Gamma spectrometer and radionuclide activity measuring method based on gamma spectrometer

Abstract

The invention discloses a gamma spectrometer and a radionuclide activity measuring method based on the gamma spectrometer. The gamma spectrometer comprises a CZT detector. The CZT detector comprises a CZT probe; the CZT probe comprises a CZT crystal group for receiving gamma rays; and the CZT crystal group comprises at least two CZT crystals. The CZT detector of the gamma spectrometer is more suitable for multi-point online measurement of a radiation source item, the CZT detector comprises the CZT probe, the CZT probe comprises the CZT crystal group used for receiving gamma rays, the CZT crystal group comprises at least two CZT crystals, the effective area of gamma ray detection is increased through the at least two CZT crystals, and the detection efficiency of high-energy gamma rays can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation source term monitoring, and in particular to a gamma spectrometer and a method for measuring the activity of radionuclides based on the gamma spectrometer. Background Art

[0002] The radiation source term is the radiation source of a nuclear power plant and is the focus of attention in the fields of chemistry and radiation protection of nuclear power plants. Under normal operating conditions, the radiation source term of the primary loop of a pressurized water reactor is mainly activated corrosion products, which may be present in the coolant or deposited on the surface of the primary loop system. The types of activated corrosion products are complex and may contain 58 Co, 60 Co, 59 Fe, 51 Cr, 54 Mn, 110m Ag, 121 Sb, 124 radioactive nuclides such as Sb. Detailed and accurate nuclide-level radiation source term data, such as the types, activities, and dose rate contributions of radionuclides at different positions in the primary loop system, are the prerequisites for carrying out fine control and optimization of the radiation source term.

[0003] However, at present, most nuclear power plants only carry out surface dose rate monitoring and radiochemical sampling measurements (usually twice a week), lacking nuclide-level source term data at different positions and their changes over time, and can no longer meet the requirements of refined management. Therefore, carrying out multi-point online measurement of the radiation source term is the only means. The online measurement of the radiation source term can only use the off-pipe non-destructive gamma spectroscopy measurement technology to directly measure the gamma spectrum outside the measured pipeline, and then inversely calculate the activity of the radionuclides in the pipeline through efficiency calibration.

[0004] The commonly used gamma spectrum detectors in nuclear power plants are mainly high-purity germanium (HPGe) detectors. Because of their excellent energy resolution and wide linear range, they can accurately measure all radionuclides with high precision and are the best choice for radiation source term measurement. HPGe detectors operate at low temperatures, require a cooler, are relatively large in volume and weight, and have relatively strict requirements for the on-site environment. However, the on-site environment of the primary loop system of a pressurized water reactor is complex and the space at most positions is limited. Therefore, HPGe detectors are not suitable for multi-point online measurement of the radiation source term. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a gamma spectrometer and a method for measuring the activity of radionuclides based on the gamma spectrometer, aiming at at least one defect existing in the related technologies mentioned in the above background art: the existing HPGe detectors are not suitable for multi-point online measurement of the radiation source term.

[0006] The technical solution adopted by the present invention to solve its technical problems is: to construct a gamma spectrometer, and the gamma spectrometer includes a CZT detector;

[0007] The CZT detector includes a CZT probe;

[0008] The CZT probe includes a CZT crystal group for receiving gamma rays; the CZT crystal group includes at least two CZT crystals.

[0009] In some embodiments, the connection mode of the CZT crystals in the CZT crystal group is parallel connection.

[0010] In some embodiments, the CZT detector further includes a collimator; one end of the collimator is provided with a channel structure for gamma rays to pass through, the collimator is detachably connected to the channel structure, and the CZT probe is placed inside the collimator.

[0011] In some embodiments, the main body of the collimator is a hollow cylindrical structure made of low-background lead material, and the surface of the collimator is covered with a support structure.

[0012] In some embodiments, the CZT probe further includes a main amplifier for amplifying the current signal generated by the CZT crystal group; in the incident direction of gamma rays, the main amplifier is located behind the CZT crystal group; the main amplifier and the CZT crystal group are integrally encapsulated in the CZT probe.

[0013] In some embodiments, the CZT crystal group further includes at least two preamplifiers, each CZT crystal is connected in series with the preamplifier, and the main amplifier is electrically connected to at least two preamplifiers.

[0014] In some embodiments, the gamma spectrometer further includes a control box and a data connection line, and the control box is data-connected to the CZT detector through the data connection line;

[0015] The control box includes a multi-channel analyzer for collecting analog signals of the CZT detector.

[0016] The present invention also provides a method for measuring the activity of a radionuclide including any one of the above gamma spectrometers. The gamma spectrometer further includes a multi-channel analyzer, and the measurement method includes the following steps:

[0017] Perform energy calibration on the multi-channel analyzer to establish the correspondence between gamma rays of different energies and the channels of the multi-channel analyzer;

[0018] Obtain the gamma spectrum obtained by continuously and cyclically measuring the object to be measured by the gamma spectrometer at preset time intervals within a preset time;

[0019] Model the measurement scenario, calculate the efficiency factors of gamma rays with different energies, and obtain the passive efficiency calibration curve;

[0020] Decompose the gamma spectrum according to the correspondence between gamma rays with different energies and the channel numbers of the multi-channel analyzer and the passive efficiency calibration curve, and obtain the types and activities of radionuclides at preset time intervals within a preset time.

[0021] In some embodiments, obtaining the gamma spectrum obtained by continuously and cyclically measuring the object to be measured at preset time intervals by the gamma spectrometer within a preset time includes:

[0022] Obtain the gamma spectrum obtained by continuously and cyclically measuring the object to be measured that has passed the dose rate detection by the gamma spectrometer at preset time intervals within a preset time;

[0023] Among them, the object to be measured that has passed the dose rate detection is the object to be measured whose channel structure is determined according to the dose rate detection at the measurement point.

[0024] In some embodiments, modeling the measurement scenario includes:

[0025] Obtain the CZT detector (100), the material and geometric dimensions of the object to be measured, and the distance between the CZT detector (100) and the object to be measured, and model the measurement scenario.

[0026] By implementing the present invention, the following beneficial effects are achieved:

[0027] The CZT detector of the gamma spectrometer of the present invention is more suitable for multi-point online measurement of radiation source terms, and the CZT detector includes a CZT probe. The CZT probe includes a CZT crystal group for receiving gamma rays. The CZT crystal group includes at least two CZT crystals. The at least two CZT crystals increase the effective area of gamma ray detection and can significantly improve the detection efficiency of high-energy gamma rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0029] Figure 1 Shows a schematic diagram of a CZT probe in an embodiment of the gamma spectrometer of the present invention;

[0030] Figure 2 Shows a schematic diagram of a CZT detector in an embodiment of the gamma spectrometer of the present invention;

[0031] Figure 3 Shows an exploded view of a CZT detector in an embodiment of the gamma spectrometer of the present invention;

[0032] Figure 4 Shows a cross-sectional view of a CZT detector in an embodiment of the gamma spectrometer of the present invention;

[0033] Figure 5 Shows a schematic diagram of a main amplifier in an embodiment of the gamma spectrometer of the present invention receiving current signals from at least two preamplifiers;

[0034] Figure 6 Shows a schematic diagram of a control box in an embodiment of the gamma spectrometer of the present invention;

[0035] Figure 7 Shows a cross-sectional view of a control box in an embodiment of the gamma spectrometer of the present invention;

[0036] Figure 8 Shows a schematic diagram of a CTZ detector and a bracket in an embodiment of the gamma spectrometer of the present invention;

[0037] Figure 9 Shows a flowchart of a method in an embodiment of the method for measuring the activity of a radionuclide in the gamma spectrometer of the present invention. Detailed implementation manners

[0038] For a clearer understanding of the technical features, objectives, and effects of the present invention, the detailed implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] It should be noted that the flowcharts shown in the accompanying drawings are only illustrative descriptions, and do not necessarily include all the contents and operations / steps, nor do they necessarily need to be executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined. Therefore, the actual execution order may be changed according to the actual situation.

[0040] The block diagrams shown in the accompanying drawings are only functional entities, and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0041] As Figure 1 shown, some embodiments of the present invention disclose a gamma spectrometer, which includes a CZT detector 100. The CZT detector can identify the main radionuclides. The CZT detector operates at room temperature without the need for refrigeration. The device has a small volume and weight, and its on-site accessibility is much better than that of HPGe detectors. Therefore, the gamma spectrometer based on the CZT detector is more suitable for multi-point on-line measurement of the primary loop radiation source term.

[0042] However, experiments have found that there is still a problem when using CZT detectors for measuring radiation source terms. Limited by the crystal production process, while ensuring the resolution, the size of CZT crystals is very small, with a maximum size of 0.5 cm * 1 cm * 1 cm. Gamma rays with energies higher than 500 keV are easily able to penetrate the crystals, resulting in a very low response efficiency of the CZT detectors. For 58 Co (811 keV) and 60 Co (1173 keV, 1332 keV) and other nuclides, the measurement accuracy is relatively poor. Therefore, the CZT detector 100 of the present invention includes a CZT probe 120. The CZT probe 120 includes a CZT crystal group 121 for receiving gamma rays. The CZT crystal group 121 includes at least two CZT crystals 1211. The at least two CZT crystals 1211 increase the effective area for gamma ray detection, and can significantly improve the detection efficiency for high-energy gamma rays. It can be understood that at least two can be two, three, or any number.

[0043] In some embodiments, the gamma spectrometer is used for multi-point on-line measurement of the primary loop radiation source term of a pressurized water reactor to obtain the activity of radioactive nuclides in the pipeline to be measured.

[0044] The CZT crystal 1211, namely cadmium zinc telluride crystal (CdZnTe, abbreviated as CZT), is an important II-VI group compound semiconductor material with unique physical and optoelectronic properties, and is widely used in fields such as radiation detection and imaging technology. The size of the CZT crystal 1211 is 0.5 cm × 1 cm × 1 cm. Here, the size of the CZT crystal 1211 is only for illustration and does not serve as a limitation of this application. It can also be other sizes.

[0045] Compared with HPGe detectors, the gamma spectrometer based on CZT detectors does not require refrigeration, has a small volume, a light weight, requires a small installation space, has strong adaptability to the on-site environment, and can be used for multi-point on-line measurement of radiation source terms.

[0046] In some embodiments, the connection method of the CZT crystals 1211 in the CZT crystal group 121 is in parallel.

[0047] Specifically, when the CZT crystal group 121 includes at least two CZT crystals 1211, the connection method between the CZT crystals 1211 pairwise is in parallel.

[0048] On the premise that the gamma spectrometer has good resolution (the resolution is better than 1.5% when the gamma ray energy is higher than 662 keV), by splicing at least two CZT crystals 1211, the detection efficiency for high-energy gamma rays is improved, thereby improving the measurement accuracy for 58 Co and 60 Co and other nuclides.

[0049] Such asFigures 2 to 4 As shown, in some embodiments, the CZT detector 100 further includes a collimator 110; one end of the collimator 110 is provided with a channel structure 111 for gamma rays to pass through. The collimator 110 is detachably linked to the channel structure 111, and a CZT probe 120 is placed inside the collimator 110.

[0050] The collimator 110 and the channel structure 111 are detachably connected by a magnetic attraction method, which can realize the quick replacement of the channel structure 111 of the collimator 110. The diameters of the channel structure 111 can be 35mm, 25mm, 15mm, or 5mm. Herein, the magnetic attraction method and the values of 35mm, 25mm, 15mm, and 5mm are only examples and do not limit this application. There can be others.

[0051] The front end of the collimator 110 is adjustable based on the channel structure 111. By using the magnetic attraction method, it can be quickly replaced, which improves the adaptability to different dose rate environments compared with a fixed channel structure.

[0052] In some embodiments, the main body of the collimator 110 is a hollow cylindrical structure made of low-background lead material, and the surface of the collimator 110 is covered with a support structure. A CZT probe 120 is placed in the hollow inside of the collimator 110.

[0053] In some embodiments, the CZT crystal group 121 further includes at least two preamplifiers 1212. Each CZT crystal 1211 is connected in series with a preamplifier 1212, and the main amplifier 122 is electrically connected to at least two preamplifiers 1212.

[0054] After the gamma rays pass through the CZT crystal 1211, the current signal released from the CZT crystal 1211 is weak and is prone to being confused with or lost to noise. Therefore, the preamplifier 1212 needs to be close to the CZT crystal 1211 to amplify the current signal released from the CZT crystal 1211 and improve the signal-to-noise ratio.

[0055] Exemplarily, when there are two CZT crystals 1211 in the CZT crystal group 121, the two CZT crystals 1211 are respectively connected in series with two preamplifiers 1212. Herein, the two CZT crystals 1211 and the two preamplifiers 1212 are only examples and do not limit this application. There can be others.

[0056] In some embodiments, the CZT probe 120 further includes a main amplifier 122 for amplifying the current signal generated by the CZT crystal group 121; in the incident direction of the gamma rays, the main amplifier 122 is located behind the CZT crystal group 121; the main amplifier 122 and the CZT crystal group 121 are integrally packaged in the CZT probe 120.

[0057] The current signal generated by the CZT crystal 1211 is small, and the main amplifier 122 further amplifies the current signal after the CZT crystal group 121 in the incident direction of gamma rays; more specifically, the main amplifier 122 further shapes and amplifies the current signal released by the preamplifier 1212.

[0058] As Figure 5 shown, the main amplifier 122 needs to be improved according to the number of CZT crystals 1211 and preamplifiers 1212 in the CZT crystal group 121. Exemplarily, when the number of CZT crystals 1211 in the CZT crystal group 121 is two, the two CZT crystals 1211 are respectively connected in series with two preamplifiers 1212, and the CZT crystals 1211 and preamplifiers 1212 of one group are connected in parallel with the CZT crystals 1211 and preamplifiers 1212 of the other group. The main amplifier 122 is connected to the main path where the two groups of CZT crystals 1211 and preamplifiers 1212 are connected in parallel. The main amplifier 122 simultaneously receives the two-way current signals of the two preamplifiers 1212 and shapes and amplifies the two-way current signals. Among them, the two CZT crystals 1211 and the two preamplifiers 1212 here are only examples and do not limit this application. It can also be others.

[0059] As Figure 6 shown, in some embodiments, the gamma spectrometer further includes a control box 200 and a data connection line 300. The control box 200 is data-connected to the CZT detector 100 through the data connection line 300; the control box 200 includes a multi-channel analyzer 210 for collecting analog signals of the CZT detector 100.

[0060] As Figure 7 shown, the control box 200 is integratedly designed, integrating the digital multi-channel analyzer 210, control circuit, industrial computer 220, memory, etc., to realize the control function of detection and the storage function of measurement data, reducing the number of devices and improving portability.

[0061] The control box 200 is equipped with multiple interfaces, including a power supply interface, a detector signal interface, a USB interface, a network interface, etc. An external computer can access the control box 200 to obtain measurement information and view and analyze the measurement data stored locally. And the control box 200 is small in size and good in portability.

[0062] As Figure 8 shown, in some embodiments, the gamma spectrometer further includes a bracket 400; the CZT detector 100 further includes a bracket connection seat 130, and the bracket connection seat 130 is detachably connected to the bracket 400.

[0063] The support 400 is equipped with a spherical pan-tilt head, which plays a role in fixing and supporting the CZT detector 100. The support 400 is weighed enough to support the CZT detector 100, and the height and angle of the support 400 can be adjusted within a certain range.

[0064] In some embodiments, the CZT detector 100 further includes a grip 140, and the grip 140 is located at the top of the CZT detector 100.

[0065] Compared with the HPGe detector, the components of the gamma spectrometer based on the CZT detector should be as integrated and miniaturized as possible to further improve the on-site accessibility.

[0066] As Figure 9 shown, some embodiments of the present invention disclose a method for measuring the activity of radionuclides of the gamma spectrometer described in any of the above embodiments. The gamma spectrometer further includes a multi-channel analyzer 210. This measurement method is applied to a computer device, and the measurement method includes the following steps:

[0067] Perform energy calibration on the multi-channel analyzer 210 to establish the corresponding relationship between gamma rays of different energies and the channels of the multi-channel analyzer 210;

[0068] Obtain the gamma spectrum obtained by the gamma spectrometer after continuously and cyclically measuring the object to be measured at preset time intervals within a preset time;

[0069] Model the measurement scene, calculate the efficiency factors of gamma rays of different energies, and obtain a passive efficiency calibration curve;

[0070] Decompose the gamma spectrum according to the corresponding relationship between gamma rays of different energies and the channels of the multi-channel analyzer 210 and the passive efficiency calibration curve to obtain the types and activities of radionuclides at preset time intervals within a preset time.

[0071] Performing energy calibration on the multi-channel analyzer 210 includes: performing energy calibration on the CZT detector and the multi-channel analyzer.

[0072] Adjust the height and angle of the support 400 according to the height and position of the object to be measured, and judge by manual or laser rangefinder to make the center of the CZT detector 100 face the center of the object to be measured. Here, the judgment by manual or laser rangefinder is only an example and is not a limitation of the present application. It can also be others.

[0073] The CZT detector 100 is connected to the control box 200 through a data connection line 300, and the control box 200 is connected to a power supply.

[0074] In some embodiments, obtaining the gamma spectrum obtained by the gamma spectrometer after continuously and cyclically measuring the object to be measured at a preset time interval within a preset time includes: obtaining the gamma spectrum obtained by the gamma spectrometer after continuously and cyclically measuring the object to be measured that has passed the dose rate detection at a preset time interval within a preset time;

[0075] Among them, the object to be measured that has passed the dose rate detection is the object to be measured for determining the pore structure 111 according to the dose rate detection at the measurement point. Specifically, the dose rate of the object to be measured is measured by a dose rate meter, and the size of the pore structure 111 is determined by the dose rate of the object to be measured, so as to realize the magnetic adsorption replacement of the pore structure 111 of the collimator 110.

[0076] In some embodiments, modeling the measurement scenario includes: obtaining the CZT detector 100, the material and geometric dimensions of the object to be measured, and the distance between the CZT detector 100 and the object to be measured, and modeling the measurement scenario.

[0077] Specifically, obtain the CZT detector 100, the material and geometric dimensions of the object to be measured, and the distance between the CZT detector 100 and the object to be measured, and input the obtained parameters into the passive efficiency calibration software to model the measurement scenario.

[0078] In some embodiments, according to the correspondence between gamma rays of different energies and the channels of the multi-channel analyzer 210 and the passive efficiency calibration curve, the gamma spectrum is de-spectrally analyzed to obtain the types and activities of radionuclides at a preset time interval within a preset time, including: inputting the parameters of the passive calibration curve into the measurement control software, and de-spectrally analyzing the gamma spectrum to obtain the types and activities of radionuclides at a preset time interval within a preset time.

[0079] It can be understood that the above embodiments only represent some implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above embodiments or technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention, that is, the embodiments described in "in some embodiments" can be freely combined with any of the above and below embodiments. Therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention should fall within the scope covered by the claims of the present invention.

Claims

1. A gamma spectrometer, characterized in that, The gamma spectrometer includes a CZT detector (100); The CZT detector (100) includes a CZT probe head (120); The CZT probe head (120) includes a CZT crystal group (121) for receiving gamma rays; the CZT crystal group (121) includes at least two CZT crystals (1211).

2. The gamma spectrometer according to claim 1, wherein The connection mode of the CZT crystals (1211) in the CZT crystal group (121) is in parallel.

3. The gamma spectrometer according to claim 1, characterized in that, The CZT detector (100) further includes a collimator (110); one end of the collimator (110) is provided with a channel structure (111) for gamma rays to pass through, the collimator (110) is detachably connected to the channel structure (111), and the CZT probe head (120) is placed inside the collimator (110).

4. The gamma spectrometer according to claim 3, characterized in that, The main body of the collimator (110) is a hollow cylindrical structure made of low-background lead material, and the surface of the collimator (110) is covered with a support structure.

5. The gamma spectrometer according to claim 1, characterized in that, The CZT probe head (120) further includes a main amplifier (122) for amplifying the current signal generated by the CZT crystal group (121); in the incident direction of gamma rays, the main amplifier (122) is located behind the CZT crystal group (121); the main amplifier (122) is integrally encapsulated with the CZT crystal group (121) in the CZT probe head (120).

6. The gamma spectrometer according to claim 5, characterized in that The CZT crystal group (121) further includes at least two preamplifiers (1212), each CZT crystal (1211) is connected in series with the preamplifier (1212), and the main amplifier (122) is electrically connected to at least two preamplifiers (1212).

7. The gamma spectrometer according to claim 1, characterized in that, The gamma spectrometer further includes a control box (200) and a data connection line (300), and the control box (200) is data-connected to the CZT detector (100) through the data connection line (300); The control box (200) includes a multi-channel analyzer (210) for collecting analog signals of the CZT detector (100).

8. A method for measuring the activity of radionuclides of a gamma spectrometer according to any one of claims 1-7, characterized in that, The gamma spectrometer further includes a multi-channel analyzer (210), and the measurement method includes the following steps: Perform energy calibration on the multi-channel analyzer (210) to establish the corresponding relationship between gamma rays of different energies and the channels of the multi-channel analyzer (210); Obtain the gamma spectrum obtained by continuously and cyclically measuring the object to be measured by the gamma spectrometer at preset time intervals within a preset time; Model the measurement scenario, calculate the efficiency factors of gamma rays of different energies, and obtain a passive efficiency calibration curve; Decompose the gamma spectrum according to the corresponding relationship between gamma rays of different energies and the channels of the multi-channel analyzer (210) and the passive efficiency calibration curve, and obtain the types and activities of radionuclides at preset time intervals within a preset time.

9. The method for measuring the activity of a radionuclide based on a gamma spectrometer according to claim 8, wherein Obtaining the gamma spectrum obtained by continuously and cyclically measuring the object to be measured by the gamma spectrometer at preset time intervals within a preset time includes: Obtain the gamma spectrum obtained by continuously and cyclically measuring the object to be measured that has passed the dose rate detection by the gamma spectrometer at preset time intervals within a preset time; Among them, the object to be measured that has undergone dose rate detection is the object to be measured for determining the pore structure (111) based on the dose rate detection at the measurement point.

10. The method for measuring the activity of radionuclides based on a gamma spectrometer according to claim 8, characterized in that, Model the measurement scenario, including: Obtain the CZT detector (100), the material and geometric dimensions of the object to be measured, and the distance between the CZT detector (100) and the object to be measured, and model the measurement scenario.

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