KR102320638B1 - Nuclear fuel cladding with composite coating layer and method for manufacturing the same - Google Patents

Abstract

The present invention is a nuclear fuel cladding; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; And it relates to a nuclear fuel cladding having a composite coating layer including a chromium nitride coating layer formed through nitriding on the chromium coating layer and a method for manufacturing the same.

Description

Nuclear fuel cladding with composite coating layer and manufacturing method thereof

The present invention relates to a nuclear fuel cladding having a composite coating layer and a method for manufacturing the same.

The sodium-cooled fast reactor, one of the 4th generation nuclear power plants, uses sodium as a coolant and produces heat generated by fission with high-energy fast neutrons into electricity. Countries around the world are accelerating R&D. The sodium-cooled high-speed reactor is a nuclear reactor with a 60 times higher uranium utilization rate, excellent nuclear proliferation resistance, and improved safety compared to existing nuclear reactors. Light and heavy water reactors currently in operation contain 93-96% of reusable uranium, which can be used as a power source for sodium-cooled high-speed reactors using reprocessing technology. The spent nuclear fuel in oxide form is converted into metallic fuel (TRU element) through a pyroprocessing process and burned in a sodium-cooled high-speed reactor. In this process, TRU elements such as plutonium are annihilated. Metal fuel (U-Zr-TRU-RE alloy) is being considered as a promising nuclear fuel for sodium-cooled high speed reactors because it is possible to design a high-power core due to high heat conduction and has high nuclear diffusion resistance. However, at the operating temperature of the sodium-cooled high-speed reactor (580-680℃ and higher), U, TRU, RE, which are components of metal fuel, and HT9 (ferritic/martensitic steel), which is a cladding material, interact with each other (Fuel-Cladding Chemical Reaction, FCCI) This interaction produces low-melting eutectic compounds and reduces the thickness of the cladding, which deteriorates the fuel integrity.

In order to prevent the mutual reaction between the nuclear fuel and the cladding material, various technologies are being developed around the world, and in particular, a method of applying a barrier between the nuclear fuel and the cladding material has been suggested as a representative method. Materials selection studies using metal flakes and coating technology studies such as deposition, plating, and oxidation methods were conducted together, and Cr, Ti, V, Ta, Mo with low neutron absorption and high thermal conductivity and melting point can be selected as barrier materials. In particular, although research on coating technology such as electrolytic plating using Cr as a barrier material is being actively conducted, there is no research on the type of the optimized current waveform in applying this electroplating method.

Korean Patent Publication No. 10-1198863 (2012. 11. 01.)

The present invention provides a nuclear fuel cladding; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; and a nuclear fuel cladding having a composite coating layer including a chromium nitride coating layer formed through nitriding on the chromium coating layer.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention comprises the steps of (a) forming a chromium coating layer on the inner surface of a nuclear fuel cladding through direct current (DC) electrolytic plating; and (b) forming a chromium nitride coating layer on the chromium coating layer through a nitriding process.

In one embodiment of the present invention, a nuclear fuel cladding; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; And it provides a nuclear fuel cladding having a composite coating layer comprising a chromium nitride coating layer formed through nitriding on the chromium coating layer.

A nuclear fuel cladding pipe provided with a composite coating layer according to the present invention includes a nuclear fuel cladding pipe; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; and a chromium nitride coating layer formed on the chromium coating layer through nitriding treatment, due to the small surface roughness of the chromium coating layer, the finally formed composite coating layer can maintain a crack-free state, so that nuclear fuel and Interaction between the cladding (ie, eutectic phenomenon) can be effectively prevented. Therefore, it is expected to greatly increase the stability of nuclear power generation.

1 is a schematic diagram showing a nuclear fuel cladding pipe provided with a composite coating layer according to an embodiment of the present invention.
Figure 2 (a) is a photograph showing the electrolytic plating apparatus used in Example 1, Figure 2 (b) is a photograph showing the chrome coating layer formed in Example 1, Figure 2 (c) is a photograph used in Example 1 It is a photograph showing a plasma processing apparatus.
3 (a) and (b) are SEM photographs (surface and cross-section) and XRD analysis graphs showing whether the microstructure is changed as the optimized plasma nitriding treatment is performed on the chromium coating layer in a crack-free state according to Example 1; am.
4 (a) and (b) are SEM photographs (surface and cross-section) showing whether the microstructure is changed as the optimized plasma nitriding treatment is performed on the cracked chromium coating layer according to Example 2.
Figure 5 (a) shows the microstructure of the final final composite coating layer according to DC and PC current waveforms when the optimized plasma nitridation treatment is performed on the chromium coating layer in a crack-free state according to Example 1 and Comparative Example 1 for 30 hours; is an SEM photograph (cross-section and surface) comparing , It is an SEM photograph (cross-section) comparing whether the finally formed composite coating layer can prevent the interaction between nuclear fuel and cladding in a transient state of 650°C or higher according to DC and PC current waveforms.

The present inventors sequentially formed a chromium coating layer and a chromium nitride coating layer by a two-step process while researching a barrier for effectively preventing the interaction between nuclear fuel and the cladding (ie, eutectic phenomenon) By doing so, it was confirmed that the barrier in a crack-free state can be successfully manufactured, and the present invention was completed.

Hereinafter, the present invention will be described in detail.

Method for manufacturing nuclear fuel cladding with composite coating layer

The present invention comprises the steps of (a) forming a chromium coating layer on the inner surface of a nuclear fuel cladding through direct current (DC) electrolytic plating; and (b) forming a chromium nitride coating layer on the chromium coating layer through a nitriding process.

First, the nuclear fuel cladding provided with a composite coating layer according to the present invention includes a step [(a) step] of forming a chrome coating layer on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating.

Specifically, the present invention is characterized in that a direct current (DC) electroplating method is used to form a chromium coating layer on the nuclear fuel cladding tube.

The nuclear fuel cladding pipe is for protecting nuclear fuel from the outside in a sodium-cooled high speed reactor, and it is preferable to use a ferrite/martensitic steel material, but is not limited thereto. In the present invention, as the material of the nuclear fuel cladding, HT9 material was used. The HT9 material uses iron as a base element, Cr: 12 wt%, Mo: 1 wt%, C: 0.17 wt%, Si: 0.25 wt% , Ni: 0.5 wt% and the like.

Conventionally, in order to form a chromium coating layer on a nuclear fuel cladding, various coating techniques such as a deposition method, a plating method, and an oxidation method have been applied. In the present invention, a direct current (DC) electroplating method is adopted among various coating technologies.

In general, the electroplating method is divided into direct current (DC) or pulse current (PC) depending on the type of current waveform applied during electroplating, and accordingly, the microstructure of the coating layer, whether cracks, grain size and mechanical characteristics change.

If the nitriding treatment described later is not performed, the pulse current (PC) electroplating method can form a crack-free chromium coating layer regardless of whether the conditions are optimized, and thus has an advantage over the direct current (DC) electroplating method. However, since the chromium coating layer formed through the pulse current (PC) electroplating method has a large surface roughness, in the process of cooling to room temperature after nitriding treatment to be described later, thermal cracks due to different thermal expansion coefficients between the chromium coating layer and the chromium nitride coating layer ) is easily generated, which is not preferable because it forms microcracks in the finally formed composite coating layer.

More specifically, the direct current (DC) electroplating method uses an aqueous solution of trivalent or hexavalent acid (chromium oxide), but at a temperature of 50°C to 100°C, 0.1 mA/cm ² to 10 mA/cm ² Average current density It may be carried out for 10 minutes to 600 minutes with ^{an average current density of 1 mA / cm 2} to 3 mA / cm ² at a temperature of 70 ° C. to 100 ° C. It is preferably carried out for 50 minutes to 100 minutes, but limited thereto doesn't happen In this case, when the temperature of the direct current (DC) electroplating method is 70° C. to 100° C., it has the advantage of forming a crack-free chromium coating layer.

The average thickness of the chromium coating layer may be 10 μm to 100 μm, preferably 20 μm to 100 μm, but is not limited thereto. At this time, when the average thickness of the chromium coating layer is too small, less than 20 μm, relatively small chromium crystal grains are distributed on the surface, so that the material is well diffused. Accordingly, there is a problem in that the interaction between the nuclear fuel and the cladding (ie, eutectic phenomenon) is increased in the transient state. The chromium coating layer may have an average thickness of the chromium coating layer in the finally formed composite coating layer reduced by about 1% to about 10% compared to the chromium coating layer according to a nitridation treatment to be described later.

In addition, the chromium coating layer may be in a non-cracked or cracked state, and preferably in a non-cracked state, but even in a cracked state in which microcracks are formed, as the nitriding treatment described below is performed, the chromium nitride coating layer is microcracked in the chromium coating layer It is formed between the micro-cracks and can recover micro-cracks, thereby preventing performance degradation caused by micro-cracks. Therefore, the composite coating layer to be described later may be in a crack-free state.

In addition, the chromium coating layer is characterized in that the small chromium crystal grains are evenly distributed so that the surface roughness is small, and its arithmetical average roughness (Ra) is preferably 0.1 μm or less, and 0.01 μm to 0.05 μm. More preferably, but not limited thereto. On the other hand, the chromium coating layer formed through the pulsed current (PC) electroplating method is characterized in that small chromium grains are distributed near the interface with the cladding, and large chromium grains are distributed near the interface with the outside, resulting in a large surface roughness. An arithmetical average roughness (Ra) thereof may be 0.2 μm or more.

Next, the nuclear fuel cladding provided with the composite coating layer according to the present invention includes a step [(b) step] of forming a chromium nitride coating layer on the chromium coating layer through nitriding treatment.

Specifically, the present invention is characterized in that a chromium coating layer is formed on the nuclear fuel cladding through a direct current (DC) electrolytic plating method, and then a nitriding treatment is performed. Thereafter, it may be cooled to room temperature (20° C. to 30° C.).

The nitriding treatment is preferably performed through a plasma nitridation method, which has the advantage that the nitriding treatment can be performed under a relatively low temperature condition (a temperature condition lower than the heat treatment temperature of the nuclear fuel cladding).

More specifically, the plasma nitridation method is performed under a nitrogen atmosphere, at a temperature of 400° C. to 800° C., and ^{a vacuum degree of 1 X 10 -4} Torr to 1 X 10 ^-1 Torr with an RF power of 10 W to 3000 W for 0.1 hours to 100 time, specifically, under a nitrogen and hydrogen mixed (H ₂ -N ₂ ) atmosphere or ammonia (NH ₃ ) atmosphere, at a temperature of 400° C. to 700° C. and 1 X 10 ^-4 Torr to 1 X 10 ⁻ It is preferably performed for 10 hours to 100 hours with an RF power of 100 W to 500 W at a vacuum degree of ^{1 Torr, but is not limited thereto.} In particular, when the chromium coating layer is in a cracked state, in order to recover microcracks, increase the RF power or sufficiently nitriding for 30 hours or more (preferably 50 hours or more) within the same conditions as above. It is preferred, but not limited thereto.

The chromium nitride coating layer is a ceramic material, and has an advantage of superior barrier properties compared to the chromium coating layer, but cracks, interfacial gaps, and peeling due to physical differences such as thermal expansion and ductility with ferrite/martensitic steel, which is a material of the nuclear fuel cladding. As such phenomena occur, it is difficult to directly apply to the inner surface of the nuclear fuel cladding tube. Accordingly, the chromium nitride coating layer is formed through nitridation of the chromium coating layer (buffering action), and since a portion of the chromium coating layer is modified with the chromium nitride coating layer, a composite coating layer having excellent interfacial adhesion can be formed. On the other hand, when the chromium coating layer is in a cracked state, the chromium nitride coating layer is formed between the microcracks of the chromium coating layer, so that the microcracks can be restored, thereby preventing performance degradation caused by the microcracks.

The chromium nitride coating layer may include Cr ₂ N or CrN, and in this case, CrN may be formed as the nitriding treatment time increases.

The chromium nitride coating layer is formed by nitriding a portion of the chromium coating layer, and may have an average thickness of 0.1 μm to 10 μm. At this time, if the average thickness of the chromium nitride coating layer is too small, there is a problem that the effect is insignificant. ) is a problem that occurs again.

Nuclear fuel cladding with composite coating layer

The present invention is a nuclear fuel cladding; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; And it provides a nuclear fuel cladding having a composite coating layer comprising a chromium nitride coating layer formed through nitriding on the chromium coating layer.

A nuclear fuel cladding pipe provided with a composite coating layer according to the present invention includes a nuclear fuel cladding pipe; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; and a chromium nitride coating layer formed through nitridation on the chromium coating layer, wherein the composite coating layer may be in a crack-free state capable of preventing interaction between nuclear fuel and the cladding, which is the chromium coating layer having a small surface roughness maintained as a result. Therefore, as a barrier, the composite coating layer can effectively prevent the interaction (ie, eutectic phenomenon) between the nuclear fuel and the cladding in a transient state.

Since the "nuclear fuel cladding", the "chromium coating layer formed through the direct current (DC) electroplating method" and the "chromium nitride coating layer formed through the nitriding process" have been described above, redundant descriptions will be omitted.

As described above, the nuclear fuel cladding pipe provided with a composite coating layer according to the present invention includes a nuclear fuel cladding pipe; a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; and a chromium nitride coating layer formed on the chromium coating layer through nitriding treatment, due to the small surface roughness of the chromium coating layer, the finally formed composite coating layer can maintain a crack-free state, so that nuclear fuel and Interaction between the cladding (ie, eutectic phenomenon) can be effectively prevented. Therefore, it is expected to greatly increase the stability of nuclear power generation.

Hereinafter, preferred examples are presented to help the understanding of the present invention. However, the following examples are only provided for easier understanding of the present invention, and the contents of the present invention are not limited by the following examples.

[Example]

Example 1: Formation of a chromium coating layer in a crack-free state through direct current (DC) electroplating method and plasma nitridation treatment thereof

First, a chromium coating layer was formed on the inner surface of the nuclear fuel cladding made of HT9 (ferrite/martensitic steel) through DC electroplating.

In this case, for the DC electroplating method, the electroplating apparatus developed by the present inventors as shown in FIG. 2(a) was used. The electroplating apparatus shown in FIG. 2(a) can install a metric-level nuclear fuel cladding tube, and when performing DC electroplating, a trivalent chromium oxide aqueous solution, which is a plating solution, is mixed with a Teflon hose in a container. It flows through the inner surface of the nuclear fuel cladding. The Pb/Sn wire, which serves as an electrode, is fixed through the inner surface of the vertically mounted nuclear fuel cladding. To prevent short circuit, a spring is used to keep the wire taut regardless of the length that is stretched during DC electroplating.

Specifically, the DC electroplating method was performed at a temperature of about 80° C. with an average current density (J _A) ^{of about 1.99 mA/cm 2} for 90 minutes.

As shown in FIG. 2(b), the formed chromium coating layer (about 26.4-34.9 μm thick) is in a crack-free state, and small chromium crystal grains are evenly distributed, so that the arithmetical average roughness (Ra) of the surface is 0.025. It is measured to be at the level of ± 0.010 ㎛ (measurement equipment: Taylor Hobson Talysurf Intra 50 mm profilometer).

Next, a chromium nitride coating layer was formed by cooling to room temperature after plasma nitriding treatment on the formed chromium coating layer.

In this case, the plasma nitridation process was performed using the plasma processing apparatus developed by the present inventors shown in FIG. 2(c). In the plasma processing apparatus illustrated in FIG. 2C , the density of plasma increases as the RF power increases.

Specifically, the plasma nitridation treatment was performed _{under an atmosphere of N 2} -40%H ₂ at a temperature of about 600° C. and ^{a vacuum degree of about 2-9 X 10 -2} Torr with an RF power of about 180 W for about 10-30 hours. .

3 (a) and (b) are SEM photographs (surface and cross-section) and XRD analysis graphs showing whether the microstructure is changed as the optimized plasma nitriding treatment is performed on the chromium coating layer in a crack-free state according to Example 1; am.

As shown in Figure 3 (a), as the plasma nitridation treatment optimized on the chromium coating layer in a crack-free state prepared through DC electroplating method was performed, it was confirmed that the chromium nitride coating layer was successfully formed on the outer surface of the chromium coating layer. As a result, it can be seen that the interaction between the nuclear fuel and the cladding can be prevented.

In addition, as shown in Figure 3 (b), when the optimized plasma nitridation treatment is performed on the chromium coating layer in a crack-free state prepared through DC electroplating for 10 hours, it is confirmed that only the _{Cr 2 N coating layer is formed,} When the optimized plasma nitridation treatment is performed for 20 hours on the crack-free chromium coating layer prepared through the DC electroplating method, _{it is confirmed that Cr 2} N and CrN are formed together. Therefore, it is expected that the longer the plasma nitridation treatment time, the more effective it is to prevent the interaction between the nuclear fuel and the cladding.

Example 2: Formation of Cracked Chrome Coating Layer by Direct Current (DC) Electrolytic Plating and Plasma Nitriding Treatment

A chrome coating layer was formed in the same manner as in Example 1, except that DC electroplating was performed for 70 minutes at an average current density (J _A) ^{of about 1.99 mA/cm 2} at a temperature of about 60° C. did.

The chromium coating layer (about 21.4 ± 1.4 μm average thickness) thus formed is a crack state in which microcracks exist, and small chromium grains are evenly distributed, so that the arithmetical average roughness (Ra) of the surface is 0.04 ± 0.02 μm. (Measuring equipment: Taylor Hobson Talysurf Intra 50 mm profilometer).

Next, a chromium nitride coating layer was formed on the formed chromium coating layer by cooling to room temperature after plasma nitridation in the same manner as in Example 1.

4 (a) and (b) are SEM photographs (surface and cross-section) showing whether the microstructure is changed as the optimized plasma nitriding treatment is performed on the cracked chromium coating layer according to Example 2.

As shown in Figs. 4 (a) and (b), as the optimized plasma nitridation treatment was performed on the cracked chrome coating layer prepared through DC electroplating, the chrome nitride coating layer was successfully formed on the outer surface of the chrome coating layer. is confirmed to be In particular, when the optimized plasma nitriding treatment is performed on the cracked chromium coating layer prepared through DC electroplating for 30 hours, the chromium nitride coating layer is formed between the microcracks of the chromium coating layer, so that the microcracks can be recovered. , it is possible to prevent performance degradation caused by microcracks. On the other hand, according to the optimized plasma nitridation treatment, since a portion of the chromium coating layer was modified with the chromium nitride coating layer, a composite coating layer having excellent interfacial adhesion was formed. On the other hand, as shown in the upper right figure of FIG. 4(b), when the thickness of the cracked chromium coating layer prepared through DC electroplating is about 10 μm, then, the optimized plasma nitriding treatment is performed for 30 hours. When done, it is confirmed that the crack is much restored. However, as shown in the lower right figure of FIG. 4(b), when the thickness of the cracked chromium coating layer manufactured through DC electroplating is about 30 μm, then, the optimized plasma nitriding treatment is performed for 30 hours. Even if it does, it is confirmed that the crack is not properly repaired. Therefore, if the thickness of the cracked chromium coating layer manufactured through the DC electroplating method becomes thick, it is necessary to increase the RF power or increase the time in the optimized plasma nitridation process.

Comparative Example 1: Formation of a crack-free chromium coating layer through pulse current (PC) electroplating method and plasma nitridation treatment thereof

First, a chromium coating layer was formed on the inner surface of the nuclear fuel cladding made of HT9 (ferritic/martensitic steel) through PC electroplating.

At this time, the PC electroplating method also used the electrolytic plating apparatus developed by the present inventors shown in FIG. 2(a).

Specifically, the PC electroplating method has a duty cycle (γ) of about 0.5 at a temperature of about 60°C, a frequency (f) of about 0.5 m/s, and an average current density (average ^{) of about 0.995 mA/cm 2} current density; J _A) for 75 min.

The resulting chrome coating layer (about 20.6 ± 1.9 ㎛ average thickness) is in a crack-free state, but small chromium grains are distributed near the interface with the cladding, and large chromium grains are distributed near the interface with the outside. do. Therefore, the arithmetical average roughness (Ra) of the surface is measured to be at the level of 0.20 ± 0.010 μm (measurement equipment: Taylor Hobson Talysurf Intra 50 mm profilometer).

Next, a chromium nitride coating layer was formed on the formed chromium coating layer by cooling to room temperature after plasma nitridation in the same manner as in Example 1.

5 (a) is a microstructure of the finally formed composite coating layer according to DC and PC current waveforms when the optimized plasma nitriding treatment is performed on the chromium coating layer in a crack-free state according to Example 1 and Comparative Example 1 for 30 hours; are SEM pictures (cross-section and surface) comparing .

As shown in Figure 5 (a), since the surface roughness of the chromium coating layer in a non-cracked state according to Example 1 is small, it is cooled to room temperature after performing an optimized plasma nitriding treatment at a temperature of about 600° C. for 30 hours. Even so, it is confirmed that micro-cracks are not formed in the finally formed composite coating layer. However, since the crack-free chromium coating layer according to Comparative Example 1 has a large surface roughness, in the process of cooling to room temperature after performing an optimized plasma nitridation treatment at a temperature of about 600° C. for 30 hours, the chromium coating layer and the chromium nitride coating layer Since thermal cracks easily occur due to different coefficients of thermal expansion, it is confirmed that microcracks are formed in the finally formed composite coating layer. That is, when the chromium coating layer is manufactured by applying the DC current waveform, the crack-free state can be maintained even after cooling after the optimized plasma nitriding treatment. Cooling can cause cracks that did not exist.

5 (b) is a composite coating layer finally formed according to DC and PC current waveforms when the optimized plasma nitriding treatment is performed on the chrome coating layer in a crack-free state according to Example 1 and Comparative Example 1 for 10 hours or 30 hours This is an SEM picture (cross-section) comparing whether the interaction between nuclear fuel and cladding can be prevented in a transient state of 650°C or higher.

As shown in Fig. 5(b), when the optimized plasma nitriding treatment is performed on the chromium coating layer in a crack-free state according to Example 1 for 10 hours, a composite coating layer in a crack-free state is finally formed, in a transient state. It has been found that interaction between nuclear fuel and cladding can be prevented. On the other hand, when the optimized plasma nitriding treatment is performed on the chromium coating layer in a crack-free state according to Comparative Example 1 for 10 hours or 30 hours, due to the large surface roughness (ie, non-uniform thickness) of the chromium coating layer, new cracks are formed It is confirmed that the interaction between the nuclear fuel and the cladding occurs in the transient state, and this interaction is confirmed to be intensified as the plasma nitridation processing time increases. In other words, when a chromium coating layer is manufactured by applying a DC current waveform, it is possible to prevent the interaction between nuclear fuel and the cladding in a transient state by maintaining a crack-free state even after cooling after optimized plasma nitriding treatment, but by applying a PC current waveform In the case of manufacturing a chromium coating layer, when cooled after the optimized plasma nitridation process, cracks that did not exist may occur, which may cause a lot of interaction between nuclear fuel and the cladding tube in a transient state.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (10)

(a) forming a chromium coating layer on the inner surface of the nuclear fuel cladding through direct current (DC) electrolytic plating; and
(b) forming a chromium nitride coating layer on the chromium coating layer through nitridation,
The nuclear fuel cladding includes a ferrite/martensitic steel material,
The direct current electroplating method is performed for 10 minutes to 600 minutes with an average current density of ^{0.1 mA/cm 2} to 10 mA/cm ² at a temperature of 50° C. to 100° C.,
The arithmetical average roughness (Ra) of the chromium coating layer in step (a) is 0.1 μm or less,
The chromium coating layer in step (a) is in a non-cracked or cracked state, and the composite coating layer finally formed through step (b) is in a crack-free state.
delete According to claim 1,
In the step (a), the average thickness of the chromium coating layer is 10 μm to 100 μm, the method for manufacturing a nuclear fuel cladding having a composite coating layer.
delete delete According to claim 1,
The method of manufacturing a nuclear fuel cladding provided with a composite coating layer, characterized in that the nitridation treatment in step (b) is performed through a plasma nitridation method.
7. The method of claim 6,
The plasma nitridation method is carried out for 0.1 hours to 100 hours with RF power of 10 W to 3000 W at a temperature of 400° C. to 800° C. and ^{a vacuum degree of 1 X 10 -4} Torr to 1 X 10 ^{-1 Torr under a nitrogen atmosphere.} A method for manufacturing a nuclear fuel cladding provided with a composite coating layer, characterized in that.
According to claim 1,
The method for manufacturing a nuclear fuel cladding pipe provided with a composite coating layer, characterized in that the average thickness of the chromium nitride coating layer in step (b) is 0.1 μm to 10 μm.
ferritic/martensitic steel fuel cladding;
a chrome coating layer formed on the inner surface of the nuclear fuel cladding through direct current (DC) electroplating; and
It includes a chromium nitride coating layer formed through nitriding on the chromium coating layer,
An arithmetic average roughness (Ra) of the chromium coating layer is 0.1 μm or less,
The composite coating layer is in a crack-free state that can prevent the interaction between the nuclear fuel and the cladding,
A nuclear fuel cladding with a composite coating layer. delete

Images