Split nuclear fuel pellet structure and SiC composite material cladding fuel rod

Abstract

The invention discloses a split type nuclear fuel pellet structure and a SiC composite material cladding fuel rod. The split type nuclear fuel pellet structure comprises a pellet (1) and an elastic piece (2), a cavity (11) for accommodating the elastic piece (2) is formed in the middle of the core block (1); the core block (1) comprises at least two core block petals (10) which are matched in the radial direction, and the elastic piece (2) is contained in the cavity (11) and abuts against the core block petals (10). According to the split type nuclear fuel pellet structure, the pellet (1) and the nuclear fuel cladding tube (3) are in clearance-free tight fit, and uniform circumferential heat transfer of a fuel rod can be guaranteed. The core block (1) with the cavity (11) in the middle can further reduce the operating peak temperature of the core block (1), and the cavity (11) can contain more fission gas, so that the internal pressure of the fuel rod can be reduced.

Description

Split-type nuclear fuel pellet structure and SiC composite cladding fuel rod Technical Field

[0001] The present invention relates to the field of nuclear fuel technology, in particular to a petal-type nuclear fuel pellet structure and a SiC composite material cladding fuel rod. Background Art

[0002] The core of a nuclear power plant consists of multiple fuel assemblies. A fuel assembly consists of a rigid framework and fuel rods, which are arranged in parallel and evenly spaced within the framework. The fuel rods are composed of cladding tubes, fuel pellets, air springs, and upper and lower end plugs. After the fuel pellets and air springs are loaded into the cladding tubes, the upper and lower end plugs are welded to the upper and lower ends, respectively, to form the fuel rods. In most existing technologies, cladding tubes are typically made of zirconium alloy.

[0003] Compared with zirconium alloys, SiC composite materials have significant advantages in high-temperature strength, radiation stability, creep resistance, oxidation resistance, and wear resistance. They also have significant fault tolerance potential under light water reactor accident conditions. Therefore, nuclear fuel cladding with SiC composite materials has become a key research direction internationally.

[0004] Although SiC composite materials have good strength, creep resistance and other properties, they are ceramic brittle materials. Compared with the metal cladding used in the current traditional UO2-Zr fuel system, their ductility is lower. When a small amount of bending or strain occurs, cracks are easily generated. The generation of cracks may lead to the ineffective sealing of the fuel rods and affect the safe operation of the reactor.

[0005] Due to the performance characteristics of the above-mentioned SiC composite material, when it is used as the cladding of the fuel rod, the gap between the pellet and the cladding needs to be carefully designed. Because SiC composite materials are ceramic materials, they have basically no plasticity, and their elastic modulus is much larger than that of traditional zirconium alloy claddings. Therefore, it is necessary to consider whether the designed fuel rods will actually operate in the reactor to avoid serious pellet-cladding interactions. Because once the pellets come into contact with the cladding, due to the intrinsic strains of the pellets such as radiation swelling and thermal expansion, the intrinsic strains of these pellets will cause the SiC composite cladding to produce large stresses and strains; and the ability of the SiC composite cladding to withstand strain is limited, and structural damage is very likely to occur. Therefore, the design of the existing technology often needs to consider designing a larger pellet-cladding gap value to avoid serious pellet-cladding interactions.

[0006] That is, in the prior art, the pellet-cladding in the SiC composite cladding fuel rod is a gap design. However, based on the design scheme of the prior art, the inventors found that it has the following defects:

[0007] 1. If there is a gap between the pellet and the cladding, heat transfer can only rely on gas conduction and radiation in the gap, which is relatively weak. Combined with the high heat flux density of the fuel rod, the existence of this gap will lead to a significant decline in the radial heat transfer capacity of the fuel rod, which will greatly increase the operating temperature of the pellets inside the fuel rod and significantly reduce the temperature operating safety margin of the fuel rod. At the same time, the increase in operating temperature can further increase the amount of fission gas released from the pellets, thereby increasing the internal pressure of the fuel rod and reducing the operating safety of the fuel rod.

[0008] 2. The pellets are installed within the cladding tube. The outer diameter of the pellets is generally smaller than the inner diameter of the cladding. The large pellet-cladding gap inevitably makes it difficult to ensure that the pellets are completely centered within the cladding during actual operation. When using SiC composite cladding, the following problems arise when the pellets are not centered within the cladding: one side of the pellets will be closer to the cladding, while the other side will be farther away. This leads to uneven circumferential heat transfer in the fuel rods. The area closer to the cladding has lower thermal resistance and greater heat flux, resulting in higher cladding temperatures; the opposite is true for areas farther away from the cladding. Furthermore, when the SiC cladding is operated under the irradiation conditions within the reactor, it will irradiate and swell. This irradiation swelling is not only related to the irradiation dose but also to the irradiation temperature: the higher the temperature, the smaller the irradiation swelling. Therefore, if the circumferential temperature of the SiC cladding is uneven, uneven irradiation swelling will occur, which in turn will cause the fuel rods to bend, affecting their operational safety. Technical issues

[0009] The technical problem to be solved by the present invention is to provide an improved split-petal nuclear fuel pellet structure and a SiC composite cladding fuel rod. Technical Solutions

[0010] The technical solution adopted by the present invention to solve the technical problem is: providing a petal-type nuclear fuel pellet structure, which includes a pellet and an elastic member;

[0011] A cavity for accommodating the elastic member is provided in the middle of the core block;

[0012] The core block includes at least two radially matched core block petals, and the elastic member is accommodated in the cavity and abuts against each of the core block petals.

[0013] Preferably, the cavity is arranged to extend along the axial direction of the core block;

[0014] The elastic member is an elastic tube and is placed in the cavity along the extension direction of the cavity.

[0015] Preferably, the number of the core block petals is two, and the elastic member is an elliptical tube;

[0016] The elastic member abuts against the core block petal with its circumference corresponding to the major axis of the ellipse, and a first gap is formed between the circumference corresponding to the minor axis of the ellipse on the elastic member and the core block petal, and the first gap is used to accommodate the elastic deformation of the elastic member.

[0017] Preferably, an inner curvature is formed on the circumference of the elastic member corresponding to the minor axis of the ellipse.

[0018] Preferably, the number of the core block petals is at least three, and the circumferential surface of the elastic member has at least three first protrusions that protrude outward and abut against the core block petals. Recesses are formed correspondingly between adjacent first protrusions, and a first gap is formed between the recessed portions and the core block petals. The first gap is used to accommodate the elastic deformation of the elastic member.

[0019] Preferably, at least one through hole is formed on the circumferential surface of the elastic member.

[0020] Preferably, the elastic member is a spring, and the number of the core block petals is two;

[0021] The relative mating surfaces of the two core block petals are respectively concave, forming the cavity on each core block petal; the elastic member is accommodated in the cavity of the two core block petals, and its two opposite ends are respectively pressed against the inner bottom surface of the cavity of the two core block petals.

[0022] Preferably, the cavity is in the shape of a stepped hole, including a first cavity and a second cavity that are connected, the inner circumference of the first cavity is larger than the inner circumference of the second cavity, the first cavity is close to the central axis of the core block, and the second cavity is far away from the central axis of the core block.

[0023] Preferably, a second gap is formed between the opposing mating surfaces of adjacent core block petals, and the second gap is used to accommodate the deformation of the core block petals.

[0024] Preferably, the width of the second gap is 0.2% to 15% of the entire diameter of the core block.

[0025] Preferably, the second gaps are symmetrically distributed relative to the central axis of the core block.

[0026] Preferably, one end surface of the core block is concavely formed with a positioning groove, and the other end surface opposite thereto is convexly formed with a second protrusion;

[0027] Adjacent core blocks are axially positioned by the cooperation between the positioning groove and the second protrusion.

[0028] The present invention also provides a SiC composite cladding fuel rod, which comprises the petal-type nuclear fuel pellet structure described in any one of the above, a SiC composite cladding tube, an air cavity spring, an upper end plug and a lower end plug;

[0029] The upper end plug and the lower end plug are respectively connected to the upper end and the lower end of the SiC composite cladding tube;

[0030] A plurality of the petal-type nuclear fuel pellet structures are sequentially stacked in the inner cavity of the SiC composite material cladding tube along the axial direction of the SiC composite material cladding tube;

[0031] The air cavity spring is arranged in the inner cavity of the SiC composite material cladding tube and is connected between the petal-type nuclear fuel pellet structure and the upper end plug. Beneficial effects

[0032] The present invention has at least the following beneficial effects: (1) Under the push of the elastic member, the outer wall of each pellet petal is tightly attached to the inner wall of the nuclear fuel cladding tube, so that the pellet and the nuclear fuel cladding tube are tightly fitted without gaps, which can ensure uniform circumferential heat transfer of the fuel rod and avoid the occurrence of fuel rod bending caused by uneven irradiation swelling of the cladding; the pellet petal can produce elastic displacement under the support of the elastic member, avoiding transient hard contact between the cladding and the pellet petal, thereby ensuring that the pellet and cladding are tightly fitted without gaps without generating a large reaction force on the cladding. (2) The pellet design with a cavity in the middle can further reduce the operating peak temperature of the pellet, and the cavity can accommodate more fission gas, thereby reducing the internal pressure of the fuel rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0034] FIG1 is a top view of a split-type nuclear fuel pellet structure according to a first embodiment of the present invention;

[0035] FIG2 is a top view of a split-type nuclear fuel pellet structure according to a second embodiment of the present invention;

[0036] FIG3 is a top view of a split-type nuclear fuel pellet structure according to a third embodiment of the present invention;

[0037] FIG4 is a top view of a split-type nuclear fuel pellet structure according to a fourth embodiment of the present invention;

[0038] 5 is a schematic structural diagram of an elastic member of a petal-type nuclear fuel pellet structure according to a fifth embodiment of the present invention;

[0039] FIG6 is a schematic structural diagram of a split-type nuclear fuel pellet structure according to a sixth embodiment of the present invention;

[0040] FIG7 is a schematic structural diagram of a split-type nuclear fuel pellet structure according to a seventh embodiment of the present invention;

[0041] FIG8 is a schematic structural diagram of FIG7 from another perspective;

[0042] FIG9 is a schematic diagram of the structure of a SiC composite cladding fuel rod according to some embodiments of the present invention. Modes for Carrying Out the Invention

[0043] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0044] The terms "axial" and "radial" refer to the length direction of the entire device or component as the "axial" direction, and the direction perpendicular to the axial direction as the "radial" direction.

[0045] The terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features. "Multiple" means two or more, unless otherwise expressly specified.

[0046] The above terms are only for the convenience of description and should not be understood as limiting the present technical solution.

[0047] As shown in Figures 1 to 8, the split-type nuclear fuel pellet structure of the present invention includes a pellet 1 and an elastic member 2. When in use, the pellet 1 and the elastic member 2 are both accommodated in the inner cavity of a nuclear fuel cladding tube 3 (hereinafter referred to as cladding tube 3).

[0048] A cavity 11 for accommodating the elastic member 2 is defined in the middle of the core block 1 .

[0049] The core block 1 includes at least two radially matched core block petals 10, each core block petal 10 includes an inner wall surface 101 facing the central axis of the core block 1 and an outer wall surface 102 facing away from the central axis of the core block 1. The elastic member 2 abuts against the inner wall surface 101 of each core block petal 10 in the cavity 11, pushing the outer wall surface 102 of the core block petal 10 to cling to the inner wall of the cladding tube 3.

[0050] Specifically, in terms of heat transfer performance, each core block petal 10 is pushed by the elastic member 2 to adhere to the inner wall of the nuclear fuel cladding tube 3 with its outer wall surface 102, so that there is a tight fit without gaps between the core block 1 and the cladding tube 3, which can ensure that the circumferential temperature of the cladding tube 3 is relatively uniform, that is, the circumferential heat transfer of the fuel rod is uniform, thereby avoiding the bending of the fuel rod caused by uneven irradiation swelling of the cladding tube 3.

[0051] From the perspective of the applied force, when the cladding tube 3 exerts an applied force on the core block petal 10, the core block petal 10 can produce elastic displacement under the support of the elastic member 2, thereby avoiding transient hard contact between the cladding tube 3 and the core block petal 10, thereby ensuring that the core block 1 and the cladding tube 3 are designed to fit tightly without gaps, while no large reaction force is generated on the cladding tube 3.

[0052] In addition, the design of the pellet 1 with the cavity 11 in the middle can further reduce the peak operating temperature of the pellet 1, and the cavity 11 can accommodate more fission gas, thereby reducing the internal pressure of the fuel rod.

[0053] Furthermore, the elastic member 2 may be an elastic tube or a spring. The elastic tube is placed in the cavity 11 along the extension direction of the cavity 11, and the elastic tube may be an elastic thin-walled tube.

[0054] As shown in FIG1 , in the split-petal nuclear fuel pellet structure of the first embodiment of the present invention, the elastic member 2 is an elliptical tube, and the number of the pellet petals 10 is two.

[0055] Specifically, the cavity 11 may extend along the axial direction of the core block 1 to the opposite end surfaces of the core block 1 , and the two core block petals 10 are arranged opposite to each other to form a nearly complete hollow core block 1 .

[0056] Corresponding to the elliptical tube-shaped elastic member 2, the cross-sectional shape of the central cavity 11 of the core block 1 can also be approximately elliptical. The assembly positioning point is located at the apex of the major axis of the ellipse between the elastic member 2 and the core block petal 10. Before assembling the components, the major axis of the ellipse of the elastic member 2 can be slightly larger than that of the cavity 11. This ensures that after assembly, the core block petal 10 can be pushed by the force of the elastic member 2, so that its outer wall 102 abuts against the inner wall of the cladding tube 3.

[0057] Furthermore, as shown in Figure 1, the elastic member 2 can abut against the inner wall surface 101 of the core block petal 10 with its circumferential surface corresponding to the major axis of the ellipse, and a first gap 41 is formed between the circumferential surface corresponding to the minor axis of the ellipse on the elastic member 2 and the inner wall surface 101 of the core block petal 10. The first gap 41 is used to accommodate the elastic deformation of the elastic member 2.

[0058] Furthermore, as shown in FIG2 , in the split-type nuclear fuel pellet structure of the second embodiment of the present invention, the difference from the above embodiments is that the circumference of the elastic member 2 corresponding to the minor axis of the ellipse is concave to form an inner curvature.

[0059] As shown in FIG2 , the inner curvature can be formed by the circumference of the elastic member 2 corresponding to the minor axis of the ellipse being concave inward along the radial direction of the minor axis of the ellipse. The inner curvature can be roughly in the shape of a U-shaped groove. Alternatively, the inner curvature can also be roughly in the shape of a curved wave.

[0060] Specifically, when the core block petal 10 undergoes intrinsic volume changes and the cladding tube 3 exerts force, causing the elastic member 2 to be squeezed, deformed, or displaced by the core block petal 10, the design of the inner curved portion 20 ensures that the elastic member 2 deforms inward, thereby preventing the circumference of the elastic member 2 near its elliptical minor axis from contacting the inner wall surface 101 of the core block petal 10 during deformation. Furthermore, the inner curved portion 20 reduces the overall stiffness of the elastic member 2, thereby preventing excessive stress from being generated when the core block 1 and the cladding tube 3 come into contact.

[0061] Furthermore, as shown in Figure 3, the third embodiment of the split-petal nuclear fuel pellet structure of the present invention differs from the above-described embodiments in that there are three pellet petals 10, and the circumferential surface of the elastic member 2 has three outwardly projecting first protrusions that abut against the inner wall surfaces 101 of the pellet petals 10. Each first protrusion abuts against the inner wall surface 101 of each pellet petal 10. Recesses are formed between adjacent first protrusions, and first gaps 41 are formed between the recesses and the inner wall surfaces 101 of the pellet petals 10. These first gaps 41 accommodate the elastic deformation of the elastic member 2.

[0062] Similarly, as shown in Figure 4, in the fourth embodiment of the split-petal nuclear fuel pellet structure of the present invention, unlike the above-mentioned embodiments, there are four pellet petals 10. The circumferential surface of the elastic member 2 has four outwardly projecting first protrusions that abut against the inner wall surfaces 101 of the pellet petals 10. Each first protrusion abuts against the inner wall surface 101 of each pellet petal 10. Recesses are formed between adjacent first protrusions, and first gaps 41 are formed between the recesses and the inner wall surfaces 101 of the pellet petals 10. These first gaps 41 accommodate the elastic deformation of the elastic member 2.

[0063] Furthermore, as shown in Figures 3 and 4, two or more recessed portions may be present between adjacent first protrusions. Correspondingly, a third protrusion may be formed between adjacent recessed portions to further accommodate the elastic deformation of the elastic member 2 and enhance the overall rigidity of the elastic member 2. The third protrusion may be provided corresponding to the second gap 42 between the core block petals 10.

[0064] To sum up, when the elastic member 2 is an elastic tube, as shown in Figures 1-4, the cross-sectional shape of the cavity 11 in the middle of the core block 1 can be set to correspond to the cross-sectional shape of the elastic member 2, so that the two are roughly the same shape, so that the elastic member 2 has good coaxiality with the core block 1 in the cavity 11.

[0065] As shown in FIG5 , in the petal-type nuclear fuel pellet structure of the fifth embodiment of the present invention, unlike the above embodiments, to further reduce the stiffness of the elastic member 2, when the elastic member 2 is an elastic tube, at least one through-hole 20 is defined on the circumference of the elastic member 2 to prevent excessive elastic force between the elastic member 2 and the pellet petals 10 due to excessive stiffness. If multiple through-holes 20 are provided, the through-holes 20 may be distributed along the axial direction of the elastic member 2 at intervals.

[0066] Other structural features not mentioned above may be configured with reference to any one of the above embodiments or in combination with multiple embodiments, and will not be described in detail here. The size and number of through holes 20 can be further determined by taking into account factors such as the required elastic force, without affecting the role played by the elastic member 2 itself in the corresponding technical solution described in conjunction with the embodiments disclosed in the present invention.

[0067] As shown in Figure 6 , in the sixth embodiment of the split-petal nuclear fuel pellet structure of the present invention, unlike the previous embodiments, the elastic member 2 is a spring, specifically a coil spring. There are also two pellet petals 10, which are arranged opposite each other to form a nearly complete hollow pellet 1. The mating surfaces of the two pellet petals 10 are concave to form cavities 11. The elastic member 2 is accommodated in these cavities 11, with its opposing ends abutting against the inner bottom surfaces 103 of the cavities 11 of the two pellet petals 10.

[0068] Furthermore, the inner wall surface 101 of the two core block petals 10 can be concave inward along the radial direction of the core block 1 to form a cavity 11, and the elastic member 2 is accommodated in the cavity 11 of the two core block petals 10, and its opposite ends can be pressed against the inner bottom surface 103 of the cavity 11 of the two core block petals 10 along the radial direction of the core block 1.

[0069] Specifically, the cavity 11 can be similar to a blind hole of a certain depth. The elastic member 2 is entirely disposed transversely within the blind hole, with its opposite ends connected and fixed to the inner wall surfaces 101 of the two core block petals 10. Similarly, the elastic deformation of the elastic member 2 can push the two oppositely arranged core block petals 10, causing the outer wall surfaces 102 of the two core block petals 10 to tightly fit against the inner wall of the cladding tube 3, thereby forming a gap-free, tight fit between the core block 1 and the cladding tube 3.

[0070] Furthermore, the cavity 11 may be in the shape of a stepped hole. The cavity 11 may include a first cavity 111 and a second cavity 112 that are connected to each other. The inner circumference of the first cavity 111 is larger than the inner circumference of the second cavity 112. The first cavity 111 is close to the central axis of the core block 1, and the second cavity 112 is far from the central axis of the core block 1.

[0071] When the first cavity 111 or the second cavity 112 is a circular hole, its inner circumference size refers to the inner diameter. When the first cavity 111 or the second cavity 112 is a square hole, its inner circumference size refers to the inner circumference width. When the first cavity 111 or the second cavity 112 is a rectangular hole, its inner circumference size refers to the inner circumference width. When the first cavity 111 or the second cavity 112 is a hole of other shapes, its inner circumference size may refer to the maximum inner circumference width.

[0072] The opposite ends of the elastic member 2 abut against the inner wall surfaces 101 of the two core block petals 10 in the second cavity 112 , and the middle portion of the elastic member 2 is located in the first cavity 111 and is spaced apart from the inner wall surfaces 101 of the core block petals 10 .

[0073] Specifically, in order to prevent the risk of stress relaxation or melting of the elastic member 2 due to excessively high temperature in the central area near the central axis of the core block 1, the cavity 11 exists in the form of a stepped hole, so that the high-temperature area in the center of the core block 1 is separated from the middle part of the elastic member 2 by a certain distance, thereby reducing the operating temperature of the elastic member 2 and reducing the risk of stress relaxation or melting thereof.

[0074] Furthermore, a second gap 42 may be formed between the opposing mating surfaces of adjacent core block petals 10. The second gap 42 is used to accommodate deformation of the core block petals 10 and to allow for deformation margins due to volume changes in the core block petals 10. Other structural features not mentioned herein may be configured with reference to any one of the above embodiments or in combination with multiple embodiments, and are not further described here.

[0075] Specifically, when the heating power of the fuel rod increases abnormally, the pellet 1 will produce intrinsic volume changes such as radiation swelling and thermal expansion. At this time, the deformation margin between the two adjacent core block petals 10 can be used to accommodate the above-mentioned intrinsic volume changes and prevent the pellet 1 from deforming outward and exerting a large force on the cladding tube 3.

[0076] Furthermore, considering the circumferential heat transfer distribution of the cladding tube 3, the width of the second gap 42 can be 0.2% to 15% of the overall diameter of the core block 1, so as to leave a deformation margin for the volume change of the core block petals 10 while achieving better circumferential heat transfer distribution of the cladding.

[0077] Furthermore, the second gaps 42 are symmetrically distributed relative to the central axis of the core block 1, so that the core block 1 has a more uniform circumferential heat transfer distribution effect within the cladding tube 3. For example, when there are two core block petals 10, the second gaps 42 are relatively symmetrically distributed about the central axis of the core block 1. When there are three or more core block petals 10, the second gaps 42 are centrally symmetrically distributed about the central axis of the core block 1.

[0078] As shown in Figures 7-8, in the petal-type nuclear fuel core block structure of the seventh embodiment of the present invention, unlike the above-mentioned embodiments, one end face of each core block 1 is concave to form a positioning groove 70, and the other opposite end face is convex to form a second protrusion 71; the core blocks 1 adjacent to each other along the axial direction can be axially positioned by matching the positioning groove 70 and the second protrusion 71.

[0079] Specifically, the arrangement of the positioning groove 70 and the second protrusion 71 ensures a better circumferential fit between the two axially adjacent core block petals 10. After the core block petals 10 are assembled into the cladding tube 3, the circumferential positions of the multiple axial core block petals 10 remain the same, thereby ensuring that the core block petals 10 at different axial heights have the same circumferential structure and heat transfer performance, and the cavities 11 and elastic parts 2 at different axial heights can also be maintained in approximately the same position, so that the petal-type nuclear fuel core block structure has better integrity in the cladding tube 3, ensuring that the overall circumferential temperature of the cladding tube 3 is uniform, and avoiding the occurrence of fuel rod bending caused by uneven irradiation swelling of the cladding tube 3.

[0080] Furthermore, in the split-type nuclear fuel pellet structure of the present invention, the pellet petals 10 can be made of uranium dioxide, uranium silicide, uranium nitride, uranium carbide, uranium carbon oxide, or the like. The elastic member 2 can be made of a nickel-based alloy, a molybdenum alloy, stainless steel, an aluminum alloy, a zirconium alloy, or the like. The cladding tube 3 used in conjunction with the split-type nuclear fuel pellet structure can be made of a zirconium alloy, a SiC composite material, or the like.

[0081] As shown in FIG9 , the SiC composite cladding tube fuel rod according to an embodiment of the present invention includes the above-mentioned split-type nuclear fuel pellet structure, a SiC composite cladding tube 30 , an air cavity spring 5 , an upper end plug 60 and a lower end plug 61 .

[0082] The upper end plug 60 and the lower end plug 61 are respectively connected to the upper and lower ends of the SiC composite cladding tube 30; a plurality of petal-type nuclear fuel pellet structures are stacked in sequence in the inner cavity of the SiC composite cladding tube 30 along the axial direction of the SiC composite cladding tube 30, and the plurality of petal-type nuclear fuel pellet structures are coaxially arranged with the SiC composite cladding tube 30; the air cavity spring 5 is arranged in the inner cavity of the SiC composite cladding tube 30 and is connected between the petal-type nuclear fuel pellet structure and the upper end plug 60.

[0083] The above are only some specific embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A split-type nuclear fuel pellet structure, characterized in that: It comprises a core block (1) and an elastic member (2); A cavity (11) for accommodating the elastic member (2) is provided in the middle of the core block (1); The core block (1) comprises at least two radially matched core block petals (10), and the elastic member (2) is accommodated in the cavity (11) and abuts against each of the core block petals (10).

2. The split-type nuclear fuel pellet structure according to claim 1, characterized in that: The cavity (11) is arranged to extend along the axial direction of the core block (1); The elastic member (2) is an elastic tube, and is placed in the cavity (11) along the extension direction of the cavity (11).

3. The split-type nuclear fuel pellet structure according to claim 2, characterized in that: The number of the core block petals (10) is two, and the elastic member (2) is an elliptical tube; The elastic member (2) abuts against the core block petal (10) with its circumferential surface corresponding to the major axis of the ellipse, and a first gap (41) is formed between the circumferential surface of the elastic member (2) corresponding to the minor axis of the ellipse and the core block petal (10), and the first gap (41) is used to accommodate the elastic deformation of the elastic member (2).

4. The split-type nuclear fuel pellet structure according to claim 3, characterized in that: The elastic member (2) has an inner curved portion formed inwardly on its circumferential surface corresponding to the minor axis of the ellipse.

5. The split-type nuclear fuel pellet structure according to claim 2, characterized in that: The number of the core block petals (10) is at least three, and the circumferential surface of the elastic member (2) has at least three first protrusions protruding outward and abutting against the core block petals (10), and recesses are formed correspondingly between adjacent first protrusions, and a first gap (41) is formed between the recessed portions and the core block petals (10), and the first gap (41) is used to accommodate the elastic deformation of the elastic member (2).

6. The split-type nuclear fuel pellet structure according to claim 2, characterized in that: At least one through hole (20) is provided on the circumferential surface of the elastic member (2).

7. The split-type nuclear fuel pellet structure according to claim 1, characterized in that: The elastic member (2) is a spring, and the number of the core block petals (10) is two; The relative mating surfaces of the two core block petals (10) are respectively concave, forming the cavity (11) on each of the core block petals (10); the elastic member (2) is accommodated in the cavity (11) of the two core block petals (10), and its two opposite ends respectively press against the inner bottom surface (103) of the cavity (11) of the two core block petals (10).

8. The split-type nuclear fuel pellet structure according to claim 7, characterized in that: The cavity (11) is in the shape of a stepped hole, comprising a first cavity (111) and a second cavity (112) that are connected to each other, the inner circumference of the first cavity (111) being larger than the inner circumference of the second cavity (112), the first cavity (111) being close to the central axis of the core block (1), and the second cavity (112) being far from the central axis of the core block (1).

9. The split-type nuclear fuel pellet structure according to any one of claims 1 to 8, characterized in that: A second gap (42) is formed between the relative mating surfaces of adjacent core block petals (10), and the second gap (42) is used to accommodate the deformation of the core block petals (10).

10. The split-type nuclear fuel pellet structure according to claim 9, characterized in that: The width of the second gap (41) is 0.2% to 15% of the overall diameter of the core block (1).

11. The split-type nuclear fuel pellet structure according to claim 9, characterized in that: The second gap (42) is symmetrically distributed relative to the central axis of the core block (1).

12. The split-type nuclear fuel pellet structure according to any one of claims 1 to 8, characterized in that: One end surface of the core block (1) is concavely formed with a positioning groove (70), and the other end surface opposite thereto is convexly formed with a second protrusion (71); Adjacent core blocks (1) are axially positioned by the cooperation of the positioning grooves (70) and the second protrusions (71).

13. A SiC composite cladding fuel rod, characterized in that: It comprises the split-type nuclear fuel pellet structure according to any one of claims 1 to 12, a SiC composite cladding tube (30), an air cavity spring (5), an upper end plug (60) and a lower end plug (61); The upper end plug (60) and the lower end plug (61) are respectively connected to the upper end and the lower end of the SiC composite material cladding tube (30) which are opposite to each other; A plurality of the split-type nuclear fuel pellet structures are sequentially stacked in the inner cavity of the SiC composite material cladding tube (30) along the axial direction of the SiC composite material cladding tube (30); The air cavity spring (5) is arranged in the inner cavity of the SiC composite material cladding tube (30) and is connected between the split-type nuclear fuel core block structure and the upper end plug (60).

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