JP2019215301A - Fuel cladding tube and method for manufacturing fuel cladding tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cladding tube having environment resistance during normal operation and accident. According to an embodiment, a fuel cladding tube (100) for accommodating a nuclear fuel has a tubular shape, and a first composite material layer (110) in which long fibers of silicon carbide and a matrix of silicon carbide are composited. , The first composite material layer 110 is laminated directly outside the first composite material layer 110 so as to cover the first composite material layer 110, and the long carbon fibers and the silicon carbide matrix are laminated. And a second composite material layer 120 that is composited. Alternatively, the fuel cladding tube 100 includes a first composite material layer 110, an intermediate layer that is laminated radially outside the first composite material layer 110 to cover the first composite material layer 110, and an intermediate layer. The second composite material layer 120 laminated so as to cover the intermediate layer on the outer side in the radial direction may be included. [Selection diagram] Figure 2

Description

  Embodiments of the present invention relate to a fuel cladding tube and a method for manufacturing a fuel cladding tube.

  A pressurized water nuclear power plant (PWR) supplies thermal energy generated from fission reactions of nuclear fuel in a nuclear reactor to a steam turbine cycle via a steam generator provided in a primary cooling system, and generates electricity by a generator. Do. In a boiling water nuclear power plant (BWR), a nuclear reactor also serves as a portion corresponding to a steam generator of a PWR, and heat is supplied directly from the nuclear reactor to a turbine cycle.

  Here, uranium generally used as nuclear fuel is contained in a fuel cladding tube as a sintered body of uranium oxide (fuel pellet), and cooling water flows around the fuel cladding tube. A plurality of fuel cladding tubes and a channel box surrounding the fuel cladding tubes constitute a fuel assembly. In the fuel assembly, the cooling water efficiently flows around the fuel cladding tube.

In PWRs and BWRs, zirconium-based alloys are generally used for fuel cladding tubes. That is, zirconium has excellent corrosion resistance and a small neutron absorption cross-sectional area. Therefore, in PWR, a Sn—Fe—Cr—Zr alloy called Zircaloy-4, and in BWR, a Sn—Fe—Cr—Zr alloy called Zircaloy-2. -An Fe-Cr-Ni-Zr alloy is used. The zirconium in these zirconium-based alloys causes a reaction at ambient temperature to generate hydrogen with ambient moisture as shown in the following reaction formula (1).
Zr + 2H ₂ O → ZrO ₂ + 2H ₂ (1)

  Here, the reaction represented by the reaction formula (1) is an exothermic reaction, and the zirconium-based alloy promotes the oxidation reaction of the reaction formula (1) by the heat generated by the alloy itself, and dramatically increases at a high temperature of about 1000 ° C. or more. And the generation of hydrogen increases.

  When a zirconium-based alloy is exposed to such a high temperature in an environment where moisture is present in a nuclear reactor, a large amount of hydrogen is generated in a short time. If this hydrogen leaks from the containment vessel, the hydrogen may stay in the reactor building and cause a hydrogen explosion.

  For these reasons, the use of a silicon carbide ceramic material as a material for a fuel cladding tube has been studied because of its excellent heat and oxidation resistance and small neutron absorption cross section.

U.S. Pat. No. 6,226,342

  In the case of a silicon carbide ceramic material, it exhibits brittle fracture. For this reason, resistance to destruction is not always large. In addition, in the case of a silicon carbide ceramic material in which silicon carbide fibers are compounded, the breaking energy is higher than that in a case where silicon carbide fibers are not compounded, but strength, thermal conductivity, airtightness, and environmental resistance are high. Is reduced.

  As a fuel cladding tube, generation of hydrogen due to reaction with moisture can be suppressed, strength and breaking energy are compatible at a high level, high thermal conductivity, high airtightness that does not pass helium gas, etc. during normal operation and accidents In any case, it is necessary to have environmental resistance.

  Therefore, an embodiment of the present invention aims to provide a fuel cladding tube having environmental resistance during normal operation and during an accident.

  In order to achieve the above object, the present embodiment is directed to a cylindrical fuel cladding tube for storing nuclear fuel, wherein a first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are compounded. A layer of carbon long fiber and a matrix of silicon carbide, which are laminated directly on the first composite material layer so as to cover the first composite material layer on the radial outside of the first composite material layer; And a second composite material layer that has been composited.

  Further, the present embodiment is a tubular fuel cladding tube for storing nuclear fuel, wherein the first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are compounded, An intermediate layer laminated directly in contact with the first composite material layer so as to cover the first composite material layer on a radially outer side of the composite material layer, and the intermediate layer on a radially outer side of the intermediate layer. A second composite material layer laminated directly in contact with the intermediate layer so as to cover the composite layer and comprising a carbon long fiber and a silicon carbide matrix.

  Further, the present embodiment is a method for manufacturing a fuel cladding tube for manufacturing a cylindrical fuel cladding tube for storing nuclear fuel, wherein the first fiber is formed by compounding a silicon carbide matrix with a silicon carbide long fiber. A first composite material layer forming step of forming a composite material layer of the following, and after the first composite material layer forming step, by combining long fibers of carbon with a matrix of silicon carbide, the first composite material layer A second composite material layer forming step of forming a second composite material layer on a radially outer side, wherein the formation of the first composite material layer and the formation of each of the second composite material layers are performed chemically. At least one of a vapor deposition method and a chemical vapor infiltration method is used.

  Further, the present embodiment is a method for manufacturing a fuel cladding tube for manufacturing a cylindrical fuel cladding tube for storing nuclear fuel, wherein the first fiber is formed by compounding a silicon carbide matrix with a silicon carbide long fiber. A first composite material layer forming step of forming the first composite material layer, and an intermediate step of forming an intermediate layer of a single material outside the first composite material layer in the radial direction after the first composite material layer forming step. A second composite material layer forming a second composite material layer radially outside of the intermediate layer by forming a layer of carbon and compounding long fibers of carbon in a silicon carbide matrix after the intermediate layer forming step And forming at least one of a chemical vapor deposition method and a chemical vapor infiltration method for forming the first composite material layer and for forming each of the second composite material layers. It is characterized in.

  According to the embodiment of the present invention, it is possible to provide a fuel cladding tube having environmental resistance during normal operation and during an accident.

FIG. 2 is an exploded view showing a configuration of a fuel rod having a fuel cladding tube according to the first embodiment. It is a cross-sectional view showing the configuration of the fuel cladding tube according to the first embodiment. It is a flow figure showing the procedure of the manufacturing method of the fuel cladding tube concerning a 1st embodiment. It is a top view showing arrangement of the 1st long fiber for composite materials in formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube concerning a 1st embodiment. It is a top view showing arrangement of the 2nd long fiber for composite materials in formation of the 2nd composite material layer of a manufacturing method of a fuel cladding tube concerning a 1st embodiment. It is a perspective view showing the state after forming the preform by the 1st example in formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube concerning a 1st embodiment. It is a perspective view showing the state after formation of the preform by the 2nd example in the formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube concerning a 1st embodiment. It is a cross-sectional view showing a configuration of a fuel cladding tube according to a second embodiment. It is a flowchart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 2nd Embodiment. It is a cross-sectional view showing a configuration of a fuel cladding tube according to a third embodiment. It is a flow figure showing the procedure of the manufacturing method of the fuel cladding tube concerning a 3rd embodiment. It is a cross-sectional view showing a configuration of a fuel cladding tube according to a fourth embodiment. It is a flow figure showing the procedure of the manufacturing method of the fuel cladding tube concerning a 4th embodiment. It is a cross-sectional view showing a configuration of a fuel cladding tube according to a fifth embodiment. It is a flow figure showing the procedure of the manufacturing method of the fuel cladding tube concerning a 5th embodiment.

  Hereinafter, a fuel cladding tube and a method for manufacturing the fuel cladding tube according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar portions are denoted by the same reference numerals, and overlapping description will be omitted.

[First Embodiment]
FIG. 1 is an exploded view showing a configuration of a fuel rod having a fuel cladding tube according to the first embodiment. The fuel rod 10 includes a fuel cladding tube 100 according to the present embodiment, an upper end plug 3 and a lower end plug 4 attached to upper and lower open portions thereof, and a plurality of columnar fuel cells, for example, which are stacked in a longitudinal direction and are nuclear fuel. It has a fuel pellet 1 and a spring 2 for suppressing its vibration.

  The fuel cladding tube 100 is a cylindrical tube, and forms a closed space together with the upper end plug 3 and the lower end plug 4. Nuclear fuel is stored in this closed space. Note that, in relation to the present embodiment, the cross-sectional shapes of the fuel pellet 1 and the fuel cladding tube 100 are not limited to circular shapes. For example, the shape may be close to a square or a triangle.

  FIG. 2 is a cross-sectional view showing the configuration of the fuel cladding tube according to the first embodiment. The fuel cladding tube 100 has a first composite material layer 110 formed in a cylindrical shape, and a second cylindrical composite material layer 120 formed radially outside the first composite material layer 110. As shown in FIG. 2, the first composite material layer 110 and the second composite material layer 120 are laminated in the radial direction, and the outer surface of the first composite material layer 110 and the inner surface of the second composite material layer 120 are stacked. Are in contact with each other.

  The first composite material layer 110 has a plurality of first composite material long fibers 111 of silicon carbide (FIG. 4) and a first matrix (base material) 112 of silicon carbide (FIG. 4). The plurality of first composite long fibers 111 are composited in a matrix 112.

  The second composite material layer 120 has a plurality of second composite long fibers 121 of carbon (FIG. 5) and a second matrix (base material) 122 of silicon carbide (FIG. 5). The plurality of second long fibers for composite material 121 are composited in the second matrix 122.

  The outer diameter of the fuel cladding tube 100 is, for example, about 10 mm. The thickness of the fuel cladding tube 100 is determined in consideration of the required thickness for structural strength in consideration of the corrosion allowance and the upper limit value of the thickness in removing heat from nuclear fuel containing fission products to the outside. , 0.7 mm or more and about 1.2 mm or less.

  The thickness of the first composite material layer 110 is 0.2 mm or more in terms of mechanical properties and environmental resistance of the fuel cladding tube 100, and is 1 0.0 mm or less is preferable.

  In addition, the thickness of the second composite material layer 120 is 0.2 mm or more from the viewpoint of mechanical properties and environmental resistance in the fuel cladding tube 100, and a reinforcing mechanism by long fibers at the time of damage is sufficiently exhibited. Is preferably 0.6 mm or less.

  That is, the thickness of the first composite material layer 110 is 0.2 mm or more and 1.0 mm or less, and the thickness of the second composite material layer 120 is 0.2 mm or more and 0.6 mm or less and the first The thickness of the first composite material layer 110 and the second composite material layer 110 are set such that the thickness of the fuel cladding tube formed by the composite material layer 110 and the second composite material layer 120 is 0.7 mm or more and 1.2 mm or less. It is preferable to select the thickness of the composite material layer 120.

  FIG. 3 is a flowchart illustrating a procedure of a method of manufacturing a fuel cladding tube according to the first embodiment.

  When forming the second composite material layer 120 radially outside of the first composite material layer 110, first, the first composite material layer 110 is formed (Step S101), and then the second composite material layer is formed. 120 are formed (step S201).

  Regarding the formation of the first composite material layer 110 (step S101), first, the first preforming is performed using a fiber bundle of the first long fibers 111 for composite material (FIG. 4), which are long fibers of silicon carbide. The body 115 (FIG. 4) is formed (step S111). Specifically, first, a fiber bundle (yarn) in which a plurality of long fibers of silicon carbide are bundled is prepared. At this time, the number of long fibers in the fiber bundle is preferably 100 or more and 500 or less. Using the fiber bundle, for example, using a cylindrical preform forming guide 50 (FIGS. 6 and 7) made of a carbon-based material, a cylindrical first preform (fiber preform) ) 115 is formed.

  FIG. 4 is a plan view showing an arrangement of first composite material long fibers in the formation of the first composite material layer. The first composite material long fiber 111 has a first direction long fiber 111a arranged in a first direction and a second direction long fiber 111b arranged in a second direction. Each group of the first direction long fibers 111a is arranged in parallel with each other, that is, each group of the second direction long fibers 111b is arranged in parallel with each other on the radial outside. Note that FIG. 4 shows an example in which an interval is provided between each group of the first directional long fibers 111a and between each group of the second directional long fibers 111b. Good.

  The first direction and the second direction intersect with each other at an intersection angle Φ. By arranging the fuel cladding tubes 100 in two directions, it is possible to bear the stress in the axial direction and the circumferential direction of the fuel cladding tube 100, and to improve the strength in each direction. When the first direction is the circumferential direction and the second direction is the axial direction, or when the two directions are displaced by the same angle, the first direction is orthogonal to the second direction, that is, Φ is 90 degrees. .

  In FIG. 4, each group of the first direction long fibers 111a is arranged in parallel with each other, that is, each group of the second direction long fibers 111b is arranged in parallel with each other outside in the radial direction, Both are not formed in a so-called stitch shape. However, since the fuel cladding tube 100 is long, in the process of forming the first preform 115, the plurality of first directional long fibers 111a and the plurality of second directional long fibers 111b are bonded to each other. A stitch may be provided in a part to form a part or the like.

  FIG. 4 shows a case where the combination of the first direction long fibers 111a and the second direction long fibers 111b is one layer. The first preform 115 is formed by laminating one layer or a plurality of layers in the radial direction with a combination of the first long fibers 111a and the second long fibers 111b.

  FIG. 5 is a plan view showing the arrangement of second composite material long fibers in the formation of the second composite material layer. The second composite material long fiber 121 has a first direction long fiber 121a arranged in the first direction and a second direction long fiber 121b arranged in the second direction. Each group of the first direction long fibers 121a is arranged in parallel with each other, that is, each group of the second direction long fibers 121b is arranged in parallel with each other on the radial outside. The second preform 125 is the same as the first preform. However, it is not always necessary to use the same molding method as that of the first preform.

  FIG. 6 is a perspective view showing a state after the formation of the preform according to the first example in the formation of the first composite material layer. In the first example, the first direction is the circumferential direction of the fuel cladding tube 100, and the second direction is the axial direction of the fuel cladding tube 100.

  The first direction, which is the circumferential direction, can be realized by reducing the inclination angle of the spiral using, for example, a filament winding method. Alternatively, in order to form the fiber bundle completely in the circumferential direction, that is, to set the inclination angle to 0 degree, fiber bundles for the first direction, that is, for the circumferential direction are arranged in parallel in the axial direction, and the fiber bundle for the second direction, that is, for the shaft, A method of winding the fiber bundle for the circumferential direction while sandwiching the fiber bundle for the direction may be used. In this case, since a multilayer structure is realized at one time by this operation, it is necessary to know in advance how many turns will increase the thickness.

  Preferably, the first direction is within a range of ± 30 degrees with respect to the circumferential direction, and the second direction is within a range of ± 30 degrees with respect to the axial direction. If it is 30 degrees, the cosine of 30 degrees is about 0.86, and it is possible to secure the strength in almost the desired direction. That is, if the composite can be formed in this range, the strength characteristics required for the fuel cladding structural member can be sufficiently exhibited.

  Since the reinforcing directions of the long fibers of the first direction long fibers 111a and the second direction long fibers 111b are arranged in the same layer in the circumferential direction and the axial direction, the matrix between the fiber bundles is also continuous in the thickness direction. Formed. Thereby, the thermal conductivity in the thickness direction of the fuel cladding tube can provide a structure utilizing the excellent thermal conductivity of silicon carbide in the matrix.

  FIG. 7 is a perspective view showing a state after the formation of the preform according to the second example in the formation of the first composite material layer. In the second example, the first direction is a direction having an angle with respect to the circumferential direction of the fuel cladding tube 100. That is, it is spirally wound along the outer surface of the preformed body forming guide 50. The second direction is a direction having an angle with respect to the circumferential direction of the fuel cladding tube 100, but is a direction facing the opposite side to the first direction when viewed in the circumferential direction. That is, it is spirally wound along the outer surface of the preformed body forming guide 50 toward the side opposite to the first direction when viewed in the circumferential direction. That is, the first direction long fibers 111a and the second direction long fibers 111b intersect at a certain intersection angle Φ as shown in FIG.

  In addition, as a manufacturing method of the fiber preform, a filament winding method and a braiding method can be used.

  A fiber bundle of long fibers of silicon carbide is arranged around a cylindrical preformed body forming guide 50 in a uniform direction, wound up to a predetermined thickness, and then solidified. Thereafter, the preform forming guide 50 is removed, for example, after the formation of the first preform 115 or after the formation of the first composite material layer 110.

  As a result, the first composite material long fiber 111 has a predetermined thickness in the radial direction by laminating a single layer or a plurality of layers of the combination of the first direction long fiber 111a and the second direction long fiber 111b. Is formed. The predetermined thickness in the radial direction is set in consideration of the final thickness of the first composite material layer 110, the thickness of the matrix material attached to the inside and outside of the first preform 115 in the radial direction, and the like.

  Next, the first matrix 112 is formed on the first preform 115 formed in step S111 (step S121). The first matrix 112 is made of silicon carbide.

  The formation of the first matrix 112 is performed by at least one of a chemical vapor deposition method and a chemical vapor infiltration method, and both may be used. For example, the first matrix 112 is formed between the first composite material long fibers 111 constituting the first preform 115 by a chemical vapor infiltration method, and if necessary, the first matrix 112 is formed. The matrix may be formed by a chemical vapor deposition method so that the periphery of the preform 115 is covered with the matrix.

  When the matrix is formed by the precursor impregnation firing method (PIP), fine cracks occur in the matrix due to shrinkage due to firing. Further, the formed silicon carbide matrix is amorphous silicon carbide (Si-CO) and contains oxygen. For this reason, in order to secure airtightness and high thermal conductivity in the fuel cladding tube 100, it is better to form the matrix by a chemical vapor deposition method or a chemical vapor infiltration method instead of the precursor impregnation firing method (PIP). preferable.

  As described above, by forming the first matrix 112 on the first preform 115, the first composite material layer 110 is formed.

  Next, regarding the formation of the second composite material layer 120 (Step S201), first, a second preform 125 (FIG. 5) is formed using a fiber bundle of carbon long fibers (Step S211). . Specifically, a fiber bundle (yarn) in which a plurality of carbon long fibers are bundled is prepared. At this time, the number of long fibers in the fiber bundle is preferably 100 or more and 500 or less. By using the fiber bundle, a cylindrical second preparatory layer is formed on the outer surface of the first composite material layer 110 so as to cover the first composite material layer 110 and contact the first composite material layer 110. A molded body (fiber preform) 125 is formed.

  Similarly to the first preformed body 115, the second preformed body 125 includes a single layer of long fibers arranged in the first direction and the second direction or a plurality of layers laminated in the radial direction. Form.

  Next, the second matrix 122 is formed on the second preform 125 formed in step S211 (step S221). The second matrix 122 is made of silicon carbide. The formation of the second matrix 122 is performed in the same manner as in the case of the first composite material layer 110.

  Silicon carbide long fibers have higher resistance in an environment having a high atmospheric temperature, for example, exceeding 400 ° C., than carbon long fibers. The long fibers of silicon carbide have a tensile strength of 2 to 4 GPa and a tensile modulus of 150 to 400 GPa. Therefore, the first composite material layer 110 using the first long fiber for composite material 111, which is a long fiber of silicon carbide, is particularly effective under high temperature conditions such as at the time of an accident.

  On the other hand, carbon long fibers have higher resistance in an environment exposed to water at about 400 ° C. or lower than silicon carbide long fibers. The long fibers of carbon have a tensile strength of 1 to 7 GPa and a tensile modulus of 30 to 950 GPa. Therefore, the second composite material layer 120 using the second long fiber for composite material 121, which is a long fiber of carbon, exhibits an effect particularly under operating conditions mainly in normal operation.

  As described above, the thickness of the first composite material layer 110 is 0.2 mm or more and 1.0 mm or less, and the thickness of the second composite material layer 120 is 0.2 mm or more and 0.6 mm or less, and The first composite material layer 110 has a total thickness of the fuel cladding tube 100 formed by the first composite material layer 110 and the second composite material layer 120 of 0.7 mm or more and 1.2 mm or less. And the thickness of the second composite material layer 120 are preferably selected.

  Under such conditions, the first composite material layer 110 and the second composite material can be used in accordance with a policy of how to balance environmental resistance and mechanical properties during normal operation and accident. The layers 120 can be laminated by appropriately setting the thickness of each layer. In addition, by using at least one of the chemical vapor deposition method and the chemical vapor infiltration method to form the matrix, airtightness and high thermal conductivity can be ensured.

  In this manner, the first composite material layer 110 in which the first composite material long fiber 111 of silicon carbide is compounded with the first matrix 112 of silicon carbide, and the second matrix 122 of silicon carbide is formed with the second matrix 122 of silicon carbide. By constructing the fuel cladding tube 100 with a laminated structure of the second composite material layer 120 in which the composite long fibers 121 are composited, the environmental resistance and mechanical properties can be improved over a wide range of environmental conditions. Can be realized.

  The long fiber reinforced silicon carbide member used for manufacturing the fuel cladding tube 100 according to the present embodiment can be used for materials such as a channel box constituting a fuel assembly, a tie plate for fixing a fuel rod, and a structural material for a control rod. it can.

  As described above, the fuel cladding tube and the method for manufacturing the fuel cladding tube according to the present embodiment can provide a fuel cladding tube having environmental resistance during normal operation and during an accident.

[Second Embodiment]
FIG. 8 is a cross-sectional view showing the configuration of the fuel cladding tube 101 according to the second embodiment. The second embodiment is a modification of the first embodiment. In the present second embodiment, an intermediate layer 130 is provided radially outside the first composite material layer 110 and radially inside the second composite material layer 120. The first composite material layer 110 and the intermediate layer 130 and the intermediate layer 130 and the second composite material layer 120 are in close contact with each other. Other than that, it is the same as the first embodiment.

  The intermediate layer 130 is formed of, for example, any one of a material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chromium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon carbide. .

  The intermediate layer 130 preferably has a thickness of 0.01 mm or more and 0.1 mm or less. In order to sufficiently exhibit different mechanical properties between the first composite material layer 110 and the second composite material layer 120, it is preferable that the intermediate layer 130 be equal to or more than the lower limit of the above range. In addition, from the viewpoint of the mechanical strength characteristics of the fuel cladding tube 100, it is preferable that the intermediate layer 130 has an upper limit of the above range or less. For this reason, the thickness of the intermediate layer 130 is more preferably in the range of 0.02 mm or more and 0.05 mm or less.

  The intermediate layer 130 is a layer having anisotropy in which the strength differs in the length direction (axial direction) and the circumferential direction in the fuel cladding tube 101. The intermediate layer 130 is more preferably a monoclinic crystal having a hexagonal or pseudo-hexagonal crystal form. In this case, the crystal face of the hexagonal crystal constituting the intermediate layer 130 slips. For this reason, it is possible to suppress the crack from developing in each of the first composite material layer 110 and the second composite material layer 120. As a result, the mechanical characteristics of the fuel cladding tube 101 can be further improved. In particular, for ternary carbides (for example, titanium aluminum carbide, vanadium aluminum carbide, chromium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, titanium silicon carbide), the crystal form is more preferably hexagonal.

  The intermediate layer 130 may be configured by stacking a plurality of the single layers, in addition to the case where the single layer of the specific material is one. For example, the intermediate layer 130 may be formed by sequentially laminating a single layer of carbon and a single layer of titanium silicon carbide.

  FIG. 9 is a flowchart illustrating a procedure of a method of manufacturing the fuel cladding tube 101 according to the second embodiment. In the method for manufacturing the fuel cladding tube 101 according to the present embodiment, after the first composite material layer forming step S101 and before the second composite material layer forming step S202, an intermediate layer forming step S301 is performed. I do.

  Step S101 of forming the first composite material layer is the same as in the first embodiment.

  In the formation step S301 of the intermediate layer, a single layer of a predetermined material is formed on the outer side in the radial direction of the first composite material layer 110 (step S311). The intermediate layer 130 is formed by one kind of single layer or by stacking a plurality of kinds of single layers.

  The intermediate layer 130 is formed by a vacuum vapor deposition (Vacuum Vapor Deposition) method, an ion plating method, a sputtering method, a plasma CVD (Chemical Vapor Deposition) method, a thermal CVD method, an optical CVD method, and a metal organic chemical vapor deposition (Metal Organic CVD) method. The film formation method such as the method is performed. Among them, the thermal CVD method is preferable because the formation of the first composite material layer 110 and the formation of the intermediate layer 130 can be continuously performed by switching the source gas.

  Next, the second composite material layer 120 is formed (Step S202). First, the second preform 125 is formed on the outer peripheral surface of the intermediate layer 130 (Step S212). Next, the second matrix 122 is formed on the second preform 125 formed in step S212 (step S222). Specifically, it is performed in the same manner as in the first embodiment. As described above, the fuel cladding tube 101 of the present embodiment is completed.

  In the present embodiment, the mechanical properties in the reinforcing direction by the long fibers are further improved by material design utilizing the fact that the intermediate layer 130 formed of this specific material has different strengths in the length direction, the circumferential direction, and the thickness direction. be able to.

[Third Embodiment]
FIG. 10 is a cross-sectional view showing the configuration of the fuel cladding tube 102 according to the third embodiment. The third embodiment is a modification of the first embodiment. In the present embodiment, an outer surface material layer 140 of silicon carbide ceramic is further provided radially outside the second composite material layer 120. The present embodiment is the same as the first embodiment except for the points related to this.

  The outer surface material layer 140 preferably has a thickness of 0.2 mm or more and 0.4 mm or less. If the outer surface material layer 140 is thinner than the lower limit of the above range, the fuel cladding tube 102 may not be able to maintain sufficient environmental resistance and airtightness, and in order to ensure a stable design strength in strength. The mechanical properties of the initial strength may be insufficient. When the outer surface material layer 140 is thicker than the upper limit of the above range, the proportion of the first composite long fiber 111 and the second composite long fiber 121 in the entire fuel cladding tube 102 is relatively small. Therefore, the mechanical properties of the fuel cladding tube 102 with respect to the breaking energy may be insufficient.

  FIG. 11 is a flowchart illustrating a procedure of a method of manufacturing the fuel cladding tube 102 according to the third embodiment. The step in which the step S201 for forming the second composite material layer 120 is performed after the step S101 for forming the first composite material layer 110 is the same as in the first embodiment.

  In the present embodiment, the outer surface material layer 140 is formed after the step S201 of forming the second composite material layer 120 (step S401). Specifically, the outer surface material layer 140 is formed of a single substance of the silicon carbide ceramic material by a chemical vapor deposition method (Step S411).

  The fuel cladding tube 102 according to the present embodiment formed as described above has a radially outer surface covered with the outer surface material layer 140, so that the corrosion thinning amount is reduced and the environmental resistance is reduced. The improvement can be realized more easily. Further, since dense silicon carbide is formed by a chemical vapor deposition method, high airtightness that suppresses passage of helium gas can be realized.

[Fourth Embodiment]
FIG. 12 is a cross-sectional view showing the configuration of the fuel cladding tube 103 according to the fourth embodiment. This embodiment is a modification of the third embodiment. In the third embodiment, an outer surface material layer 140 is formed radially outside the second composite material layer 120. On the other hand, in the fourth embodiment, an inner surface material layer 150 is formed radially inside the first composite material layer 110.

  That is, in the fuel cladding tube 102 in the third embodiment, the outer surface material layer 140 is formed on the outer surface in the radial direction, whereas in the fuel cladding tube 103 in the fourth embodiment, An inner surface material layer 150 of silicon carbide ceramic is formed on a radially inner surface.

  FIG. 13 is a flowchart illustrating a procedure of a method of manufacturing the fuel cladding tube 103 according to the fourth embodiment. In the method of manufacturing the fuel cladding tube 103 according to the present embodiment, first, the inner surface material layer 150 is formed (Step S501). More specifically, the inner surface material layer 150 is formed of a single silicon carbide ceramic material by a chemical vapor deposition method (step S511).

  After that, the first composite material layer 110 is formed (Step S102). That is, the first preform 115 is formed radially outside the inner surface material layer 150 (step S112), and the first matrix 112 is formed in the first preform 115 (step s122). After that, the second composite material layer 120 is further formed (Step S201).

  As described above, in the present embodiment, the innermost layer of the fuel cladding tube 103 is the inner surface material layer 150. That is, since the inner surface of the fuel cladding tube 103 is covered with the inner surface material layer 150, the resistance to outgas, which is a fission product released from the fuel pellet 1, is increased, and high airtightness can be secured.

[Fifth Embodiment]
FIG. 14 is a cross-sectional view showing the configuration of the fuel cladding tube 104 according to the fifth embodiment. The fifth embodiment is a combination of the second embodiment and the third embodiment. That is, in the fuel cladding tube 104 according to the fifth embodiment, the first composite material layer 110, the intermediate layer 130, the second composite material layer 120, and the outside are arranged from the radial inside to the radial outside. The surface material layers 140 are stacked in this order.

  FIG. 15 is a flowchart illustrating a procedure of a method of manufacturing a fuel cladding tube according to the fifth embodiment. First, the first composite material layer 110 is formed (Step S101). Next, the intermediate layer 130 is formed on the radially outer surface of the first composite material layer 110 (Step S301). The formation of a specific single layer (step S311) is the same as in the second embodiment.

  Next, the second composite material layer 120 is formed on the radially outer surface of the intermediate layer 130 (Step S202). Then, after the step S20 of forming the second composite material layer 120, the outer surface material layer 140 is formed (step S401).

  In the fuel cladding tube 104 according to the present embodiment formed as described above, the operation relating to the fuel cladding tubes 100, 101, and 102 in the first embodiment, the second embodiment, and the third embodiment, respectively, Has an effect.

  That is, the first composite material layer 110 in which the first composite material long fiber 111 of silicon carbide is compounded with the first matrix 112 of silicon carbide, and the second matrix 122 of carbon is formed with the second matrix 122 of silicon carbide. By constructing the fuel cladding tube 104 in a laminated structure with the second composite material layer 120 in which the composite long fibers 121 are composited, the environmental resistance and the mechanical properties are improved over a wide range of environmental conditions. be able to. In addition, the material design utilizing the fact that the intermediate layer 130 formed of a specific material has different strengths in the length direction, the circumferential direction, and the thickness direction can further improve the mechanical properties in the reinforcing direction of the long fibers. Furthermore, since the outer surface in the radial direction is covered with the outer surface material layer 140, the amount of corrosion loss is reduced, and the improvement of environmental resistance can be more easily realized. In addition, since dense silicon carbide is formed by a chemical vapor deposition method, high airtightness that does not pass helium gas can be realized.

[Other Embodiments]
While some embodiments of the present invention have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. For example, in the embodiment, the case where the fuel cladding tube 100 contains uranium fuel as nuclear fuel has been described as an example, but the invention is not limited to this. For example, it may be a plutonium fuel, a mixed oxide fuel of uranium and plutonium, or a case other than an oxide such as a carbide or a nitride. Moreover, in the embodiment, the case where the coolant is light water in the fuel cladding tube 100 has been described as an example, but the fuel cladding tube 100 is not limited to this. For example, a gas cooling furnace such as helium gas or carbon dioxide gas, or a liquid metal cooling furnace containing sodium or lead may be used.

  Further, the features of each embodiment may be combined. For example, the third embodiment and the fourth embodiment may be combined.

  Furthermore, these embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  Hereinafter, embodiments of the present invention will be specifically described with reference to five examples and comparative examples thereof, but the embodiments of the present invention are not limited to these examples.

  Examples 1 to 5 described below correspond to the first to fifth embodiments, respectively.

[Example 1]
In Example 1, when producing the fuel cladding tube 100, first, a first preform 115 (preform) constituting the first composite material layer 110 was formed. In this step, first, carbon was coated on the surface of a long fiber of silicon carbide having a diameter of 12 μm (trade name: Hynicalon (registered trademark) type S, manufactured by Nippon Carbon) by CVD. Then, a cylindrical preform (thickness: 0.5 mm) was produced by a filament winding method using a fiber bundle (yarn) obtained by bundling 500 first composite material long fibers 111.

  Next, a matrix, that is, a first matrix 112 was formed on the preformed body of the first composite material layer 110, that is, the first preformed body 115. In this step, after the first preform 115 is set inside a carbon mold in a chemical vapor reactor, the temperature is 1300 to 1400 ° C. and the pressure is 4 to 100 kPa. Source gases (silicon tetrachloride gas, propane gas, hydrogen gas) were introduced into the reactor. Thus, a first matrix 112 containing silicon carbide as a main component was formed in the first preform 115 to prepare a first composite material layer 110 having a thickness of 0.5 mm. Here, the first matrix 112 is formed by the chemical vapor infiltration method between one composite long fiber 111 constituting the first preform 115 of the first composite material layer 110, and the first matrix 112 is formed. The first matrix 112 was formed by a chemical vapor deposition method so that the periphery of the preform 115 was covered with the first matrix 112.

  Next, a second preform 125 that forms the second composite material layer 120 was formed. In this step, first, carbon was coated on the surface of carbon long fiber having a diameter of 10 μm (trade name: Torayca (registered trademark) M60, manufactured by Toray) by CVD. Then, a fiber bundle (yarn) obtained by bundling 3000 second long fibers 121 for a composite material is separated, and a fiber bundle having 500 fibers is formed into a cylindrical shape having a thickness of 0.5 mm by a filament winding method. Was formed on the outer peripheral surface of the first composite material layer 110.

  Next, a second matrix 122 was formed on the second preform 125 of the second composite material layer 120. In this step, after setting the second preform 125 in a carbon mold in a chemical vapor reactor, the temperature is 1300 to 1400 ° C. and the pressure is 4 to 100 kPa, Source gases (silicon tetrachloride gas, propane gas, hydrogen gas) were introduced into the reactor. As a result, the second composite material layer 120 having a thickness of 0.5 mm was formed by forming the second matrix 122 mainly containing silicon carbide on the second preform 125. Here, similarly to the case of the first composite material layer 110, the chemical vapor infiltration between the second composite material long fibers 121 constituting the second preform 125 of the second composite material layer 120 is performed. The second matrix 122 was formed by a chemical vapor deposition method so that the second matrix 122 was formed so as to cover the periphery of the second preform 125 by the method. Thus, the fuel cladding tube 100 of Example 1 was completed.

[Example 2]
In Example 2, as in Example 1, after preparing the first composite material layer 110, the intermediate layer 130 was formed on the outer peripheral surface of the first composite material layer 110. Here, the intermediate layer 130 was formed by forming a single layer of carbon (C) (having a thickness of 0.1 mm). After that, as in the case of Example 1, the second composite material layer 120 was formed on the outer peripheral surface of the first composite material layer 110 via the intermediate layer 130. Thus, the fuel cladding tube 101 of Example 2 was completed.

[Example 3]
In the third embodiment, similarly to the first embodiment, after preparing the first composite material layer 110 having a thickness of 0.4 mm, the second composite material layer 110 having a thickness of 0.4 mm is formed on the outer peripheral surface of the first composite material layer 110. A composite material layer 120 was formed. Thereafter, an outer surface material layer 140 was formed on the outer peripheral surface of the second composite material layer 120. The outer surface material layer 140 was formed by forming a single layer of silicon carbide (thickness: 0.2 mm) by chemical vapor deposition. Thus, the fuel cladding tube 102 of Example 3 was completed.

[Example 4]
In Example 4, before the case of Example 1, the inner surface material layer 150 was formed by depositing a single layer (thickness: 0.2 mm) of silicon carbide by a chemical vapor deposition method. After forming a first composite material layer 110 having a thickness of 0.4 mm thereon as in the case of Example 1, a second composite material having a thickness of 0.4 mm was formed on the outer peripheral surface of the first composite material layer 110. A material layer 120 was formed. Thus, the fuel cladding tube 103 of Example 4 was completed.

[Example 5]
In Example 5, similarly to Example 3, after forming the first composite material layer 110 having a thickness of 0.4 mm, the intermediate layer 130 was formed on the outer peripheral surface of the first composite material layer 110. Here, the intermediate layer 130 was formed by forming a single layer (thickness: 0.1 mm) of titanium silicon carbide (Ti ₃ SiC ₂ ). Then, as in the case of Example 1, the second composite material layer 120 having a thickness of 0.3 mm was formed on the outer peripheral surface of the first composite material layer 110 via the intermediate layer 130. Thereafter, an outer surface material layer 140 was formed on the outer peripheral surface of the second composite material layer 120 to a thickness of 0.2 mm. Thus, the fuel cladding tube 104 of Example 5 was completed.

[Comparative example]
In the comparative example, the first composite material layer 110 was formed as in the case of Example 1, but the formation of the second composite material layer 120 was not performed. Thus, a fuel cladding tube having only the first composite material layer 110 having a thickness of 1 mm was prepared as a comparative example.

  In Examples 1 to 5 and Comparative Example, the directions of the first direction long fibers 111a and the second direction long fibers 111b of the first preform 115 of the first composite material layer 110 are respectively the same as the first direction. This is the case where the combination is performed in the circumferential direction and the axial direction described in the first embodiment, and the same applies to the second preform 125 of the second composite material layer 120.

[contents of the test]
Each sample of the examples and the comparative examples was subjected to an airtightness test, a thermal property test, an environmental resistance test (during normal operation and accident) and a mechanical property test.

  Table 1 shows the conditions of each example, and Table 2 shows the evaluation results of each example.

  In the airtightness test, a helium leak test was performed. In the thermal property test, a thermal conductivity measurement test by a laser flash method was performed.

As environmental resistance tests, a medium-temperature hydrothermal test was performed assuming normal operation, and a high-temperature steam test was performed assuming an accident. The medium temperature hydrothermal test was performed using an autoclave under the following test conditions. The weight before the test and the weight after the test were measured, and the thinning amount was converted from the difference between the two. Table 1 shows the ratio obtained by dividing the value obtained for each example by the value of the comparative example. That is, the ratio when the value of the comparative example is set to “1” with respect to the value of each example is shown.
(Medium-temperature hydrothermal test conditions)
・ Temperature: 360 ° C
・ Pressure: 18MPa
・ Retention time: 1 week (high temperature steam test)
・ Temperature: 1200 ° C
・ The amount of water vapor: 100%
・ Holding time: 72 hours

  In addition, a mechanical property test was performed on the sample of each example. Here, each of the initial fracture strength and the fracture energy was measured by performing a tensile strength test at room temperature as a mechanical property test. The test method was implemented in accordance with ASTM C1793-15. Regarding each of the initial breaking strength and the breaking energy, Table 1 shows the ratio obtained by dividing the value obtained for each example by the value of the comparative example. That is, the ratio when the value of the comparative example is set to “1” with respect to the value of each example is shown.

[Evaluation results]
As shown in Table 2, in Example 1, the helium leak amount was 1/100 or less of that of the comparative example, and the thermal conductivity was improved 1.5 times. In the environmental resistance test, the resistance is 1/100 or less of that of the comparative example, and the environmental resistance is excellent. Further, Example 1 is excellent in mechanical properties because the initial fracture strength and the fracture energy are higher in the mechanical property test than the comparative example. In Example 1, a first composite material layer 110 in which silicon carbide long fibers were composited in a silicon carbide matrix and a second composite material layer 120 in which carbon long fibers were composited in a silicon carbide matrix were used. It has a laminated structure. On the other hand, the comparative example includes only the first composite material layer 110. As described above, the first composite material layer 110 in which the silicon carbide long fiber is composited in the silicon carbide matrix is compared with the second composite material layer 120 in which the carbon long fiber is composited in the silicon carbide matrix. By laminating, the denseness of the material itself is also improved, and the airtightness, the thermal conductivity, the environmental resistance, and the mechanical properties can be improved.

  Example 2 has a higher breaking energy and is more excellent in mechanical properties than Example 1. In Example 2, a first composite material layer 110 in which silicon carbide long fibers were composited in a silicon carbide matrix and a second composite material layer 120 in which carbon long fibers were composited in a silicon carbide matrix were used. It has a laminated structure in which an intermediate layer 130 is further formed. On the other hand, the comparative example includes only the first composite material layer 110.

  As described above, the first composite material layer 110 in which the silicon carbide long fiber is composited in the silicon carbide matrix, the second composite material layer 120 in which the carbon long fiber is composited in the silicon carbide matrix, By laminating the intermediate layer 130, the denseness of the material itself is also improved, and further improvement in mechanical properties can be realized.

  In Example 3, since the dense single outer surface material layer 140 is formed, the helium leak amount is equal to or less than the detection limit, and extremely excellent airtightness is exhibited. Furthermore, in the environmental resistance test, the amount of corrosion thinning is significantly smaller than that of the comparative example, and the environmental resistance is excellent both during normal operation and during an accident.

  Further, in the mechanical property test, the examples 3 and 5 have higher initial breaking strength and breaking energy than the comparative example, and are excellent in mechanical properties. In particular, with respect to the breaking energy, Example 2 and Example 5 are higher than Example 1.

In the second embodiment, a single layer of carbon (C) is provided as an intermediate layer 130 between the first composite material layer 110 and the second composite material layer 120. In the third embodiment, a single layer of titanium silicon carbide (Ti ₂ SiC ₂ ) is provided as the intermediate layer 130.

  As described above, since the intermediate layer 130 formed of a specific material is interposed between the first composite material layer 110 and the second composite material layer 120, the breaking energy increases, so that the mechanical properties Can be further improved.

  Although not listed as an example in Table 1, in addition to the case where the intermediate layer 130 is a single layer of carbon or titanium aluminum carbide, chromium aluminum carbide, vanadium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, titanium silicon Even in the case of a single layer of carbide, similarly, improvement in environmental resistance and mechanical properties can be realized.

  DESCRIPTION OF SYMBOLS 1 ... Fuel pellet, 2 ... Spring, 3 ... Upper end plug, 4 ... Lower end plug, 10 ... Fuel rod, 50 ... Guide for forming a preform, 100, 101, 102, 103, 104 ... Fuel cladding tube, 110 ... first composite material layer, 111 ... first composite material long fiber, 111a ... first direction long fiber, 111b ... second direction long fiber, 112 ... first matrix (base material), 115 ... first Preform, 120 ... second composite material layer, 121 ... second composite long fiber, 121a ... first direction long fiber, 121b ... second direction long fiber, 122 ... second matrix (base material) ), 125: second preform, 130: intermediate layer, 140: outer surface material layer, 150: inner surface material layer

Claims (16)

A tubular fuel cladding tube for storing nuclear fuel,
A first composite material layer in which silicon carbide long fibers and a silicon carbide matrix are composited,
Laminated directly in contact with the first composite material layer so as to cover the first composite material layer on the radially outer side of the first composite material layer, and a long carbon fiber and a silicon carbide matrix are combined. A second composite material layer,
A fuel cladding tube comprising: A tubular fuel cladding tube for storing nuclear fuel,
A first composite material layer in which silicon carbide long fibers and a silicon carbide matrix are composited,
An intermediate layer directly in contact with the first composite material layer so as to cover the first composite material layer on a radially outer side of the first composite material layer;
A second composite material layer laminated directly in contact with the intermediate layer so as to cover the intermediate layer on the radially outer side of the intermediate layer, and a composite of a long fiber of carbon and a matrix of silicon carbide;
A fuel cladding tube comprising: The intermediate layer is formed of a single substance of a material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chromium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon carbide.
The fuel cladding tube according to claim 2, wherein:   The fuel cladding tube according to claim 2, wherein the intermediate layer has a hexagonal crystal form. 5.   The fuel cladding tube according to any one of claims 2 to 4, wherein the intermediate layer has a thickness of 0.01 mm or more and 0.1 mm or less.   An inner surface material layer disposed directly in contact with the first composite material layer so as to cover the first composite material layer from the inside of the first composite material layer; 6. The semiconductor device according to claim 1, further comprising at least one of an outer surface material layer disposed directly in contact with said second composite material layer so as to cover said second composite material layer from the outside. A fuel cladding tube according to any one of the preceding claims.   The fuel cladding tube according to claim 6, wherein the inner surface material layer and the outer surface material layer have a thickness of 0.2 mm or more and 0.4 mm or less.   The first composite material layer has a thickness of 0.2 mm or more and 1.0 mm or less, and the second composite material layer has a thickness of 0.2 mm or more and 0.6 mm or less; The thickness of the first composite material layer and the thickness of the second composite material layer such that the total value of the thickness of the layer and the thickness of the second composite material layer is 0.7 mm or more and 1.2 mm or less. The fuel cladding tube according to any one of claims 1 to 7, comprising: The first composite material long fibers in the first composite material layer are arranged in the first direction and those arranged in the second direction different from the first direction in the radial direction. Laminated,
The second composite material long fibers in the second composite material layer are arranged in the first direction and those arranged in the second direction different from the first direction in the radial direction. Laminated,
The fuel cladding tube according to any one of claims 1 to 8, characterized in that:   The fuel cladding tube according to claim 9, wherein the first direction is a circumferential direction, and the second direction is an axial direction. In the first composite material layer, a plurality of combinations of the first composite material long fibers arranged in a first direction and those arranged in a second direction different from the first direction have a radial direction. The first matrix is continuously arranged in the thickness direction between the laminated first composite material long fibers,
In the second composite material layer, a plurality of combinations of the second composite material long fibers arranged in a first direction and those arranged in a second direction different from the first direction are formed in a radial direction. The second matrix is continuously arranged in the thickness direction between the laminated second composite material long fibers,
The fuel cladding tube according to any one of claims 1 to 10, characterized in that: A method for manufacturing a fuel cladding tube for manufacturing a tubular fuel cladding tube for storing nuclear fuel,
A first composite material layer forming step of forming a first composite material layer by complexing silicon carbide long fibers with a silicon carbide matrix;
Forming a second composite material layer radially outside the first composite material layer by compounding long fibers of carbon with a silicon carbide matrix after the first composite material layer forming step; Forming a material layer;
Have
The formation of the first composite material layer and the formation of each of the second composite material layers use at least one of a chemical vapor deposition method and a chemical vapor infiltration method.
A method for producing a fuel cladding tube, comprising: A method for manufacturing a fuel cladding tube for manufacturing a tubular fuel cladding tube for storing nuclear fuel,
A first composite material layer forming step of forming a first composite material layer by complexing silicon carbide long fibers with a silicon carbide matrix;
An intermediate layer forming step of forming an intermediate layer of a single material on a radially outer side of the first composite material layer after the first composite material layer forming step;
After the intermediate layer forming step, a second composite material layer forming step of forming a second composite material layer radially outside the intermediate layer by compounding long fibers of carbon with a silicon carbide matrix,
Have
The formation of the first composite material layer and the formation of each of the second composite material layers use at least one of a chemical vapor deposition method and a chemical vapor infiltration method.
A method for producing a fuel cladding tube, comprising: The intermediate layer is formed of a single material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chromium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon carbide,
The formation of the intermediate layer is performed by at least one of a chemical vapor deposition method and a chemical vapor infiltration method,
The method for manufacturing a fuel cladding tube according to claim 13, wherein: Before the first composite material layer forming step, the method further includes an inner surface material layer forming step of forming a cylindrical inner surface material layer,
The fuel cladding tube according to any one of claims 12 to 14, wherein the inner surface material layer is formed by using at least one of a chemical vapor deposition method and a chemical vapor infiltration method. Manufacturing method. An outer surface material layer forming step of forming a cylindrical outer surface material layer after the second composite material layer forming step,
The fuel cladding according to any one of claims 12 to 15, wherein the outer surface material layer is formed by using at least one of a chemical vapor deposition method and a chemical vapor infiltration method. Pipe manufacturing method.

Images