Apparatus and method for inspecting for radioactivity in inspection object

Abstract

The present disclosure provides an apparatus and method for inspecting for radioactivity in an inspection object. The apparatus includes: a radiation detection unit configured to measure an energy spectrum of radiation generated from an inspection object; and a control unit configured to determine a radioactive nuclide on the basis of the measured energy spectrum, determine a region of interest to be applied to the measured energy spectrum according to the determined nuclide, determine a count rate in the region of interest, and determine a radioactivity concentration on the basis of the count rate in the region of interest. According to the present disclosure, it is possible to accurately determine Compton maximum energy for low-energy gamma rays by introducing a function related to energy resolution at the time of analyzing an energy spectrum, and thus it is possible to set a suitable region of interest for various energies, thereby improving the reliability of radioactivity inspection in an inspection object.

Description

Device and method for examining radioactivity in a subject of examination

[0001] The present disclosure relates to a radioactivity inspection technique, and more particularly, to a device and method for inspecting radioactivity within an inspection subject.

[0002] As the issue of marine radioactivity affecting humans and marine life becomes increasingly prominent, various radiation detectors are being used to accurately determine whether radioactivity in seafood complies with established standards. Conventional technologies utilize high-resolution HPGe detectors capable of gamma-ray spectroscopy. However, their limited size limits detection efficiency and necessitates long-term measurement. In contrast, plastic scintillators based on polyvinyl toluene (PVT) offer the advantage of being inexpensive and capable of large-scale production. This high detection efficiency makes PVT-based detectors ideal for radioactivity testing of seafood.

[0003] However, since gamma-ray peak analysis is not possible with PVT-based detectors, it is important to appropriately set the region around the Compton edge in the measured energy spectrum as the region of interest to minimize the influence of background and electrical noise when determining radioactivity in seafood. However, plastic scintillators are composed of hydrogen and carbon with low atomic numbers and have low light intensity, resulting in low energy resolution. Therefore, when applying a PVT detector, if low-energy gamma-rays are emitted from radioactive materials present in seafood, the self-shielding effect may cause problems in accurately identifying the Compton maximum energy in the measured energy spectrum.

[0004] Meanwhile, energy-weighting techniques exist that apply energy weighting to the energy spectrum of gamma rays measured using plastic scintillators. However, when applying these techniques, as the energy-weighting exponent increases, the error in the Compton maximum energy increases, making it difficult to determine an appropriate region of interest. This can make accurate determination of radioactivity in seafood impossible.

[0005] To solve these problems, the present disclosure aims to provide a device and method for testing radioactivity with high reliability in a test subject such as aquatic products.

[0006] According to one embodiment of the present disclosure, a device for examining radioactivity within a subject of inspection is provided. The device may include a radiation detector configured to measure an energy spectrum of radiation emitted from the subject of inspection; and a controller configured to determine a radioactive nuclide based on the measured energy spectrum, determine a region of interest to apply the measured energy spectrum according to the determined nuclide, determine a count rate within the region of interest, and determine a radioactivity concentration based on the count rate within the region of interest.

[0007] In addition, the controller may be additionally configured to control the output of information on the determined nuclide and the determined radioactivity concentration together with an alarm signal when the determined radioactivity concentration is higher than an alarm level set for the determined nuclide.

[0008] Additionally, the controller may be configured to determine the radioactive nuclide by determining the similarity between the reference energy spectrum for each nuclide and the measured energy spectrum using the MLE (Maximum Likelihood Estimation) technique.

[0009] Additionally, the control unit may be configured to determine the region of interest based on the Compton edge energy, Compton maximum energy, and resolution of the radiation detector for the determined nuclide.

[0010] In addition, the above area of ​​interest is [E CM - FWHM / 2, E CE + FWHM / 2] can be determined. Here, E CE is the Compton edge energy, and E CM is the Compton maximum energy, and FWHM is the resolution.

[0011] Additionally, the resolution of the radiation detector can be determined according to the following resolution function.

[0012]

[0013] Here, E represents the Compton edge energy or the gamma-ray energy absorbed by the detector, FWHM represents the resolution of the detector at the gamma-ray energy E, and a, b and c represent the degree of spread of the peak by the gamma-ray energy within the spectrum.

[0014] Additionally, the controller may be configured to determine the Compton maximum energy according to a fitted energy to Compton maximum energy relationship based on the resolution function.

[0015] Additionally, the controller may be configured to determine a count rate within the region of interest with the background removed, and determine the radioactivity concentration based on the count rate, the gamma-ray emission rate of the determined nuclide, the detection efficiency of the inspection target, and the weight of the inspection target.

[0016] According to one embodiment of the present disclosure, a method for examining radioactivity within an inspection subject is provided. The method may include: measuring an energy spectrum of radiation emitted from the inspection subject; identifying a radioactive nuclide based on the measured energy spectrum; determining a region of interest to apply the measured energy spectrum based on the identified nuclide; determining a count rate within the region of interest; and determining a radioactivity concentration based on the count rate within the region of interest.

[0017] According to the present disclosure, by introducing a function related to energy resolution in energy spectrum analysis, the Compton maximum energy for low-energy gamma rays can be accurately determined, thereby enabling the setting of an appropriate region of interest for various energies, thereby achieving a technical effect of improving the reliability of radiation inspection within the inspection subject.

[0018] FIG. 1 is an exemplary drawing showing the structure of a radiation inspection device according to one embodiment of the present disclosure.

[0019] FIG. 2 is an exemplary block diagram showing a system configuration including a radiation inspection device according to one embodiment of the present disclosure.

[0020] FIG. 3 is an exemplary flowchart illustrating a method for examining radioactivity in an inspection subject according to one embodiment of the present disclosure.

[0021] FIG. 4 is an exemplary graph showing the fitted energy versus Compton maximum energy relationship based on a resolution function according to one embodiment of the present disclosure.

[0022] FIG. 5 is an exemplary graph illustrating setting a region of interest in an energy spectrum according to one embodiment of the present disclosure.

[0023] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. First, when assigning reference numerals to components in each drawing, it should be noted that, where possible, identical components are assigned the same reference numerals even if they appear in different drawings. Furthermore, when describing the present invention, if a detailed description of a related, well-known structure or function is judged to obscure the gist of the present invention, such detailed description will be omitted.

[0024] Various aspects of the present invention are described below. It is to be understood that the inventions presented herein may be embodied in a wide variety of forms, and that any specific structure, function, or both presented herein are merely exemplary. Based on the inventions presented herein, one of ordinary skill in the art will appreciate that one aspect presented herein may be implemented independently of any other aspects, and that two or more of these aspects may be combined in various ways. For example, a device may be implemented or a method may be implemented using any number of the aspects described herein. Furthermore, such a device may be implemented or such a method may be implemented using structures, functions, or structures and functions other than or in addition to one or more of the aspects described herein.

[0025] FIG. 1 is an exemplary drawing showing the structure of a radiation inspection device (100) according to one embodiment of the present disclosure.

[0026] As illustrated in FIG. 1, a sample (110) to be inspected (e.g., aquatic products, etc.) can be introduced into a radiation inspection device (100) through a sample transfer table (120). A radiation detector (130) can detect radioactive materials present in the sample (110), and a scale (140) can measure the weight of the sample (110) and transfer it to the radiation inspection device (100). In another embodiment, the sample (110) can be provided to the radiation inspection device (100) in a preset quantity without having to measure the weight with the scale (140), or weight information of the sample (110) can be provided to the radiation inspection device (100) from an upper computing device.

[0027] The radiation inspection device (100) can determine the radioactive nuclides and radioactivity concentration present in the sample (100), as described later, and can be configured to display information including the detected nuclides and concentration and output an alarm when the determined radioactivity concentration is above a set alarm level.

[0028] FIG. 2 is an exemplary block diagram showing a system configuration including a radiation inspection device according to one embodiment of the present disclosure.

[0029] As illustrated in FIG. 2, a radiation inspection device (100) may include a radiation detector (130) and a controller (240). The radiation detector (130) may be configured to measure an energy spectrum of radiation generated from an inspection target (e.g., aquatic products, etc.). The controller (240) may be configured to determine a radioactive nuclide (e.g., Cs-137, I-131, etc.) based on the measured energy spectrum, determine a region of interest to apply to the measured energy spectrum according to the determined nuclide, determine a count rate within the region of interest, and determine a radioactivity concentration of the inspection target based on the determined count rate within the region of interest.

[0030] The radiation detector (130) may include a plastic scintillator (210), a photomultiplier tube (PMT) (215), a summing circuit (220), and a multi-channel analyzer (MCA) (230).

[0031] The plastic scintillator (210) may be, for example, a PVT scintillator, and may be configured to convert incident radiation generated from the inspection target (110) into light of a visible light wavelength. The PMT (215) may be configured to focus visible light from the PVT scintillator (210) and convert it into an electrical signal. The summing circuit (220) may sum the signals received from the PMT (215) and perform noise removal and amplification functions. The MCA (230) may be configured to process the electrical signal from the summing circuit (220) to generate an energy spectrum of incident radiation from the inspection target and transmit it to the controller (240).

[0032] The controller (240) may be a computing device for analyzing the energy spectrum measured by the radiation detector (130), and may be implemented as a personal computer (PC), a dedicated computing device for radiation inspection, etc. In addition, the controller (240) may be connected to a central control system (250) through a predetermined wired or wireless communication network, and may be configured to perform a radiation inspection of an inspection target according to a command from the central control system (250) and provide the inspection results (e.g., measurement completion signal, inspection pass / fail, radiation concentration, etc.) to the central control system (250).

[0033] In one embodiment, when the radiation inspection device (100) is implemented in manual mode, the radiation inspection device (100) may be equipped with a scale (140) for measuring the weight of the inspection target. In another embodiment, when the radiation inspection device (100) is implemented in automatic mode, the weight information of the inspection target sample may be provided from a central control system (250) or a preset quantity of the inspection target sample may be processed to enter the radiation inspection device (100).

[0034] FIG. 3 is an exemplary flowchart illustrating a method for examining radioactivity in an inspection subject according to one embodiment of the present disclosure.

[0035] As illustrated in FIG. 3, when an inspection subject (110) enters a radiation inspection device (100) (300), a radiation detector (130) measures the radiation within the inspection subject (100) for a preset time (e.g., 1 minute) (305), and (in manual mode) a scale (140) can measure the weight of the inspection subject (110) (310).

[0036] The controller (240) can determine the presence or absence of radioactive material based on the contamination suspicion criteria established based on the background values ​​measured by the radiation detector (130) (315). These contamination suspicion criteria can be expressed by the following formula:

[0037]

[0038] Here, k can be set based on the false alarm rate presented by ANSI (American National Standards Institute).

[0039] In step 315, if the criteria according to mathematical formula 1 are not satisfied, the controller (240) may determine that there is no radioactivity, output the inspection target (110), and terminate the radioactivity inspection. In step 315, if the criteria according to mathematical formula 1 are satisfied, the controller (240) may perform an analysis on the measured energy spectrum as described below.

[0040] The controller (240) can determine radioactive nuclides based on the measured energy spectrum (325). To this end, the controller (240) can be configured to determine radioactive nuclides by determining the similarity between the reference energy spectrum and the measured energy spectrum for each nuclide using the Maximum Likelihood Estimation (MLE) technique. For example, reference energy spectrum information for Cs-137, I-131, etc., which may be nuclides of interest for an inspection target (110) such as aquatic products, can be provided in advance, and the controller (240) can determine which nuclide among Cs-137, I-131, etc., exists in the inspection target (110) by comparing the measured energy spectrum with each of these reference energy spectra.

[0041] In one implementation example, reference energy spectrum information for a specific nuclide can be determined by applying a Monte Carlo computational simulation technique. For example, a radiation inspection device (100) can use a computational simulation utilizing a Monte Carlo N-Particle Transport (MCNP) code to obtain reference energy spectra for each nuclide, such as Cs-137 and I-131, when they exist in a test subject (e.g., aquatic food), and apply the obtained spectrum to determine radioactive nuclides.

[0042] Once the radioactive nuclide is identified in step 325, the controller (240) can determine a region of interest to apply to the measured energy spectrum based on the identified nuclide (330). To this end, the controller (240) can determine the region of interest based on the Compton edge energy, Compton maximum energy, and the resolution of the radiation detector (130) for the identified nuclide.

[0043] Compton edge energy refers to the highest energy that can be transmitted to the detector by complete backscattering during Compton scattering, and is a value that can be calculated according to a given formula using the peak energy of the corresponding nuclide.

[0044] Compton maximum energy can be determined to be identifiable depending on the resolution and energy range of the detector (130). For example, when measuring high-energy gamma rays, the Compton maximum energy can be accurately identified in the measured energy spectrum. However, when measuring relatively low-energy gamma rays, the resolution may be low, making it difficult to accurately identify the Compton maximum energy. Accordingly, the present disclosure proposes a method for determining Compton maximum energy for low-energy gamma rays based on the Compton maximum energy determined for high-energy gamma rays.

[0045] To this end, the radiation inspection device (100) can first determine the Compton maximum energy in high-energy gamma rays for a specific nuclide through computer simulation, and then use this to define a functional relationship to represent the Compton maximum energy in a low-energy region. The Compton maximum energy is a value that varies depending on the resolution of the detector (130), and the resolution of the detector (130) can be determined according to the following resolution function:

[0046]

[0047] Here, E represents the Compton edge energy or the gamma-ray energy absorbed by the detector (130), FWHM (Full Width at Half Maximum) represents the resolution of the detector (130) at the gamma-ray energy E, and a, b, and c may represent the degree of spread of a peak due to the corresponding gamma-ray energy within the spectrum. a, b, and c may be determined through Monte Carlo computational simulation of the radiation inspection device (100).

[0048] The radiation inspection device (100) can determine the fitted energy vs. Compton maximum energy relationship based on this resolution function, as illustrated in FIG. 4. As illustrated in FIG. 4, based on the resolution function defined in mathematical expression 2, a functional relationship can be determined with the Compton maximum energy corresponding to a relatively high energy region (approximately 0.5 to 1.0 MeV in the example of FIG. 4) as the X-axis and the Compton maximum energy corresponding to such energy region as the Y-axis. Accordingly, the controller (240) can determine the Compton maximum energy (also for a low energy region) according to the fitted energy vs. Compton maximum energy relationship based on this resolution function.

[0049] As described above, once the Compton edge energy, Compton maximum energy, and resolution of the detector (130) for the identified nuclide are determined, the controller (240) can determine the region of interest to apply to the measured energy spectrum as follows:

[0050]

[0051] Here, E CE is the Compton edge energy, and E CM is the Compton maximum energy, and FWHM is the resolution according to Equation 2.

[0052] FIG. 5 is an exemplary graph showing setting a region of interest (500) according to mathematical formula 3 in a measured energy spectrum.

[0053] Next, the controller (240) can remove the background signal (330) to evaluate the radioactivity due to the radioactive material present in the inspection target (110) and determine the count rate within the region of interest from which the background signal has been removed (335).

[0054] When the count rate within the region of interest is determined in step 335, the controller (240) can determine the radioactivity concentration (e.g., in Bq / kg units) based on the determined count rate, the gamma-ray emission rate of the determined nuclide, the detection efficiency of the inspection target (110), and the weight of the inspection target (110) (340).

[0055] Specifically, the controller (240) can determine the radioactivity concentration according to the following formula:

[0056]

[0057] Here, the count rate is the count rate determined in step 335, and the weight is the weight of the inspection target (110) measured in step 310. Y is a factor representing the gamma-ray emission rate of the determined nuclide, and ε is a factor representing the detection efficiency of the inspection target (110). The radiation inspection device (100) can determine the detection efficiency for each inspection target (e.g., each target marine product) (350) through a computer simulation of the inspection environment (e.g., Monte Carlo computer simulation) (345) and apply it to the determination of the radioactivity concentration according to mathematical expression 4.

[0058] The controller (240) can output the inspection target (110) and end the radiation inspection if the radioactivity concentration determined in step 340 is lower than the alarm level set for the determined nuclide (360). If the radioactivity concentration determined in step 340 is higher than the alarm level set for the determined nuclide, the controller (240) can output the determined nuclide and determined radioactivity concentration information along with an alarm signal (365). For example, the controller (240) can display that a concentration higher than the alarm level has been detected through its own display or to the central control system (250) and output the determined nuclide and determined radioactivity concentration. In addition, the controller (240) can be additionally configured to output a voice or other form of alarm signal through its own alarm device or to the central control system (250) when a concentration higher than the alarm level is detected.

[0059] It should be understood that any specific order or hierarchy of steps in any of the presented processes is merely an example of exemplary approaches. It should be understood that the specific order or hierarchy of steps in the processes may be rearranged within the scope of the present invention based on design priorities. The appended method claims present elements of various steps in an exemplary order, but are not intended to be limited to the specific order or hierarchy presented.

[0060] The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments disclosed herein, but is to be construed in the broadest scope consistent with the principles and novel features disclosed herein.

[0061] (Explanation of symbols)

[0062] 100: Radiation testing device

[0063] 110: Inspection subject

[0064] 120: Sample transfer table

[0065] 130: Radiation detector

[0066] 140: Scales

[0067] 210: PVT scintillator

[0068] 215: PMT

[0069] 220: Summing circuit

[0070] 230: MCA

[0071] 240: Controller

[0072] 250: Central Control System

Claims

1. As a device for testing radioactivity in the test subject, A radiation detector configured to measure the energy spectrum of radiation emitted from the inspection object; and A controller configured to determine a radioactive nuclide based on the measured energy spectrum, determine a region of interest to be applied to the measured energy spectrum according to the determined nuclide, determine a count rate within the region of interest, and determine a radioactivity concentration based on the count rate within the region of interest. A radiation inspection device, including:

2. In paragraph 1, The controller is further configured to output information on the determined radioactivity concentration and the determined radioactivity concentration together with an alarm signal when the determined radioactivity concentration is higher than the alarm level set for the determined radioactivity. Radiation testing device.

3. In paragraph 1, The above controller is configured to determine the radioactive nuclide by determining the similarity between the reference energy spectrum for each nuclide and the measured energy spectrum using the MLE (Maximum Likelihood Estimation) technique. Radiation testing device.

4. In paragraph 1, The control unit is configured to determine the region of interest based on the Compton edge energy, Compton maximum energy, and resolution of the radiation detector for the determined nuclide. Radiation testing device.

5. In paragraph 4, The above area of ​​interest is [E CM - FWHM / 2, E CE + FWHM / 2], and E CE is the Compton edge energy, and E CM is the Compton maximum energy, and FWHM is the resolution. Radiation testing device.

6. In paragraph 4, The resolution of the above radiation detector is determined by the following resolution function: E represents the Compton edge energy or the gamma-ray energy absorbed by the detector, FWHM represents the resolution of the detector at the gamma-ray energy E, and a, b and c represent the degree of spread of the peak by the gamma-ray energy within the spectrum. Radiation testing device.

7. In paragraph 5, The controller is configured to determine the Compton maximum energy according to a fitted energy-to-Compton maximum energy relationship based on the resolution function. Radiation testing device.

8. In paragraph 1, The controller is configured to determine a count rate within the region of interest from which the background has been removed, and to determine the radioactivity concentration based on the count rate, the gamma-ray emission rate of the determined nuclide, the detection efficiency of the inspection target, and the weight of the inspection target. Radiation testing device.

9. As a method for examining radioactivity in a subject of examination, A step of measuring the energy spectrum of radiation generated from the inspection subject; A step of determining a radioactive nuclide based on the measured energy spectrum; A step of determining a region of interest to be applied to the measured energy spectrum according to the above-determined nuclide; a step of determining a counting rate within the region of interest; and A step of determining the radioactivity concentration based on the count rate within the above region of interest. A method of radioactivity inspection, comprising:

10. In paragraph 9, Further comprising a step of outputting information on the determined nuclide and the determined radioactivity concentration together with an alarm signal when the determined radioactivity concentration is higher than the alarm level set for the determined nuclide. Radioactivity testing methods.

11. In paragraph 9, The step of determining the above radioactive nuclide is: A step of determining the radioactive nuclide by determining the similarity between the reference energy spectrum and the measured energy spectrum for each nuclide using the MLE technique, Radioactivity testing methods.

12. In paragraph 9, The step of determining the above area of ​​interest is: A step of determining the region of interest based on the Compton edge energy, Compton maximum energy, and resolution of the radiation detector for the determined nuclide, Radioactivity testing methods.

13. In paragraph 12, The above area of ​​interest is [E CM - FWHM / 2, E CE + FWHM / 2], and E CE is the Compton edge energy, and E CM is the Compton maximum energy, and FWHM is the resolution. Radioactivity testing methods.

14. In paragraph 12, The resolution of the above radiation detector is determined by the following resolution function: E represents the Compton edge energy or the gamma-ray energy absorbed by the detector, FWHM represents the resolution of the detector at the gamma-ray energy E, and a, b and c represent the degree of spread of the peak by the gamma-ray energy within the spectrum. Radioactivity testing methods.

15. In paragraph 14, The above Compton maximum energy is determined according to the fitted energy to Compton maximum energy relationship based on the above resolution function. Radioactivity testing methods.

16. In paragraph 9, The step of determining the above radioactivity concentration is: A step of determining the count rate within the region of interest from which the background has been removed; and A step of determining the radioactivity concentration based on the counting rate, the gamma ray emission rate of the determined nuclide, the detection efficiency of the inspection target, and the weight of the inspection target, Radioactivity testing methods.

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