Delayed neutron calibration source and activation method thereof

Abstract

The embodiment of the invention provides a delayed neutron calibration source and an activation method thereof. The delayed neutron calibration source comprises a shielding part, a containing device, a detector and an accelerator. A first containing cavity extending in the height direction and a first channel communicated with the first containing cavity are formed in the shielding part, and the shielding part is used for shielding radiation. The containing device is arranged in the first containing cavity and corresponds to the first channel, and the containing device is used for containing the reaction target piece. At least part of the detector is arranged in the first containing cavity and used for detecting the counting rate of neutrons in the first containing cavity. A beam emitted by the accelerator can pass through the first channel and irradiate the reaction target. According to the embodiment of the invention, the condition that a delayed neutron radiation field is generated by leakage in a water loop in the nuclear fission process can be simulated, and detection and calibration are facilitated. By controlling the beam intensity, the emissivity of delayed neutrons can be changed, and different neutron radiation fields can be simulated.

Description

Technical Field

[0001] The present application relates to the field of delayed neutron technology, and in particular to a delayed neutron calibration source and an activation method thereof. Background Art

[0002] During the operation of nuclear reactors, the main accident risk comes from the leakage of radioactive materials caused by structural damage. Monitoring delayed neutrons in reactor loop water is one of the effective methods to detect whether fuel elements are damaged. In related technologies, since the radiation field of reactor loop water is difficult to calibrate, there is a lack of a delayed neutron calibration source to simulate and measure the neutron radiation field near the delayed neutron monitor. Summary of the invention

[0003] In view of this, an embodiment of the present application provides a delayed neutron calibration source and an activation method thereof, which are used to simulate and measure the neutron radiation field near a delayed neutron monitor.

[0004] To achieve the above-mentioned purpose, the first aspect of the embodiment of the present application provides a delayed neutron calibration source, including:

[0005] A shielding part, wherein a first accommodating cavity extending in a height direction and a first channel communicating with the first accommodating cavity are formed inside the shielding part, and the shielding part is used for shielding radiation;

[0006] A containing device, the containing device is arranged in the first containing cavity and corresponds to the first channel, and the containing device is used to contain a reaction target;

[0007] A detector, at least part of which is disposed in the first containing cavity, and the detector is used to detect a neutron count rate in the first containing cavity;

[0008] An accelerator, wherein a beam emitted by the accelerator can pass through the first channel and irradiate the reaction target.

[0009] In one embodiment, the shielding portion is provided with a placement platform in the first accommodating cavity, the accommodating device is arranged on the placement platform, and the center line of the first channel passes through the centroid of the accommodating device.

[0010] In one embodiment, the shielding portion includes a second channel, the second channel is connected to the first accommodating cavity, the detector can extend into the first accommodating cavity through the second channel, wherein the center line of the second channel intersects the center line of the first channel; and / or,

[0011] The centerline of the second channel coincides with the centerline of the receiving device.

[0012] In one embodiment, the shielding portion includes a first shielding member and a second shielding member arranged along a height direction of the shielding portion, and the first shielding member and the second shielding member define the first accommodating cavity inside.

[0013] In one embodiment, the first channel is arranged on the first shielding member, and the first channel penetrates the inner wall of the first accommodating cavity along a first direction, and the second channel is arranged on the second shielding member, and the second shielding member penetrates the inner wall of the first accommodating cavity along a height direction of the shielding part, wherein the first direction intersects with the height direction.

[0014] In one embodiment, the first shielding component includes a first sub-component and a second sub-component, one side of the first sub-component is snap-fitted with the second sub-component, and the other side of the first sub-component is snap-fitted with the second shielding component; the first sub-component and the second sub-component at least form part of the first accommodating cavity.

[0015] In one embodiment, the accommodating device is provided with a penetration hole, and the detector can penetrate the penetration hole.

[0016] In one embodiment, the wall thickness of the first accommodating cavity is not less than 80 mm.

[0017] A second aspect of an embodiment of the present application provides an activation method for a delayed neutron calibration source, which is applied to the delayed neutron calibration source, wherein the delayed neutron calibration source comprises a shielding portion, a containing device, a detector and an accelerator; a first containing cavity and a first channel connected to the first containing cavity are formed inside the shielding portion, the first containing cavity is used to contain a reaction target, and the shielding portion can shield radiation; the containing device is disposed in the first containing cavity, and is used to contain the reaction target; at least part of the detector is disposed in the first containing cavity, and the detector is used to detect the neutron count rate in the first containing cavity; the beam emitted by the accelerator can pass through the first channel to irradiate the reaction target; the activation method of the delayed neutron calibration source comprises:

[0018] Filling the reaction target in the containing device;

[0019] Setting the beam intensity of the accelerator to a first beam intensity;

[0020] Controlling the beam of the accelerator to irradiate the reaction target;

[0021] The detector is controlled to detect delayed neutrons to obtain a first counting rate.

[0022] In one embodiment, controlling the beam of the accelerator to irradiate the reaction target comprises:

[0023] Controlling the beam of the accelerator to irradiate the reaction target to generate precursor nuclei;

[0024] When the precursor nucleus reaches a saturation state, controlling the beam of the accelerator to stop irradiating the reaction target;

[0025] The delayed neutron calibration source is left to stand until the prompt neutrons in the containing device disappear.

[0026] In the embodiment of the present application, by setting a first accommodating cavity on the shielding part, the reaction target can be irradiated by the beam emitted by the accelerator in the first accommodating cavity, and fission occurs to produce delayed neutrons. In this way, the situation in which leakage occurs in the water circuit during nuclear fission and a delayed neutron radiation field is generated can be simulated. By controlling the beam intensity, the emission rate of delayed neutrons can be changed, and different neutron radiation fields can be simulated. On the other hand, the setting of the shielding part can block the internal radiation from leaking outward and prevent harm to the surrounding environment and operators. At the same time, it isolates external interference radiation from entering the interior, ensures that the calibration source works without interference, and maintains a stable radiation environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of a delayed neutron calibration source in an embodiment of the present application;

[0028] Figure 2 for Figure 1 A schematic diagram of the structure of the medium containing device;

[0029] Figure 3 This is a flow chart of a method for activating a delayed neutron calibration source in an embodiment of the present application.

[0030] Description of Reference Numerals

[0031] 10. Delayed neutron calibration source; 1. Shielding part; 11. First accommodating chamber; 12. First channel; 13. Second channel; 14. Placement table; 15. First shielding member; 151. First sub-member; 152. Second sub-member; 16. Second shielding member; 2. Accommodating device; 21. Through hole; 3. Detector; 4. Accelerator. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0033] In the description of the embodiments of the present application, it should be noted that the terms "transmission direction of the ray", "height direction", "first direction", "second direction", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings. These orientation terms are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. The present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0034] The present application embodiment provides a delayed neutron calibration source 10, see Figure 1 The delayed neutron calibration source 10 includes a shielding portion 1, a containing device 2, a detector 3 and an accelerator 4. A first containing cavity 11 extending in the height direction and a first channel 12 connected to the first containing cavity 11 are formed inside the shielding portion 1. The shielding portion 1 is used to shield radiation. The containing device 2 is disposed in the first containing cavity 11 and is disposed corresponding to the first channel 12. The containing device 2 is used to contain a reaction target. At least part of the detector 3 is disposed in the first containing cavity 11. The detector 3 is used to detect the neutron count rate in the first containing cavity 11. The beam emitted by the accelerator 4 can pass through the first channel 12 and irradiate the reaction target.

[0035] The delayed neutron calibration source 10 is a device specially used for calibrating and detecting neutron-related measuring equipment. Delayed neutrons refer to neutrons emitted when certain radioactive nuclides in nuclear fission products decay. Unlike prompt neutrons, they are not generated at the moment of fission, but are emitted after a certain time delay. The delayed neutron calibration source 10 can accurately provide such neutrons and simulate different neutron radiation fields.

[0036] The delayed neutron calibration source 10 comprises a shielding portion 1 , a containing device 2 , a detector 3 and an accelerator 4 .

[0037] The specific material of the shielding part 1 is not limited here. The material has strong absorption and scattering capabilities for radiation, and its function is to block the internal radiation from leaking outward to prevent harm to the surrounding environment and operators. At the same time, it isolates external interference radiation from entering the interior, ensures that the calibration source is not disturbed, and maintains a stable radiation environment.

[0038] Exemplarily, the shielding part 1 is made of hydrogen-containing material, for example, the shielding part 1 is a boron-containing polyethylene cylinder with a diameter of 240 mm and a height of 460 mm, and a hollow cylinder with a diameter of 80 mm and a height of 300 mm is hollowed out at the center thereof to form the first accommodating chamber 11 .

[0039] The container 2 is usually a high temperature and radiation resistant container made of special ceramics or metal alloys. It provides a stable and closed storage space for the reaction target, ensures that the target is in a predetermined position, enables the accelerator 4 beam to act accurately on the target, and can also contain the products generated by the reaction to prevent them from leaking and contaminating the equipment.

[0040] For example, the container 2 is a titanium alloy cylindrical cup-shaped structure with a 2 mm circular bottom surface, a wall thickness of 2 mm, an inner diameter of the volume part of 50 mm, an outer diameter of 70 mm, and a height of 50 mm. The use of titanium alloy can reduce the corrosion of the solution to the container on the one hand, and reduce the blocking effect on the proton beam inflow and delayed neutron emission on the other hand.

[0041] Exemplarily, sensors are installed on the outside or inside of the containing device 2 to monitor the temperature and pressure in real time to prevent abnormal reactions.

[0042] Detector 3: It is an instrument that can interact with neutrons and convert information such as neutron flux into electrical signals and counting signals. Common detectors include scintillation detector 3, gas detector 3, etc. Scintillation detector 3 uses the interaction between neutrons and scintillators to emit light, and then generates electrical signals through photoelectric conversion elements; gas detector 3 relies on neutrons ionizing gas to produce ion pairs to record signals, which is used to accurately monitor the number and energy of neutrons in the containment cavity.

[0043] An accelerator 4 is a device that can accelerate charged particles (such as protons, electrons, etc.) using electric and magnetic fields to reach a high energy state. The accelerated particle beam has enough energy to hit the reaction target to trigger a nuclear reaction, providing an energy source for generating delayed neutrons. Common types include linear accelerators 4 and cyclotron accelerators 4.

[0044] Exemplarily, the accelerator 4 is equipped with a beam focusing and shaping system to optimize the beam quality.

[0045] Exemplarily, the accelerator 4 controls the beam intensity to a typical beam intensity of 1 μA / s, a beam energy of 100 MeV, particles are protons, and a beam spot size diameter of 25 mm-50 mm.

[0046] In some embodiments, the accelerator 4 is connected to an intelligent control system to flexibly adjust the beam energy and intensity according to experimental and calibration requirements; a beam monitor is added downstream to provide real-time feedback on the beam status, and the calibration source can be automatically adjusted according to different conditions.

[0047] The first accommodating cavity 11 is located inside the shielding part 1 and is a space reserved for key components such as the accommodating device 2 and the detector 3. It has a regular shape and extends in the height direction to facilitate layout. It can make full use of the internal space of the shielding part 1, so that the components are reasonably distributed and work stably in coordination.

[0048] The first channel 12 is a tubular channel on the shielding part 1, connecting the inside and the outside, for the beam emitted by the accelerator 4 to pass through, accurately guiding the beam to the reaction target. The channel diameter and length are accurately designed according to the beam energy and intensity to prevent beam scattering.

[0049] The reaction target is a key component for generating a nuclear reaction under the irradiation of the particle beam generated by the accelerator 4. The specific composition of the reaction target is not limited here, and is specifically determined according to the nuclear reaction raw materials corresponding to the actual calibration.

[0050] Exemplarily, the reaction target may be radioactive nuclides such as uranium and plutonium that can be used for fission reactions. After being hit by high-energy particles (such as protons, neutrons, etc.) generated by the accelerator 4, these nuclides will undergo fission reactions and produce a variety of products including delayed neutrons.

[0051] It should be noted that the reaction target needs to have a certain concentration to ensure that the reaction data can be measured easily. Taking the uranium solution as an example, the uranium concentration should not be less than 0.01g / ml, so that no less than 10 4 The delayed neutron emission rate is on the order of / s.

[0052] In the embodiment of the present application, by setting a first accommodating cavity 11 on the shielding part 1, the reaction target can be irradiated by the beam emitted by the accelerator 4 in the first accommodating cavity 11, and fission occurs to produce delayed neutrons. In this way, the situation in which leakage occurs in the water circuit during nuclear fission and a delayed neutron radiation field is generated can be simulated. By controlling the beam intensity, the emission rate of delayed neutrons can be changed to simulate different neutron radiation fields. On the other hand, the setting of the shielding part 1 can block the internal radiation from leaking outward and prevent harm to the surrounding environment and operators. At the same time, it isolates external interference radiation from entering the interior, ensures that the calibration source works without interference, and maintains a stable radiation environment.

[0053] In some embodiments, see Figure 1 The shielding part 1 is provided with a placing platform 14 in the first accommodating cavity 11 , the accommodating device 2 is arranged on the placing platform 14 , and the center line of the first channel 12 passes through the centroid of the accommodating device 2 .

[0054] The placement table 14 is a bearing structure specially built for the shielding part 1 in the first accommodating cavity 11. It is generally made of a material that is strong, high temperature resistant and has certain radiation protection performance, and the specific material is not limited here. The placement table 14 provides a stable and flat placement surface for the accommodating device 2 to ensure that the accommodating device 2 will not be displaced due to external vibrations, slight shaking of the equipment operation, etc.

[0055] Exemplarily, the placement table 14 is made of special alloy steel or specially treated ceramic material.

[0056] The centroid is also called the geometric center. For the container 2, it refers to the center position of the container 2 in the spatial geometry. The centroid calculation method varies for containers 2 of different shapes. For example, the centroid of a regular cylinder is at the midpoint of the cylinder's central axis. The centroid of a cuboid is the intersection of the three diagonals.

[0057] An additional placement table 14 is provided in the first accommodating chamber 11 to securely place the accommodating device 2. At the same time, it is emphasized that the center line of the first channel 12 accurately passes through the centroid of the accommodating device 2, and the beam emitted by the accelerator 4 can reach the core area of ​​the reaction target in the accommodating device 2 directly and accurately along the ideal path, ensuring the stability of the reaction while reducing the geometric error of the beam irradiation path on the reaction target, which is conducive to reducing the calculation difficulty of the verification and improving the verification accuracy.

[0058] In some embodiments, see Figure 1 The shielding portion 1 includes a second channel 13 , which is connected to the first accommodating cavity 11 , and the detector 3 can extend into the first accommodating cavity 11 through the second channel 13 , wherein the center line of the second channel 13 intersects with the center line of the first channel 12 .

[0059] The second channel 13 is another tubular structure on the shielding part 1. The second channel 13 has a similar structure to the first channel 12 and also has a specific geometric shape and size. The second channel 13 is used to provide space for the detector 3 to enter and exit the first accommodating cavity 11, to ensure that the detector 3 can smoothly reach the designated detection position, and at the same time to maintain the shielding integrity of the shielding part 1 to the greatest extent to avoid a large amount of radiation leakage.

[0060] The center line of the first channel 12 or the second channel 13 is a virtual straight line, which accurately locates the geometric center direction of the channel. For a cylindrical channel, the center line is the central axis of the cylinder.

[0061] The second channel 13 is provided to facilitate the detector 3 to flexibly enter and exit the first accommodating cavity 11. The center line of the second channel 13 intersects with the center line of the first channel 12, that is, the first channel 12 and the second channel 13 extend in different directions in the shielding part 1 in space, and there is a certain intersection space, which is conducive to the detection of the detector 3 and improves the compactness of the structure of the detector 3.

[0062] In some embodiments, see Figure 1 , the center line of the second channel 13 coincides with the center line of the accommodating device 2.

[0063] The center line of the second channel 13 coincides with the center line of the containing device 2, which means that when the detector 3 enters and exits through the second channel 13, the moving trajectory goes straight through the center of the containing device 2, aiming to make the detector 3 as close as possible to the core area of ​​the reaction target, to fully and accurately detect the generation of delayed neutrons by nuclear reactions, and to ensure the reliability and accuracy of the detection data.

[0064] In some embodiments, see Figure 1 The shielding part 1 includes a first shielding member 15 and a second shielding member 16 arranged along a height direction of the shielding part 1 , and the first shielding member 15 and the second shielding member 16 define a first accommodating cavity 11 inside.

[0065] The shielding part 1 is jointly formed by the first shielding member 15 and the second shielding member 16 spliced ​​in the height direction, and the first accommodating cavity 11 is precisely defined. This modular assembly mode is not only conducive to controlling the precision and quality of components during production and manufacturing, but also provides convenience for subsequent maintenance and upgrading of the equipment; at the same time, the shielding members that are reasonably spliced ​​can efficiently achieve the radiation shielding goal, which meets the strict radiation control requirements of the delayed neutron calibration source 10.

[0066] In some embodiments, see Figure 1 The first channel 12 is arranged on the first shielding member 15, and the first channel 12 passes through the inner wall of the first accommodating cavity 11 along the first direction. The second channel 13 is arranged on the second shielding member 16, and the second shielding member 16 passes through the inner wall of the first accommodating cavity 11 along the height direction of the shielding part 1, wherein the first direction intersects with the height direction.

[0067] Here, the first direction is not specifically limited and can be any direction. For the convenience of description, the first direction of the embodiment of the present application is the direction shown in the drawings.

[0068] The first channel 12 is placed on the first shielding member 15, and passes straight through the inner wall of the first accommodating cavity 11 along the first direction, creating conditions for the precise introduction of the beam of the accelerator 4, so that the beam can smoothly impact the reaction target in the accommodating device 2; the second channel 13 is located on the second shielding member 16, and passes vertically through the inner wall of the first accommodating cavity 11 along the height direction of the shielding part 1, so as to facilitate the detector 3 to flexibly enter and exit the first accommodating cavity 11 and monitor the neutron status in the cavity in real time; and it is specifically pointed out that the first direction intersects with the height direction, in order to make the beam path and the entry and exit path of the detector 3 reasonably staggered in space, so as to achieve a layout effect of non-interference and coordinated work.

[0069] In some embodiments, see Figure 1 The first shielding member 15 includes a first sub-member 151 and a second sub-member 152. One side of the first sub-member 151 is engaged with the second sub-member 152, and the other side of the first sub-member 151 is engaged with the second shielding member 16. The first sub-member 151 and the second sub-member 152 at least form a part of the first accommodation cavity 11.

[0070] Snap-fit ​​is a mechanical connection method in which two or more parts are interlocked and clamped together through a protrusion and groove structure of a specific shape, thereby achieving a stable connection.

[0071] The specific method of snap-fit ​​is not limited here. In the case of the first shielding component 15 of the delayed neutron calibration source 10, the first subcomponent 151 and the second subcomponent 152 are connected by snap-fit, and this connection does not require the use of complex bolts, nuts and other connectors, and can achieve a tight assembly effect by relying on the cleverly designed snap-fit ​​structure of the components themselves. The snap-fit ​​requires that the protruding part (such as the tenon) accurately fits the size and shape of the groove part (such as the mortise), and that the friction and bite force after the two are combined are sufficient to resist the influence of external forces such as vibration and displacement generated during the operation of the equipment, maintain structural stability, and ensure that the shielding function is not disturbed.

[0072] The first shielding component 15 is assembled in a modular form, and is disassembled into a first sub-component 151 and a second sub-component 152, which are connected to the second shielding component 16 and each other by means of a snap-fitting method. Such an ingenious structure, on the one hand, is conducive to the precise control of the quality and processing accuracy of each sub-component in the production process. On the other hand, it brings great convenience to the subsequent maintenance and replacement of components of the equipment. When a sub-component fails, ages, or needs to be upgraded, it can be quickly disassembled and replaced, greatly shortening the downtime; furthermore, the flexibly combined sub-components can efficiently enclose a first accommodating cavity 11 that adapts to the internal layout of the equipment, meeting various functional requirements.

[0073] In some embodiments, see Figure 1 to Figure 2 The accommodating device 2 is provided with a through hole 21 , and the detector 3 can pass through the through hole 21 .

[0074] The through hole 21 is a through hole structure opened on the receiving device 2 .

[0075] The shape of the through hole 21 is not limited here, and is specifically designed according to the outer contour of the detector 3 .

[0076] Exemplarily, the perforated holes 21 are in regular geometric shapes such as circles or squares.

[0077] The setting of the through hole 21 provides a predetermined passage for the detector 3 to pass through the container 2, so that the detector 3 can reach a specific position inside the container 2 and accurately detect the neutron situation in the relevant area. The aperture size of the through hole 21 needs to accurately match the size of the detector 3, so as to ensure that the detector 3 passes smoothly and minimize the impact on the integrity of the container 2 and the internal radiation environment.

[0078] In some embodiments, see Figure 1 , the wall thickness of the first accommodating chamber 11 is not less than 80 mm.

[0079] The wall thickness of the first accommodating chamber 11 refers to the thickness of the material layer constituting the wall of the first accommodating chamber 11 , which is the vertical distance from the inner surface to the outer surface of the chamber.

[0080] The wall thickness of the first accommodating cavity 11 is not less than 80 mm. The specific wall thickness is not limited here. For example, it can be 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 86 mm, 87 mm, 88 mm, 89 mm, 90 mm, etc.

[0081] Exemplarily, the wall thickness of the first accommodating cavity 11 is 80 mm, which can effectively block the influence of room scattered neutrons on the radiation field of the delayed neutron calibration source 10, and its shielding effect for neutrons with energy less than 1 eV is greater than 98%.

[0082] The requirement that the wall thickness is not less than 80 mm means that when manufacturing the delayed neutron calibration source 10, the shielding material layer constituting the first accommodating cavity 11 needs to meet a certain thickness standard. This is to ensure that the first accommodating cavity 11 can effectively shield internal radiation and prevent radiation from leaking to the external environment, while also resisting possible external interference radiation and providing adequate protection for the equipment in the accommodating cavity.

[0083] The present application embodiment provides a method for activating a delayed neutron calibration source. Figure 1 and Figure 3 , applied to a delayed neutron calibration source 10, which includes a shielding part 1, a containing device 2, a detector 3 and an accelerator 4. A first containing cavity 11 and a first channel 12 connected to the first containing cavity 11 are formed inside the shielding part 1. The first containing cavity 11 is used to contain a reaction target, and the shielding part 1 can shield radiation. The containing device 2 is arranged in the first containing cavity 11 to contain a reaction target. At least part of the detector 3 is arranged in the first containing cavity 11, and the detector 3 is used to detect the neutron count rate in the first containing cavity 11. The beam emitted by the accelerator 4 can pass through the first channel 12 to irradiate the reaction target. The activation method of the delayed neutron calibration source includes the following steps S101 to S105:

[0084] Step S101, loading a reaction target into a containing device.

[0085] The reaction target, as the key material basis for the nuclear reaction, is filled in the container 2. The container 2 can provide a stable placement environment for the target, ensure that the subsequent accelerator 4 beam acts accurately on the target, and contain the products generated by the reaction to prevent leakage and contamination of the equipment and the surrounding environment.

[0086] Step S102, setting the beam intensity of the accelerator to a first beam intensity.

[0087] According to the experimental or calibration requirements, the beam intensity of the accelerator 4 is accurately set to the first beam intensity. The beam intensity is a key parameter that affects the intensity of the nuclear reaction and the amount of delayed neutrons produced. Different beam intensities will trigger nuclear reactions of different scales. The appropriate first beam intensity setting is a prerequisite for obtaining accurate calibration data later.

[0088] Step S103, controlling the accelerator beam to irradiate the reaction target.

[0089] Control the accelerator 4 to allow the beam of a given intensity to stably and accurately irradiate the reaction target. This step is the core operation to trigger the nuclear reaction and promote the generation of delayed neutrons. The beam interacts with the target, and the atomic nuclei absorb energy to undergo fission and excitation, thereby producing delayed neutrons.

[0090] Step S104, controlling the detector to detect delayed neutrons to obtain a first counting rate.

[0091] In the context of delayed neutron calibration, the count rate specifically refers to the number of delayed neutrons detected by the detector 3 per unit time. For example, if the detector 3 detects 100 delayed neutrons within 1 second, the count rate at this time is 100 / second. It is an important indicator for quantifying the generation of delayed neutrons. When the beam intensity of the accelerator 4 is high, more energy is applied to the reaction target, the nuclear reaction triggered is more intense, and more delayed neutrons are generated, so the count rate will increase.

[0092] Then the detector 3 is started to detect the delayed neutrons generated by the above nuclear reaction. The detector 3 converts the information such as the neutron flux into a counting signal to obtain a first counting rate, which is used to quantitatively reflect the output of the delayed neutrons to detect the activation of the delayed neutrons in the delayed neutron calibration source.

[0093] In the embodiment of the present application, by setting a first accommodating cavity 11 on the shielding part 1, the reaction target can be irradiated by the beam emitted by the accelerator 4 in the first accommodating cavity 11, and fission occurs to produce delayed neutrons. In this way, the situation in which leakage occurs in the water circuit during nuclear fission and a delayed neutron radiation field is generated can be simulated. By controlling the beam intensity, the emission rate of delayed neutrons can be changed to simulate different neutron radiation fields. On the other hand, the setting of the shielding part 1 can block the internal radiation from leaking outward and prevent harm to the surrounding environment and operators. At the same time, it isolates external interference radiation from entering the interior, ensures that the calibration source works without interference, and maintains a stable radiation environment. .

[0094] In some embodiments, see Figure 1 and Figure 3 , step S103 includes:

[0095] The accelerator beam is controlled to irradiate the reaction target to produce precursor nuclei.

[0096] Precursor nuclei are a type of key intermediate product in the nuclear reaction process. When the beam of accelerator 4 accurately irradiates the reaction target according to the set intensity, the target nuclei absorb the energy carried by the beam particles, undergo nuclear reaction processes such as fission and excitation, and then generate a series of unstable nuclides, which are the pioneer nuclei. Taking uranium 235 as a reaction target as an example, under the impact of a high-energy proton beam, the uranium 235 nucleus fissions to produce many fission fragments such as Br-87 and I-137, some of which will further decay into pioneer nuclei, which have the potential to produce delayed neutrons later.

[0097] The delayed neutron precursor nucleus spontaneously decays and fissions, producing a certain number of delayed neutrons, which is the emission rate.

[0098] It should be noted that the emission rate of delayed neutrons is related to many factors. Here, taking uranium as an example, assuming that the uranium concentration is c (kg·m -3 ), the volume of the reaction solution participating in the reaction is V(m 3 ), proton beam intensity A(A), and ensure that the irradiated area S(m 2 ) is slightly larger than the beam spot size, then under the reaction cross section σ, the number of uranium fission particles per unit time is:

[0099]

[0100] After that, uranium fission occurs, and a certain proportion of K1 is converted into delayed neutron precursor nuclei, which then undergo a half-life. A certain proportion of K2 will decay, and will undergo β-n decay, producing delayed neutrons.

[0101] When the precursor nuclei reach saturation, the accelerator beam is controlled to stop irradiating the reaction target.

[0102] As the beam continues to irradiate, the precursor nuclei are constantly generated and accumulated, and their number will gradually increase. The saturation state means that under the current experimental conditions, the generation rate and decay rate of the precursor nuclei reach a dynamic balance, and the number no longer increases significantly. To monitor whether the pioneer nuclei are saturated, professional radiation monitoring equipment is generally used to track the radiation characteristics of specific pioneer nuclei. When saturation is reached, continuing to irradiate the beam will not only fail to efficiently generate more useful precursor nuclei, but may also cause problems such as excess energy deposition and equipment overheating, so the beam irradiation should be stopped in time.

[0103] The delayed neutron calibration source is left to stand until the prompt neutrons in the containment device disappear.

[0104] Prompt neutrons are generated synchronously at the moment of nuclear reaction. These neutrons are released immediately at the moment of reaction, and their energy, flux and other characteristics are very different from those of delayed neutrons. If the prompt neutron interference is not eliminated, the detector 3 will mix in the error signal when measuring the delayed neutron count rate, resulting in a huge deviation in the result. The delayed neutron calibration source 10 is left stationary for a period of time, which is to use the characteristics of the short half-life and rapid decay of the prompt neutrons to allow them to decay naturally during this stationary period, creating a pure environment for the subsequent accurate detection of delayed neutrons.

[0105] Strict control of the precursor nucleus generation, saturation and prompt neutron elimination links allows Detector 3 to focus on measuring delayed neutrons, avoiding interference from mixed signals, and obtaining accurate and reliable data such as the delayed neutron count rate and energy spectrum.

[0106] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A delayed neutron calibration source, characterized in that: include: A shielding part, wherein a first accommodating cavity extending in a height direction and a first channel communicating with the first accommodating cavity are formed inside the shielding part, and the shielding part is used for shielding radiation; A containing device, the containing device is arranged in the first containing cavity and corresponds to the first channel, and the containing device is used to contain a reaction target; A detector, at least part of which is disposed in the first accommodating cavity, and the detector is used to detect a neutron count rate in the first accommodating cavity; An accelerator, wherein a beam emitted by the accelerator can pass through the first channel and irradiate the reaction target.

2. The delayed neutron calibration source according to claim 1, characterized in that: The shielding part is provided with a placing platform in the first accommodating cavity, the accommodating device is arranged on the placing platform, and the center line of the first channel passes through the centroid of the accommodating device.

3. The delayed neutron calibration source according to claim 1, characterized in that: The shielding portion includes a second channel, the second channel is communicated with the first accommodating cavity, the detector can extend into the first accommodating cavity through the second channel, wherein a center line of the second channel intersects a center line of the first channel; and / or, The centerline of the second channel coincides with the centerline of the containing device.

4. The delayed neutron calibration source according to claim 3, characterized in that: The shielding portion includes a first shielding member and a second shielding member arranged along a height direction of the shielding portion, and the first shielding member and the second shielding member define the first accommodating cavity inside.

5. The delayed neutron calibration source according to claim 4, characterized in that: The first channel is arranged on the first shielding member, and the first channel penetrates the inner wall of the first accommodating cavity along a first direction. The second channel is arranged on the second shielding member, and the second shielding member penetrates the inner wall of the first accommodating cavity along a height direction of the shielding portion, wherein the first direction intersects with the height direction.

6. The delayed neutron calibration source according to claim 4, characterized in that: The first shielding component includes a first subcomponent and a second subcomponent. One side of the first subcomponent is snap-fitted with the second subcomponent, and the other side of the first subcomponent is snap-fitted with the second shielding component. The first subcomponent and the second subcomponent at least form part of the first accommodating cavity.

7. The delayed neutron calibration source according to claim 1, characterized in that: The accommodating device is provided with a penetration hole, and the detector can penetrate the penetration hole.

8. The delayed neutron calibration source according to any one of claims 1 to 7, characterized in that: The wall thickness of the first accommodating cavity is not less than 80 mm.

9. A method for activating a delayed neutron calibration source, applied to a delayed neutron calibration source, characterized in that: The delayed neutron calibration source comprises a shielding part, a containing device, a detector and an accelerator; a first containing cavity and a first channel communicating with the first containing cavity are formed inside the shielding part, the first containing cavity is used to contain a reaction target, and the shielding part can shield radiation; the containing device is arranged in the first containing cavity, and is used to contain the reaction target; at least part of the detector is arranged in the first containing cavity, and the detector is used to detect the neutron count rate in the first containing cavity; The beam emitted by the accelerator can pass through the first channel to irradiate the reaction target; The activation method of the delayed neutron calibration source comprises: Filling the reaction target in the containing device; Setting the beam intensity of the accelerator to a first beam intensity; Controlling the beam of the accelerator to irradiate the reaction target; The detector is controlled to detect delayed neutrons to obtain a first counting rate.

10. The method for activating a delayed neutron calibration source according to claim 9, characterized in that: The step of controlling the beam of the accelerator to irradiate the reaction target comprises: Controlling the beam of the accelerator to irradiate the reaction target to generate precursor nuclei; When the precursor nucleus reaches a saturation state, controlling the beam of the accelerator to stop irradiating the reaction target; The delayed neutron calibration source is left to stand until the prompt neutrons in the containing device disappear.

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