KR20100114392A - Low temperature deposition process of functional multi-layer on nuclear fuel cladding for fast reactor - Google Patents

Abstract

PURPOSE: A method for depositing a functional multi-layered thin film on a nuclear fuel cladding for a fast reactor is provided to increase the lifetime of the nuclear fuel cladding for a reactor. CONSTITUTION: A functional material is directly deposited on the surface of a nuclear fuel cladding at a low temperature and is made of titanium, nickel, chrome, vanadium, zirconium, molybdenum, tungsten and tantalum, alloy thereof and oxide thereof. The titanium, the nickel-chrome alloy, and zirconium are successively deposited. The composition ratio of nickel-chrome alloy is 1:1.

Description

Low temperature deposition process of functional multi-layer on Nuclear Fuel Cladding for Fast Reactor

The present invention relates to a method of depositing a functional thin film for improving the lifetime of a fuel cladding for a high speed reactor, and more particularly, to a multi-layered structure of a functional thin film on the surface of a nuclear fuel cladding at a low temperature using a vacuum thin film process. It relates to a method of vapor deposition.

Nuclear fuel cladding for nuclear reactors is a component that effectively traps fuel and transfers heat generated by fission, which contains 8-12% of chromium in fourth-generation reactors such as sodium-cooled reactors (SFRs). Stainless steel is considered a fuel cladding material. However, these stainless steels react with metal uranium, which is a nuclear fuel material, at a reactor operating temperature of 650 ° C. or higher, and thus, the thickness of the cladding tube becomes thinner with time, resulting in a weakening of its integrity.

In order to prevent such a mutual reaction phenomenon and to improve the life of the cladding tube, research is being conducted to attach a material for preventing mutual diffusion on the inner surface of the cladding tube.

In Korean Unexamined Patent Application Publication No. KR-2009-0018396, a fuel rod for a fast reactor in which an oxide coating layer is formed on an inner surface of a coating tube in order to suppress a reaction between a fuel and a coating material is proposed. The concept of attaching chromium oxide, vanadium oxide and zirconium oxide to the inner surface of the coating tube by acid dissolution oxidation method, high temperature oxidation method, electrolytic oxidation method and vapor deposition method was proposed.

However, the above technique has a disadvantage in that the temperature range that suppresses diffusion by using a single layer is limited depending on the material used, and since the high temperature addition process is required to form the oxide, The problem that the intensity | strength of a cladding pipe falls is produced.

US Patent No. 4022662 discloses a cladding tube having a layer made of stainless steel, copper, a copper alloy, nickel, a nickel alloy, and the like and a diffusion barrier layer coated with chromium or a chromium alloy.

The method of manufacturing a cladding tube for preventing the interdiffusion reaction described in the above document forms a thin diffusion preventing layer made of a pure metal which does not form a mutual reaction layer with uranium, such as chromium or vanadium, for this purpose. By inserting the metal liner molded into the inside of the coating tube into the inside of the coating tube to produce a coating tube having an anti-diffusion layer inside through the extrusion molding process, a method of suppressing the interdiffusion reaction between the nuclear fuel and the coating tube is used.

However, the method of manufacturing a cladding tube to form a diffusion barrier layer in the cladding tube by a molding process is complicated and its cost is high, and the bonding strength between the diffusion barrier layer and the cladding tube base material is weak, resulting in a difference in thermal expansion between the two materials at high temperatures. There is a problem that is likely to be separated from each other by.

The Standford Research Institute (SRI) of the United States has reported a study on the suppression of chemical reaction with iodine generated after fission by coating a thin film on the inner surface of the cladding by using fluidized chemical vapor deposition. There has been no report on the substantial increase in chemical and mechanical durability by depositing functional thin films directly inside the cladding.

An attempt was made to collaborate on the coating of the cladding as part of the International Nuclear Joint Research (I-NERI) project between KAERI and the Standford Research Institute (SRI) in the United States. As a result, no research has been reported to characterize the deposition on high-speed nuclear fuel cladding.

The present invention, by using a vacuum thin film process on the nuclear fuel cladding for high-speed reactor to overcome the problems posed in the prior art, by depositing a functional material in a multi-layered form at a low temperature of the cladding in an even temperature range without changing the properties of the fuel cladding Life extension can be achieved.

An object of the present invention is to provide a manufacturing method for improving the life of the nuclear fuel cladding material for nuclear reactors.

In order to achieve the above object, the present invention provides a deposition method comprising directly depositing a functional material on the surface of the nuclear fuel cladding in the form of multiple thin films.

The functional material is one selected from the group consisting of titanium (Ti), nickel (Ni), chromium (Cr), vanadium (V), zirconium (Zr), molybdenum (Mo), tungsten (W) and tantalum (Ta). More elements are selected. Titanium has the effect of increasing the adhesion between the cladding and the functional material, nickel has the effect of increasing the adhesion between the functional material, and chromium, vanadium, zirconium, molybdenum, tungsten and tantalum, By having a lower diffusion rate than iron, which occupies most of them, there is an effect of preventing the interdiffusion between the cladding tube and the uranium element. In addition, as the functional material, the elements may be used in the form of an oxide or an alloy.

This functional multiple thin film is deposited on the cladding surface at a temperature from room temperature to 500 ° C. Since the temperature is lower than the reactor operating temperature of 650 ° C., it is possible to achieve the life of the fuel cladding tube without inducing additional changes in physical properties of the fuel cladding tube.

Such a functional multiple thin film preferably has a thickness of 0.5 μm to 100 μm. When the thickness of the functional multi-layer thin film is less than 0.5㎛, does not sufficiently suppress the interaction reaction, when the thickness of more than 100㎛, due to the thickness of the thick film has a problem that the heat emitted from the nuclear fuel is difficult to transfer efficiently.

Such functional multiple thin films are deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD), depending on the shape of the fuel cladding. More specifically, physical vapor deposition (PVD) includes R.F magnetron sputtering, D.C. Magnetron sputtering, thermal evaporation, E-Beam deposition, and the like, and chemical vapor deposition (CVD) includes thermal CVD, plasma CVD, laser CVD, metal-organic chemical vapor deposition (Metal-Organic Chemical Vapor) Deposition: MOCVD).

As described in detail above, the present invention provides a manufacturing method of coating a functional multi-film on the surface of a nuclear fuel cladding tube at a low temperature in order to extend the life of the nuclear fuel cladding material for nuclear reactors. Since the manufacturing method according to the present invention can be deposited at a low temperature in the form of multiple thin films, it is possible to achieve the extension of the life of the cladding tube at an even temperature range without changing the properties of the fuel cladding tube, compared to the conventional fuel cladding tube. Can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the scope of the present invention is not limited by these examples.

For the material used in the present embodiment, in order to improve the adhesion between the cladding tube and the material to be deposited, the titanium layer is preferentially deposited, and then an alloy material having a composition ratio of chromium and nickel of 1: 1 is used. By evaporation, and zirconium layers were sequentially deposited.

1 shows an experimental flow chart of depositing functional thin films in the form of multiple thin films. As the vapor deposition method used in this embodiment, R.F. Provided is a manufacturing method for directly depositing the above material on a nuclear fuel cladding material for a high speed furnace at room temperature using a Radio Frequency Magnetron Sputtering method.

The specific deposition method is as follows.

Example

(1) 12% chromium-containing stainless steel (HT9), a nuclear fuel cladding tube, was washed with acetone, ethyl alcohol, and isopropyl alcohol sequentially using an ultrasonic cleaner for 10 minutes for each process. It was then dried using nitrogen (99%).

(2) The fuel cladding material is introduced into a high vacuum chamber equipped with RF frequency magnetron sputtering, and then the chamber pressure is maintained at 10 ^-6 Torr or less using an exhaust valve. did.

(3) When the vacuum condition as described above is maintained, argon (Ar) gas is introduced to maintain the pressure of the chamber at 10 ^-1 to 10 ^-2 Torr, and then the surface of the target of nickel-chromium to be deposited is pretreated. did. This pretreatment process is intended to remove potential contaminants on the surface of the target. This process was conducted at 300 W for 15 minutes.

(4) After completing the above conditions, the pressure in the chamber was adjusted to 5 Pa 10 ^-3 Torr, and titanium was deposited at 200 W for 10 minutes.

(5) Then, after depositing the nickel-chromium alloy for 10 minutes at 200W, the pressure in the chamber was again maintained at 10 ⁻⁶ Torr.

(6) When the vacuum condition as described above is maintained, the argon (Ar) gas is introduced to maintain the pressure of the chamber at 10 ⁻¹ to 10 ⁻² Torr, and then the surface of the zirconium target to be deposited is subjected to a pretreatment process. This pretreatment process is intended to remove contaminants on the target surface. This process was performed at 300W for 15 minutes.

(7) After completing the above conditions, after adjusting the pressure of the chamber to 5 ㅧ 10 ^-3 Torr, zirconium was deposited at 200W for 40 minutes. When deposition was complete, the pressure in the chamber was maintained at 10 ⁻⁶ Torr or less using an exhaust valve.

(8) When the above conditions were completed, the above steps (5) to (7) were repeated five or more times to deposit a functional thin film having a multilayer structure on the cover tube material for the nuclear reactor.

Experiments were conducted to see if the functional material produced according to the above process could actually prevent the spread of nuclear fuel.

Experimental Example

A metal fuel plate containing 10 wt% of zirconium in uranium was prepared, and then faced with the sample on which the multiple thin films were deposited, and then closely contacted with a screw, and then exposed to a vacuum furnace for 25 hours and cooled. Cross sections of the bonded specimens were observed using a scanning electron microscope.

In the case of the specimen on which the functional thin film is deposited, it is observed that the reaction between the nuclear fuel and the cladding does not occur and the cladding and the fuel are separated (FIG. 4).

Comparative Experiment

After the exposure of the cladding tube material and the metal fuel plate on which the multiple thin films were not deposited and exposure for the same time as in Example, the cross section of the cooled and bonded specimens was observed using a scanning electron microscope.

In the case of the specimen in which the functional thin film was not deposited, it was observed that the nuclear fuel and the coating material reacted with each other to form a reaction layer having a thickness of about 250 μm (FIG. 5).

As mentioned above, specific parts of the present invention have been described in detail, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Therefore, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

1 is a flow chart for manufacturing a functional multiple thin film according to the present invention.

Figure 2 shows a photograph of the cross-section of the cross-sectional view of the functional multi-layer thin film deposited according to the embodiment with a scanning electron microscope (Scanning Electron Microscope).

3 is a result of analysis of the elements contained in the functional thin film prepared according to the embodiment by Auger Electron Spectroscopy (Auger Electron Spectroscopy).

4 is a result (example) of a test for mounting a functional multiple thin film deposited on the surface of a nuclear fuel cladding tube.

5 is a result (comparative example) of a test for mounting a functional multiple thin film deposited on a fuel cladding tube surface.

Claims (15)

A method of depositing a functional material on a fuel cladding tube comprising depositing the functional material directly on the surface of the fuel cladding tube at a low temperature in a multi-film form. The method of claim 1, wherein the functional material is at least one selected from the group consisting of titanium, nickel, chromium, vanadium, zirconium, molybdenum, tungsten and tantalum, alloys thereof, and oxides thereof. Deposition method. The method of claim 2, wherein the functional material is at least one selected from the group consisting of titanium, nickel, chromium and zirconium, alloys thereof, and oxides thereof. The method of claim 1, wherein the deposition is performed in the order of titanium, nickel-chromium alloy and zirconium. The method of claim 4, wherein the composition ratio of the nickel-chromium alloy is 1: 1. 2. The method of claim 1, wherein the deposition temperature of the functional multiple thin film is from room temperature to 500 ° C. 3. The method of claim 1, wherein the thickness of the functional multilayer is 0.5 μm to 100 μm. The method of claim 1, wherein the functional multiple thin film is deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD). The method of claim 8, wherein physical vapor deposition (PVD) is performed by R.F magnetron sputtering, D.C. A method of depositing a functional material on a surface of a nuclear fuel cladding tube, characterized in that it is selected from the group consisting of magnetron sputtering, thermal evaporation, E-Beam deposition, and the like. The method of claim 8, wherein the chemical vapor deposition (CVD) is selected from the group consisting of thermal CVD, plasma CVD, laser CVD, metal-organic chemical vapor deposition (MOCVD), and the like. A method of depositing a functional material on the surface of a nuclear fuel cladding tube. A nuclear fuel cladding tube for a high-speed reactor obtained by depositing a functional material by the vapor deposition method according to claim 1. 12. The nuclear fuel cladding according to claim 11, wherein the functional material is at least one selected from the group consisting of titanium, nickel, chromium, vanadium, zirconium, molybdenum, tungsten and tantalum, alloys thereof, and oxides thereof. The nuclear fuel clad tube according to claim 12, wherein the functional material is at least one selected from the group consisting of titanium, nickel, chromium and zirconium, alloys thereof and oxides thereof. 12. The nuclear fuel cladding according to claim 11, wherein the deposition is performed in the order of titanium, nickel-chromium alloy, and zirconium. 15. The nuclear fuel clad tube according to claim 14, wherein the composition ratio of the nickel-chromium alloy is 1: 1.

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