JP7168531B2 - Radiation monitor - Google Patents

Description

The present invention relates to a radiation monitor.

Light emission occurs when radiation is incident on a scintillator and part or all of the energy of the incident radiation is imparted to the scintillator through nuclear reaction, interaction, or the like. In many cases, the emitted light intensity depends on the energy applied to the scintillator. Therefore, the amount of energy given to the scintillator can be known by measuring the amount of emitted light.
The amount of light emitted from the scintillator is converted into electrical information by a photoelectric conversion device such as a photomultiplier tube and measured. In a scintillation detector, a photomultiplier tube is connected to a scintillator. Photons emitted by the scintillator excite electrons on the photocathode, emitting photoelectrons, which are then amplified to measure radiation. is doing. Since scintillation light has different emission wavelengths depending on the type of scintillator, a suitable photocathode is generally selected for each type of scintillator. In a scintillation detector that measures the crest value, amplified electrons are output as a pulse having a crest value corresponding to the energy. The energy imparted to the scintillator is measured as the crest value of the pulse.

Many materials used as photocathode emit different amounts of photoelectrons per incident photon depending on the temperature. Therefore, in a field where the temperature fluctuates, even the same crest value corresponds to different energy depending on the temperature on the photocathode. In situations where accurate crest value analysis is required, such as using a scintillator with high energy resolution to separate and measure gamma rays of a specific energy from gamma rays of multiple energies, it is necessary to take measurements based on temperature changes. be.
Fluctuations in peak values due to temperature cannot be corrected or reset after each measurement, such as prior energy calibration, energy analysis after measurement, and relative comparison with known peak values of radiation that serve as indices. It is possible.

However, when continuously monitoring radiation in an environment with temperature changes, the peak value variation must be corrected within a short period of time.
As one of peak value correction methods for such a situation, there is Patent Document 1.

In Patent Document 1, the ambient temperature is measured by a thermistor provided around the detector, the temperature of the measurement part is estimated based on the temporal change of the temperature measured by the thermistor, and based on the estimated temperature of the measurement part A radiation measurement apparatus is described that corrects radiation data output from a measurement unit. The radiation measurement device described in Patent Document 1 measures the temperature around the detector to correct temperature fluctuations, and corrects the time delay such as the heat transfer time until the temperature fluctuations are affected. monitoring.

Japanese Unexamined Patent Application Publication No. 2014-21040

As described above, in a radiation measuring apparatus that continuously monitors radiation of arbitrary energy using a scintillation detector, accurate monitoring cannot be continued unless the fluctuations in the peak value due to temperature fluctuations are corrected each time. Can not. When one monitoring time is a constant long measurement, it is possible to correct the peak value appropriately during one monitoring by measuring the temperature while measuring the peak value distribution. However, if multiple measurements are required during a time delay such as heat transfer between the location of a temperature-sensitive device such as a scintillator or photomultiplier tube and the temperature measurement location, a faster wave than the temperature measurement is required. A high price correction method is needed.

The present invention has been made in view of such circumstances, and is a radiation monitoring apparatus capable of continuous monitoring in a short period of time using a scintillation detector without the need for temperature measurement in an environment with temperature fluctuations. The task is to provide

In order to solve the above-mentioned problems, a radiation monitoring device for monitoring radiation by acquiring an output signal from a scintillation detector that outputs a signal of peak value corresponding to the energy of radiation, wherein the peak value a monitoring peak value range of a monitoring target in which the peak value fluctuates; a peak value range setting means for setting at least two peak value ranges within the monitoring peak value range; peak value variation calculation means for calculating a peak value variation based on the ratio; and correction means for correcting the monitored peak value range so that the calculated peak value variation is reduced ; The peak value fluctuation amount calculation means calculates the peak value fluctuation amount based on the ratio of the count rate of the peak value of the peak that has a normal distribution in the peak value distribution to be monitored, and calculates the peak value fluctuation amount based on the peak value to be monitored. A standard deviation storage means for storing the correlation between the deviation and the center peak value of the peak is provided, and the peak value fluctuation amount calculation means calculates the peak value fluctuation amount based on the correlation stored in the standard deviation storage means. It is characterized by calculating .
Other aspects of the present invention are described in embodiments below.

According to the present invention, it is possible to provide a radiation monitoring apparatus capable of continuous monitoring in a short period of time using a scintillation detector without the need for temperature measurement in an environment with temperature fluctuations.

1 is a diagram showing the configuration of a radiation monitoring apparatus according to a first embodiment of the invention; FIG. FIG. 4 is a diagram showing an output signal of the scintillation detector when gamma rays are incident on the scintillation detector of the radiation monitoring apparatus according to the first embodiment of the present invention; It is a figure explaining that the crest value of the radiation monitoring apparatus concerning the 1st Embodiment of this invention is proportional to temperature. 4 is a diagram showing peak value distribution of an output signal of a scintillation detector of the radiation monitoring apparatus according to the first embodiment of the present invention; FIG. It is a figure which shows the time relationship of the scintillation detector of the radiation monitoring apparatus which concerns on the 1st Embodiment of this invention, and the output signal of each measuring device. It is a figure which shows the actual measurement data of the peak value of the radiation monitoring apparatus based on the 1st Embodiment of this invention. It is a figure which shows the structure of the radiation monitoring apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the radiation monitoring apparatus which concerns on the 3rd Embodiment of this invention. FIG. 10 is a diagram showing the configuration of a radiation monitoring apparatus provided with a crest value adjustment function by a multichannel analyzer according to a fourth embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing the configuration of a radiation monitoring apparatus according to the first embodiment of the invention. The radiation monitoring apparatus of this embodiment is an example applied to, for example, a peak value analysis type radiation detector and a radiation monitoring apparatus.
[Radiation monitor 100]
The radiation monitoring apparatus 100 monitors the counting rate of radiation of arbitrary energy with the scintillation detector 11 in a field where the temperature changes.
As shown in FIG. 1, the radiation monitoring apparatus 100 includes at least three measurement devices 12a, 12b, and 12c for measuring signals in the peak value range of the scintillation detector 11, an analysis device 13, and a monitoring device 14. . The three measurement devices 12a, 12b, and 12c are collectively referred to as the measurement device 12. FIG.

<Scintillation detector 11>
The scintillation detector 11 outputs a signal with a peak value corresponding to the energy of radiation.
The scintillation detector 11 converts, for example, fluorescence generated when radiation is incident on a crystal of sodium iodide (NaI) (including thallium) into an electric signal using a photomultiplier tube, amplifies the signal, and outputs the signal. This scintillation detector 11 is suitable for detecting gamma rays, detects the energy of radiation, and outputs an analog electrical signal with a peak value corresponding to this energy.

<Measuring device 12>
The measuring device 12 has a peak value range setting value 105a that sets the peak value range 1, and the measuring device 12a that measures the signal in the peak value range 1 of the scintillation detector 11 and the peak value that sets the peak value range 2 A measuring device 12b that has a range setting value 105b and measures a signal in the peak value range 2 of the scintillation detector 11, and a peak value range setting value 105c that sets a monitoring peak value range 3, and the scintillation detector 11. and a measuring device 12c that measures a signal in the monitoring peak value range 3 .
The peak value range setting values 105 a , 105 b , 105 c (peak value range setting means) are set based on the peak value fluctuation amount calculated by the peak value range calculator 104 .
The details of the crest value ranges 1 to 3 will be described later with reference to FIGS. 2 to 4. FIG.

The measuring device 12a compares the detection signal from the scintillation detector 11 with the set peak value range 1, and outputs a logic pulse to the analyzer 13 when a peak value corresponding to the peak value range 1 is input. Send.
The measuring device 12b compares the detection signal from the scintillation detector 11 with the set peak value range 2, and outputs a logic pulse to the analyzer 13 when a peak value corresponding to the peak value range 2 is input. Send.
The measuring device 12c compares the detection signal from the scintillation detector 11 with the set peak value range 3, and outputs a logic pulse to the monitoring device 14 when a peak value corresponding to the monitoring peak value range 3 is input. Send to
Although the radiation monitoring apparatus 100 has three measuring devices 12a, 12b, and 12c for each peak value range 1 to 3 to be monitored, it is possible to detect at least three peak value ranges. If it is Also, the measurement devices 12a, 12b, 12c can be implemented using a single-channel analyzer capable of supporting a high signal processing speed of, for example, less than 1s.

<Analyzer 13>
The analysis device 13 calculates the peak value variation amount (“peak value variation amount calculation function”) and outputs adjustment signals for the peak values of the measurement devices 12a, 12b, and 12c (“monitored peak value range 3 correction function”). ).
The analysis device 13 includes counting units 101a and 101b, a counting rate ratio calculation unit 102 (peak value fluctuation amount calculation means), a temperature fluctuation correction database 103 (peak value fluctuation amount calculation means), and a peak value range calculation unit 104 ( crest value fluctuation amount calculation means, correction means).
The counting unit 101a counts the logic pulses output from the measuring device 12a based on the signal within the crest value range 1 .
The counting unit 101b counts the logic pulses output from the measuring device 12b based on the signal within the crest value range 2 .

The count rate ratio calculation unit 102 calculates the ratio of the count rate between the peak value of the peak value range 1 and the peak value of the peak value range 2 (hereinafter referred to as “count rate ratio”) (see FIG. 3 and the formula ( 2) See).
The temperature fluctuation correction database 103 stores in advance as a database the relationship between the counting rate ratio and the peak value fluctuation amount. Note that the temperature fluctuation correction database 103 has the relationship of Equation (3), which will be described later, so that the logarithm of the count rate ratio and the peak value fluctuation amount have a linear function relationship. By preparing in advance the relationship between the peak value fluctuation amount and the counting rate ratio as the temperature fluctuation correction database 103, the peak value fluctuation amount can be calculated at high speed and with high accuracy.

The peak value range calculator 104 calculates the peak value fluctuation amount based on the ratio of the count rates of the peak values in at least two peak value ranges (1, 2). In this embodiment, the peak value range calculator 104 refers to the temperature variation correction database 103 to calculate the peak value fluctuation amount from the ratio of the counting rates.
The peak value range calculator 104 has a function as a correction unit that corrects the monitored peak value range (3) so that the calculated peak value fluctuation amount becomes small. The peak value ranges (peak value ranges 1 to 3) set by the peak value range calculator 104 are input to the measuring devices 12a, 12b and 12c, respectively, and the peak value range setting values 105a and 105b of the measuring devices 12a, 12b and 12c are obtained. , 105c.
Also, the peak value range setting values 105a and 105b are input to the temperature fluctuation correction database 103, and are used when calculating the peak value fluctuation amount from the temperature fluctuation correction database 103 by the ratio of the following counting rates.

<Monitoring device 14>
The monitoring device 14 includes a counting unit 101c that counts the number of signals detected by the measuring device 12c. The counting unit 101c counts the logic pulses output from the measuring device 12c based on the signal within the monitoring peak value range 3 .
The monitoring device 14 acquires the peak value of the monitoring peak value range 3 of the peak value range setting value 105c to monitor the radiation.

[Output signal of scintillation detector 11]
FIG. 2 is a diagram showing an output signal of the scintillation detector 11 when gamma rays are incident on the scintillation detector 11. As shown in FIG. The horizontal axis is time, and the vertical axis is peak value.
The signals obtained by the scintillation detector 11 (see FIG. 1) are noise components, signals associated with Compton scattering, signals associated with photoelectric absorption, and signals associated with electron pair generation. Of these, the noise component has a relatively low peak value in many cases, although the peak value is not uniquely determined. Compton scattering, photoelectric absorption, and electron pair generation are phenomena caused by the interaction of gamma rays and scintillators.

The crest value of the signal obtained by the scintillation detector 11 is determined by the energy applied to the scintillator, and the greater the applied energy, the higher the crest value. In Compton scattering, the energy given to the scintillator is determined by the energy of the incident gamma ray and the scattering angle. In photoelectric absorption, the energy given to the scintillator is determined by the energy of incident gamma rays. In electron pair generation, the energy imparted to the scintillator is determined by the energy of the incident gamma rays. The energy imparted to the scintillators differs depending on whether the scintillators are ejected (single escape) or ejected from the two scintillators (double escape). When multiple interactions occur per incident gamma ray, a crest value corresponding to the sum of energies imparted by the interactions that have occurred is obtained.

The radiation monitoring apparatus 100 (see FIG. 1) sets a range of the peak value distribution of the output signal of the scintillation detector 11 that conforms to the normal distribution (see FIG. 4 described later) as the monitoring peak value range 3 shown in FIG. Also, two points within the monitoring peak value range 3 are set as the peak value range 1 and the peak value range 2 . A peak value range 1 shown in FIG. 2 is a peak value range set by the peak value range setting value 105a of the measuring device 12a of FIG. A peak value range 2 shown in FIG. 2 is a peak value range set by the peak value range setting value 105b of the measuring device 12b of FIG. A monitoring peak value range 3 shown in FIG. 2 is a peak value range set by the peak value range setting value 105c of the measuring device 12c in FIG.
The relationship between the crest value ranges 1 to 3 and the crest value distribution will be described later with reference to FIG.

<Variation of crest value due to temperature fluctuation>
FIG. 3 is a diagram explaining that the crest value is proportional to the temperature. Take Temperature [degrees Celsius] on the horizontal axis and Peak channel [ch] on the vertical axis. The ▴ mark in FIG. 2 represents the crest value.
As shown in FIG. 3, the crest value varies in proportion to temperature. For example, if the peak value indicated by symbol a in FIG. 2 is observed, it fluctuates so as to decrease as the temperature rises, as shown in FIG. For this reason, in a radiation measuring apparatus that continuously monitors radiation of arbitrary energy using a scintillation detector 11 (see FIG. 1), correct monitoring cannot be performed unless the fluctuations in the peak value due to temperature fluctuations are corrected each time. cannot continue.

<Peak value distribution of output signal>
FIG. 4 is a diagram showing the crest value distribution of the output signal of the scintillation detector 11. As shown in FIG. The horizontal axis is the crest value, and the vertical axis is the radiation count rate. For simplicity, FIG. 4 shows a crest value distribution assuming that only gamma rays of a single energy are incident on the scintillation detector 11 (see FIG. 1).

Photoelectric absorption or total absorption (when all energy is imparted to the scintillator by multiple interactions) yields the crest value distribution shown in FIG.
The peak value distribution shown in FIG. 4 can be separated into a peak 301 following a normal distribution, a region 302 dominated by Compton scattering or multiple scattering, and a region 303 dominated by noise components.

A peak 301 following a normal distribution is set as a monitoring peak value range 3, which is a monitoring range. The monitoring peak value range 3 is the peak value range set by the measuring device 12c (see the peak value range setting value 105c in FIG. 1). In the monitoring peak value range 3, the peak value fluctuates depending on the temperature.

Also, arbitrary two points (x ₁ , x ₂ ) within the monitoring peak value range 3 are set as the peak value range 1 and the peak value range 2 . The peak value range 1 is the peak value range 1 set by the measuring device 12a in FIG. 1 (see the peak value range setting value 105a in FIG. 1), and the peak value range 2 is the peak value range 2 set by the measuring device 12b. (See peak value range setting value 105b in FIG. 1).

The operation of the radiation monitoring apparatus 100 configured as described above will be described below.
[Explanation of principle]
First, the basic concept of the present invention will be described.
Note as a precondition that the crest value is proportional to the temperature, as shown in FIG.

The inventors paid attention to the fact that the peak value distribution peak 301 (see FIG. 4) is given by a normal distribution.
When a gamma ray of a certain energy is measured by the scintillation detector 11 and its peak value distribution is measured, all the energy is imparted to the scintillator by photoelectric absorption and multiple interactions. As a result, a peak 301 (see FIG. 4) represented by a normal distribution is formed in the crest value distribution. A peak 301 represented by this normal distribution is defined as a monitoring range (fluctuates with temperature), which is a monitoring peak value range 3 here. Also, any two points (x ₁ , x ₂ ) within the monitoring peak value range 3 are taken, and the count rate ratio (count rate ratio) between the peak value x ₁ and the peak value x ₂ is taken.
A normal distribution G _n (x) in the n-th measurement during continuous measurement is represented by the following equation (1).

Here, _{σn is the standard deviation and mn is} the center position of the normal distribution. Taking the ratio of the normal distribution at any two points x ₁ and x ₂ gives the following equation (2).

The above equation (2) expresses the count rate ratio F(x ₁ , x ₂ ) between the peak value x ₁ and the peak value x ₂ .
Equation (3) is obtained by solving equation (2) for the peak position _mn .

The above formula (3) indicates the actual processing. That is, (x ₁ +x ₂ )/2 in the first term of equation (3) indicates the setting values of the two peak value ranges, and σ _n ² /(x ₁ −x ₂ ) in the second term is known or ( The second term ln(F(x ₁ , x ₂ )) indicates the measured value of the count rate ratio between the peak value x ₁ and the peak value x ₂ .

The center position of the n-th normal distribution can be calculated from any two points according to the above equation (3). Arbitrary two points x ₁ and x ₂ are set values, and F(x ₁ , x ₂ ) is a value obtained from measured values. The standard deviation σ _n is set in advance for each peak position m _n as the performance of the scintillation detector 11, or if the fluctuation of the peak value is minute (n−1), by substituting the value for the n-th time It is possible to obtain the central position of the normal distribution of In many cases, σ _n is given as a linear function of m _n .
When the relationship between the peak position and σ is given by a linear function, _σn is given by the following equation (4).

_σn can be calculated according to the following equation (5) based on the _σn shown in the above equation (4) and the peak position _mn shown in the above equation (3). Under the condition shown in Equation (5), it is also possible to calculate σn using only _n -th information (without n-1th information).

Here, since the value to be calculated is the peak value fluctuation amount, m _n is obtained for each monitoring using σn obtained by either the above formula (4) or the above formula (5), and ( _n -1 time), the difference in the center position of the normal distribution obtained by the difference becomes the peak value fluctuation amount.

In this way, the radiation monitoring apparatus 100 estimates the peak value fluctuation amount from the ratio of the count rates of at least two peak value ranges 1 and 2 within the monitored peak value range 3 (see FIG. 4) to be monitored, and The fluctuating monitoring peak value range 3 is corrected.

[Description of operation]
Next, operation of the radiation monitoring apparatus 100 will be described.
FIG. 5 is a diagram showing temporal relationships among output signals of the scintillation detector 11, measuring device 12a, measuring device 12b, and measuring device 12c.
Reference numerals 401 to 404 denote output signals from the scintillation detector 11 (see FIG. 1), reference numeral 411 denotes output signals from the measuring device 12a, reference numeral 421 denotes output signals from the measuring device 12b, and reference numerals 431 to 433 denote output signals from the measuring device 12c. be.

As shown in FIG. 5, among the signals output from the scintillation detector 11, those signals (for example, the output signal 404) that do not fall within the monitoring peak value range 3 are not monitored. Among the output signals of the scintillation detector 11, when the signal 401 falling within the peak value range 1 is input to the measuring device 12a, the measuring device 12a outputs the logic pulse 411 shown in FIG. Output to the counting unit 101a. output. Similarly, when a signal 402 in the crest value range 2 among the output signals of the scintillation detector 11 is input to the measuring device 12b, the measuring device 12b converts the logic pulse 421 shown in FIG. 101b.

When the signals 401, 403, and 402, among the output signals of the scintillation detector 11, which fall within the monitoring peak value range 3 are input to the measuring device 12c, the measuring device 12c outputs the logic pulses 431, 432, and 433 shown in FIG. It is output to the counting unit 101c of the monitoring device 14 (see FIG. 1).

<Operation of analysis device 13>
As shown in FIG. 1, the counting unit 101a of the analysis device 13 (see FIG. 1) counts the number of logic pulses output from the measuring device 12a and outputs the counting result to the counting rate ratio calculating unit 102. The counting unit 101b counts the number of logic pulses output from the measuring device 12b and outputs the counting result to the counting rate ratio calculating unit 102 .
The counting rate ratio calculation unit 102 calculates a counting rate ratio based on the counting results obtained by the counting units 101a and 101b.

Further, the relationship between the peak value fluctuation amount and the counting rate ratio is stored in advance in the temperature fluctuation correction database 103 . Since the temperature fluctuation correction database 103 has the relationship of Equation (3), the logarithm of the count rate ratio and the peak value fluctuation amount have a linear function relationship.

The peak value range calculator 104 refers to the temperature fluctuation correction database 103 based on the count rate ratio calculated by the count rate ratio calculator 102 to calculate the peak value fluctuation amount.
The peak value range calculator 104 corrects the peak value range setting values 105a, 105b, and 105c set by the measuring devices 12a, 12b, and 12c based on the calculated peak value variation. At this time, the peak value range setting values 105a and 105b do not necessarily need to be corrected if the peak value range after the peak value fluctuation is within the range of the peak value range setting value 105c. The peak value range setting value 105c needs to be corrected when there is a variation in the peak value. The peak value range calculator 104 corrects the monitored peak value range 3 of the peak value range setting value 105c so that the calculated peak value fluctuation amount becomes smaller.
By adjusting the above for each measurement or dynamically, it is possible to continue monitoring corresponding to peak value fluctuations during continuous monitoring.

<Operation of monitoring device 14>
As shown in FIG. 1, the counting unit 101c of the monitoring device 14 (see FIG. 1) counts the number of logic pulses output from the measuring device 12c.
The monitoring device 14 acquires the peak value of the monitoring peak value range 3 of the peak value range setting value 105c to monitor the radiation.

FIG. 6 is a diagram showing actual measurement data of peak values. The vertical axis represents the change [ch] in the estimated peak value, and the horizontal axis represents the change [ch] in the actual peak value. As shown in FIG. 6, it was found that the actual measurement data of the wave height value has a positive correlation with the estimated wave height value. It was confirmed that it can adapt to the temperature fluctuating field.

As described above, the radiation monitoring apparatus 100 according to the present embodiment includes at least three measuring devices 12a, 12b, and 12c for measuring the signal of the peak value range of the scintillation detector 11, the analyzing device 13, and the monitoring device. 14 and prepare. The measuring devices 12a, 12b, and 12c acquire the output signal from the scintillation detector 11, and monitor the peak value range 3 to be monitored, in which the peak value fluctuates due to temperature changes, and at least two peak values within the monitored peak value range 3. Peak value range setting values 105a, 105b, and 105c for setting peak value ranges 1 and 2 are provided. The analysis device 13 includes counting units 101a and 101b, a counting rate ratio calculation unit 102 for calculating the ratio of the count rate between the peak value in the peak value range 1 and the peak value in the peak value range 2, and a temperature fluctuation correction database 103. , and a peak value range calculator 104 . The peak value range calculator 104 refers to the temperature variation correction database 103 to calculate the peak value fluctuation amount from the ratio of the counting rates. Further, the peak value range calculator 104 corrects the monitored peak value range 3 so that the calculated peak value fluctuation amount becomes smaller.

With this configuration, it is possible to immediately calculate the peak value fluctuation amount without the need for temperature measurement, and adjust (correction )can do. That is, the radiation monitoring apparatus 100 calculates the peak value fluctuation amount based on the ratio of the count rate of the peak value in the two peak value ranges 1 and 2 other than the temperature change, and monitors based on the peak value fluctuation amount. Peak value range 3 is corrected. As a result, continuous monitoring is possible without the time lag that occurs in the correction method based on temperature measurement. Therefore, continuous monitoring in a short time using the scintillation detector 11 can be realized in an environment with temperature fluctuations.

For example, if it is necessary to measure multiple times during the time delay between the location of a device that is affected by temperature such as a scintillator or photomultiplier tube and the location of temperature measurement, the crest value that is earlier than the temperature measurement is required. Although a correction method is required, in this embodiment, there is no need for temperature measurement, and the peak value fluctuation amount can be calculated immediately, so monitoring is possible without time delay accompanying correction by temperature measurement. Effective.

In the present embodiment, the peak value range calculation unit 104 calculates the peak value fluctuation amount based on the ratio of the count rate of the peak values of the peak values of the normal distribution in the peak value distribution to be monitored. As a result, the peak value fluctuation amount can be calculated (estimated) from the ratio of the count rates of the peak values in the two peak value ranges 1 and 2 other than the temperature change at the peak of the normal distribution. In particular, minimizing the number of processed signals enables fast response.
The two peak value ranges 1 and 2 may be any two points within the monitoring peak value range 3 .

In this embodiment, the peak value range calculation unit 104 calculates the peak value variation at high speed and with high accuracy by referring to the temperature variation correction database 103 that stores the relationship of the peak value variation with respect to the ratio of the counting rate. be able to.

In this embodiment, the radiation monitoring apparatus 100 can continue monitoring corresponding to peak value fluctuations during continuous monitoring by adjusting each measurement or dynamically.

In this embodiment, the radiation monitoring apparatus 100 estimates the current peak value fluctuation amount from the trend of change in the peak value fluctuation amount calculated by one or more measurements during continuous monitoring. As a result, it is possible to set the monitoring peak value range 3 in which the influence of errors is suppressed.

In this embodiment, by using a single channel analyzer for the measurement devices 12a, 12b, and 12c, the single channel analyzer counts two points within the peak range set for peak value fluctuation estimation and counts in the monitoring peak value range. measure. This allows a single channel analyzer to minimize the number of signals to be processed and enable fast response.

In this embodiment, the radiation monitoring apparatus 100 includes the monitoring device 14 that acquires the peak value of the monitoring peak value range 3 of the peak value range setting value 105c of the measuring device 12c (see FIG. 1) and monitors radiation. In order to adjust the monitoring range, the monitoring device 14 confirms whether the peak value range being monitored is appropriate as a result of the adjustment. Thereby, reliability can be improved.

(Second embodiment)
In the first embodiment, the temperature fluctuation correction database 103 is used, but since there is a relationship of expression (3), a configuration including the peak value fluctuation amount calculation unit 106 instead of the temperature fluctuation correction database 103 is also possible. .
FIG. 7 is a diagram showing the configuration of a radiation monitoring apparatus according to the second embodiment of the invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and descriptions of overlapping portions are omitted.
As shown in FIG. 7, the analysis device 13A of the radiation monitoring device 200 includes a peak value fluctuation calculation unit 106, a storage device 107, and a standard deviation database 108 instead of the temperature fluctuation correction database 103 of FIG. Prepare.

In Equation (3), the crest value at the center of the peak to be monitored is calculated. In order to calculate the peak value fluctuation amount from the difference from the peak value at the center of the peak one time before (n-1th time), the peak value at the center of the peak is stored each time the peak value fluctuation amount calculation unit 106 operates. A storage device 107 is provided.

Also, in equation (3), the standard deviation must be known. The standard deviation correlates with the peak center position. For this purpose, a standard deviation database 108 is provided for accumulating the standard deviation along with the crest value at the center of the peak.
Note that the peak values corresponding to x ₁ and x ₂ in equation (3) are input from the peak value range calculator 104 .

The operation of the radiation monitoring apparatus 200 configured as described above will be described below.
As shown in FIG. 7, when the output signal of the count rate ratio calculation unit 102 is input to the peak value fluctuation amount calculation unit 106, the peak value fluctuation amount calculation unit 106 obtains from the standard deviation database 108 one previous (n- The peak value and standard deviation at the peak center of the first time) are read, and the current (nth time) peak center value is calculated according to Equation (3). The calculated crest value is input to the standard deviation database 108 .

The peak value variation calculation unit 106 calculates the standard deviation based on the peak value at the center of the n-th peak, and transmits it to the storage device 107 as a set with the peak value at the center of the n-th peak. The peak value fluctuation amount calculation unit 106 calculates the peak value at the center of the n-th peak from the standard deviation read from the storage device 107 (n-1th time), and reads from the standard deviation database 108 (n-1th time ) from the peak value at the center of the peak, the peak value fluctuation amount is calculated and transmitted to the peak value range calculation unit 104 .

The peak value range calculation unit 104 corrects the peak value range setting values 105a, 105b, and 105c set by the measuring devices 12a, 12b, and 12c based on the calculated peak value fluctuation amount. At this time, the peak value range setting value 105c needs to be corrected at least when there is a variation in the peak value. On the other hand, the peak value range setting values 105a and 105b do not necessarily need to be corrected as long as the peak value range after the peak value fluctuation is within the range of the peak value range setting value 105c.

The peak value range setting values 105a and 105b are input to the peak value fluctuation amount calculation unit 106, and when calculating the peak value fluctuation amount from the peak value fluctuation amount calculation unit 106 according to the ratio of the next (n+1) count rate used for

As described above, in the second embodiment, the current peak value fluctuation amount is calculated (estimated) from the trend of change in the peak value fluctuation amount estimated by one or more measurements during continuous monitoring. As a result, it is possible to set the monitoring peak value range 3 in which the influence of errors is suppressed.

Further, in the second embodiment, by using the relationship of formula (3), the peak value fluctuation amount can be calculated without providing the temperature fluctuation correction database 103 (however, the standard deviation database 108 is not required). Become). Database resources are simplified, and cost reduction can be expected.

(Third Embodiment)
In the second embodiment, the (n−1) standard deviation is used as a method of deriving the standard deviation. This can be handled when the crest value fluctuation is minute. When the peak value fluctuation amount is large, it may be preferable to derive the peak value fluctuation amount based on the actually measured value.
FIG. 8 is a diagram showing the configuration of a radiation monitoring apparatus according to the third embodiment of the invention. The same components as those in FIG. 7 are denoted by the same reference numerals, and descriptions of overlapping portions are omitted.
As shown in FIG. 8, the analysis device 13B of the radiation monitoring apparatus 300 has a standard deviation calculation unit 109 and a storage device 110 instead of the peak value fluctuation amount calculation unit 106, the storage device 107 and the standard deviation database 108 in FIG. And prepare.
The analyzer 13B calculates the peak value fluctuation amount without using the (n−1)th standard deviation.

The operation of the radiation monitoring apparatus 300 configured as described above will be described below.
As shown in FIG. 8, when the count rate ratio is input to the crest value variation calculation unit 106, the standard deviation derivation unit 109 derives the standard deviation based on Equation (5). For the peak values corresponding to x ₁ and x ₂ in equation (5), the peak value range setting value 105 a and the peak value range setting value 105 b of the (n−1)th time are input from the peak value range calculator 104 . The peak value range setting value 105a and the peak value range setting value 105b of the (n−1)th time are also input to the peak value fluctuation amount calculation unit 106, and the ratio of the counting rate, the standard deviation, and the peak value range setting value from the nth time , the crest value at the center of the peak is calculated.
The peak value at the center of the obtained peak is input and stored in the storage device 110, and the peak value at the (n−1)th peak center is output from the storage device 110, and the peak value fluctuation amount calculation unit 106 is entered in In the peak value fluctuation amount calculating unit 106, the peak value fluctuation amount is calculated from the difference between the peak value at the center of the n-th peak and the peak value at the center of the (n-1)th peak. is entered.

The calculated peak value fluctuation amount is used by the peak value range calculator 104 to correct the peak value range setting values 105a, 105b, and 105c set in the measuring devices 12a, 12b, and 12c. At this time, the peak value range setting value 105c needs to be corrected at least when there is a variation in the peak value. On the other hand, the peak value range setting values 105a and 105b do not necessarily need to be corrected if the peak value range after the peak value fluctuation is within the range of the peak value range setting value 105c. In addition, the peak value range setting values 105a and 105b are input to the peak value fluctuation amount calculation unit 106 and the standard deviation derivation unit 109, and the peak value fluctuation amount calculation unit 106 outputs the peak value fluctuation amount calculation unit 106 according to the next (n+1) counting rate ratio. It is used when calculating the variation amount.

As described above, in the third embodiment, by using the relationship of Equation (5), the peak value fluctuation amount can be calculated without using the standard deviation database 108 as well. Database resources are simplified, and further cost reduction can be expected.

(Fourth embodiment)
The functions of the measurement devices 12a, 12b, 12c (see FIGS. 1, 7, and 8) that determine the crest value of the output signal of the scintillation detector 11 and output logic pulses are single-channel analyzers. Single-channel analyzers can accommodate fast signal processing speeds, eg, less than 1s. However, when using a single-channel analyzer, it is not possible to grasp the whole image of the peak value distribution, so it is not suitable for checking whether peaks are being monitored correctly.

In addition to this single-channel analyzer, there is a multi-channel analyzer as a device for analyzing peak values. A multi-channel analyzer is a device that collects the entire peak value range of interest and outputs the peak value distribution shown in FIG. Even if multi-channel analyzers are used as the measuring devices 12a, 12b, 12c, the radiation monitoring devices 100, 200, 300 of each embodiment operate normally. However, since the number of signals to be processed increases when using a multi-channel analyzer, there is a possibility that the processing cannot keep up with the high counting rate. Alternatively, if a high signal processing speed of, for example, less than 1 s is required, the multi-channel analyzer may not be able to handle the slow signal processing speed. Therefore, it is desirable that the measurement devices 12a, 12b, 12c be single-channel analyzers.

FIG. 9 is a diagram showing the configuration of a radiation monitoring apparatus provided with a peak value adjustment function by a multichannel analyzer according to the fourth embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and descriptions of overlapping portions are omitted.
The fourth embodiment is an example of using both a single-channel analyzer and a multi-channel analyzer.
As shown in FIG. 9, the radiation monitoring apparatus 400 includes single-channel analyzers 701a, 701b, and 701c, a multi-channel analyzer 702, and a crest value adjuster 703.
The peak value adjustment unit 703 compares both input peak values and determines the peak value adjustment amount necessary to make the peak value range setting value 105c the same range as the peak value range output from the multichannel analyzer 702. calculate.

As shown in FIG. 9, signals output from the scintillation detector 11 are input to single-channel analyzers 701a, 701b, and 701c. When the peak value of the input signal is within the peak value range setting 105a (peak value range 1: see FIG. 4), a logic pulse is output from the single channel analyzer 701a. Similarly, when the peak value of the input signal is within the peak value range setting 105b (peak value range 2: see FIG. 4), a logic pulse is output from the single channel analyzer 701b, and the peak value of the input signal is is within the peak value range setting 105c (monitored peak value range 3: see FIG. 4), a logic pulse is output from the single channel analyzer 701c.

A signal input to the multi-channel analyzer 702 forms a crest value distribution. That is, the signal input to the multichannel analyzer 702 is for monitoring the entire peak value range of interest. Monitoring by the multi-channel analyzer 702 can be slower signal processing than the single-channel analyzers 701a, 701b, and 701c, and takes a certain amount of time to form the crest value distribution. It is desirable that the constant time be within a range in which there is no peak value fluctuation. If there is no peak value fluctuation, it is confirmed that the peak value range setting value 105c is appropriate. In other words, when there is no peak value fluctuation, the multi-channel analyzer 702 adjusts the peak value range based on the peak value distribution obtained by measuring for a certain period of time during which there was no peak value fluctuation. Confirm that the set value 105c is valid.

The peak value range calculator 104 outputs the peak value range set value 105 c to the peak value adjuster 703 . The multi-channel analyzer 702 also outputs an appropriate peak value range to the peak value adjusting section 703 .
The peak value adjusting unit 703 compares both the peak value range setting value 105c that has been input with the peak value range of the appropriate peak, and the peak value range setting value 105c is the peak value range that is output from the multichannel analyzer 702. Calculate the amount of peak value adjustment necessary to have the same range as The peak value adjustment amount is input to the peak value range calculation unit 104, and the peak value range calculation unit 104 adjusts the deviation of the peak value based on the peak value adjustment amount.

Although the measurement time of the multi-channel analyzer 702 is set within a time period in which there is no peak value fluctuation, even if there is a peak value fluctuation, it is very small, and if the peak value range setting value 105c does not change, there is a problem even if the same operation is performed. There is no In addition, if the influence of peak value fluctuations on the peak value distribution can be grasped from the peak value fluctuations and time estimation, even if the peak value range setting value 105c is changed, the wave during measurement by the multichannel analyzer 702 Adjustments may be made based on the high price fluctuation amount.

It is difficult to apply the radiation monitoring apparatus 400 when the signal processing of the multi-channel analyzer cannot catch up with the high counting rate (such as when the dead time is 100%). On the other hand, in an environment where the radiation monitoring apparatus 400 cannot keep up with the required signal processing speed and signal processing itself is possible, it is possible to confirm whether monitoring is being performed appropriately.

As described above, in this embodiment, by applying a multi-channel analyzer instead of a single-channel analyzer, it is possible to estimate peaks at a plurality of points and estimate the crest value fluctuation amount by fitting. This enables monitoring without time delay associated with correction by temperature measurement.

In particular, in this embodiment, multi-channel peak value analysis is performed using signals branched from the continuous monitoring system, and the peak value range determined by the multi-channel peak value analysis is compared with that during monitoring when the peak value fluctuation is minute, Confirm or correct the crest range being monitored for validity. This makes it possible to correct deviations due to continuous measurements over a long period of time.

It should be noted that the present invention is not limited to the configurations described in the above embodiments, and the configurations can be changed as appropriate without departing from the gist of the present invention described in the claims.

Each of the embodiments described above has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the configurations described. Further, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. . Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

11 scintillation detector 12, 12a ~ 12c measuring device 13 analysis device 14 monitoring device 100, 200, 300, 400 radiation monitoring device 101a ~ 101c counting unit 102 counting rate ratio calculation unit 103 peak value fluctuation amount database 104 peak value range calculation unit 105a to 105c peak value range setting value 106 peak value variation calculation unit 107 storage device 108 standard deviation database 109 standard deviation derivation unit 110 storage device 701, 701a to 701c single channel analyzer 702 multichannel analyzer 703 peak value adjustment unit

Claims (7)

A radiation monitoring apparatus for monitoring radiation by acquiring an output signal from a scintillation detector that outputs a signal with a peak value corresponding to radiation energy,
a monitoring peak value range of a monitoring target in which the peak value fluctuates due to temperature changes; and peak value range setting means for setting at least two peak value ranges within the monitoring peak value range;
peak value variation calculation means for calculating a peak value variation based on a ratio of the count rates of the peak values in at least two of the peak value ranges;
a correction means for correcting the monitored peak value range so that the calculated peak value fluctuation amount becomes small ;
The peak value fluctuation amount calculation means is
calculating the peak value fluctuation amount based on the ratio of the count rate of the peak value of the peak having a normal distribution among the peak value distributions to be monitored;
Standard deviation storage means for storing the correlation between the standard deviation of the peak to be monitored and the center peak value of the peak,
The peak value fluctuation amount calculation means is
calculating a peak value fluctuation amount based on the correlation stored in the standard deviation storage means;
A radiation monitoring device characterized by: A radiation monitoring apparatus for monitoring radiation by acquiring an output signal from a scintillation detector that outputs a signal with a peak value corresponding to radiation energy,
a monitoring peak value range of a monitoring target in which the peak value fluctuates due to temperature changes; and peak value range setting means for setting at least two peak value ranges within the monitoring peak value range;
peak value variation calculation means for calculating a peak value variation based on a ratio of the count rates of the peak values in at least two of the peak value ranges;
correction means for correcting the monitored peak value range so that the calculated peak value fluctuation amount becomes smaller ;
standard deviation deriving means for deriving the standard deviation of the monitored peak based on the count rate ratio;
A second storage means for storing the center peak value and the standard deviation of the peak in at least one previous monitoring,
The peak value fluctuation amount calculation means is
A peak value fluctuation amount is calculated based on the correlation between the center peak value of the peak stored in the second storage means and the standard deviation.
A radiation monitoring device characterized by: A radiation monitoring apparatus for monitoring radiation by acquiring an output signal from a scintillation detector that outputs a signal with a peak value corresponding to radiation energy,
a monitoring peak value range of a monitoring target in which the peak value fluctuates due to temperature changes; and peak value range setting means for setting at least two peak value ranges within the monitoring peak value range;
peak value variation calculation means for calculating a peak value variation based on a ratio of the count rates of the peak values in at least two of the peak value ranges;
a correction means for correcting the monitored peak value range so that the calculated peak value fluctuation amount becomes small ;
The peak value fluctuation amount calculation means is
calculating the peak value fluctuation amount based on the ratio of the count rate of the peak value of the peak having a normal distribution among the peak value distributions to be monitored;
The peak position (m _n ) is represented by the following formula

however,
m _n : Center position of normal distribution (peak value adjustment amount)
x ₁ : peak value range 1 within monitoring peak value range 3
x ₂ : Peak value range 2 within monitoring peak value range 3
σ _n : standard deviation
F(x ₁ , x ₂ ): Count rate ratio
A radiation monitoring device characterized by: Storage means for pre-storing the correlation between the counting rate ratio and the peak value fluctuation amount,
The peak value fluctuation amount calculation means is
2. The radiation monitoring apparatus according to claim 1, wherein the peak value fluctuation amount is calculated based on the correlation stored in the storage means. a multi-channel analyzer that adjusts the monitoring peak value range;
Compare the monitored peak value range indicated by the multi-channel analyzer and the peak value range of the peak being monitored, and if there is a difference, the peak value range is the monitored peak value range output from the multi-channel analyzer. 3. The radiation monitoring apparatus according to claim 1 , further comprising: a peak value adjustment unit that calculates a peak value adjustment amount that makes the range to be the same. The standard deviation (σ _n ) is represented by the following formula

however,
m _n : Center position of normal distribution (peak value adjustment amount)
x ₁ : peak value range 1 within monitoring peak value range 3
x ₂ : Peak value range 2 within monitoring peak value range 3
σ _n : standard deviation F(x ₁ , x ₂ ): count rate ratio The radiation monitoring apparatus according to claim 1 or 2 . A radiation monitoring apparatus for monitoring radiation by acquiring an output signal from a scintillation detector that outputs a signal with a peak value corresponding to radiation energy,
a monitoring peak value range of a monitoring target in which the peak value fluctuates due to temperature changes; and peak value range setting means for setting at least two peak value ranges within the monitoring peak value range;
peak value variation calculation means for calculating a peak value variation based on a ratio of the count rates of the peak values in at least two of the peak value ranges;
correction means for correcting the monitored peak value range so that the calculated peak value fluctuation amount becomes smaller ;
a multi-channel analyzer that adjusts the monitoring peak value range;
Compare the monitored peak value range indicated by the multi-channel analyzer and the peak value range of the peak being monitored, and if there is a difference, the peak value range is the monitored peak value range output from the multi-channel analyzer. and a peak value adjustment means for calculating a peak value adjustment amount that makes the same range,
The peak value fluctuation amount calculation means is
A peak value fluctuation amount is calculated based on the ratio of the count rate of the peak value of the peak having a normal distribution in the peak value distribution to be monitored.
A radiation monitoring device characterized by:

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