Nuclear reactor reactivity control cylinder and control method

Abstract

The invention discloses a nuclear reactor reactivity control cylinder and a control method, and belongs to the technical field of nuclear reactor reactivity control. The nuclear reactor reactivity control cylinder comprises a first fixed reflecting layer arranged on the periphery of a reactor core and a plurality of cylinder bodies, the reactor core is provided with a longitudinal central axis, the plurality of cylinder bodies are sequentially and coaxially arranged between the reactor core and the first fixed reflecting layer in a sleeving mode from inside to outside with the longitudinal central axis as the center, and the cylinder bodies are all connected with rotary drivers. And the same number of absorbing layers are uniformly arranged on each barrel body at intervals along the circumference of the barrel body. According to the nuclear reactor reactivity control cylinder and the control method, it can be guaranteed that fuel consumption in all radial directions in a reactor core is uniform due to the absorption / reflection effect in long-term operation, meanwhile, the total mass volume of an absorption layer is not increased, and the energy consumption of the reactor core is reduced on the premise that the neutron economy or utilization rate is kept. And the controllable reactivity range of the barrel is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor reactivity control, and in particular to a nuclear reactor reactivity control tube and a control method. Background Art

[0002] For compact small-scale ground nuclear reactors, some existing control technologies can adjust the absorption rate and reflectivity of neutrons by changing the relative position of the absorber and the reflective layer, thereby regulating the reactivity. For example, a control drum is provided with a crescent-shaped or arc-shaped neutron absorbing material on the side of a circular control drum, and the control drum is arranged in a reflective material layer outside the core. When the neutron absorbing material in the control drum is rotated away from the core, the absorption efficiency is reduced; by rotating the control drum, the neutron absorbing material is brought close to the core, thereby improving the absorption efficiency. However, it cannot be guaranteed that during the long-term operation of the nuclear reactor, the control-related absorption / reflection effects will have a uniform effect on the fuel consumption in all directions in the reactor core. At the same time, under the existing technology, it is difficult to expand the controllable reactivity range while keeping the total mass volume of the absorbing material unchanged. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems in the prior art and to provide a nuclear reactor reactivity control tube and a control method that can ensure that the fuel consumption in all radial directions in the reactor core due to the absorption / reflection effect during long-term operation is uniform, while achieving the purpose of improving the controllable reactivity range of the tube without increasing the total mass volume of the absorption layer and while maintaining the neutron economy or utilization rate.

[0004] The reactivity control tube of a nuclear reactor provided by the present invention comprises a first fixed reflection layer arranged on the periphery of a core, wherein the core has a longitudinal central axis, and further comprises:

[0005] A plurality of cylinders are coaxially sleeved in sequence from the inside to the outside, with the longitudinal central axis as the center, between the core and the first fixed reflective layer. Each cylinder is provided with an absorption layer evenly spaced along its circumference, and the number of absorption layers on each cylinder is the same. The absorption layers on different cylinders can overlap along the radial direction of the cylinder, and when the positions of the absorption layers are all misaligned, they can at least jointly occupy an angle range of 360° centered on the longitudinal central axis;

[0006] The rotary driver is connected to each of the cylinders to drive each of the cylinders to rotate around the longitudinal center axis.

[0007] Preferably, the sum of the angular ranges occupied by the absorption layer on any cylinder centered on the longitudinal central axis is 360° / N, and the number of the cylinders is greater than N.

[0008] Preferably, the innermost cylinder is in close contact with the core, and adjacent cylinders are in close contact with each other.

[0009] Preferably, an annular groove is provided on the inner wall of the cylinder, and the annular groove is arranged with the longitudinal central axis as the center. Balls are provided in an annular array on the outer wall of the cylinder. The position of the balls on the inner cylinder corresponds to the position of the annular groove on the outer adjacent cylinder, so that the balls roll in the corresponding annular grooves.

[0010] Preferably, the core is divided into multiple sections along the longitudinal center axis, and multiple cylinders are coaxially sleeved from inside to outside between each section of the core and the first fixed reflective layer, and each cylinder is connected to a rotating driver respectively.

[0011] Preferably, the rotary drivers correspond to the barrels one by one, and each rotary driver comprises:

[0012] A fixed gear coaxially fixedly connected to one end of the corresponding cylinder;

[0013] A transmission gear meshing with the fixed gear;

[0014] A driving part connected to the transmission gear via a clutch device, the clutch device is used to connect or disconnect the driving part from the transmission gear, and when the driving part is connected to the transmission gear, the driving part is used to drive the transmission gear to rotate;

[0015] An elastic reset member is connected to the transmission gear to prevent the transmission gear from leaving an initial position.

[0016] Preferably, the rotary drivers correspond to the barrels one by one, and each rotary driver comprises:

[0017] A fixed gear coaxially fixedly connected to one end of the corresponding cylinder;

[0018] A transmission rack meshing with the fixed gear;

[0019] A driving part connected to the transmission rack through a clutch device, the clutch device is used to connect or disconnect the driving part from the transmission rack, and when the driving part is connected to the transmission rack, the driving part is used to drive the transmission rack to translate;

[0020] An elastic reset member is connected to the transmission rack to prevent the transmission rack from leaving an initial position.

[0021] Preferably, the fixed gears are all sector gears, and the sector gears on each of the cylinders are staggered in the circumferential direction.

[0022] Any of the above-mentioned control methods for a nuclear reactor reactivity control cylinder includes driving each cylinder to rotate synchronously in the same direction by a rotary driver when the angle range jointly occupied by the positions of each absorption layer is less than 360°.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The novel cylinder body of the present invention can ensure uniform fuel consumption in radial directions in the reactor core due to absorption / reflection effects during long-term operation by rotating the cylinder bodies. By making the inner absorption layer and the outer absorption layer completely overlap in the radial direction, the cylinder body can minimize the neutron absorption effect and maximize the neutron reflection effect. At this time, the core reactivity is maximum. If uniform absorption effect is to be achieved at this time, all cylinder bodies can be synchronously rotated by an angle at a certain time interval to achieve uniform radial neutron absorption effect from a time average. By making each absorption layer alternately occupy an angle range of 0° to 360°, that is, the absorption layer is fully unfolded to cover the core, the core neutron absorption effect can be maximized, the neutron reflection effect can be minimized, the core reactivity can be minimized, and uniform absorption of core neutrons can be achieved.

[0025] The difference in core reactivity when the cylinders are completely overlapped and completely deployed is the range of the controllable reactivity of the cylinders. In actual use, the cylinders can be deployed between completely overlapped and completely deployed, that is, the controlled reactivity is between the maximum and minimum values. Specifically, the total amount of absorption layers in each cylinder is kept unchanged, and the absorption layers are subdivided into more parts by increasing the number of cylinder layers, such as from Figure 1-2 The third level is upgraded to Figure 3-4 The six layers can make the area facing the core smaller when the absorption layers in each cylinder are fully overlapped, thereby further reducing the neutron absorption and increasing the difference in the amount of neutron absorption from full expansion to full overlap, thereby expanding the control range of reactivity, thereby achieving the purpose of improving the controllable reactivity range of the cylinder without increasing the total mass volume of the absorption layer and maintaining the neutron economy (utilization rate). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure in which the absorption layers of the three-layer cylinder of the present invention are completely overlapped;

[0027] Figure 2 It is a schematic diagram of the structure in which the absorption layers of the three-layer cylinder of the present invention are completely staggered;

[0028] Figure 3 It is a schematic diagram of the structure in which the absorption layers of the six-layer cylinder of the present invention are completely overlapped;

[0029] Figure 4 It is a schematic diagram of the structure in which the absorption layers of the six-layer cylinder of the present invention are completely staggered;

[0030] Figure 5 It is a schematic diagram of the cross-sectional structure of the core of the present invention divided along the axial direction;

[0031] Figure 6It is a schematic diagram of different axial power distribution of the reactor of the present invention;

[0032] Figure 7 It is a comparative schematic diagram of the reactivity control range under the three-layer and six-layer cylinders of the present invention;

[0033] Figure 8 It is a schematic diagram of the axial structure of the cylinder of the present invention;

[0034] Fig. 9 It is a schematic diagram of the longitudinal cross-sectional structure of the cylinder of the present invention;

[0035] Fig.10 It is a schematic diagram of the top view of the cylinder of the present invention;

[0036] Fig.11 It is a structural schematic diagram of the connection between the cylinder and the transmission gear of the present invention;

[0037] Fig.12 It is a structural schematic diagram of the coil spring device of the present invention;

[0038] Fig.13 It is a schematic diagram of the structure of the three-layer cylinder and the transmission gear connected to each other in the present invention;

[0039] Fig.14 It is a structural schematic diagram of the connection between the cylinder and the fixed gear with missing teeth of the present invention;

[0040] Fig.15 It is a schematic structural diagram of the transmission rack of the present invention being connected to a fixed gear with missing teeth.

[0041] Description of reference numerals:

[0042] 1. Core, 2. First fixed reflective layer, 3. Cylinder, 31. Absorbing layer, 32. Annular groove, 33. Ball, 41. Fixed gear, 42. Transmission gear, 421. Rotating main shaft, 43. Transmission rack, 431. Sliding rod, 432. Linear spring, 451. Coil spring box, 452. Coil spring box inner shaft, 453. Coil spring, 46. Electric clamp, 47. Friction clutch mechanism, 5. Second fixed reflective layer, 6. Rotatable reflective layer. DETAILED DESCRIPTION

[0043] The following is combined with Figure 1 to Figure 15 , the specific implementation of the present invention is described in detail, but it should be understood that the protection scope of the present invention is not limited by the specific implementation. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] The nuclear reactor reactivity control tube and control method provided by the present invention include a first fixed reflection layer 2 and a plurality of cylinders 3 arranged on the periphery of a core 1, the core 1 having a longitudinal central axis, each cylinder 3 being coaxially sleeved between the core 1 and the first fixed reflection layer 2 from the inside to the outside with the longitudinal central axis as the center, and the gap between the innermost cylinder 3 and the core 1 being filled with a second fixed reflection layer 5, each cylinder 3 being connected to a rotary drive to drive each cylinder 3 to rotate around the longitudinal central axis through the rotary drive, and each cylinder 3 being evenly spaced along its own circumference and having the same number of The absorption layer 31, each absorption layer 31 on different cylinders 3 can overlap along the radial direction of the cylinder 3, and when the positions of each absorption layer 31 are misplaced, they can at least jointly occupy an angle range of 360° centered on the longitudinal central axis. By adopting the above technical scheme, each cylinder 3 can be rotated by a rotary drive, so that each absorption layer 31 on each cylinder 3 can overlap or misplace along the radial direction of the cylinder 3, so as to change the angle range jointly occupied by each absorption layer 31 on each cylinder 3 centered on the longitudinal central axis, thereby changing the size of the exposed surface area of ​​the core 1, thereby controlling the reactivity of the core 1.

[0045] Specifically, according to the reactivity adjustment range required by the core 1, the number of specific cylinders 3 is selected under the premise of keeping the mass volume of the absorption layer unchanged. In this way, the absorption layer 31 is evenly spaced on each layer of the cylinder 3, so that when fully unfolded, the core can be completely covered at 360°, and when completely overlapped along the radial direction of the cylinder 3, the core can be covered close to 0°. Compared with the shielding of one layer by another, the present invention highlights the effect of extreme folding, that is, the area of ​​the absorption layer 31 facing the core 1 is continuously reduced by overlapping more layers, and the neutron absorption is reduced, so as to achieve the purpose of improving the controllable reactivity range of the cylinder without increasing the total mass volume of the absorption layer 31 and maintaining the economic utilization rate of neutrons;

[0046] More specifically, when the three layers of absorption layers 31 completely overlap in the radial direction, 2 / 3 of the surface area of ​​the core 1 is exposed. If the number of layers of the cylinder 3 is increased, and the absorption layers 31 and the reflective materials are evenly distributed in each layer to achieve the functions of complete overlap and complete coverage, more core 1 area can be exposed. For example, 6 layers can expose 5 / 6 of the core 1 area, and 8 layers can expose 7 / 8. In this way, the reactivity of the core can be adjusted within a larger range, because the exposed core 1 area in the present invention is larger and can be adjusted as needed, that is, the range of reactivity can be increased or decreased by increasing or decreasing the number of layers. Under the same loading of the absorption layer 31 and the same thickness of the cylinder 3 and axial length, the range of controllable reactivity is greatly expanded, from the absorption layer being completely staggered and completely covering the core 1, to the absorption layer being completely overlapped and only 1 / 3, 1 / 30, 1 / 60... of the area covering the core 1, which can ultimately effectively improve the economy of the reactor. Specifically, it can be compared Figure 4 2 / 3 of the area is exposed Figure 7 5 / 6 of the area is exposed.

[0047] In one embodiment of the present invention, the sum of the angle ranges of the absorption layer 31 on any cylinder 3 centered on the longitudinal central axis is 360° / N, and the number of cylinders 3 may be equal to N. Figure 1 and Figure 2 As shown, the purpose of the present invention can be achieved. However, as the number of cylinders 3 increases, the outermost layer becomes farther and farther away from the innermost layer, which will cause the absorption layers 31 of the two layers to be non-adjacent and produce larger and larger gaps, resulting in leakage. Therefore, it is more preferred that the number of cylinders 3 is greater than N in order to effectively suppress the effect of gap leakage. Figure 4 As shown, outside the original last layer, another layer is added, and the absorbent material in this layer is completely offset and adjacent to the second-to-last layer, but completely overlaps with the innermost first layer. In this way, if the notch effect is larger, another layer can be added on the outside, which is still completely offset and adjacent to the second-to-last layer, but completely overlaps with the innermost second layer, so as to effectively suppress the notch effect, and so on, until the notch effect can be ignored and the notch effect is offset. The added layers, whose absorbent layers 31 correspond to the existing internal absorbent layers 31 respectively, will still shrink to the effect when no layers are added when they are rotated and shrunk to completely overlap, that is, the exposed area remains consistent, thereby ensuring the range of controlled reactivity.

[0048] As a preferred solution, the innermost cylinder 3 is in close contact with the core 1, and adjacent cylinders 3 are in close contact with each other, so that there is enough space outside the core 1 to arrange more reflective materials and shielding materials to prevent neutrons from leaking into the environment.

[0049] As a preferred solution, an annular groove 32 is coaxially provided on the inner wall of the cylinder 3, and balls 33 are provided in an annular array on the outer wall of the cylinder 3. The position of the balls 33 on the inner cylinder 3 corresponds to the position of the annular groove 32 on the outer adjacent cylinder 3, so that the balls 33 roll in the corresponding annular groove 32. In this way, when the adjacent cylinders 3 rotate relative to each other, the resistance to the rotation of the cylinder 3 can be reduced.

[0050] Since the existing reactivity control means can only achieve uniform control of axial reactivity, such as a control drum, or a one-way introduction of axial reactivity control capability, such as a control rod partially inserted in the axial direction, it is impossible to achieve segmented precise control of axial reactivity. Therefore, as a preferred solution, the core 1 is divided into multiple sections along the longitudinal center axis, and multiple cylinders 3 are coaxially sleeved from the inside to the outside between each section of the core 1 and the first fixed reflector 2, and each cylinder 3 is connected to a rotary driver respectively;

[0051] Specifically, the core 1 is divided into a first section, a second section and a third section along the longitudinal center axis, a three-layer cylinder 3 and a three-layer rotatable reflective layer 6 are sleeved between the first section and the first fixed reflective layer 2, another three-layer cylinder 3 is sleeved between the second section and the third section and the first fixed reflective layer 2, and the three-layer cylinder 3 sleeved outside the second section is fixedly connected with the three-layer rotatable reflective layer 6 sleeved outside the first section in a one-to-one correspondence, and the rotary drive comprises a first rotary drive, a second rotary drive and a third rotary drive, the first rotary drive is used to drive the three-layer cylinder 3 sleeved outside the first section to rotate around the longitudinal center axis, the second rotary drive is used to drive the three-layer rotatable reflective layer 6 sleeved outside the first section to rotate around the longitudinal center axis, and the third rotary drive is used to drive the three-layer cylinder 3 sleeved outside the third section to rotate;

[0052] Specifically, the core 1 may be divided into M sections greater than three sections, such as four sections, five sections, etc., along the longitudinal center axis, so as to achieve more precise axial layered control. A rotatable reflective layer 6 connected to each cylinder 3 located in the second section to the M-1 section in a one-to-one correspondence is provided in the first section or the M-th section. In this way, the corresponding cylinders 3 in the second section to the M-1 section can be driven to rotate by rotating the rotatable reflective layer 6 in the first section or the M-th section.

[0053] like Figure 6 The different axial power distribution of the reactor reflects the different axial strength distribution of the fission reaction and the axial distribution of the neutron flux. Since the axial power peak / neutron flux distribution in some core 1 designs will move significantly during operation, the above-mentioned technical scheme can be used to configure the cylinders 3 located in different sections to be expanded or overlapped according to the different axial neutron flux distributions through axial segmented control, thereby realizing segmented control of the reactor reactivity in the axial direction and providing different neutron absorption capabilities along the axial direction, thereby achieving precise reactivity control and improving neutron economy while ensuring the controllability of the reactor.

[0054] As a preferred embodiment, the rotary drive corresponds to the cylinder 3 one by one, and each rotary drive includes a fixed gear 41, a transmission gear 42, a driving part, a clutch device and an elastic reset member. The driving part is a motor (not shown in the drawings). The fixed gear 41 is coaxially fixedly connected to one end of the corresponding cylinder 3. When the core 1 is segmented in sequence along the longitudinal center axis, the fixed gear 41 can be connected to one end of the corresponding rotatable reflective layer 6. The transmission gear 42 is meshed with the fixed gear 41, and the motor is electrically connected to the power supply. The motor is fixedly arranged on the main structure of the test bench (not shown in the drawings). The transmission gear 42 is coaxially fixed. The clutch device is a friction clutch mechanism 47, the input end of the friction clutch mechanism 47 is connected to the output shaft of the motor, and the output end is connected to the top of the rotating main shaft 421. The elastic reset member is a coil spring device, and the bottom end of the rotating main shaft 421 is connected to a coil spring mechanism. The coil spring mechanism includes a coil spring box 451, an inner shaft 452 of the coil spring box and a coil spring 453. The coil spring box 451 is fixedly arranged on the main structure of the test bench, and the inner shaft 452 of the coil spring box is rotatably connected to the center of the coil spring box 451. The inner shaft 452 of the coil spring box is also fixedly connected to the rotating main shaft 421 through a pin key. The coil spring 453 The spring 453 is sleeved outside the inner shaft 452 of the coil spring box, and its two ends are respectively connected to the inner shaft 452 of the coil spring box and the inner wall of the coil spring box 451 to prevent the transmission gear 42 or the transmission rack 43 from leaving the initial position. With the above technical solution, when the friction clutch mechanism 47 is energized and tightened, the power from its input end can be transmitted from the output end to the rotating main shaft 421, and then the transmission gear 42 is driven by the motor, and the fixed gear 41 and the corresponding cylinder 3 are driven to rotate, and the coil spring 453 is deformed. When the friction clutch mechanism 47 is powered off and released, the power at its input end can no longer be transmitted to the rotating main shaft 421, and the coil spring 453 is deformed. 3 can restore the deformation and drive the cylinder 3 to rotate in the opposite direction until it returns to the initial position. Specifically, the initial position is a state where all cylinders 3 are unfolded in sequence and the absorption layers 31 do not overlap, that is, a fully unfolded state. At this time, the cylinder 3 has the strongest ability to absorb neutrons. Furthermore, when power is cut off or due to an accidental power outage, the present invention can restore the cylinder 3 to the initial position (that is, the fully unfolded state) by relying on the inherent characteristics of the components in the rotating driver (that is, the elastic reset member), thereby achieving the maximum absorption capacity of the core 1 neutrons to ensure the safety of the core 1.

[0055] In another embodiment, the transmission gear 42 can be replaced by a transmission rack 43, the transmission rack 43 is meshed with the corresponding fixed gear 41, the transmission rack 43 is slidably connected to the main structure of the test bench, one end of the transmission rack 43 is fixedly connected to a slide bar 431 along the longitudinal direction, the elastic reset member is a linear spring 432, the linear spring 432 is sleeved on the slide bar 431, the two ends of the linear spring 432 are respectively connected to the slide bar 431 and the main structure of the test bench, the driving part is also a motor (not shown in the drawings), and a screw slider mechanism (not shown in the drawings) is connected to the output shaft of the motor to drive the slider of the screw slider mechanism to move through the rotation of the motor output shaft. The guide rod of the structure is parallel to the sliding direction of the transmission rack 43 on the main structure of the test bench. The clutch device is an electric clamp 46. The fixed part of the electric clamp 46 is fixedly connected to the slider. The clamping part of the electric clamp 46 is clamped on the slide bar 431. When the electric clamp 46 is powered on, the clamping part of the electric clamp 46 is clamped on the slide bar 431. The movement of the slider can drive the slide bar 431 and the transmission rack 43 to translate, so that the linear spring 432 is deformed and drives the fixed gear 41 to rotate. When the electric clamp 46 is powered off, the clamping part of the electric clamp 46 releases the slide bar 431, the linear spring 432 recovers its deformation, and drives the cylinder 3 to rotate in the opposite direction until it returns to the initial position.

[0056] Specifically, the position of the fixed gear 41 located relatively inside is higher than that of the fixed gear 41 located outside, so that the transmission gear 42 or the transmission rack 43 is meshed with the fixed gear 41 .

[0057] In order to achieve the meshing of each fixed gear 41 with the corresponding transmission rack 43 or transmission gear 42, if a complete gear is used, it is necessary to arrange each fixed gear 41 in a stepped manner, with the fixed gear 41 located in the inner layer being higher and the fixed gear 41 located in the outer layer being lower. However, this will increase the axial length of the present invention. For this reason, as a preferred embodiment, the present invention arranges the fixed gears 41 to be fan-shaped gears, and the fan-shaped gears on each cylinder 3 are staggered in the circumferential direction. In this way, the fixed gears 41 can be located at the same height, and the transmission gear 42 or transmission rack 43 can be meshed with the fixed gear 41, thereby reducing the axial length of the present invention.

[0058] Any of the above-mentioned control methods for a nuclear reactor reactivity control cylinder is that when the angle range jointly occupied by the positions of the absorption layers 31 on the cylinder 3 is less than 360°, the cylinders 3 are driven to rotate synchronously in the same direction by a rotary driver;

[0059] By adopting the above technical scheme, by rotating all the cylinders 3 at the same time, it can be ensured that the absorption or reflection effect on the fuel consumption in all radial directions in the reactor core 1 during long-term operation is uniform. By making the inner absorption layer 31 and the outer absorption layer 31 completely overlap in the radial direction, the cylinder 3 can minimize the neutron absorption effect and maximize the neutron reflection effect. At this time, the reactivity of the core 1 is the largest. If a uniform absorption effect is to be achieved at this time, all the cylinders 3 can be synchronously rotated by an angle within a certain time interval to achieve uniform radial neutron absorption effect from a time average perspective.

[0060] In the description of the present invention, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0061] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect" and "connect" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nuclear reactor reactivity control tube, comprising a first fixed reflector layer (2) arranged on the periphery of a core (1), wherein the core (1) has a longitudinal central axis, characterized in that: Also includes: A plurality of cylinders (3) are coaxially sleeved in sequence from the inside to the outside, with the longitudinal central axis as the center, between the core (3) and the first fixed reflective layer (2); each cylinder (3) is provided with an absorption layer (31) evenly spaced along its own circumference, and the number of the absorption layers (31) on each cylinder (3) is the same; the absorption layers (31) on different cylinders (3) can overlap along the radial direction of the cylinder (3); and when the positions of the absorption layers (31) are all misaligned, they can at least jointly occupy an angle range of 360° centered on the longitudinal central axis; The rotary drive is connected to each of the cylinders (3) so as to drive each of the cylinders (3) to rotate around the longitudinal center axis through the rotary drive.

2. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: The sum of the angle ranges occupied by the absorption layer (31) on any cylinder (3) centered on the longitudinal central axis is 360° / N, and the number of the cylinders (3) is greater than N.

3. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: The innermost cylinder (3) is in close contact with the core (1), and adjacent cylinders (3) are in close contact with each other.

4. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: An annular groove (32) is provided on the inner wall of the cylinder (3), and the annular groove (32) is arranged with the longitudinal central axis as the center. Balls (33) are provided in an annular array on the outer wall of the cylinder (3), and the position of the balls (33) on the cylinder (3) located on the inner side corresponds to the position of the annular groove (32) on the cylinder (3) adjacent to the outer side, so that the balls (33) roll in the corresponding annular groove (32).

5. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: The core (1) is divided into a plurality of sections along the longitudinal center axis, and a plurality of cylinders (3) are coaxially sleeved in sequence from the inside to the outside between each section of the core (1) and the first fixed reflective layer (2), and each cylinder (3) is respectively connected to a rotating driver.

6. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: The rotary drivers correspond to the barrels (3) one by one, and each rotary driver comprises: A fixed gear (41) is coaxially fixedly connected to one end of the corresponding cylinder (3); A transmission gear (42) meshing with the fixed gear (41); A driving part connected to the transmission gear (42) via a clutch device, the clutch device being used to connect or disconnect the driving part from the transmission gear (42), and when the driving part is connected to the transmission gear (42), the driving part is used to drive the transmission gear (42) to rotate; An elastic reset member is connected to the transmission gear (42) to prevent the transmission gear (42) from leaving the initial position.

7. The nuclear reactor reactivity control cylinder according to claim 1, characterized in that: The rotary drivers correspond to the barrels (3) one by one, and each rotary driver comprises: A fixed gear (41) is coaxially fixedly connected to one end of the corresponding cylinder (3); A transmission rack (43) meshing with the fixed gear (41); A driving part connected to the transmission rack (43) via a clutch device, the clutch device being used to connect or disconnect the driving part from the transmission rack (43), and when the driving part is connected to the transmission rack (43), the driving part is used to drive the transmission rack (43) to translate; An elastic reset member is connected to the transmission rack (43) to prevent the transmission rack (43) from leaving an initial position.

8. The nuclear reactor reactivity control cylinder according to claim 6 or 7, characterized in that: The fixed gears (41) are all sector gears, and the sector gears on each of the cylinders (3) are staggered in the circumferential direction.

9. The control method of a nuclear reactor reactivity control cylinder according to any one of claims 1 to 8, characterized in that: When the angle range jointly occupied by the positions of the absorption layers (31) on the cylinder (3) is less than 360°, the cylinders (3) are driven to rotate synchronously in the same direction by a rotary drive.

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