Helium-3 based large measurement cavity neutron multiplicity measurement device and measurement method

Abstract

A kind of helium-3-based large measurement cavity neutron multiplicity measuring device, including detection system, horizontal motion control system and vertical motion control system, detection system includes measurement cavity and detection component, detection component is arranged at the inboard of measurement cavity, detection component includes neutron multiplicity detector and detector shield, neutron multiplicity detector is helium-3 counter tube, recess is provided on detector shield, recess is used to place helium-3 counter tube;Electronic box is connected with helium-3 counter tube and power supply module by cable;The present application is by reasonably setting helium-3 counter tube structure and measurement cavity structure, under the premise of meeting the demand of detection efficiency and large volume sample measurement, effectively control the total amount of helium-3 counter tube, reduce economic cost, improve economic benefit, to solve the problems, such as the low detection efficiency of existing multiplicity measurement equipment, unable to meet the large volume sample measurement, the cost is significantly improved due to the large use demand of helium-3 counter tube etc.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation detection technology, and in particular to a large measurement cavity neutron multiplicity measurement device and method based on helium-3. Background Technology

[0002] With the development of the nuclear industry, the amount of uranium, plutonium, and other materials worldwide is increasing, making nuclear proliferation a widespread concern in the international community. Since uranium and plutonium can produce fission neutrons, non-destructive analysis using neutron detection technology combined with isotopic abundance is the most common method in nuclear safeguards. In my country, the detection of uranium and plutonium materials in nuclear facilities, as well as the classification and treatment of large amounts of radioactive solid waste generated during long-term operation and decommissioning, has gradually become a challenging task. In the development of nuclear radiation detection technology, neutron measurement technology has become an important non-destructive analytical technique in the field of nuclear radiation detection, and it is of great significance in nuclear safeguards, especially in nuclear material accounting.

[0003] Neutrons possess strong penetrating power and are difficult to shield, making them the only rapid and feasible method that simultaneously meets detection requirements for analyzing medium- and high-density, large-volume samples. They also show broad application prospects in the classification and detection of low- and intermediate-level solid radioactive waste. In these related fields, this technology plays a positive role in the accurate quantitative analysis of U / Pu materials, including routine sample analysis, warehouse inventory, and closed-loop balance calculations for U / Pu production lines.

[0004] Neutron multiplicity measurement (NMDA) is a rapid, non-destructive analysis technique that measures the multiplicity distribution of fission neutrons in nuclear materials to achieve accurate quantitative analysis. No standard calibration is required during the measurement process, thus avoiding the potential influence of standard samples on the measurement results. Because fission neutrons are temporally correlated, the number of neutrons released in a single fission event follows a certain probability distribution, i.e., a multiplicity distribution. This method can distinguish between fission neutrons and non-fission neutrons, minimizing interference from non-fission neutrons and the influence of the matrix material on the measurement.

[0005] Neutron multiplicity counting is a state-of-the-art non-destructive analysis method for nuclear materials. Although the number of neutrons produced during nuclear fission is random, it follows statistical laws and conforms to a certain probability distribution; this probability distribution is called the neutron multiplicity distribution. By studying the neutron multiplicity distribution information emitted during nuclear fission, the mass properties of nuclear materials can be accurately obtained. A helium-3-based neutron multiplicity measurement device uses helium-3 as the neutron detector. The cavity of the device is typically filled with polyethylene. Fission neutrons are slowed down by the polyethylene to become thermal neutrons, which are then detected by the helium-3 tube, forming a pulse sequence. The total neutron count rate and multiplicity count rate are obtained through coincidence analysis. Substituting these values ​​into the neutron multiplicity measurement equation yields the effective mass of the sample. The neutron multiplicity measurement is expressed by the following equation:

[0006] Singles=Fεν sf,1 (1+α)M (1)

[0007]

[0008]

[0009] In the formula, Singles, Doubles, and Triples represent the single, double, and triple count rates, respectively, and ν sf,1 ν sf,2 and ν sf,3 These are the first, second, and third factorial moments of the spontaneous fission emission neutron number distribution, ν i1 ν i2 、 and ν i3 These are the first, second, and third factorial moments of the induced fission emission neutron number distribution, respectively; ε is the detector's neutron detection efficiency; and f... d f t These are the detector's double and triple coincidence gate factors, M is the multiplication coefficient, α is the ratio of the number of neutrons to the number of spontaneously fissioning neutrons, and F is the average reaction rate when spontaneously fissioning neutrons occur.

[0010] To ensure that neutron multiplexing measurement technology can meet the practical needs of different measurement objects, the neutron multiplexing measurement device is usually designed according to the volume of the object to be measured and the detection efficiency requirements. The helium-3 counter tube is the core component of the neutron multiplexing measurement device. From the principle of nuclear radiation detection, as long as a sufficient number of helium-3 counter tubes are installed in the device and their length is long enough, the measurement requirements for objects of different volumes can be met. However, due to the scarcity and high price of helium-3 gas, it is impossible to use helium-3 counter tubes without considering costs.

[0011] Therefore, when dealing with large-volume measurement objects, existing multivariable measurement equipment often has the following problems:

[0012] 1. The measurement chamber sizes of existing multiplex measurement devices are φ170mm×300mm (NMC-01), φ229mm×206mm (AWCC), and φ165mm×305mm (5RMC), respectively. However, the measurement chambers of these devices do not reach φ400mm×400mm. Therefore, the measurement chambers of existing multiplex measurement devices cannot meet the measurement requirements of large-volume samples.

[0013] 2. If the measurement cavity of the existing multiplex measurement device is directly enlarged to φ400mm×400mm, while maintaining the basic parameters of the helium-3 counter tube in the existing multiplex measurement device, and the spacing of the helium-3 counter tube is increased proportionally according to the enlarged measurement cavity, the detection efficiency will be less than 20% in all cases.

[0014] 3. The existing multiplexing measurement equipment uses a total of 6776 cm of helium-3 counter tubes with a measuring cavity size of φ170mm×300mm (NMC-01), 2940 cm of helium-3 counter tubes with a measuring cavity size of φ229mm×206mm (AWCC), and 50820 cm of helium-3 counter tubes with a measuring cavity size of φ165mm×305mm (5RMC). The usage is extremely large, which seriously wastes economic costs and has poor economic benefits. Summary of the Invention

[0015] The purpose of this invention is to address the shortcomings of existing technologies by providing a large-cavity neutron multiplicity measurement device and method based on helium-3. By rationally designing the helium-3 counter tube structure and the measurement cavity structure, the total number of helium-3 counter tubes used is effectively controlled while meeting the requirements for detection efficiency and large-volume sample measurement, thus reducing economic costs and improving economic efficiency. This solves the problems of low detection efficiency, inability to meet the requirements for large-volume sample measurement, and significantly increased costs due to the large number of helium-3 counter tubes required in existing multiplicity measurement equipment. To achieve the above objectives, this invention is implemented through the following technical solution:

[0016] A large-cavity neutron multiplicity measurement device based on helium-3 includes a frame, a detection system, a horizontal motion control system, a vertical motion control system, and a power control system. The frame includes an upper top plate and a lower bottom plate, with four parallel frame side supports positioned between them. The power control system includes a power supply module and a motor control box, both mounted on the frame side supports. The detection system includes a measurement cavity and a detection assembly. The measurement cavity is mounted on the upper side of the frame via upper and lower clamping plates, and the detection assembly is positioned inside the measurement cavity. The system includes a neutron multiplex detector and a detector shield. The neutron multiplex detector is a helium-3 counter tube. The detector shield has a groove for placing the helium-3 counter tube. An upper cover plate that fits into the measurement cavity is also provided on the upper side of the measurement cavity. An electronics box is also provided between the measurement cavity and the upper cover plate. The electronics box is connected to the helium-3 counter tube and a power supply module via cables. The horizontal motion control system includes a horizontal motion support rail, which is laid on the lower base plate and extends outward beyond the frame side frame using a distance adjustment bracket. A sliding support plate is connected via... The guide rail support unit is slidably connected to the horizontal motion support guide rail. A detection base that fits into the measuring cavity is provided on the upper side of the sliding support plate, and a movable positioning clip is provided on the detection base. A horizontal lead screw bearing seat is also provided on the lower side of the sliding support plate, and a horizontal handwheel is connected to the horizontal lead screw bearing seat via a horizontal motion lead screw. A horizontal limiting block is provided on the side of the sliding support plate away from the horizontal motion support guide rail, and a vertical limiting block is provided between the upper clamping plate and the upper top plate. The vertical motion control system includes a vertical motion motor, two sets of vertical motion lead screws, and two sets of vertical guide shafts. The motion screw passes through the upper and lower clamping plates via a vertical screw nut and is connected to the upper top plate and lower bottom plate via a vertical screw bearing seat. The vertical guide shaft passes through the upper and lower clamping plates via a vertical linear bearing and is fixedly connected to the upper top plate and lower bottom plate via a vertical limiting sleeve flange. The vertical motion motor is connected to the vertical power gear converter via a coupling. The vertical power gear converter is connected to the vertical screw bearing seat via two sets of vertical transmission rollers. The vertical power gear converter is also equipped with a vertical handwheel. The vertical motion motor is connected to the power supply module via a motor control box.

[0017] Preferably, the number of helium-3 counting tubes is greater than or equal to 46, and the length is greater than or equal to 48 cm.

[0018] Preferably, the measuring cavity has a cylindrical structure, and the size of the measuring cavity is greater than or equal to Φ400mm×400mm.

[0019] Preferably, the number and length of the grooves are matched with the number and length of the helium-3 counting tubes.

[0020] Preferably, the helium-3 counter tubes are arranged in a double-layer layout with equal intervals. When the total number of helium-3 counter tubes n is even, the number of helium-3 counter tubes in the inner layer is n / 2, and the number of helium-3 counter tubes in the outer layer is also n / 2. When the total number of helium-3 counter tubes n is odd, the number of helium-3 counter tubes in the inner layer is (n-1) / 2, and the number of helium-3 counter tubes in the outer layer is (n+1) / 2.

[0021] Preferably, the top plate, bottom plate, and frame side frames are all made of stainless steel.

[0022] Preferably, a polyethylene partition is provided on the inner side of the measuring cavity, and a graphite partition is provided on the upper cover and the detection base.

[0023] Preferably, the bottom of the frame is also provided with multiple sets of movable casters.

[0024] Preferably, the upper side of the top plate is also provided with a plurality of eye bolts.

[0025] A measurement method based on a large measurement cavity neutron multiplicity measurement device using helium-3 includes the following steps:

[0026] Step S1: Connect the neutron multiplicity measurement device in the large measurement cavity to the background detection and control system;

[0027] Step S2: The reverse horizontal handwheel drives the horizontal motion screw to rotate in reverse, thereby driving the detection base to slide outward on the horizontal motion support rail to the sample loading position;

[0028] Step S3: Place the sample to be tested and use the movable positioning card to fix the sample to be tested on the base;

[0029] Step S4: Rotate the horizontal handwheel to drive the horizontal movement screw to rotate forward, and send the detection base to the horizontal 0 position of the sample detection. At this time, the detection base is facing the lower side of the measurement cavity.

[0030] Step S5: Control the vertical motion motor to rotate forward and transmit power to the vertical motion screw. The vertical motion screw drives the measuring cavity, upper clamping plate and lower clamping plate to the vertical 0 position of sample detection. The vertical 0 position can be finely adjusted by the vertical handwheel to ensure that the detection base and the measuring cavity fit perfectly.

[0031] Step S6: Turn on the electronics box, set the initial measurement state, and clear the count state.

[0032] Step S7: Start the measurement program of the electronics box;

[0033] Step S8: Record the measurement data and turn off the electronics box;

[0034] Step S9: Control the vertical motion motor to reverse and raise the measuring cavity, upper clamping plate and lower clamping plate to the initial position;

[0035] Step S10: Reverse the horizontal handwheel to return the detection base to the sample loading position, remove the sample, and end the measurement.

[0036] The beneficial effects of this invention are:

[0037] 1. The measuring cavity size of the device of the present invention reaches φ400mm×400mm, which can effectively meet the actual needs of existing measuring objects, meet the measurement requirements of large volume samples, and at the same time improve the detection efficiency to 30% or more.

[0038] 2. This invention can meet the requirements of measurement cavity size and detection efficiency while ensuring that the total number of helium-3 counter tubes used is less than or equal to 2500 cm³, which greatly saves the consumption of helium-3 counter tubes, significantly reduces the cost of helium-3 counter tubes, and improves economic efficiency.

[0039] 3. When measuring large-sized samples, this invention makes full use of structures such as motors, lead screws, and drive fixing plates, allowing the object to be placed in a visible position outside the frame support, with the base and measuring cavity at the same center, thus avoiding the problem of eccentric placement of the object leading to a decrease in detection efficiency. Attached Figure Description

[0040] Figure 1 This is a first-view three-dimensional structural diagram of the measuring device of the present invention;

[0041] Figure 2 This is a three-dimensional structural schematic diagram of the measuring device of the present invention from another perspective;

[0042] Figure 3 This is a three-dimensional structural schematic diagram of the measuring device of the present invention from another perspective;

[0043] Figure 4 This is a front view of the measuring device of the present invention;

[0044] Figure 5 This is a cross-sectional view along direction AA of the front view of the measuring device of the present invention;

[0045] Figure 6 For the present invention Figure 5 Cross-sectional view along the BB direction;

[0046] Figure 7 This is a structural diagram showing the arrangement of the helium-3 counting tubes in the measuring device of the present invention;

[0047] Figure 8 This is a flowchart illustrating the measurement method of the present invention.

[0048] In the diagram: 1. Top plate; 2. Bottom plate; 3. Side frame; 4. Power supply module; 5. Motor control box; 6. Vertical motion motor; 7. Electronics box; 8. Fuma wheel; 9. Eye bolt; 10. Measuring chamber; 11. Upper clamping plate; 12. Lower clamping plate; 13. Helium-3 counter tube; 14. Detector shield; 15. Top cover plate; 16. Horizontal motion support rail; 17. Distance adjustment bracket; 18. Sliding support plate; 19. Rail support unit; 20. 21. Detection base; 22. Movable positioning clip; 23. Horizontal lead screw bearing seat; 24. Horizontal handwheel; 25. Horizontal movement lead screw; 26. Horizontal limit block; 27. Vertical limit block; 28. Vertical movement lead screw; 29. ​​Vertical guide shaft; 30. Vertical lead screw nut; 31. Vertical lead screw bearing seat; 32. Vertical linear bearing; 33. Vertical limit sleeve flange; 34. Coupling; 35. Vertical power gear converter; 36. Vertical transmission roller; 37. Vertical handwheel. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The following describes embodiments of the invention based on its overall structure.

[0051] The present invention will now be further described with reference to the accompanying drawings and specific embodiments:

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer and more explicit, the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] Example 1:

[0054] like Figures 1 to 7 As shown, a large-cavity neutron multiplicity measurement device based on helium-3 includes a frame, a detection system, a horizontal motion control system, a vertical motion control system, and a power control system. The frame includes an upper top plate 1 and a lower bottom plate 2, with four parallel frame side frames 3 positioned between the upper top plate 1 and the lower bottom plate 2. The power control system includes a power supply module 4 and a motor control box 5, both mounted on the frame side frames 3 to provide power to the vertical motion motor 6 and the electronics box 7. Multiple sets of movable casters 8 are provided at the bottom of the frame for convenient and timely transfer of the device. Multiple eye bolts 9 are also provided on the upper side of the upper top plate 1 for hoisting and moving the device.

[0055] The detection system includes a measuring cavity 10 and a detection assembly. The measuring cavity 10 used in this invention is a cylindrical structure with dimensions greater than or equal to Φ400mm×400mm. The measuring cavity 10 is mounted on the upper side of the frame via an upper clamping plate 11 and a lower clamping plate 12, and the detection assembly is mounted inside the measuring cavity 10. The detection assembly includes a neutron multiplicity detector and a detector shield 14, wherein the neutron multiplicity detector is a helium-3 counter tube 13. Grooves are provided on the detector shield 14 so that the number and length of the grooves match the number and length of the helium-3 counter tubes 13. The helium-3 counter tubes 13 are placed through the grooves. The number of helium-3 counter tubes 13 needs to be greater than or equal to 46, and their length needs to be greater than or equal to 48cm. The measuring device of this invention uses 50 helium-3 counter tubes 13 with a length of 48cm. The upper side of the measuring cavity 10 is also provided with an upper cover plate 15 that fits the measuring cavity 10. An electronics box 7 is provided between the measuring cavity 10 and the upper cover plate 1. The electronics box 7 is then connected to the helium-3 counter tube 13 and the power supply module 4 via cables for measuring the number of neutrons in the sample.

[0056] To meet the size and detection efficiency requirements of the measuring cavity 10 while ensuring that the total number of helium-3 counter tubes 13 actually used is less than or equal to 2500 cm, thereby saving the consumption of helium-3 counter tubes 13 and reducing the cost of helium-3 counter tubes 13, the helium-3 counter tubes 13 of this invention adopt a double-layer layout with equal intervals. Specifically, when the total number n of helium-3 counter tubes 13 is even, the number of inner helium-3 counter tubes 13 is n / 2, and the number of outer helium-3 counter tubes 13 is also n / 2; when the total number n of helium-3 counter tubes 13 is odd, the number of inner helium-3 counter tubes 13 is set to (n-1) / 2, and the number of outer helium-3 counter tubes 13 is (n+1) / 2.

[0057] The horizontal motion control system includes a horizontal motion support rail 16, which is laid on the lower base plate 2 and extends outward beyond the frame side frame 3 using a distance adjustment bracket 17. This outward extension facilitates the loading of the object to be tested. A sliding support plate 18 is slidably connected to the horizontal motion support rail 16 via a guide rail support unit 19. A detection base 20, which fits into the measuring cavity 10, is located on the upper side of the sliding support plate 18. A movable positioning clip 21 is installed on the detection base 20 to fix the sample to be tested. The lower side of the sliding support plate 18... A horizontal lead screw bearing seat 22 is also provided. A horizontal handwheel 23 is connected to the horizontal lead screw bearing seat 22 via a horizontal movement lead screw 24 for moving the detection base 20. A horizontal limiting block 25 is provided on the side of the sliding support plate 18 away from the horizontal movement support guide rail 16. A vertical limiting block 26 is provided between the upper clamping plate 11 and the upper top plate 1. This can prevent the detection base 20 from deviating from the lower position of the measuring cavity 10, prevent it from failing to fit with the measuring cavity 10, and prevent the measuring cavity 10 from colliding with the upper clamping plate 11 or the electronic box 7 during the upward process, thus preventing malfunctions.

[0058] The vertical motion control system includes a vertical motion motor 6, two sets of vertical motion lead screws 27, and two sets of vertical guide shafts 28. The vertical motion lead screws 27 pass through the upper clamping plate 11 and the lower clamping plate 12 via vertical lead screw nuts 29, and are connected to the upper top plate 1 and the lower bottom plate 2 via vertical lead screw bearing seats 30. The vertical guide shafts 28 pass through the upper clamping plate 11 and the lower clamping plate 12 via vertical linear bearings 31, and are fixedly connected to the upper top plate 1 and the lower bottom plate 2 via vertical limiting sleeve flanges 32. The vertical motion lead screws 27 are used to lift and lower the measuring cavity 10, while the vertical guide shafts 28 are used to support the measuring cavity 10 and provide guidance in the vertical direction. The vertical motion motor 6 is connected to a vertical power gear converter via a coupling 33. The vertical power gear converter 34 is connected to the vertical lead screw bearing seat 30 through two sets of vertical transmission rollers 35. The power is transmitted to the vertical movement lead screw 27 by the forward and reverse rotation of the vertical motion motor 6, so as to realize the lifting function of the measuring cavity 10. The vertical power gear converter 34 is also equipped with a vertical handwheel 36. Since the vertical lifting of the measuring cavity 10 mainly relies on the motor to operate, the mechanical control is not completely precise. Therefore, the vertical handwheel 36 can be used for fine adjustment to make the measuring cavity 10 fit perfectly with the detection base 20 and prevent errors caused by gaps. The vertical motion motor 6 is connected to the power supply module 4 through the motor control box 5, and the motor control box 5 is used to control the vertical motion motor 6.

[0059] The frame of the present invention is preferably made of stainless steel, and a polyethylene partition is provided on the inner side of the measuring cavity 10. The upper cover plate 15 and the detection base 20 are also equipped with graphite partitions.

[0060] Example 2:

[0061] like Figure 8 As shown, a measurement method implemented by a large measurement cavity neutron multiplicity measurement device based on helium-3 includes the following steps:

[0062] Step S1: Connect the neutron multiplicity measurement device in the large measurement cavity to the background detection and control system;

[0063] Step S2: The horizontal handwheel 23 reverses and drives the horizontal motion screw 24 to rotate in reverse, thereby driving the detection base 20 to slide outward on the horizontal motion support rail 16 to the sample loading position.

[0064] Step S3: Place the sample to be tested and use the active positioning card 21 to fix the sample to be tested on the testing base 20;

[0065] Step S4: The forward-rotating horizontal handwheel 23 drives the horizontal motion screw 24 to rotate forward, sending the detection base 20 to the horizontal 0 position of the sample detection. At this time, the detection base 20 is facing the lower side of the measuring cavity 10.

[0066] Step S5: Control the vertical motion motor 6 to rotate forward and transmit power to the vertical motion screw 27. The vertical motion screw 27 drives the measuring cavity 10, the upper clamping plate 11 and the lower clamping plate 12 to descend to the vertical 0 position of the sample detection. The vertical 0 position can be finely adjusted by the vertical handwheel 36 to ensure that the detection base 20 and the measuring cavity 10 fit perfectly.

[0067] Step S6: Turn on the electronics box 7, set the initial measurement state, and clear the count state.

[0068] Step S7: Start the measurement program of the electronics box 7;

[0069] Step S8: Record the measurement data and turn off the electronics box 7;

[0070] Step S9: Control the vertical motion motor 6 to reverse and raise the measuring cavity 10, upper clamping plate 11 and lower clamping plate 12 to the initial position;

[0071] Step S10: Reverse the horizontal handwheel 23 to return the detection base 20 to the sample loading position, remove the sample, and end the measurement.

[0072] After establishing a communication connection between the device of the present invention and the background detection system, the detection base 20 is first slid to the sample loading position by rotating the horizontal handwheel 23 in the reverse direction. The sample is then fixed by the movable positioning card 21. The horizontal handwheel 23 is rotated in the forward direction to send the detection base 20 to the horizontal 0 position of the sample detection. At this time, the vertical motion motor 6 is controlled to rotate in the forward direction by the motor control box 5 to lower the measuring cavity 10 to the vertical 0 position of the sample detection. If the lowering position is slightly deviated, the vertical handwheel 36 is used for fine adjustment to ensure that the detection base 20 fits the measuring cavity 10. At this time, the electronic box 7 is opened, the initial measurement state is set and the count state is cleared, and then the measurement program of the electronic box 7 is started to measure and record data. Then the detection base 20 is slid out and the sample is removed.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention, and no reference numerals in the claims should be regarded as limiting the scope of the claims.

Claims

1. A large-cavity neutron multiplicity measurement device based on helium-3, comprising a frame, a detection system, a horizontal motion control system, a vertical motion control system, and a power control system, characterized in that, The frame includes an upper top plate and a lower bottom plate, and four parallel frame side frames are arranged between the upper top plate and the lower bottom plate. The power control system includes a power supply module and a motor control box, and both the power supply module and the motor control box are arranged on the frame side frames. The detection system includes a measurement cavity and a detection assembly. The measurement cavity is mounted on the upper side of the frame via upper and lower clamping plates. The detection assembly is located inside the measurement cavity and includes a neutron multiplicity detector and a detector shield. The neutron multiplicity detector is a helium-3 counter tube. The detector shield has a groove for placing the helium-3 counter tube. An upper cover plate that fits into the measurement cavity is also provided on the upper side of the measurement cavity. An electronics box is also provided between the measurement cavity and the upper cover plate. The electronics box is connected to the helium-3 counter tube and the power supply module via cables. The horizontal motion control system includes a horizontal motion support rail, which is laid on the lower base plate and extends outward beyond the frame side frame using a distance adjustment bracket. A sliding support plate is slidably connected to the horizontal motion support rail through a guide rail support unit. A detection base that fits into the measuring cavity is provided on the upper side of the sliding support plate, and a movable positioning card is provided on the detection base. A horizontal lead screw bearing seat is also provided on the lower side of the sliding support plate, and a horizontal handwheel is connected to the horizontal lead screw bearing seat through a horizontal motion lead screw. A horizontal limiting block is provided on the side of the sliding support plate away from the horizontal motion support rail, and a vertical limiting block is provided between the upper clamping plate and the upper top plate. The vertical motion control system includes a vertical motion motor, two sets of vertical motion lead screws, and two sets of vertical guide shafts. The vertical motion lead screws pass through the upper and lower clamping plates via vertical lead screw nuts and are connected to the upper top plate and lower bottom plate via vertical lead screw bearing seats. The vertical guide shafts pass through the upper and lower clamping plates via vertical linear bearings and are fixedly connected to the upper top plate and lower bottom plate via vertical limiting sleeve flanges. The vertical motion motor is connected to a vertical power gear converter via a coupling. The vertical power gear converter is powered by two sets of vertical transmission rollers connected to the vertical lead screw bearing seats. The vertical power gear converter also has a vertical handwheel. The vertical motion motor is connected to a power supply module via a motor control box. The helium-3 counter tubes are arranged in a double-layer layout with equal intervals. When the total number of helium-3 counter tubes n is even, the number of helium-3 counter tubes in the inner layer is n / 2, and the number of helium-3 counter tubes in the outer layer is also n / 2. When the total number of helium-3 counter tubes n is odd, the number of helium-3 counter tubes in the inner layer is (n-1) / 2, and the number of helium-3 counter tubes in the outer layer is (n+1) / 2.

2. The helium-3-based large-cavity neutron multiplicity measurement device according to claim 1, characterized in that, The number of helium-3 counting tubes is greater than or equal to 46, and the length is greater than or equal to 48 cm.

3. The large-cavity neutron multiplicity measurement device based on helium-3 according to claim 1, characterized in that, The measuring cavity has a cylindrical structure, and the size of the measuring cavity is greater than or equal to Φ400mm×400mm.

4. The large-cavity neutron multiplicity measurement device based on helium-3 according to claim 1, characterized in that, The number and length of the grooves are matched with the number and length of the helium-3 counter tubes.

5. The helium-3-based large-cavity neutron multiplicity measurement device according to claim 1, characterized in that, The top plate, bottom plate, and side frame are all made of stainless steel.

6. The large-cavity neutron multiplicity measurement device based on helium-3 according to claim 1, characterized in that, The inner side of the measuring cavity is provided with a polyethylene partition, and the upper cover and the detection base are both equipped with a graphite partition.

7. The large-cavity neutron multiplicity measurement device based on helium-3 according to claim 1, characterized in that, The bottom of the frame is also equipped with multiple sets of movable casters.

8. The large-cavity neutron multiplicity measurement device based on helium-3 according to claim 1, characterized in that, The upper side of the top plate is also equipped with multiple eye bolts.

9. A measurement method implemented using the large measurement cavity neutron multiplicity measurement device according to any one of claims 1-8, characterized in that, Includes the following steps: Step S1: Connect the neutron multiplicity measurement device in the large measurement cavity to the background detection and control system; Step S2: The reverse horizontal handwheel drives the horizontal motion screw to rotate in reverse, thereby driving the detection base to slide outward on the horizontal motion support rail to the sample loading position; Step S3: Place the sample to be tested and use the movable positioning card to fix the sample to be tested on the base; Step S4: Rotate the horizontal handwheel to drive the horizontal movement screw to rotate forward, and send the detection base to the horizontal 0 position of the sample detection. At this time, the detection base is facing the lower side of the measurement cavity. Step S5: Control the vertical motion motor to rotate forward and transmit power to the vertical motion screw. The vertical motion screw drives the measuring cavity, upper clamping plate and lower clamping plate to the vertical 0 position of sample detection. The vertical 0 position can be finely adjusted by the vertical handwheel to ensure that the detection base and the measuring cavity fit perfectly. Step S6: Turn on the electronics box, set the initial measurement state, and clear the count state. Step S7: Start the measurement program of the electronics box; Step S8: Record the measurement data and turn off the electronics box; Step S9: Control the vertical motion motor to reverse and raise the measuring cavity, upper clamping plate and lower clamping plate to the initial position; Step S10: Reverse the horizontal handwheel to return the detection base to the sample loading position, remove the sample, and end the measurement.

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