Reactor neutron flux fission ionization chamber

Abstract

The embodiment of the present disclosure 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, a gas-filled tube, a gas-filled end head, an insulating connector, a high-voltage connector, a signal transmission assembly and an electronic system. The fission coating is on the wall of the anode tube and is used for responding to neutrons. The anode inner tube is located in the cathode shell, and the core end of the high-voltage connector is welded to the inner wall of the anode inner tube. The insulating connector is in the cathode shell and separates the anode inner tube from the cathode shell. The gas-filled end head and the gas-filled tube are welded to the cathode shell. The signal transmission assembly is connected to the electronic system. The electronic system comprises a high-voltage module, a total 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 embodiment improves the effective sensitive area of the detector, thereby greatly improving the sensitivity.

Description

Technical Field

[0001] The embodiments disclosed herein relate to the field of nuclear power technology, specifically to a reactor neutron flux detection fission ionization chamber. Background Technology

[0002] Activating the neutron source increases the neutron flux level when the reactor is in a deep subcritical state, ensuring that the neutron flux at the reactor's nuclear monitoring instruments reaches its effective monitoring range, avoiding monitoring blind spots, and thus enabling real-time monitoring of the reactor flux and criticality safety levels. 252 CF-based primary neutron source components are commonly used for startup neutron sources. Currently, there are no mature primary neutron source suppliers in China, and only a few countries in the world have the capability for commercial production. 252 Cf's capabilities, thus forming a basis for... 252 The monopoly of the Cf supply market. If the primary neutron source assembly could be eliminated during reactor design, i.e., passive start-up could be implemented, freeing my country from dependence on imported products in key technologies and preventing the independent development and export of nuclear power from being controlled by others. Passive start-up relies solely on the neutrons spontaneously released by the fuel as the neutron source for reactor startup. Its source strength is relatively weak, therefore, during reactor loading and when the pre-criticality level is high, external detectors have a certain monitoring "blind zone," making it impossible to obtain effective counts.

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

[0004] Currently, the known fission ionization chambers used for neutron flux measurement in reactors generally have an outer diameter of 2.5 mm or 5–10 mm and a relatively short length, typically less than 100 mm. The sensitivity of the aforementioned patented products is generally lower than 0.01 cps / nv (high-enriched U-235 thermal neutron spectrum) and 0.001 cps / nv (U-238 fast spectrum). It is a generally accepted fact in the field that, with similar outer diameters, the longer the uranium-plated region, the higher the sensitivity. A major factor limiting sensitivity is the inability to plating uranium onto longer anode surfaces, for the following reasons:

[0005] I. Large-size electroplating equipment is difficult to obtain. Uranium plating equipment generally uses electroplating tanks of special sizes. If the size is too large, it is impossible to guarantee the uniformity of solution concentration during the electroplating process. In addition, in order to ensure the uniformity and flatness of the coating, hoisting and control devices are generally required. If the length of the uranium plating anode is too long, the entire equipment will be too large and difficult to obtain.

[0006] II. The stability and uniformity of the uranium plating 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 are no large fluctuations. However, a longer anode and a larger electroplating tank will 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 should not fall off after being subjected to vibration, friction, high temperature and other problems. However, the longer the anode surface, the greater the difficulty in controlling the stability process. Summary of the Invention

[0007] The summary portion of this disclosure is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description portion. This summary portion is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

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

[0009] In a first aspect, some embodiments of this disclosure provide a reactor neutron flux detection fission ionization chamber, which includes: a fission coating, an inner anode tube, a cathode shell, a gas filling pipe, a gas filling end cap, an insulating connector, a high-voltage connector, a signal transmission component, and an electronic system. The fission coating is applied to the anode tube wall for responding to neutrons; the inner anode tube is located inside the cathode shell, and the core wire end of the high-voltage connector is welded to the inner wall of the inner anode tube. The insulating connector is located inside the cathode shell, isolating the inner anode tube 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 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 above-mentioned 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 2.0 μm and 5.6 μm.

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

[0012] Optionally, the cathode housing is made of Inconel 600 material with a thickness of 0.5 mm to 1 mm.

[0013] Optionally, the above-mentioned anodic fission coating adopts a segmented uranium plating process, with a total length of approximately 500mm to 1200mm.

[0014] Optionally, the anode inner liner is installed in a segmented manner, with adjacent segments fixed by high-insulation alumina ceramic and connected by electrode wires.

[0015] Optionally, the pressure of the gas filling the cathode shell is 1 atm to 4.5 atm.

[0016] Optionally, the above-mentioned electronic system has three operating modes: pulse mode under low throughput: a charge-sensitive preamplifier is used to collect charges and convert them into voltage pulse signals, and a discrimination circuit is used to shape and count them; Campbell mode under medium throughput: AC coupling is used to remove DC signals, sampling and performing mean square value processing to obtain the mean square voltage, and then the count rate is calculated; current mode under high throughput: the current signal is amplified and filtered, then AD converted, and then the count rate is calculated.

[0017] The embodiments disclosed above have the following beneficial effects: By employing segmented uranium plating and segmented installation, an anode inner tube with a sensitive area length exceeding 1000 mm can be obtained, resulting in a maximum sensitivity improvement of over 10 times, significantly enhancing measurement sensitivity. The cathode shell material is Inconel 600, with a shell thickness of 0.5 mm to 1 mm, and is connected to the ground wire of the signal transmission component. The fission coating uses a highly enriched 235U material with a thickness between 2.0 and 5.6 μm, and the uranium plating method is either single-layer inner cylinder outer surface plating or double-sided uranium plating. The ionization chamber charging gas is pure Ar gas with a pressure of atm to 4 atm. The distance between the ionization chamber cathode and anode is 1.5 mm to 2.5 mm. The electronic system has three operating modes: a pulse mode at low throughput, corresponding to the source range; a mean square voltage mode at higher throughput, also called Campbell mode, corresponding to the intermediate range; and a current mode at high throughput, corresponding to the power range. The uranium-plated anode inner tube adopts segmented uranium plating and is installed with insulation and 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. Attached Figure Description

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

[0019] Figure 1 This is a schematic diagram of a design structure for a reactor neutron flux detection fission ionization chamber disclosed herein;

[0020] Figure 2 This is a design diagram of an electronics system for a reactor neutron flux detection fission ionization chamber disclosed herein;

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

[0022] Figure 4 This is a schematic diagram of the charge-sensitive preamplifier principle in the counting mode of the reactor neutron flux detection fission ionization chamber disclosed herein. Detailed Implementation

[0023] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0024] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

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

[0026] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

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

[0028] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a schematic diagram of a design structure for a reactor neutron flux detection fission ionization chamber. The reactor neutron flux detection fission ionization chamber disclosed herein includes: a fission coating, an inner anode tube, a cathode shell, a gas filling pipe, a gas filling end cap, insulating connectors, a high-voltage connector, signal transmission components, and an electronic system. Figure 1In the example design structure diagram, the reactor neutron flux detection fission ionization chamber includes: a gas filling pipe protective cover 1, a gas filling pipe 2, a gas filling end cap 3, a gas filling end insulating component 4, a cathode outer tube 5, an anode inner tube 6, an anode inter-section insulating sleeve 7, an anode inner tube 8, an electrode wire 9, a high-voltage end insulating component 10, a sealing flange 11, a high-voltage connector 12, and a high-voltage end sleeve 13.

[0030] It should be noted that the insulating connectors include: the gas-filled end insulating component 4 and the high-voltage end insulating component 10. The signal transmission components and electronic system are part of the built-in signal processing system; therefore, their specific design location is not limited. The fission coating is a layer applied to the anode tube wall; therefore, in Figure 1 Not shown in the image.

[0031] In some embodiments, the fission coating is applied to the anode tube wall for neutron response; the anode inner liner is located inside the cathode outer shell, and the high-voltage connector core wire end is welded to the inner wall of the anode inner liner. An insulating connector is located inside the cathode outer shell, isolating the anode inner liner from the cathode outer shell; the gas filling end cap and gas filling pipe are welded and connected to the cathode outer 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. The high-voltage module can refer to a high-voltage power supply module. The current-sensitive preamplifier can refer to a current-sensitive preamplifier module. For example, the current-sensitive preamplifier module can be a current-sensitive preamplifier. The charge-sensitive preamplifier can refer to a charge-sensitive preamplifier module. For example, the current-sensitive preamplifier module can be a charge-sensitive preamplifier. The signal conditioning module can refer to an isolation transmitter module. The AD conversion module can refer to an AD analog-to-digital conversion module. The amplitude discrimination module can refer to a pulse amplitude discriminator. The signal processing module can refer to a signal processor.

[0032] The fission coating material mentioned above is uranium trioxide (U3O8), wherein, 235 The enrichment level of Uranium-235 is 0-30% (as high as possible when conditions permit). 238 The enrichment level of U is 70-99.28%, and high enrichment levels are used. 235 U ensures high detection sensitivity within a relatively small detector size. It's important to note that the uranium plating thickness affects detector sensitivity; different thicknesses result in varying energy deposition of alpha particles and fission fragments within the plating, leading to different energy deposition in the emitted gas and thus affecting sensitivity. Based on actual detector operating requirements, this invention selects a uranium plating thickness between 2.0 μm and 5.6 μm to ensure good sensitivity in the ionization chamber.

[0033] The distance between the cathode and anode affects the energy deposition of fission fragments in charge collection during ionization chamber operation. Generally, energy deposition increases with increasing electrode spacing, eventually reaching a stable level; however, increasing the electrode spacing reduces the electric field strength and electron collection efficiency. Based on the actual operating requirements of the ionization chamber, the electrode spacing is designed to be 1.5mm to 2.5mm.

[0034] Gas pressure primarily affects the energy deposition of particles in the gas. As gas pressure increases, the energy deposition of fission fragments tends to increase, making fission fragments easier to distinguish from alpha particles. In high-temperature environments, the gas expands, leading to higher internal pressures within the detector, which poses a challenge to the detector's structural strength. Based on the actual operating environment of the ionization chamber, the gas pressure ranges from 1 atm to 4.5 atm (standard atmospheric pressure).

[0035] Considering the complex measurement environment of practical applications, including high temperature, high pressure, and significant gamma radiation, the outer shell material is required to possess high comprehensive performance, exhibiting excellent high-temperature resistance, corrosion resistance, and radiation resistance, as well as good stress resistance, corrosion cracking resistance, and mechanical properties at high temperatures. This invention uses Inconel 600 shell material to meet the requirements of the working environment. While meeting the process requirements, the detector shell is made as thin as possible to avoid sensitivity loss due to neutron scattering. This invention uses a shell thickness of 0.5mm to 1mm.

[0036] The size of the detector primarily affects its overall sensitivity. Keeping the sensitivity constant (0.1 cps / nv), the detector's outer diameter and length are inversely proportional. Based on the requirements of the ionization chamber's operating environment and considering actual manufacturing processes, a detector outer diameter of 6mm–10mm and a length greater than 50cm are selected.

[0037] Figure 2 For electronic system design diagrams. Figure 2 In the example, the electronic system may include: a high-voltage module, a detector, a master 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. The detector can be a device for observing and recording particles, an indispensable piece of 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 may 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 communicatively connected to the detector, which is connected to the main control switch. The main control switch is connected to both the current-sensitive preamplifier and the charge-sensitive preamplifier. The current-sensitive preamplifier is communicatively connected to both the amplitude discrimination module and the signal conditioning module. The signal conditioning module is communicatively connected to one AD conversion module. Both AD conversion modules and the amplitude discrimination module are communicatively connected to the pulse counting / FPGA / mean square voltage / current acquisition module. The current-sensitive preamplifier is communicatively connected to another AD conversion module. The pulse counting / FPGA / mean square voltage / current acquisition module is communicatively connected to the host computer.

[0039] The electronic system mainly involves the different operating modes of the fission ionization chamber and the switching between modes. The fission ionization chamber has three operating modes: ① Low-flux pulse mode: A charge-sensitive preamplifier collects the charge and converts it into a voltage pulse signal, which is then shaped and counted using a discrimination circuit; ② Medium-flux Campbell mode: AC coupling eliminates the DC signal, samples and performs mean square (MSS) value processing to obtain the MSS voltage, and then calculates the count rate; ③ High-flux current mode: The current signal is amplified, filtered, and then converted using an analog-to-digital converter (AD converter) before the count rate is calculated. Different electronic circuits were designed for each operating mode, and these circuits were integrated into a system using an FPGA and a computer. The system switches between different modes according to different flux levels, enabling the fission ionization chamber to monitor neutron flux across the entire range.

[0040] It should be noted that when switching between counting mode and current mode, it is necessary to ensure that the current mode is powered by a negative high voltage. Figure 3 The current is output from the ground electrode, resulting in good shielding during transmission; the counting mode is powered by positive high voltage. Figure 4 The outer casing is grounded, and a pulse current signal is output from the high-voltage electrode through capacitive coupling.

[0041] In summary, this invention comprises a fission coating, an inner anode tube, a cathode shell, a gas filling pipe, a gas filling end cap, insulating connectors, a high-voltage connector, signal transmission components, and an electronic system. It is adaptable to the measurement environment within a reactor and possesses high sensitivity.

[0042] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. A high-temperature resistant reactor neutron flux detection fission ionization chamber, characterized in that, The reactor neutron flux detection fission ionization chamber includes: a fission coating, an inner anode tube, a cathode shell, a gas filling pipe, a gas filling end cap, insulating connectors, a high-voltage connector, signal transmission components, and an electronic system. The fission coating is applied to the inner wall of the anode tube to respond to neutrons; The inner tube of the anode is located inside the outer shell of the cathode, and the core wire end of the high-voltage connector is welded to the inner wall of the inner tube of the anode. The insulating connector is located inside the cathode housing, isolating the anode inner tube from the cathode housing; The inflation end cap and inflation pipe are welded together and connected to the cathode shell; The signal transmission components are 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; The fission coating is applied using a segmented uranium plating process; The inner tube of the anode is installed in a segmented manner, with adjacent segments fixed by high-insulation alumina ceramic and connected by electrode wires; The electronic system has three operating modes: Pulse mode under low throughput: A charge-sensitive preamplifier is used to collect charge and convert it into a voltage pulse signal, which is then shaped and counted using a discrimination circuit; Campbell's mode at medium throughput: AC coupling eliminates DC signal, samples and performs mean square value processing to obtain mean square voltage, and then calculates the count rate; High-throughput current mode: The current signal is amplified, filtered, and then converted by an analog-to-digital converter before the count rate is calculated; For switching between counting mode and current mode: it is necessary to ensure that the current mode is powered by negative high voltage and outputs current from the ground electrode; the counting mode is powered by positive high voltage, with the casing as ground, and outputs pulse current signal from the high voltage electrode through capacitor coupling.

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 level of U is 0-30%. 238 The enrichment of U is 70-99.28%, and the thickness of its uranium plating is between 2.0 μm and 5.6 μm.

3. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that, The distance between the inner tube of the anode and the outer shell of the cathode 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 Inconel 600 material with a thickness of 0.5mm to 1mm.

5. The reactor neutron flux detection fission ionization chamber according to claim 1, characterized in that, The pressure of the gas filling the cathode shell is 1 atm to 4.5 atm.

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