A gamma contamination monitor and monitoring method suitable for large volume article monitoring

Abstract

The application discloses a kind of gamma contamination monitor and monitoring method suitable for large volume article monitoring, including inside hollow shell, controller, large area plastic scintillator gamma detector and multichannel energy spectrum data acquisition module;Multichannel energy spectrum data acquisition module receives nuclear pulse signal detected by gamma detector and converts it into energy spectrum data;Controller according to the size of all energy spectrum data divides all energy spectrum data to 3 energy intervals, and respectively to the energy spectrum data in 3 energy intervals is fused, to obtain the nuclide distribution of 3 energy intervals;According to nuclide distribution and preset interval reference nuclide, activity conversion is carried out, and activity and specific activity are obtained.The purpose of the present application is to provide a kind of gamma contamination monitor and monitoring method suitable for large volume article, using relatively cheap large area plastic scintillator and multichannel energy spectrum data acquisition module, form has the ability to measure more than 300L large package and article.

Description

Technical Field

[0001] This invention relates to the field of gamma pollution monitoring technology, and in particular to a gamma pollution monitoring instrument and method suitable for monitoring large-volume items. Background Technology

[0002] Currently, monitoring instruments for gamma contamination on items in nuclear-contaminated sites are typically equipped with one or two detectors and designed with a measuring chamber of approximately tens of liters for measuring smaller items. The measurement results are expressed as counts or converted into activity indicators. However, these devices cannot measure larger items and are significantly affected by high or complex background radiation in complex environments. Furthermore, differences in the position of the measured item within the measuring chamber can cause significant deviations in the measurement results. Additionally, during activity conversion, only relative conversion can be performed for a single nuclide, thus failing to accurately measure and convert activity. Therefore, these devices cannot meet the current needs of nuclear-contaminated sites for monitoring contamination on larger items.

[0003] Chinese patent CN109696700A discloses a monitoring system for extremely low level transuranic radioactive waste packages. This patent describes the use of multiple medium-sized and irregularly shaped NaI detectors to form a small object detection chamber, employing multi-channel technology to monitor radioactive materials and perform nuclide analysis on the packages and waste. However, large, medium-sized, and irregularly shaped NaI detectors are extremely expensive. The combination of eight NaI detectors with an eight-channel multi-data acquisition module results in very high equipment costs and makes it impossible to construct a large-volume measurement chamber. Summary of the Invention

[0004] The purpose of this invention is to provide a gamma contamination monitor and monitoring method suitable for monitoring large-volume items. It utilizes six relatively inexpensive large-area plastic scintillators combined with six multi-channel data acquisition modules to form a system capable of measuring gamma contamination in large cargo packages and items larger than 300L.

[0005] This invention is achieved through the following technical solution:

[0006] A gamma pollution monitor suitable for monitoring large-volume items includes a hollow shell, a controller, six large-area plastic scintillator gamma detectors, and six multi-channel data acquisition modules. The inner wall of the shell is provided with a shield, and the six large-area plastic scintillator gamma detectors are arranged on the shield of the shell in a 4π spatial layout.

[0007] The large-area plastic scintillator gamma detector transmits the detected nuclear pulse signal to the corresponding multichannel energy spectrum data acquisition module. The multichannel energy spectrum data acquisition module obtains energy spectrum data based on the nuclear pulse signal. The controller divides all the energy spectrum data into three energy ranges according to the magnitude of all the energy spectrum data, and fuses the energy spectrum data in the three energy ranges to obtain the nuclide distribution in the three energy ranges. Based on the nuclide distribution and a preset range reference nuclide, activity conversion is performed to obtain activity and specific activity. The three energy ranges are a low-energy range, a medium-energy range, and a high-energy range.

[0008] In existing technologies, monitoring instruments for gamma contamination on items in nuclear-contaminated sites are typically equipped with one or two detectors and designed with a measuring chamber of approximately tens of liters for measuring smaller items. The measurement results are expressed as counts or converted into activity indicators. However, such devices cannot measure larger items and are significantly affected by high or complex background noise in complex environments. Furthermore, differences in the position of the measured item within the measuring chamber can cause significant deviations in the measurement results. Additionally, during activity conversion, only relative conversion can be performed for a single nuclide, thus failing to accurately measure and convert activity. Therefore, these devices cannot meet the current needs of nuclear-contaminated sites for monitoring contamination on larger items.

[0009] Chinese patent CN109696700A discloses a monitoring system for extremely low level transuranic radioactive waste packages. This patent describes the use of multiple medium-sized and irregularly shaped NaI detectors to form a small object detection chamber, employing multi-channel technology to monitor radioactive materials and perform nuclide analysis on the packages and waste. However, large, medium-sized, and irregularly shaped NaI detectors are extremely expensive; eight NaI detectors combined with an eight-channel multi-data acquisition module result in very high equipment costs and make it impossible to form a large-volume measurement chamber. Based on this, this application provides a gamma contamination monitor suitable for monitoring large-volume objects. It utilizes six relatively inexpensive large-area plastic scintillator gamma detectors for detection. At the same time, the design takes into account the poor energy resolution of plastic scintillator gamma detectors and innovatively combines six multi-channel data acquisition modules to divide the energy range of 50keV to 3MeV into three energy ranges: low, medium, and high. Through the energy spectrum partitioning algorithm, the activity of nuclides in different ranges is converted separately, so that the activity measurement results of the device are much higher than those of traditional single-channel gamma contamination monitors. This makes it possible to measure large-volume objects while keeping the equipment cost much lower than that of small object measuring devices using NaI scintillators.

[0010] Preferably, it also includes a perforated weighing tray, which is disposed on a shield at the bottom of the housing, and the weighing tray does not contact the large-area plastic scintillator gamma detector.

[0011] Preferably, it also includes a pressure sensor, which is disposed below the shield at the bottom of the housing and is electrically connected to the controller.

[0012] Preferably, the shielding body includes a first shielding layer and a second shielding layer arranged sequentially from top to bottom;

[0013] The first shielding layer includes a stainless steel layer and a copper plate layer;

[0014] The second shielding layer includes a first lead layer, a second lead layer, and a third lead layer of different thicknesses.

[0015] Preferably, the thickness of the first lead layer is 10 mm, the thickness of the second lead layer is 15 mm, and / or the thickness of the third lead layer is 25 mm.

[0016] Preferably, the housing is further provided with doors on its two symmetrical sidewalls, and the doors are opened and closed by electromagnetic locks.

[0017] In a second aspect, this application provides a gamma contamination monitoring method suitable for monitoring large-volume objects, applied to a gamma contamination monitoring instrument for monitoring large-volume objects as described above, comprising the following steps:

[0018] The nuclear pulse signal detected by the large-area plastic scintillator gamma detector is acquired and converted into energy spectrum data;

[0019] Based on the magnitude of all the energy spectrum data, all the energy spectrum data are divided into three energy ranges: a low energy range, a medium energy range, and a high energy range.

[0020] The energy spectrum data in the three energy ranges are fused to obtain the nuclide distribution in the three energy ranges.

[0021] Based on the nuclide distribution and a preset interval reference nuclide, activity conversion is performed to obtain activity and specific activity.

[0022] Preferably, the method further includes a compensation step, which is used to correct the energy spectrum data and includes the following steps:

[0023] Obtain the weight value of the item being measured;

[0024] The fused energy spectrum data is measured and compensated based on the weight value to obtain compensated energy spectrum data. Preferably, the compensation value of the weight value for the energy spectrum data is:

[0025] Y = m × R × Ni;

[0026] Y represents the compensation value, m represents the weight, R represents the supplementary coefficient (embedded with different material compensation coefficients), and Ni is the count value in the i-th energy region after fusion (i = 1, 2, 3).

[0027] Preferably, the method further includes the following steps:

[0028] The radiation count measurement value of the tested item and the detection positions of the six large-area plastic scintillator gamma detectors were obtained.

[0029] Based on the six radiation count measurements and the six detection locations, 21 composite channels are virtually constructed.

[0030] The detection cavity is divided into 27 location regions based on the 21 composite channels and the 6 radiation counting measurements.

[0031] During pollution location, based on the radiation count measurements of the 6 mentioned radiation counts and the counts of the 21 mentioned composite channels, the internal algorithm is used for analysis and processing to divide the tested item into 27 detection channels corresponding to the 27 mentioned location areas;

[0032] Based on the spatial attenuation characteristics of radiation intensity, the detection data from the 27 detection channels were compared and corrected to identify the 1-3 areas with the highest probability of contamination.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] In terms of activity conversion, it solves the problems of distortion in single nuclide activity conversion in traditional small-scale pollution monitoring, as well as the problems of high cost, long time, detection limit, and inability to achieve large-volume NaI measurement. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a perspective view of the internal structure of the gamma pollution monitor of the present invention;

[0037] Figure 2 This is a partial magnified perspective view of the gamma pollution monitor of the present invention;

[0038] Figure 3 This is a schematic diagram of the internal structure of the gamma pollution monitor of the present invention;

[0039] Figure 4 This is a schematic diagram of the overall structure of the gamma pollution monitor of the present invention;

[0040] Figure 5 This is a top view of the gamma pollution monitor of the present invention;

[0041] The attached diagram shows the markings and corresponding component names:

[0042] 1. Housing; 2. Large-area plastic scintillator gamma detector; 3. Weighing tray; 4. Pressure sensor; 5. Door; Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0044] Example 1

[0045] A gamma contamination monitor suitable for monitoring large-volume items, such as Figure 1-5 As shown, it includes an internally hollow shell 1, six large-area plastic scintillator gamma detectors 2, and a 256-channel energy spectrum data acquisition module. The inner wall of the shell 1 is equipped with a shield, and the six large-area plastic scintillator gamma detectors 2 are arranged on the shield of the shell 1 in a 4π spatial layout.

[0046] A large-area plastic scintillator gamma detector transmits the detected nuclear pulse signal to the corresponding 256-channel energy spectrum data acquisition module. The 256-channel energy spectrum data acquisition module obtains energy spectrum data based on the nuclear pulse signal. The controller divides all the energy spectrum data into three energy ranges according to the magnitude of all the energy spectrum data, and fuses the energy spectrum data in the three energy ranges to obtain the nuclide distribution in the three energy ranges. Then, based on the nuclide distribution and the preset interval reference nuclide, the activity is converted to obtain the activity and specific activity. The three energy ranges are the low-energy range, the medium-energy range, and the high-energy range.

[0047] In this embodiment, six 256-channel energy spectrum data acquisition modules are used to divide the energy range (50keV-3MeV) into three energy ranges: low, medium, and high. The specific division is set according to the actual situation. Then, the energy spectrum data is fused in each of the three ranges, and the reference nuclide is used according to the range (the reference nuclide for the low-energy range is Am by default). 241 Or Ba 133 The reference nuclide in the medium energy range is Cs. 137 The reference nuclide in the high-energy range uses Co. 60 The activity conversion of nuclides is carried out to solve the problem of distortion in the activity conversion of single nuclides in traditional small-scale pollution monitoring, as well as the problems of high cost, long time, high detection limit, and inability to achieve large-volume measurement of NaI.

[0048] In this embodiment, the 4π spatial layout means that the large-area plastic scintillator gamma detector 2 is arranged on the six inner walls of the housing 1 in a head-to-tail arrangement to maintain the spatial symmetry of the detector's sensitive area, reduce the influence of the measurement position on the measurement results, and achieve a result deviation of less than 15%.

[0049] Furthermore, the shielding in this embodiment comprises two layers. The first layer is composed of stainless steel and copper plates of a certain thickness, and the second layer is composed of lead of three different thicknesses: 10mm, 15mm, and 25mm. This ensures excellent sensitivity of the device in complex high-background environments. Verification has shown that, with an environmental background of 0.5 μSv / h, the device can still maintain a detection limit below 40 Bq during a 60-second measurement period.

[0050] Furthermore, such as Figure 2 As shown, it also includes a hollowed-out weighing tray 3, which is set on the shield at the bottom of the housing 1, and the weighing tray 3 does not contact the large-area plastic scintillator γ detector 2.

[0051] In this embodiment, by setting up a weighing tray 3, when the item to be tested is placed inside the housing 1, the item will not directly affect the large-area plastic scintillator gamma detector 2, so as to avoid damage to the large-area plastic scintillator gamma detector 2; at the same time, the weighing tray 3 adopts a hollow design, which will not affect the detection of the large-area plastic scintillator gamma detector 2.

[0052] Furthermore, it also includes pressure sensors 4, which are disposed below the shield at the bottom of the inner part of the housing 1 and are electrically connected to the controller. Preferably, there are four pressure sensors 4, which are evenly distributed at the bottom of the inner part of the housing 1.

[0053] In this embodiment, pressure sensor 4 is used to measure the weight of the object being measured and to perform corresponding numerical compensation on the energy spectrum data based on the weight of the object, so as to reduce the deviation caused by the shielding of the object itself. The compensation value is calculated as: weight × compensation coefficient × count value.

[0054] Furthermore, doors 5 are provided on the two symmetrical side walls of the housing 1, and the doors 5 are opened and closed by electromagnetic locks.

[0055] This embodiment features two doors 5, one at the front and one at the back, on the housing 1. It is equipped with a high-precision distance sensor and a locking mechanism to meet the user's needs for segmented measurement of long tools or items. Simultaneously, it can achieve interlocking between the two doors 5 in short tool or short item mode, and can be configured as a single-door 5 mode or a double-door 5 entry / exit mode as needed.

[0056] The following describes the usage of a gamma contamination monitor suitable for monitoring large-volume items provided in this embodiment:

[0057] Short Tool Mode

[0058] Step 1: The equipment is powered on and enters the self-test process. After the self-test is completed, the equipment performs the baseline measurement before measurement.

[0059] Step 2: After the baseline measurement is completed, open front door 5 and prompt the user to place the item to be measured.

[0060] Step 3: Close the front door 5 and begin radiation counting and weight measurement of the item being tested;

[0061] Step 4: After the measurement is completed, the total radiation count, the energy spectrum data of the six large-area plastic scintillator gamma detectors 2, and the weight value of the measured object are obtained. The energy spectrum data is compensated accordingly based on the weight value to obtain the compensated energy spectrum data. By fusing the compensated energy spectrum data, the nuclide distribution in the three energy ranges is obtained. Combined with the preset range reference nuclides, the count values ​​of the three ranges are converted into activity and specific activity and displayed.

[0062] Step 5: Based on the counts of the large-area plastic scintillator gamma detectors 2 and the counts of the virtual composite channel, the internal algorithm is used to analyze and process the data, and divide the test item into 27 detection channels corresponding to 27 location areas (6 probes plus 21 composite channels). After comparing and correcting the data of the 27 channels, the 1-3 areas with the highest probability of contamination can be given, so as to achieve precise location of contamination.

[0063] Step 6: Prompt the user based on whether the tested item is contaminated;

[0064] Step 7: Open front door 5 (uncontaminated, single door 5 mode), open rear door 5 (uncontaminated, double door 5 mode), open front door 5 (contaminated);

[0065] Step 8: Close the front / rear door 5. If the measurement result is not contaminated, directly enter the background smoothing and waiting state for measurement. If the measurement result is contaminated, enter the forced background measurement.

[0066] Long Tool Pattern

[0067] Step 1: Switch from short tool mode to long tool mode;

[0068] Step 2: Open all five front and rear doors, and re-measure the baseline after a certain period of time;

[0069] Step 3: Enter the measurement preparation state. Long tool measurements need to be performed in segments.

[0070] Step 4: Press the measurement button to start the measurement. After the measurement is completed, repeat the measurement for the next segment.

[0071] After step 5 is completed, the software automatically generates a long tool virtual graphic based on the number of measurement segments, and provides the pollution count and total energy spectrum distribution segment by segment. It also provides voice prompts to indicate whether there is pollution and provides the activity value and total activity value converted within the three energy ranges.

[0072] Step 6: End the measurement. If the measurement result is uncontaminated, proceed directly to the background smoothing and waiting state. If the measurement result is contaminated, proceed to the forced background measurement.

[0073] Example 2

[0074] This embodiment provides a gamma contamination monitoring method suitable for monitoring large-volume objects, applied to a gamma contamination monitoring instrument for monitoring large-volume objects as provided in Embodiment 1, including the following steps:

[0075] The nuclear pulse signal detected by the large-area plastic scintillator gamma detector 2 was acquired and converted into energy spectrum data;

[0076] Based on the magnitude of all energy spectrum data, all energy spectrum data are divided into three energy ranges: low energy range, medium energy range, and high energy range.

[0077] The energy spectrum data in the three energy ranges were fused to obtain the nuclide distribution in the three energy ranges;

[0078] Activity and specific activity are obtained by performing activity conversion based on the distribution of nuclides and a preset interval of reference nuclides.

[0079] Furthermore, it also includes a compensation step, which is used to correct the energy spectrum data, including the following steps:

[0080] Obtain the weight value of the item being measured;

[0081] The fused energy spectrum data is measured and compensated based on the weight value to obtain the compensated energy spectrum data.

[0082] The compensation value for the weight value in the energy spectrum data is as follows:

[0083] Y = m × R × Ni;

[0084] Y represents the compensation value, m represents the weight, R represents the supplementary coefficient (embedded with different material compensation coefficients), and Ni is the count value in the i-th energy region after fusion (i = 1, 2, 3).

[0085] Furthermore, it also includes the following steps:

[0086] The radiation count measurement value of the tested item and the detection positions of 6 large-area plastic scintillator gamma detectors 2 were obtained;

[0087] Based on 6 radiation count measurements and 6 detection locations, 21 composite channels were virtually created;

[0088] The detection cavity was divided into 27 location regions based on 21 composite channel and 6 radiation counting measurements;

[0089] During contamination location, based on the radiation count measurements from 6 radiation counts and the counts from 21 composite channels, the internal algorithm is used to analyze and process the data, dividing the tested item into 27 detection channels corresponding to 27 location areas.

[0090] By comparing and correcting the detection data from 27 detection channels, the 1-3 areas with the highest probability of pollution were identified.

[0091] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gamma contamination monitor suitable for large volume object monitoring, characterized in that, The gamma contamination monitor comprises a hollow shell (1), a controller, six large-area plastic scintillator gamma detectors (2) and six multi-channel energy spectrum data acquisition modules, the inner wall of the shell (1) is provided with a shielding body, and the six large-area plastic scintillator gamma detectors (2) are arranged on the shielding body of the shell (1) in a 4π spatial layout mode. The nuclear pulse signals detected by the large-area plastic scintillator gamma detectors (2) are transmitted to the corresponding multi-channel energy spectrum data acquisition modules, and the multi-channel energy spectrum data acquisition modules obtain energy spectrum data according to the nuclear pulse signals; the controller divides all the energy spectrum data into three energy intervals according to the size of all the energy spectrum data, and fuses the energy spectrum data in the three energy intervals respectively to obtain the nuclide distribution of the three energy intervals; and the activity and specific activity are obtained by converting the nuclide distribution and the preset interval reference nuclide.

2. The gamma contamination monitor suitable for monitoring large volume objects according to claim 1, wherein, The gamma contamination monitor further comprises a hollow weighing tray (3) arranged on the shielding body at the bottom of the shell (1), and the weighing tray (3) is not in contact with the large-area plastic scintillator gamma detectors (2).

3. The gamma contamination monitor suitable for monitoring large volume objects according to claim 1, wherein, The gamma contamination monitor further comprises a pressure sensor (4) arranged below the shielding body at the bottom of the shell (1) and electrically connected with the controller.

4. The gamma contamination monitor suitable for monitoring large volume objects according to claim 1, wherein, The shielding body comprises a first shielding layer and a second shielding layer arranged in sequence from top to bottom; The first shielding layer comprises a stainless steel layer and a copper plate layer; The second shielding layer comprises a first lead layer, a second lead layer and a third lead layer with different thicknesses.

5. A gamma contamination monitor suitable for use in monitoring large volume objects as claimed in claim 4, wherein, The thickness of the first lead layer is 10 mm, the thickness of the second lead layer is 15 mm, and / or the thickness of the third lead layer is 25 mm.

6. The gamma contamination monitor suitable for monitoring large volume objects according to any one of claims 1-5, wherein, The shell (1) is further provided with a door (5) on two symmetrical side walls, and the door (5) is opened and closed by an electromagnetic lock.

7. A method of gamma contamination monitoring suitable for bulk item monitoring, characterized in that, The gamma contamination monitor for monitoring large-volume objects according to any one of claims 1-6 comprises the following steps: Obtaining the nuclear pulse signals detected by the large-area plastic scintillator gamma detectors (2) and converting them into energy spectrum data; Dividing all the energy spectrum data into three energy intervals according to the size of all the energy spectrum data; the three energy intervals are low-energy interval, medium-energy interval and high-energy interval; Fusing the energy spectrum data in the three energy intervals respectively to obtain the nuclide distribution of the three energy intervals; Converting the nuclide distribution and the preset interval reference nuclide to obtain the activity and specific activity.

8. A gamma contamination monitoring method suitable for large volume object monitoring according to claim 7, characterized in that, The gamma contamination monitor further comprises a compensation step for correcting the energy spectrum data, which comprises the following steps: Obtaining the weight value of the measured object; Compensating the fused energy spectrum data according to the weight value to obtain the compensated energy spectrum data.

9. A gamma contamination monitoring method suitable for large volume object monitoring according to claim 8, characterized in that, The compensation value of the weight value on the energy spectrum data is: Y=m×R×Ni; Y represents a compensation value, m represents weight, R represents a supplementary coefficient, and Ni is a count value in the i-th energy region after fusion (i = 1, 2, 3).

10. A method of gamma contamination monitoring suitable for large volume object monitoring according to any one of claims 7-9, characterized in that, Further comprising the following steps: Obtaining radiation count measurement values of the measured object and detection positions of the six large-area plastic scintillator gamma detectors (2); virtually generating 21 composite channels according to the six radiation count measurement values and the six detection positions; dividing the detection cavity into 27 position regions according to the 21 composite channels and the six radiation count measurement values; In the pollution positioning, according to the count conditions of the six radiation count measurement values and the 21 composite channels, the measured object is divided into 27 detection channels corresponding to the 27 position regions through internal algorithm analysis processing; According to the spatial attenuation characteristics of the ray intensity, the detection data of the 27 detection channels are compared and corrected to obtain 1-3 regions with the maximum pollution probability.

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