Apparatus and Method of identifying gamma nuclides

Abstract

The present invention provides a gamma ray radionuclide identification apparatus and method that enables rapid and accurate detection of gamma ray radionuclides by applying a function of temperature peak change and a function of temperature resolution change of a gamma ray spectrum regarding the temperature effect of a spectrometer measuring gamma rays to a gamma ray radionuclide identification algorithm.

Description

Technology Field

[0001] The present invention relates to a gamma nuclide identification apparatus and method for identifying gamma nuclides by correcting for changes in peak shift and resolution of the gamma ray spectrum according to temperature. Background Technology

[0002] Scintillator-based radiation detectors are affected by temperature in their gamma ray spectrum signals.

[0003] A scintillator-based radiation spectrometer acquires detected radiation as an electrical pulse signal. The acquired radiation pulse signal is converted into a digital signal channel to form an energy spectrum. At this time, as the characteristics and properties of the scintillator and the collecting sensors change depending on the temperature, the height of the acquired signal pulse changes, and the shape of the spectrum changes according to the temperature.

[0004] Therefore, when identifying gamma nuclides with a spectrometer, since identification is fundamentally based on the shape of the spectrum, it is necessary to identify gamma nuclides by considering the shape of the spectrum according to temperature.

[0005] Korean Patent Publication No. 10-2015-0120205 discloses a portable radiation detection device and a method thereof, wherein temperature compensation for each temperature range is performed based on correction values ​​set differently for each temperature range in radiation detection.

[0006] Korean Registered Patent No. 10-1762008 discloses a radiation detection device and a detection method that repeatedly measures the spectrum of an ambient temperature and a mixed source in a radiation detection environment, and obtains and calibrates an energy correction function from the spectrum of the ambient temperature and the mixed source.

[0007] Mariscotti, M. disclosed in a 1967 paper that a gamma-ray spectrum is read to find peaks and to determine amplitude, center, and width through minimum-order fitting.

[0008] However, conventional technology has not presented an improved algorithm for changes in the shape and resolution of gamma-ray spectra depending on temperature.

[0009] Furthermore, while conventional technology proposes methods to compensate for or minimize spectral changes due to temperature, such methods are limited to peak shifts and do not consider changes in peak resolution. Prior art literature

[0010] Korean Registered Patent No. 10-1762008 "Radiation Detector Device and Detector Method" Korean Published Patent No. 10-2015-0120205 "Portable Radiation Detector Device and Method Thereof"

[0011] Mariscotti, MA "A method for automatic identification of peaks in the presence of background and its application to spectrum analysis." Nuclear Instruments and Methods 50.2 (1967): 309-320. The problem to be solved

[0012] The present invention provides a gamma-ray radionuclide identification apparatus and method that enables rapid and accurate identification of gamma-ray radionuclides by applying a peak change function and a resolution change function regarding the temperature effect of a small spectrometer to a gamma-ray radionuclide identification algorithm.

[0013] Another objective of the present invention is to provide a portable gamma-ray radionuclide identification device and method that enables the detection and identification of radionuclides in real time at sites with varying temperatures, regardless of temperature, and the presence of radioactive materials or isotopes.

[0014] The problems solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0015] An embodiment provides a gamma ray radionuclide identification device comprising: a gamma ray detector that converts gamma rays emitted from a gamma ray source into a gamma ray spectrum of an electrical signal and outputs it; and a signal processing unit that detects the maximum peak and energy of the gamma rays by applying a temperature peak shift change function and a temperature resolution change function to the electrical signal corresponding to the gamma rays output from the gamma ray detector, and then identifies and outputs a radionuclide corresponding to the gamma rays.

[0016] An embodiment is a method for identifying gamma-ray nuclides using the gamma-ray nuclide identification device, comprising: a calibration step of deriving a channel energy correlation function (y(E)) and a channel resolution correction function (y(R)) of a gamma-ray spectrum using a standard radiation source; and a temperature peak shift change function (C) using the gamma-ray spectrum emitted from the standard radiation source. E ) and temperature resolution change function (C R A method for identifying gamma-ray nuclides is provided, comprising: a step of deriving a temperature change function to derive ); and a step of identifying gamma-ray nuclides by applying a peak shift and a spectrum change and a resolution change according to the temperature to a gamma-ray spectrum emitted from a gamma-ray nuclide to be identified, thereby detecting the energy of the gamma-ray spectrum, and applying the detected energy to a gamma-ray nuclide library to identify the gamma-ray nuclide. Effects of the invention

[0017] An embodiment of the present invention enables rapid and accurate verification of the temperature-dependent peak shift and resolution changes of gamma rays by applying a temperature peak shift change function representing the temperature-dependent peak change of standardized gamma rays for gamma ray nuclide identification, and a temperature resolution change function representing the temperature-dependent change of the resolution required for peak search.

[0018] An embodiment of the present invention enables the gamma ray detector to be manufactured in a compact size, thereby making it possible to manufacture a portable gamma ray radionuclide identification device. Due to this characteristic, a spectrometer can be applied as a radioisotope identification device, enabling the fabrication of a portable gamma ray detector.

[0019] Accordingly, embodiments of the present invention enable the rapid and accurate detection of the energy of channels having gamma ray peaks and maximum center peaks by reflecting changes in peak shift and resolution according to temperature when identifying gamma ray nuclides.

[0020] In addition, embodiments of the present invention can enable accurate gamma-ray radionuclide identification regardless of ambient temperature changes when applied to radionuclide identification in an outdoor environment. Brief explanation of the drawing

[0021] FIG. 1 is a configuration diagram of a gamma ray radionuclide identification device (1) of an embodiment of the present invention. Figure 2 is a flowchart showing the processing steps of the gamma-ray radionuclide identification method of an embodiment of the present invention. Figure 3 is a flowchart showing the detailed processing steps of the gamma ray radionuclide identification step (S40) of Figure 2. Figure 4 is a diagram showing code for executing the gamma-ray radionuclide identification step (S40) of Figures 2 and 3, implemented in the C language. Figure 5 is a graph showing the correlation between the channel and energy. Figure 6 is a graph showing the correlation between the channel and the resolution. Figures 7 to 9 are graphs showing the gamma ray spectra of Ba-133, Am-241, and Cs-137 at different temperatures, respectively. Figure 10 is a graph showing the relative change in the position of the gamma ray spectrum peaks according to temperature. Figure 11 is a graph showing the relative change in gamma ray spectrum peak resolution according to temperature. Specific details for implementing the invention

[0022] Specific structural or functional descriptions of embodiments according to the concept of the present invention disclosed herein are provided merely for the purpose of explaining embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms and are not limited to the embodiments described herein.

[0023] Embodiments according to the concept of the present invention may be subject to various modifications and may take various forms; therefore, embodiments are illustrated in the drawings and described in detail in this specification. However, this is not intended to limit the embodiments according to the concept of the present invention to specific disclosed forms, and includes modifications, equivalents, or substitutions that fall within the spirit and scope of the present invention.

[0024] Terms such as "first" or "second" may be used to describe various components, but said components should not be limited by said terms. For the sole purpose of distinguishing one component from another, for example, without departing from the scope of rights according to the concept of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0025] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. Conversely, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between. Expressions describing the relationships between components, such as "between," "exactly between," or "directly adjacent to," should be interpreted in the same way.

[0026] The terms used herein are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0027] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0028] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, the scope of the patent application is not limited or restricted by these embodiments. Identical reference numerals in each drawing indicate identical components.

[0029] FIG. 1 is a configuration diagram of a gamma ray radionuclide identification device (1) of an embodiment of the present invention.

[0030] As shown in FIG. 1, the gamma ray radionuclide identification device (1) may be configured to include a gamma ray detection unit (10) and a signal processing unit (20).

[0031] The above gamma ray detector (10) may be configured to convert and output a scintillation generated in response to gamma rays emitted from a gamma ray source (S) into an electrical signal.

[0032] To this end, the gamma ray detection unit (10) may be configured to include a scintillation element (110), a temperature sensor (115), an optical coupler (130), a photodetector (140), and a first amplifier (150).

[0033] The scintillation element (110) may be made of an inorganic scintillator material that generates a scintillation as electrons are excited by the gamma rays and return to a low energy level. In an embodiment of the present invention, the scintillation-generating material may be one or more selected from the group consisting of HPGe (High Purity Germanium), NaI, NaI(Tl), CsI(Tl), CsI(Na), BGO, and mixtures thereof.

[0034] The temperature sensor (115) may be installed at an adjacent location to the scintillation element (110) and configured to measure and provide the ambient temperature when gamma rays are detected.

[0035] The reflector (120) may be installed around the scintillation element (110) and configured to reflect the scintillation generated from the scintillation element (110) toward the optical coupler (130). The reflector (120) may be made of a highly reflective material such as a mirror, a silver thin film, or an aluminum thin film.

[0036] The optical coupler (130) may be installed on the surface of the scintillation element (110) where the reflector (130) is not installed, and configured to transmit the scintillation generated from the scintillation element (110) and the scintillation reflected from the reflector (120) to the photodetector (140). The optical coupler (130) may be made of an optical waveguide or optical fiber, etc., in which a high-reflection waveguide is formed inside.

[0037] The photodetector (140) may be installed at the end of the photocoupler (130) located on the opposite side of the scintillation element (110). The photodetector (140) may be configured to generate a gamma-ray spectrum of an electrical signal in response to the scintillation transmitted from the photocoupler (130). To this end, the photodetector (140) may include a photodiode. The photodetector (140) may include one or more SiPMs (Silicone Photomultipliers).

[0038] The first amplifier (150) may be configured to convert an electrical signal corresponding to the gamma ray spectrum detected by the photodetector (140) into a voltage signal. The first amplifier (150) may be a preamplifier. The preamplifier may convert the electrical signal into a voltage signal proportional to the charge amount corresponding to the electrical signal. The voltage signal may have a voltage of several to tens of mV. By doing so, the output impedance of the first amplifier (150) can be kept low so that the voltage signal is transmitted to the signal processing unit (20) without signal loss and so that noise caused by the connected signal cable does not occur.

[0039] The optical coupler (130), the photodetector (140), and the preamplifier (150) may be manufactured to be integrally mounted on a first substrate (151) to which an electric cable (C) is connected. The electric cable (C) may be a flat flexible cable. The first substrate (151) on which the optical coupler (130), the photodetector (140), and the preamplifier (150) are mounted may be integrally mounted on a surface (126) in which an opening is formed of a first case (125) in which the scintillation element (110) and the reflector (120) are embedded and sealed.

[0040] The signal processing unit (20) may be configured to receive a voltage signal corresponding to a detected gamma ray transmitted from the gamma ray detection unit (10), perform signal processing, and identify and output a gamma ray nuclide corresponding to the gamma ray. The signal processing is a temperature peak shift change function (C f ) and temperature resolution change function (C R It may be a signal processing method that calculates the peak shift value and resolution change value due to temperature by applying ).

[0041] The above resolution is the spacing between peaks, representing the ability to distinguish adjacent peaks. The above resolution is the value obtained by dividing the Full Width Half Maximum (FWHM) of a peak by the median energy of the channel. The smaller the above value, the better the ability to distinguish peaks.

[0042] The above signal processing may be a signal processing that calculates the maximum peak and energy of the gamma ray by applying the peak shift value and resolution change value due to the temperature, identifies the corresponding gamma ray nuclide, and outputs the identified gamma ray nuclide information.

[0043] To this end, the signal processing unit (20) may be configured to include a cable socket (210), a second amplifier (210), an AD converter (ADC) (230), an arithmetic unit (240), a storage device (250), and a communication module (255).

[0044] The above cable socket (210) can be configured to connect the end of the electric cable (C) located on the side of the signal processing unit (20).

[0045] The second amplifier (210) may be a linear amplifier that receives and shapes the voltage signal through the electric cable (C), and linearly amplifies it by improving the signal-to-noise ratio (S / N). The shaping may be Gaussian shaping. The linearly amplified voltage signal may be amplified to have a voltage range of 20V or less and exceeding several volts.

[0046] The above AD converter (230) may be configured to receive the linearly amplified analog voltage signal from the second amplifier (210), convert it into a digital voltage signal for signal processing by the arithmetic unit (240), and output it.

[0047] The above-mentioned calculator (240) may be configured to receive the digital voltage signal corresponding to the gamma ray spectrum, divide it by peak, and store it for each channel. The channel is the peak position of the gamma ray spectrum.

[0048] The above-described calculator (240) may be configured to perform operations such as energy and resolution correction for a digital voltage signal corresponding to the stored gamma ray spectrum, temperature-dependent spectrum acquisition and temperature change function derivation, spectrum flattening, detection of gamma ray peak shift value and resolution conversion value with the temperature change function applied, and gamma ray radionuclide identification, and output.

[0049] The above temperature change function is a temperature peak shift change function (C E ) and temperature resolution change function (C R It can be.

[0050] The above temperature peak shift change function (C E ) may be a function that derives a peak shift in the spectrum according to temperature during gamma ray measurement by the gamma ray detector (10).

[0051] The above temperature resolution change function (C R ) may be a function that derives the change in resolution within the spectrum according to the temperature during gamma ray measurement by the gamma ray detector (10).

[0052] The above-mentioned arithmetic unit (240) may be configured as a Field Programmable Gate Array (FPGA).

[0053] The above storage device (250) may be configured to store a gamma ray nuclide library, in which energy values ​​corresponding to the peaks of gamma rays radiated by each gamma ray nuclide according to temperature are stored, as a gamma ray nuclide table. For example, the above storage device (250) may be configured as a non-volatile memory device.

[0054] [Table 1] shows an example of the above gamma ray nuclide table.

[0055] Gamma ray radionuclide table radionuclide Energy (MeV) A-1 Ea A-2 Ec B-1 Eb B-2 Ed C-1 Ee E Ef F-1 Eg C-2 Eh F-2 Ei G Ej ... ...

[0056] A gamma-ray nuclide may emit gamma rays having one or more peaks. The gamma-ray nuclide table may store a single energy value corresponding to a gamma-ray nuclide having one peak, and store energy values ​​corresponding to two or more peaks for a gamma-ray nuclide having two or more peaks. In the gamma-ray nuclide table, A-1 and A-2 may be information for gamma-ray nuclide A having energies Ea (MeV) and Ec (MeV) corresponding to two peaks including a maximum peak. B-1 and B-2 may be gamma-ray nuclides B having energies Eb (MeV) and Ed (MeV) corresponding to two peaks including a maximum peak. E and G may be gamma-ray nuclides emitting gamma rays having a single peak and single energies Ef (MeV) and Ej (MeV), respectively.

[0057] The above-described calculator (240) may be configured to compare the energies corresponding to the calculated gamma ray peaks with a plurality of energies stored in the gamma ray nuclide table, and to identify a gamma ray nuclide in which one or more energies match as a target gamma ray nuclide. That is, since the present invention identifies a gamma ray nuclide by applying energies corresponding to a plurality of peaks emitted from a single gamma ray nuclide, the accuracy of gamma ray nuclide identification can be improved.

[0058] The communication module (255) may be configured to provide a communication interface that enables the signal processing unit (20) to perform wired or wireless communication with an external device such as the external control unit (30). The communication module (255) may be configured to perform communication with an external device including the external control unit (30) through wired communication such as USB, USB-C, RS-45, and wireless short-range communication such as Wi-Fi, Bluetooth, and infrared communication.

[0059] The above cable socket (210), second amplifier (220), AD converter (230), arithmetic unit (240), storage device (250), and communication module (255) can be integrally mounted on a second substrate (260) on which a circuit pattern is formed, and then sealed inside a second case (270).

[0060] The above external control unit (30) may be an IT device or computer device equipped with a user interface that controls the operation of the signal processing unit (20) and outputs the result of the operation.

[0061] The above user interface may be configured to input data and commands, display the operating status, and display output results so that the signal processing unit (20) can perform calculations for gamma ray nuclide identification.

[0062] The above IT device may be a mobile phone, a tablet with mobile communication capabilities, etc.

[0063] The above computer device may be a laptop or PC capable of mobile communication. The above IT device may be configured as an independent control device capable of mobile communication so as to be portable, equipped with a user interface for external control of the signal processing unit (20).

[0064] Figure 2 is a flowchart showing the processing steps of the gamma-ray radionuclide identification method of an embodiment of the present invention.

[0065] As shown in FIG. 2, the gamma-ray nuclide identification method of the embodiment may include a calibration step (S10), a temperature change function derivation step (S20), a spectrum smoothing step (S30), and a gamma-ray nuclide identification step (S40).

[0066] The above calibration step (S10) may be a step of performing channel energy calibration and channel resolution calibration for a gamma ray spectrum for the application of the gamma ray radionuclide identification method of the present invention. The energy of the gamma ray may be the lower area of ​​the channel.

[0067] In practice, during peak searching in radionuclide identification algorithms, the peak location is determined by moving by a value less than the channel resolution (approximately (resolution size) / 2) to find the peak maximum. Since the resolution varies with temperature, this must be taken into account. As the resolution can decrease or increase with temperature, failing to account for this during peak searching may result in the inflection point information (peak center) not being found. For this reason, channel resolution correction is required.

[0068] The above channel energy correction may involve deriving a channel energy correlation function (y(E)), which is a correlation function of gamma ray energy for the channel at the peak position of the gamma ray spectrum.

[0069] The above resolution correction may involve deriving a channel resolution correction function (y(R)) which is a correlation function between the channel width and gamma ray energy corresponding to the peak position of the gamma ray spectrum.

[0070] The above channel energy correlation function (y(E)) and channel resolution correction function (y(R)) can be calculated by applying the least squares regression method, etc., after measuring gamma rays using a well-known gamma ray nuclide as a standard radioactive source.

[0071] The above channel energy calibration and the above channel resolution calibration may be calculated by applying a least squares regression method, etc., to the channel energy correlation function and the channel resolution calibration function as calibration formulas after measuring the gamma rays emitted from the above standard radiation sources.

[0072] The above temperature change function derivation step (S20) may be a step of obtaining gamma ray spectra emitted from a gamma ray source (S) for each gamma ray nuclide and temperature, and then deriving information on peak shift and spectrum shape change according to temperature in the gamma ray spectra as a function.

[0073] The above temperature-dependent peak shift change function is the temperature peak shift change function (C E It may be ). The above temperature peak shift change function (C E ) can be expressed as [Mathematical Formula 1].

[0074]

[0075] Here, c is 20.00 to 20.48, d is 11.00 to 11.80, f is 0.020 to 0.038, and T is the temperature of the gamma ray detector (10). .

[0076] The above temperature-dependent resolution change function is the temperature resolution change function (C R It may be ). The above temperature resolution change function (C R ) can be expressed as [Mathematical Formula 2].

[0077]

[0078] Here, g is 1.050 to 1.060, h is 0.010 to 0.024, k is 0.0120 to 0.0126, l is 7.300 to 7.326, m is 4.095 to 5.005, and T is the temperature (°C) of the gamma ray detector (10).

[0079] The spectrum flattening step (S30) may be a step for removing statistical noise to apply the acquired temperature-specific spectrum data to the gamma-ray nuclide identification step (S40). The spectrum flattening step (S30) may be performed by a flattening mathematical technique that applies a flattening filter type, iterations, and points. Depending on the characteristics of the measuring instrument (resolution, measurement efficiency and measurement time, amplifier amplification rate, number of channels, etc.) and the purpose of use, an appropriate flattening mathematical technique (smoothing filter type, iterations, points) may be selected and applied in the spectrum flattening step (S30). The spectrum flattening step (S30) may also be applied to the first and second derivative values ​​and variance values ​​of the spectrum.

[0080] The above gamma ray radionuclide identification step (S40) includes the temperature T (°C) of the gamma ray detector (10) at the time of gamma ray detection, the channel energy correction function (y(E)), the channel resolution correction function (y(R)), and the temperature peak shift change function (C) in the gamma ray spectrum detected by the gamma ray detector (10). E ) and the above temperature resolution change function (C R It may be a step of identifying and outputting a gamma ray nuclide corresponding to the detected gamma ray by applying ).

[0081] Figure 3 is a flowchart showing the detailed processing steps of the gamma ray radionuclide identification step (S40) of Figure 2.

[0082] As shown in FIG. 3, the gamma-ray nuclide identification step (S40) may include a peak detection step (S41), a channel calculation step (S43), an energy calculation step (S45), and a gamma-ray nuclide derivation step (S47).

[0083] The peak detection step (S41) may be a step of searching for a peak of a gamma ray channel by distinguishing it from a noise peak in the gamma ray spectrum emitted from the identified target gamma ray nuclide. Specifically, the peak detection step (S410) may be a step of searching for a peak having gamma ray nuclide information by distinguishing it from a noise peak through differential operation on the spectrum corresponding to the acquired gamma ray.

[0084] The above channel calculation step (S43) may be a step of calculating a peak center channel corresponding to the center of a peak by performing a peak search for a resolution size of the position of the channel corresponding to the detected peak.

[0085] The energy calculation step (S45) above may be a step of calculating and outputting the peak center channel calculated in the channel calculation step (S43) as energy. The energy may be the lower area of ​​the peak center channel obtained by integrating the peak center channel.

[0086] The above gamma ray nuclide derivation step (S47) may be a step of identifying and outputting a gamma ray nuclide having an energy corresponding to the peak center channel from a gamma ray nuclide library stored in the storage device (250) as a gamma ray nuclide corresponding to the detected gamma ray. At this time, if there are multiple energies corresponding to the peak center channel, the gamma ray nuclides having multiple energies may be identified and output as the gamma ray nuclides.

[0087] <Example>

[0088] 1. Hardware and Software Configuration

[0089] A small, portable gamma-ray radionuclide identification device (1) was fabricated by applying CsI(Tl) as the scintillation element (110) of Fig. 1 and SiPMs as the photodetector (140) so that a gamma-ray spectrum can be obtained while carrying it.

[0090] FIG. 4 is a diagram showing an algorithm for executing the gamma-ray radionuclide identification step (S40) of FIG. 2 and FIG. 3 to be implemented in the C language.

[0091] The signal processing unit (20) uses the channel energy correlation function (y(E)), channel resolution correction function (y(R)), and temperature peak shift change function (C) of [Equation 3] to [Equation 2] to identify gamma ray nuclides. E ) and temperature resolution change function (C R It was configured as an FPGA that executes C language code implementing the algorithm of Fig. 4 with the applied.

[0092]

[0093] To identify gamma-ray nuclides, a gamma-ray nuclide table for the 63 types of gamma-ray nuclides in [Table 2] above was stored in the storage device (250) as a gamma-ray nuclide library.

[0094] The signal processing unit (20) compares the energy derived after executing the C language code with the energy of the gamma ray nuclide table to identify the gamma ray nuclide corresponding to the detected gamma ray.

[0095] 2. Correction step (S10)

[0096] A total of 7 data points were obtained using gamma rays of 59.4 keV for Am-241, 88.04 keV for Cd-109, 356.02 keV for Ba-133, 662.62 keV for Cs-137, 834.85 keV for Mn-54, 1,274.53 keV for Na-22, and 1,332.50 keV for Co-60 with a gamma ray identification device (1) manufactured for performing the calibration step (S10).

[0097] To derive the correlation functions between channel and energy, and channel and resolution, energy and resolution information for peak positions within the spectrum were derived and graphed.

[0098] Figure 5 is a graph showing the correlation between the channel and energy, and Figure 6 is a graph showing the correlation between the channel and resolution.

[0099] A channel energy correlation function (y(E)) and a channel resolution correction function (y(R)) were derived by applying a fitting method based on least squares regression to the energy and resolution information for peak positions derived from the graphs of Figures 5 and 6.

[0100] The above channel energy correlation function (y(E)) can be expressed as [Equation 3].

[0101]

[0102] Here, y(E) is the energy of the gamma ray corresponding to the channel (MeV), x is the number of channels, a is 999.299±2.56, and b is 14.54±0.84.

[0103] The above channel resolution correction function (y(R)) can be expressed as [Equation 4].

[0104]

[0105] Here, y(R) is the rate of change of channel resolution (%), x is the number of channels, a is 1.7646±0.2792, and b is -0.45564±0.0239.

[0106] 3. Derivation of temperature change function step (S20)

[0107] To identify the measured gamma-ray nuclides, the peak positions and resolution (the spacing between peaks) of the gamma-ray spectrum are required. Therefore, a temperature peak shift change function (C) representing the shift or change of gamma-ray spectrum peaks with respect to temperature is needed. E ) and temperature resolution change function (C R Gamma ray spectrum data by temperature was acquired to derive ).

[0108] Measurements were performed by applying a gamma ray source and a gamma ray radionuclide identification device (1) having the structure of <Example> 1. hardware and software configuration at each stable temperature in 10 ℃ intervals from -20, -10, 0, 10, 20, 30, 40, 50 ℃.

[0109] The gamma ray sources used were standard radioactive sources of Cs-137, Ba-133, and Am-241, and gamma ray spectrum measurements were performed three times for 10 minutes for each gamma ray source at different temperatures.

[0110] Figures 7 to 9 are graphs showing the gamma ray spectra of Ba-133, Am-241, and Cs-137 at different temperatures, respectively.

[0111] As shown in Figures 7 to 9, the ratio of gamma ray spectrum shift and resolution change according to temperature was the same in all channels.

[0112] Using the gamma ray spectra according to temperature in Figures 7 to 9 above, a graph of the relative change in the resolution magnitude of the peak position according to temperature at 20 ℃ was obtained.

[0113] Figure 10 is a graph showing the relative change in the position of the gamma ray spectrum peaks according to temperature. Figure 11 is a graph showing the relative change in the gamma ray spectrum peak resolution according to temperature.

[0114] In Figures 10 and 11, the error bar is the standard deviation of the mean of three measurements.

[0115] Using the graphs of FIGS. 10 and 11 described above, the temperature peak shift change function (C E ) and temperature resolution change function (C R ) was derived.

[0116] The derived temperature peak shift change function (C E ) is represented by [Mathematical Formula 5].

[0117]

[0118] The derived temperature resolution change function (C R ) was expressed as [Mathematical Formula 6].

[0119]

[0120] In [Equation 5] and [Equation 6], T is the temperature at the time of gamma ray measurement ( )am.

[0121] 4. Spectrum flattening step (S30)

[0122] For spectrum flattening, filters such as SG (Savitzky-Golay method) 4th-order polynomial smoothing, SG 2nd-order polynomial smoothing for the 1st-order derivative of the spectrum, Gaussian smoothing for the 2nd-order derivative of the spectrum, SG 2nd-order polynomial smoothing, and Gaussian smoothing for the 2nd-order derivative of the spectrum were applied to the detected gamma-ray spectra to perform flattening.

[0123] 5. Gamma-ray radionuclide identification step (S40)

[0124] Subsequently, the gamma ray radionuclide identification step (S40) of FIG. 3 was implemented using the C language code of FIG. 4. The implemented C language code of the gamma ray radionuclide identification step (S40) was programmed and executed on an arithmetic unit (240) implemented on an FPGA to perform radionuclide identification for the measured gamma rays.

[0125] The C language code executed in the above-mentioned calculator (240) periodically receives gamma ray spectrum data (n) and temperature values ​​(T) detected through the gamma ray detection unit (10) and signal processing unit (20) of the gamma ray radionuclide identification device (1) as input values ​​at regular intervals, and performs identification of gamma ray radionuclides through multiple calculations. At this time, the temperature (T) is obtained from the temperature sensor (115) equipped in the gamma ray detection unit (10).

[0126] The variables in Figure 4 are as follows.

[0127] T: Temperature (scintill temperature) (°C), n(i): Spectral function, n'(i): First derivative of n(i), n(i): Second derivative of n(i), i: Number of channels (peak position), imax: Maximum number of channels (maximum channel position), j: Maximum peak position, P: Peak center channel, σ(i): Standard deviation, σ(i) 2 : Variance, s: Peak search sensitivity, y(R): Channel resolution correction function y(R)=a*x b , y(E): As the channel energy correlation function, y(E) = a*x + b, C E (Refer to Equation 5): Function of temperature peak shift change (function of relative change in peak position with respect to temperature), C R (Refer to Equation 6): Function of change in temperature resolution (function of relative change in resolution with respect to temperature).

[0128] The gamma-ray nuclide identification step (S40) of Fig. 4 is explained in more detail.

[0129] To perform the peak detection step (S41) of Fig. 3, after receiving gamma ray spectrum data (n(i)) and temperature value (T), a peak containing gamma ray nuclide information was detected by distinguishing it from noise peaks in the detected gamma ray spectrum through differential operation.

[0130] Steps S410 to S435 of FIG. 4 correspond to the peak detection step (S41) of FIG. 3.

[0131] The peak detection step (S41) is explained in more detail with reference to FIG. 4.

[0132] Steps S410 and S415 of FIG. 4 assign 1 to the channel count increment variable i, and then i is i max Increment by 1 until it reaches. Here, i is the channel number of the detected gamma-ray spectrum, and i max may be the maximum channel number of the above gamma ray radionuclide identification device (1).

[0133] Next, step S420 is performed so that if the second derivative value n(i) of the gamma ray spectrum is greater than the second derivative product of the peak search sensitivity s and the standard deviation σ(i), and n(i) (post-channel value) is smaller than n(i-1) (pre-channel value), it is recognized as a meaningful gamma ray peak and the next step is performed. At this time, s can be set to an appropriate value depending on the type of gamma ray detector and the measurement environment.

[0134] If, in step S420 above, the condition is not satisfied that the second derivative value n(i) of the gamma ray spectrum is greater than the second derivative product of the peak search sensitivity s and the standard deviation σ(i) and n(i) is less than n(i-1), return to step S415 above and repeat the processing while increasing i by 1.

[0135] Step S425 assigns 1 to a new channel variable j, which is incremented by 1 within the channel containing the recognized peak, when the recognized peak is recognized as a valid gamma ray peak in Step S420.

[0136] Step S430 involves deriving the resolution by using a new channel value j that is half the size of the Full-width-Half-Maximum (Rxi) channel size corresponding to that channel location (y(R)*i*C R It is repeatedly determined whether (T) / 2) has been reached.

[0137] If the condition of step S430 is not satisfied, step S433 is performed to update i to the sum of the recognized peak i and the above j, and then the process is repeated by returning to step S410.

[0138] If the condition of step S430 is satisfied, step S435 is performed to determine whether n'(i+j-1) of the first derivative of the gamma ray spectrum n(i) is greater than 0 and n'(i+j) is less than 0, thereby determining whether it is a maximum point.

[0139] If the condition of step S435 is not satisfied, perform step S440, increase the value of j by 1, then return to step S430 and repeat the processing.

[0140] If the condition of step S435 is satisfied, steps S450 and S455 of Fig. 4, corresponding to the channel calculation step (S43) of Fig. 3, are performed.

[0141] First, step S450 is performed to update i to the sum of the initially recognized peak position i and j. Next, the updated i is received in step S455 to calculate the peak center channel (P). The peak center channel (P) can be calculated more accurately using the first derivative zero-cross method of n(i). That is, as in step S455, the peak center channel (P) can be calculated by P = i - 1 + n'(i-1) / (n'(i - 1) - n'(i)).

[0142] After the peak center channel (P) is calculated by step S455, step S460 of Fig. 4, corresponding to the energy calculation step (S45) of Fig. 3, is performed.

[0143] Step S460 calculates the value of the calculated peak center channel (P) using the gamma ray energy calculation formula E=a*P / C E The gamma ray energy (E) is calculated by applying it to (T)-b. Here, a and b are the slope and y-intercept of the channel energy correlation function (y(E)) of [Equation 3], respectively.

[0144] After the energy of the gamma ray is calculated in step S460, step S465 of Fig. 4 is performed, which corresponds to the gamma ray nuclide derivation step (S47) of Fig. 3.

[0145] Step S465 of Fig. 4 compares the gamma ray energy calculated in Step S460 with the gamma ray energy of the gamma ray nuclide table set by the method of [Table 1].

[0146] Generally, gamma-ray nuclides emit gamma rays having one or more intrinsic energies. Therefore, the gamma-ray nuclide table, in which the energies of one or more gamma rays are matched for each gamma-ray nuclide, can be stored as a gamma-ray nuclide library in the storage device (250). At this time, the gamma-ray energies for each gamma-ray nuclide can be arranged in descending order according to their intensity. By doing so, it is possible to accurately identify gamma-ray nuclides by comparing the energies of multiple gamma-ray peaks included in a single gamma-ray spectrum.

[0147] To explain using [Table 1] as an example, [Table 1] defines a library of nuclides having energies of Ea MeV, Eb MeV, Ec MeV, and Ed MeV. In this case, A-1 and A-2 may be gamma-ray nuclides A that emit gamma rays with different gamma ray energies of Ea MeV and Ec MeV. B-1 and B-2 may be gamma-ray nuclides B that emit gamma rays with different gamma ray energies of Eb MeV and Ed MeV.

[0148] That is, by defining two or more energies for each gamma-ray nuclide, when all defined energies are detected, the gamma-ray nuclide can be identified and output as the gamma-ray nuclide corresponding to the detected gamma ray.

[0149] At this time, it is desirable that the energy of each gamma-ray nuclide recorded in the gamma-ray nuclide library be defined as a range of energy defined for each gamma-ray nuclide. This is because the identified energy may not exactly match the energy defined in the gamma-ray nuclide library. In addition, by setting the gamma-ray energy emitted by the gamma-ray nuclide as an energy range, the gamma-ray nuclide can be identified with two or more energies even if there is an overlapping range with the energy of other gamma-ray nuclides, thereby increasing the accuracy of gamma-ray nuclide identification. Explanation of the symbols

[0150] S: Gamma ray source C: Electric cable 1: Gamma-ray radionuclide identification device 10: Gamma ray detector 110: Scintillation 115: Temperature sensor 120: Reflector 125: Case 127: Surface with an opening 130: Optical coupler 140: Photodetector 150: First amplifier (preamplifier) 151: First substrate 20: Signal processing unit 210: Cable socket 220: Second amplifier 230: AD Converter 240: Arithmetic unit 250: Storage device 255: Communication module 260: Second substrate 270: Second case 30: External control unit

Claims

Claim 1 A gamma ray detector that converts gamma rays emitted from a gamma ray source into a gamma ray spectrum of an electrical signal and outputs it; and a temperature peak shift change function (C) for the gamma ray spectrum output from the gamma ray detector. E ) and temperature resolution change function (C R It includes a signal processing unit that detects the maximum peak and energy of the gamma ray spectrum by applying ) and then identifies and outputs a nuclide corresponding to the gamma ray, and the temperature peak shift change function (C E )Is, A gamma ray radionuclide identification device characterized in that, where c is 20.00 to 20.48, d is 11.00 to 11.80, f is 0.020 to 0.038, and T is the temperature of the gamma ray detector. Claim 2 delete Claim 3 A gamma ray detector that converts gamma rays emitted from a gamma ray source into a gamma ray spectrum of an electrical signal and outputs it; and a temperature peak shift change function (C) for the gamma ray spectrum output from the gamma ray detector. E ) and temperature resolution change function (C R It includes a signal processing unit that detects the maximum peak and energy of the gamma ray spectrum by applying ) and then identifies and outputs a nuclide corresponding to the gamma ray, and the temperature resolution change function (C R )silver, A gamma-ray radionuclide identification device in which, where g is 1.050 ~ 1.060, h is 0.010 ~ 0.024, k is 0.0120 ~ 0.0126, l is 7.300 ~ 7.326, m is 4.095 ~ 5.005, and T is the temperature (°C) of the gamma-ray detector. Claim 4 A gamma ray radionuclide identification device according to claim 1, wherein the gamma ray detector comprises: a scintillation element that generates a scintillation by gamma rays; a temperature sensor that measures and outputs the temperature of the gamma ray detector; a photodetector that receives the scintillation generated by the scintillation element and converts it into a gamma ray spectrum of the electrical signal and outputs it; and a first amplifier that converts the electrical signal for the gamma ray spectrum output from the photodetector into a voltage signal. Claim 5 A gamma ray radionuclide identification device according to claim 1, wherein the signal processing unit comprises: a second amplifier that amplifies a voltage signal corresponding to the gamma ray output from the gamma ray detection unit; an AD converter that converts the voltage signal output from the second amplifier into a digital voltage signal and outputs it; a computer that uses the digital voltage signal to detect the energy of the gamma ray by reflecting the peak shift and resolution change of the gamma ray spectrum according to the temperature at the time of gamma ray detection, and then identifies and outputs the gamma ray radionuclide using a gamma ray radionuclide library; and a storage device that stores the gamma ray radionuclide library in which the gamma ray radionuclide for gamma ray radionuclide identification by the computer is matched with the gamma ray energy radiated for each gamma ray radionuclide. Claim 6 In claim 5, the gamma ray nuclide library is a gamma ray nuclide identification device in which a plurality of gamma ray energies corresponding to a plurality of peaks included in the gamma ray spectrum emitted from the gamma ray nuclide are matched to each of the gamma ray nuclides. Claim 7 A method for identifying gamma-ray radionuclides using a gamma-ray radionuclide identification device of claim 1, comprising: a calibration step of deriving a channel energy correlation function (y(E)) and a channel resolution correction function (y(R)) of a gamma-ray spectrum using a standard radiation source; and a temperature peak shift change function (C) using the gamma-ray spectrum emitted from the standard radiation source. E ) and temperature resolution change function (C R A method for identifying gamma-ray nuclides, comprising: a step of deriving a temperature change function to derive a temperature change function; and a step of identifying gamma-ray nuclides, comprising: a step of detecting the energy of a gamma-ray spectrum by applying a peak shift and spectrum change and a resolution change according to the temperature to a gamma-ray spectrum emitted from a gamma-ray nuclide to be identified, and applying the detected energy to a gamma-ray nuclide library to identify the gamma-ray nuclide, wherein the gamma-ray nuclide identification step comprises: a peak detection step of searching for a peak of a gamma-ray channel by distinguishing it from a noise peak in the gamma-ray spectrum emitted from the gamma-ray nuclide to be identified; a channel calculation step of calculating a peak center channel corresponding to the center of a peak by performing a peak search by the resolution size of a channel position corresponding to the detected peak; an energy calculation step of calculating and outputting the peak center channel as energy; and a step of deriving a gamma-ray nuclide by comparing the energy of the peak center channel with the energy of the gamma-ray nuclide library to derive the gamma-ray nuclide. Claim 8 In claim 7, the gamma-ray nuclide identification step comprises a channel energy correlation function (y(E)), a channel resolution correction function (y(R)), and a temperature peak shift change function (C E ) and temperature resolution change function (C R A gamma-ray nuclide identification method for calculating the energy of the above gamma-ray spectrum by applying ). Claim 9 A method for identifying gamma-ray nuclides according to claim 7, wherein the channel energy correlation function (y(E)) is y(E) = a*x + b, where y(E) is the energy of the gamma ray corresponding to the channel (MeV), x is the number of channels, a is 999.299±2.56, and b is 14.54±0.

84. Claim 10 In claim 7, the channel resolution correction function (y(R)) is y(R) = a*x b A gamma-ray radionuclide identification method in which, where y(R) is the rate of change of channel resolution (%), x is the number of channels, a is 1.7646±0.2792, and b is -0.45564±0.

023. Claim 11 delete Claim 12 In claim 7, the temperature resolution change function (C R )silver, A method for identifying gamma-ray nuclides, wherein, here, g is 1.050 ~ 1.060, h is 0.010 ~ 0.024, k is 0.0120 ~ 0.0126, l is 7.300 ~ 7.326, m is 4.095 ~ 5.005, and T is the temperature (°C) of the gamma-ray detector. Claim 13 delete

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