Method for manufacturing zirconium alloy cladding tube

Abstract

One embodiment provides a method for manufacturing a zirconium alloy cladding tube that suppresses changes in the microstructure of a zirconium alloy base material caused by process heat generated during a metal coating film deposition process using arc ion plating (AIP), improves adhesion between the coating layer and the base material, enables lamination of dense coating layers, and does not change the performance of the base material. The manufacturing method for a zirconium alloy cladding tube according to one embodiment includes a cladding tube preparation step for preparing a cladding tube made of a zirconium alloy material, a target preparation step, a vacuum heating step, an etching step, and a coating step, and controls changes in the microstructure to prevent recrystallization of the zirconium alloy on the surface of the cladding tube by controlling target conditions, preheating conditions, current conditions, and voltage conditions.

Description

[Technical Field]

[0001] A method for manufacturing a zirconium alloy cladding tube is provided. [Background technology]

[0002] Accident-tolerant fuel (ATF) cladding has been developed with the aim of preventing hydrogen explosions by reducing the amount of hydrogen generated in high-temperature steam environments during nuclear power plant accidents. ATF cladding must meet various performance requirements in extreme environments, such as corrosion resistance, creep resistance, stability under irradiation deformation, and storage and disposal requirements, while focusing on improving oxidation resistance during accidents. However, considering economic viability and rapid commercialization, accident-tolerant cladding is currently being developed worldwide by coating the surface of existing zirconium (Zr) alloy cladding with an oxidation-resistant material.

[0003] To this end, the Korea Atomic Energy Research Institute is researching two methods: a surface treatment method using a 3D printing process on the surface of existing Zr alloy cladding tubes, and a coating method using Arc Ion Plating (AIP) technology. In particular, the AIP method has been selected as a method for improving oxidation resistance by coating Cr or CrAl alloy without damaging the base material of commercial zirconium alloy cladding tubes, and commercialization of the technology is currently under development.

[0004] However, the AIP process, which applies a coating layer to a zirconium alloy cladding tube, has the advantage of not causing any changes to the base material, but it has been found to have the problem of the microstructure of the zirconium alloy cladding tube changing due to the heat generated during the process.When the microstructure of the zirconium alloy cladding tube changes due to the heat generated during the process, physical properties such as mechanical strength decrease, which poses a problem to the structural function of the nuclear fuel cladding tube.

[0005] As a related prior art document, Korean Patent No. 2,161,584 discloses "Metal coating film having excellent high temperature oxidation resistance and corrosion resistance and manufacturing method thereof." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent No. 2,161,584 Summary of the Invention [Problem to be solved by the invention]

[0007] One embodiment provides a method for manufacturing a zirconium alloy cladding tube that can suppress changes in the microstructure of a zirconium alloy base material due to process heat generated during a metal coating film deposition process using arc ion plating (AIP), improves adhesion between the coating layer and the base material, and enables the deposition of a dense coating layer without changing the performance of the base material.

[0008] In addition to the above-mentioned objects, embodiments of the present invention can be used to achieve other objects not specifically mentioned. [Means for solving the problem]

[0009] A method for manufacturing a zirconium alloy cladding tube according to one embodiment includes: a cladding tube preparation step of preparing a cladding tube made of a zirconium alloy material; a target preparation step of preparing a target under predetermined target conditions, the target including a coating material to be coated on the surface of the cladding tube; a vacuum heating step of placing the cladding tube and the target in a chamber and vacuum-heating the target under predetermined preheating conditions for an initial vacuum; a particle evaporation step of supplying a current to the surface of the target under predetermined current conditions to generate an arc and evaporate particles of the coating material; and a coating step of supplying a bias voltage under predetermined voltage conditions to uniformly coat the ionized coating material on the surface of the cladding tube, wherein the target conditions, preheating conditions, current conditions, and voltage conditions are adjusted to control a change in microstructure so as to prevent recrystallization of the zirconium alloy on the surface of the cladding tube. [Effects of the Invention]

[0010] According to one embodiment, when a zirconium alloy cladding tube is manufactured using a coating technique that employs arc ion plating of a zirconium alloy, the adhesion between the coating layer and the base material can be improved, allowing for the deposition of a dense, high-quality coating layer, and the oxidation resistance can be improved, thereby preventing the microstructure of the zirconium alloy cladding tube from being changed by process heat. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to an embodiment; [Figure 2] 10 is a diagram schematically illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to a comparative example. FIG. [Figure 3] 1 is a diagram illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to an embodiment; [Figure 4] FIG. 10 is a diagram comparing the changes in the microstructure of cladding tubes manufactured using the target setting conditions according to the first experimental example. [Figure 5] FIG. 10 is a diagram comparing the changes in the microstructure of cladding tubes manufactured using the target setting conditions according to the second experimental example. [Figure 6] FIG. 10 is a diagram showing the change in the microstructure of the cladding tube manufactured using the target setting conditions according to the third experimental example. [Figure 7] FIG. 10 is a diagram showing the change in the microstructure of the cladding tube manufactured using the target setting conditions according to the fourth experimental example. DETAILED DESCRIPTION OF THE INVENTION

[0012] With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention can be realized in various different forms and is not limited to the embodiments described herein. In the drawings, parts unnecessary for the explanation of the present invention are omitted to clearly explain the present invention, and the same reference numerals are used throughout the specification for the same or similar components. Furthermore, in the case of well-known publicly known technologies, detailed descriptions thereof will be omitted.

[0013] Throughout the specification, when a part "comprises" a certain element, this means that it can further include other elements, but not excluding other elements, unless otherwise specified.

[0014] Hereinafter, the method for manufacturing a zirconium alloy cladding tube will be described in detail with reference to the drawings.

[0015] Figure 1 is a diagram schematically illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to one embodiment, and Figure 2 is a diagram schematically illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to a comparative example. A method for manufacturing a zirconium alloy cladding tube according to one embodiment will be described with reference to Figures 1 and 2. The method for manufacturing a zirconium alloy cladding tube according to one embodiment includes a cladding tube preparation step, a target preparation step, a vacuum heating step, an etching (cleaning) step, a particle evaporation step, and a coating step. By adjusting the preset target conditions, preheating conditions, current conditions, and voltage conditions, it is possible to easily control changes in the microstructure to prevent recrystallization of the zirconium alloy on the surface of the cladding tube 20.

[0016] The cladding tube preparation stage is a stage of preparing a cladding tube 20 made of a zirconium alloy material. Here, the cladding tube 20 is referred to as a zirconium alloy cladding tube or an accident-resistant nuclear fuel cladding tube.

[0017] The target preparation step includes preparing the target 10 under preset target conditions, including a coating material to be coated on the surface of the cladding tube 20. Here, the coating material may include an oxidation-resistant material. The oxidation-resistant material may include one or more of Cr and Cr alloys. The size of the target 10 can be set to 3 inches.

[0018] The vacuum heating step is a step of vacuum heating under pre-set pre-heating conditions for initial vacuum after placing the cladding tube 20 and the target 10 in the chamber 100. Here, the pre-heating temperature under the pre-set pre-heating conditions can be set to 350°C or less.

[0019] In the etching (cleaning) step, a preset current and bias voltage are supplied to the surface of the target 10 to generate an arc, evaporating particles of the coating material and removing foreign matter from the surface. In the etching step, the current supplied to the target 10 is 80 A or less, the bias voltage is 200 V to 600 V, and the time can be set to within 20 minutes, thereby minimizing changes to the microstructure of the target 10.

[0020] The particle evaporation step is a step in which a current is supplied to the surface of the target 10 under preset current conditions to generate an arc and evaporate particles of the coating material. During the particle evaporation step, the coating material particles evaporate, and a cleaning function can also be performed to remove foreign matter from the surface of the cladding tube. Here, under the preset current conditions, the current supplied to the target 10 can be set to 80 A or less, the bias voltage can be set to a range of 200 to 600 V, and the time can be set to within 20 minutes. Even if the bias voltage is high during the particle evaporation step, no change in the microstructure (recrystallization) occurs in the zirconium alloy cladding tube 20 within 20 minutes.

[0021] The coating step involves applying a bias voltage under preset voltage conditions to uniformly coat the surface of the cladding tube 20 with ionized coating material in order to increase the deposition rate of evaporated particles. Here, under the preset voltage conditions, the current applied to the target 10 is set to 80 A or less, and the bias voltage can be set to less than 100 V. A higher bias voltage can cause etching and reduce deposition efficiency. Furthermore, when performing vacuum heating at a preheating temperature of 350°C or less, a decrease in high-temperature oxidation resistance and peeling at the Cr-Al thin film interface, which can occur with a bias voltage of less than 100 V, can be prevented. To achieve a 10-micron-thick Cr or Cr alloy coating layer, the coating time can be three hours or more. For example, to uniformly coat a 10-micron-thick Cr or Cr alloy layer on a zirconium alloy, the coating time can be approximately 10 hours. Such a long coating time can reduce changes in the target microstructure by causing recrystallization of the zirconium alloy matrix.

[0022] 1 and 2 show examples of microstructural changes in zirconium alloy cladding tubes due to the arc ion plating (AIP) process. For example, FIGS. 1 and 2 compare the recrystallization phenomenon in the cladding tube 20 depending on the difference in current and bias voltage supplied to a 3-inch target. As in the example of FIG. 1, when a 3-inch target 10 is supplied with a current of 80 A and a bias voltage of less than 100 V, no microstructural changes occur on the surface of the cladding tube 20. Reference numeral 12 indicates an evaporation area in the 3-inch target 10.

[0023] In contrast, when a 3-inch target 10 is used, the current is 90 A, and the bias voltage is 120 V or more as in the comparative example of FIG. 2, a change in the microstructure occurs on the surface of the cladding tube 20.

[0024] As shown in the comparative example of Figure 2, when a 3-inch target 10 is used, a current of 90 A is supplied, and a bias voltage of 120 V or more is supplied, a microstructural change occurs on the surface of the cladding tube 20. Therefore, it is necessary to adjust the size of the target 10 and the current formation area due to the magnetic field to confirm the recrystallization phenomenon caused by the microstructural change on the surface of the cladding tube 20. Reference numeral 20a denotes the microstructural change area that occurs on the surface of the cladding tube 20.

[0025] FIG. 3 is a schematic diagram illustrating a process for manufacturing a zirconium alloy cladding tube using target setting conditions according to one embodiment. Referring to FIG. 3, when the current and bias voltage supplied to the target 10 are set to 90 A and 120 V, respectively, the size of the target 10 increases. For example, the target size can be set to 5 inches, and such a 5-inch target can be rotated. Reference numeral 10a denotes a 5-inch target. Reference numeral 12a denotes multiple evaporation portions on the 5-inch target 10a. Referring to FIG. 3, due to the rotation of the target, the arc appears in a donut shape rather than a single point shape.

[0026] For example, if the current and bias voltage supplied to the target 10 are 90 A and 120 V, respectively, the size of the target 10 can be changed from 3 inches to 5 inches, and the current can be controlled by a magnetic field so that the arc rotates rather than concentrating in one place. Here, a device for rotating the target is provided.

[0027] Zirconium alloys undergo stress relaxation or partial recrystallization heat treatment depending on the alloy's composition. These heat treatments are used to maintain properties such as mechanical strength and corrosion resistance in the reactor. Recrystallization of most zirconium alloys begins at temperatures above 450°C. Long-term maintenance above the recrystallization temperature inevitably leads to recrystallization, which reduces mechanical strength and alters corrosion resistance due to increased precipitate size. Furthermore, partial recrystallization can damage the cladding tube 20 due to the difference between localized mechanical deformation in weak areas and creep and irradiation growth deformation. Therefore, undesired recrystallization in the cladding tube 20 can deviate from the intended performance of the cladding tube 20.

[0028] Arc ion plating is being developed as a technology for manufacturing accident-resistant nuclear fuel that can prevent hydrogen explosions by coating the surface of existing zirconium alloy cladding with an oxidation-resistant material to a thickness of 50 microns or less, thereby suppressing oxidation under normal reactor conditions and accident environments. Arc ion plating has been used in a variety of applications, including coating high-melting-point materials without damaging or changing the base material. However, when coating zirconium nuclear fuel cladding with an oxidation-resistant material (Cr or Cr-Al alloy), process variables can cause the heat from the process to reach the zirconium alloy, resulting in recrystallization.

[0029] One embodiment can prevent partial recrystallization from occurring along the length of the cladding tube 20. In a typical process, the application of current and bias voltage and the change in geometric shape that occurs during consumption of the coating target cause radiant heat generated during surface melting of the target to be transferred to the zirconium alloy, resulting in the accumulation of excessive temperature.

[0030] In one embodiment, the problem of microstructural change due to recrystallization of the zirconium alloy can be solved by limiting the preheating conditions for the initial vacuum, the applied current and bias voltage conditions during coating, and the radiant heat control conditions by controlling the target size and consumption area.

[0031] In one embodiment, the change in microstructure caused by the process heat generated when coating the cladding tube 20 with an oxidation-resistant material (Cr or Cr alloy, where Cr alloy includes Cr-based alloys including Cr-Al) in the arc ion plating process can be suppressed.

[0032] The heat generated during the arc ion plating vacuum deposition process and the conditions for transferring it to the cladding tube 20 of the coating object and for recrystallization will be explained.

[0033] 1) Preheating conditions for evacuating the chamber 100 during the vacuum heating step: To achieve a high vacuum state within the chamber 100, a heater is used to heat the chamber, activating gas molecules adhering to the interior and facilitating evacuation to the vacuum pump. The maximum heater temperature can be set to 350°C or less. Setting the maximum heater temperature to 350°C or less is lower than the recrystallization temperature of the zirconium alloy (450°C). However, the actual temperature of the zirconium alloy may increase due to the application of additional heat from the application of current and bias voltage to the target 10 in the subsequent process, which may result in recrystallization. This preheating process is different from the deposition process that follows, in which the temperature is less than approximately 200°C. The preheating process is performed for approximately 20 to 30 minutes.

[0034] 2) Conditions for the current supplied to the target 10 during the particle evaporation stage: An arc is generated on the surface of the target 10 to evaporate the target material. The arc heat exceeds 1,900°C to sufficiently ionize Cr and Cr alloys. The radiant heat of the arc generated at this time can cause recrystallization of the zirconium alloy. Therefore, the current for generating the arc can be set to 80 A or less, which is the minimum condition for melting the target 10.

[0035] 3) Bias voltage conditions between the target 10 and the cladding tube 20 during the coating process: The surface of the target 10 is ionized and vaporized by the arc, and the vaporized particles fly out from the target 10. If a bias voltage is applied at this time, the particle speed increases and the size of the vaporized particles also increases. The increased particle speed and size increase the heat of the particles that is transferred to the cladding tube 20 to be coated, increasing the possibility of recrystallization. Therefore, the maximum value of the bias voltage to increase the deposition rate can be set to less than 100V.

[0036] Additionally, as the target 10 is consumed, its surface changes to a concave lens shape. If the surface of the target 10 changes to a specific curvature, the radiant heat from the arc current is likely to concentrate on a specific region of the cladding tube 20, increasing the likelihood of recrystallization. Therefore, by adjusting the concave lens shape that is generated when the target 10 loses its surface, it is possible to prevent recrystallization from occurring due to the radiant heat concentrating on a specific region of the target.

[0037] Arc ion plating for coating accident-resistant nuclear fuel cladding tubes 20 involves placing a target 10 and a test piece in a chamber 100 and heating it to create a high-vacuum atmosphere. An electric current is then applied to the surface of the material (target) to be deposited instantaneously, generating an arc and vaporizing particles. A bias voltage is then applied to increase the deposition rate of the vaporized particles, allowing the ionized target material to coat the test piece uniformly.

[0038] However, in the process of coating the cladding tube 20 with an oxidation-resistant material (Cr, Cr alloy), a phenomenon may occur in which the cladding tube 20 is entirely or partially recrystallized unintentionally.

[0039] In one embodiment, to solve the problem of recrystallization of the zirconium alloy, the conditions for the vacuum heating conditions in the chamber 100, the current supplied to the target 10, and the bias voltage among the parameters of the arc ion plating process can be optimized. Also, to prevent the accumulation of radiant heat due to the formation of a concave lens when the target 10 is consumed, the size of the target 10 can be significantly changed, thereby eliminating the phenomenon of arc current concentrating in one area due to the magnetic field.

[0040] For example, during the process, the heating temperature of the chamber 100 when evacuated can be set to be maintained at 350° C. or less, the current supplied to the target 10 can be set to be maintained at 80 A or less, and the bias voltage can be set to be maintained at less than 100 V. If one or more of the setting conditions of the heating temperature, target current, and bias voltage exceed the set limit values, recrystallization problems of the zirconium alloy may occur.

[0041] The arc ion plating method according to one embodiment can be considered a type of physical vapor deposition method, and requires optimization of deposition conditions to perform atom-by-atom deposition by supplying a current and a bias voltage to the target 10.

[0042] Here, the current supplied to the target 10 is 80 A or less, preferably 70 A to 80 A, and the bias voltage can be set to less than 100 V, preferably 70 V to 100 V. If the current supplied to the target 10 is less than 70 A, the deposition rate may decrease. If the current supplied to the target 10 is greater than 80 A, the size and number of droplets generated in the coating thin film may increase.

[0043] On the other hand, if the bias voltage supplied to the target 10 is less than 70 V, the high-temperature oxidation resistance decreases and the coating thin film may peel off from the interface. If the bias voltage supplied to the target 10 is more than 100 V, the deposition rate may decrease significantly.

[0044] During deposition, the larger the size of the evaporated material, the slower it accelerates, and the slower it may collide with gas molecules and not reach the target. For this reason, increasing the operating pressure during deposition can reduce the probability of ions and droplets generated on the target 10 colliding with gas molecules. The operating pressure during deposition can be set to 5 mTorr to 30 mTorr. If the operating pressure during deposition is less than 5 mTorr, surface roughness and droplets may increase.

[0045] FIG. 4 is a graph comparing the change in the microstructure of the cladding tube 20 manufactured using the target setting conditions according to the first experimental example. FIG. 4 shows a 3-inch target. Referring to FIG. 4, the change in the microstructure of the cladding tube 20 is compared when the current supplied to the target 10 is maintained at 80 A or less and the bias voltage supplied to the target 10 is set to 70 V. As shown in the left diagram of FIG. 4, when the current supplied to the target 10 is maintained at 70 A and the bias voltage supplied to the target 10 is set to 70 V, there is no change in the microstructure of the cladding tube 20. In contrast, as shown in the right diagram of FIG. 4, when the current supplied to the target 10 is maintained at 90 A and the bias voltage supplied to the target 10 is set to 70 V, recrystallization occurs in the change in the microstructure of the cladding tube 20.

[0046] FIG. 5 is a graph comparing the microstructural changes of the cladding tube 20 manufactured using the target setting conditions according to the second experimental example. FIG. 5 shows a 3-inch target. Referring to FIG. 5, the bias voltage supplied to the target 10 was set to less than 100 V and more than 100 V, and the current supplied to the target 10 was set to 70 A, and the microstructural changes of the cladding tube 20 were compared. As shown in the left diagram of FIG. 5, when the current supplied to the target 10 was maintained at 70 A and the bias voltage supplied to the target 10 was set to 90 V, there was no change in the microstructural changes of the cladding tube 20. In contrast, as shown in the right diagram of FIG. 5, when the current supplied to the target 10 was maintained at 70 A and the bias voltage supplied to the target 10 was set to 120 V, recrystallization occurred in the microstructural changes of the cladding tube 20.

[0047] 6 is a diagram showing the change in the microstructure of the cladding tube 20 manufactured using the target setting conditions according to the third experimental example. Referring to FIG. 6, the current and bias voltage supplied to the target 10 are set to 90 A and 120 V, respectively, and the size of the target 10 is set to 3 inches. When the current and bias voltage supplied to the target 10 are set to 90 A and 120 V, respectively, the arc is concentrated at one point on the target 10, causing a change in the microstructure of the cladding tube 20, resulting in recrystallization.

[0048] FIG. 7 shows the change in the microstructure of the cladding tube 20 manufactured using the target setting conditions according to the fourth experimental example. Referring to FIG. 7, the current and bias voltage supplied to the target 10a are set to 90A and 120V, respectively, and the size of the target 10a is changed from 3 inches to 5 inches. When the current and bias voltage supplied to the 5-inch target 10a are set to 90A and 120V, respectively, there is no change in the microstructure of the cladding tube 20. This is because the current is controlled by the magnetic field so that the arc rotates rather than concentrating in one place in the 5-inch target 10a.

[0049] Recrystallization does not occur unless the current and bias voltage supplied to the target are low. Larger targets improve process efficiency, but high currents and bias voltages can make rotation control difficult. When the current supplied to the target is 80 A or less and the bias voltage is less than 100 V, there is no change in the microstructure if the target is 3 inches or larger. However, when the target is less than 3 inches, e.g., 2 inches, microstructure changes occur and process efficiency is low. The target size may be 10 inches or less. When the target is larger than 10 inches, manufacturing is difficult and target yield may decrease. For example, the target can be 3 to 5 inches in size. The efficiency of a 5-inch target is higher than that of a 3-inch target. When the current supplied to the target exceeds 80 A or the bias voltage is 100 V or more, there is no change in the microstructure if the target is 5 inches or larger and the current is controlled by a magnetic field to rotate in an arc. Furthermore, when the current exceeds 80 A or the bias voltage is 100 V or more, the target size is 4 inches, and an arc rotating magnetic field is present, there is no change in the microstructure. Accordingly, when the current exceeds 80 A or the bias voltage is 100 V or more, the target size is 4 inches or more, and an arc rotating magnetic field is present, there is no change in the microstructure. In this case, too, the target size is preferably 10 inches or less, taking manufacturability and target yield into consideration.

[0050] During the oxidation-resistant material deposition process for cladding tubes 20 used for accident-resistant nuclear fuel using arc ion plating, if the microstructure of the cladding tube 20 changes, it will affect its mechanical properties and corrosion characteristics, making it difficult to achieve the performance targets of the cladding tube 20 used for accident-resistant nuclear fuel. In one embodiment, a coating technology using zirconium alloy arc ion plating technology improves the adhesion between the coating layer and the base material, enabling the deposition of dense, high-quality coating layers without changing the performance of the base material. Accident-resistant nuclear fuel is required for all operating nuclear power plants in the future, according to the current EU taxonomy standard requiring the use of accident-resistant nuclear fuel in operating nuclear power plants after 2025. Therefore, the use of accident-resistant nuclear fuel cladding is inevitable in operating nuclear power plants. One embodiment is a core technology related to the manufacture of accident-resistant nuclear fuel cladding, and is expected to not only improve the safety of operating nuclear power plants but also bring significant economic benefits.

[0051] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A coated tube preparation step of preparing a coated tube made of a zirconium alloy material, A target preparation step of preparing a target including a coating substance to be coated on the surface of the coated tube and satisfying preset target conditions, A vacuum heating step of placing the coated tube and the target in a chamber and then performing vacuum heating under preset preheating conditions for initial vacuum, An etching step of supplying a preset current and bias voltage to the surface of the target to generate an arc, evaporating particles of the coating substance, and removing foreign substances on the surface, A particle evaporation step of supplying a current to the surface of the target under preset current conditions to generate an arc and evaporate particles of the coating substance, A coating step of supplying a bias voltage under preset voltage conditions to uniformly coat the surface of the coated tube with the ionized coating substance, A method for manufacturing a zirconium alloy coated tube, comprising: Adjusting the size of the target to be different according to preset target conditions for the current and bias voltage supplied to the target, By adjusting the target conditions, the preheating conditions, the current conditions, and the voltage conditions, dispersing the radiant heat transmitted from the evaporation part of the target to the coated tube, and preventing the accumulation phenomenon of radiant heat on the coated tube due to the formation of a concave lens during the consumption of the target, thereby adjusting the change in the microstructure to prevent the occurrence of recrystallization of the zirconium alloy on the surface of the coated tube, The target conditions satisfy a target size of 3 inches or more and 10 inches or less, The preheating conditions satisfy a preheating temperature of 350 degrees or less, The current conditions satisfy a current of 80 A or less, The voltage conditions in the etching step satisfy a voltage of 200 V to 600 V, The voltage conditions in the coating step satisfy less than 100 V, A method for manufacturing a zirconium alloy coated tube.

2. " The method for manufacturing a zirconium alloy coated tube according to Claim 1, wherein the coating substance contains an acid-resistant substance.

3. The method for manufacturing a zirconium alloy coated tube according to Claim 2, wherein the acid-resistant substance contains one or more of Cr and Cr alloys.

4. The method for manufacturing a zirconium alloy coated tube according to Claim 1, wherein the time in the etching step is set within 20 minutes.

5. The method for manufacturing a zirconium alloy coated tube according to claim 1, wherein the current supplied to the target in the particle evaporation stage exceeds 80 A, and / or the bias voltage in the coating stage satisfies one or more of the conditions of 100 V or more, the target rotates, and the size of the target is set to 4 inches or more and 10 inches or less.

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