Semiconductor detector for gamma nuclide monitoring and monitoring device

Abstract

The invention discloses a semiconductor detector used for gamma nuclide monitoring and a monitoring device. The semiconductor detector comprises a detection element and a signal processing module used for reading and processing a detection signal of the detection element. The detection element comprises a plurality of cadmium zinc telluride crystals which are arranged in an array mode; each tellurium-zinc-cadmium crystal adopts a pixel electrode structure, and unipolar charge sensitivity can be realized by a pixel electrode reading method. According to the semiconductor detector for gamma nuclide monitoring, the tellurium-zinc-cadmium crystals with high energy resolution are adopted, the energy resolution of the semiconductor detector is further improved through array type combination of the pixel electrodes and the tellurium-zinc-cadmium crystals, gamma nuclides in radioactive liquid effluents can be analyzed on line, and the accuracy of gamma nuclide monitoring is improved. And the monitoring requirement on the liquid effluent is met.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear effluent monitoring, and in particular to a semiconductor detector and a monitoring device for γ nuclide monitoring. Background Art

[0002] The effluents from nuclear power plants are divided into liquid effluents and gaseous effluents. At present, nuclear power plants use two methods, online alarm monitoring and laboratory analysis, to monitor liquid effluents. Online alarm monitoring generally only measures the total radioactivity of liquid effluents, provides information for alarm and closing certain valves, and is generally used for early warning, with a very limited role. The laboratory analysis method analyzes the liquid effluent samples in the effluent laboratory after collection to achieve the quantification of the concentration of radionuclides and is used to statistically calculate the emissions of nuclear power plants. The sampling and analysis of liquid effluents involve relatively complex and lengthy pretreatment processes, causing a small amount of radiation exposure to monitoring personnel, and the construction cost of the effluent laboratory is high.

[0003] The existing online monitoring system for liquid effluents in nuclear power plants uses scintillation detectors, which have low energy resolution, can only measure the total radioactivity of liquid effluents, do not have the ability to analyze nuclides, and play a limited role. The specific nuclide analysis still needs to be carried out manually in the laboratory after traditional sampling. The offline measurement sampling process is cumbersome and time-consuming, so the analysis results lack representativeness for the current discharged liquid effluents. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an improved semiconductor detector for γ nuclide monitoring and a monitoring device for γ nuclide monitoring.

[0005] The technical solution adopted by the present invention to solve its technical problems is: to provide a semiconductor detector for γ nuclide monitoring, including a detection element and a signal processing module for reading and processing the detection signal of the detection element; the detection element includes a plurality of cadmium zinc telluride crystals arranged in an array; each cadmium zinc telluride crystal adopts a pixel electrode structure and can achieve unipolar charge sensitivity by means of pixel electrode reading.

[0006] In one embodiment, each cadmium zinc telluride crystal is divided into a plurality of volume elements arranged in three-dimensional space, and by calibrating and correcting the charge collection efficiency of each volume element, the difference in charge collection efficiency is eliminated, and the energy resolution of the semiconductor detector is improved.

[0007] In one embodiment, the signal processing module includes an integrated circuit board having a first surface and a second surface relative to each other, a plurality of circuit modules arranged on the first surface of the integrated circuit board, and a digital processing circuit board, a communication circuit board, a high-voltage interface circuit board and a power management circuit board arranged in sequence on the second surface of the integrated circuit board; each of the cadmium zinc telluride crystals is connected to a corresponding one of the circuit modules through a substrate; each of the circuit modules includes an ASIC circuit board, a high-voltage module circuit board for providing bias, and a power supply board, which are sequentially stacked and connected between the substrate and the integrated board.

[0008] In one embodiment, the semiconductor detector further comprises a housing; the detection element and the signal processing module are installed in the housing, and the detection element faces and is close to an inner wall of the housing in the housing.

[0009] In one embodiment, the semiconductor detector further includes a heat dissipation mechanism installed in the housing.

[0010] In one embodiment, the heat dissipation mechanism includes a heat dissipation component and / or a heat dissipation fan.

[0011] The present invention also provides a monitoring device for monitoring gamma nuclides, comprising any of the semiconductor detectors described above.

[0012] In one embodiment, the monitoring device further comprises a liquid water tank and a shielding box for the liquid to be tested to pass through, and the liquid water tank is arranged in the shielding box;

[0013] The liquid water tank is provided with a positioning groove for accommodating the semiconductor detector, and the positioning groove is isolated from the internal chamber of the liquid water tank; the side wall of the liquid water tank is also provided with at least one water inlet connected to the internal chamber for injecting and / or discharging the liquid to be tested.

[0014] In one embodiment, the shielding box is provided with a water pipe port connected to the water port for externally receiving the liquid to be tested, delivering the liquid to be tested into the liquid tank or discharging the liquid to be tested in the liquid tank.

[0015] In one embodiment, the shielding box is a multi-layer structure, including a copper layer, a lead layer and a stainless steel layer from the inside to the outside.

[0016] In one embodiment, the shielding box comprises a shielding box body having an opening and a shielding box cover; the shielding box cover is used to fit on the opening of the shielding box body to close the opening.

[0017] Advantages of the present invention: A cadmium zinc telluride crystal with high energy resolution is adopted, and the energy resolution of the semiconductor detector is further improved through pixel electrodes and an array combination of multiple cadmium zinc telluride crystals, so as to perform on-line analysis of γ nuclides in radioactive liquid effluents and meet the monitoring requirements for liquid effluents. Description of the Drawings

[0018] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0019] Figure 1 is a longitudinal sectional structural schematic diagram of a monitoring device according to an embodiment of the present invention;

[0020] Figure 2 is a structural schematic diagram of a semiconductor detector according to an embodiment of the present invention;

[0021] Figure 3 is Figure 2 a sectional structural schematic diagram of the semiconductor detector shown;

[0022] Figure 4 is a connection schematic diagram of a detection element and a signal processing module in a semiconductor detector according to an embodiment of the present invention;

[0023] Figure 5 is a pixel electrode structural schematic diagram of a cadmium zinc telluride crystal in a semiconductor detector according to an embodiment of the present invention. Detailed Embodiments

[0024] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0025] As Figure 1 shown, a monitoring device for γ nuclide monitoring according to an embodiment of the present invention includes a semiconductor detector 100 for monitoring γ nuclides in nuclear power liquid effluents, and also includes a liquid water tank 200 and a shielding box 300.

[0026] The liquid water tank 200 is used for positioning the semiconductor detector 100 thereon and for the liquid to be measured (i.e., nuclear power liquid effluents) to pass through, and the semiconductor detector 100 monitors the γ nuclides in the liquid to be measured. The shielding box 300 serves as a shielding layer, and the liquid water tank 200 and the semiconductor detector 100 are arranged inside the shielding box 300 to shield radiation and electromagnetic interference through the shielding box 300.

[0027] Among them, the liquid water tank 200 is made of a non-metal, such as polyethylene. The liquid water tank 200 is preferably a closed water tank. The internal chamber of the liquid water tank 200 is used to receive the liquid to be measured. At least one water inlet 201 is provided on the side wall of the liquid water tank 200 for injecting and / or discharging the liquid to be measured. A positioning groove 202 that is isolated from the internal chamber of the liquid water tank 200 is also provided on the liquid water tank 200, and the positioning groove 202 is used to accommodate the semiconductor detector 100.

[0028] In one embodiment, the liquid water tank 200 has a columnar structure, such as a cylindrical body or a polygonal columnar body. The positioning groove 202 is formed by inwardly recessing the top surface of the liquid water tank 200, and the shape of the positioning groove 202 is preferably adapted to the outer peripheral shape of the semiconductor detector 100.

[0029] In one embodiment, as Figure 1 shown, the liquid water tank 200 is provided with two water inlets 201, which are respectively located on different side walls of the liquid water tank 200, such as two opposite side walls. One water inlet 201 serves as an inlet for introducing the liquid to be measured; the other water inlet 201 serves as an outlet for discharging the liquid to be measured.

[0030] It can be understood that when only one water inlet 201 is provided on the liquid water tank 200, this water inlet 201 can be used as an inlet or an outlet.

[0031] The shielding box 300 serves as the shielding outer layer of the monitoring device and encloses the liquid water tank 200 and the semiconductor detector 100 therein. The shape of the shielding box 300 can be, but is not limited to, a polygon, a circular cylinder, a polyhedron, etc., with the overall size being larger than that of the liquid water tank 200.

[0032] Corresponding to the inflow and outflow of the liquid to be measured, the shielding box 300 is provided with a water pipe port 301 communicating with the water inlet 201 for receiving the liquid to be measured outside, sending the liquid to be measured into the liquid water tank 200, or for discharging the liquid to be measured in the liquid water tank 200 outward.

[0033] In one embodiment, as Figure 1 shown, corresponding to the liquid water tank 200 having two water inlets 201, the shielding box 300 is provided with two water pipe ports 301, and the two water pipe ports 301 are respectively connected to the two water inlets 201 in a corresponding manner. When introducing the liquid to be measured, the pipeline for transporting the liquid to be measured can enter the shielding box 300 through one water pipe port 301 and be connected to one water inlet 201 corresponding to this water pipe port 301; the other water pipe port 301 is used for the discharge pipeline to enter the shielding box 300 and be connected to the other water inlet 201 corresponding to this water pipe port 301.

[0034] Further, the shielding box 300 is a multi-layer structure, including a copper layer, a lead layer, and a stainless steel layer from the inside out. Among them, the copper layer is used to shield electromagnetic interference, preferably oxygen-free copper; the lead layer is used to shield environmental radiation, and aged lead can be preferably used.

[0035] To facilitate the taking and placing of the liquid water tank 200 and the semiconductor detector 100, the shielding box 300 adopts an openable and closable structure. As an option, the shielding box 300 includes a shielding box body 310 with an opening and a shielding box cover 320 for covering the opening. The shielding box cover 320 is adaptively arranged with the opening and can be connected to the shielding box body 310 in at least one way such as clamping or connection by fasteners to close the opening.

[0036] As Figures 1-4 shown, the semiconductor detector 100 includes a detection element 10 and a signal processing module 20 for reading and processing the detection signal of the detection element 10. The semiconductor detector 100 also includes a housing 30, and the detection element 10 and the signal processing module 20 are installed in the housing 30.

[0037] Among them, the detection element 10 includes a plurality of cadmium zinc telluride crystals 11 arranged in an array. Each cadmium zinc telluride crystal 11 includes pixel electrodes arranged in an array, so that the cadmium zinc telluride crystal 11 forms a pixel electrode structure and can realize unipolar charge sensitivity by the method of pixel electrode reading. The number of cadmium zinc telluride crystals 11 is preferably 4 - 6. Refer to Figure 5 , which shows a detection element 10 of an embodiment, which includes four arranged cadmium zinc telluride crystals 11, and each cadmium zinc telluride crystal 11 includes pixel electrodes 110 arranged in 11×11.

[0038] Further, each cadmium zinc telluride crystal 11 is divided into a plurality of volume elements arranged in three-dimensional space, and by calibrating and correcting the charge collection efficiency of each volume element, the charge collection efficiency differences caused by carrier capture, material inhomogeneity, etc. are eliminated, and the energy resolution of the semiconductor detector is improved.

[0039] Refer to Figure 4 , in an embodiment, the signal processing module 20 includes a plurality of circuit modules, an integrated circuit board 21, a digital processing circuit board 22, a communication circuit board 23, a high-voltage interface circuit board 24, and a power management circuit board 25. The integrated circuit board 21 has opposite first and second surfaces. A plurality of circuit modules are arranged on the first surface of the integrated circuit board 21 and are connected to the integrated circuit board 21; the digital processing circuit board 22, the communication circuit board 23, the high-voltage interface circuit board 24, and the power management circuit board 25 are arranged on the side where the second surface of the integrated circuit board 21 is located.

[0040] Specifically, the number of circuit modules is correspondingly set with the number of cadmium zinc telluride crystals 11, and one cadmium zinc telluride crystal 11 is connected to one circuit module. As Figure 4As shown, each cadmium zinc telluride crystal 11 is respectively connected to a corresponding circuit module through a substrate (such as a flip-chip substrate) 12, which facilitates plugging and unplugging.

[0041] Each circuit module may further include an ASIC circuit board 211, a high-voltage module circuit board 212, and a power supply board 213 that are sequentially stacked and connected between the substrate 12 and the integrated circuit board 21. Among them, the ASIC circuit board 211 is mainly composed of an FPGA and an ASIC; the high-voltage module circuit board 212 provides a bias voltage for the semiconductor detector; the power supply board 213 is an ADC and LDO power supply board, which mainly provides each low voltage required by the circuit module and realizes high-speed digital acquisition of the ADC.

[0042] The integrated circuit board 21 aggregates and processes the signals of all cadmium zinc telluride crystals 11, and then sends them to the digital processing circuit board 22 for processing. In an embodiment, the power consumption of each cadmium zinc telluride crystal 11 is approximately 0.24 A / 3 V, and the entire signal processing module 20 has 4 cadmium zinc telluride crystals 11, and its total power consumption is approximately 1.15 A / 3 V.

[0043] The digital processing circuit board 22 is connected to the second surface of the integrated circuit board 21, and is mainly composed of an FPGA, which corrects the signals and calculates the DOI. The communication circuit board 23 is connected to the digital processing circuit board 22 and communicates with the host computer for transmitting data and various instructions. The high-voltage interface circuit board 24 is connected to the communication circuit board 23, and the power management circuit board 25 is connected to the side of the high-voltage interface circuit board 24 facing away from the communication circuit board 23; the high-voltage interface circuit board 24 is used for filtering the high voltage and providing ~1200 V high voltage for the detection element 10 through a connector; the power management circuit board 25 is used for processing and managing the input external power supply.

[0044] On the side of the communication circuit board 23 facing away from the integrated circuit board 21, there may be a network port 26 for external connection, including but not limited to an RJ45 network port. The high-voltage interface circuit board 24 and the power management circuit board 25 may be provided with notches to provide a space for the network port 26, so that the network port 26 is exposed outside the power management circuit board 25 facing away from the high-voltage interface circuit board 24, which is convenient for connection and use.

[0045] In an embodiment, the signal processing module 20 uses a KHR chip, which is used for processing (amplifying and timing) and reading out the signals (including the anode, cathode, and anode-gate) of the pixelated detection element. The XC7VX485T-2FFG1761I of Xilinx (Xilinx Semiconductor) is selected to implement functions such as signal conditioning, timing control, analog-to-digital conversion, and data transmission of the KHR chip module.

[0046] Another example is Figures 1-3As shown, in one embodiment, the detection element 10 faces and is close to an inner wall of the housing 30 within the housing 30. The housing 30 has opposite first and second ends, and the first end of the detection element 10 inside is the detection end. Inside the detection end of the housing 30, a metal structure can be provided around the detection element 10, which not only facilitates the positioning and installation of the detection element 10, but also prevents the detection element 10 from being damaged during installation, transportation, and use, improving the reliability and service life of the semiconductor detector 100.

[0047] On the liquid water tank 200, the semiconductor detector 100 is received in the positioning groove 202 with the detection end facing the bottom surface of the positioning groove 202. On the second end of the housing 30 or on the side wall of the housing 30, an interface connected to the network port 26 is further provided, and this interface is used for connecting an external wire.

[0048] Furthermore, to solve the huge heat generated by the signal processing module 20 when the semiconductor detector 100 is working, the semiconductor detector 100 may further include a heat dissipation mechanism, and the heat dissipation mechanism is installed inside the housing 30 to achieve heat dissipation of the semiconductor detector 100. The heat dissipation mechanism includes a heat dissipation component 40 and / or a heat dissipation fan 50; the heat dissipation component 40 can be composed of a plurality of heat sinks or is a radiator with heat dissipation fins on the outer surface. The heat dissipation fan 50 can accelerate the heat exchange between the signal processing module 20 and the external air to achieve rapid heat dissipation.

[0049] In Figure 3 In the shown embodiment, the heat dissipation mechanism includes a heat dissipation component 40 and a heat dissipation fan 50. The heat dissipation component 40 is arranged in the housing 30 around the detection element 10, and the heat dissipation fan 50 is arranged inside one end of the housing 30 far from the detection element 10 (i.e., inside the second end of the housing 30). Corresponding to the heat dissipation fan 50, an air outlet 51 is provided on the second end of the housing 30.

[0050] On the second end of the housing 30, at least one functional interface is further provided. The functional interfaces are respectively used for connecting the signal processing module 20 and the heat dissipation fan 50, etc., and are used for external connectors to be plugged in to supply power to the signal processing module 20 and the heat dissipation fan 50 and realize signal transmission, etc.

[0051] When the monitoring device for γ nuclide monitoring of the present invention is in use, the nuclear power liquid effluent is sent into the liquid water tank 200 through the shielding box 300, and the semiconductor detector 100 on the liquid water tank 200 monitors the nuclides in the liquid effluent.

[0052] Next, the detection performance of the semiconductor detector of the present invention is verified with a standard source.

[0053] 1. Energy resolution and angular response

[0054] Measurement conditions: 137The Cs standard point source is 5.0 cm away from the surface of the semiconductor detector and is placed directly in front of the semiconductor detector, 60° to the left in front, and 60° to the right in front, respectively, with a measurement time of 900 s.

[0055] The measurement system for 137 The energy resolutions of the 661.7 keV gamma rays of Cs are 0.92%, 0.96%, and 0.93% respectively.

[0056] 2. Energy response range

[0057] Measurement conditions: 137 Cs, 232 The Th radioactive sources are placed 5.0 cm directly in front of the semiconductor detector.

[0058] When the gain is 80 mV / fC, the 32 keV gamma ray peak of Cs is visible in the energy spectrum, and there are counts at 30 keV; 137 When the gain is 20 mV / fC, the 2615 keV gamma ray peak of Th is visible in the energy spectrum, and there are counts at 3.0 MeV.

[0059] When the gain is 20 mV / fC, the 2615 keV gamma ray peak of Th is visible in the energy spectrum, and there are counts at 3.0 MeV. 232 When the gain is 20 mV / fC, the 2615 keV gamma ray peak of Th is visible in the energy spectrum, and there are counts at 3.0 MeV.

[0060] 3. Full absorption peak detection efficiency

[0061] Measurement conditions: The semiconductor detector is placed in a 1.656 L Marinelli beaker 137 Cs, 152 in the EU mixed solution standard source. The results are shown in Table 1 below.

[0062] Table 1

[0063]

[0064]

[0065] 4. 137 Cs volume source detection limit

[0066] Measurement conditions: The semiconductor detector is placed in a lead chamber to measure the background, and the measurement time is 3600 s. Calculate the detection limit (95% confidence level) of the measurement system for the 1.656 L Marinelli beaker solution sample 137 of Cs. The results are shown in Table 2 below.

[0067] Table 2

[0068] Radionuclide Energy keV Lower limit of specific activity detection Bq / kg <![CDATA 137 Cs]]> 661.66 32

[0069] 5. Volume source activity

[0070] Measurement conditions: The semiconductor detector is placed in a 1.656 L Marinelli beaker 137Inside the Cs standard solution source, the measurement time was 600 s. The results are shown in Table 3 below.

[0071] Table 3

[0072]

[0073] Compared with the existing online monitoring system for liquid effluents and the effluent laboratory device in nuclear power plants, the present invention uses a cadmium zinc telluride crystal with high energy resolution, and further improves the energy resolution of the semiconductor detector through pixel electrodes, an array combination of multiple cadmium zinc telluride crystals, and charge collection efficiency calibration, so as to perform online analysis on radioactive liquid effluents. Different from the existing online monitoring system for liquid effluents in nuclear power plants, the present invention can perform nuclide analysis on liquid effluents and meet the monitoring requirements of regulatory authorities for liquid effluents.

[0074] For the effluent laboratory, the monitoring device of the present invention is small in overall volume and can be placed at the effluent discharge point of the nuclear power plant. The results output in real time are representative of the currently discharged liquid effluents.

[0075] The above are only embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or equivalent process transformation made using the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A semiconductor detector for gamma nuclide monitoring, characterized in that: It includes a detection element and a signal processing module for reading and processing the detection signal of the detection element; the detection element includes a plurality of cadmium zinc telluride crystals arranged in an array; each of the cadmium zinc telluride crystals adopts a pixel electrode structure and can realize unipolar charge sensitivity by a pixel electrode readout method.

2. The semiconductor detector according to claim 1, characterized in that: Each of the cadmium zinc telluride crystals is divided into a plurality of volume elements arranged in a three-dimensional space, and the charge collection efficiency of each volume element is calibrated and corrected to eliminate the difference in charge collection efficiency and improve the energy resolution of the semiconductor detector.

3. The semiconductor detector according to claim 1, characterized in that: The signal processing module comprises an integrated circuit board having a first surface and a second surface opposite to each other, a plurality of circuit modules arranged on the first surface of the integrated circuit board, a digital processing circuit board, a communication circuit board, a high-voltage interface circuit board and a power management circuit board arranged in sequence on the second surface of the integrated circuit board; each of the cadmium zinc telluride crystals is connected to a corresponding one of the circuit modules through a substrate; Each of the circuit modules comprises an ASIC circuit board, a high voltage module circuit board for providing bias voltage, and a power supply board which are sequentially stacked and connected between the substrate and the integrated board.

4. The semiconductor detector according to any one of claims 1 to 3, characterized in that: The semiconductor detector further comprises a shell; the detection element and the signal processing module are installed in the shell, and the detection element faces and is close to an inner wall of the shell in the shell.

5. The semiconductor detector according to claim 4, characterized in that: The semiconductor detector also includes a heat dissipation mechanism installed in the housing; The heat dissipation mechanism includes a heat dissipation component and / or a heat dissipation fan.

6. A monitoring device for gamma nuclide monitoring, characterized in that: A semiconductor detector comprising any one of claims 1 to 5.

7. The monitoring device according to claim 6, characterized in that: The monitoring device further comprises a liquid water tank and a shielding box for the liquid to be tested to pass through, wherein the liquid water tank is arranged in the shielding box; The liquid water tank is provided with a positioning groove for accommodating the semiconductor detector, and the positioning groove is isolated from the internal chamber of the liquid water tank; the side wall of the liquid water tank is also provided with at least one water inlet connected to the internal chamber for injecting and / or discharging the liquid to be tested.

8. The monitoring device according to claim 7, characterized in that: The shielding box is provided with a water pipe port connected with the water port, which is used to receive the liquid to be tested externally, send the liquid to be tested into the liquid water tank or discharge the liquid to be tested in the liquid water tank to the outside.

9. The monitoring device according to claim 7, characterized in that: The shielding box is a multi-layer structure, comprising a copper layer, a lead layer and a stainless steel layer from the inside to the outside.

10. The monitoring device according to claim 7, characterized in that: The shielding box comprises a shielding box body with an opening and a shielding box cover; the shielding box cover is used to fit on the opening of the shielding box body to close the opening.

Images