KR20220166524A - Nuclear fuel pellet having enhanced thermal conductivity and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a nuclear fuel pellet for increasing thermal conductivity and a manufacturing method thereof. The nuclear fuel pellet comprises: an oxide nuclear fuel matrix; and a plate-like coated thermal conductivity metal array dispersed in the matrix. The plate-like coated thermal conductivity metal array has an aluminum compound coated on all or part of a surface of a plate-shaped thermal conductivity metal.

Description

Nuclear fuel pellet with improved thermal conductivity and manufacturing method thereof

The present invention relates to a nuclear fuel pellet with improved thermal conductivity and a manufacturing method thereof.

Uranium dioxide (UO ₂ ), a material for a light-water reactor nuclear fuel pellet, has good compatibility with water used as a light-water reactor coolant, has a high melting point of about 2850 ° C, and exhibits excellent in-furnace stability such that phase transformation does not occur even at high temperatures. Therefore, although it has disadvantages in terms of thermal conductivity and uranium density compared to other uranium compounds (UC, UN, etc.), it is widely used as a material for light water reactor nuclear fuel pellets.

However, the UO ₂ The low thermal conductivity characteristic forms a rapid temperature gradient inside the UO ₂ nuclear fuel pellet and causes a high fuel core temperature. This temperature gradient acts as a very unfavorable factor in terms of nuclear fuel safety in normal operation and transient state of nuclear fuel. Therefore, the technology for improving the thermal conductivity of the UO ₂ nuclear fuel pellets is a very important factor in terms of nuclear fuel performance and safety. There is a method of adding heterogeneous materials as a method of improving the thermal conductivity of the UO ₂ nuclear fuel pellets _. need.

Domestic Registered Patent Publication No. 2016-0051113 (2016.05.11)

The present invention is to maximize the effect of improving thermal conductivity while minimizing the addition of heterogeneous materials, comprising an oxide nuclear fuel matrix; and a plate-shaped coated thermally conductive metal array dispersed in the matrix, wherein the plate-shaped coated thermally conductive metal array is coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal, a nuclear fuel having improved thermal conductivity. It is intended to provide a sintered body and the like.

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

The present invention relates to an oxide nuclear fuel matrix; and a plate-shaped coated thermally conductive metal array dispersed in the matrix, wherein the plate-shaped coated thermally conductive metal array is coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal, a nuclear fuel having improved thermal conductivity. A sintered body is provided.

In addition, in the nuclear fuel pellet having improved thermal conductivity according to an embodiment of the present invention, the coated thermally conductive plate-shaped metal array may be distributed in a horizontal direction within the matrix to have orientation.

In addition, in the nuclear fuel pellet with improved thermal conductivity according to another embodiment of the present invention, the content of the coated thermally conductive plate-like metal array may be 1 wt% to 5 wt% based on the total weight of the matrix.

In addition, in the nuclear fuel pellet with improved thermal conductivity according to another embodiment of the present invention, the aluminum compound content may be 0.05 wt% to 0.5 wt% based on the total weight of the plate-shaped thermally conductive metal.

In addition, in the nuclear fuel pellet with improved thermal conductivity according to an embodiment of the present invention, the plate-shaped thermally conductive metal is molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium ( V), hafnium (Hf), tantalum (Ta), rhodium (Rh), and zirconium (Zr), wherein the aluminum compound includes aluminum oxide (Al ₂ O ₃ ), aluminum metal salt , (Al(NO ₃ ) ₃ ) and (AlCl ₃ ), and aluminum hydroxide (Al(OH) ₃ ).

Also, in the nuclear fuel pellet with improved thermal conductivity according to another embodiment of the present invention, the ratio of the average width to the thickness of the plate-shaped coated thermally conductive metal array may be 10 to 300.

In addition, in another embodiment of the present invention, in the nuclear fuel pellet with improved thermal conductivity, the aluminum compound may have an average particle size of 0.1 μm to 50 μm.

In addition, the present invention provides (a) preparing a plate-shaped coated thermally conductive metal powder by coating all or part of the surface of the plate-shaped thermally conductive metal powder with an aluminum compound, and (b) the plate-shaped coated thermally conductive metal prepared in step (a). Provided is a method for manufacturing a nuclear fuel pellet with improved thermal conductivity, comprising mixing powder and oxide nuclear fuel powder, followed by molding and heat treatment.

In addition, in the manufacturing method of a nuclear fuel pellet with improved thermal conductivity according to an embodiment of the present invention, in step (a), the plate-shaped coated thermally conductive metal powder is prepared through a milling process after mixing the spherical thermally conductive metal powder and an aluminum compound. How to; Alternatively, a method of manufacturing a spherical thermally conductive metal powder by contacting it with an aluminum compound after performing a milling process; It may be a thermally conductive metal powder prepared by any one method selected from among.

In addition, in the method of manufacturing a nuclear fuel pellet with improved thermal conductivity according to an embodiment of the present invention, the weight ratio of the spherical thermally conductive metal powder and the aluminum compound may be 99.95:0.05 to 99.5:0.5.

A nuclear fuel pellet comprising a plate-shaped coated thermally conductive metal array dispersed in an oxide nuclear fuel matrix according to the present invention, wherein the plate-shaped coated thermally conductive metal array is coated with an aluminum compound on all or part of a surface of the plate-shaped thermally conductive metal. As a result, due to the aluminum compound, the oxide nuclear fuel crystal grain size can be greatly grown in the periphery of the array during the heat treatment process, and accordingly, the oxide nuclear fuel as a whole The average and distribution of grain size can also be improved. Therefore, while minimizing the addition of heterogeneous materials, it is possible to maximize the thermal conductivity improvement effect by reducing the core temperature of the oxide nuclear fuel.

The nuclear fuel pellet according to the present invention can be easily applied to existing commercial nuclear fuel manufacturing facilities, while significantly improving nuclear fuel safety and performance under normal operation, transient and accident conditions.

1(a) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, plate-shaped Al ₂ O ₃ coated Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Example 1, and finally manufactured nuclear fuel. This is an optical micrograph showing the microstructure of the sintered body.
1(b) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, plate-shaped Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Comparative Example 1, and a microstructure of the final nuclear fuel pellet. This is an optical microscope picture.
Figure 2 is a graph showing the comparison of the crystal grain size of the peripheral portion of the metal particle and the whole.

While studying a method for maximizing the effect of improving the thermal conductivity of a nuclear fuel pellet to which heterogeneous materials are added, the present inventors, as an additive to oxide nuclear fuel powder, have found a plate-shaped coating in which an aluminum compound is coated on all or part of the surface of a plate-shaped thermally conductive metal. By using the thermally conductive metal powder, it was confirmed that the grain size of the oxide nuclear fuel can be greatly grown in the periphery of the array, and the present invention was completed.

Hereinafter, the present invention will be described in detail.

The present invention includes an oxide nuclear fuel matrix and a plate-like coated thermally conductive metal array dispersed in the matrix, wherein the plate-shaped coated thermally conductive metal array is coated with an aluminum compound on all or part of the surface of the plate-like thermally conductive metal. To provide a nuclear fuel pellet with improved thermal conductivity.

A nuclear fuel pellet having improved thermal conductivity according to the present invention includes an oxide nuclear fuel matrix and a plate-like coated thermally conductive metal array dispersed in the matrix.

Specifically, the oxide fuel matrix may include one or more selected from the group consisting of uranium oxide (UO ₂ ), plutonium oxide (PuO ₂ ), and thorium oxide (ThO ₂ ). In this case, the oxide nuclear fuel matrix is formed from the oxide nuclear fuel powder, and the oxide nuclear fuel powder is described later.

In addition, the plate-shaped coated thermally conductive metal array is characterized in that an aluminum compound is coated on all or part of the surface of the plate-shaped thermally conductive metal.

The term "disc, laminar or plate" in the present specification means a flat shape in contrast to a thin and elongated acicular shape (needle) or strip, and the plate shape has an average width to thickness It is characterized by having a large ratio and having a constant area in a plan view (top view).

On the other hand, when the aluminum compound coating is omitted in the plate-shaped coated thermally conductive metal array, the thermally conductive metal provides power during the heat treatment process to hinder the growth of oxide nuclear fuel crystal grains in its periphery. In order to improve this problem, However, it needs to be coated with an aluminum compound that affects oxide fuel grain growth.

The plate-like coated thermally conductive metal array has excellent interfacial integrity and is used as a heterogeneous material for growing the oxide nuclear fuel crystal grain size to a large extent at the periphery of the array. At this time, since the crystal grains of the oxide nuclear fuel are one of the important indicators for nuclear fuel performance, such as fission gas product release and in-furnace behavior, it is important to increase them and have a uniform microstructure. In addition, unlike the spherical shape, the plate-shaped thermally conductive metal array is characterized in that the ratio of the average width to the thickness is large. Since it is possible to form a continuous thermally conductive metal array, it has an advantage of excellent thermal conductivity improvement effect even with a small content.

With respect to the total weight of the matrix, the content of the plate-shaped coated thermally conductive metal array is preferably 1% to 5% by weight, but is not limited thereto. At this time, due to the aluminum compound, the plate-shaped coated thermally conductive metal array provides power during the heat treatment process to increase the size of oxide nuclear fuel crystal grains in the periphery of the array, and heat conduction of most of the nuclear fuel is mainly performed through molding and heat treatment. Since it is possible to form a continuous thermally conductive metal array in the horizontal direction, it has the advantage of maximizing the thermal conductivity improvement effect even with a small content.

In addition, in the plate-shaped coated thermally conductive metal array, the content of the aluminum compound may be 0.05 wt % to 0.5 wt % based on the total weight of the plate-shaped thermal conductive metal. At this time, when the content of the aluminum compound is too low, there is a problem in that the inhibition of grain size growth of the oxide nuclear fuel cannot be offset in the surrounding area during the heat treatment process. There is a problem that hinders nuclear fuel grain size growth.

Specifically, the plate-shaped thermal conductive metal is molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf), tantalum (Ta), It may include one or more selected from the group including rhodium (Rh) and zirconium (Zr), and may include an alloy based thereon. In addition, the aluminum compound is at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), aluminum metal salt, (Al(NO ₃ ) ₃ ) and (AlCl ₃ ), and aluminum hydroxide (Al(OH) ₃ ). It may include, and aluminum oxide (Al ₂ O ₃ ) is preferably one, but is not limited thereto.

Specifically, the ratio of average width to thickness of the plate-shaped coated thermally conductive metal array is preferably 10 to 300, but is not limited thereto. At this time, when the ratio of the average width to the thickness of the plate-shaped coated thermally conductive metal array is less than 10, it becomes a shape similar to a sphere, and there is a problem in that a continuous thermally conductive metal array in the horizontal direction cannot be formed even through molding and heat treatment, When the average width to thickness ratio of the plate-shaped coated thermally conductive metal array exceeds 300, the effect of increasing the thermal conductivity with respect to the increase in the average width to thickness ratio is insignificant, and cracks occur in the oxide fuel matrix during the sintering process. has a problem that causes

More specifically, the plate-shaped coated thermally conductive metal array may have an average width of 1 μm to 900 μm and a thickness of 0.1 μm to 3 μm. In particular, the average width of the plate-shaped coated thermally conductive metal array is preferably from 5 μm to 900 μm, and the thickness is preferably from 0.1 μm to 2 μm, but is not limited thereto. At this time, when the average width or thickness of the plate-shaped coated thermally conductive metal array is too small, there is a problem in that a continuous thermally conductive metal array cannot be formed in the horizontal direction even through molding and heat treatment, and the plate-shaped coated thermally conductive metal array If the average width or thickness is too large, cracks may occur in the oxide fuel matrix during the sintering process.

In addition, it is preferable that the average aspect ratio of the plate-shaped coated thermally conductive metal array plane is 1 to 5, but is not limited thereto. When the average aspect ratio of the plate-shaped coated thermally conductive metal arrangement plane is 5 or more, the shape is relatively needle-shaped or strip-like, and the effect of improving the thermal conductivity of the sintered nuclear fuel body is deteriorated.

The plate-shaped coated thermally conductive metal array may be distributed in a horizontal direction within the matrix to have orientation, thereby serving as an efficient passage for heat transferred in a horizontal direction within the nuclear fuel pellet.

The term "horizontal direction" in the present specification means a radial direction from the center in the nuclear fuel pellet, and refers to a direction in which heat conduction of the nuclear fuel is mainly performed. In addition, the term “orientation” in the present specification means a distribution preferentially skewed in a specific direction.

On the other hand, the nuclear fuel pellet with improved thermal conductivity according to the present invention comprises the steps of (a) preparing a plate-shaped coated thermally conductive metal powder coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal powder; and (b) mixing the plate-shaped coated thermally conductive metal powder prepared in step (a) with the oxide nuclear fuel powder, followed by molding and heat treatment. Each step will be described later.

The present invention comprises the steps of (a) preparing a plate-shaped coated thermally conductive metal powder coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal powder; and (b) mixing the plate-shaped coated thermally conductive metal powder prepared in step (a) with the oxide nuclear fuel powder, followed by molding and heat treatment.

First, the method for manufacturing a nuclear fuel pellet with improved thermal conductivity according to the present invention includes the step [step (a)] of preparing plate-shaped coated thermally conductive metal powder in which an aluminum compound is coated on all or part of the surface of the plate-shaped thermally conductive metal powder. do.

Specifically, the plate-shaped coated thermally conductive metal powder is prepared by coating an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal powder, and a known physical or chemical coating method known in the art may be employed.

According to one embodiment, the plate-shaped coated thermally conductive metal powder may be prepared after mixing the spherical thermally conductive metal powder and an aluminum compound, and in this case, a milling process may be used.

According to another embodiment, the preparation of the plate-shaped coated thermally conductive metal powder is performed by performing a milling process on the spherical thermally conductive metal powder to prepare the plate-shaped thermally conductive metal powder, and then performing a process of bringing aluminum into contact with a salt in which it is dissolved. can be coated. In this case, the aluminum-dissolved salt may be a conventional aluminum-dissolved salt that meets the purpose of preparing the thermally conductive metal powder of the present invention. In addition, by changing the above order, the aluminum compound is coated on the spherical thermally conductive metal powder first, and then the plate-shaped thermally conductive metal powder can be prepared through a milling process.

The average particle size of the spherical thermally conductive metal powder may be 0.1 μm to 50 μm, preferably 0.1 μm to 30 μm, but is not limited thereto. Specifically, the spherical thermally conductive metal powder is molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf), tantalum (Ta) , rhodium (Rh), and zirconium (Zr), and may include one or more selected from the group, and may include an alloy based thereon.

The aluminum compound is coated on all or part of the surface of the thermally conductive metal powder in the milling process, and serves to increase the size of oxide nuclear fuel crystal grains in the surrounding area by providing power in the heat treatment process. The average particle size of the aluminum compound may also be 0.1 μm to 50 μm, preferably 0.1 μm to 30 μm, but is not limited thereto. Specifically, the aluminum compound is one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), aluminum metal salt, (Al(NO ₃ ) ₃ ) and (AlCl ₃ ), and aluminum hydroxide (Al(OH) ₃ ). It may include the above, and it is preferable that it is aluminum oxide (Al ₂ O ₃ ), but is not limited thereto.

The weight ratio of the spherical thermally conductive metal powder and the aluminum compound may be 99.95:0.05 to 99.5:0.5. At this time, when the content of the aluminum compound is too low, there is a problem in that the inhibition of grain size growth of the oxide nuclear fuel cannot be offset in the surrounding area during the heat treatment process. There is a problem that hinders nuclear fuel grain size growth.

In addition, the milling process may employ a known milling process known in the art, such as an attrition mill, a ball mill, or a planetary mill. Through this milling process, the aluminum compound can be effectively adhered and coated on all or part of the surface of the relatively soft thermally conductive metal powder by generating contact and shear force between particles.

Thus, the plate-shaped coated thermally conductive metal powder may have an average width ratio to the thickness of the plate-shaped coated thermally conductive metal powder of 10 to 300, as described in the plate-shaped coated thermally conductive metal arrangement, and the plate-shaped coated thermally conductive metal powder The metal powder may have an average width of 1 μm to 900 μm, a thickness of 0.1 μm to 3 μm, and an average aspect ratio of the plane of the plate-shaped coated thermally conductive metal powder may be 1 to 5.

Next, the method for manufacturing a nuclear fuel pellet with improved thermal conductivity according to the present invention includes mixing the plate-shaped coated thermally conductive metal powder and the oxide nuclear fuel powder, followed by molding and heat treatment (step (b)).

Specifically, the oxide nuclear fuel powder is formed from an oxide nuclear fuel precursor, and means a state before performing a granulation process to be described later, and is a distinct concept. Specifically, it means that the average particle size of the oxide nuclear fuel powder is 0.1 μm to 50 μm. In the case of UO ₂ powder, it is formed from UF ₆ corresponding to its precursor through conventional manufacturing processes such as dry (DC) and wet (ADU, AUC) processes, but is not limited thereto.

An average particle size of the oxide nuclear fuel powder may be 0.1 μm to 50 μm, preferably 0.1 μm to 30 μm, but is not limited thereto. The average particle size of the oxide nuclear fuel powder is preferably smaller than or equal to the average width or thickness (in particular, width) of the plate-shaped coated thermally conductive metal powder in view of the horizontal arrangement of the plate-shaped coated thermally conductive metal powder, but is limited thereto. It doesn't work.

Specifically, the oxide nuclear fuel powder may include one or more selected from the group consisting of uranium oxide (UO ₂ ), plutonium oxide (PuO ₂ ), and thorium oxide (ThO ₂ ), and include uranium oxide (UO ₂ ). It is preferable to do it, but it is not limited thereto.

The weight ratio of the plate-shaped coated thermally conductive metal powder and the oxide nuclear fuel powder may be 1:99 to 5:95. At this time, the plate-shaped coated thermally conductive metal powder provides power during the heat treatment process due to the aluminum compound to increase the grain size of the oxide nuclear fuel in the periphery of the array, and heat conduction of most of the nuclear fuel is mainly performed through molding and heat treatment Since it is possible to form a continuous thermally conductive metal array in the horizontal direction, it has the advantage of maximizing the thermal conductivity improvement effect even with a small content.

In addition, the molding may be performed so that the plate-shaped thermally conductive metal powder has orientation in a horizontal direction, and is preferably performed through uniaxial pressing, but is not limited thereto. Specifically, the molding may be performed for 1 hour to 20 hours under a pressure of 100 MPa to 500 MPa.

The heat treatment is for preparing a nuclear fuel pellet, and may be performed at a temperature of 1300° C. to 1800° C. for 1 hour to 20 hours.

In addition, the present invention may provide a nuclear fuel including the nuclear fuel pellet having improved thermal conductivity and a nuclear fuel cladding tube in which a plurality of the nuclear fuel pellets are loaded.

In addition, the present invention comprises the steps of (a) preparing a plate-shaped thermally conductive metal powder coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal powder; and (b) mixing the plate-shaped coated thermally conductive metal powder prepared in step (a) with the oxide nuclear fuel powder, followed by molding and heat treatment.

As described above, in the nuclear fuel pellet including a plate-shaped coated thermally conductive metal array dispersed in an oxide nuclear fuel matrix according to the present invention, the plate-shaped coated thermally conductive metal array comprises an aluminum compound on all or part of the plate-shaped thermally conductive metal surface. This coating is characterized in that, due to the aluminum compound, the grain size of the oxide nuclear fuel can be greatly grown in the periphery of the array during the heat treatment process, and thus the entire oxide nuclear fuel The average and distribution of grain size can also be improved. Therefore, while minimizing the addition of heterogeneous materials, it is possible to maximize the thermal conductivity improvement effect by reducing the core temperature of the oxide nuclear fuel.

The nuclear fuel pellet according to the present invention can be easily applied to existing commercial nuclear fuel manufacturing facilities, while significantly improving nuclear fuel safety and performance under normal operation, transient and accident conditions.

Hereinafter, a preferred embodiment is presented to aid understanding of the present invention. However, the following examples are provided to more easily understand the present invention, and the content of the present invention is not limited by the following examples.

[Example]

Example 1

First, after mixing spherical Mo powder with an average particle size of about 45 ㎛ and Al ₂ O ₃ powder with an average particle size of about 0.1 ㎛ in a weight ratio of 99.85:0.15, a milling process using a planetary mill was performed to obtain Al ₂ O ₃ Coating plate-shaped Mo powder was prepared. At this time, the average width of the prepared Al ₂ O ₃ coated plate-shaped Mo powder was about 70 μm, the thickness was about 1 μm, and the aspect ratio was about 70.

In addition, as oxide nuclear fuel powder, UO ₂ powder having an average particle size of about 3 μm was prepared.

Thereafter, the plate-like Al ₂ O ₃ coated Mo powder and the UO ₂ powder were mixed in a weight ratio of 97.2:2.8, and then, in the prepared mixture, the Al ₂ O ₃ coated plate-like Mo powder was subjected to a pressure of about 400 MPa to have orientation in the horizontal direction. After uniaxial pressure molding, a nuclear fuel pellet (approximately 97% TD) was finally prepared by heat treatment at a temperature of approximately 1700° C. for approximately 4 hours under a hydrogen reducing atmosphere with a slight oxygen partial pressure (equivalent to 2% CO ₂ ).

1(a) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, plate-shaped Al ₂ O ₃ coated Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Example 1, and finally manufactured nuclear fuel. It is an optical micrograph showing the microstructure of the sintered body, and FIG. 2 is a graph showing the size of crystal grains around the metal particle and the whole.

As shown in FIGS. 1(a) and 2, the nuclear fuel pellet according to Example 1 includes Al ₂ O ₃ coated plate-like Mo metal particles that are horizontally dispersed and arranged in a UO ₂ matrix, and between the UO ₂ matrix and the metal particles It is confirmed that the interfacial integrity is excellent, and the UO ₂ crystal grain size of the metal particle periphery greatly increases by an average of 4 to 5 times compared to Comparative Examples 1 and 2 described later. Therefore, the average and distribution of the overall UO ₂ grain size can also be improved, and thus nuclear fuel safety and performance can be greatly improved.

Example 2

First, plate-shaped Mo powder was prepared by performing a milling process using a planetary mill on spherical Mo powder having an average particle size of about 45 μm. The prepared plate-like Mo powder had an average width of about 70 μm, a thickness of about 1 μm, and an aspect ratio of about 70. The resulting plate-shaped Mo powder was immersed in 20 ml of distilled water in which 1 mol/L aluminum nitrate (Al(NO ₃ ) ₃ -9H ₂ O) was dissolved, and coated by aluminum nitrate precipitation on the surface of the metal particles through a drying treatment. The amount of dissolved aluminum nitrate was carried out in a weight ratio of (98:2) to the metal powder.

Nuclear fuel pellets (97% TD) were manufactured in the same manner as in Example 1, except for using the aluminum metal salt-coated planar Mo metal particles thus prepared.

FIG. 1(b) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, aluminum nitrate-coated plate-shaped Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Example 2, and a final manufactured nuclear fuel pellet This is an optical micrograph showing the microstructure. Figure 2 is a graph showing the size of the crystal grain for the peripheral portion and the entire metal particle.

As shown in FIGS. 1(b) and 2 , it was confirmed that the nuclear fuel pellet according to Example 2 also had excellent interface integrity and an effect of increasing the size of UO ₂ crystal grains in the periphery.

Comparative Example 1

A nuclear fuel pellet (97% TD) was manufactured in the same manner as in Example 1, except that the use of Al ₂ O ₃ powder having an average particle size of about 0.1 μm was omitted.

1(c) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, plate-shaped Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Comparative Example 1, and a microstructure of the final nuclear fuel pellet. This is an optical microscope picture. Figure 2 is a graph showing the size of the crystal grain for the peripheral portion and the entire metal particle.

As shown in FIGS. 1(c) and 2 , the nuclear fuel pellet according to Comparative Example 1 includes a plate-shaped Mo array dispersed in a UO ₂ matrix, and it is confirmed that UO ₂ crystal grain growth is reduced in the periphery of the array. Therefore, there is a limit to improving nuclear fuel safety and performance.

Comparative Example 2

A nuclear fuel pellet was manufactured in the same manner as in Example 1, except that spherical Mo powder having an average particle size of about 45 μm and Al ₂ O ₃ powder having an average particle size of about 0.1 μm were mixed in a weight ratio of 99:1. .

1(d) is a scanning electron microscope (SEM) photograph showing spherical Mo powder, plate-shaped Mo powder, and UO ₂ powder used in the manufacture of a nuclear fuel pellet according to Comparative Example 1, and a microstructure of the final nuclear fuel pellet. This is an optical microscope picture. Figure 2 is a graph showing the size of the crystal grain for the peripheral portion and the entire metal particle.

As shown in FIGS. 1(d) and 2, the nuclear fuel pellet according to Comparative Example 2 includes a plate-shaped Mo array dispersed in a UO ₂ matrix, and an excessive amount of aluminum compound is added compared to Examples 1 and 2, resulting in UO ₂ It is judged that the effect of improving the grain size is reduced. Therefore, it can be seen that the addition of an aluminum compound has an effect in improving the grain size of UO ₂ , and it can be seen that the addition amount should be in an appropriate range.

The above description of the present invention is for illustrative purposes, and those skilled in the art 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, the embodiments described above should be understood as illustrative in all respects and not limiting.

Claims (10)

an oxide fuel matrix; and
comprising a coated thermally conductive plate-like metal array dispersed in the matrix;
The coated thermally conductive plate-like metal array is a nuclear fuel sintered body with improved thermal conductivity, characterized in that an aluminum compound is coated on all or part of the surface of the thermally conductive plate-like metal.
According to claim 1,
The coated thermally conductive plate-shaped metal array is dispersed to have orientation in a horizontal direction in the matrix, the nuclear fuel pellet having improved thermal conductivity.
According to claim 1,
Based on the total weight of the matrix, the content of the coated thermally conductive plate-like metal array is 1% to 5% by weight.
According to claim 1,
In the plate-shaped coated thermally conductive metal array, the content of the aluminum compound is 0.05% by weight to 0.5% by weight based on the total weight of the plate-shaped thermally conductive metal.
According to claim 1,
In the plate-shaped coated thermal conductive metal arrangement, the plate-shaped thermal conductive metal is molybdenum (Mo), chromium (Cr), tungsten (W), niobium (Nb), ruthenium (Ru), vanadium (V), hafnium (Hf) ), at least one selected from the group consisting of tantalum (Ta), rhodium (Rh) and zirconium (Zr), and the aluminum compound is aluminum oxide (Al ₂ O ₃ ), aluminum metal salt, (Al(NO ₃ ) ₃ ) and (AlCl ₃ ), and aluminum hydroxide (Al(OH) ₃ ), including at least one selected from the group consisting of, the nuclear fuel pellet with improved thermal conductivity.
According to claim 1,
The ratio of the average width to the thickness of the plate-shaped coated thermally conductive metal array is 10 to 300, the nuclear fuel pellet with improved thermal conductivity.
According to claim 1,
The aluminum compound has an average particle size of 0.1 μm to 50 μm, a nuclear fuel pellet with improved thermal conductivity.
(a) preparing a plate-shaped coated thermally conductive metal powder coated with an aluminum compound on all or part of the surface of the plate-shaped thermally conductive metal powder; and
(b) mixing the plate-shaped coated thermally conductive metal powder prepared in step (a) with the oxide nuclear fuel powder, followed by molding and heat treatment;
According to claim 8,
In the step (a), the plate-shaped coated thermally conductive metal powder,
A method of preparing through a milling process after mixing the spherical thermally conductive metal powder and the aluminum compound; Alternatively, a method of manufacturing a spherical thermally conductive metal powder by contacting it with an aluminum compound after performing a milling process; A method of manufacturing a nuclear fuel pellet with improved thermal conductivity, which is a thermally conductive metal powder produced by any one method selected from among.
According to claim 8,
The weight ratio of the spherical thermally conductive metal powder and the aluminum compound is 99.95: 0.05 to 99.5: 0.5, the manufacturing method of the nuclear fuel pellet with improved thermal conductivity.

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