Reactor neutron flux detection fission ionization chamber

Abstract

The embodiment of the invention discloses a reactor neutron flux detection fission ionization chamber. The reactor neutron flux detection fission ionization chamber comprises a fission coating, an anode inner tube, a cathode shell, an inflation tube, an inflation end sealing head, an insulation connecting piece, a high-pressure connector, a signal transmission assembly and an electronics system, and the fission coating is arranged on the anode tube wall in a transition mode and used for responding to neutrons; the anode liner is located in the cathode shell, and the core wire end of the high-voltage connector is welded to the inner wall of the anode liner. The insulating connecting piece is arranged in the cathode shell and isolates the anode liner from the cathode shell; the gas charging end sealing head is welded with the gas charging pipe and is connected with the cathode shell; the signal transmission assembly is connected with the electronics system; the electronics system comprises a high-voltage module, a master control switch, a current sensitive pre-amplifier, a charge sensitive pre-amplifier, a signal conditioning module, an AD conversion module, an amplitude discrimination module and a signal processing module. According to the embodiment, the effective sensitive area of the detector is improved, so that the sensitivity is greatly improved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of nuclear power technology, and in particular to a reactor neutron flux detection fission ionization chamber. Background Art

[0002] Starting the neutron source is to increase the neutron flux level when the reactor is in a deep subcritical state, so that the neutron flux at the reactor's nuclear measurement instrument reaches its effective monitoring range, avoiding the occurrence of monitoring blind spots, thereby achieving real-time monitoring of the reactor's flux level and criticality safety level. 252 The primary neutron source assembly composed of Cf is a commonly used start-up neutron source. At present, there is no mature primary neutron source supply source in China, and only a few countries in the world have commercial production. 252 Cf's ability to form 252 Monopoly of the Cf supply market. If the primary neutron source assembly can be eliminated during the reactor design process, that is, passive start-up can be implemented, we can get rid of our dependence on imported products in key technologies and avoid being controlled by others in the independent development and export of my country's nuclear power. Passive start-up relies solely on the neutrons spontaneously released by the fuel as the starting neutron source of the nuclear reactor. Its source strength is relatively weak. Therefore, when the reactor is loaded and the criticality is deep before the criticality, the external detector has a certain range of monitoring "blind spots" and cannot obtain effective counts;

[0003] The operating environment inside the reactor is harsh. Currently, the temperature of a pressurized water reactor can reach over 300°C during operation, requiring the detector to be resistant to high temperatures. The spatial layout inside the reactor is complex, and there are strict requirements on the geometric dimensions of the detector, especially the outer diameter. Under passive start-up conditions, the neutron flux density in the core is low, requiring the detector to have a higher detection sensitivity.

[0004] At present, the fission ionization chambers for neutron flux measurement in known reactors generally have an outer diameter of 2.5mm or 5-10mm, and a relatively short length, generally within 100mm. The sensitivity of the above-mentioned patented products is generally lower than 0.01cps / nv (highly enriched U-235 thermal neutron spectrum) and 0.001cps / nv (U-238 fast spectrum). It is a recognized fact in this field that the longer the uranium plating area is, the higher the sensitivity is when the outer diameter is similar. A major factor restricting the sensitivity is that it is impossible to plate uranium on a longer anode surface for the following reasons:

[0005] 1. Large-sized electroplating equipment is difficult to obtain. Uranium plating equipment generally uses a special-sized electroplating tank. If the size is too large, the uniformity of the solution concentration during the electroplating process cannot be guaranteed; and in order to ensure the uniformity and flatness of the coating, a hoisting device and a control device are generally required. If the length of the uranium plating anode is too long, the entire device will be too large and difficult to obtain.

[0006] Second, the stability and uniformity of the uranium-plated surface cannot be guaranteed. (1) The coating on the anode surface needs to be uniform, that is, the surface thickness difference is small and there is no large fluctuation. Longer anodes and larger electroplating tanks will also make it difficult to control the uniform distribution of solution concentration, resulting in difficulty in controlling the uniformity of the coating. (2) The coating on the anode surface needs to be stable, that is, it will not fall off after being subjected to vibration, friction, high temperature and other problems. The longer the anode surface, the more difficult it is to control the process of stability. Summary of the invention

[0007] The content of this disclosure is used to introduce concepts in a brief form, which will be described in detail in the detailed implementation section below. The content of this disclosure is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

[0008] Some embodiments of the present disclosure propose a reactor neutron flux detection fission ionization chamber to solve one or more of the technical problems mentioned in the above background technology section.

[0009] In the first aspect, some embodiments of the present disclosure provide a reactor neutron flux detection fission ionization chamber, which includes: a fission coating, an anode inner tube, a cathode shell, a gas-filled tube, a gas-filled end cap, an insulating connector, a high-voltage connector, a signal transmission component, and an electronic system, wherein the fission coating is applied to the anode tube wall to respond to neutrons; the anode liner is located in the cathode shell, and the core wire end of the high-voltage connector is welded to the inner wall of the anode liner. The insulating connector is in the cathode shell to isolate the anode liner from the cathode shell; the gas-filled end cap and the gas-filled tube are welded and connected to the cathode shell; the signal transmission component is connected to the electronic system; the electronic system includes: a high-voltage module, a master control switch, a current-sensitive preamplifier, a charge-sensitive preamplifier, a signal conditioning module, an AD conversion module, an amplitude discrimination module, and a signal processing module.

[0010] Optionally, the fission coating material is U3O8, wherein: 235 The enrichment of U is 0-30%, 238 The enrichment of U is 70-99.28%, and the thickness of the uranium plating is between 2.0um and 5.6um.

[0011] Optionally, the distance between the anode inner shell and the cathode outer shell is 1.5 mm-2.5 mm.

[0012] Optionally, the cathode shell is made of Inconel600 with a thickness of 0.5 mm to 1 mm.

[0013] Optionally, the anode fission coating adopts a segmented uranium plating process, with a total length of about 500mm to 1200mm.

[0014] Optionally, the anode liner is installed in sections, and adjacent sections are fixed with high-insulation alumina ceramics and connected with electrode wires.

[0015] Optionally, the pressure of the gas filled in the cathode housing is 1 atm to 4.5 atm.

[0016] Optionally, the above-mentioned electronic system has three working modes: pulse mode under low flux: using a charge-sensitive preamplifier, collecting charges and converting them into voltage pulse signals, using a discrimination circuit to form and count; Campbell mode under medium flux: AC coupling to eliminate DC signals, sampling and performing mean square value processing, obtaining mean square voltage, and then calculating the counting rate; current mode under high flux: amplifying and filtering the current signal, performing AD conversion, and then calculating the counting rate.

[0017] The above-mentioned embodiments of the present disclosure have the following beneficial effects: by adopting segmented uranium plating and segmented installation methods, an anode inner tube with a sensitive area length of more than 1000mm can be obtained, and the design sensitivity can be increased by more than 10 times, which greatly improves the measurement sensitivity. The cathode shell material is Inconel600, the shell thickness is: 0.5mm~1mm, and it is connected to the ground wire of the signal transmission component. The fission coating adopts high-enrichment 235U material, and its thickness is between 2.0 and 5.6um. The uranium plating method is uranium plating on the outer surface of a single-layer inner tube or uranium plating on both sides. The ionization chamber charging gas is pure Ar gas, and its gas pressure is atm~4atm. The distance between the cathode and the anode of the ionization chamber is 1.5mm~2.5mm. The electronic system has three working modes: pulse mode at low flux, corresponding to the source range; mean square voltage mode at higher flux, also called Campbell mode, corresponding to the intermediate range; current mode at high flux, corresponding to the power range. The inner tube of the uranium-plated anode is segmented uranium-plated and installed with insulation isolation. The total length can reach more than 1000mm, which greatly increases the effective sensitive area of ​​the detector and thus greatly improves the sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that components and elements are not necessarily drawn to scale.

[0019] Figure 1 It is a schematic diagram of a design structure of a reactor neutron flux detection fission ionization chamber disclosed in the present invention;

[0020] Figure 2 It is an electronics system design diagram of the reactor neutron flux detection fission ionization chamber disclosed in the present invention;

[0021] Figure 3 It is a schematic diagram of a charge-sensitive preamplifier in a current mode of a reactor neutron flux detection fission ionization chamber disclosed in the present invention;

[0022] Figure 4 It is a schematic diagram of the charge-sensitive preamplifier principle in the counting mode of the reactor neutron flux detection fission ionization chamber disclosed in the present invention. DETAILED DESCRIPTION

[0023] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0024] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

[0025] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0026] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0027] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0028] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0029] Figure 1 The present invention is a schematic diagram of the design structure of a reactor neutron flux detection fission ionization chamber. The reactor neutron flux detection fission ionization chamber disclosed in the present invention comprises: a fission coating, an anode inner tube, a cathode shell, an air filling tube, an air filling end cap, an insulating connector, a high-voltage connector, a signal transmission component, and an electronics system. Figure 1In the design structure diagram of the example, the reactor neutron flux detection fission ionization chamber includes: a gas-filled tube protective cover 1, a gas-filled tube 2, a gas-filled end cap 3, a gas-filled end insulating member 4, a cathode outer tube 5, an anode inner tube 6, an anode internode insulating sleeve 7, an anode inner tube 8, an electrode wire 9, a high-voltage end insulating member 10, a sealing flange 11, a high-voltage joint 12, and a high-voltage end sleeve 13.

[0030] It should be noted that the insulating connector includes: an insulator 4 at the gas-filled end and an insulator 10 at the high-voltage end. The signal transmission components and the electronic system belong to the built-in signal processing system, so the specific design position is not limited. The fission coating is a layer on the anode tube wall, so Figure 1 Not shown.

[0031] In some embodiments, the fission coating is applied to the anode tube wall to respond to neutrons; the anode liner is located in the cathode shell, and the high-voltage connector core wire end is welded to the inner wall of the anode liner. The insulating connector is in the cathode shell to isolate the anode liner from the cathode shell; the gas-filled end cap and the gas-filled tube are welded and connected to the cathode shell; the signal transmission component is connected to the electronics system; the electronics system includes: a high-voltage module, a master control switch, a current-sensitive preamplifier, a charge-sensitive preamplifier, a signal conditioning module, an AD conversion module, an amplitude discrimination module, and a signal processing module. The high-voltage module may refer to a high-voltage power supply module. The current-sensitive preamplifier may refer to a current-sensitive preamplifier module. For example, the current-sensitive preamplifier module may be a current-sensitive preamplifier. The charge-sensitive preamplifier may refer to a charge-sensitive preamplifier module. For example, the current-sensitive preamplifier module may be a charge-sensitive preamplifier. The signal conditioning module may refer to an isolation transmitter module. The AD conversion module may refer to an AD analog-to-digital conversion module. The amplitude discrimination module may refer to a pulse amplitude discriminator. The signal processing module may refer to a signal processor.

[0032] The fission coating material is uranium octoxide U3O8, wherein: 235 The enrichment of U-235 is 0-30% (as high as possible under conditions), 238 The enrichment of U is 70-99.28%. 235 U can ensure a higher detection sensitivity at a smaller detector size. It should be noted that the thickness of the uranium plating will affect the sensitivity of the detector. Different thicknesses will result in different energy deposition of alpha particles and fission fragments in the plating, resulting in different energy deposition in the gas after emission, which in turn affects the sensitivity. According to the actual working requirements of the detector, the present invention selects a uranium plating thickness between 2.0um and 5.6um, which can ensure that the ionization chamber has good sensitivity.

[0033] The distance between the cathode and the anode affects the energy deposition of fission fragments and charge collection when the ionization chamber is working. Generally speaking, energy deposition increases with the increase of the electrode distance and eventually reaches stability; if the electrode distance increases, the electric field strength decreases and the electron collection efficiency decreases. According to the actual working requirements of the ionization chamber, the electrode distance is designed to be 1.5mm to 2.5mm.

[0034] Gas pressure mainly affects the energy deposition of particles in the gas. As gas pressure increases, the energy deposition of fission fragments tends to increase, making it easier to distinguish between fission fragments and alpha particles. In a high temperature environment, the gas will expand and the pressure inside the detector will be higher, which is also a challenge to the structural strength of the detector. According to the actual working environment of the ionization chamber, the gas pressure is 1atm~4.5atm (standard atmospheric pressure).

[0035] Considering the actual application environment, the measurement environment is relatively complex, with high temperature, high pressure and a large amount of gamma radiation. The shell material is required to have high comprehensive performance, good high temperature resistance, corrosion resistance, and radiation resistance, and good stress resistance, corrosion cracking performance and mechanical properties at high temperatures. The present invention uses Inconel600 shell material to meet the requirements of the working environment. When the process is met, the detector shell is made as thin as possible to avoid the loss of sensitivity due to neutron scattering. The shell thickness of the present invention is 0.5mm to 1mm.

[0036] The size of the detector mainly affects the overall sensitivity of the detector. When the sensitivity (0.1cps / nv) remains unchanged, the outer diameter and length of the detector are in a certain inverse proportional relationship. According to the needs of the working environment of the ionization chamber and considering the actual processing requirements, the outer diameter of the detector is selected to be 6mm to 10mm, and the length of the detector is greater than 50cm.

[0037] Figure 2 Design diagrams for electronic systems. Figure 2 In the example, the electronics system may include: a high-voltage module, a detector, a master control switch, a current-sensitive preamplifier, a charge-sensitive preamplifier, a signal conditioning module, two AD conversion modules, an amplitude discrimination module, a pulse counting / FPGA / mean square voltage / current acquisition module, and a host computer. Among them, the detector can be a device for observing and recording particles, which is an indispensable equipment in nuclear physics and particle physics experimental research. Detectors can be divided into two categories: counters and track detectors. The pulse counting / FPGA / mean square voltage / current acquisition module can include a pulse counting module, an FPGA (Field Programmable Gate Array), a voltage acquisition module, and a current acquisition module.

[0038] It should be noted that the high-voltage module is connected to the detector in communication, and the detector is connected to the master control switch; the master control switch is connected to the current sensitive preamplifier and the charge sensitive preamplifier respectively; the current sensitive preamplifier is connected to the amplitude discrimination module and the signal conditioning module respectively; the signal conditioning module is connected to an AD conversion module in communication. Both AD conversion modules and the amplitude discrimination module are connected to the pulse counting / FPGA / mean square voltage / current acquisition module in communication. The current sensitive preamplifier is connected to another AD conversion module in communication. The pulse counting / FPGA / mean square voltage / current acquisition module is connected to the host computer in communication.

[0039] The electronics system mainly involves different working modes of the fission chamber and the conversion between modes. The fission chamber has three working modes: ① Pulse mode under low flux: using charge sensitive preamplifier, collecting charges and converting them into voltage pulse signals, using discrimination circuits to form and count; ② Campbell mode under medium flux: AC coupling removes DC signals, samples and performs mean square value processing, obtains mean square voltage, and then calculates the counting rate; ③ Current mode under high flux: amplifies and filters the current signal, then performs AD conversion, and then calculates the counting rate. Different electronic circuits are designed for different working modes, and different circuits are integrated into a system through FPGA and computer, and different modes are switched according to different fluxes, so that the fission chamber can complete the monitoring function of neutron flux in the entire range.

[0040] It should be noted that for the switch between counting mode and current mode: it is necessary to ensure that the current mode is powered by negative high voltage ( Figure 3 ), output current from the ground electrode, the transmission shielding effect is better; the counting mode is positive high voltage power supply ( Figure 4 ), the outer shell is grounded, and a pulse current signal is output from the high voltage electrode through capacitive coupling.

[0041] In summary, the present invention includes a fission coating, an anode inner tube, a cathode shell, a gas-filled tube, a gas-filled end cap, an insulating connector, a high-voltage connector, a signal transmission component, and an electronic system. It can adapt to the measurement environment in a reactor and has a high sensitivity.

[0042] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A high temperature resistant reactor neutron flux detection fission ionization chamber, characterized in that: The reactor neutron flux detection fission ionization chamber comprises: a fission coating, an anode inner tube, a cathode shell, a gas-filled tube, a gas-filled end cap, an insulating connector, a high-voltage connector, a signal transmission component, and an electronics system, wherein: The fission coating is applied on the anode tube wall to respond to neutrons; The anode inner shell is located in the cathode outer shell, and the core wire end of the high-voltage joint is welded to the inner wall of the anode inner shell. The insulating connector is in the cathode shell to isolate the anode inner shell from the cathode shell; The gas filling end cap and the gas filling pipe are welded and connected to the cathode shell; The signal transmission components are connected to the electronics system; The electronics system includes: high voltage module, master control switch, current sensitive preamplifier, charge sensitive preamplifier, signal conditioning module, AD conversion module, amplitude discrimination module and signal processing module.

2. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The fission coating material is U3O8, wherein: 235 The enrichment of U is 0-30%, 238 The enrichment of U is 70-99.28%, and the thickness of the uranium plating is between 2.0um and 5.6um.

3. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The distance between the anode inner shell and the cathode outer shell is 1.5mm-2.5mm.

4. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The cathode shell is made of Inconel600 with a thickness of 0.5 mm to 1 mm.

5. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The anode fission coating adopts a segmented uranium plating process, and the total length is about 500mm to 1200mm.

6. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The anode liner is installed in sections, and adjacent sections are fixed with high-insulation alumina ceramics and connected with electrode wires.

7. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The pressure of the gas filled in the cathode housing is 1 atm to 4.5 atm.

8. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that: The electronics system has three operating modes: Pulse mode under low flux: use charge-sensitive preamplifier to collect charge and convert it into voltage pulse signal, and use discrimination circuit to shape and count; Campbell mode at medium flux: AC coupling removes DC signals, samples and performs RMS processing, obtains RMS voltage, and then calculates the count rate; Current mode under high flux: the current signal is amplified and filtered, then AD converted and the count rate is calculated.

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