Reactor core detector based on liquid emitter material and processing method thereof

Abstract

The invention discloses a reactor core detector based on a liquid emitter material and a processing method thereof, the reactor core detector comprises a probe, a transmission cable and a reducing sleeve, the probe comprises a collection body, an insulator and an emitter, the emitter comprises a pressure container and a liquid emitter, the liquid emitter is sealed in the pressure container, and the transmission cable is connected with the collection body. The liquid emitter is made of a metal material which is in a solid state at normal temperature but melts at high temperature in the reactor core, or a metal material which is in a liquid state at normal temperature. According to the invention, the selection range of the emitter material is successfully expanded, and the limitation that the previous emitter material can only use a solid metal material is changed, so that the self-powered detector can adopt a liquid emitter, the selection categories of the emitter material are increased, and the adaptability and flexibility of the self-powered detector in practical application are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of radiation detection, and in particular relates to a core detector based on liquid emitter material for radiation particle detection and a processing method thereof. Background Art

[0002] In order to ensure the safe and effective operation of nuclear reactors, monitoring work in the core naturally becomes an extremely important part. Self-powered detectors are a special type of nuclear detector that is widely used in nuclear reactor core detection work. They can directly characterize the state of nuclear reactions in the reactor. Self-powered detectors have the advantages of high temperature resistance, radiation resistance, small size, simple structure, and no need for external power supply. They are very suitable for core detection work and are one of the indispensable equipment for reactors. They are widely used in various cores such as test reactors, pressurized water reactors, high temperature gas-cooled reactors, and fourth-generation reactors.

[0003] The structure of a traditional self-powered detector includes a front-end probe, a rear-end transmission cable, and a connecting sleeve between the probe and the cable; the probe part is composed of an emitter, an insulator, and a collector. The emitter of a typical self-powered detector is made of metal materials such as Rh and V, the insulator is made of Al2O3 and MgO, and the collector can use materials such as Inconel600 and stainless steel.

[0004] The working principle of the self-powered detector is based on the interaction between the emitter material and neutrons. The emitter material will be activated and release electrons under neutron irradiation. These electrons are collected to form a current signal, which is proportional to the injection rate of the incident neutrons. Therefore, the selection of emitter materials is crucial to the performance of the detector. At present, most emitter materials are made of solid metal materials, because solid metal materials are easy to process, store and transport, and have the advantages of low production technology difficulty. Liquid metal materials have relatively low storage and transportation stability, flow leakage and other problems. This results in some liquid metal materials cannot be used as emitter materials in existing self-powered detectors. Summary of the invention

[0005] In view of the problem that it is difficult for existing self-powered detectors to use liquid metal materials as emitter materials, the present invention provides a core detector based on liquid emitter materials and a processing method thereof. The core detector uses liquid metal materials as emitter materials by designing a specific structure, so that liquid metal materials can become candidate materials for self-powered detectors, changing the previous limitation that the emitter materials of self-powered detectors can only use solid metal materials, thereby expanding the available options for emitter materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a core detector based on liquid projectile material, including a probe, a transmission cable, and a reducing sleeve; The probe comprises a collector, an insulator, and an emitter which are coaxially arranged from outside to inside. The emitter comprises a pressure vessel and a liquid emitter. The pressure vessel comprises a pressure vessel body and a pressure vessel sealing cover. The pressure vessel body is a cylindrical structure with one end closed. The pressure vessel sealing cover is a disc-shaped structure. The liquid emitter is filled in the inner cavity of the pressure vessel body. The pressure vessel body and the pressure vessel sealing cover are laser welded into a sealed whole. The insulator comprises an insulator side tube and an insulator bottom powder layer. The insulator side tube is nested in a cylindrical collector with one end closed. The insulator bottom powder layer is laid on the bottom of the collector. The transmission cable comprises a transmission cable shell and a transmission cable core wire, wherein the space between the transmission cable shell and the transmission cable core wire is filled with a transmission cable insulating material, wherein the transmission cable core wire comprises a transmission cable signal core wire and a transmission cable compensation core wire, and the transmission cable signal core wire is connected to a pressure vessel sealing cover by laser welding; The reducer sleeve is a hollow annular structure with different sizes at both ends. The small end of the reducer sleeve is welded to the transmission cable housing, and the large end of the reducer sleeve is welded to the open end of the collector.

[0007] Furthermore, the liquid emitter is made of a metal material that is solid at room temperature but melts at high temperature inside the core or a metal material that is liquid at room temperature.

[0008] Furthermore, the liquid emitter is made of indium (In).

[0009] Furthermore, the liquid emitter indium (In) and the pressure vessel body are assembled in a clearance fit manner.

[0010] Furthermore, the outer diameter of the pressure vessel sealing cover is the same as the outer diameter of the pressure vessel body, and both the pressure vessel body and the pressure vessel sealing cover are made of Inconel600 material.

[0011] Furthermore, the insulator side tube is made of alumina material, the insulator bottom powder layer is made of alumina powder, and the collector is made of Inconel600 material.

[0012] Furthermore, the transmission cable casing, the transmission cable signal core wire, and the transmission cable compensation core wire are all made of Inconel600 material, and the transmission cable insulation material is made of alumina material.

[0013] Furthermore, the reducer sleeve is made of Inconel600 material.

[0014] In a second aspect, the present invention provides a method for processing the above-mentioned core detector based on liquid emitter material, comprising: S1: Put the liquid projectile into the pressure vessel body, place the sealing cover on the top of the pressure vessel body, and connect the sealing cover and the pressure vessel body by laser welding to form a whole, thereby forming the projectile; S2: Evenly spread the aluminum oxide powder on the bottom of the collector and compact it to form an insulator bottom powder layer, then insert the insulator side tube into the collector, and then put the emitter into the insulator side tube; S3: Use laser welding to weld the signal core wire of the transmission cable and the sealing cover, then weld the large end of the reducer sleeve and the collector, and then weld the small end of the reducer sleeve and the transmission cable shell.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are: (1) The core detector based on liquid emitter material provided by the present invention successfully expands the selection range of emitter materials through the design and use of a specific structure, changing the previous limitation that only solid metal materials can be used as emitter materials, so that the self-powered detector can use liquid emitters, increasing the selection categories of emitter materials. The liquid emitter in the present invention can not only use metal materials that are in liquid form at room temperature, but also use metal materials that are in solid form at room temperature but melt at high temperature inside the core, thereby improving the adaptability and flexibility of the self-powered detector in practical applications.

[0016] (2) The present invention uses a pressure vessel to form an overall closed environment, which can not only limit the fluidity of the liquid projectile, but also limit the change in volume of the liquid projectile in the core environment as the temperature increases, thereby avoiding pressure leakage and avoiding the toxicity and reactivity of some liquid projectile materials.

[0017] (3) For metal materials that are solid at room temperature and melt at high temperatures, the solid metal is sealed into the pressure vessel during processing and welded. As the temperature rises, the solid metal material will heat up, melt when the temperature reaches the melting point, and increase in volume. At this time, the pressure vessel needs to provide sufficient pressure resistance to ensure that the pressure generated by the melting of the metal will not leak out. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 is a schematic structural diagram of a core detector based on liquid emitter material in an embodiment of the present invention; Figure 2 yes Figure 1 Schematic diagram of the cross section of the probe; Reference numerals: 1-probe, 2-transmission cable, 3-reducing sleeve; 11-collector, 12-insulator, 13-emitter; 121-insulator side tube, 122-insulator bottom powder layer; 131-pressure vessel, 132-liquid projectile; 1311-pressure vessel body, 1312-pressure vessel sealing cover; 21-transmission cable casing, 22-transmission cable insulation material, 23-transmission cable core wire; 231-transmission cable signal core wire, 232-transmission cable compensation core wire. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1 Please see attached Figure 1-2 As shown, a core detector based on liquid projectile material in this embodiment includes a probe 1, a transmission cable 2, and a reducing sleeve 3.

[0022] Specifically, the probe 1 includes a collector 11, an insulator 12, and an emitter 13 which are coaxially arranged from outside to inside. The emitter 13 includes a pressure vessel 131 and a liquid emitter 132. The pressure vessel 131 includes a pressure vessel body 1311 and a pressure vessel sealing cover 1312. The pressure vessel body 1311 is a cylindrical structure with one end closed, and the pressure vessel sealing cover 1312 is a disc-shaped structure. The liquid emitter 132 is filled in the inner cavity of the pressure vessel body 1311. The pressure vessel body 1311 and the pressure vessel sealing cover 1312 are laser welded into a sealed whole. The insulator 12 includes an insulator side tube 121 and an insulator bottom powder layer 122. The insulator side tube 121 is nested in a In a cylindrical collector 11 with closed ends, an insulating base powder layer 122 is laid on the bottom of the collector 11; the transmission cable 2 includes a transmission cable casing 21 and a transmission cable core wire 23, and a transmission cable insulating material 22 is filled between the transmission cable casing 21 and the transmission cable core wire 23, and the transmission cable core wire 23 is composed of a transmission cable signal core wire 231 and a transmission cable compensation core wire 232, and the transmission cable signal core wire 231 is connected to the pressure vessel sealing cover 1312 by laser welding; the reducing sleeve 3 is a hollow annular structure with different sizes at both ends, the small end of the reducing sleeve 3 is welded to the transmission cable casing 21, and the large end of the reducing sleeve 3 is welded to the open end of the collector 11.

[0023] In this embodiment, the probe 1, the transmission cable 2, and the reducer 3 are welded by laser welding technology to ensure the sealing of the overall structure. The probe 1 is used to detect the radiation signal and output it in the form of current. The transmission cable 2 then transmits the current signal to the electronic system connected at the back end for reading and calculation, thereby realizing online measurement of the radiation in the pile.

[0024] When the core detector is used for nuclear reactor detection, nuclear radiation will hit the signal core of the cable and generate a part of the signal. The superposition of this part of the signal and the signal output by the probe 1 will cause the signal to become larger. Therefore, the present invention uses a double-core cable consisting of a transmission cable signal core 231 and a transmission cable compensation core 232. The transmission cable signal core 231 connected to the probe 1 is used to transmit part of the signal of the probe 1, and the transmission cable compensation core 232 is not connected to the probe 1. When the nuclear radiation hits the transmission cable 2, the same current will be generated on the transmission cable signal core 231 and the transmission cable compensation core 232. By adopting the compensation line differential input structure circuit, this part of the excess current is offset to maximize the noise suppression ratio and interference suppression ratio of the circuit.

[0025] In this embodiment, the liquid emitter 132 is indium (In). Indium is a solid metal at room temperature, and its melting point is 156 degrees Celsius.

[0026] In actual use, the reactor is at a high temperature of 350 degrees Celsius, and the indium material will melt into liquid metal.

[0027] In this embodiment, the outer diameter of the pressure vessel sealing cover 1312 is the same as the outer diameter of the pressure vessel body 1311, and both the pressure vessel body 1311 and the pressure vessel sealing cover 1312 are made of Inconel 600. Since the volume of metal materials will increase when they change from solid to liquid, the pressure bearing capacity and welding stability of the pressure vessel 131 are very high.

[0028] As a preferred embodiment, when the liquid emitter 132 indium (In) is placed in the pressure vessel 131, a clearance fit is formed between the liquid emitter 132 indium (In) and the pressure vessel 131, so that after the indium melts at high temperature, there is space to accommodate its volume change, reducing the requirements for the pressure vessel 131.

[0029] In this embodiment, the insulator side tube 121 is made of 99% pure alumina ceramic tube, the insulator bottom powder layer 122 is made of α-alumina powder, and the collector 11 is made of Inconel600 material; the transmission cable housing 21, the transmission cable signal core wire 231, and the transmission cable compensation core wire 232 are all made of Inconel600 material, and the transmission cable insulation material 22 is made of α-alumina powder.

[0030] The processing method of the core detector based on the liquid emitter 132 material of this embodiment has the following specific steps: S1: Put the liquid emitter 132 into the pressure vessel body 1311, place the sealing cover on the top of the pressure vessel body 1311, and connect the sealing cover and the pressure vessel body 1311 by laser welding to form a whole, thereby forming the emitter 13; S2: evenly spread the aluminum oxide powder on the bottom of the collector 11 and compact it to form an insulator bottom powder layer 122, then insert the insulator side tube 121 into the collector 11, and then put the emitter 13 into the insulator side tube 121; S3: Use laser welding to weld the signal core wire 231 of the transmission cable and the sealing cover, then weld the large end of the reducing sleeve 3 and the collecting body 11, and then weld the small end of the reducing sleeve 3 and the transmission cable housing 21.

[0031] The detection principle of the core detector based on the liquid emitter 132 material of this embodiment: When the core detector based on the liquid emitter 132 material of this embodiment is used for detection in the reactor, radiation particles (neutrons, photons) enter the probe 1, and the radiation particles pass through the collector 11, the insulator side tube 121, the pressure vessel 131, and the liquid emitter 132 material indium (In) undergo a nuclear reaction to generate electrons; the electrons pass through the pressure vessel 131 and the insulator side tube 121, reach the collector 11 and are collected, generating a current signal. The current signal is output through the transmission cable signal core wire 231, and the detection of radiation particles can be realized in conjunction with the back-end electronics system.

[0032] Example 2 Different from the first embodiment, the liquid emitter 132 in this embodiment is made of a metal material that is in liquid form at room temperature.

[0033] Specifically, the liquid emitter in this embodiment is made of any one of mercury (Hg) and gallium (Ga).

[0034] Example 3 Different from the first embodiment, the liquid emitter 132 in this embodiment is made of other metal materials with a melting point of 30-300° C. and melted at the high temperature inside the core.

[0035] Specifically, the liquid emitter in this embodiment adopts any one of tin (Sn), bismuth (Bi), rubidium (Rb), potassium (K), sodium (Na), and lithium (Li).

[0036] Example 4 Different from the first embodiment, the liquid emitter 132 in this embodiment is made of other metal materials having a melting point exceeding 300° C. and melting at the high temperature inside the core.

[0037] Specifically, the liquid emitter in this embodiment uses any one of cadmium (Cd), lead (Pb), zinc (Zn), and antimony (Sb).

[0038] Test Case The most commonly used emitter material in self-powered neutron detectors is rhodium (Rh), and the emitter material used in Example 1 is indium (In). The physical properties of the two materials are shown in the table below.

[0039]

[0040] It can be seen from the above table that: (1) the reaction cross section of indium is larger than that of rhodium, and more neutrons will react with indium under the same neutron field; (2) the half-life of the generated nuclides of indium is shorter than that of rhodium, which means that indium generates signals faster and responds quickly; (3) the β decay energy of the generated nuclides of indium is larger, which means that it can provide a larger current signal, which is beneficial to signal response and output.

[0041] The current sensitivity of two self-powered neutron detectors, Rh-SPND and In-SPND, of the same size is calculated using simulation software. The detector used for modeling is a typical SPND structure with probe dimensions: emitter diameter 0.8mm, insulation layer thickness 0.5mm, collector thickness 0.6mm. The simulation is performed using neutrons with an energy of 0.0253eV, and the results are shown in the following table.

[0042]

[0043] It can be seen from the above table that compared with rhodium materials, indium has a larger output current and higher current sensitivity. Therefore, as an emitter material for detectors, indium has better detection performance than rhodium.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the technical solution and conceptual invention of the present invention should be included in the protection scope of the present invention.

Claims

1. A core detector based on liquid projectile material, characterized in that: Including probe, transmission cable, reducer sleeve; The probe comprises a collector, an insulator, and an emitter which are coaxially arranged from outside to inside. The emitter comprises a pressure vessel and a liquid emitter. The pressure vessel comprises a pressure vessel body and a pressure vessel sealing cover. The pressure vessel body is a cylindrical structure with one end closed. The pressure vessel sealing cover is a disc-shaped structure. The liquid emitter is filled in the inner cavity of the pressure vessel body. The pressure vessel body and the pressure vessel sealing cover are laser welded into a sealed whole. The insulator comprises an insulator side tube and an insulator bottom powder layer. The insulator side tube is nested in a cylindrical collector with one end closed. The insulator bottom powder layer is laid on the bottom of the collector. The transmission cable comprises a transmission cable shell and a transmission cable core wire, wherein the space between the transmission cable shell and the transmission cable core wire is filled with a transmission cable insulating material, wherein the transmission cable core wire comprises a transmission cable signal core wire and a transmission cable compensation core wire, and the transmission cable signal core wire is connected to a pressure vessel sealing cover by laser welding; The reducer sleeve is a hollow annular structure with different sizes at both ends. The small end of the reducer sleeve is welded to the transmission cable housing, and the large end of the reducer sleeve is welded to the open end of the collector.

2. A core detector based on liquid emitter material according to claim 1, characterized in that: The liquid emitter is made of a metal material that is solid at room temperature but melts at high temperature inside the core or a metal material that is liquid at room temperature.

3. A core detector based on liquid emitter material according to claim 2, characterized in that: The liquid emitter uses indium (In).

4. The core detector based on liquid emitter material according to claim 3, characterized in that: The liquid emitter indium (In) is assembled with the pressure vessel body by a clearance fit.

5. The core detector based on liquid emitter material according to claim 1, characterized in that: The outer diameter of the pressure vessel sealing cover is the same as the outer diameter of the pressure vessel body, and both the pressure vessel body and the pressure vessel sealing cover are made of Inconel600 material.

6. The core detector based on liquid emitter material according to claim 1, characterized in that: The insulator side tube is made of alumina material, the insulator bottom powder layer is made of alumina powder, and the collector is made of Inconel600 material.

7. The core detector based on liquid emitter material according to claim 1, characterized in that: The transmission cable shell, the transmission cable signal core wire, and the transmission cable compensation core wire are all made of Inconel600 material, and the transmission cable insulation material is made of alumina material.

8. The core detector based on liquid emitter material according to claim 1, characterized in that: The reducer sleeve is made of Inconel600 material.

9. A method for processing a core detector based on liquid projectile material according to any one of claims 1 to 8, comprising: S1: Put the liquid projectile into the pressure vessel body, place the sealing cover on the top of the pressure vessel body, and connect the sealing cover and the pressure vessel body by laser welding to form a whole, thereby forming the projectile; S2: Spread the aluminum oxide powder evenly on the bottom of the collector and compact it to form an insulator bottom powder layer, then insert the insulator side tube into the collector, and then put the emitter into the insulator side tube; S3: Use laser welding to weld the signal core wire of the transmission cable and the sealing cover, then weld the large end of the reducer sleeve and the collector, and then weld the small end of the reducer sleeve and the transmission cable shell.

Images