A coating cladding for fuel rods and its preparation method and application

Abstract

The present invention provides a coated cladding for fuel rods, a preparation method, and applications thereof. The coated cladding comprises a cladding tube body and a protective coating applied to the outer surface of the cladding tube body. The protective coating comprises a cemented carbide coating that completely dissolves in water and has a thickness of 0.05-0.1 mm. The present invention utilizes a cemented carbide coating that completely dissolves in water as the protective coating and further controls the coating thickness. This prevents scraping between the cladding tube and the grid springs and cams during fuel rod assembly, while ensuring smooth insertion of the fuel rod assembly into the fuel rod framework, thereby improving safety.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear fuel, and in particular relates to a coating cladding for a fuel rod, a preparation method thereof and an application thereof. Background Art

[0002] Zirconium alloys are widely used as structural materials in water-cooled nuclear power reactors, such as fuel rod cladding, due to their excellent properties. However, existing zirconium alloy fuel rod cladding exhibits significant defects and deficiencies in the event of a nuclear accident. For example, to prevent axial movement of the fuel rods during fuel assembly operation within the reactor, the grid design incorporates grid springs and rigid cams to provide a certain clamping force for the fuel rods. This clamping force reduces micro-vibration wear between the fuel rods and the grid during operation and prevents axial movement of the fuel rods during fuel assembly operation within the reactor. However, when the fuel rods are pulled into the fuel frame, the degree of scraping on different parts of the fuel rod cladding tubes varies, as different grids have different friction coefficients on different parts of the fuel rod cladding tubes. This scraping will occur to varying degrees during insertion, forming zirconium chips, some of which adhere to the cladding tube surface and some to the fuel grid elements. Some zirconium chips enter the reactor along with the fuel assemblies. Due to flow-induced vibration, there is constant friction between the zirconium chips and the fuel rod cladding tubes. Some of them cause the fuel assemblies to be damaged in the reactor, affecting the normal operation of the reactor.

[0003] To address the above problems, the nuclear industry has attempted to improve the zirconium alloy surface by coating it.

[0004] CN113035384A discloses a coated cladding for nuclear fuel rods and its manufacturing method. The coated cladding comprises: a cladding tube body; a coating layer disposed on the outer wall of the cladding tube body; and a protective layer comprising a plurality of protrusions radially disposed along the cladding tube body, each of which is disposed on the outer side of the coating layer. While this method can mitigate scratching and chipping of the cladding and coating materials, the manufacturing process is complex.

[0005] CN109208045A discloses a fuel rod cladding processing process and fuel rod cladding. The fuel rod cladding processing process includes the following steps: connecting a zirconium alloy substrate to the cathode of a power supply, connecting zirconium metal to the anode of the power supply, placing the substrate and zirconium metal in molten salt, and applying power for a predetermined time. This method uses a pure zirconium coating to protect the cladding, but the problem of zirconium chips caused by scratching still exists.

[0006] In summary, how to provide a method to prevent the fuel rod cladding from generating zirconium chips due to scratching and improve the safety of reactor operation has become an urgent problem to be solved. Summary of the Invention

[0007] In response to the problems existing in the prior art, the purpose of the present invention is to provide a coated cladding for fuel rods, a preparation method and application thereof. By selecting and designing the coating properties and controlling the coating thickness, scratches on the cladding tube body are effectively avoided while ensuring that the fuel rod assembly is smoothly pulled into the skeleton, thereby improving safety, which is of great significance.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a coating cladding for a fuel rod, the coating cladding for a fuel rod comprising a cladding tube body and a protective coating coated on an outer surface of the cladding tube body;

[0010] The protective coating comprises a cemented carbide coating that is completely soluble in an aqueous medium;

[0011] The thickness of the protective coating is 0.05-0.1 mm, such as 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm or 0.1 mm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0012] The present invention utilizes a completely aqueous cemented carbide coating as a protective coating. By further controlling the coating thickness, the coating prevents scraping between the cladding tube, the grid springs, and the cams during fuel rod assembly, while ensuring smooth insertion of the fuel rod assembly into the fuel rod framework. This, in turn, prevents the generation of zirconium chips from these scraping processes, which can accumulate within the reactor and cause damage to the fuel rods. The protective coating should be neither too thin, as it would not effectively protect the cladding tube itself, nor too thick, as it would prevent smooth insertion into the fuel rod framework.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical solution of the present invention, the raw material composition of the protective coating includes, by mass fraction: Mg 2.0-3.5wt%, such as 2.0wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3.0wt%, 3.3wt% or 3.5wt%; Cu 1.0-1.5wt%, such as 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or 1.5wt%; Ga 1.0-1.6wt%, such as 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt% or 1.6wt%; In 0.1-0.4wt%, such as 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt% or 0.4wt%; and Ni60 6-15wt%, for example, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%, etc.; the balance is Al. The selection of the above values ​​is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are also applicable.

[0015] In a second aspect, the present invention provides a method for preparing the coating cladding for a fuel rod according to the first aspect, the preparation method comprising:

[0016] (1) mixing cemented carbide coating raw materials according to a proportion and then grinding to obtain cemented carbide powder;

[0017] (2) The cemented carbide powder obtained in step (1) is sprayed onto the outer surface of the cladding tube body by a spraying process to obtain a coating cladding with a protective coating thickness of 0.05-0.1 mm.

[0018] As a preferred technical solution of the present invention, the particle size of the cemented carbide powder in step (1) is 150-300 mesh, such as 150 mesh, 200 mesh, 250 mesh or 300 mesh, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] In the present invention, the particle size of the cemented carbide powder must be controlled. If the particle size is too large, that is, the mesh size is too small, the coating particles will be too large, and the rigid convex parts will easily scrape the particles off during the rod drawing process, causing abrasion of the fuel rods. If the particle size is too small, that is, the mesh size is too large, the powder will aggregate into powder clumps and will not disperse during fluidization. When sprayed onto the fuel rod cladding tube, it will form smooth small lumps, affecting the coating appearance. During the rod drawing process, the rigid convex parts will scrape the smooth small lumps, also abrading the fuel rods and causing scratches on the fuel rods.

[0020] In a third aspect, the present invention provides an application of the fuel rod coating cladding described in the first aspect, wherein the fuel rod coating cladding is used in the field of nuclear fuel.

[0021] As a preferred technical solution of the present invention, the method for applying the coating cladding for the fuel rod comprises the following steps:

[0022] The fuel rods are assembled with the coating cladding to obtain a fuel rod assembly; the fuel rod assembly is then pulled into the fuel skeleton for cleaning and drying.

[0023] As a preferred technical solution of the present invention, the cleaning includes alkaline washing and water washing performed in sequence.

[0024] As a preferred technical solution of the present invention, the alkali solution used in the alkali washing includes sodium hydroxide solution or potassium hydroxide solution.

[0025] Preferably, the concentration of the alkali solution used in the alkali washing is 0.3-0.6wt%, such as 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the temperature of the alkali washing is 60-95°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the alkali washing time is 2-4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the number of water washings is no less than 2 times, for example 2 times, 3 times, 4 times or 5 times, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the time for each water washing is 15-30 minutes, such as 15 minutes, 20 minutes, 25 minutes or 30 minutes, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, the drying method includes using gas blowing to dry.

[0031] Preferably, the drying time is 5-10 minutes, such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention adopts a hard alloy coating that can be completely dissolved in an aqueous medium as a protective coating, and by further controlling the thickness of the coating, under the condition of ensuring that the fuel rod assembly is smoothly pulled into the framework, avoids scratching between the cladding tube and the grid spring and the rigid convex when the fuel rod is pulled, thereby avoiding zirconium chips generated by scratching or zirconium chips accumulated in the reactor and causing damage to the fuel rod. DETAILED DESCRIPTION

[0034] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0035] The following are typical but non-limiting examples of the present invention:

[0036] Example 1:

[0037] This embodiment provides a fuel rod coating cladding and a preparation method thereof. The fuel rod coating cladding includes a cladding tube body and a protective coating coated on the outer surface of the cladding tube body.

[0038] The protective coating comprises a cemented carbide coating that is completely soluble in an aqueous medium;

[0039] The thickness of the protective coating is 0.05 mm.

[0040] The raw material composition of the cemented carbide coating is shown in Table 1.

[0041] Table 1

[0042]

[0043]

[0044] The method for preparing the fuel rod coating cladding comprises:

[0045] (1) Mixing the raw materials of the cemented carbide coating according to a ratio and grinding them to obtain a 200-mesh cemented carbide powder;

[0046] (2) The cemented carbide powder obtained in step (1) is sprayed onto the outer surface of the cladding tube body by a spraying process to obtain a coating cladding with a protective coating thickness of 0.05 mm.

[0047] Example 2:

[0048] This embodiment provides a fuel rod coating cladding and a preparation method thereof. The fuel rod coating cladding includes a cladding tube body and a protective coating coated on the outer surface of the cladding tube body.

[0049] The protective coating comprises a cemented carbide coating that is completely soluble in an aqueous medium;

[0050] The thickness of the protective coating is 0.1 mm.

[0051] The raw material composition of the cemented carbide coating is shown in Table 2.

[0052] Table 2

[0053]

[0054]

[0055] The method for preparing the fuel rod coating cladding comprises:

[0056] (1) Mixing the cemented carbide coating raw materials according to a ratio and grinding them to obtain 150-mesh cemented carbide powder;

[0057] (2) The cemented carbide powder obtained in step (1) is sprayed onto the outer surface of the cladding tube body by a spraying process to obtain a coating cladding with a protective coating thickness of 0.1 mm.

[0058] Example 3:

[0059] This embodiment provides a fuel rod coating cladding and a preparation method thereof. The fuel rod coating cladding includes a cladding tube body and a protective coating coated on the outer surface of the cladding tube body.

[0060] The protective coating comprises a cemented carbide coating that is completely soluble in an aqueous medium;

[0061] The thickness of the protective coating is 0.07 mm.

[0062] The raw material composition of the cemented carbide coating is shown in Table 3.

[0063] Table 3

[0064] element Mass fraction / wt% Mg 2.0 Cu 1.0 Ga 1.0 In 0.1 Ni60 15.0 Al 80.9

[0065] The method for preparing the fuel rod coating cladding comprises:

[0066] (1) Mixing the raw materials of the cemented carbide coating according to a ratio and grinding them to obtain a 300-mesh cemented carbide powder;

[0067] (2) The cemented carbide powder obtained in step (1) is sprayed onto the outer surface of the cladding tube body by a spraying process to obtain a coating cladding with a protective coating thickness of 0.7 mm.

[0068] Example 4:

[0069] This embodiment provides a method for preparing a coating cladding for a fuel rod. The preparation method is similar to the preparation method in Example 3, with the only difference being that: step (1) grinds the cemented carbide powder to 350 mesh.

[0070] The coating cladding prepared in this embodiment forms multiple smooth small bags on the cladding tube body, which affects the appearance of the coating and meets the use standards. If the rod is forcibly assembled, the rigid convexity will scratch the smooth small bags, abrading the fuel rod and causing scratches on the fuel rod.

[0071] Example 5:

[0072] This embodiment provides a method for preparing a coating cladding for a fuel rod. The preparation method is similar to the preparation method in Example 2, with the only difference being that: step (1) grinds the cemented carbide powder to 100 mesh.

[0073] In the coating cladding prepared in this embodiment, the coating particles are too large, and the rigid convexity can easily scrape the particles off during the rod drawing process, thereby abrading the fuel rod.

[0074] Application Example 1:

[0075] This application example provides a method for applying the coating cladding for fuel rods described in Example 1, comprising:

[0076] The fuel rods were assembled with the coating cladding to obtain a fuel rod assembly. The fuel rod assembly was then pulled into the fuel skeleton and first cleaned with a 0.5 wt% sodium hydroxide solution at 60°C for 2 hours, then washed twice with water, each time for 20 minutes, and then blown dry with dry air.

[0077] Application Example 2:

[0078] This application example provides a method for applying the coating cladding for fuel rods described in Example 2, including:

[0079] The fuel rods were assembled with the coating cladding to obtain a fuel rod assembly. The fuel rod assembly was then pulled into the fuel skeleton and first cleaned with a 0.3 wt% sodium hydroxide solution at 95°C for 4 hours, then washed with water three times, each time for 15 minutes, and then blown dry with dry air.

[0080] Application Example 3:

[0081] This application example provides a method for applying the coating cladding for fuel rods described in Example 3, including:

[0082] The fuel rods were assembled with the coating cladding to obtain a fuel rod assembly. The fuel rod assembly was then pulled into the fuel skeleton and first cleaned with a 0.6 wt% sodium hydroxide solution at 70°C for 3 hours, then washed twice with water, each time for 30 minutes, and then blown dry with dry air.

[0083] After the operation of Application Examples 1-3, no zirconium chips were found on the fuel assembly after cleaning, and no scratches caused by springs and convex convexities were found on the surface of the fuel rod cladding tube, indicating that the cemented carbide coating used in the present invention played a good protective role.

[0084] While the present invention illustrates the products and detailed methods of the present invention through the foregoing embodiments, the present invention is not limited to these products and detailed methods. This does not necessarily mean that the present invention must rely on these products and detailed methods in order to be implemented. Those skilled in the art will appreciate that any improvements to the present invention, equivalent replacements for the operations of the present invention, additions of auxiliary operations, and selections of specific methods are all within the scope of protection and disclosure of the present invention.

Claims

1. A coating cladding for a fuel rod, characterized in that: The fuel rod coating cladding comprises a cladding tube body and a protective coating covering the outer surface of the cladding tube body; The protective coating comprises a cemented carbide coating that is completely soluble in an aqueous medium; The thickness of the protective coating is 0.05-0.1 mm; the raw material composition of the protective coating includes, by mass fraction, Mg 2.0-3.5 wt%, Cu 1.0-1.5 wt%, Ga 1.0-1.6 wt%, In 0.1-0.4 wt% and Ni60 6.0-15.0 wt%, with the balance being Al.

2. A method for preparing a coating cladding for a fuel rod according to claim 1, characterized in that: The preparation method comprises: (1) mixing cemented carbide coating raw materials according to a proportion and then grinding to obtain cemented carbide powder; (2) The cemented carbide powder obtained in step (1) is sprayed onto the outer surface of the cladding tube body by a spraying process to obtain a coating cladding with a protective coating thickness of 0.05-0.1 mm.

3. The method for preparing a coating cladding for a fuel rod according to claim 2, characterized in that: The particle size of the cemented carbide powder in step (1) is 150-300 mesh.

4. An application of the coating cladding for fuel rods according to claim 1, characterized in that: The fuel rod coating cladding is used in the field of nuclear fuel.

5. The use of the coating cladding for fuel rods according to claim 4, characterized in that: The method for applying the coating cladding for fuel rods comprises the following steps: The fuel rods are assembled with the coating cladding to obtain a fuel rod assembly; the fuel rod assembly is then pulled into the fuel skeleton for cleaning and drying.

6. The use of the coating cladding for fuel rods according to claim 5, characterized in that: The cleaning comprises alkali cleaning and water cleaning which are performed in sequence.

7. The use of the coating cladding for fuel rods according to claim 6, characterized in that: The alkali solution used in the alkali washing includes sodium hydroxide solution or potassium hydroxide solution.

8. The use of the coating cladding for fuel rods according to claim 7, characterized in that: The concentration of the alkali solution used in the alkali washing is 0.3-0.6 wt %.

9. The use of the coating cladding for fuel rods according to claim 6, characterized in that: The temperature of the alkali washing is 60-95°C.

10. The use of the coating cladding for fuel rods according to claim 6, characterized in that: The alkali washing time is 2-4h.

11. The use of the coating cladding for fuel rods according to claim 6, characterized in that: The number of water washings is no less than 2 times.

12. The use of the coating cladding for fuel rods according to claim 11, characterized in that: Each washing time is 15-30 minutes.

13. The use of the coating cladding for fuel rods according to claim 5, characterized in that: The drying method includes drying with gas.

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