U.S. patent application number 16/394322 was filed with the patent office on 2020-03-05 for nuclear fuel rod for fast reactors including metallic fuel slug coated with protective coating layer and fabrication method ther.
The applicant listed for this patent is Korea Atomic Energy Research Institute, Korea Hydro & Nuclear Power Co., Ltd.. Invention is credited to Jong-Hyuk Baek, Jin-Sik Cheon, Jun Hwan Kim, Junehyung Kim, Ki H. Kim, Sung-Ho Kim, Young-Mo Ko, Byoungoon Lee, Chan Bock Lee, Seok-Jin Oh, Yoon-Myeong Woo, Seong W. Yang.
Application Number | 20200075182 16/394322 |
Document ID | / |
Family ID | 51207677 |
Filed Date | 2020-03-05 |
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United States Patent
Application |
20200075182 |
Kind Code |
A1 |
Lee; Chan Bock ; et
al. |
March 5, 2020 |
NUCLEAR FUEL ROD FOR FAST REACTORS INCLUDING METALLIC FUEL SLUG
COATED WITH PROTECTIVE COATING LAYER AND FABRICATION METHOD
THEREOF
Abstract
Provided are a nuclear fuel rod for fast reactors that includes
a metallic fuel slug coated with a protective coating layer and a
fabrication method thereof. The nuclear fuel rod for fast reactors
that includes a surface treated metallic fuel slug and a cladding
tube according to the present invention has an excellent effect of
stabilizing components of the metallic fuel slug and fission
products or impurities, because the interdiffusion between the
metallic fuel slug and the cladding tube does not occur. Also,
since the uniform coating on the surface of the metallic fuel slug
may be facilitated and fabrication costs may be significantly
reduced in comparison to a typical technique of using a functional
material for preventing the interdiffusion at an inner surface of
the cladding tube, it may be suitable for fabricating the nuclear
fuel rod for fast reactors.
Inventors: |
Lee; Chan Bock; (Daejeon,
KR) ; Kim; Jun Hwan; (Daejeon, KR) ; Baek;
Jong-Hyuk; (Daejeon, KR) ; Cheon; Jin-Sik;
(Daejeon, KR) ; Lee; Byoungoon; (Daejeon, KR)
; Kim; Ki H.; (Daejeon, KR) ; Kim; Sung-Ho;
(Daejeon, KR) ; Kim; Junehyung; (Daejeon, KR)
; Oh; Seok-Jin; (Daejeon, KR) ; Ko; Young-Mo;
(Daejeon, KR) ; Woo; Yoon-Myeong; (Daejeon,
KR) ; Yang; Seong W.; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Korea Atomic Energy Research Institute
Korea Hydro & Nuclear Power Co., Ltd. |
Daejeon
Gyeongsangbuk-do |
|
KR
KR |
|
|
Family ID: |
51207677 |
Appl. No.: |
16/394322 |
Filed: |
April 25, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15412560 |
Jan 23, 2017 |
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16394322 |
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14079740 |
Nov 14, 2013 |
9589680 |
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15412560 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G21C 3/60 20130101; Y02E
30/40 20130101; G21C 1/02 20130101; Y02E 30/30 20130101; G21C 3/20
20130101; G21C 3/04 20130101; G21C 3/047 20190101; G21C 21/02
20130101 |
International
Class: |
G21C 3/20 20060101
G21C003/20; G21C 21/02 20060101 G21C021/02; G21C 3/60 20060101
G21C003/60; G21C 1/02 20060101 G21C001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2013 |
KR |
10-2013-0005989 |
Sep 13, 2013 |
KR |
10-2013-0110624 |
Claims
1. A fast reactor nuclear fuel element comprising: a metallic fuel
slug, the fuel slug consisting essentially of a uranium (U) and
zirconium (Zr) alloy; a protective coating layer of a nitride layer
or a carbide layer, the protective coating layer is coated on a
surface of the fuel slug, which causes the fuel slug to be coated
with the single protective coating layer of the nitride layer or
the carbide layer, the single protective coating layer is formed by
nitridation or caburization of the fuel slug, thickness of the
single protective coating layer is in a range of 0.5 .mu.m to 100
.mu.m, and the single protective coating layer is preformed on the
fuel slug surface prior to fuel slug usage in a fast reactor, the
single protective coating layer is configured to prevent
interdiffusion between the fuel slug and a cladding tube, to
prevent the cladding tube from thinning during fission operation in
the fast reactor.
2. A nuclear fuel rod configured for use with a fast reactor
comprising: a fast reactor nuclear fuel element of claim 1; and a
cladding tube sealing the metal fuel slug.
3. The nuclear fuel rod as set forth in claim 2, wherein the
cladding tube comprises one or more selected from the group
consisting of iron (Fe), chromium (Cr), tungsten (W), molybdenum
(Mo), vanadium (V), titanium (Ti), niobium (Nb), tantalum (Ta),
silicon (Si), manganese (Mn), nickel (Ni), carbon (C), nitrogen
(N), and boron (B).
Description
CROSS-REFERENCES TO RELATED APPLICATION
[0001] This patent application is a divisional application of U.S.
application Ser. No. 15/412,560, filed on Jan. 23, 2017, which is a
continuation application of U.S. application Ser. No. 14/079,740,
filed on Nov. 14, 2013, now U.S. Pat. No. 9,589,680, issued Mar. 7,
2017, which claims the benefit of priority from Korean Patent
Application No. 10-2013-0005989 filed on Jan. 18, 2013, and Korean
Patent Application No. 10-2013-0110624 filed on Sep. 13, 2013, the
contents of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a nuclear fuel rod for
fast reactors that includes a metallic fuel slug coated with a
protective coating layer and a fabrication method thereof.
BACKGROUND
[0003] The present invention relates to a process for improving the
performance of nuclear fuel for reactors, and more particularly, to
a technique that stabilizes components of a metallic fuel slug and
fission products or impurities through the stabilization of
surfaces of the metallic fuel slug and metallic fuel powder by a
surface treatment.
[0004] Nuclear fuel in fast reactors is designed in various types,
such as a plate type, a pellet type, and a rod type, and a
fissionable material that undergoes a nuclear reaction is included
in a nuclear fuel rod. The fissionable material is sealed by a
container, which is not reactive due to its good compatibility with
a coolant and has good heat transfer characteristics, i.e. a
cladding tube. The nuclear fuel rods being maintained at a constant
spacing are assembled in the form of a fuel assembly and the
assembly is charged into a nuclear reactor. In this case, the
cladding tube surrounding the fuel must prevent chemical
interactions between the fissionable material and the coolant by
blocking a direct contact therebetween and must prevent the leakage
of fission products. In addition, in fast reactors using metallic
nuclear fuel, it is highly advantageous in terms of the safety and
economic efficiency of nuclear fuel to also inhibit interactions
between the cladding tube and the fissionable material.
[0005] In particular, in fast reactors using metallic fuel, a
phenomenon occurs, in which a melting temperature of a metallic
fuel slug decreases or the strength of a cladding tube decreases by
the interpenetration between components (uranium (U), plutonium
(Pu), thorium (Th), minor actinides (MA), zirconium (Zr),
molybdenum (Mo), fission products, etc.) of the metallic fuel slug
and components (iron (Fe), chromium (Cr), tungsten (W), Mo,
vanadium (V), niobium (Nb), etc.) of the stainless steel cladding
tube by diffusion. Thus, the maximum allowable bumup and the
maximum allowable operating temperature of the metallic fuel for
fast reactors may be limited [J. Nucl. Mater., 204 (1993) p.
244-251 and J. Nucl. Mater., 204 (1993) p. 141-147].
[0006] Also, a diffusion couple experiment performed at 923 K by T.
Ogata et al. demonstrated the occurrence of a reaction due to the
interdiffusion between a metallic fuel slug and a cladding tube,
and reported that the thickness of an interaction layer increased
proportional to the reaction time [J. Nucl. Mater., 250 (1997) p.
171-175].
[0007] In order to prevent the interdiffusion reaction, General
Electric (GE) disclosed a technique for inhibiting the interaction
between a metallic fuel slug and a cladding tube by inserting an
about 50 .mu.m thick liner or sleeve formed of a metal of Zr,
titanium (Ti), Nb, and Mo between the metallic fuel slug and the
cladding tube.
[0008] Since the technique of GE essentially requires the
introduction of an additional process, the production of the
nuclear fuel rod may not only be complicated, but considerable
additional costs may also be required.
[0009] Also, in order to remove quartz tube mold waste generated
during the preparation of a fuel slug for fast reactors and
simultaneously, to inhibit a fuel-cladding chemical interaction
(FCCI) between metallic fuel slug and cladding tube, D. C. Crawford
et al. melt-casted an about 200 .mu.m thick zirconium tube and
reported the results of their experiments. However, cracks may
occur in the zirconium tube.
[0010] Metallic fuel for reactors has been considered important as
a nuclear fuel of sodium-cooled fast reactors, an advanced nuclear
fuel, due to high thermal conductivity and high nuclear
proliferation resistance in conjunction with pyroprocessing.
However, with respect to the metallic fuel, since metallic uranium
as a fuel material and a fuel cladding material interdiffuse and
react above 650.degree. C., i.e., an operating temperature of the
reactor, the thickness of a cladding tube decreases according to
the operating time. As a result, the lifetime of the cladding tube
may decrease due to the deterioration of the soundness thereof. In
order to prevent the interaction phenomenon and improve the
performance of the cladding material, research into using a
material for preventing the interdiffusion and reaction between the
fuel and the cladding tube has been conducted.
[0011] In Patent Document 1 (Korean Patent Application Laid-Open
Publication No. KR-2009-0018396), a nuclear fuel rod for fast
reactors, in which an oxide coating layer is formed on the inside
of a cladding tube, is suggested in order to inhibit the
fuel-cladding material interaction. Specifically, a concept of
attaching chromium oxide, vanadium oxide, and zirconium oxide to
the inside of the cladding tube by using an acid dissolution and
oxidation method, a high-temperature oxidation method, an
electrolytic oxidation method, and a vapor deposition method is
suggested.
[0012] In Patent Document 2 (Korean Patent Application Laid-Open
Publication No. KR-2010-0114392), a concept of depositing
functional materials, such as titanium, nickel, chromium, vanadium,
and zirconium, in multilayers is suggested in order to inhibit the
fuel-cladding material interaction and improve the performance of
the fuel cladding tube.
[0013] In Patent Document 3 (Korean Patent Application Laid-Open
Publication No. KR-2010-0081961), a method of uniformly plating an
inner wall of a fuel cladding tube and a concept of forming a
nitride layer on a surface of the plating layer through an
additional process of a nitridation treatment are suggested.
[0014] In Patent Document 4 (Japanese Patent Application Laid-Open
Publication No. 2012-237574), a typical main body that may
accommodate nuclear fuel and is formed of an iron-based material;
and a cladding tube including an inner layer part composed of a
carbon-based material that is formed on an inner circumferential
surface of the main body and a reactor including the cladding tube
are suggested in order to provide a cladding tube that may improve
high-temperature characteristics and power generation efficiency,
and a reactor including the cladding tube.
[0015] However, the fuel cladding tube for fast reactors is a
seamless tube having a diameter of 7 mm, a thickness of 0.6 mm, and
a length of 3,000 mm. Thus, there may be limitations in attaching
the functional material for preventing interdiffusion to the inside
of the thin and long tube, and treatment costs may be high.
[0016] Accordingly, the present inventors found that the
interdiffusion between a metallic fuel slug and a cladding tube may
be prevented by stabilizing components of the metallic fuel slug
and fission products or impurities though the simple and uniform
formation of an oxide layer, a nitride layer, or a carbide layer on
the surface of the metallic fuel slug, thereby leading to
completion of the present invention.
SUMMARY
[0017] One object of the present invention is to provide a metallic
fuel slug coated with a protective coating layer.
[0018] Another object of the present invention is to provide a
nuclear fuel rod for fast reactors including the metallic fuel
slug.
[0019] Still another object of the present invention is to provide
a method of fabricating the nuclear fuel rod for fast reactors.
[0020] In order to achieve the object, the present invention
provides a metallic fuel slug used in a nuclear fuel rod for fast
reactors, the metallic fuel slug having a surface coated with a
single protective coating layer selected from the group consisting
of an oxide layer, a nitride layer, and a carbide layer, wherein
the protective coating layer is formed by oxidation, nitridation,
or caburization of the metallic fuel slug.
[0021] The present invention also provides a nuclear fuel rod for
fast reactors including: a metallic fuel slug having a surface
coated with a single protective coating layer selected from the
group consisting of an oxide layer, a nitride layer, and a carbide
layer, wherein the protective coating layer is formed by oxidation,
nitridation, or caburization of the metallic fuel slug; and a
cladding tube sealing the metal fuel slug.
[0022] Furthermore, the present invention provides a method of
fabricating a nuclear fuel rod for fast reactors including: coating
a surface of a metallic fuel slug with a single protective coating
layer selected from the group consisting of an oxide layer, a
nitride layer, and a carbide layer by oxidation, nitridation, or
caburization of the metallic fuel slug (step 1); and sealing a
cladding tube after introducing the metallic fuel slug coated with
the protective coating layer in step 1 into the cladding tube (step
2).
[0023] The present invention also provides a method of fabricating
a nuclear fuel rod for fast reactors including: coating a surface
of metallic fuel powder with a single protective coating layer
selected from the group consisting of an oxide layer, a nitride
layer, and a carbide layer by oxidation, nitridation, or
caburization of the metallic fuel powder (step 1); preparing a
metallic fuel slug by forming the metallic fuel powder coated with
the protective coating layer in step 1 (step 2); and sealing a
cladding tube after introducing the metallic fuel slug prepared in
step 2 into the cladding tube (step 3).
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0025] FIG. 1 is a schematic view illustrating a metallic fuel slug
coated with a protective coating layer according to the present
invention;
[0026] FIG. 2 is a scanning electron microscope image of a cross
section of a nuclear fuel rod for fast reactors according to
Example 1 of the present invention after a diffusion couple
experiment;
[0027] FIG. 3 is a scanning electron microscope image of a cross
section of a nuclear fuel rod for fast reactors according to
Example 2 of the present invention after a diffusion couple
experiment;
[0028] FIG. 4 is a scanning electron microscope image of a cross
section of a nuclear fuel rod for fast reactors according to
Example 3 of the present invention after a diffusion couple
experiment;
[0029] FIG. 5 is a scanning electron microscope image of a cross
section of a nuclear fuel rod for fast reactors according to
Example 18 of the present invention after a diffusion couple
experiment; and
[0030] FIG. 6 is a scanning electron microscope image of a cross
section of a nuclear fuel rod for fast reactors according to
Comparative Example 1 of the present invention after a diffusion
couple experiment.
DETAILED DESCRIPTION
[0031] Features and advantages of the present invention will be
more clearly understood by the following detailed description of
the present preferred embodiments by reference to the accompanying
drawings. It is first noted that terms or words used herein should
be construed as meanings or concepts corresponding with the
technical sprit of the present invention, based on the principle
that the inventor can appropriately define the concepts of the
terms to best describe his own invention. Also, it should be
understood that detailed descriptions of well-known functions and
structures related to the present invention will be omitted so as
not to unnecessarily obscure the important point of the present
invention.
[0032] Hereinafter, the present invention will be described in
detail.
[0033] The present invention provides a metallic fuel slug used in
a nuclear fuel rod for fast reactors, the metallic fuel slug having
a surface coated with a single protective coating layer selected
from the group consisting of an oxide layer, a nitride layer, and a
carbide layer, wherein the protective coating layer is formed by
oxidation, nitridation, or caburization of the metallic fuel
slug.
[0034] In the metallic fuel slug coated with a protective coating
layer according to the present invention, since components of the
metallic fuel slug, fission products, or impurities are stabilized,
an interdiffusion phenomenon occurred between the metallic fuel
slug and the cladding tube sealing the metallic fuel slug during
the fabrication of the nuclear fuel rod for fast reactors may be
reduced. Also, according to the present invention, since a rare
earth element, which is included on the surface of a metallic fuel
fabricated by pyroprocessing to degrade the performance of the
metallic fuel, may be transformed into a non-active compound, such
as oxide, nitride, and carbide, the performance of the metallic
fuel may be improved.
[0035] With respect to the metallic fuel slug according to the
present invention, the metallic fuel slug may be fabricated by
including uranium (U), plutonium (Pu), thorium (Th), minor
actinides (MA, neptunium (Np), americium (Am), and curium (Cm)),
rare earth elements (RE, lanthanum (La), cerium (Ce), neodymium
(Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), europium
(Eu), and gadolinium (Gd)), zirconium (Zr), and molybdenum (Mo)
alone or in a mixture thereof. However, any metallic fuel slug
applicable to the nuclear fuel rod for fast reactors may be
used.
[0036] With respect to the metallic fuel slug according to the
present invention, a thickness of the protective coating layer may
be in a range of 0.5 .mu.m to 100 .mu.m.
[0037] In the case that the thickness of the protective coating
layer is less than 0.5 .mu.m, the interdiffusion phenomenon may not
be sufficiently inhibited. In the case in which the thickness of
the protective coating layer is greater than 100 .mu.m, since
thermal conductivity may decrease due to the thick coating layer,
heat discharged from the fuel may not be efficiently
transferred.
[0038] The present invention also provides a nuclear fuel rod for
fast reactors including a metallic fuel slug having a surface
coated with a single protective coating layer selected from the
group consisting of an oxide layer, a nitride layer, and a carbide
layer, wherein the protective coating layer is formed by oxidation,
nitridation, or caburization of the metallic fuel slug; and a
cladding tube sealing the metal fuel slug.
[0039] With respect to the nuclear fuel rod for fast reactors
according to the present invention, the metallic fuel slug may be
fabricated by including U, Pu, Th, MA (Np, Am, and Cm), RE (La, Ce,
Nd, Pr, Pm, Sm, Eu, and Gd), Zr, and Mo alone or in a mixture
thereof. However, any metallic fuel slug applicable to the nuclear
fuel rod for fast reactors may be used.
[0040] With respect to the nuclear fuel rod for fast reactors
according to the present invention, a thickness of the protective
coating layer may be in a range of 0.5 .mu.m to 100 .mu.m.
[0041] In the case that the thickness of the protective coating
layer is less than 0.5 .mu.m, the interdiffusion phenomenon may not
be sufficiently inhibited. In the case in which the thickness of
the protective coating layer is greater than 100 .mu.m, since
thermal conductivity may decrease due to the thick coating layer,
heat discharged from the fuel may not be efficiently
transferred.
[0042] With respect to the nuclear fuel rod for fast reactors
according to the present invention, the cladding tube may include
iron (Fe), chromium (Cr), tungsten (W), Mo, vanadium (V), titanium
(Ti), niobium (Nb), tantalum (Ta), silicon (Si), manganese (Mn),
nickel (Ni), carbon (C), nitrogen (N), and boron (B) alone or in
the form of an alloy by mixing thereof. However, the present
invention is not limited thereto.
[0043] Furthermore, the present invention provides a method of
fabricating a nuclear fuel rod for fast reactors including: coating
a surface of a metallic fuel slug with a single protective coating
layer selected from the group consisting of an oxide layer, a
nitride layer, and a carbide layer by oxidation, nitridation, or
caburization of the metallic fuel slug (step 1); and sealing a
cladding tube after introducing the metallic fuel slug coated with
the protective coating layer in step 1 into the cladding tube (step
2).
[0044] In the fabricating method according to the present
invention, step 1 is a step of forming the protective coating layer
on the surface of the metallic fuel slug. Specifically, an oxide,
nitride, or carbide coating layer may be formed on the surface of
the metallic fuel slug by oxidation, nitridation, or caburization
of the metallic fuel slug.
[0045] In the fabricating method according to the present
invention, step 2 is a step of sealing the cladding tube after
introducing the surface-treated metallic fuel slug into the
cladding tube.
[0046] Formation of Oxide Protective Coating Layer
[0047] A method of heat treating in a gas atmosphere containing
oxygen, a method of dipping in an oxidation solution, and a method
of performing an electrolytic treatment may be used as a method of
forming an oxide protective coating layer.
[0048] First, the method of heat treating in a gas atmosphere
containing oxygen may be performed by heat treating a metallic fuel
slug at a temperature ranging from 100.degree. C. to 1000.degree.
C. and a pressure ranging from 1 atm to 50 atm in an atmosphere of
oxygen, air, or inert gas containing oxygen.
[0049] In the case that the heat treatment temperature is less than
100.degree. C., the oxide layer may not be efficiently formed. In
the case in which the heat treatment temperature is greater than
1000.degree. C., transformation of the metallic fuel slug may occur
and thus, the performance of the metallic fuel slug as a fuel may
be degraded. Also, a pressurization treatment may be performed for
the efficient heat treatment. In the case that the pressure of the
heat treatment is 50 atm or more, an additional sealing apparatus
may be required, and thus, economic efficiency of the process may
be reduced.
[0050] Next, the method of dipping in an oxidation solution may be
performed by dipping a metallic fuel slug in a hydrochloric,
sulfuric, nitric, sodium hydroxide, or potassium hydroxide
solution, and heat treating the metallic fuel slug at a temperature
ranging from 30.degree. C. to 90.degree. C. for 30 minutes to 5
hours.
[0051] Finally, the method of performing an electrolytic treatment
may be performed by plasma electrolytic oxidation, micro-arc
oxidation, micro-arc discharge oxidation, spark anodizing, anodic
spark deposition, micro-arc anodizing, micro plasma anodizing,
micro plasma oxidation, and electro plasma oxidation of a metallic
fuel slug.
[0052] Formation of Nitride Protective Coating Layer
[0053] A method of heat treating in a gas atmosphere containing
nitrogen and an ion nitriding method may be used as a method of
forming a nitride protective coating layer.
[0054] First, the method of heat treating in a gas atmosphere
containing nitrogen may be performed by heat treating a metallic
fuel slug at a temperature ranging from 100.degree. C. to
1000.degree. C. and a pressure ranging from 1 atm to 50 atm in an
atmosphere of nitrogen, ammonia, or inert gas containing
nitrogen.
[0055] In the case that the heat treatment temperature is less than
100.degree. C., the nitride layer may not be efficiently formed. In
the case in which the heat treatment temperature is greater than
1000.degree. C., transformation of the metallic fuel slug may occur
and thus, the performance of the metallic fuel slug as a fuel may
be degraded. Also, a pressurization treatment may be performed for
the efficient heat treatment. In the case that the pressure of the
heat treatment is 50 atm or more, an additional sealing apparatus
may be required, and thus, economic efficiency of the process may
be reduced.
[0056] Next, the ion nitriding method may be performed by using a
method of applying a negative potential to an object to be
ion-nitrided in a gas atmosphere containing nitrogen. The ion
nitriding method may be completed by heat treating the object under
conditions of a temperature ranging from 100.degree. C. to
1000.degree. C., a pressure ranging from 1 atm to 50 atm, and a
potential ranging from 1 V to 1,000 V in an inert atmosphere
containing nitrogen. In the case that the heat treatment
temperature is less than 100.degree. C., the nitride layer may not
be efficiently formed. In the case in which the heat treatment
temperature is greater than 1000.degree. C., transformation of the
metallic fuel slug may occur and thus, the performance of the
metallic fuel slug as a fuel may be degraded. Also, a
pressurization treatment may be performed for the efficient heat
treatment. In the case that the pressure of the heat treatment is
50 atm or more, an additional sealing apparatus may be required,
and thus, economic efficiency of the process may be reduced. With
respect to the applied potential, efficient ion nitridation may not
be achieved at a potential of less than 1 V. Since an additional
insulation treatment may be required at a potential of greater than
1,000 V, economic efficiency of the process may be reduced.
[0057] Formation of Carbide Protective Coating Layer
[0058] A method of heat treating in a gas atmosphere containing
carbon may be used as a method of forming a carbide protective
coating layer.
[0059] The method of heat treating in a gas atmosphere containing
carbon may be performed by heat treating a metallic fuel slug at a
temperature ranging from 100.degree. C. to 1000.degree. C. and a
pressure ranging from 1 atm to 50 atm in an atmosphere of carbon,
methane, carbon dioxide, or carbon monoxide.
[0060] In the case that the heat treatment temperature is less than
100.degree. C., the carbide layer may not be efficiently formed. In
the case in which the heat treatment temperature is greater than
1000.degree. C., transformation of the metallic fuel slug may occur
and thus, the performance of the metallic fuel slug as a fuel may
be degraded. Also, a pressurization treatment may be performed for
the efficient heat treatment. In the case that the pressure of the
heat treatment is 50 atm or more, an additional sealing apparatus
may be required, and thus, economic efficiency of the process may
be reduced.
[0061] Also, the present invention provides a method of fabricating
a nuclear fuel rod for fast reactors including: coating a surface
of metallic fuel powder with a single protective coating layer
selected from the group consisting of an oxide layer, a nitride
layer, and a carbide layer by oxidation, nitridation, or
caburization of the metallic fuel powder (step 1); preparing a
metallic fuel slug by forming the metallic fuel powder coated with
the protective coating layer in step 1 (step 2); and sealing a
cladding tube after introducing the metallic fuel slug prepared in
step 2 into the cladding tube (step 3).
[0062] Since the method of fabricating a nuclear fuel rod for fast
reactors according to the present invention may form the protective
coating layer on the surface of the metallic fuel powder,
components of fuel, fission products, or impurities may be
stabilized and various types of fuels may be fabricated. In
particular, the coated metallic fuel powder may be formed in the
form of a metallic fuel slug during the fabrication of the nuclear
fuel rod for fast reactors and thus, the interdiffusion phenomenon
between the metallic fuel slug and the cladding tube sealing the
metallic fuel slug may be reduced.
[0063] In the fabricating method according to the present
invention, step 1 is a step of forming the protective coating layer
on the surface of the metallic fuel powder. Specifically, an oxide,
nitride, or carbide coating layer may be formed on the surface of
the metallic fuel powder by oxidation, nitridation, or caburization
of the metallic fuel powder. Preferred conditions that may form the
protective layers are as described in the above specification.
[0064] In the fabricating method according to the present
invention, step 2 is a step of preparing the metallic fuel slug by
forming the metallic fuel powder. Specifically, a method of
stacking the powder in a nuclear fuel rod composed of a cylindrical
cladding tube, a method of sintering the powder by heat treating in
a heat treatment furnace, and a method of forming a cylindrical
sintered body by introducing the metallic fuel powder into a metal
or ceramic matrix and heat treating.
[0065] In the fabricating method according to the present
invention, step 3 is a step of sealing the cladding tube after
introducing the metallic fuel slug into the cladding tube.
[0066] As described above, the nuclear fuel rod for fast reactors
that includes the surface treated metallic fuel slug and the
cladding tube according to the present invention has an excellent
effect of stabilizing components of the metallic fuel slug and
fission products or impurities, because the interdiffusion between
the metallic fuel slug and the cladding tube does not occur. Also,
since the uniform coating on the surface of the metallic fuel slug
may be facilitated and fabrication costs may be significantly
reduced in comparison to a typical technique of using a functional
material for preventing the interdiffusion at an inner surface of
the cladding tube, it may be suitable for fabricating the nuclear
fuel rod for fast reactors.
[0067] Hereinafter, the present invention will be described in more
detail according to examples. However, the following examples are
provided for illustrative purposes only, and the scope of the
present invention should not be limited thereto in any manner.
<Example 1> Fabrication 1 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0068] An oxide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 600.degree. C. and a
pressure of 5 atm for 2 hours in an argon gas atmosphere containing
20% oxygen. Then, the heat-treated metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 2> Fabrication 2 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0069] An oxide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 150.degree. C. and a
pressure of 1 atm for 1 hour in an air atmosphere. Then, the
heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 3> Fabrication 3 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0070] An oxide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 300.degree. C. and a
pressure of 1 atm for 1 hour in an air atmosphere. Then, the
heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 4> Fabrication 4 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0071] An oxide layer was formed on a surface of a metallic fuel
slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear
fuel material, in a hydrochloric acid solution at 50.degree. C. for
2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 5> Fabrication 5 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0072] An oxide layer was formed on a surface of a metallic fuel
slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear
fuel material, in a sulfuric acid solution at 50.degree. C. for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 6> Fabrication 6 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0073] An oxide layer was formed on a surface of a metallic fuel
slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear
fuel material, in a nitric acid solution at 50.degree. C. for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 7> Fabrication 7 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0074] An oxide layer was formed on a surface of a metallic fuel
slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear
fuel material, in a sodium hydroxide solution at 50.degree. C. for
2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 8> Fabrication 8 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0075] An oxide layer was formed on a surface of a metallic fuel
slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear
fuel material, in a potassium hydroxide solution at 50.degree. C.
for 2 hours. Then, the metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 9> Fabrication 9 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0076] An oxide layer was formed on a surface of a metallic fuel
slug through plasma electrolytic oxidation by dipping the metallic
fuel slug formed of U-10Zr, a nuclear fuel material, in a potassium
hydroxide solution and a sodium hydroxide solution, and then
applying a positive voltage of 200 V thereto. Then, the metallic
fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate
a nuclear fuel rod for fast reactors.
<Example 10> Fabrication 10 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0077] An oxide layer was formed on a surface of a metallic fuel
slug by micro-arc oxidation of the metallic fuel slug formed of
U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was
put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel
rod for fast reactors.
<Example 11> Fabrication 11 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0078] An oxide layer was formed on a surface of a metallic fuel
slug by micro-arc discharge oxidation of the metallic fuel slug
formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel
slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a
nuclear fuel rod for fast reactors.
<Example 12> Fabrication 12 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0079] An oxide layer was formed on a surface of a metallic fuel
slug by spark anodizing of the metallic fuel slug formed of U-10Zr,
a nuclear fuel material. Then, the metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 13> Fabrication 13 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0080] An oxide layer was formed on a surface of a metallic fuel
slug by anodic spark deposition of the metallic fuel slug formed of
U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was
put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel
rod for fast reactors.
<Example 14> Fabrication 14 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0081] An oxide layer was formed on a surface of a metallic fuel
slug by micro-arc anodizing of the metallic fuel slug formed of
U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was
put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel
rod for fast reactors.
<Example 15> Fabrication 15 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0082] An oxide layer was formed on a surface of a metallic fuel
slug by micro plasma anodizing of the metallic fuel slug formed of
U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was
put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel
rod for fast reactors.
<Example 16> Fabrication 16 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0083] An oxide layer was formed on a surface of a metallic fuel
slug by micro plasma oxidation of the metallic fuel slug formed of
U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was
put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel
rod for fast reactors.
<Example 17> Fabrication 17 of Nuclear Fuel Rod for Fast
Reactors Having Oxide Layer Formed on Surface
[0084] An oxide layer was formed on a surface of a metallic fuel
slug by electro plasma oxidation of the metallic fuel slug formed
of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug
was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear
fuel rod for fast reactors.
<Example 18> Fabrication 1 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0085] A nitride layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 800.degree. C. and a
pressure of 2 atm for 2 hours in a 100% pure ammonia gas
atmosphere. Then, the heat-treated metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 19> Fabrication 2 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0086] A nitride layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 500.degree. C. and a
pressure of 2 atm for 2 hours in a 100% pure ammonia gas
atmosphere. Then, the heat-treated metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 20> Fabrication 3 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0087] A nitride layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 300.degree. C. and a
pressure of 2 atm for 2 hours in a 100% pure ammonia gas
atmosphere. Then, the heat-treated metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 21> Fabrication 4 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0088] A nitride layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 150.degree. C. and a
pressure of 2 atm for 2 hours in a 100% pure ammonia gas
atmosphere. Then, the heat-treated metallic fuel slug was put into
a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for
fast reactors.
<Example 22> Fabrication 5 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0089] An ion-nitrided layer was formed on a surface of a metallic
fuel slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into a mixed gas containing 80% nitrogen and
20% argon gas, and heat treating the metallic fuel slug at a
temperature of 800.degree. C. and a negative voltage of 200 V for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 23> Fabrication 6 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0090] An ion-nitrided layer was formed on a surface of a metallic
fuel slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into a mixed gas containing 80% nitrogen and
20% argon gas, and heat treating the metallic fuel slug at a
temperature of 500.degree. C. and a negative voltage of 200 V for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 24> Fabrication 7 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0091] An ion-nitrided layer was formed on a surface of a metallic
fuel slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into a mixed gas containing 80% nitrogen and
20% argon gas, and heat treating the metallic fuel slug at a
temperature of 300.degree. C. and a negative voltage of 200 V for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 25> Fabrication 8 of Nuclear Fuel Rod for Fast
Reactors Having Nitride Layer Formed on Surface
[0092] An ion-nitrided layer was formed on a surface of a metallic
fuel slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into a mixed gas containing 80% nitrogen and
20% argon gas, and heat treating the metallic fuel slug at a
temperature of 150.degree. C. and a negative voltage of 200 V for 2
hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 26> Fabrication 1 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0093] A carbide layer was formed on a surface of a metallic fuel
slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into carbon powder and heat treating the
metallic fuel slug at a temperature of 700.degree. C. and a
pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel
slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a
nuclear fuel rod for fast reactors.
<Example 27> Fabrication 2 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0094] A carbide layer was formed on a surface of a metallic fuel
slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into carbon powder and heat treating the
metallic fuel slug at a temperature of 500.degree. C. and a
pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel
slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a
nuclear fuel rod for fast reactors.
<Example 28> Fabrication 3 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0095] A carbide layer was formed on a surface of a metallic fuel
slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into carbon powder and heat treating the
metallic fuel slug at a temperature of 300.degree. C. and a
pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel
slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a
nuclear fuel rod for fast reactors.
<Example 29> Fabrication 4 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0096] A carbide layer was formed on a surface of a metallic fuel
slug by introducing the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, into carbon powder and heat treating the
metallic fuel slug at a temperature of 150.degree. C. and a
pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel
slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a
nuclear fuel rod for fast reactors.
<Example 30> Fabrication 5 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0097] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 700.degree. C. and a
pressure of 1 atm for 2 hours in a methane gas atmosphere. Then,
the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 31> Fabrication 6 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0098] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 500.degree. C. and a
pressure of 1 atm for 2 hours in a methane gas atmosphere. Then,
the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 32> Fabrication 7 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0099] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 300.degree. C. and a
pressure of 1 atm for 2 hours in a methane gas atmosphere. Then,
the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 33> Fabrication 8 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0100] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 150.degree. C. and a
pressure of 1 atm for 2 hours in a methane gas atmosphere. Then,
the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo)
cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 34> Fabrication 9 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0101] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 700.degree. C. and a
pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 35> Fabrication 10 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0102] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 500.degree. C. and a
pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 36> Fabrication 11 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0103] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 300.degree. C. and a
pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 37> Fabrication 12 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0104] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 150.degree. C. and a
pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 38> Fabrication 13 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0105] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 700.degree. C. and a
pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 39> Fabrication 14 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0106] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 500.degree. C. and a
pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 40> Fabrication 15 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0107] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 300.degree. C. and a
pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Example 41> Fabrication 16 of Nuclear Fuel Rod for Fast
Reactors Having Carbide Layer Formed on Surface
[0108] A carbide layer was formed on a surface of a metallic fuel
slug by heat treating the metallic fuel slug formed of U-10Zr, a
nuclear fuel material, at a temperature of 150.degree. C. and a
pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere.
Then, the heat-treated metallic fuel slug was put into a HT9
(12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast
reactors.
<Comparative Example 1> Fabrication of Nuclear Fuel Rod for
Fast Reactors with No Surface Treatment
[0109] A surface treatment was not performed on a metallic fuel
slug formed of U-10Zr, a nuclear fuel material, and the metallic
fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate
a nuclear fuel rod for fast reactors.
<Experimental Example 1> Metallic Fuel Slug-Cladding Tube
Diffusion Couple Experiment
[0110] The following experiments were performed for evaluating the
interdiffusivity between the metallic fuel slug and the cladding
tube in the nuclear fuel rods for fast reactors fabricated in
examples.
[0111] Specifically, the nuclear fuel rods for fast reactors
fabricated in Examples 1, 2, 3, and 18, and Comparative Example 1
were cut to a length of 10 mm, and the 10 mm long nuclear fuel rods
were then cut in half in a radial direction. Then, metallic fuel
slug-cladding tube diffusion couple experiments were performed at
800.degree. C. for 25 hours. After the diffusion couple
experiments, bonded samples were cooled and cross sections of the
bonded samples were observed using a scanning electron microscope.
The results thereof are presented in FIGS. 2 to 6.
[0112] FIG. 2 is a scanning electron microscope image of the cross
section of the nuclear fuel rod for fast reactors according to
Example 1 of the present invention after the diffusion couple
experiment.
[0113] FIG. 3 is a scanning electron microscope image of the cross
section of the nuclear fuel rod for fast reactors according to
Example 2 of the present invention after the diffusion couple
experiment.
[0114] FIG. 4 is a scanning electron microscope image of the cross
section of the nuclear fuel rod for fast reactors according to
Example 3 of the present invention after the diffusion couple
experiment.
[0115] FIG. 5 is a scanning electron microscope image of the cross
section of the nuclear fuel rod for fast reactors according to
Example 18 of the present invention after the diffusion couple
experiment.
[0116] FIG. 6 is a scanning electron microscope image of the cross
section of the nuclear fuel rod for fast reactors according to
Comparative Example 1 of the present invention after the diffusion
couple experiment.
[0117] As illustrated in FIGS. 2 to 6, with respect to Example 1
(FIG. 2), Example 2 (FIG. 3), Example 3 (FIG. 4), and Example 18
(FIG. 5), it was observed that the interactions between the
metallic fuel slugs and the cladding tubes did not occur because
dense oxide layers and nitride layer were formed on the surfaces of
the metallic fuel slugs. In contrast, with respect to Comparative
Example 1 (FIG. 6), it may be observed that the metallic fuel slug
material and the cladding tube material were interdiffused and
reacted during the diffusion couple experiment.
[0118] Therefore, the nuclear fuel rod for fast reactors that
includes the surface treated metallic fuel slug and the cladding
tube according to the present invention had an excellent effect of
stabilizing components of the metallic fuel slug and fission
products or impurities, because the interdiffusion between the
metallic fuel slug and the cladding tube did not occur. Also, since
the uniform coating on the surface of the metallic fuel slug may be
facilitated and fabrication costs may be significantly reduced in
comparison to a typical technique of using a functional material
for preventing the interdiffusion at an inner surface of the
cladding tube, it may be suitable for fabricating the nuclear fuel
rod for fast reactors. Furthermore, according to the present
invention, since a rare earth element, which is included on the
surface of a metallic fuel fabricated by pyroprocessing to degrade
the performance of the metallic fuel, may be transformed into a
non-active compound, such as oxide, nitride, and carbide, the
improvement of the performance of the metallic fuel and the
extension of the lifetime of the metallic fuel may be expected.
[0119] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *