Fast reactor control rod assembly with high reactor value

Abstract

The invention particularly relates to a high-reactivity-value fast reactor control rod assembly, which belongs to the technical field of fast reactor control rod assembly design and manufacturing, and comprises a cladding, and a fuel rod and a boron carbide absorption rod which are fixed in the cladding; the fuel rod and the boron carbide absorption rod are connected together through the connecting rod; a connector is arranged at one end of the cladding and used for being connected with a control rod driving mechanism corresponding to the control rod assembly; a pin is arranged at the other end of the cladding and is used for being inserted into a slot of a large grid tray header or a small grid tray header of a fast reactor core corresponding to the control rod assembly; the control rod driving mechanism drives the control rod assembly to move up and down in the fast reactor core according to an operation instruction of the fast reactor; the fuel rod is away from the connector, and the boron carbide absorption rod is close to the connector. The fuel pellets and the boron carbide pellets are arranged at different heights in a layered manner in the axial direction, so that the reactivity value of the fast reactor control rod assembly is improved, and the fast reactor control rod assembly with high reactivity value is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of design and manufacturing of a fast reactor control rod assembly, in particular to a high-reactivity value fast reactor control rod assembly. Background Art

[0002] The control rod assemblies of China's experimental fast reactor and demonstration fast reactor both use enriched boron carbide pellets as neutron absorbing materials, among which the effective neutron absorbing element is B-10. The control rod assemblies of Russia's BN series fast reactor units and European and American fast reactor units also adopt similar design methods. The reactivity value of the control rod assembly designed using the above scheme is related to the abundance of B-10 in the boron carbide pellets. The higher the B-10 abundance, the higher the neutron absorption rate and the greater the reactivity value of the control rod assembly. At present, the B-10 abundance in the boron carbide pellets of the control rod assembly that performs the safe shutdown function in the demonstration fast reactor has reached 92%. The maximum abundance of B-10 in the boron carbide pellets can only reach 100%, and the reactivity value of this type of control rod assembly will be difficult to further improve in the future. Therefore, it is necessary to study other new schemes that can improve the reactivity value of fast reactor control rod assemblies. Summary of the invention

[0003] The purpose of the present invention is to provide a fast reactor control rod assembly with high reactivity value, which improves the reactivity value of the fast reactor control rod assembly by arranging fuel pellets and boron carbide pellets in layers at different heights in the axial direction, thereby obtaining a fast reactor control rod assembly with high reactivity value.

[0004] In order to achieve the above object, the present invention provides the following technical solutions: A high-reactivity value fast reactor control rod assembly comprises a cladding, and fuel rods and boron carbide absorber rods fixed in the cladding; the fuel rods and the boron carbide absorber rods are connected together by connecting rods; a connector is provided at one end of the cladding for connecting with a control rod drive mechanism corresponding to the control rod assembly; a pin is provided at the other end of the cladding for inserting into a slot of a large grid plate header or a small grid plate header of a fast reactor core corresponding to the control rod assembly; the control rod drive mechanism drives the control rod assembly to move up and down in the fast reactor core according to the operation instructions of the fast reactor; the fuel rods are away from the connector, and the boron carbide absorber rods are close to the connector.

[0005] As one feasible method, the length of the fuel rod and the boron carbide absorber rod are both 45 to 55 mm shorter than the length of the active zone of the fast reactor core; the length of the fuel rod and the boron carbide absorber rod are both 850 to 950 mm; and the length of the connecting rod is 90 to 110 mm.

[0006] As one of the achievable methods, the up and down movement stroke of the control rod drive mechanism corresponding to the control rod assembly is 1790 to 2010 mm.

[0007] As one of the feasible ways, when the control rod drive mechanism corresponding to the control rod assembly moves to the upper limit of the stroke, the top of the fuel rod in the control rod assembly is 45 to 55 mm lower than the horizontal plane of the top of the fast reactor core active zone, and the bottom of the boron carbide absorber rod is 45 to 55 mm higher than the horizontal plane of the top of the fast reactor core active zone. All the fuel rods in the control rod assembly are within the fast reactor core active zone, and all the boron carbide absorber rods are outside the fast reactor core active zone.

[0008] As one of the feasible ways, when the control rod drive mechanism corresponding to the control rod assembly moves to the lower limit of the stroke, the top of the fuel rod in the control rod assembly is 45 to 55 mm lower than the horizontal plane of the bottom of the fast reactor core active zone, the bottom of the boron carbide absorber rod is 45 to 55 mm higher than the horizontal plane of the bottom of the fast reactor core active zone, all the fuel rods in the control rod assembly are outside the fast reactor core active zone, and all the boron carbide absorber rods are inside the fast reactor core active zone.

[0009] As one of the achievable methods, the bottom slots of the small grid plate header and the large grid plate header of the fast reactor core corresponding to the control rod assembly are both sinker-type slots; the length of the sinker-type slots is 1400-1500 mm; When the control rod assembly is inserted downward, the fuel rods in the control rod assembly withdraw from the active region of the fast reactor core and are gradually inserted into the slots of the large grid plate header or the small grid plate header of the fast reactor core corresponding to the control rod assembly, while the boron carbide absorber rods in the control rod assembly are inserted into the active region of the fast reactor core; When the control rod assembly is lifted, the boron carbide absorber rods in the control rod assembly withdraw from the active region of the fast reactor core, while the fuel rods in the control rod assembly are gradually lifted to the active region of the fast reactor core.

[0010] As one possible implementation method, assuming that the axial position coordinate of the control rod assembly before insertion is S(1) and the axial position coordinate after insertion is S(2), the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to the following steps: The effective proliferation factors keff(1) and keff(2) of the fast reactor core are calculated using a general core design software when the control rod assembly is at the axial position S(1) and axial position S(2). The reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to formula (1): Wherein, ρ is the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2); keff(1) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(1); keff(2) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(2).

[0011] As one of the possible implementations, the flow distribution of the control rod assembly is achieved by the following steps: Solving formula (2) yields the flow rate distributed by the control rod assembly; The surface temperature of the control rod assembly cladding is calculated according to formula (2), and the maximum temperature of the control rod assembly cladding wall is required not to exceed 600°C; Formula (2) is: Formula (3) is: in, is the total flow rate of the fast reactor core, in kg / s; For components i Flow rate, in kg / s; is the total pressure drop of the flow channel of component i, in kPa; For components i Pressure drop, in kPa; For components i The grid pressure drop, in kPa; is the function conversion coefficient of the flow rate of component i and the total pressure drop of the flow channel of component i, which is obtained through hydraulic tests; q(z) is the linear power density at the z plane of the control rod assembly, in W / m 2 ; h is the surface heat transfer coefficient of the fast reactor core coolant; T w (z) is the cladding wall temperature at the z plane of the control rod assembly, in °C; T f (z) is the fast reactor core coolant temperature at the z plane of the control rod assembly, in °C.

[0012] As one possible approach, the connecting rod is made of stainless steel.

[0013] Beneficial technical effects of the present invention: The high reactivity value fast reactor control rod assembly of the present invention fully utilizes the cavity formed in the fast reactor core when the control rod assembly is lifted to the top of the fast reactor core active area, which not only increases the effective uranium loading of the fast reactor core and reduces the critical diameter of the fast reactor core, but also can effectively improve the reactivity value of a single control rod assembly; the reactivity value is 1.5 to 2 times that of an ordinary control rod assembly, and the number of control rod assemblies can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of an embodiment of a high reactivity value fast reactor control rod assembly of the present invention; Figure 2A schematic diagram of the axial position of a fast reactor core in an embodiment when a control rod drive mechanism corresponding to a control rod assembly moves to an upper limit of the stroke; Figure 3 A schematic diagram of the axial position of a fast reactor core in an embodiment when a control rod drive mechanism corresponding to a control rod assembly moves to a lower limit of travel; Figure 4 It is a structural schematic diagram of an embodiment of a sinking slot; Figure 5 A schematic diagram of one embodiment of flow distribution for a fast reactor core assembly.

[0015] In the figure, 1. Boron carbide absorber rod; 2. Fuel rod; 3. Top horizontal plane of fast reactor core active area; 4. Bottom horizontal plane of fast reactor core active area; 5. Small grid plate header; 6. Settlement slot; 7. Large grid plate header. DETAILED DESCRIPTION

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0017] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0018] In the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connection" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0019] The terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of the elements listed and may also include additional elements not expressly listed.

[0020] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0021] See also Figure 1The present embodiment provides a high reactivity value fast reactor control rod assembly, comprising a cladding and a fuel rod 2 and a boron carbide absorber rod 1 fixed in the cladding; the fuel rod 2 and the boron carbide absorber rod 1 are connected together by a connecting rod; a connector is provided at one end of the cladding for connecting with a control rod drive mechanism corresponding to the control rod assembly; a pin is provided at the other end of the cladding for inserting into a slot of a large grid header 7 or a small grid header 5 of a fast reactor core corresponding to the control rod assembly; the control rod drive mechanism drives the control rod assembly to move up and down in the fast reactor core according to the operation instruction of the fast reactor; the fuel rod 2 is away from the connector, and the boron carbide absorber rod 1 is close to the connector.

[0022] The control rod assembly of the present invention provides a certain positive reactivity within the active region of the fast reactor core when the control rod assembly is pulled out of the fast reactor core, thereby increasing the total amount of metallic uranium fuel in the fast reactor core and reducing the average power density of the fast reactor core; when the control rod assembly is inserted into the fast reactor core, the fuel core blocks in the control rod assembly move out of the active region of the fast reactor core, and the boron carbide core blocks enter the active region of the fast reactor core to absorb neutrons and introduce negative reactivity; such a design scheme can not only improve the fuel utilization rate of the fast reactor core, but also effectively improve the reactivity value of a single control rod assembly.

[0023] When a common control rod assembly exits a fast reactor core, a cavity is formed in the fast reactor core, and the cavity is generally filled with an inert gas or a fast reactor core coolant. The control rod assembly of the present invention adds a fuel rod 2 in the axial direction. When the boron carbide absorber rod 1 moves to the top of the fast reactor core active area, the fuel rod 2 just fills the cavity formed when the boron carbide absorber rod 1 leaves, and increases the fissile nuclides in the fast reactor core, and the effective uranium loading of the fast reactor core is also increased accordingly; under the same critical calculation conditions, after the effective uranium loading of the fast reactor core is increased, the corresponding critical diameter of the fast reactor core is also reduced accordingly.

[0024] See also Figure 1 In this embodiment, as one of the feasible ways, the lengths of the fuel rod 2 and the boron carbide absorber rod 1 are both 45 to 55 mm shorter than the length of the active zone of the fast reactor core; the lengths of the fuel rod 2 and the boron carbide absorber rod 1 are both 850 to 950 mm; and the length of the connecting rod is 90 to 110 mm.

[0025] In this embodiment, as one of the achievable modes, the stroke of the control rod drive mechanism corresponding to the control rod assembly is 1790-2010 mm. The stroke of the control rod drive mechanism corresponding to the ordinary control rod assembly is generally 850-950 mm. The stroke of the control rod drive mechanism corresponding to the control rod assembly of the present invention is significantly higher than the stroke of the control rod drive mechanism corresponding to the ordinary control rod assembly.

[0026] See also Figure 2In this embodiment, as one of the achievable ways, when the control rod drive mechanism corresponding to the control rod assembly moves to the upper limit of the stroke, the top of the fuel rod 2 in the control rod assembly is 3 (45-55) mm lower than the top horizontal plane of the fast reactor core active zone, and the bottom of the boron carbide absorber rod 1 is 3 (45-55) mm higher than the top horizontal plane of the fast reactor core active zone, so as to ensure that all the fuel rods 2 in the control rod assembly are within the fast reactor core active zone, and all the boron carbide absorber rods 1 are outside the fast reactor core active zone.

[0027] See also Figure 3 In this embodiment, as one of the achievable ways, when the control rod drive mechanism corresponding to the control rod assembly moves to the lower limit of the stroke, the top of the fuel rod 2 in the control rod assembly is 4 (45-55) mm lower than the horizontal plane of the bottom of the fast reactor core active area, and the bottom of the boron carbide absorber rod 1 is 4 (45-55) mm higher than the horizontal plane of the bottom of the fast reactor core active area, so as to ensure that all the fuel rods 2 in the control rod assembly are outside the fast reactor core active area, and all the boron carbide absorber rods 1 are inside the fast reactor core active area.

[0028] See also Figure 4 In this embodiment, as one of the achievable methods, since the stroke of the control rod assembly moving up and down is longer, in order to match the stroke of the control rod assembly moving up and down, the bottom slots of the small grid plate header 5 and the large grid plate header 7 of the fast reactor core corresponding to the control rod assembly are both sinking slots 6; the length of the sinking slots 6 is 1400-1500 mm, which is convenient for accommodating the pins of the control rod assembly and the fuel rods 2; When the control rod assembly is inserted downward, the fuel rod 2 in the control rod assembly withdraws from the active area of ​​the fast reactor core and is gradually inserted into the slot of the large grid plate header 7 or the small grid plate header 5 of the fast reactor core corresponding to the control rod assembly, while the boron carbide absorber rod 1 in the control rod assembly is inserted into the active area of ​​the fast reactor core; the fuel rod 2 contains a large amount of fissile nuclides, and after withdrawing from the active area of ​​the fast reactor core, the nuclear reaction rate in the area where the control rod assembly is located will be reduced, and at the same time, after the boron carbide absorber rod 1 is inserted into the active area of ​​the fast reactor core, the B-10 atoms therein have a strong absorption effect on neutrons, and the reaction rate in the area where the control rod assembly is located will be further reduced; When the control rod assembly is lifted, the boron carbide absorber rod 1 in the control rod assembly withdraws from the active area of ​​the fast reactor core, while the fuel rod 2 in the control rod assembly is gradually lifted to the active area of ​​the fast reactor core; after the neutron absorbing material in the area where the control rod assembly is located withdraws, more fissile nuclides are introduced, and the nuclear reaction in the area where the control rod assembly is located will increase.

[0029] When an ordinary control rod assembly withdraws from the active zone of the fast reactor core, no fuel rod 2 is introduced, and the fissile nuclides in the core are not increased; when an ordinary control rod assembly is inserted into the active zone of the fast reactor core, the fissile nuclides in the fast reactor core are reduced. Therefore, the reactivity value of the control rod assembly of the present invention is higher than that of the ordinary control rod assembly.

[0030] In this embodiment, as one of the achievable methods, assuming that the axial position coordinate of the control rod assembly before insertion is S(1), and the axial position coordinate after insertion is S(2), the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to the following steps: The effective proliferation factors keff(1) and keff(2) of the fast reactor core are calculated using a general core design software when the control rod assembly is at the axial position S(1) and axial position S(2). The reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to formula (1): Wherein, ρ is the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2); keff(1) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(1); keff(2) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(2).

[0031] The control rod assembly of the present invention contains fuel pellet rods, which have higher heating power than ordinary control rods and higher requirements for flow distribution than ordinary control rod assemblies. Figure 5 In this embodiment, as one of the achievable methods, the flow distribution of the control rod assembly is achieved by the following steps: Solving formula (2) yields the flow rate distributed by the control rod assembly; The surface temperature of the control rod assembly cladding is calculated according to formula (3), and the maximum temperature of the control rod assembly cladding wall is required not to exceed 600°C; Formula (2) is: Formula (3) is: in, is the total flow rate of the fast reactor core, in kg / s; For components i Flow rate, in kg / s; is the total pressure drop of the flow channel of component i, in kPa; For components i Pressure drop, in kPa; For components i The grid pressure drop, in kPa; is the function conversion coefficient of the flow rate of component i and the total pressure drop of the flow channel of component i, which is obtained through hydraulic tests; q(z) is the linear power density at the z plane of the control rod assembly, in W / m 2 ; h is the surface heat transfer coefficient of the fast reactor core coolant; T w (z) is the cladding wall temperature at the z plane of the control rod assembly, in °C; T f (z) is the fast reactor core coolant temperature at the z plane of the control rod assembly, in °C.

[0032] In this embodiment, as one of the feasible ways, the connecting rod is made of stainless steel.

[0033] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high reactivity value fast reactor control rod assembly, characterized in that: The invention comprises a cladding, a fuel rod (2) and a boron carbide absorber rod (1) fixed in the cladding; the fuel rod (2) and the boron carbide absorber rod (1) are connected together via a connecting rod; a connecting head is provided at one end of the cladding for connecting to a control rod drive mechanism corresponding to the control rod assembly; a pin is provided at the other end of the cladding for inserting into a slot of a large grid plate header (7) or a small grid plate header (5) of a fast reactor core corresponding to the control rod assembly; the control rod drive mechanism drives the control rod assembly to move up and down in the fast reactor core according to the operation instruction of the fast reactor; the fuel rod (2) is away from the connecting head, and the boron carbide absorber rod (1) is close to the connecting head.

2. The high reactivity value fast reactor control rod assembly according to claim 1, characterized in that: The lengths of the fuel rods (2) and the boron carbide absorber rods (1) are both 45 to 55 mm shorter than the length of the active region of the fast reactor core; the lengths of the fuel rods (2) and the boron carbide absorber rods (1) are both 850 to 950 mm; and the length of the connecting rods is 90 to 110 mm.

3. The high reactivity value fast reactor control rod assembly according to claim 2, characterized in that: The up and down movement stroke of the control rod drive mechanism corresponding to the control rod assembly is 1790 to 2010 mm.

4. The high reactivity value fast reactor control rod assembly according to claim 2, characterized in that: When the control rod drive mechanism corresponding to the control rod assembly moves to the upper limit of the stroke, the top of the fuel rod (2) in the control rod assembly is 45 to 55 mm lower than the top horizontal plane (3) of the fast reactor core active region, and the bottom of the boron carbide absorber rod (1) is 45 to 55 mm higher than the top horizontal plane (3) of the fast reactor core active region; all the fuel rods (2) in the control rod assembly are within the fast reactor core active region, and all the boron carbide absorber rods (1) are outside the fast reactor core active region.

5. The high reactivity value fast reactor control rod assembly according to claim 2, characterized in that: When the control rod drive mechanism corresponding to the control rod assembly moves to the lower limit of the stroke, the top of the fuel rod (2) in the control rod assembly is 45 to 55 mm lower than the horizontal plane (4) at the bottom of the fast reactor core active region, and the bottom of the boron carbide absorber rod (1) is 45 to 55 mm higher than the horizontal plane (4) at the bottom of the fast reactor core active region; all the fuel rods (2) in the control rod assembly are outside the fast reactor core active region, and all the boron carbide absorber rods (1) are inside the fast reactor core active region.

6. The high reactivity value fast reactor control rod assembly according to claim 2, characterized in that: The bottom slots of the fast reactor core small grid plate header (5) and the large grid plate header (7) corresponding to the control rod assembly are both sinker-type slots (6); the length of the sinker-type slots (6) is 1400-1500 mm; When the control rod assembly is inserted downward, the fuel rod (2) in the control rod assembly withdraws from the active region of the fast reactor core and is gradually inserted into the slot of the large grid plate header (7) or the small grid plate header (5) of the fast reactor core corresponding to the control rod assembly, while the boron carbide absorber rod (1) in the control rod assembly is inserted into the active region of the fast reactor core; When the control rod assembly is lifted, the boron carbide absorber rods (1) in the control rod assembly withdraw from the active region of the fast reactor core, while the fuel rods (2) in the control rod assembly are gradually lifted to the active region of the fast reactor core.

7. The high reactivity value fast reactor control rod assembly according to claim 1, characterized in that: Assuming that the axial position coordinate of the control rod assembly before insertion is S(1) and the axial position coordinate after insertion is S(2), the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to the following steps: The effective proliferation factors keff(1) and keff(2) of the fast reactor core are calculated using a general core design software when the control rod assembly is at the axial position S(1) and axial position S(2). The reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2) is calculated according to formula (1): Wherein, ρ is the reactivity value introduced after the control rod assembly is inserted from the axial position S(1) to the axial position S(2); keff(1) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(1); keff(2) is the effective proliferation factor of the fast reactor core when the control rod assembly is at the axial position S(2).

8. The high reactivity value fast reactor control rod assembly according to claim 1, characterized in that: The flow distribution of the control rod assembly is achieved by the following steps: Solving formula (2) yields the flow rate distributed by the control rod assembly; The surface temperature of the control rod assembly cladding is calculated according to formula (3), and the maximum temperature of the control rod assembly cladding wall is required not to exceed 600°C; Formula (2) is: Formula (3) is: in, is the total flow rate of the fast reactor core, in kg / s; For components i Flow rate, in kg / s; is the total pressure drop of the flow channel of component i, in kPa; is the pressure drop of component i, in kPa; is the grid pressure drop of component i, in kPa; is the function conversion coefficient of the flow rate of component i and the total pressure drop of the flow channel of component i, which is obtained through hydraulic tests; q(z) is the linear power density at the z plane of the control rod assembly, in W / m 2 ; h is the surface heat transfer coefficient of the fast reactor core coolant; T w (z) is the cladding wall temperature at the z plane of the control rod assembly, in °C; T f (z) is the fast reactor core coolant temperature at the z plane of the control rod assembly, in °C.

9. The high reactivity value fast reactor control rod assembly according to claim 1, characterized in that: The connecting rod is made of stainless steel.

Images