JP7068058B2 - Manufacturing method of fuel cladding tube and fuel cladding tube - Google Patents

Description

An embodiment of the present invention relates to a fuel cladding tube and a method for manufacturing a fuel cladding tube.

A pressurized water reactor (PWR) supplies thermal energy generated from the nuclear split reaction of nuclear fuel in a nuclear reactor to a steam turbine cycle via a steam generator installed in the primary cooling system, and generates power with a generator. conduct. Further, in a boiling water reactor (BWR), the nuclear reactor also serves as a portion corresponding to a steam generator of the PWR, and heat is directly supplied from the nuclear reactor to the turbine cycle.

Here, uranium generally used as nuclear fuel is housed in a fuel cladding tube as a sintered body (fuel pellet) of uranium oxide, and cooling water flows around the fuel cladding tube. A plurality of fuel cladding tubes and a channel box surrounding them form 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. That is, zirconium has excellent corrosion resistance and has a small neutron absorption cross-sectional area. Therefore, in PWR, it is a Sn—Fe—Cr—Zr alloy called Zircaloy-4, and in BWR, it is called Zircaloy-2. -Fe-Cr-Ni-Zr alloy is used. Zirconium in these zirconium-based alloys undergoes a reaction at high temperatures to generate hydrogen with the surrounding moisture, as shown in the following reaction equation (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 itself, and is dramatic at a high temperature of about 1000 ° C. or higher. The generation of hydrogen increases.

When a zirconium-based alloy is exposed to such a high temperature in an environment where water 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 inside the reactor building and cause a hydrogen explosion.

For this reason, the use of silicon carbide ceramics as a material for fuel cladding is being studied because of its excellent heat resistance and oxidation resistance and its small neutron absorption cross section.

US Pat. No. 6,226,342

In the case of silicon carbide ceramic materials, it exhibits brittle fracture. Therefore, the resistance to destruction is not necessarily large. Further, in the case of the silicon carbide ceramic material in which the silicon carbide fiber is compounded, the breaking energy is higher than that in the case of the material in which the silicon carbide fiber is not compounded, but the strength, thermal conductivity, airtightness, and environmental resistance are high. There is a problem that

As a fuel cladding tube, it is possible to suppress the generation of hydrogen due to the reaction with moisture, and it has both strength and breaking energy at a high level, high thermal conductivity, high airtightness that does not allow helium gas to pass through, etc. In either case, it is necessary to have environmental resistance.

Therefore, it is an object of the present invention 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 a tubular fuel cladding tube for accommodating nuclear fuel, and is a first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited. And laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the first composite material layer, and a matrix of carbon filaments and silicon carbide. It is characterized by having a second composite material layer in which the material is composited.

Further, the present embodiment is a tubular fuel cladding tube for accommodating nuclear fuel, which is a first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited, and the first composite material layer. An intermediate layer laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the composite material layer, and the intermediate layer on the radial outer side of the intermediate layer. It has a second composite material layer that is laminated in direct contact with the intermediate layer so as to cover it and is a composite of long carbon fibers and a matrix of silicon carbide, and the intermediate layer is carbon, titanium aluminum carbide. , Vanadium Aluminum Carbide, Chrome Aluminum Carbide, Niobium Aluminum Carbide, Tantal Aluminum Carbide, Titanium Silicon Carbide .
Further, the present embodiment is a tubular fuel cladding tube for accommodating nuclear fuel, which is a first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited, and the first composite material layer. An intermediate layer laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the composite material layer, and the intermediate layer on the radial outer side of the intermediate layer. It has a second composite material layer that is laminated in direct contact with the intermediate layer so as to cover it, and is a composite of long carbon fibers and a matrix of silicon carbide, and the intermediate layer has a hexagonal crystal form. It is characterized by being.

Further, the present embodiment is a method for manufacturing a fuel cladding tube for manufacturing a tubular fuel cladding tube for accommodating nuclear fuel, and the first method is to composite long fibers of silicon carbide with a matrix of silicon carbide. After the first composite material layer forming step for forming the composite material layer and the first composite material layer forming step, an intermediate layer for forming an intermediate layer made of a single material is formed on the radial outer side of the first composite material layer. After the layer forming step and the intermediate layer forming step, a second composite material layer is formed on the radial outer side of the intermediate layer by compounding long carbon fibers with a silicon carbide matrix. It has a forming step, and at least one of a chemical vapor phase vapor deposition method and a chemical vapor phase infiltration method is used for the formation of the first composite material layer and the formation of each of the second composite material layer. The intermediate layer is formed of a single material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chrome aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon carbide, and the intermediate layer is formed. Is characterized by performing at least one of a chemical vapor phase vapor deposition method and a chemical vapor phase infiltration method .

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

It is an exploded view which shows the structure of the fuel rod which has the fuel cladding tube which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the fuel cladding tube which concerns on 1st Embodiment. It is a flow chart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 1st Embodiment. It is a top view which shows the arrangement of the long fiber for the 1st composite material in the formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube which concerns on 1st Embodiment. It is a top view which shows the arrangement of the long fiber for the 2nd composite material in the formation of the 2nd composite material layer of the manufacturing method of the fuel cladding tube which concerns on 1st Embodiment. It is a perspective view which shows the state after the formation of the preformed body by 1st example in the formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube which concerns on 1st Embodiment. It is a perspective view which shows the state after the formation of the preformed body by 2nd example in the formation of the 1st composite material layer of the manufacturing method of the fuel cladding tube which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the fuel cladding tube which concerns on 2nd Embodiment. It is a flow chart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 2nd Embodiment. It is sectional drawing which shows the structure of the fuel cladding tube which concerns on 3rd Embodiment. It is a flow chart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the fuel cladding tube which concerns on 4th Embodiment. It is a flow chart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 4th Embodiment. It is sectional drawing which shows the structure of the fuel cladding tube which concerns on 5th Embodiment. It is a flow chart which shows the procedure of the manufacturing method of the fuel cladding tube which concerns on 5th Embodiment.

Hereinafter, the fuel cladding tube according to the embodiment of the present invention and the method for manufacturing the fuel cladding tube will be described with reference to the drawings. Here, common reference numerals are given to parts that are the same as or similar to each other, and the description of superimposing them 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 open portions above and below the fuel rod 100, and a plurality of cylindrical columns of nuclear fuel, for example, laminated in the longitudinal direction. It has a fuel pellet 1 and a spring 2 for suppressing its vibration.

The fuel cladding tube 100 is a cylindrical tube, and together with the upper end plug 3 and the lower end plug 4, forms a closed space. Nuclear fuel is stored in this enclosed space. 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 a circular shape. For example, it may have a shape 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 laminated. Are in contact with each other.

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

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

The fuel cladding tube 100 has, for example, an outer diameter of 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 of the thickness for removing heat from the nuclear fuel containing fission products to the outside. , 0.7 mm or more and 1.2 mm or less are preferable.

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 the reinforcing mechanism by the long fibers is sufficiently exhibited at the time of damage. It is preferably 0.0 mm or less.

Further, the thickness of the second composite material layer 120 is 0.2 mm or more in terms of mechanical properties and environmental resistance of the fuel cladding tube 100, and the reinforcing mechanism by the long fibers is sufficiently exhibited at the time of damage. It 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 thickness of the second composite material layer 110 are 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 flow chart showing a procedure of a method for manufacturing a fuel cladding tube according to the first embodiment.

When forming the second composite material layer 120 radially outside 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. Form 120 (step S201).

Regarding the formation of the first composite material layer 110 (step S101), first, the fiber bundle of the first long fiber 111 for composite material (FIG. 4), which is a long fiber of silicon carbide, is used for the first preforming. Form the body 115 (FIG. 4) (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, a cylindrical preformed body forming guide 50 (FIGS. 6 and 7) made of a carbon-based material is used, and a first cylindrical preformed body (fiber preform) is used around the guide. ) 115 is formed.

FIG. 4 is a plan view showing the arrangement of the long fibers for the first composite material in the formation of the first composite material layer. The first composite length fiber 111 has a first-direction long fiber 111a arranged in the first direction and a second-direction long fiber 111b arranged in the 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 outer side in the radial direction. Note that FIG. 4 shows an example in which a space is provided between each group of the first-direction long fibers 111a and between each group of the second-direction long fibers 111b, but even if this space is not provided. good.

The first direction and the second direction intersect each other with an intersection angle Φ. By arranging them in two directions, stress can be applied in each of the axial direction and the circumferential direction of the fuel cladding tube 100, and the strength can be improved in each direction. If the first direction is the circumferential direction and the second direction is the axial direction, or both are deviated by the same angle, the first direction and the second direction are orthogonal to each other, 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 on the outer side 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 preformed body 115, the fuel cladding tube 100 is bonded to each other in the plurality of first-direction long fibers 111a and the plurality of second-direction long fibers 111b. A stitch may be provided in a part for forming a part or the like.

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

FIG. 5 is a plan view showing the arrangement of the long fibers for the second composite material in the formation of the second composite material layer. The second composite length 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 outer side in the radial direction. The same applies to the second preformed body 125 as well as the first preformed body. However, it is not always necessary to use the same molding method as that of the first preformed body.

FIG. 6 is a perspective view showing a state after the formation of the preformed body according to the first example in the formation of the first composite material layer. In this 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, for example, using a filament winding method and reducing the inclination angle of the spiral. Alternatively, in order to form completely in the circumferential direction, that is, to set the inclination angle to 0 degrees, the fiber bundles for the first direction, that is, the circumferential direction are arranged in parallel in the axial direction, and the fiber bundles for the second direction, that is, the axis are arranged in parallel. A method of winding the fiber bundle for the circumferential direction while sandwiching the fiber bundle for the direction may also be used. In this case, since a multi-layered configuration can be realized at one time by this operation, it is necessary to know in advance how many turns will make the thickness.

It is preferable that the first direction is in the range of plus or minus 30 degrees with respect to the circumferential direction, and the second direction is in the range of plus or minus 30 degrees with respect to the axial direction. If it is 30 degrees, the cosine of 30 degrees is about 0.86, and the strength in the desired direction can be secured. That is, if it can be compounded within this range, it becomes possible to sufficiently exhibit the strength characteristics required for the structural member for the fuel cladding tube.

By arranging the strengthening directions of the long fibers 111a in the first direction and the long fibers 111b in the second direction 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. Is formed. Thereby, the thermal conductivity in the thickness direction of the fuel cladding tube can provide a structure utilizing the excellent thermal conductivity of the silicon carbide of the matrix.

FIG. 7 is a perspective view showing a state after formation of the preformed body according to the second example in the formation of the first composite material layer. In this 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 opposite 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 fiber 111a and the second-direction long fiber 111b intersect with each other at a certain crossing angle Φ, as shown in FIG.

As a method for producing the fiber preform, a filament winding method and a braiding method can be used.

Around the columnar preformed body forming guide 50, fiber bundles of long fibers of silicon carbide are arranged in the same direction, wound to a predetermined thickness, and then solidified. After this, the preformed body forming guide 50 is removed, for example, after the formation of the first preformed body 115 or after the formation of the first composite material layer 110.

As a result, the long fiber 111 for the first composite material has a predetermined thickness in the radial direction by laminating a single layer or a plurality of layers of a combination of the long fiber 111a in the first direction and the long fiber 111b in the second direction. The first preformed body 115 to have 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 adhering to the inside and outside of the first preformed body 115 in the radial direction, and the like.

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

The formation of the first matrix 112 is carried out by at least one of a chemical vapor deposition method and a chemical vapor phase infiltration method, and both may be used. For example, it is assumed that the first matrix 112 is formed by the chemical vapor phase infiltration method between the long fibers 111 for the first composite material constituting the first preformed body 115, and if necessary, the first matrix 112 is formed. The matrix may be formed by a chemical vapor deposition method so that the matrix covers the periphery of the preformed body 115.

When the matrix is formed by the precursor impregnation firing method (PIP), fine cracks are generated in the matrix due to shrinkage due to firing. Further, the silicon carbide matrix formed is amorphous silicon carbide (Si—CO) and contains oxygen. Therefore, in order to ensure airtightness and high thermal conductivity in the fuel cladding tube 100, it is better to form the matrix by the chemical vapor deposition method or the chemical vapor deposition method instead of the precursor impregnation firing method (PIP). preferable.

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

Next, regarding the formation of the second composite material layer 120 (step S201), first, the second preformed body 125 (FIG. 5) is formed by using the fiber bundle of long carbon fibers (step S211). .. Specifically, a fiber bundle (yarn) in which a plurality of long carbon 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. Using the fiber bundle, the outer surface of the first composite material layer 110 is placed in contact with the first composite material layer 110 so as to cover the first composite material layer 110, and the second reserve is cylindrical. A molded body (fiber preform) 125 is formed.

Similarly to the first preformed body 115, the second preformed body 125 is also composed of 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 preformed body 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 than carbon long fibers in an environment where the atmospheric temperature is high, for example, exceeding 400 ° C. Further, the long fibers of silicon carbide have a tensile strength of 2 to 4 GPa and a tensile elastic modulus of 150 to 400 GPa. Therefore, the first composite material layer 110 using the long fiber 111 for the first composite material, 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 of about 400 ° C. or lower than silicon carbide long fibers. Further, the long carbon fiber has a tensile strength of 1 to 7 GPa and a tensile elastic modulus of 30 to 950 GPa. Therefore, the second composite material layer 120 using the second long fiber 121 for a composite material, which is a long fiber of carbon, is particularly effective under operating conditions mainly during 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. , The first composite material layer 110 such that the total thickness of the fuel cladding tube 100 formed by the first composite material layer 110 and the second composite material layer 120 is 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 these conditions, the first composite layer 110 and the second composite material depend on the policy of how to balance the environmental resistance and mechanical properties during normal operation and accidents. The thickness of each of the layers 120 can be appropriately set and laminated. In addition, airtightness and high thermal conductivity can be ensured by using at least one of a chemical vapor deposition method and a chemical vapor phase infiltration method for forming the matrix.

As described above, the first composite material layer 110 in which the long fibers 111 for the first composite material of silicon carbide are composited with the first matrix 112 of silicon carbide, and the second matrix 122 of silicon carbide are made of carbon. By forming the fuel cladding tube 100 in a laminated structure with the second composite material layer 120 in which the long fibers 121 for composite materials of 2 are composited, the environmental resistance and mechanical properties are improved over a wide range of environmental conditions. It 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 as a material 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. can.

As described above, the method for manufacturing a fuel cladding tube and a 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 second embodiment, the intermediate layer 130 is provided on the radial outside of the first composite material layer 110 and on the radial inside of 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 that of the first embodiment.

The intermediate layer 130 is formed of, for example, 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 thickness of the intermediate layer 130 is preferably 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 is at least the lower limit of the above range. Further, from the viewpoint of the mechanical strength characteristics of the fuel cladding tube 100, it is preferable that the intermediate layer 130 is not more than the upper limit value in the above range. Therefore, it is more preferable that the thickness of the intermediate layer 130 is 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 the fuel cladding tube 101 having different strengths in the length direction (axial direction) and the circumferential direction. It is more preferable that the intermediate layer 130 has a monoclinic crystal form showing a hexagonal or pseudo-hexagonal crystal form. In this case, the crystal face slips in the hexagonal crystals constituting the intermediate layer 130. Therefore, it is possible to suppress the growth of cracks in each of the first composite material layer 110 and the second composite material layer 120. As a result, the mechanical properties of the fuel cladding tube 101 can be further improved. In particular, for ternary carbides (eg, 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.

In addition to the case where the intermediate layer 130 has only one single layer of the specific material described above, the intermediate layer 130 may be configured by laminating a plurality of the single layers. 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 flow chart showing a procedure of a method for 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, the intermediate layer forming step S301 is performed after the first composite material layer forming step S101 and before the second composite material layer forming step S202. I do.

The first composite material layer forming step S101 is the same as that of the first embodiment.

In the intermediate layer forming step S301, a single layer of a predetermined material is formed on the radial outer side of the first composite material layer 110 (step S311). The intermediate layer 130 is formed by using one type of single layer or by laminating a plurality of types of single layers.

The intermediate layer 130 is formed by a 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 an organic metal vapor deposition method. ) Method or other film deposition method. Of these, the thermal CVD method is suitable because the film formation of the first composite material layer 110 and the film formation of the intermediate layer 130 can be continuously performed by switching the raw material gas.

Next, the second composite material layer 120 is formed (step S202). First, the second preformed body 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 preformed body 125 formed in step S212 (step S222). Specifically, the same method as in the case of the first embodiment is performed. As described above, the fuel cladding tube 101 of the present embodiment is completed.

In the present embodiment, the mechanical properties in the strengthening direction by the long fibers are further improved by the 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, the outer surface material layer 140 of the silicon carbide ceramics is further provided on the radial outer side of the second composite material layer 120. Except for the points related to this, the present embodiment is the same as that of the first embodiment.

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 sufficiently maintain environmental resistance and airtightness, and in order to secure a stable design strength in terms of strength, The mechanical properties of the initial strength may be inadequate. When the outer surface material layer 140 is thicker than the upper limit of the above range, the abundance ratios of the first long fiber 111 for composite material and the second long fiber 121 for composite material in the entire fuel cladding tube 102 are relative to each other. Therefore, the mechanical properties regarding the fracture energy of the fuel cladding tube 102 may be insufficient.

FIG. 11 is a flow chart showing a procedure of a method for manufacturing the fuel cladding tube 102 according to the third embodiment. The portion where the step S201 for forming the second composite material layer 120 is carried out after the step S101 for forming the first composite material layer 110 is the same as that of the first embodiment.

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

Since the radial outer surface of the fuel cladding tube 102 according to the present embodiment formed as described above is covered with the outer surface material layer 140, the amount of corrosion thinning is reduced and the fuel cladding tube 102 has environmental resistance. The improvement can be realized more easily. Furthermore, since dense silicon carbide is formed by the chemical vapor deposition method, high airtightness that suppresses the 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, the outer surface material layer 140 is formed on the radial outer side of the second composite material layer 120. On the other hand, in the fourth embodiment, the 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, the outer surface material layer 140 is formed. , The inner surface material layer 150 of silicon carbide ceramics is formed on the inner surface in the radial direction.

FIG. 13 is a flow chart showing a procedure of a method for manufacturing the fuel cladding tube 103 according to the fourth embodiment. In the method for manufacturing the fuel cladding tube 103 according to the present embodiment, first, the inner surface material layer 150 is formed (step S501). Specifically, the inner surface material layer 150 is formed by a simple substance of the silicon carbide ceramic material by the chemical vapor deposition method (step S511).

After that, the first composite material layer 110 is formed (step S102). That is, the first preformed body 115 is formed on the radial outer side of the inner surface material layer 150 (step S112), and the first matrick 112 is formed on the first preformed body 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, can be enhanced, and high airtightness can be ensured.

[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 from the radial inner side to the radial outer side. The surface material layers 140 are laminated in this order.

FIG. 15 is a flow chart showing a procedure of a method for manufacturing a fuel cladding tube according to a fifth embodiment. First, the first composite material layer 110 is formed (step S101). Next, the intermediate layer 130 is formed on the radial outer surface of the first composite material layer 110 (step S301). The specific formation of the simple substance layer (step S311) is the same as that of the second embodiment.

Next, a second composite material layer 120 is formed on the radial outer surface of the intermediate layer 130 (step S202). Then, after step S20 for 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 actions 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 long fibers 111 for the first composite material of silicon carbide are composited with the first matrix 112 of silicon carbide, and the second matrix 122 of silicon carbide with the second carbon. By forming the fuel cladding tube 104 in a laminated structure with the second composite material layer 120 in which the long fibers 121 for the composite material are composited, the improvement of environmental resistance and mechanical properties is realized over a wide range of environmental conditions. be able to. Further, the mechanical properties in the strengthening direction by the long fibers can be further improved by the material design utilizing the fact that the intermediate layer 130 formed of the specific material has different strengths in the length direction, the circumferential direction and the thickness direction. Further, since the outer surface in the radial direction is covered with the outer surface material layer 140, the amount of corrosion thinning is reduced, and the improvement of environmental resistance can be further easily realized. Further, since the dense silicon carbide is formed by the chemical vapor deposition method, high airtightness that does not allow helium gas to pass through can be realized.

[Other embodiments]
Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. For example, in the embodiment, the case where the fuel cladding tube 100 stores the uranium fuel as the nuclear fuel is shown as an example, but the present invention is not limited thereto. For example, it may be in the form of a plutonium fuel, a mixed oxide fuel of uranium and plutonium, or a non-oxide, for example, a carbide or a nitride. Further, in the embodiment, the case where the fuel cladding tube 100 has a coolant of light water is shown as an example, but the present invention is not limited to this. For example, it may be a gas-cooled reactor such as helium gas or carbon dioxide gas, or a liquid metal cooled reactor containing sodium, lead, or the like.

Moreover, you may combine the features of each embodiment. For example, a third embodiment and a fourth embodiment may be combined.

Furthermore, these embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

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.

In addition, Examples 1 to 5 shown below correspond to the first Embodiment 1 to 5, respectively.

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

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 above-mentioned first preformed body 115 is set inside the carbon mold in the chemical gas phase reaction furnace, the temperature is 1300 to 1400 ° C. and the pressure is 4 to 100 kPa. The raw material gas (silicon tetrachloride gas, propane gas, hydrogen gas) was introduced into the reactor. As a result, the first matrix 112 containing silicon carbide as a main component was formed in the first preformed body 115 to prepare the first composite material layer 110 having a thickness of 0.5 mm. Here, the first matrix 112 is formed by the chemical vapor phase infiltration method between the long fibers 111 for the composite material constituting the first preformed body 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 first matrix 112 covered the periphery of the preformed body 115.

Next, a second preformed body (preform) 125 constituting the second composite material layer 120 was formed. In this step, first, carbon was coated on the surface of carbon long fibers having a diameter of 10 μm (trade name: Treca (registered trademark) M60, manufactured by Toray Industries, Inc.) by the CVD method. Then, a fiber bundle (yarn) obtained by bundling 3000 long fibers 121 for the second composite material is split into 500 fibers, and the fiber bundle is used by a filament winding method to form a cylinder and have a thickness of 0.5 mm. The second preformed body 125 was prepared on the outer peripheral surface of the first composite material layer 110.

Next, a second matrix 122 was formed on the second preformed body 125 of the second composite material layer 120. In this step, after the above-mentioned second preformed body 125 is set inside the carbon mold in the chemical gas phase reaction furnace, the temperature is 1300 to 1400 ° C. and the pressure is 4 to 100 kPa. The raw material gas (silicon tetrachloride gas, propane gas, hydrogen gas) was introduced into the reactor. As a result, the second matrix 122 containing silicon carbide as a main component was formed on the second preformed body 125 to form the second composite material layer 120 having a thickness of 0.5 mm. Here, as in the case of the first composite material layer 110, the chemical vapor phase permeates between the long fibers 121 for the second composite material constituting the second preformed body 125 of the second composite material layer 120. The second matrix 122 was formed by the method, and the second matrix 122 was formed by the chemical vapor vapor deposition method so that the second matrix 122 covered the circumference of the second preformed body 125. As a result, the fuel cladding tube 100 of Example 1 was completed.

[Example 2]
In Example 2, as in the case of 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) (thickness 0.1 mm). Then, as in the case of Example 1, a second composite material layer 120 was formed on the outer peripheral surface of the first composite material layer 110 via the intermediate layer 130. As a result, the fuel cladding tube 101 of Example 2 was completed.

[Example 3]
In Example 3, as in the case of Example 1, after preparing the first composite material layer 110 having a thickness of 0.4 mm, a 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. The composite material layer 120 was formed. Then, the 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 a chemical vapor deposition method. As a result, the fuel cladding tube 102 of Example 3 was completed.

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

[Example 5]
In Example 5, similarly to the case of Example 3, the intermediate layer 130 was formed on the outer peripheral surface of the first composite material layer 110 after the first composite material layer 110 having a thickness of 0.4 mm was formed. 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, a 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. Then, an outer surface material layer 140 having a thickness of 0.2 mm was formed on the outer peripheral surface of the second composite material layer 120. As a result, the fuel cladding tube 104 of Example 5 was completed.

[Comparison example]
In the comparative example, the first composite material layer 110 was formed as in the case of Example 1, but the second composite material layer 120 was not formed. As a result, a fuel cladding tube made of 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 Examples, the directions of the first-direction long fibers 111a and the second-direction long fibers 111b of the first preformed body 115 of the first composite material layer 110 are the first, respectively. This is the case of combining in the circumferential direction and the axial direction described in the first embodiment, and the same applies to the second preformed body 125 of the second composite material layer 120.

[contents of the test]
Airtightness test, thermal property test, environmental resistance test (during normal operation, accident) and mechanical property test were performed on each sample of Examples and Comparative Examples.

The conditions of each example are shown in Table 1, and the evaluation results for each example are shown in Table 2.

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

In addition, as environmental resistance tests, a medium-temperature water heat test was conducted assuming normal operation, and a high-temperature steam test was conducted assuming an accident. The medium temperature water heat test was performed under the following test conditions using an autoclave. The weight before the test and the weight after the test were measured, and the amount of wall loss was converted from the difference between the two. Table 1 shows the ratio of the values obtained for each example divided by the values of the comparative examples. That is, the ratio when the value of the comparative example is set to "1" is shown for the value of each embodiment.
(Conditions for medium temperature water heat test)
-Temperature: 360 ° C
・ Pressure: 18MPa
・ Retention time: 1 week (high temperature steam test)
・ Temperature: 1200 ℃
・ Amount of water vapor: 100%
・ Holding time: 72 hours

In addition, mechanical property tests were conducted on the samples of each example. Here, as a mechanical property test, a tensile strength test was carried out at room temperature to measure the initial fracture strength and the fracture energy. The test method was carried out in accordance with ASTM C1793-15. For each of the initial fracture strength and the fracture energy, Table 1 shows the ratio of the values obtained for each example divided by the values of the comparative examples. That is, the ratio when the value of the comparative example is set to "1" is shown for the value of each embodiment.

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

Further, the second embodiment has a higher breaking energy and is excellent in mechanical properties as compared with the first embodiment. In Example 2, a first composite material layer 110 in which long fibers of silicon carbide are composited in a matrix of silicon carbide and a second composite material layer 120 in which long fibers of carbon are composited in a matrix of silicon carbide. It is composed of a laminated structure in which an intermediate layer 130 is further formed between the layers. On the other hand, the comparative example is composed of only the first composite material layer 110.

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

In Example 3, since the outer surface material layer 140 of a dense simple substance is formed, the amount of helium leak is below the detection limit, and the airtightness is very excellent. Further, in the environmental resistance test, the amount of corrosion and wall 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, Examples 3 and 5 have higher initial fracture strength and fracture energy than Comparative Examples, and are excellent in mechanical properties. In particular, with respect to the destructive energy, Example 2 and Example 5 are higher than Example 1.

In Example 2, a simple substance 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 Example 3, a single layer of titanium silicon carbide (Ti ₂ SiC ₂ ) is provided as an intermediate layer 130.

As described above, by interposing the intermediate layer 130 formed of a specific material between the first composite material layer 110 and the second composite material layer 120, the fracture energy is increased, and thus the mechanical properties are obtained. 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, chrome aluminum carbide, vanadium aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon. Similarly, in the case of a single layer of carbide, improvement in environmental resistance and mechanical properties can be realized.

1 ... fuel pellets, 2 ... springs, 3 ... upper end plugs, 4 ... lower end plugs, 10 ... fuel rods, 50 ... guides for forming preformed bodies, 100, 101, 102, 103, 104 ... fuel cladding tubes, 110. ... 1st composite material layer, 111 ... 1st composite long fiber, 111a ... 1st direction long fiber, 111b ... 2nd direction long fiber, 112 ... 1st matrix (base material), 115 ... 1st Preformed body, 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 preformed body, 130 ... Intermediate layer, 140 ... Outer surface material layer, 150 ... Inner surface material layer

Claims (13)

A tubular fuel cladding tube for storing nuclear fuel.
A first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited,
The first composite material layer is laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the first composite material layer, and the long carbon fibers and the matrix of silicon carbide are composited. With the second composite material layer
A fuel cladding tube characterized by having. A tubular fuel cladding tube for storing nuclear fuel.
A first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited,
An intermediate layer laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the first composite material layer.
A second composite material layer in which long carbon fibers and a matrix of silicon carbide are composited and laminated in direct contact with the intermediate layer so as to cover the intermediate layer on the radial outer side of the intermediate layer.
Have,
The intermediate layer is formed of a single material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chrome aluminum carbide, niobium aluminum carbide, tantalum aluminum carbide, and titanium silicon carbide.
A fuel cladding tube characterized by that. A tubular fuel cladding tube for storing nuclear fuel.
A first composite material layer in which long fibers of silicon carbide and a matrix of silicon carbide are composited,
An intermediate layer laminated in direct contact with the first composite material layer so as to cover the first composite material layer on the radial outer side of the first composite material layer.
A second composite material layer, which is laminated in direct contact with the intermediate layer so as to cover the intermediate layer on the radial outer side of the intermediate layer, and is a composite of long carbon fibers and a matrix of silicon carbide.
Have,
The intermediate layer is a fuel cladding tube characterized by having a hexagonal crystal form . The fuel cladding tube according to claim 2 or 3, wherein the intermediate layer has a thickness of 0.01 mm or more and 0.1 mm or less . The inner surface material layer arranged in direct 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, and the second composite material layer. Claims 1 to 4 further include at least one of the outer surface material layers arranged in direct contact with the second composite material layer so as to cover the second composite material layer from the outside. The fuel cladding tube according to any one of the above. The fuel cladding tube according to claim 5, 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 thickness of the first composite material layer is 0.2 mm or more and 1.0 mm or less, and the thickness of the second composite material layer is 0.2 mm or more and 0.6 mm or less, and the first composite material. 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 6, characterized in that it has . The long fibers for the first composite material 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 long fibers for the second composite material 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 7, wherein the fuel cladding tube is characterized by the above. The fuel cladding tube according to claim 8, wherein the first direction is a circumferential direction and the second direction is an axial direction . The long fibers for the first composite material in the first composite material layer are a plurality of combinations of those arranged in the first direction and those arranged in the second direction different from the first direction in the radial direction. The first matrix is continuously arranged in the thickness direction between the laminated long fibers for the first composite material.
The long fibers for the second composite material in the second composite material layer are a plurality of combinations of those arranged in the first direction and those arranged in the second direction different from the first direction in the radial direction. A second matrix is continuously arranged in the thickness direction between the laminated long fibers for the second composite material.
The fuel cladding tube according to any one of claims 1 to 7, wherein the fuel cladding tube is characterized. It is a method of manufacturing a fuel cladding tube that manufactures a cylindrical fuel cladding tube for storing nuclear fuel.
The first composite material layer forming step of forming the first composite material layer by compounding the long fibers of silicon carbide with the silicon carbide matrix,
After the first composite material layer forming step, an intermediate layer forming step of forming an intermediate layer made of a single material on the radial outside of the first composite material layer,
After the intermediate layer forming step, a second composite material layer forming step of forming a second composite material layer on the radial outer side of the intermediate layer by compounding long carbon fibers in a silicon carbide matrix.
Have,
At least one of the chemical vapor deposition method and the chemical vapor phase infiltration method was used for the formation of the first composite material layer and the formation of each of the second composite material layer.
The intermediate layer is formed of a single material selected from the group consisting of carbon, titanium aluminum carbide, vanadium aluminum carbide, chrome 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 the chemical vapor deposition method and the chemical vapor phase infiltration method.
A method for manufacturing a fuel cladding tube. Prior to the first composite material layer forming step, an inner surface material layer forming step for forming a tubular inner surface material layer is further provided.
The method for manufacturing a fuel cladding tube according to claim 11, wherein at least one of a chemical vapor deposition method and a chemical vapor phase infiltration method is used for forming the inner surface material layer . After the second composite material layer forming step, the outer surface material layer forming step for forming the cylindrical outer surface material layer is further provided.
The method for manufacturing a fuel cladding tube according to claim 11 or 12, wherein at least one of a chemical vapor deposition method and a chemical vapor phase infiltration method is used for forming the outer surface material layer .

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