A thermal neutron field monitoring device

Abstract

This application relates to the field of thermal neutron field monitoring technology, and provides a thermal neutron field monitoring device. The thermal neutron field monitoring device includes an absorption sleeve and a thermal neutron detector. The absorption sleeve has an absorption window and a placement cavity arranged sequentially along a first direction. The absorption window is used to absorb a portion of the incident thermal neutrons. The thermal neutron detector includes an incident part located in the placement cavity and facing the absorption window. After a portion of the incident thermal neutrons is absorbed by the absorption window, the remaining portion of the incident thermal neutrons enters the incident part and then enters the thermal neutron detector. By using the absorption sleeve to absorb a portion of the incident thermal neutrons, the count rate of the thermal neutron detector is reduced, thereby meeting the count rate requirements.

Description

Technical Field

[0001] This application relates to the field of thermal neutron field monitoring technology, and in particular to a thermal neutron field monitoring device. Background Technology

[0002] To determine the energy and fluence response of a neutron measuring instrument, a series of neutron reference radiation fields at different energy points need to be established. To ensure uniformity of energy points for neutron reference radiation fields across countries, the International Organization for Standardization (ISO) has recommended neutron reference radiation field energies and generation methods for determining the energy and fluence response of neutron measuring instruments. A thermal neutron field is obtained by using neutrons generated by a moderated reactor or accelerator. This thermal neutron field is then used to determine the energy and fluence response of the neutron measuring instrument. Since reactor power fluctuates over time, a thermal neutron field monitoring device is needed to normalize the neutron fluence rate obtained during the calibration and verification of the neutron measuring instrument to the absolute neutron fluence rate obtained during the establishment of the thermal neutron field. Summary of the Invention

[0003] In view of this, this application aims to provide a thermal neutron field monitoring device that can be used to monitor thermal neutron fields.

[0004] To achieve the above objectives, embodiments of this application provide a thermal neutron field monitoring device, comprising:

[0005] An absorption sleeve having an absorption window and a placement cavity arranged sequentially along a first direction, wherein the absorption window is used to absorb incident thermal neutrons.

[0006] A thermal neutron detector includes an incident section located in the placement cavity and facing the absorption window.

[0007] In some embodiments, the absorbent sleeve includes an outer shell and an inner shell, the inner shell forming the placement cavity, the outer shell forming an assembly cavity, the inner shell being located in the assembly cavity, and the first sidewall of the placement cavity along a first direction and the second sidewall of the assembly cavity along a first direction together forming the absorbent window.

[0008] In some embodiments, there are multiple inner shells, and the lengths of the first sidewalls of each inner shell along a first direction are not equal. The thermal neutron detector can be placed in any of the inner shells, and any of the inner shells can be placed in the assembly cavity.

[0009] In some embodiments, the outer shell has an opening at one end away from the first sidewall along a first direction to form an assembly port, the assembly port communicating with the assembly cavity, and the inner shell being inserted into the assembly cavity through the assembly port.

[0010] In some embodiments, the inner shell includes a cover and a seat. The cover has a first sidewall and a first opening groove. The first opening groove opens on a side away from the first sidewall. The seat has a second opening groove that opens toward the cover. The openings of the first opening groove and the second opening groove are joined together to form the placement cavity.

[0011] In some embodiments, the thermal neutron detector includes a gas chamber and a tail, the incident portion, the gas chamber, and the tail are connected sequentially along a first direction, the gas chamber is used to contain working gas, the maximum dimension of the incident portion along a second direction and the maximum dimension of the tail along a second direction are both smaller than the maximum dimension of the gas chamber along a second direction, the placement cavity includes a front section, a middle section, and a rear section connected sequentially along the first direction, the incident portion is located in the front section, the gas chamber is located in the middle section, and at least a portion of the tail is located in the rear section, wherein the second direction is perpendicular to the first direction.

[0012] In some embodiments, the air chamber has a spherical structure.

[0013] In some embodiments, the thermal neutron detector is a proportional counter.

[0014] In some embodiments, the absorbent sleeve is made of boron-containing polyethylene.

[0015] In some embodiments, the absorbent sleeve contains 18% boron trioxide by mass.

[0016] The thermal neutron field monitoring device provided in this application embodiment, on the one hand, after a portion of the incident thermal neutrons is absorbed by the absorption window, the remaining portion of the incident thermal neutrons enters the incident section to enter the thermal neutron detector. The absorption sleeve absorbs a portion of the incident thermal neutrons, thereby reducing the count rate of the thermal neutron detector to meet the count rate requirements. On the other hand, the placement cavity facilitates the positioning and assembly of the thermal neutron detector. Attached Figure Description

[0017] Figure 1 This is the thermal neutron energy spectrum at an ambient temperature of 20℃.

[0018] Figure 2 This is a schematic diagram of the outer shell structure in one embodiment of this application;

[0019] Figure 3 for Figure 2 A cross-sectional view along the AA direction;

[0020] Figure 4 This is a schematic diagram of the structure of the seat in the first embodiment of this application;

[0021] Figure 5 for Figure 4Cross-sectional view along the BB direction;

[0022] Figure 6 This is a schematic diagram of the structure of the cover in the first embodiment of this application;

[0023] Figure 7 for Figure 4 A cross-sectional view along the CC direction;

[0024] Figure 8 for Figure 3 The outer shell, Figure 5 The seat and Figure 7 Assembly diagram of the middle cover;

[0025] Figure 9 This is a schematic diagram of the structure of the base and the cover in the second embodiment of this application, wherein (a) is the cover and (b) is the base;

[0026] Figure 10 This is a schematic diagram of the structure of the base and the cover in the third embodiment of this application, wherein (a) is the cover and (b) is the base;

[0027] Figure 11 This is a schematic diagram of the structure of the base and the cover in the fourth embodiment of this application, wherein (a) is the cover and (b) is the base;

[0028] Figure 12 This is a schematic diagram of the structure of the base and the cover in the fifth embodiment of this application, wherein (a) is the cover and (b) is the base;

[0029] Figure 13 This is a schematic diagram of the structure of a thermal neutron detector in one embodiment of this application;

[0030] Figure 14 for Figure 13 A schematic diagram of the assembly of the thermal neutron detector and its outer shell;

[0031] Figure 15 This is a flux response diagram of a thermal neutron field monitoring device in one embodiment of this application.

[0032] Explanation of reference numerals in the attached figures

[0033] Absorption sleeve 1; absorption window 11; placement cavity 12; first side wall 121; front section 131; middle section 132; rear section 133; outer shell 101; assembly cavity 101a; second side wall 1011; assembly opening 101b; inner shell 102; cover 1021; first opening slot 10211; first sub-part 102111; base 1022; second opening slot 10221; second sub-part 102212;

[0034] Thermal neutron detector 2; incident section 21; gas chamber section 22; tail section 23; Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and technical features in the embodiments of this application can be combined with each other, and the detailed descriptions in the specific embodiments should be understood as explanations of the purpose of this application and should not be regarded as undue limitations on this application.

[0036] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. The terms "first," "second," etc., used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly including at least one feature. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the embodiments of this application, the unit "MeV" is megaelectron volts, the unit "K" is Kelvin, the unit "cm" is centimeters, and the unit "mm" is millimeters.

[0037] Table 1 shows the neutron reference radiation field energies and generation methods recommended by the International Organization for Standardization for determining the energy and fluence response of neutron measurement equipment.

[0038] Table 1. Neutron reference radiation field used to determine the energy response of the neutron measurement equipment.

[0039]

[0040] In the neutron energies of the neutron reference radiation field in Table 1, 2.53 × 10⁻⁶ ⁻¹⁰ -8 MeV is the typical energy of a neutron when it reaches thermal equilibrium with surrounding matter at 20°C. The neutron energy spectrum at an ambient temperature of 20°C is as follows: Figure 1 As shown, Figure 1 In the diagram, the horizontal axis represents neutron energy, and the vertical axis represents the spectral neutron fluence. The neutron energy follows a Maxwell-Boltzmann distribution, which can be represented by Equation 1:

[0041] Formula 1

[0042] In Equation 1:

[0043] Φ E (E) —Indicates spectral neutron flux, in cm. -2 MeV -1 ;

[0044] E — This represents the neutron energy, measured in MeV;

[0045] k — represents the Boltzmann constant, which is 0.86173423 × 10⁻⁶. -10MeV·K -1 ;

[0046] T — Indicates ambient temperature, in Kelvin (K).

[0047] As shown in Table 1, thermal neutrons are generally obtained by slowing down neutrons produced by reactors or accelerators. The established thermal neutron field, also known as the thermal neutron reference radiation field, is used to determine the response of neutron measurement equipment to energy and flux. Since the reactor power fluctuates over time, a thermal neutron field monitoring device is needed to normalize the neutron flux rate obtained during the calibration and verification of the neutron measurement equipment to the absolute measurement neutron flux rate obtained when the thermal neutron field is established.

[0048] Currently, the flux rate range of the thermal neutron field constructed in the horizontal channel of the China Advanced Research Reactor in the laboratory is (10) 6 ~10 8 )n·cm -2 ·s -1 The typical energy of a neutron is 25.3 meV. Since thermal neutron field monitoring devices are generally placed at an angle to the central beam, it is assumed that the neutron fluence rate at this location is (10-1). 5 ~10 7 )n·cm -2 ·s -1 The count rate of an existing thermal neutron detector, such as the He-3 proportional counter, was simulated using a Monte Carlo program, such as McNP6. The simulated count rate of the existing thermal neutron detector was (3.05491 × 10⁻⁶). 5 ~3.05491×10 7 )s -1 This far exceeds the upper limit of the count rate of existing thermal neutron detectors, meaning that existing thermal neutron detectors cannot be directly used to monitor thermal neutron fields.

[0049] Please see Figures 2 to 8 This application provides a thermal neutron field monitoring device, which includes an absorption sleeve 1 and a thermal neutron detector 2.

[0050] Please see Figure 8 The absorbing sleeve 1 has an absorption window 11 and a placement cavity 12 arranged sequentially along a first direction. The absorption window 11 is used to absorb a portion of the incident thermal neutrons. For example, the absorption window 11 is capable of absorbing most of the thermal neutrons. For example, most of the thermal neutrons means that the absorbed thermal neutrons account for more than 50% of all incident thermal neutrons.

[0051] The thermal neutron detector 2 includes an incident section 21, which is located in the placement cavity 12 and faces the absorption window 11. After being absorbed by the absorption window 11, the remaining thermal neutrons enter the thermal neutron detector 2 through the incident section 21. That is, after a portion of the incident thermal neutrons is absorbed by the absorption window 11, the remaining portion of the incident thermal neutrons enters the incident section 21.

[0052] The thermal neutron field monitoring device provided in this application embodiment, on the one hand, after a portion of the incident thermal neutrons is absorbed by the absorption window 11, the remaining portion of the incident thermal neutrons enters the incident section 21 to enter the thermal neutron detector 2. By using the absorption sleeve 1 to absorb a portion of the incident thermal neutrons, the count rate of the thermal neutron detector 2 is reduced to meet the count rate requirements. On the other hand, the placement cavity 12 facilitates the positioning and assembly of the thermal neutron detector 2.

[0053] In one embodiment, please refer to Figures 2 to 8 The absorbent sleeve 1 includes an outer shell 101 and an inner shell 102. The inner shell 102 has a placement cavity 12, and the outer shell 101 has an assembly cavity 101a. The inner shell 102 is located in the assembly cavity 101a. The first sidewall 121 of the placement cavity 12 along the first direction and the second sidewall 1011 of the assembly cavity 101a along the first direction together constitute the absorbent window 11. Specifically, the outer shell 101 and the inner shell 102 can be independent of each other. That is, the outer shell 101 and the inner shell 102 can be manufactured independently. By manufacturing the outer shell 101 and the inner shell 102 separately, the manufacturing difficulty of the absorbent sleeve 1 can be reduced, thereby simplifying the production process.

[0054] In one embodiment, the inner shell 102 and the outer shell 101 are detachably connected. This facilitates the replacement of the inner shell 102.

[0055] As an example, in one embodiment, please refer to Figures 2 to 8 The outer contour of the inner shell 102 is cylindrical, and the shape of the assembly cavity 101a is also cylindrical. The outer contour of the inner shell 102 is adapted to the shape of the assembly cavity 101a. In this way, the inner shell 102 can be more stably assembled in the assembly cavity 101a.

[0056] As an example, in one embodiment, please refer to Figure 2 The outer contour of the outer shell 101 can be roughly cylindrical.

[0057] In one embodiment, please refer to Figure 2 The outer shell 101 is a one-piece molded structure. This reduces the number of installation steps.

[0058] As an example, in one embodiment, please refer to Figure 8The inner sleeve 102 is tightly fitted or interference-fitted with the assembly cavity 101a. This not only facilitates quick loading and unloading of the inner sleeve 102, but also ensures that the inner sleeve 102 is more securely assembled in the assembly cavity 101a.

[0059] Because the neutron fluence rate of a thermal neutron field varies within a certain range, the fluence response of the thermal neutron field monitoring device also needs to be adjustable within a certain range. In one embodiment, please refer to... Figure 14 and Figure 15 The thermal neutron detector 2 has multiple detection positions and can remain at any one of them. The detection distance between each detection position and the absorption window 11 along the first direction away from the front surface of the thermal neutron detector 2 is... L The values ​​are not equal, and the detection center O of thermal neutron detector 2 is located at the detection position. Thus, the flux response of the thermal neutron field monitoring device is variable.

[0060] In one embodiment, please refer to Figures 2 to 15 There are multiple inner shells 102, and the lengths of the first sidewalls 121 of each inner shell 102 along the first direction are unequal. The thermal neutron detector 2 can be placed in any one of the inner shells 102, and any one of the inner shells 102 can be placed in the assembly cavity 101a. That is, the thermal neutron detector 2 can be selectively placed in any one of the inner shells 102. Each inner shell 102 can be placed in the assembly cavity 101a. On the one hand, the unequal lengths of the first sidewalls 121 of each inner shell 102 along the first direction result in a varying detection distance between the detection center O of the thermal neutron detector 2 and the surface of the absorption window 11 that is away from the neutron detector along the first direction. L They are not equal. Therefore, without replacing the thermal neutron detector 2, by replacing the inner casing 102, the detection center of the thermal neutron detector 2 can be located at different detection positions along the first direction of the absorption sleeve 1. Thus, by varying the detection distance... L This results in different fluence responses in the thermal neutron field monitoring device. Thus, the thermal neutron field monitoring device has good versatility and can be applied to thermal neutron fields with different neutron fluence rates. On the other hand, the same outer shell 101 and the same thermal neutron detector can be reused repeatedly, saving structural components and thus reducing costs.

[0061] In one embodiment, please refer to Figures 2 to 8 The outer shell 101 has an opening at one end away from the first sidewall 121 along a first direction to form an assembly port 101b. The assembly port 101b communicates with the assembly cavity 101a, and the inner shell 102 is inserted into the assembly cavity 101a through the assembly port 101b. For example, during disassembly, the inner shell 102 can be pulled out of the assembly cavity 101a through the assembly port 101b. Thus, the assembly between the inner shell 102 and the outer shell 101 is simple, facilitating quick assembly of the inner shell 102 by operators.

[0062] In one embodiment, the inner shell 102 has a circular cross-section, with a plane perpendicular to the first direction as its cross-section, and the assembly opening 101b also has a circular shape. The area of ​​the assembly opening 101b is not less than the cross-sectional area of ​​the inner shell 102. Thus, the shape of the assembly opening 101b is adapted to the cross-sectional shape of the inner shell 102, so that the inner shell 102 can be inserted into the assembly cavity 101a through the assembly opening 101b.

[0063] In one embodiment, please refer to Figures 4 to 8 The inner shell 102 includes a cover 1021 and a base 1022. The cover 1021 has a first sidewall 121 and a first opening groove 10211. The first opening groove 10211 has an opening on the side away from the first sidewall 121. The base 1022 has a second opening groove 10221 that opens toward the cover 1021. The openings of the first opening groove 10211 and the second opening groove 10221 are joined together to form a placement cavity 12. Specifically, the cover 1021 and the base 1022 are independent of each other. That is, the cover 1021 and the base 1022 can be manufactured independently. For example, in the process of assembling the thermal neutron detector 2 into the inner shell 102, one of the cover 1021 and the base 1022 can be first fitted over the thermal neutron detector 2, and then the other of the cover 1021 and the base 1022 can be closed to complete the installation between the thermal neutron detector 2 and the inner shell 102. This design not only facilitates the manufacturing and processing of the cover 1021 and the base 1022, reducing manufacturing costs, but also facilitates the installation of the thermal neutron detector 2.

[0064] In one embodiment, please refer to Figure 8 and Figure 13 The thermal neutron detector 2 includes a gas chamber 22 for containing working gas. The gas chamber 22 is connected to the side of the incident section 21 away from the absorption window 11 along a first direction. The detection center of the thermal neutron detector 2 is the geometric center of the gas chamber 22.

[0065] In one embodiment, please refer to Figure 8 and Figure 13The thermal neutron detector 2 includes a gas chamber 22 and a tail 23. The incident section 21, gas chamber 22, and tail 23 are sequentially connected along a first direction. The gas chamber 22 is used to contain the working gas. The maximum dimensions of the incident section 21 and the tail 23 along the second direction are both smaller than the maximum dimension of the gas chamber 22 along the second direction. The placement cavity 12 includes a front section 131, a middle section 132, and a rear section 133 sequentially connected along the first direction. The incident section 21 is located in the front section 131, the gas chamber 22 is located in the middle section 132, and at least a portion of the tail 23 is located in the rear section 133. The second direction is perpendicular to the first direction. Specifically, the detection center of the detector is the geometric center of the gas chamber 22. The gas chamber 22 has a relatively large maximum dimension along the second direction. On the one hand, the gas chamber 22 contains more working gas and has a larger sensitive volume, which results in higher sensitivity of the thermal neutron detector 2. On the other hand, this makes it easier to position and install the gas chamber 22 in the middle section 132, thus restricting the movement of the thermal neutron detector 2 along the first direction.

[0066] In one embodiment, please refer to Figure 8 and Figure 13 The portion of the thermal neutron detector 2 furthest from the incident section 21 is located outside the placement chamber 13. For example, a portion of the tail section 23 is located outside the rear section 133. This facilitates the connection of other components to the thermal neutron detector 2.

[0067] In one embodiment, please refer to Figure 8 and Figure 13 The shape of the front section 131 is adapted to the injection section 21, the shape of the middle section 132 is adapted to the air chamber section 22, and the shape of the rear section 133 is adapted to the tail section 23. The shape of the front section 131 is adapted to the injection section 21 to accommodate the injection section 21, the shape of the middle section 132 is adapted to the air chamber section 22 to accommodate the air chamber section 22, and the shape of the rear section 133 is adapted to the tail section 23 to accommodate the tail section 23.

[0068] In one embodiment, please refer to Figure 13 The gas chamber 22 has a spherical structure. Specifically, the center of the gas chamber 22 is the detection center of the thermal neutron detector 2. This shape not only facilitates the positioning of the gas chamber 22, but also effectively distinguishes the different efficiencies of the gas chamber 22 in detecting thermal neutrons when it is at different positions of the absorption sleeve 1 along the first direction.

[0069] In one embodiment, please refer to Figure 8 and Figure 13 Both the incident section 21 and the tail section 23 are cylindrical. The front section 131 is cylindrical to match the incident section 21, and the rear section 133 is cylindrical to match the tail section 23. The diameters of the incident section 21 and the tail section 23 are both smaller than the diameter of the air chamber section 22.

[0070] As an example, in one embodiment, please refer to Figure 5 , Figure 7 , Figure 8 and Figure 13 The first opening slot 10211 includes a front section 131 and a first sub-section 102111 communicating with the front section. The opening of the first opening slot 10221 is located on the side of the first sub-section 102111 away from the front section 131. The second opening slot 10221 includes a second sub-section 102212 and a rear section 133 communicating with the second sub-section 102212. The opening of the second opening slot 10221 is located on the side of the second sub-section 102212 away from the rear section 133. The first sub-section 102111 and the second sub-section 102212 are joined together to form a middle section 132. This design facilitates the assembly of the thermal neutron detector 2 into the inner housing 102. For example, a portion of the gas chamber 22 and the incident portion 21 can be inserted into the front section 131 and the first sub-section 102111 through the opening of the first opening slot 10221, and then the second sub-section 102212 and the rear section 133 can be fitted onto the remaining portion of the gas chamber 22 and the tail section 23, so that the inner shell 102 and the thermal neutron detector 2 can be quickly assembled together.

[0071] It is understood that, in one embodiment, both the cover 1021 and the base 1022 can be tightly fitted with the assembly cavity 101a of the outer shell 101 to complete the fixation of the thermal neutron detector 2, the inner shell 102 and the outer shell 101.

[0072] In one embodiment, please refer to Figure 13 The thermal neutron detector 2 is a proportional counter. The signal amplitude of the proportional counter is higher than that of the ionization chamber.

[0073] In one embodiment, the thermal neutron detector 2 is a He-3 proportional counter. That is, the working gas of the thermal neutron detector 2 is He-3 (i.e., helium with a mass number of 3).

[0074] He-3 (helium with a mass number of 3) is a helium isotope gas that is colorless, odorless, and tasteless. A He-3 proportional counter is a proportional counter that uses He-3 gas as its working gas. The He-3 proportional counter is a neutron detector based on the thermal neutron-He-3(n, p)T nuclear reaction method. He-3 has a very high reaction cross-section for thermal neutrons, reaching 5400 Å, making it a highly efficient thermal neutron detector.

[0075] In one embodiment, the thermal neutron detector 2 is a BF3 proportional counter. That is, the working gas of the thermal neutron detector 2 is BF3 (i.e., boron fluoride).

[0076] The absorber sleeve 1 is made of a material with a large thermal neutron absorption cross-section. A material with a large thermal neutron absorption cross-section can absorb most thermal neutrons, thereby reducing the count rate of the thermal neutron detector 2. Materials with a large thermal neutron absorption cross-section include, but are not limited to, He-3, Li-6 (lithium with a mass number of 6), B-10 (boron with a mass number of 10), Cd-113 (cadmium with a mass number of 113), Gd-155 (gadolinium with a mass number of 155), and U-235 (uranium with a mass number of 235).

[0077] In one exemplary embodiment, the absorber sleeve 1 is made of boron-containing polyethylene. Boron-containing polyethylene is low in cost and has high thermal neutron absorption efficiency.

[0078] For example, boron-containing polyethylene can be polyethylene doped with boron carbide, boron nitride, or boron oxide.

[0079] In one embodiment, the absorber sleeve 1 is made of boron trioxide and polyethylene. Boron trioxide is B2O3. Boron-containing polyethylene, formed by mixing boron trioxide and polyethylene, has good mechanical properties and is easy to process.

[0080] In one embodiment, the mass percentage of boron trioxide in the material of the absorbing sleeve 1 is 18%. This ensures that the absorbing sleeve 1 absorbs a moderate number of neutrons, satisfying the requirement that the count rate of the thermal neutron field monitoring device is within (50~500) s. -1 Within a suitable range.

[0081] For example, the relative atomic number of each isotope in boron-containing polyethylene includes: 0.102931 for B-10, 0.414310 for B-11 (boron with a mass number of 11), 0.775862 for O (oxygen), 5.85714 for C (carbon), and 1.17143 for H (hydrogen).

[0082] In one embodiment, the thickness of the absorption window 11 along the first direction can be 3 mm.

[0083] In one embodiment, please refer to Figures 1 to 13The outer contours of both the outer shell 101 and the inner shell 102 are cylindrical, and the assembly cavity 101a is cylindrical. The thickness of the outer shell 101 along the first direction can be between 119.9 mm and 120.1 mm. For example, the thickness of the outer shell 101 along the first direction is 120 mm. The diameter of the outer shell 101 can be between 79.9 mm and 80.1 mm. For example, the diameter of the outer shell 101 can be 80 mm. The thickness of the assembly cavity 101a along the first direction is between 115.4 mm and 115.6 mm. For example, the thickness of the assembly cavity 101a along the first direction is 115.5 mm. The diameter of the assembly cavity 101a is between 39.85 mm and 40.05 mm. For example, the diameter of the assembly cavity 101a is 40 mm. The thickness of the inner shell 102 along the first direction is between 115.4 mm and 115.6 mm. For example, the thickness of the inner shell 102 along the first direction is 115.5 mm. The diameter of the inner shell 102 is between 39.95 mm and 40.1 mm. For example, the diameter of the inner shell 102 is 40 mm.

[0084] For example, in one embodiment, this application simulates the count rate of a He-3 proportional counter using a Monte Carlo program such as Mcnp6. The simulated He-3 proportional counter is used to detect thermal neutrons at a He-3 gas pressure of 2 atm (standard atmospheric pressure). The thermal neutron monitoring device is placed at a position at a certain angle to the central beam, with the neutron fluence rate at that position being (10^- ... 5 ~10 7 )n·cm -2 ·s -1 For example, the Monte Carlo program can be used to calculate the count rate of the He-3 proportional counter. The simulated He-3 proportional counter's charge response, calculated by the Monte Carlo program, is 3.05491 cm⁻¹. 2 .

[0085] The relationship between injection response and count rate can be expressed by Equation 2:

[0086] Formula 2

[0087] In Equation 2:

[0088] n —Indicates the counting rate, s -1 ;

[0089] F R —Indicates injection response, cm 2 ;

[0090] —Indicates neutron fluence rate, n·cm -2 ·s -1 .

[0091] The counting rate of the analog He-3 proportional counter can be calculated from Equation 2 as (3.05491 × 10⁻⁶). 5 ~3.05491×10 7 )s -1 This far exceeds the upper limit of the count rate of existing He-3 proportional counters.

[0092] For example, a thermal neutron field monitoring device according to an embodiment of this application is simulated using a Monte Carlo program such as Mcnp6. Please refer to [link to relevant documentation]. Figures 4 to 15 There are five inner shells 102, and the lengths of the first sidewalls 121 of the five inner shells 102 along the first direction are not equal. The five inner shells 102 ensure that the detection distances L between the detection center O of the neutron detector and the front surface of the absorption window 11 away from the neutron detector along the first direction are 3cm, 4cm, 5cm, 6cm, and 7cm, respectively. The thermal neutron detector 2 uses a He-3 proportional counter, the pressure of the He-3 gas is 2 atm (standard atmospheric pressure), and the neutron fluence rate is (10... 5 ~10 7 )n·cm -2 ·s -1 Please refer to Table 2 for the results. Figure 15 ,

[0093] Table 2 Flux response and count rate of the thermal neutron field monitoring device of this application

[0094]

[0095] From Table 2 and Figure 15 It can be seen that at a neutron flux rate of 10 5 n·cm -2 ·s -1 At this time, a thermal neutron field monitoring device with a detection distance of 4 cm using a He-3 proportional counter can be selected. The counting rate of this thermal neutron field monitoring device is 8.82776E+01 s. -1 At a neutron fluence rate of 10 7 n·cm -2 ·s -1 At that time, a thermal neutron field monitoring device with a detection distance of 5 cm and a He-3 proportional counter was selected. The counting rate of the thermal neutron field monitoring device at this time was 3.37778E+02 s. -1 Thus, the count rate of the thermal neutron field monitoring device is satisfied to be within (50~500) s. -1 Within a suitable range.

[0096] The above description is merely a preferred embodiment of this application and is not intended to limit the application. Various modifications and variations can be made to this application by those skilled in the art. All modifications, equivalent substitutions, improvements, etc., within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A thermal neutron field monitoring device, characterized by, The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device.

2. The thermal neutron field monitoring device of claim 1, wherein, The application relates to a thermal neutron field monitoring device.

3. The thermal neutron field monitoring device of claim 1, wherein, The application relates to a thermal neutron field monitoring device.

4. The thermal neutron field monitoring device of claim 1, wherein, The application relates to a thermal neutron field monitoring device.

5. The thermal neutron field monitoring device of claim 4, wherein, The application relates to a thermal neutron field monitoring device.

6. The thermal neutron field monitoring device of claim 1, wherein, The application relates to a thermal neutron field monitoring device.

7. The thermal neutron field monitoring device of claim 1, wherein, The application relates to a thermal neutron field monitoring device.

8. The thermal neutron field monitoring device of claim 7, wherein, The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. The application relates to a thermal neutron field monitoring device. 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