JP5748306B2 - Radioactivity measuring device - Google Patents

Description

  The present invention relates to a radioactivity measurement apparatus.

  Conventionally, there has been known a method for preventing an unnecessarily long measurement time by indicating whether or not a measurement value exceeds a predetermined limit value in radioactivity measurement. (For example, refer to Patent Document 1). In this method, the maximum measurement time corresponding to the detection limit is calculated, individual measurements for a time shorter than the maximum measurement time are performed a plurality of times, and based on the measurement values obtained in each of the plurality of individual measurements. Thus, the probability that the average value of the measurement values obtained when the individual measurement is continued exceeds the limit value is calculated, and the necessity of continuing the measurement is determined according to this probability.

JP-T-2004-511784

By the way, in the method according to the related art, even before the maximum measurement time corresponding to the detection limit is reached, the measurement may be terminated based on the probability that the measurement value exceeds the limit value. However, if the calculation accuracy of the probability that the measurement value exceeds the limit value is low, the measurement may end in a measurement time that is too short, and whether or not the calculation accuracy of this probability is sufficiently high. Therefore, it is not possible to determine whether or not an appropriate measurement time can be set according to this probability.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radioactivity measurement apparatus capable of properly terminating measurement in a measurement time required to ensure a target detection limit. It is said.

In order to solve the above problems and achieve the object, the present invention employs the following aspects.
(1) A radioactivity measurement apparatus according to an aspect of the present invention includes a radiation detector that detects radiation emitted from a sample (for example, the radiation detector 15 in the embodiment), and the radiation detector detects the radiation. Processing means for automatically analyzing the energy spectrum of the radiation (for example, the processing device 13 in the embodiment), and the processing means has a target detection limit radioactivity for each of at least one detection target nuclide. The processing means sets the total absorption peak from the energy spectrum of the radiation at a plurality of timings during the period in which the radiation is detected by the radiation detector in the automatic analysis of the energy spectrum of the radiation. searching, calculating the nuclide corresponding to the total absorption peak, the corresponding to the total absorption peak after setting the peak area of the whole peak Calculating species of radioactivity and no rows calculated and out of the detection limit radioactivity of the radionuclide, the processing means, for all of the detected species in each of the plurality of timing, the detection limit radioactivity the It is determined whether or not the number of consecutive times that is less than the target detection limit radioactivity is a predetermined number or more, and when it is determined that the number of continuous times is the predetermined number or more for all the detection target nuclides, the radiation The detection of the radiation by the detector and the automatic analysis of the energy spectrum of the radiation are terminated.

(2) The radioactivity measurement apparatus according to (1) includes a display device (for example, the output device 12 in the embodiment), and the processing unit calculates the detection target nuclide calculated at each of the plurality of timings. The time series change of the detection limit radioactivity for each may be displayed on the display device.

(3) In the radioactivity measurement apparatus according to (2), the processing unit performs the time series change of the detection limit radioactivity for each of the detection target nuclides calculated at each of the plurality of timings. The arrival timing when the detection limit radioactivity becomes less than the target detection limit radioactivity for each detection target nuclide may be predicted, and the arrival timing may be displayed on the display device.
(4) In the radioactivity measurement apparatus according to any one of (1) to (3) above, the detection limit radioactivity is less than the target detection limit radioactivity for all the detection target nuclides. You may provide the display part which displays the screen for setting the target value with respect to the frequency | count or time to determine continuously.
(5) In the radioactivity measurement apparatus according to any one of (1) to (3), the processing means has the detection limit radioactivity that is the target detection limit radiation for all the detection target nuclides. The target value for the number of times or time that is continuously determined to be less than the performance may be set to a fixed value.
(6) The radioactivity measurement apparatus according to any one of (1) to (5) instructing whether or not to perform measurement using the target detection limit radioactivity set for each detection target nuclide. A display unit for displaying a screen for the purpose may be provided.

  According to the radioactivity measuring apparatus according to the aspect described in (1) above, whether or not the continuous number of times that the detection limit radioactivity is less than the target detection limit radioactivity for all detection target nuclides is a predetermined number or more. Therefore, it is possible to make an appropriate determination in consideration of statistical variations in radioactivity. Thereby, a measurement can be appropriately complete | finished in the measurement time required in order to ensure the target detection limit radioactivity.

  In the case of (2) above, the operator can easily visually recognize the timing at which the detection limit radioactivity for each detection target nuclide reaches the target detection limit radioactivity.

  In the case of (3) above, the operator can easily grasp the timing of the end of measurement.

It is a block diagram of the radioactivity measuring apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the home screen displayed on a display apparatus at the time of the action | operation of the wave height analyzer of the radioactivity measuring apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the setting screen of the target detection limit radioactivity of the radioactivity measuring apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the setting screen of the sample analysis of the radioactivity measuring apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the detection limit monitor screen of the radioactivity measuring apparatus which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radioactivity measuring apparatus which concerns on embodiment of this invention.

Hereinafter, a radioactivity measurement apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the radioactivity measurement apparatus 10 according to the present embodiment includes an input device 11, an output device 12, a processing device 13, a pulse height analyzer 14, and a radiation detector 15.
The input device 11 includes, for example, various switches and a keyboard that output signals according to the input operation of the operator, and transmits various command signals according to the input operation of the operator to the processing device 13.
The output device 12 includes a speaker and a display device, and outputs various types of information received from the processing device 13.

The wave height analyzer 14 is, for example, a multi-channel analyzer, and calculates the wave height distribution of the output signal pulse output from the radiation detector 15, that is, the count value for each of a plurality of channels set according to the wave height value. For example, when an output signal pulse having a peak value corresponding to the energy of radiation emitted from the sample is output from the radiation detector 15, the pulse height analyzer 14 uses the energy distribution as the pulse height distribution of the output signal pulse of the radiation detector 15. Create a spectrum.
The radiation detector 15 is a semiconductor detector such as germanium, and detects radiation (for example, γ-rays, X-rays, etc.) emitted from the sample.

The processing device 13 includes a storage unit 21 and a calculation unit 22.
The storage unit 21 stores, for example, various types of preset data, calculation result data of the calculation unit 22, data output from the wave height analyzer 14, and the like. The various types of data set in advance are, for example, nuclear data of a plurality of nuclides (for example, energy of emitted radiation) and peak efficiency data at the energy of all absorption peaks of the radiation detector 15.

  The calculation unit 22 uses the nuclear data of a plurality of nuclides stored in the storage unit 21 and the peak efficiency data at the energy of all absorption peaks of the radiation detector 15 to detect the radiation detected by the radiation detector 15. Automatically analyze the energy spectrum of. The calculation unit 22 searches for the total absorption peak and total absorption from the energy spectrum of the radiation collected cumulatively at a plurality of timings with a predetermined monitoring interval during the period in which the radiation detector 15 detects the radiation. The calculation of the nuclide corresponding to the peak, the radioactivity of the nuclide, and the detection limit radioactivity (MDA) for the detection target nuclide among the identified nuclides are automatically performed.

  Accordingly, the calculation unit 22 acquires various parameters required for the analysis by an operator's input operation on the input device 11 or the like, prior to the automatic analysis of the radiation energy spectrum. The various parameters are at least one or more detection target nuclides, a standby time from the start of detection of radiation by the radiation detector 15 until the first detection limit radioactivity is calculated, and a time interval for calculating the detection limit radioactivity. Monitoring interval, target value of detection limit radioactivity for each detection target nuclide (target detection limit radioactivity), target number of continuous determination times, and the like.

The processing device 13 causes the display device of the output device 12 to display a screen display for allowing the operator to input various parameters.
For example, as shown in FIG. 2, the processing device 13 includes a button 32 a for instructing setting of the target detection limit radioactivity on the home screen 31 displayed on the display device when the wave height analyzer 14 is operated, and a plurality of timings. A switching tab 32 including a button 32b for instructing display of a time-series change of the detection limit radioactivity calculated in step S3 is displayed.
Then, when the button 32a for instructing the setting of the target detection limit radioactivity is selected and operated by the operator, the processing device 13 displays a target detection limit radioactivity setting screen 33 as shown in FIG. Display on the display device. On the setting screen 33, the processing device 13 includes a switching tab 34 having buttons 34a and 34b for instructing registration and cancellation of various setting contents, and buttons 35a and 35b for instructing addition and deletion of detection target nuclides. The switching tab 35 provided is displayed. Further, the processing device 13 uses the setting screen 33 to display a screen 36 for setting a standby time, a monitor interval, a continuous determination number target value (number of times of arrival), and the like, and a target detection limit radioactivity for each detection target nuclide. A screen 37 for setting is displayed.

  In addition, as shown in FIG. 4, the processing device 13 performs measurement using the target detection limit radioactivity set for each detection target nuclide in a state where the sample analysis setting screen 38 is displayed on the display device. Instruct. In the setting screen 38, the processing device 13 displays a screen 39 for instructing setting of measurement information and a screen 40 for instructing whether or not to perform measurement using the target detection limit radioactivity.

In the processing device 13, on the home screen 31 shown in FIG. 2, the button 32 b for instructing the display of the time series change of the detection limit radioactivity (MDA calculated value) calculated at a plurality of timings is selected and operated by the operator. In this case, as shown in FIG. 5, the detection limit monitor screen 41 displays a time series change of the detection limit radioactivity on the display device. When displaying the time series change of the detection limit radioactivity, the processing device 13 further displays the result of function fitting by an appropriate function (MDA change prediction) and the target detection limit radioactivity (MDA target value). To do.
Furthermore, the processing device 13 has a detection limit radioactivity that is less than the target detection limit radioactivity for each detection target nuclide according to the time-series change of the detection limit radioactivity for each detection target nuclide calculated at each of a plurality of timings. The arrival timing is predicted, and the predicted arrival timing (scheduled arrival date and time) is displayed on the detection limit monitor screen 41. Furthermore, the processing device 13 sets the arrival timing ((expected arrival date and time) all nuclides) at which the detection limit radioactivity of all detection target nuclides is less than the target detection limit radioactivity based on the arrival timing predicted for each detection target nuclide. It is displayed on the detection limit monitor screen 41. Further, the processing device 13 calculates the number of continuous determinations for which the detection limit radioactivity is less than the target detection limit radioactivity for all detection target nuclides at each of a plurality of timings, ) Is displayed on the detection limit monitor screen 41.

The processing device 13 determines whether or not the number of continuous determinations at which the detection limit radioactivity of all detection target nuclides is less than the target detection limit radioactivity is greater than or equal to the target number of continuous determinations at each of a plurality of timings. When the processor 13 determines that the number of continuous determinations is equal to or greater than the target number of continuous determinations for all detection target nuclides, the processing device 13 automatically detects the radiation by the radiation detector 15 and the radiation energy spectrum. End the analysis.
For example, when the determination result as shown in Table 1 below is obtained in a state where the target number of consecutive determinations is set to 3 for the two detection target nuclides A and B, the processing device 13 When the second determination is completed, it is determined that the number of continuous determinations for all the detection target nuclides A and B is equal to or greater than the target number of continuous determinations, and the detection and analysis of radiation are ended.

  In addition to the determination result as to whether or not the continuous determination count is equal to or greater than the target value of the continuous determination count, the processing device 13 sets a time preset for a preset measurement time or a count preset for the detection limit radioactivity determination count. Accordingly, the detection of radiation by the radiation detector 15 and the automatic analysis of the energy spectrum of the radiation may be terminated.

  The radioactivity measurement apparatus 10 according to this embodiment has the above-described configuration. Next, the operation of the radioactivity measurement apparatus 10 will be described.

First, in step S01 shown in FIG. 6, the processing device 13 determines whether or not the target value (target detection limit radioactivity) of the detection limit radioactivity (MDA) is input for each detection target nuclide.
When this determination result is “NO”, the processing device 13 advances the processing to the end.
On the other hand, if the determination result is “YES”, the processing device 13 advances the process to step S02.

Next, in step S <b> 02, the processing device 13 determines whether or not a target value (continuous determination number target value) of the continuous determination number (N) is input.
When this determination result is “NO”, the processing device 13 advances the processing to the end.
On the other hand, when the determination result is “YES”, the processing device 13 advances the process to step S03.
Next, in step S03, the processing device 13 sets zero for the continuous determination number (N) and initializes the continuous determination number (N).

Next, in step S04, the processing device 13 determines whether or not an operation start of the wave height analyzer 14 is instructed.
When this determination result is “NO”, the processing device 13 advances the processing to the end.
On the other hand, when the determination result is “YES”, the processing device 13 advances the process to step S05.

Next, in step S05, the processing device 13 determines whether or not a predetermined standby time has elapsed since the start of operation of the wave height analyzer 14 was instructed.
When the determination result is “NO”, the processing device 13 repeatedly executes the process of step S05.
On the other hand, when the determination result is “YES”, the processing device 13 advances the process to step S06.
Next, in step S06, the processing device 13 collects the energy spectrum of the radiation detected by the radiation detector 15.
Next, in step S07, the processing device 13 performs a search for all absorption peaks with respect to the energy spectrum of radiation.

Next, in step S08, the processing device 13 sets a peak area of all absorption peaks.
Next, in step S09, the processing device 13 calculates a detection limit radioactivity (MDA) for each detection target nuclide among the nuclides corresponding to all absorption peaks.
Next, in step S10, the processing device 13 uses an appropriate function to change the detection limit radioactivity after the current time according to the time-series change of the detection limit radioactivity for each detection target nuclide calculated at each of a plurality of timings. The function is predicted using function fitting, and the predicted change in detection limit radioactivity is displayed on the display device.

Next, in step S11, the processing apparatus 13 determines whether or not the calculated detection limit radioactivity is less than the target detection limit radioactivity for all detection target nuclides.
When the determination result is “NO”, the processing device 13 advances the process to step S12.
On the other hand, when the determination result is “YES”, the processing device 13 advances the process to step S13.
In step S12, the processing device 13 sets zero for the continuous determination number (N) and initializes the continuous determination number (N). Then, the process returns to step S06.
In step S <b> 13, the processing device 13 newly sets a value obtained by adding “1” to the number of continuous determinations (N) at this time as the number of continuous determinations (N).

In step S14, the processing device 13 determines whether or not the continuous determination number (N) is equal to or greater than the continuous determination number target value, or whether or not the measurement time or the determination number has reached a time preset or a count preset. judge.
If the determination result is “NO”, the processing device 13 returns the process to step S06.
On the other hand, when the determination result is “YES”, the processing device 13 advances the process to step S15.
Next, in step S <b> 15, the processing device 13 stops the operation of the wave height analyzer 14.
Next, in step S <b> 16, the processing device 13 collects the energy spectrum of the radiation detected by the radiation detector 15 after it is determined that the continuous determination number (N) has reached the continuous determination number target value or more.
Next, in step S <b> 17, the processing device 13 calculates the detection limit radioactivity for each detection target nuclide among the nuclides corresponding to all the absorption peaks, using the energy spectrum of the radiation collected at this time. Then, the process proceeds to the end.

As described above, according to the radioactivity measurement apparatus 10 according to the present embodiment, the number of continuous determinations for which the detection limit radioactivity is less than the target detection limit radioactivity for all detection target nuclides is equal to or greater than the target value of the continuous determination number Therefore, it is possible to make an appropriate determination in consideration of statistical variation in radioactivity. Thereby, a measurement can be appropriately complete | finished in the measurement time required in order to ensure the target detection limit radioactivity.
Furthermore, since the time series change of the detection limit radioactivity for each detection target nuclide calculated at each of the plurality of timings is displayed on the display device, the timing at which the detection limit radioactivity for each detection target nuclide reaches the target detection limit radioactivity Can be easily recognized visually by the operator.
Furthermore, since the arrival timing at which the detection limit radioactivity is less than the target detection limit radioactivity is predicted for each detection target nuclide, and the arrival timing is displayed on the display device, the operator can easily grasp the measurement end timing. it can.

  The above-described embodiments are presented as examples, and are not intended to limit the scope of the invention. The above-described novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The above-described embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

For example, in the above-described embodiment, the continuous determination frequency target value may be a fixed value set in advance.
In the above-described embodiment, at least one of the standby time and the monitoring interval may be a fixed value set in advance.

  For example, in the above-described embodiment, the radiation detector 15 is a semiconductor detector such as germanium, but is not limited thereto, and may be another detector such as a scintillation detector.

DESCRIPTION OF SYMBOLS 10 ... Radioactivity measuring device 11 ... Input device 12 ... Output device 13 ... Processing apparatus (processing means) 14 ... Wave height analyzer 15 ... Radiation detector 21 ... Memory | storage part 22 ... Calculation part

Claims (6)

A radiation detector for detecting radiation emitted from the sample;
Processing means for automatically analyzing the energy spectrum of the radiation detected by the radiation detector;
With
The processing means includes
Set the target detection limit radioactivity for at least one detection target nuclide,
The processing means includes
In automatic analysis of the energy spectrum of the radiation,
Search of the total absorption peak from the energy spectrum of the radiation at a plurality of timings during the period in which the radiation is detected by the radiation detector, calculation of nuclides corresponding to the total absorption peak, peak region of the total absorption peak calculation of radioactivity nuclide corresponding to the total absorption peak after setting the and no rows calculated and out of the detection limit radioactivity of the radionuclide,
The processing means includes
For each of the detection target nuclides at each of the plurality of timings, determine whether or not the continuous number of times that the detection limit radioactivity is less than the target detection limit radioactivity is a predetermined number or more,
When it is determined that the number of consecutive times is equal to or greater than the predetermined number for all the detection target nuclides, the detection of the radiation by the radiation detector and the automatic analysis of the energy spectrum of the radiation are terminated.
A radioactivity measuring apparatus characterized by that. A display device,
The processing means causes the display device to display a time-series change in the detection limit radioactivity for each of the detection target nuclides calculated at each of the plurality of timings.
The radioactivity measuring apparatus according to claim 1. The processing means is configured to convert the detection limit radioactivity for each detection target nuclide into the target detection limit radiation according to a time series change of the detection limit radioactivity for each detection target nuclide calculated at each of the plurality of timings. Predicting the arrival timing that is less than the ability, and displaying the arrival timing on the display device,
The radioactivity measuring apparatus according to claim 2. A display unit for displaying a screen for setting a target value for the number of times or time to continuously determine that the detection limit radioactivity is less than the target detection limit radioactivity for all the detection target nuclides;
The radioactivity measurement apparatus according to any one of claims 1 to 3, wherein The processing means sets a target value for the number of times or time to continuously determine that the detection limit radioactivity is less than the target detection limit radioactivity for all the detection target nuclides to a fixed value.
The radioactivity measurement apparatus according to any one of claims 1 to 3, wherein A display unit that displays a screen for instructing whether to perform measurement using the target detection limit radioactivity set for each detection target nuclide;
The radioactivity measurement apparatus according to any one of claims 1 to 5, wherein

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