KR102644122B1 - Method for temperature compensation of radiation spectrum - Google Patents

Abstract

The present invention relates to a method of temperature compensation of a radiation spectrum for radionuclide identification, comprising: a first step of receiving and storing background radiation energy spectrum data measured by a radiation detector in an environment without an object for radionuclide identification; A second step of calculating and storing a reference count center value and a reference count rate from the background radiation energy spectrum data; A third step of receiving and storing the object radiation energy spectrum data measured by the radiation detector in an environment where there is an object for determining radionuclides; A fourth step of calculating and storing an object count center value and an object count rate from the object radiation energy spectrum data; A fifth step of comparing the reference count center value and the object count center value; And if the object count center value exceeds a preset error range compared to the reference count center value, a sixth step of comparing the reference count rate and the object count rate and adjusting a gain value for temperature compensation, wherein the third Steps through step 6 are repeatedly performed, and the radiation energy spectrum for nuclide identification is temperature-compensated.

Description

Temperature compensation method of radiation spectrum for nuclide identification {METHOD FOR TEMPERATURE COMPENSATION OF RADIATION SPECTRUM}

The present invention relates to a method of temperature compensation of a radiation spectrum, and more specifically, to a method of temperature compensation of a radiation spectrum for nuclide discrimination, which allows temperature compensation for nuclide discrimination to be quickly performed through software.

In general, scintillator-type detection systems such as NaI(Tl) and PVT are equipment that analyzes incident radiation/radiological information using the spectrum of radiation energy incident on the detector. A scintillator-type detector absorbs incident radiation energy and emits a proportional amount of photons. At this time, the generated photons are measured by the PMT, and the radiation energy spectrum is measured by collecting count information for each radiation energy through an MCA (Multi-Channel Analyzer).

The coefficient distribution of the radiation energy spectrum is determined by gamma-ray reactions such as photoelectric effect, Compton scattering, and electron pair generation, and analysis using the full energy peak is mainly used. The total energy peak is the peak that absorbs all of the radiation energy and has a Gaussian shape. The full energy peak is narrow and indicates a specific energy, and is used for energy correction and nuclide identification.

Energy calibration is a process of matching energy information for each channel using several random radionuclides, and nuclide identification is an analysis that determines the radionuclides contained in the measured sample (or radiation) and determines the energy of the full-energy peak and the target. Matching radionuclides are identified by comparing the energy information of the radionuclides. In other words, the energy corresponding to each channel is calculated and the nuclide is determined by comparing the channel (energy) where the full energy peak occurs with the energy of the existing nuclide information.

On the other hand, optical sensors (PMT, SiPM, etc.) that measure the amount of light generated from NaI(Tl), PVT, etc. are sensitive to temperature and affect the radiation energy spectrum. Spectral changes according to temperature show a tendency for the full-energy peak to shift to a lower channel as the temperature increases, and this change results in inaccurate nuclide identification.

The technology that compensates for this problem is called temperature compensation technology, and by incorporating temperature compensation technology, it has fixed energy for a specific channel. Temperature compensation technology is divided into hardware technology and software technology. Hardware technologies include 1) a method using a thermometer (disclosed in Korean Patent Publication No. 10-1188749, etc.), and 2) a method using LEDs (disclosed in U.S. Patent Publication No. 07642516, etc.). The software technology is a correction method through spectrum analysis.

Software technology includes a temperature compensation method using natural radionuclides. In environments excluding extreme environments such as the ocean and space environments, radiation from natural radionuclides is collected from the surroundings, and this can be used for temperature compensation. Radiation measured from the surrounding environment uses the total energy peaks measured from Pb-212, Pb-214, K-40, and Tl-208 to check changes in energy levels for each channel through regular spectrum analysis and determine the corresponding energy difference. This is a way to correct it.

However, this temperature compensation method requires a long calculation time as the peak search and peak positioning algorithms are composed of very complex formulas and requires at least 5 minutes of measurement data (depending on the detector volume). In other words, it is suitable for use when using a high-speed operation processor such as a PC, but it is difficult to apply to low-power operation processors built into small or portable equipment due to insufficient performance.

For analysis of natural nuclides, at least 5 minutes of measurement data is required, and if the energy is wrong due to temperature compensation, a gap time (as much as the measurement time) for correction is created to adjust the difference, causing a disruption in the actual radiation analysis.

Korean Patent Publication No. 10-1188749 US Patent Publication No. 07642516

The purpose of the present invention is to provide a method of temperature compensation of the radiation spectrum for nuclide identification, in which temperature compensation for nuclide identification can be quickly achieved through software.

The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The present invention for achieving the above object includes a first step of receiving and storing background radiation energy spectrum data measured by a radiation detector in an environment without an object for identifying radionuclides; A second step of calculating and storing a reference count center value and a reference count rate from the background radiation energy spectrum data; A third step of receiving and storing the object radiation energy spectrum data measured by the radiation detector in an environment where there is an object for determining radionuclides; A fourth step of calculating and storing an object count center value and an object count rate from the object radiation energy spectrum data; A fifth step of comparing the reference count center value and the object count center value; And if the object count center value exceeds a preset error range compared to the reference count center value, a sixth step of comparing the reference count rate and the object count rate and adjusting a gain value for temperature compensation, wherein the third Steps through step 6 are repeatedly performed, and the radiation energy spectrum for nuclide identification is temperature-compensated.

Specifically, in the sixth step, if the object count center value exceeds an error range of 5% compared to the reference count center value, the reference count rate and the object count rate may be compared.

In the sixth step, if the object counting rate is 10% or less compared to the standard counting rate, the gain value can be adjusted.

In the sixth step, the gain value may be calculated by dividing the reference count center value by the object count center value and multiplying the gain value preset in the first step.

According to the present invention, temperature compensation for the radiation energy spectrum is performed in software in about 15 seconds, so that the blank time for correction (as much as the measurement time) is greatly reduced as in the past, making it possible to quickly identify nuclides, and using low power. Because it can drive an operation processor, it can be applied to small or portable equipment.

Figure 1 is a block diagram schematically showing a system implementing the temperature compensation method of the radiation spectrum for nuclide identification according to the present invention.
Figure 2 is a flowchart showing the temperature compensation method of the radiation spectrum for nuclide identification according to the present invention.
Figure 3 is a graph of background radiation energy spectrum data.
Figure 4 is a graph of the process of accumulating and storing object radiation energy spectrum data and calculating a value.
Figure 5 is a graph showing the object radiation energy spectrum data within the error range.
Figure 6 is a graph showing that the object radiation energy spectrum data is within the error range and exceeds the target time.
Figure 7 is a graph when the object counting rate is greater than the standard counting rate.
Figure 8 is a graph in which the gain value is adjusted because the object counting rate is the same as or similar to the reference counting rate.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Identical elements in the drawings are indicated by identical symbols wherever possible. Additionally, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted.

As shown in Figures 1 and 2, the temperature compensation method of the radiation spectrum for identifying radionuclides of the present invention uses background radiation energy spectrum data measured by the radiation detector 100 in an environment without an object for identifying radionuclides. It begins with the step of receiving and storing (S10).

An environment without objects for identifying radionuclides refers to an environment in which only natural radiation is emitted. In other words, radiation below a certain level has no significant effect on the human body. As is well known, fine radiation that does not affect the human body is emitted in the natural world, and this is called natural radiation, and the state in which only natural radiation is emitted is called the background state.

The radiation detector 100 may be a scintillator type detector such as NaI(Tl). As is well known, the radiation detector 100 converts incident radiation into an electrical signal, amplifies its size, removes noise, and converts it into an analyzable signal. The converted signal is expressed in the form of a pulse, and the pulses are counted and stored separately according to the size of the voltage value. Each process that counts the pulses of each voltage value and manages them cumulatively over a certain period of time in the allocated buffer is called energy, and through this process, radiation energy spectrum data expressed as a count value (count value) according to the energy value can be obtained. .

The radiation detector 100 measures radiation in an environment without an object for identifying radionuclides, that is, in a background state, obtains background radiation energy spectrum data (referred to as “background spectrum data”), and then outputs it.

The background spectrum data is transmitted to the nuclide identification means (200) that is electrically connected to the radiation detector (100). The nuclide identification means 200 performs functions such as input, operation, control, memory, and output, and accumulates and stores background spectrum data transmitted from the radiation detector 100.

For example, the nuclide identification means 200 may be a multiple wave height analyzer (MCA). As is well known, the multi-wave analyzer is a device that classifies, collects, stores, and outputs background spectrum data, which is a pulse signal output from the radiation detector 100, by pulse height through the continuous execution method of a single-channel analyzer. It consists of a device and a display device, and is a device that divides and designates data storage for each range of pulse size to be analyzed, and when a pulse is output, digitizes the pulse size and adds it to the designated data storage corresponding to the numerical value.

The nuclide identification means 200 may be configured to have an algorithm for performing temperature compensation of the present invention mounted on such a multiple wave height analyzer (MCA). In contrast, the nuclide identification means 200 may be a computer means equipped with an algorithm for performing temperature compensation of the present invention and an existing multi-wave analyzer (MCA) electrically connected to the computer means.

This nuclide identification means 200 calculates and stores a standard count center value and a standard count rate from the background spectrum data transmitted by the radiation detector 100 (S20). The nuclide identification means 200 calculates the background spectrum data accumulated during a randomly set period of time, calculates and stores a standard count center value and a standard count rate.

CountCenter refers to a channel in which balance is achieved according to the count distribution on the same principle as the center of gravity (the position where balance is achieved according to weight distribution), which is used as an important factor in load design, etc., and the count center value is the accumulated radiation energy. It can be obtained through spectrum data, and the formula can be expressed as Equation 1 below.

는 채널(Ch)과 스펙트럼 i번째 채널 카운트값(Cnt_i)을 곱한 합이고,

는 스펙트럼 i번째 채널 카운트값(Cnt_i)의 합이다. 계수율은 카운트값들의 합을 시간으로 나누면 구할 수 있다.here,

is the sum of the channel (Ch) multiplied by the ith channel count value (Cnt _i ) of the spectrum,

is the sum of the ith channel count value (Cnt _i ) of the spectrum. The count rate can be obtained by dividing the sum of count values by time.

Figure 3 is a graph of background spectrum data (count value per channel) accumulated for 300 seconds. The count center value (C.C) of the accumulated measured background spectrum data calculated using Equation 1 and the count rate formula is 113.57 channels (ch). and the count rate is 583.0cps.

The values calculated in this way become reference values for performing temperature compensation, and are values obtained when a gain value of 1.386 is previously set in the nuclide discrimination means 200. The cumulative measurement time of 300 seconds represents the target time and is the minimum time to implement temperature compensation in software.

The initially set gain value (Gain) becomes a reference value for adjusting the gain for temperature compensation in the subsequent process, and the nuclide discrimination means 200 collects the background spectrum data accumulated for a target time of 300 seconds with the gain value (Gain) set. The standard count center value (C.C) and standard count rate are calculated through .

When the standard count center value and the standard count rate are calculated from the background spectrum data, the nuclide determination means 200 initializes the accumulated and stored background spectrum data by deleting it (S30).

When the accumulated background spectrum data is deleted and initialized, the nuclide determination means 200 uses the object radiation energy spectrum data (hereinafter, "object spectrum data") measured by the radiation detector 100 in an environment where there is an object for determining radionuclides. ) is transmitted and stored. At this time, the gain value does not change to 1.386.

The nuclide identification means 200 cumulatively measures and stores object spectrum data during a set cycle, and calculates and stores the object count center value and object count rate by applying Equation 1 and the count rate formula from the object spectrum data accumulated in each cycle. Do it (S40).

As illustrated in FIG. 4, when the object spectrum data is set to be measured at 1 second intervals for 15 seconds (minimum calculation time), the nuclide determination means 200 determines the object spectrum data from the object spectrum data accumulated and stored at 1 second intervals. The count center value (C.C.) and object count rate (Count rate) are calculated and stored cumulatively, and this process is repeated for 15 seconds. The minimum calculation time of 15 seconds is the minimum calculation time to calculate a meaningful object count center value and object counting rate that can calculate gain values for temperature compensation.

If the object spectrum data has not been cumulatively measured for 15 seconds and the cumulative values for the object count center value and object count rate cannot be calculated (S50), the nuclide determination means 200 feeds back to step S40 and collects the object spectrum data again. Cumulative measurements are made at 1-second intervals for 15 seconds (minimum calculation time). At this time, the nuclide determination means 200 can calculate the cumulative value by accumulating newly measured data to the currently accumulated data, initialize by deleting the currently accumulated and stored data, and then measure the object spectrum data again to calculate the accumulated value. It can be calculated.

When the object count center value and the object count rate are calculated through this process, the nuclide determination means 200 compares the reference count center value and the object count center value (S60).

The nuclide determination means (200) compares the object count center value and the standard count center value based on an error range of 5%, and if the object count center value is within the error range of ±5% compared to the standard count center value, the nuclide determination means ( 200) deletes and initializes the cumulatively measured and stored object spectrum data and each calculated value, and then cumulatively measures the object spectrum data from the radiation detector 100 to cumulatively calculate the object count center value and object count rate.

As illustrated in FIG. 5, the calculated object count center value is 110.6 channels (ch), which is within ±5% of the reference count center value 113.57 channels (ch), and the nuclide determination means 200 initializes the current accumulated data. After that, the object count center value and the object count rate can be cumulatively calculated by cumulatively measuring the object spectrum data from the radiation detector 100.

At this time, the nuclide determination means 200 may determine whether the cumulative measurement time of the object spectrum data exceeds the target time and perform a process of recalculating the object count center value and the object count rate (S70).

That is, if the cumulative measurement time is less than the target time, the nuclide determination means 200 feeds back to step S40 and cumulatively measures the object spectrum data from the radiation detector 100 to cumulatively calculate the object count center value and object count rate.

If the cumulative measurement time is more than the target time, the nuclide determination means 200 feeds back to step S30, deletes and initializes the accumulated measured and stored object spectrum data and each calculated value, and then accumulates the object spectrum data from the radiation detector 100 again. By measuring, the object count center value and object counting rate can be calculated cumulatively.

As illustrated in FIG. 6, when the cumulative measurement time reaches the target time of 300 seconds, the nuclide determination means 200 feeds back to step S30 to initialize the data and then cumulatively measures the object spectrum data from the radiation detector 100 again. Calculate the object count center value and object count rate.

If the object count center value exceeds the error range of 5% compared to the standard count center value, the nuclide determination means 200 compares the standard count rate and the object count rate (S80). The object counting rate is a cumulative value once the measurement cycle is set as described above.

The nuclide determination means 200 compares the standard counting rate and the object counting rate based on 10%. If the object counting rate exceeds 10% compared to the standard counting rate, radionuclide discrimination is performed. If the object counting rate is 10% or less compared to the standard counting rate, the nuclide determination means 200 compares the standard counting rate and the object counting rate. , determine the effect of temperature and adjust the gain value for temperature compensation (S90).

As illustrated in FIG. 7 , when the object counting rate is 843.0 cps, which exceeds 10% of the standard counting rate of 583.0 cps, the nuclide discrimination means 200 proceeds with radionuclide discrimination, and as illustrated in FIG. 8 , the object counting rate is If it is 581.5 cps, which is 10% or less compared to the standard count rate of 583.0 cps, the nuclide determination means 200 calculates a gain value (setGain) for temperature compensation and adjusts the gain.

The adjusted gain value (setGain) is calculated by dividing the reference count center value by the object count center value and multiplying it by the preset gain value (Gain), and can be expressed in Equation 2 below.

Here, setGain is the gain value to be adjusted, Gain is the preset gain value, refC.C is the reference count center value, and C..C is the object count center value.

Referring to FIG. 8, the gain value (setGain) is preferably calculated when the object counting rate is the same or similar to the reference counting rate, the object count center value is 99.6ch, the preset gain value (Gain value) is 1.386, and the standard If the count center value is 113.57ch, the nuclide determination means 200 calculates 1.386×(113.57/99.6) to calculate a gain value (setGain) of 1.5804.

When the gain value (setGain) is calculated, the nuclide determination means 200 adjusts and sets the preset gain value (Gain) to the newly calculated gain value (setGain) and then feeds back to step S30 to initialize by deleting all data. Afterwards, steps S40 to S90 are repeatedly performed, and the repeated performance is performed until the object counting rate exceeds 10% of the standard counting rate.

As described above, according to the present invention, temperature compensation for the radiation energy spectrum is achieved using software technology rather than temperature compensation using hardware technology using a thermometer or LED, and the temperature compensation is performed for about 15 seconds, thereby reducing the existing temperature compensation. As shown, the blank time for correction (as much as the measurement time) is greatly reduced, enabling rapid identification of nuclides, and the operation processor can be driven with low power, so it can be applied to small or portable equipment.

The above-described present invention has been examined with a focus on preferred embodiments, and those skilled in the art will be able to implement embodiments other than the detailed description of the present invention within the essential technical scope of the present invention. You will be able to. Here, the essential technical scope of the present invention is indicated in the claims, and all differences within the equivalent scope should be construed as being included in the present invention.

100: Radiation detector
200: Nuclide identification means

Claims (4)

A first step of receiving and storing background radiation energy spectrum data measured by a radiation detector in an environment without an object for identifying radionuclides;
A second step of calculating and storing a reference count center value and a reference count rate from the background radiation energy spectrum data;
A third step of receiving and storing the object radiation energy spectrum data measured by the radiation detector in an environment where there is an object for determining radionuclides;
A fourth step of calculating and storing an object count center value and an object counting rate from the object radiation energy spectrum data;
A fifth step of comparing the reference count center value and the object count center value; and
When the object count center value exceeds a preset error range compared to the reference count center value, a sixth step of comparing the reference count rate and the object count rate and performing temperature compensation,
In the first step, the background radiation energy spectrum data is stored for a preset target time,
In the second step, the reference count center value and the reference count rate are calculated from a preset gain value,
In the third step, the object radiation energy spectrum data is initialized by deleting the background radiation energy spectrum data and stored with the gain value unchanged,
In the fourth step, the object count center value and the object count rate are calculated from the object radiation energy spectrum data stored for a preset minimum calculation time,
In the sixth step, if the object count center value exceeds a preset error range compared to the reference count center value, the reference count rate and the object count rate are compared, and as a result of the comparison, the object count rate is 10% or less compared to the standard count rate. If so, the gain value is adjusted by multiplying the gain value by dividing the reference count center value by the object count center value and then feeding back to the third step,
In the sixth step, if it is within the error range and the measurement time of the object radiation energy spectrum data is less than the target time, feeding back to the third step to store the object radiation energy spectrum data,
In the sixth step, if it is within the error range and the measurement time of the object radiation energy spectrum data exceeds the target time, it is fed back to the third step to include the object radiation energy spectrum data, the object count center value, and the A temperature compensation method of a radiation spectrum for nuclide discrimination, characterized in that the object count rate is deleted and initialized, and then the object radiation energy spectrum data is transmitted and stored again from the radiation detector.
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