JP3807652B2 - Radiation measurement apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation measuring apparatus and method, and more particularly to an apparatus and method for measuring environmental radiation and displaying the measurement result.
[0002]
[Prior art]
In radiation treatment facilities such as medical facilities and nuclear power plants that use radiation, environmental radiation (for example, gamma rays) is monitored in and around the facility. Factors that cause fluctuations in gamma rays to be monitored include changes in radon concentration due to rainfall, etc., the use of X-rays and gamma rays in nondestructive inspections, and the effects of electromagnetic waves such as lightning and radar. There are various factors. It is the most important matter in environmental radiation monitoring to quickly and accurately determine whether the fluctuation is due to these factors or abnormal fluctuation.
[0003]
Conventionally, various types of radiation measuring devices have been used to monitor radiation. Among them, a known multi-channel analyzer (MCA) is a device that displays a count value (dose rate) as a spectrum for each energy of radiation.
[0004]
However, in order to use MCA for environmental radiation monitoring and to determine whether the spectrum changes due to abnormalities or other factors due to the spectrum display, generally a wealth of knowledge and experience is required. Is needed. Further, when a plurality of factors are intertwined or when the spectrum variation is small, it is generally difficult for even an expert to analyze the factor of the spectrum variation quickly. In addition, it can be said that it is more difficult to make the above determination using the measurement results of a general dosimeter or the like.
[0005]
[Problems to be solved by the invention]
As described above, measurement and display by various conventional monitoring devices cannot be said to be sufficient to quickly and accurately determine whether there is a change in dose due to abnormality or a change in dose due to other factors. Therefore, in the unlikely event that an abnormality occurs, a display method that can intuitively grasp the situation is demanded in order to quickly determine the situation and immediately perform factor analysis. Further, there is a demand for an apparatus capable of easily confirming a change in dose even for a person who has little knowledge or experience of radiation measurement.
[0006]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to express a variation in dose more easily in displaying a radiation measurement result.
[0007]
Another object of the present invention is to provide a display that can quickly and accurately determine the dose variation factor.
[0008]
[Means for Solving the Problems]
(1) In a preferred aspect of the present invention, a radiation detection unit that detects radiation and outputs detection data continuously and a difference calculation between the detection data are executed, and a result of the difference calculation is predetermined. the running standardized operations, which a data computation unit for determining the normalized volatility with, including a display unit, the displaying the temporal change of the normalized volatility.
[0009]
According to the above configuration, the difference calculation is performed between two detection data different in time, and the calculation result is displayed after predetermined standardization is performed. Therefore, the variation of the count value (or count rate) can be clearly expressed, and the variation tendency and the like can be displayed in a format that is easier to visually understand than the conventional display method.
[0010]
Note that, when performing a predetermined normalization calculation, a standard deviation is preferably used as described later. The radiation is generally γ rays (X rays), but the principle of the present invention can be applied to β rays and α rays.
[0011]
(2) In the present invention, a radiation detection unit that detects radiation and outputs detection data continuously, a discrimination unit that discriminates the detection data for each radiation energy, and is temporally adjacent to each radiation energy The difference calculation between the detection data N (t−1, i) and N (t, i) is executed (where N (t, i) is the radiation energy i and the count rate at time t) , and the difference calculation A normalization operation is performed to divide the result by the standard deviation A (t, i) ^1/2 (however, A (t, i) ^1/2 = (N (t, i) + N (t-1, i) ) / 2) ^1/2), and by the this RiTadashi Kakuka fluctuation rate F (t, a data computation unit for obtaining a i), the normalized fluctuation rate F (t, the time course of i) for each radiation energy And a display processing unit for displaying a graph. Here, the result of the difference calculation is N (t, i) − N (t-1, i) or its absolute value.
[0012]
According to the above configuration, a difference calculation is performed between detection data that are temporally different from each other, a fluctuation is extracted, and further, the fluctuation can be normalized based on the standard deviation. Regardless of the size (even if there is a difference in the count value between the energies), the variation can be raised on the display. Therefore, even a person with little knowledge and experience can intuitively grasp the fluctuation phenomenon.
[0013]
In particular, in environmental monitoring, comparing actual displayed graphs with typical patterns corresponding to radiation and radiation sources used in the facility makes it easy to determine whether an abnormality has occurred or other factors. be able to. In this case, nuclide discrimination can be easily performed.
[0014]
(3) Various methods can be employed for displaying the standardized fluctuation rate.
[0015]
Here, preferably, the display processing unit creates a three-dimensional graph in which the first axis is a radiation energy axis, the second axis is a time axis, and the third axis is an axis representing the normalized variation rate. In this case, color coding may be performed according to the positive and negative of the third axis. According to such display processing, it is possible to more intuitively grasp whether the fluctuation is increasing or decreasing.
[0016]
Preferably, the display processing unit is a two-dimensional graph in which the first axis is a radiation energy axis, the second axis is a time axis, and the normalized variation rate is expressed using at least one of luminance and hue. Create According to such a two-dimensional graph, it is possible to clearly represent the changing portion by expressions such as color, brightness, and density, and in this case, it is possible to realize an intuitively easy-to-understand expression.
[0017]
Preferably, the display processing unit creates a two-dimensional graph in which the first axis is a radiation energy axis or a time axis, and the second axis is an axis representing the normalized variation rate. In this two-dimensional graph, the fluctuation of only a specific channel may be displayed, but the fluctuation of a large number of channels may be displayed simultaneously using color coding or the like.
[0018]
Preferably, an alarm determination unit that determines an alarm state by comparing the normalized variation rate and a predetermined alarm determination value; an alarm output unit that outputs an alarm signal when the alarm state is determined; including. In addition to visual confirmation, automatic alarm judgment can be used to reliably handle abnormal situations.
[0019]
(3) Moreover, in order to achieve the said objective, the method which concerns on this invention detects the radiation, The detection data is output, The process of discriminating the said detection data for every radiation energy, For every radiation energy For the detection data N (t−1, i) and N (t, i) that are temporally adjacent, the normalized variation rate F (t, i) is
[Expression 1]
F (t, i) = (N (t, i) −N (t−1, i)) / A (t, i) ^1/2 (1)
However, N (t, i) is the radiation energy i, and the counting rate A (t, i) ^{1/2 at} time t is the standard deviation (A (t, i) ^1/2 = (N (t, i) + N (t-1, i)) / 2) ^1/2 )
And a step of calculating by the following.
[0020]
In the above equation (1), the numerator corresponds to the time difference of the detection data, and the denominator corresponds to normalization by standard deviation. Here, (N (t, i) + N (t-1, i)) / 2 is a moving average.
[0021]
It is known that the count in radioactivity measurement can vary statistically within a certain multiple of the standard deviation. Therefore, when the same object is measured continuously, the amount of fluctuation between detection data, that is, the difference is divided by the standard deviation, so that the value after normalization can be basically kept within a certain range in the entire energy range. . If the standard deviation can be approximated by the square root of the detection data (count value), good standardization can be performed over the entire energy range by the above equation (1) .
[0022]
In the calculation formula (1) above, the numerator may be the absolute value of the difference. Further, the expression may be modified so that the background is taken into account .
[0023]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0024]
FIG. 1 shows a preferred embodiment of a radiation measuring apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof. This radiation measuring apparatus is also used in, for example, radiation treatment facilities such as medical facilities and nuclear power plants that use radiation, and monitors environmental radiation (for example, gamma rays) in and around the facility. . Of course, the present invention is applicable to other radiation measurements.
[0025]
In FIG. 1, the radiation measuring apparatus according to the present embodiment is roughly composed of a detector 10, a γ-ray spectrometer 12, and a computer. The detector 10 is a device that detects γ-rays that are radiation, and includes, for example, a NaI (Tl) type scintillation detector. Incidentally, the detector 10 may be portable. The detector 10 continuously detects γ-rays, and the detected data is sent to the γ-ray spectrometer 12.
[0026]
In the γ-ray spectrometer 12, a signal as detection data is amplified by the amplifier 14 and then converted into digital data by the ADC 16. The detection data converted into the digital data is sent to the wave height analyzing unit 18 where the wave height analyzing unit 18 discriminates the wave height and obtains a count value N for each energy (channel). And the energy spectrum for every time is once memorize | stored. In FIG. 1, the structure of the memory in the wave height analysis unit 18 is conceptually shown, that is, stored independently for each spectrum at each time.
[0027]
The analysis result by the wave height analysis unit 18 is output to the standardization calculation unit 20. The normalization calculation unit 20 is means for executing the above-described equation (1). Specifically, the standardized fluctuation rate F is calculated by calculating the difference between adjacent data and dividing the difference by the standard deviation. The calculation result is sent to the graph creation unit 22 and the alarm determination unit 23.
[0028]
The graph creation unit 22 is a means for graphing the calculated standard variation rate F. The graph created in this way is displayed on the display 24. The alarm determination unit 23 compares the standardized variation rate F with a predetermined alarm determination value K. When the standardized variation rate F becomes larger than the alarm determination value K, the alarm determination unit 23 sends a predetermined alarm signal to the outside. Output. Incidentally, the absolute value of the normalized variation rate may be calculated prior to the alarm determination, or the alarm value K may be set to both positive and negative.
[0029]
2 to 4 show display examples of the normalized variation rate according to the present embodiment. In the display example shown in FIG. 2, the first axis is the energy axis, the second axis is the time axis, and the third axis is the axis representing the normalized variation rate. Then, a hue or luminance corresponding to the axis is assigned according to the magnitude of the normalized variation rate, and the magnitude of the normalized variation rate can be intuitively grasped by such hue or luminance. As shown in FIG. 2, unlike the conventional display, when a variation in radiation occurs, it is possible to visualize the variation more prominently. Therefore, even if it is a person with little experience and knowledge, there exists an advantage that the fluctuation | variation of a radiation can be grasped | ascertained more intuitively and easily. In addition, according to the display example shown in FIG. 2, since the change in the normalized variation rate is represented for each energy, it is easy to determine the radionuclide. As a result, when an abnormality occurs, there is an advantage that it is possible to more accurately determine whether the abnormality is due to an artificial factor or other factors.
[0030]
In the display example shown in FIG. 3, the first axis is the energy axis, and the second axis is the time axis. The magnitude of the normalized variation rate is expressed by hue or luminance. A guide indicating the size is shown in the box on the right side of the figure. According to such a display example, it is possible to grasp at a glance what kind of fluctuation has occurred in which energy due to a change in hue or a change in density. In the display example shown in FIG. 2, the overlap in the depth direction occurs. However, according to the display example shown in FIG. 3, the luminance axis or the hue axis can be used in the two-dimensional plane. Can be avoided.
[0031]
In FIG. 4, in the display example shown in FIG. 2, one axis is an energy axis, and the other axis is an axis representing the magnitude of the normalized variation rate. Therefore, in such a display example, the display is updated in real time. Even in this display example, it is possible to clearly grasp the energy site where the fluctuation occurs. Although radiation itself varies, according to various display examples according to the present embodiment, unnatural variation can be expressed more remarkably with respect to such variation. In this regard, reference is made to the comparative example of FIGS.
[0032]
In the comparative example shown in FIGS. 5 and 6, another display example when performed under the same measurement conditions as the display example shown in FIG. 3 is shown. In the comparative example shown in FIG. 5, a simple count difference for each energy is represented, and in the comparative example shown in FIG. 6, a value obtained by dividing the count difference for each energy by the count moving average is shown. As shown in FIG. 5, if the count difference is simply expressed, the fluctuation at the time of abnormality cannot be expressed more remarkably, and the same problem occurs in the display example as shown in FIG. .
[0033]
Therefore, according to the display mode according to the present embodiment described above, it is possible to recognize fluctuations at the time of abnormality more quickly and to perform analysis thereof, particularly in monitoring gamma rays in or around radiation handling facilities. There is.
[0034]
In the above embodiment, the detector 10 is not limited to the one described above, and various detectors can be used. In the configuration example shown in FIG. 1, the γ-ray spectrometer 12 and the computer at the subsequent stage are directly connected. Of course, the data is once recorded on an external recording medium and the external recording medium is recorded. The data may be read by setting to the computer. In the display examples shown in FIGS. 2 to 4, the standardized fluctuation rate F is provided with a sign, but of course, the absolute value may be displayed depending on the application. That is, the present invention can be variously modified.
[0035]
【The invention's effect】
As described above, according to the present invention, when displaying the radiation measurement result, it is possible to make it easier to understand the variation of the dose, and it is possible to quickly and accurately determine the variation factor of the dose.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a preferred embodiment of a radiation measuring apparatus according to the present invention.
FIG. 2 is a diagram showing a display example 1 according to the present embodiment.
FIG. 3 is a diagram showing a display example 2 according to the present embodiment.
FIG. 4 is a diagram showing a display example 3 according to the present embodiment.
FIG. 5 is a diagram showing a comparative example.
FIG. 6 is a diagram showing a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Detector, 12 gamma ray spectrometer, 14 amplifier, 16 ADC, 18 Wave height analysis part, 20 Normalization calculating part, 22 Graph preparation part, 23 Alarm determination part, 24 Display.

Claims (7)

A radiation detector that detects radiation and outputs detection data continuously;
A discrimination unit for discriminating the detection data for each radiation energy;
For each radiation energy, a difference operation between detection data N (t−1, i) and N (t, i) adjacent in time is executed (where N (t, i) is the radiation energy i, (Counting rate at time t) , and the result of the difference calculation is divided by the standard deviation A (t, i) ^1/2 (where A (t, i) ^1/2 = (N (t, t, i) + N (t-1 , i)) / 2) 1/2), a data computation unit for obtaining it in by RiTadashi Kakuka fluctuation rate F (t, i),
A display processing unit that graphically displays changes over time of the normalized fluctuation rate F (t, i) for each radiation energy;
A radiation measuring apparatus comprising: The apparatus of claim 1.
The result of the difference calculation is N (t, i) − N (t-1, i) Or a radiation measuring apparatus characterized by having an absolute value thereof. The apparatus of claim 1 .
The display processing unit creates a three-dimensional graph in which the first axis is a radiation energy axis, the second axis is a time axis, and the third axis is an axis representing the normalized variation rate F (t, i). A radiation measuring apparatus characterized by the above. The apparatus of claim 1 .
The display processing unit is a two-dimensional representation in which the first axis is a radiation energy axis, the second axis is a time axis, and the normalized variation rate F (t, i) is expressed using at least one of luminance and hue. A radiation measuring apparatus characterized by creating a graph. The apparatus of claim 1 .
The display processing unit creates a two-dimensional graph in which a first axis is a radiation energy axis or a time axis, and a second axis is an axis representing the normalized variation rate F (t, i). measuring device. The apparatus of claim 1 .
An alarm determination means for comparing the standardized fluctuation rate F (t, i) with a predetermined alarm determination value to determine an alarm state;
Alarm output means for outputting an alarm signal when the alarm state is determined;
A radiation measuring apparatus comprising: Detecting radiation and outputting detection data;
Discriminating the detection data for each radiation energy;
For each radiation energy, the normalized fluctuation rate F (t, i) is calculated for the detection data N (t−1, i) and N (t, i) that are temporally adjacent to each other.
F (t, i) = (N (t, i) −N (t−1, i)) / A (t, i) ^1/2 (1)
Where N (t, i) is the radiation energy i and the counting rate at time t
A (t, i) ^1/2 is the standard deviation
[A (t, i) ^1/2 = (N (t, i) + N (t-1, i)) / 2) ^1/2 ]
A process of calculating by
A radiation measurement method comprising:

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