Aqueous coating composition and method for assembling nuclear fuel assembly by using same

Abstract

The present invention relates to an aqueous coating composition for mainly preventing physical damage to a metal surface and increasing the durability of a surface coating, and, specifically, to: an aqueous coating agent, which contains an acrylic polymer as a main component, is environmentally friendly and improves work safety; and an aqueous coating composition, which can be applied to the protection and coating of nuclear fuel rods, steel materials or similar metal materials and can maintain excellent performance while minimizing safety issues that can occur during coating, wherein the aqueous coating composition for protecting a metal surface and reducing friction comprises: 18.5-23.5 wt% of a styrene-acrylic copolymer; 67.5-72.5 wt% of water (H2O); 1.5-2.5 wt% of a polyoxyalkylene glycol; 1-2 wt% of n-propanol; and 4-6 wt% of monoethanolamine.

Description

Water-based coating composition and method for assembling nuclear fuel assemblies using the same

[0001] The present invention relates primarily to an aqueous coating composition that prevents physical damage to metal surfaces and increases the durability of surface coatings. More specifically, it relates to an aqueous coating agent comprising an acrylic polymer as a main component that is environmentally friendly and improves work safety. It is applicable to the protection and coating of nuclear fuel rods, steel materials, or similar metal materials, and relates to an aqueous coating composition capable of maintaining excellent performance while minimizing safety issues that may occur during the coating process.

[0002] The coating of metal surfaces is intended to improve durability and corrosion resistance, but conventional organic solvent-based coating agents can cause environmental pollution and pose risks to workers' health due to the release of volatile organic compounds (VOCs) during the coating process. Accordingly, environmentally friendly water-soluble coating agents are being proposed as an alternative.

[0003] Conventional technology includes the following:

[0004] Coating compositions containing solid lubricants are widely used to reduce friction and improve durability.

[0005] Water-soluble urethane and acrylic-based compositions have been developed as substitutes for existing organic solvent-based coatings, and this technology ensures physical stability and environmental resistance.

[0006] Conventional core-shell structure-based coatings have evolved into a technology that improves particle dispersion stability while simultaneously providing thermal stability.

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] (Patent Document 1) Korean Patent Publication No. 10-2024-0026343 (Date of Publication: Feb. 28, 2024)

[0010] The present invention aims to overcome the volatile organic compound emission problems and safety limitations of existing organic solvent-based coating agents by providing an aqueous coating composition that offers excellent protection to metal surfaces while being easy to remove.

[0011] The aqueous coating composition of the present invention for achieving these purposes comprises 18.5-23.5 wt% of styrene-acrylic copolymer; 67.5-72.5 wt% of water (H2O); 1.5-2.5 wt% of polyoxyalkylene glycol; 1-2 wt% of n-propanol; and 4-6 wt% of monoethanolamine.

[0012] Next, a method for assembling a skeleton and a fuel rod constituting a nuclear fuel assembly using the above-described aqueous coating composition is characterized by applying the aqueous coating composition to the surface of the fuel rod to form a film, then assembling the nuclear fuel assembly by inserting the fuel rod into the skeleton, and then washing off the aqueous coating composition.

[0013] The aqueous coating composition of the present invention comprises 18.5-23.5 wt% of styrene-acrylic copolymer; 67.5-72.5 wt% of water (H2O); 1.5-2.5 wt% of polyoxyalkylene glycol; 1-2 wt% of n-propanol; and 4-6 wt% of monoethanolamine. By assembling a framework and fuel rods constituting a nuclear fuel assembly using the above-described aqueous coating composition, it is possible to maintain performance equivalent to that of existing organic solvent-based coating agents, improve safety and environmental friendliness, increase worker safety, ensure process efficiency, and have the effect of facilitating easy removal of the coating after the assembly process.

[0014] FIG. 1 is a drawing showing a test apparatus for evaluating an aqueous coating composition according to an embodiment of the present invention.

[0015] FIG. 2 is a diagram showing the surface scratch depth measurement locations of a fuel rod for evaluating an aqueous coating composition according to an embodiment of the present invention.

[0016] Figure 3 is a photograph showing the results of the corrosion effect on a fuel rod by the aqueous coating composition of the present invention.

[0017] Figure 4 is a photograph showing the results of testing the ease of cleaning of the aqueous coating composition of the present invention.

[0018] The specific structural or functional descriptions presented in the embodiments of the present invention are merely illustrative for the purpose of explaining embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms. Furthermore, it should not be interpreted as being limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention.

[0019] Specific embodiments of the present invention will be described below.

[0020] The aqueous coating composition of the present invention is characterized by comprising 18.5-23.5 wt% of styrene-acrylic copolymer, 67.5-72.5 wt% of water (H2O), 1.5-2.5 wt% of polyoxyalkylene glycol, 1-2 wt% of n-propanol; and 4-6 wt% of monoethanolamine.

[0021] In particular, this aqueous coating composition can be coated on the surface of the fuel rod during the manufacturing process of the fuel rod for a light water reactor, thereby minimizing surface damage (scratches) that may occur during the manufacturing process of the fuel rod.

[0022] FIG. 1 is a drawing showing a test apparatus for evaluating an aqueous coating composition according to an embodiment of the present invention. By performing a fuel rod loading test on a HIPER 16-type frame (20), the load generated during loading, the depth of scratches on the surface of the fuel rod, and the loading force were measured, thereby comparing and evaluating the water-soluble coating agent of the present invention with the conventional lacquer coating agent and dry friction (no coating agent applied).

[0023] Specifically, referring to FIG. 1, after combining the fuel rod (10) with the charging rod and gripper of the charging device, it is withdrawn by completely passing through the inner cell of the support grid constituting the skeletal body (20), and a test is performed under charging conditions identical to mass production conditions.

[0024] FIG. 2 is a diagram showing the surface scratch depth measurement locations of a fuel rod for evaluating an aqueous coating composition according to an embodiment of the present invention, and the surface scratch was evaluated at four locations around the fuel rod where substantial contact is made with the support grid.

[0025] [Table 1] below shows data on the results of measuring scratches on the surface of five specimens (fuel rods) by applying a conventional coating agent (lacquer solution coating agent).

[0026]

[0027] Table 2 below shows the results of measuring scratches on the surface of four specimens (fuel rods) by applying the coating agent of the present invention.

[0028]

[0029] The following [Table 3] shows the results of scratch measurements on the surfaces of five specimens (fuel rods) under dry friction (no coating applied) conditions.

[0030]

[0031] The following [Table 4] is data showing the measurement results of each charging load (unit N) under dry friction conditions and coating agents of the present invention and the prior art (lacquer solution coating agent).

[0032]

[0033] Figure 3 is a photograph showing the results of the corrosion effect of the aqueous coating composition of the present invention on a fuel rod. After coating the fuel rod specimen with the aqueous coating composition of the present invention, it was corroded in water at a high temperature for a certain period of time according to the corrosion test procedure, and the test results were confirmed to be satisfactory (passed).

[0034] Next, the physical properties of the film of the aqueous coating composition of the present invention were tested. A film of the prior art (lacquer solution coating agent) was formed on a flat specimen of the same material as a fuel rod and dried, and then pencil hardness, adhesion, thickness, and ease of washing with water were tested. The following [Table 5] is the data showing the test results.

[0035]

[0036] Figure 4 is a photograph showing the results of testing the washability of the aqueous coating composition of the present invention. The aqueous coating composition of the present invention was applied to three plate-shaped specimens and dried, after which a portion was washed with water. It can be seen that the coating film was cleanly washed off in all specimens. In addition, it was confirmed that when a fuel rod cladding tube with a coating film formed on its surface was immersed in water, the coating film dissociated and was removed.

[0037] In addition, the aqueous coating composition of the present invention was classified as a non-hazardous material in a hazardous material classification test conducted by the Korea Fire Industry Technology Institute.

[0038] The present invention described above is not limited by the aforementioned embodiments and attached drawings, and it will be obvious to those skilled in the art that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention.

[0039] [Explanation of the symbol]

[0040] 10 : Fuel rod 20 : Skeleton

Claims

1. A water-based coating composition for protecting a metal surface and reducing friction, Styrene-acrylic copolymer 18.5-23.5 wt%; Water (H2O) 67.5-72.5 wt%; Polyoxyalkylene Glycol 1.5-2.5 wt%; 1-2 wt% n-propanol; and An aqueous coating composition containing 4-6 weight% of monoethanolamine.

2. A method for assembling a nuclear fuel assembly composed of a skeleton and fuel rods constituting the nuclear fuel assembly using the aqueous coating composition of claim 1, A method for assembling a nuclear fuel assembly characterized by applying the aqueous coating composition to the surface of the fuel rod to form a film, then inserting the fuel rod into the skeletal body to assemble the nuclear fuel assembly, and then washing off the aqueous coating composition.

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