Combined detector for online sipping device

Abstract

The invention particularly relates to a combined detector for an online sipping device. The combined detector comprises a beta-ray detector, a gamma-ray detector and a signal processing system, the beta ray detector adopts a plastic scintillation chamber with a high beta / gamma response ratio; the gamma ray detector adopts a scintillation crystal; the signal processing system is configured to perform beta-gamma coincidence measurement on output signals of the beta-ray detector and the gamma-ray detector; the plastic scintillation chamber is adjacent to the scintillation crystal space, and the detection areas of the plastic scintillation chamber and the scintillation crystal space are at least partially overlapped so as to jointly detect the detected gas flowing through the plastic scintillation chamber. The invention further relates to a nuclear fuel assembly damage detection method which adopts the combined detector. According to the invention, comprehensive detection of beta and gamma rays of radioactive inert gas is realized, and efficient and sensitive measurement of beta rays in large-volume radioactive inert gas is realized, so that the efficiency and accuracy of gamma-beta coincidence measurement are improved.

Description

A combined detector for online sucking devices Technical Field

[0001] This invention relates to the field of nuclear radiation detection technology, specifically to a combined detector for an online sipping device and a method for detecting damage to nuclear fuel assemblies using the combined detector, applicable to nuclear fuel assembly damage detection, such as... 133 Xe, 85 Online monitoring of radioactive inert gases such as Kr. Background Technology

[0002] Online slurping devices are an important component of fuel handling and storage systems (PMC) used to qualitatively inspect the damage to nuclear fuel assemblies after irradiation. Currently, most online slurping devices in China only use gas. 133 Xe emitted gamma rays as the measurement target. However, when fuel components break down, the main fission products in the coolant water... 133 Xe not only emits gamma rays but also beta rays; simultaneously, other fission products such as 85 Kr also emits beta rays. Therefore, existing devices measure only one object, affecting the accuracy of the judgment.

[0003] like 133 Xe, 85 Beta ray detectors for radioactive inert gases such as Kr typically employ passivated ion-implanted planar silicon (PIPS) semiconductor detectors or scintillation detectors composed of a plastic sheet and a photoelectric conversion device, with a detection solid angle usually of 2π. Because beta rays have a short range in air, generally less than 15 cm, these traditional detectors struggle to achieve sensitive measurements of beta rays in large-volume gas samples, resulting in limited detection efficiency.

[0004] In addition, to improve detection specificity, such as 133 Xe, 85 β-ray detectors for radioactive inert gases such as Kr need to be used together with γ-ray detectors for γ-β coincidence measurements. 133 Xe emits both gamma rays and beta rays simultaneously, with the beta rays emitted uniformly in space at a solid angle of 4π. However, using a beta detector with a solid angle of 2π significantly reduces the detection efficiency of beta rays, thus directly affecting the overall efficiency and reliability of gamma-beta coincidence measurements. Summary of the Invention

[0005] One of the objectives of this invention is to solve the existing problems such as 133 Xe, 85 To address the limitation of single-object measurement in beta and gamma ray detectors for radioactive inert gases such as Kr, this paper proposes a combined detector and nuclear fuel assembly damage detection method for online sipping devices, enabling the detection of damage to nuclear fuel assemblies such as Kr. 133Xe, 85 Comprehensive detection of beta and gamma rays from radioactive inert gases such as Kr.

[0006] The second objective of this invention is to solve the existing problems such as 133 Xe, 85 To address the problem of small solid angles and difficulty in sensitively measuring beta rays in large volumes of radioactive inert gases such as Kr, this paper proposes a combined detector and nuclear fuel assembly damage detection method for online sipping devices. This method utilizes a 4π solid angle plastic scintillation chamber and extends its array to achieve the detection of beta rays in large volumes of gases such as Kr. 133 Xe, 85 This enables efficient and sensitive measurement of beta rays in large-volume radioactive inert gases such as Kr, thereby improving the efficiency and accuracy of γ-β coincidence measurements.

[0007] To achieve the above objectives, in one aspect, the present invention provides a combined detector for an online inhalation device, comprising a beta-ray detector, a gamma-ray detector, and a signal processing system; the beta-ray detector includes a plastic scintillation chamber, a light guide, a first photoelectric conversion device, and a first signal processing circuit; the plastic scintillation chamber is a cubic or cylindrical cavity formed by splicing together thin plastic scintillation sheets, and has an internal channel for the gas to be measured to flow through; the first photoelectric conversion device is optically coupled to the plastic scintillation chamber via the light guide; the first signal processing circuit is electrically connected to both the first photoelectric conversion device and the signal processing system; the gamma-ray detector includes a scintillation crystal, a second photoelectric conversion device, and a second signal processing circuit; the second photoelectric conversion device is optically coupled to the scintillation crystal; the second signal processing circuit is electrically connected to both the second photoelectric conversion device and the signal processing system; the signal processing system is configured to perform beta-gamma coincidence measurement on the output signals of the beta-ray detector and the gamma-ray detector; the plastic scintillation chamber and the scintillation crystal are arranged spatially adjacent to each other, and their detection areas at least partially overlap, so as to jointly detect the gas to be measured flowing through the plastic scintillation chamber.

[0008] As one possible implementation, the interior of the plastic scintillation chamber is a cubic or cylindrical cavity divided into at least one detection unit. The body diagonal length of each detection unit is the estimated range of the monoenergetic electrons of the beta rays of the gas being measured in air. Each detection unit has only one inlet and one outlet and is connected to the gas path of only one adjacent detection unit, so that the gas being measured can flow sequentially through each detection unit.

[0009] As one possible implementation, the plastic scintillation chamber is composed of multiple stacked or arrayed detection units, with air passages connected between adjacent detection units.

[0010] As one possible implementation, the interior of the plastic scintillation chamber is a cubic chamber, which is divided into eight cubic sub-chambers of equal volume by three plastic scintillation sheets that intersect each other perpendicularly. Each sub-chamber constitutes a detection unit; the gas paths of each detection unit are connected in series.

[0011] As one possible implementation, the plastic scintillator sheet is made of a plastic scintillator with a β / γ response ratio greater than 180 and less than 1000, and has a thickness of 0.5 mm to 1 mm.

[0012] As one possible approach, the outer surface of the plastic scintillator is coated with a TiO2 reflective layer, except for the light window.

[0013] As one possible implementation, the gamma-ray detector further includes a metal shielding layer disposed between the scintillation crystal and the plastic scintillation chamber; the scintillation crystal is NaI or Ti.

[0014] As one possible implementation, the metal shielding layer is an aluminum shell with a thickness of 1 mm to 2 mm.

[0015] As one possible implementation, the first signal processing circuit and / or the second signal processing circuit includes a preamplifier.

[0016] As one feasible method, the gas being measured is 133 Xe or 85 Kr.

[0017] To achieve the above objectives, the present invention provides a method for detecting damage to nuclear fuel assemblies, employing the aforementioned combined detector, comprising the following steps: allowing the gas to be tested to flow through the plastic scintillation chamber; detecting β rays emitted by radioactive nuclides in the gas to be tested using the β-ray detector, generating a β-ray signal; detecting γ rays emitted by radioactive nuclides in the gas to be tested using the γ-ray detector, generating a γ-ray signal; the output signals of the β-ray detector and the γ-ray detector are sent to a signal processing system for β-γ coincidence measurement, and the presence and activity of a specific radioactive inert gas nuclide in the gas to be tested are determined based on the β-γ coincidence measurement results.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The combined detector for online sipping devices and the nuclear fuel assembly damage detection method of the present invention, by integrating a beta-ray detector and a gamma-ray detector, can simultaneously measure beta-rays and gamma-rays released by radioactive inert gases, overcoming the deficiency of the prior art in measuring only one object, and making the damage judgment more comprehensive and accurate.

[0019] The present invention relates to a combined detector for an online sipping device and a method for detecting damage to nuclear fuel assemblies. It employs a plastic scintillation chamber as a β detector, achieving 4π solid angle detection of β rays. Through range constraint design of the detector unit size and multi-unit array expansion, it overcomes the technical bottleneck of sensitive measurement of large-volume gas samples, significantly improving the overall detection efficiency of β rays. For radioactive gases of the same sensitive volume, compared to existing β-ray detectors using a 2π solid angle, the β-ray detector of the present invention achieves a 3-5 times improvement in β detection efficiency and a 3-5 times improvement in γ-β coincidence detection efficiency.

[0020] The combined detector and nuclear fuel assembly damage detection method for online sipping devices of the present invention significantly increases the coincidence count rate of γ-β coincidence measurement due to the substantial improvement in β detection efficiency, effectively improving the signal-to-noise ratio and detection sensitivity of coincidence measurement and reducing the probability of false positives.

[0021] The combined detector and nuclear fuel assembly damage detection method for online sipping devices of the present invention employs a plastic scintillator with a high β / γ response ratio and combines it with pulse amplitude discrimination, which can effectively suppress the interference of γ-ray background on β measurement; at the same time, the thin metal shielding layer between the γ detector and the plastic scintillator also avoids the influence of β rays on γ energy spectrum measurement. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the working principle of an embodiment of the combined detector for an online sipping device of the present invention; Figure 2 is a schematic diagram of the gas flow direction in the plastic scintillation chamber of the present invention. Detailed Implementation

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0026] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of description and simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0027] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0029] As shown in Figure 1, the present invention provides an embodiment of a combined detector for an online sucking device, comprising a beta-ray detector, a gamma-ray detector, and a signal processing system.

[0030] In this embodiment, the beta-ray detector includes a plastic scintillation chamber, an acrylic light guide, a first photoelectric conversion device, and a first preamplifier. It performs 4π solid angle detection of beta rays in the measured gas and suppresses the gamma-ray background through pulse amplitude discrimination. The plastic scintillation chamber is a cubic or cylindrical cavity constructed from assembled plastic scintillators, with its inner wall directly contacting the measured gas. It has internal channels for the measured gas to flow through. The interior of the plastic scintillation chamber is a cubic or cylindrical cavity configured as one or more detection units. The body diagonal length of each detection unit is the estimated range of the monoenergetic electrons of the beta rays in the measured gas in air, ensuring effective detection of beta rays. The estimated range of the monoenergetic electrons of the beta rays in the measured gas in air is estimated based on the energy of the beta rays. To achieve sensitive detection of beta rays in large-volume measured gases, the plastic scintillation chamber is composed of multiple stacked or arrayed detection units, resulting in overall beta-ray detection sensitivity. The volume breaks through the β-ray range limitation; adjacent detection units share a single-layer plastic scintillation sheet; each detection unit has only one air inlet and one air outlet, and is only connected to the gas path of the adjacent detection unit, so that the gas to be measured can flow sequentially through each detection unit; the β / γ response ratio of the plastic scintillation sheet is greater than 180 and less than 1000, the thickness is 0.5mm-1mm, for example 0.7mm, and the surface is polished, detailed parameters are shown in Table 1; the outer surface of the plastic scintillation chamber is provided with a light window on one side; the outer surface of the plastic scintillation chamber, except for the light window, is coated with a TiO2 reflective layer and is wrapped and supported by a metal shell such as an aluminum alloy shell; one end of the organic glass light guide is optically coupled to the light window of the plastic scintillation chamber, and the other end is optically coupled to the photosensitive surface of the photoelectric conversion device; the electrical signal output terminal of the first photoelectric conversion device is electrically connected to the input terminal of the first preamplifier, and the output terminal of the first preamplifier is electrically connected to the signal processing system.

[0031] Table 1 Detailed parameters of plastic scintillating film To measure beta rays under strong gamma-ray interference radiation, a high β / γ response ratio is required to facilitate measurement in a mixed field of beta and gamma rays. Gamma-ray interference signals can be removed through simple pulse amplitude discrimination. This invention employs a plastic scintillation chamber, constructed from thin plastic scintillation sheets with a high β / γ response ratio, to perform 4π solid angle detection of beta rays in the measured gas.

[0032] The beta rays of the gas being measured are ionized and excited by a plastic scintillation sheet in a plastic scintillation chamber to generate photon signals. The photon signals are converted into current pulses after passing through an optical window and a light guide into the first photoelectric conversion device. The magnitude of the current pulses is proportional to the total number of photons incident on the beta ray detector. The current pulses are converted into low-impedance voltage signals, i.e. beta ray signals, by the first preamplifier. The beta ray signals are then transmitted through a cable to the signal processing system for amplification, discrimination, and measurement.

[0033] In this embodiment, the gamma-ray detector includes a NaI crystal, a second photoelectric conversion device, and a second preamplifier. It measures the gamma rays of the gas being tested and simultaneously performs gamma-β coincidence measurements with a β-ray detector. The NaI crystal is a high-performance inorganic scintillation crystal with excellent resolution for gamma rays, capable of detecting both energy and intensity. It exhibits outstanding luminescence performance, high energy resolution, no self-absorption in the emission band, and is easily grown into large-size crystals. The light-transmitting window of the NaI crystal is directly photocoupled to the photosensitive surface of the second photoelectric conversion device. The electrical signal output terminal of the second photoelectric conversion device is electrically connected to the input terminal of the second preamplifier, and the output terminal of the second preamplifier is electrically connected to the signal processing system. The NaI crystal is mounted close to the outer wall of one end face of the plastic scintillation chamber, with a thin metal shielding layer between them to shield against interference from β-rays on the gamma-ray measurement while allowing gamma rays to pass through without affecting the gamma-ray measurement.

[0034] After the gamma rays of the gas being tested penetrate the plastic scintillation chamber, they deposit energy in the NaI crystal to generate scintillation light. The scintillation light is then processed by a second photoelectric conversion device and a second preamplifier to convert it into an analyzable voltage pulse signal, which is a gamma ray signal. The gamma ray signal is transmitted through a cable to a signal processing system for amplification, discrimination, counting, and energy spectrum measurement of the gamma ray signal.

[0035] In this embodiment, the plastic scintillation chamber and the NaI crystal are arranged adjacent to each other in space, and their detection areas at least partially overlap, so as to jointly detect the gas to be measured flowing through the plastic scintillation chamber; the output signals of the β-ray detector and the γ-ray detector are sent to the signal processing system for β-γ coincidence measurement.

[0036] In this embodiment, as an example, when the gas being measured is 133Xe, the maximum energy Emax of the β-rays of 133Xe is 346.3 keV, and the average energy Eave is 100.6 keV. Using the average energy of the β-rays of 133Xe, the range of a monoenergetic electron in air is conservatively estimated to be 10.5 cm. This range is used as a constraint in the design of the plastic scintillation chamber, and the body diagonal length of the detection unit of the plastic scintillation chamber is set to the length of this range. In addition, the size of the gamma-ray detector is also considered in the design of the detection unit of the plastic scintillation chamber. When the NaI crystal size of the gamma-ray detector is 3 inches, the volume of the detection unit is 140.8 mL. The plastic scintillation chamber is a cubic cavity assembled from six plastic scintillation sheets. The interior of the plastic scintillation chamber is a cubic cavity with a length of 8 cm, a width of 8 cm, and a height of 17.6 cm, which is divided into eight equal-volume cubic sub-cavities by three perpendicularly intersecting plastic scintillation sheets. Each sub-cavity serves as... Each detection unit has only one inlet and one outlet, and is connected to the gas path of only one adjacent sub-chamber. The gas paths of each detection unit are connected in series. The gas to be measured enters through the inlet, flows sequentially through each detection unit, and is discharged from the cubic chamber through the outlet. As shown in Figure 2, the gas to be measured enters from the bottom detection unit A1, then clockwise through detection units B1, C1, and D1, then upwards through detection unit D2, then counterclockwise through detection units A2, B2, and C2, and finally is discharged from the cubic chamber through detection unit C2. The NaI crystal is installed close to the outer wall of the 8cm×8cm end face of the plastic scintillation chamber. A 1mm-2mm thick aluminum shell is provided between the NaI crystal and the plastic scintillation chamber as a thin metal shielding layer.

[0037] In other embodiments, NaI crystals may be replaced with TI crystals.

[0038] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A combined detector for an online sucking device, characterized in that, The system comprises a beta-ray detector, a gamma-ray detector, and a signal processing system. The beta-ray detector includes a plastic scintillation chamber, a light guide, a first photoelectric conversion device, and a first signal processing circuit. The plastic scintillation chamber is a cavity constructed from assembled plastic scintillation sheets, with an internal channel for the gas to be measured. The first photoelectric conversion device is optically coupled to the plastic scintillation chamber via the light guide. The first signal processing circuit is electrically connected to both the first photoelectric conversion device and the signal processing system. The gamma-ray detector includes a scintillation crystal, a second photoelectric conversion device, and a second signal processing circuit. The second photoelectric conversion device is optically coupled to the scintillation crystal. The second signal processing circuit is electrically connected to both the second photoelectric conversion device and the signal processing system. The plastic scintillation chamber and the scintillation crystal are spatially adjacent, and their detection areas at least partially overlap. The combined detector is configured to perform beta-gamma coincidence measurements on the output signals of the beta-ray detector and the gamma-ray detector.

2. The combined detector according to claim 1, characterized in that, The interior of the plastic scintillation chamber is a cavity divided into at least one detection unit. The body diagonal length of each detection unit is the estimated range of the monoenergetic electrons of the beta rays of the gas being measured in air. Each detection unit has only one inlet and one outlet and is connected to the gas path of only one adjacent detection unit, so that the gas being measured can flow sequentially through each detection unit.

3. The combined detector according to claim 2, characterized in that, The plastic scintillation chamber is composed of multiple stacked or arrayed detection units, with air passages connected between adjacent detection units.

4. The combined detector according to claim 3, characterized in that, The interior of the plastic scintillation chamber is a cubic chamber, which is divided into eight equal cubic sub-chambers by three plastic scintillation sheets that intersect each other perpendicularly. Each sub-chamber constitutes a detection unit; the gas paths of each detection unit are connected in series.

5. The combined detector according to any one of claims 1-4, characterized in that, The plastic scintillator sheet is made of a plastic scintillator with a β / γ response ratio greater than 180 and less than 1000, and has a thickness of 0.5 mm to 1 mm.

6. The combined detector according to claim 1, characterized in that, The outer surface of the plastic scintillator is coated with a reflective layer, except for the light window.

7. The combined detector according to claim 1, characterized in that, The gamma-ray detector also includes a metal shielding layer disposed between the scintillation crystal and the plastic scintillation chamber; the scintillation crystal is NaI or Ti.

8. The combined detector according to claim 7, characterized in that, The metal shielding layer is an aluminum shell with a thickness of 1 mm to 2 mm.

9. The combined detector according to claim 1, characterized in that, The first signal processing circuit and / or the second signal processing circuit include a preamplifier.

10. A method for detecting damage to nuclear fuel assemblies, characterized in that, The combined detector as described in any one of claims 1-9 includes the following steps: allowing the gas to be tested to flow through the plastic scintillation chamber; detecting β rays emitted by a radioactive nuclide in the gas to be tested using the β-ray detector to generate a β-ray signal; detecting γ rays emitted by a radioactive nuclide in the gas to be tested using the γ-ray detector to generate a γ-ray signal; the output signals of the β-ray detector and the γ-ray detector are sent to a signal processing system for β-γ coincidence measurement, and the presence and activity of a specific radioactive inert gas nuclide in the gas to be tested are determined based on the β-γ coincidence measurement result.

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