperature-high-temperature sintering curve.

[0052] This invention patent is the first in China's nuclear field to propose a furnace brick basket structure, which is crucial because the sintering furnace is a high-radiation environment. During furnace brick replacement, 10 rollers allow the basket containing the furnace bricks to easily and smoothly enter the sintering furnace. Two latches 15 at the bottom of the basket 3 secure the basket 3 and the furnace body inside the furnace shell 1, ensuring stability. This completes the brick loading process. Similarly, waste furnace bricks can be easily pulled out of the sintering furnace using the basket structure for subsequent nuclear waste disposal. The brick replacement time is less than 2 hours.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 furnace body for a continuous sintering furnace using uranium-plutonium oxide fuel, characterized in that: It includes a furnace shell (1), a wire basket (3), and a furnace body. The furnace shell (1) is located on the outside, and there is a protective atmosphere (2) between it and the wire basket (3). The furnace body is located inside the wire basket (3), and it includes an insulation layer (4) and a furnace chamber (5), while the molybdenum boat (7) is located in the furnace chamber (5). There are two parallel guide rails inside the furnace shell (1), and rollers (14) on both sides of the bottom of the mesh basket (3). The mesh basket (3) sits in the furnace shell (1) through the rollers (14) on both sides, and the mesh basket (3) moves out and into the furnace shell (1) through the rollers (14).

2. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 1, characterized in that: The basket (3) has a basket hole (11) and a thermocouple through hole (12), through which the thermocouple is inserted into the furnace body.

3. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 2, characterized in that: The basket (3) contains multiple fixing strips (13).

4. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 3, characterized in that: The bottom of the outer side of the basket (3) has a buckle (15) that holds the basket (3) and the furnace body inside the furnace shell (1).

5. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 4, characterized in that: The furnace chamber (5) contains heating wires (6).

6. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 5, characterized in that: It also includes a cooling circulation system, which is located inside the furnace shell (1).

7. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 6, characterized in that: The furnace shell (1) is made of 316L stainless steel, and the wire mesh basket (3) is made of 310S stainless steel, both of which are cylindrical.

8. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 6, characterized in that: The protective atmosphere (2) uses a hydrogen-argon mixture, and the mixture flows continuously.

9. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 6, characterized in that: Both the insulation layer (4) and the furnace chamber (5) are made of alumina bricks. The density of the alumina bricks used in the furnace chamber (5) is greater than that of the alumina bricks in the insulation layer (4). The alumina bricks in the insulation layer (4) and the furnace chamber (5) are stacked without binder, and expansion joints are left between the bricks.

10. The furnace body of a continuous sintering furnace for uranium-plutonium oxide fuel according to claim 6, characterized in that: The furnace bricks used at the top of the furnace (5) have a chelated butt joint structure.

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