JP2017072381A - Radiation measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly conduct processing for suppressing a measurement error of radiation.SOLUTION: A detection unit 30 is configured to generate a detection signal in accordance with radiation entering an ionization chamber 12, and output the detection signal to a computation processing unit 32. The computation processing unit 32 is configured to discretize the detection signal, and determine whether a first detection value, a second detection value and a third detection value sequentially generated as time goes by meet a peak formation condition, in which the peak formation condition means a condition that the second detection value is a peak value with respect to the first detection and the third detection value. The computation processing unit 32 is configured to, when the peak formation condition is met, obtain a modification value on the basis of at least one of the first detection value and the third detection value, and determine the modification value as a radiation measurement value corresponding to the second value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radiation measuring instrument, and more particularly to an improvement in a process for measuring radiation.

  Radiation measuring instruments that measure radiation such as β-rays and γ-rays are widely used. Some radiation measuring instruments have an ionization chamber filled with gas. When radiation enters the ionization chamber, the gas in the ionization chamber is ionized by the radiation. The radiation measuring instrument measures the radiation dose based on the current from the electrons collected from the ionized gas to the electrodes in the ionization chamber.

  The ionization chamber is often filled with the air of the factory to be adjusted from the viewpoint of reducing manufacturing costs. However, air may contain radon or thoron that emits alpha rays. Therefore, when air is used as the gas sealed in the ionization chamber, alpha rays unnecessary for radiation measurement are detected, and an error may occur when measuring radiation reaching the inside from the outside of the ionization chamber. is there.

  Therefore, as described in Patent Document 1 below, a radiation measurement apparatus that suppresses the influence of α rays in the ionization chamber is considered. In this radiation measuring apparatus, while a voltage measurement value is obtained based on the integral value of the voltage signal output from the ionization chamber, the number of detections per unit time of α rays is obtained as a count rate based on the differential value of the voltage signal. It is done. Then, by converting the α ray count rate into a voltage value and subtracting the converted value from the voltage measurement value, a radiation measurement value in which the influence of α rays is suppressed is obtained.

JP 2001-116844 A

  In the radiation measurement apparatus described in Patent Document 1, an error in the radiation measurement value is obtained by converting the α-ray count rate into a voltage value. However, the process for obtaining the α ray counting rate requires a long time because it is necessary to count α rays over a certain length of time.

  An object of the present invention is to quickly perform a process for suppressing a measurement error of radiation.

  According to the present invention, a detection unit that detects radiation by an ionization chamber, and a first detection value, a second detection value, and a third detection value that are sequentially obtained from the detection unit as time elapses are peak formation conditions, A determination unit that determines whether or not a second detection value satisfies a peak formation condition that is a peak value for the first detection value and the third detection value; and when the peak formation condition is satisfied, A correction unit that calculates a correction value based on at least one of a detection value and the third detection value; and when the peak formation condition is satisfied, the correction value is a radiation measurement value corresponding to the second detection value A measurement value determining unit.

  In general, when a time waveform of detected values sequentially detected with the passage of time by an ionization chamber shows a peak, the peak is often caused by specific radiation such as α rays. Therefore, when the above-described peak formation condition is satisfied, there is a high possibility that the second detection value is a peak value based on specific radiation. According to the present invention, when the peak formation condition is satisfied, the correction value is obtained based on at least one of the first detection value and the third detection value. And the radiation measurement value by which the error component based on specific radiation was suppressed is obtained by making the correction value into the radiation measurement value corresponding to a 2nd detection value. According to the present invention, a radiation measurement value in which a component based on specific radiation is suppressed is obtained by three detection values obtained in time series. Since the three detection values need only be obtained at a time interval necessary for determining whether or not the peak formation condition is satisfied, the processing for suppressing the error component is quickly performed.

  Desirably, the peak formation condition is such that a first difference, which is a difference between the second detection value and the first detection value, is equal to or greater than a predetermined first determination value, and the second detection with respect to the third detection value. It includes a condition that the second difference, which is a difference in values, is greater than or equal to a predetermined second determination value.

  In general, when specific radiation is detected by an ionization chamber, it often shows a time waveform that rises and falls within a predetermined time range and a predetermined level range. According to the present invention, it is possible to determine whether or not a peak formation condition for specific radiation is satisfied by appropriately setting the first determination value and the second determination value.

  Preferably, a smoothing unit that performs a smoothing process on a detection value detected by the detection unit is provided, and the determination unit includes the first determination value and the second determination unit according to a degree of smoothing performed by the smoothing unit. Set the judgment value.

  The time waveform indicated by each detection value subjected to the smoothing process varies depending on the degree of smoothing by the smoothing unit. According to the present invention, the first determination value and the second determination value are set according to the degree of smoothing by the smoothing unit. For this reason, whether or not the peak formation condition is satisfied is appropriately determined according to the degree of smoothing.

  Preferably, the measurement value determining unit sets a value based on the second detection value as a radiation measurement value corresponding to the second detection value when the peak formation condition is not satisfied.

  According to the present invention, when the peak formation condition is not satisfied, the correction value for the second detection value is not a radiation measurement value. Therefore, a component based on the radiation to be measured can be reflected in the radiation measurement value.

  According to the present invention, it is possible to quickly perform a process for suppressing radiation measurement errors.

It is a perspective view of the radiation measuring instrument which concerns on embodiment of this invention. It is a figure which shows the structure of an ionization chamber and a measurement part. It is a figure which shows the detection value after a detection signal and smoothing. It is a figure which shows a measured value and the signal for a display. It is a figure which shows the detection value after a detection signal and smoothing. It is a figure which shows the signal for a display. It is a figure which shows the structure of an arithmetic processing part. It is a flowchart which shows an alpha ray component reduction process. It is a figure which shows the example of a detected value and a measured value notionally.

  FIG. 1 is a perspective view of a radiation measuring instrument 10 according to an embodiment of the present invention. The radiation measuring instrument 10 includes an ionization chamber 12 and a measurement unit 14. The ionization chamber 12 is filled with air. The ionization chamber 12 has a structure for collecting electrons from the air ionized by the radiation incident on the ionization chamber 12. The measurement unit 14 measures the radiation dose based on electrons collected from the ionized air. A display unit 18 is provided on the front panel 16 of the measurement unit 14, and a measurement result is displayed on the display unit 18. An operation button 20 is provided on the front panel 16 and is operated by the user during measurement. The radiation measuring instrument 10 may be used as a portable measuring instrument.

  FIG. 2 schematically shows the configurations of the ionization chamber 12 and the measurement unit 14. The measurement unit 14 includes an operation unit 22, a control unit 24, a detection unit 30, a high pressure generation unit 31, an arithmetic processing unit 32, and a display unit 18. The operation unit 22 includes operation buttons and the like provided on the front panel. The control unit 24 performs overall control of the radiation measuring instrument 10. For example, the control unit 24 executes control for starting or ending measurement and control for switching information to be displayed on the display unit 18 according to the operation of the operation unit 22. In this case, the operation unit 22 outputs operation information corresponding to the user operation to the control unit 24. The control unit 24 controls the detection unit 30, the high voltage generation unit 31, the arithmetic processing unit 32, or the display unit 18 according to the operation information.

  When radiation enters the ionization chamber 12, the air in the ionization chamber 12 is ionized. A collector electrode 26 is provided inside the ionization chamber 12, and an electrode layer 28 is provided on the inner surface of the ionization chamber 12. The collector electrode 26 is electrically connected to the detection unit 30. The electrode layer 28 is electrically connected to the high voltage generator 31. The electrode layer 28 applies a DC voltage with the electrode layer 28 side negative between the collector electrode 26 and the electrode layer 28. As a result, the collector electrode 26 has a high potential with respect to the electrode layer 28, and an electric field is generated between the collector electrode 26 and the electrode layer 28. Due to this electric field, electrons in the ionized air are collected on the collector electrode 26. As a result, a detection current flows through the collector electrode 26. The detection unit 30 includes a circuit that generates a detection signal by causing a detection current to flow through a circuit element such as a resistor to generate a voltage. The detection unit 30 generates a detection signal based on the detected current and outputs the detection signal to the arithmetic processing unit 32.

  The arithmetic processing unit 32 performs an α-ray component reduction process for reducing a component based on the α-ray (hereinafter referred to as an α-ray component) on the detection signal to generate a display signal. The arithmetic processing unit 32 outputs a display signal to the display unit 18, and the display unit 18 displays the measured value.

  An outline of the processing executed by the arithmetic processing unit 32 will be described with reference to FIGS. 3A, 3B, 4A, and 4B. FIG. 3A (a) shows an outline of the time waveform of the detection signal V (t) output from the detection unit 30 to the arithmetic processing unit 32. The horizontal axis indicates time t, and the vertical axis indicates the value of the detection signal V (t). In the detection signal V (t), a peak due to an α-ray component appears between times t = 8T to 10T.

  The arithmetic processing unit discretizes the detection signal V (t) at intervals of the extraction time T, and each detection value V (i) (i =... 0, 1, 2, 3, 3) obtained by discretization. ...)) Is smoothed. The smoothing process is a process of smoothing the time waveform obtained if each detected value is interpolated. FIG. 3A (b) shows the detection value V (i) after the smoothing process. The horizontal axis represents the time variable i, and the vertical axis represents the detected value V (i). The difference between the peak value of the detection value due to the α-ray component and the detection values before and after the smoothing process with an appropriate smoothing degree becomes large.

  For each time t = iT, the arithmetic processing unit has a detection value increase amount V (i) −V (i−1) per extraction time T that is equal to or greater than a predetermined determination value D1, and the time per extraction time T. When the peak formation condition that the decrease amount V (i) −V (i + 1) of the detection value is equal to or greater than the predetermined determination value D2 is satisfied, the average value of the detection values V (i + 1) and V (i−1) is calculated. The measured value Z (i) corresponding to the time variable i is assumed. The determination values D1 and D2 may be the same value or different values.

  On the other hand, when the peak formation condition is not satisfied, the arithmetic processing unit directly sets the detected value V (i) as the measured value Z (i) corresponding to the time variable i.

  In FIG. 3A (b), the peak formation condition is satisfied for the detected value V (9). Therefore, [V (10) + V (8)] / 2 is defined as a measured value Z (9). The other measured value Z (i) is set as a detected value V (i). FIG. 3B (c) shows the measured value Z (i) obtained in this way. The horizontal axis represents the time variable i, and the vertical axis represents the measured value V (i). The measured value Z (9) obtained by the correction is indicated by white circles, and the other measured values are indicated by black circles.

  The arithmetic processing unit applies a smoothing process and an interpolation process to the discretized measurement value Z (i) (i =... 0, 1, 2, 3,...), A display signal Z (t) is generated as a continuous signal. FIG. 3B (d) shows the display signal Z (t). The horizontal axis represents time t, and the vertical axis represents the value of the display signal Z (t).

  FIG. 4A (a) conceptually shows another example of the time waveform of the detection signal V (t). FIG. 4A (b) shows each detection value V (i) obtained for this detection signal V (t). In each detection value V (i) shown in FIG. 4A (b), since the peak formation condition is not satisfied, each detection value V (i) is directly used as each measurement value Z (i). FIG. 4B (c) shows a display signal Z (t) obtained for the detection value V (i) shown in FIG. 4A (b).

  According to the general nature of α rays, the α ray component included in the detection signal has a predetermined rise time and fall time, and a peak value in a predetermined range. Therefore, the detection value V (i) is the peak value of the α-ray component by appropriately setting the detection value extraction time T and the determination values D1 and D2 to determine whether the peak formation condition is satisfied. It is determined whether or not.

  When the peak formation condition is satisfied for the detected value V (i), the corrected value based on the two detected values before and after is set as the measured value Z (i), so that the measured value in which the α-ray component is reduced. Z (i) is determined. On the other hand, when the peak formation condition is not satisfied for the detected value V (i), the detected value V (i) is directly used as the measured value Z (i). In this case, even if the detection value has increased from the previous detection value, this increase is likely due to other radiation such as γ-rays or β-rays. The detected value is reflected in the measured value while being distinguished from the increase.

  FIG. 5 shows the configuration of the arithmetic processing unit 32. The calculation processing unit 32 includes a discretization unit 36, a calculation smoothing unit 38, an α-ray component reduction calculation unit 40, and a display smoothing unit 42. The arithmetic processing unit 32 is configured by a processor, for example. In this case, the arithmetic processing unit 32 constitutes a discretization unit 36, a calculation smoothing unit 38, an α-ray component reduction calculation unit 40, and a display smoothing unit 42 by executing a program read in advance. In the arithmetic processing unit 32, these components may be configured by individual hardware.

  The discretization unit 36 extracts and discretizes the value of the detection signal for each predetermined extraction time T, and outputs the discretization value continuous at intervals of the extraction time T on the time axis to the calculation smoothing unit 38. The extraction time T in the discretization unit 36 is determined according to the characteristics of the α-ray component. For example, the extraction time T is determined so that the peak waveform based on one detection event falls within twice the extraction time T.

  The arithmetic smoothing unit 38 performs a smoothing process on the discretized detection signal. An example of the smoothing process is a moving average process. In the moving average process, a predetermined number of discretized values retroactive from the reference time and an average value of the predetermined number of discretized values from the reference time to the future are used as the moving average value of the reference time. It is processing. For example, the discretization value of the reference time is X (j), the previous discretization value is X (j−1), the previous discretization value is X (j−2),. The discretized value before n is X (j−n), the discretized value after 1 is X (j + 1), the discretized value after 2 is X (j + 2),... When the later discretized value is X (j + n), the moving average value V (j) is expressed by the following (Equation 1).

  Here, n is an integer greater than or equal to 0 that defines the number of discretized values to be added and summed (2n + 1). By appropriately setting this value, the degree to which the past or future value is reflected in the moving average value is determined. Is set. When n is 0, the moving average value is a normal value. Further, low pass filter processing is executed by appropriately setting n. Note that each X (i) may be individually multiplied by a weighting coefficient to be added and summed to adjust the contribution of each X (i) to the moving average value V (j).

  The degree of smoothing in the arithmetic smoothing unit 38 is set so that the difference between the peak value of the detection value due to the α-ray component and the detection values before and after that is sufficiently large. If the degree of smoothing is too large, the difference between the peak value due to the α-ray component and the detected values before and after that may be reduced by excessive smoothing. On the other hand, when the degree of smoothing is too small, the detection values of radiation other than α rays are not sufficiently smoothed, so that it is difficult to distinguish between α ray components and noise.

  The calculation smoothing unit 38 outputs the discretized detection signal after the smoothing process to the α-ray component reduction calculation unit 40. The α-ray component reduction calculation unit 40 reduces the α-ray component included in the detection signal by the α-ray component reduction processing according to the flowchart of FIG.

  In FIG. 6, V (0), V (1), V (2), V (3),... Are sequentially output as detection values from the calculation smoothing unit 38 to the α-ray component reduction calculation unit 40. An example of processing when done is shown. The α-ray component reduction calculation unit 40 sets the initial value of the time variable i to 0, and increases the time variable i by 1 over time. The processes in steps S102 to S107 are executed for one i value.

  The α-ray component reduction calculating unit sets a value obtained by adding 1 to the initial value of i as a new i (S101). Then, the first difference V (1) −V (0) is obtained, and it is determined whether or not the first difference is equal to or greater than a predetermined first determination value D1 (S102). When the first difference V (1) −V (0) is less than the first determination value D1, the α-ray component reduction calculation unit sets the detected value V (1) as the measured value Z (1) (S105). .

  When the first difference V (1) −V (0) is greater than or equal to the first determination value D1, the α-ray component reduction calculating unit obtains the second difference V (1) −V (2) and obtains the second difference. Is greater than or equal to a predetermined second determination value D2 (S103). When the second difference V (1) −V (2) is less than the second determination value D2, the α-ray component reduction calculation unit sets the detected value V (1) as the measured value Z (1) (S105). .

  When the second difference V (1) −V (2) is equal to or greater than the second determination value D2, the α-ray component reduction calculation unit calculates the average value of the detection values V (2) and V (0) as the detection value V. The measured value Z (1) corresponding to (1) is used. That is, the measured value Z (1) is obtained as Z (1) = [V (2) + V (0)] / 2 (S104).

  The α-ray component reduction calculation unit outputs the measured value Z (1) obtained in step S104 or S105 (S106). The α-ray component reduction calculation unit determines whether or not a measurement stop command is input from the control unit 24 of FIG. 2 to the calculation processing unit 32 (S107), and ends the process when the measurement stop command is input. To do. This determination is not necessarily performed after step S106. That is, when the measurement stop command is input from the control unit 24 to the calculation processing unit 32, the α-ray component reduction calculation unit may end the process regardless of the calculation step of the flowchart. The α-ray component reduction calculating unit returns to the process of step S101 and increases the value of i by 1 (S101).

  Thereafter, the α-ray component reduction calculating unit similarly obtains the measured value Z (i). That is, the first difference V (i) −V (i−1) is obtained, and it is determined whether or not the first difference is greater than or equal to a predetermined first determination value D1 (S102). When the first difference V (i) −V (i−1) is less than the first determination value D1, the α-ray component reduction calculation unit obtains the measurement value Z (i) corresponding to the detection value V (i). The detected value V (i) is set (S105).

  When the first difference V (i) −V (i−1) is equal to or greater than the first determination value D1, the α-ray component reduction calculating unit obtains the second difference V (i) −V (i + 1), and It is determined whether or not the two differences are equal to or greater than a predetermined second determination value D2 (S103). When the second difference V (i) −V (i + 1) is less than the second determination value D2, the α-ray component reduction calculation unit obtains the measured value Z (i) corresponding to the detected value V (i) as the detected value. V (i) is set (S105).

  When the second difference V (i) −V (i + 1) is equal to or larger than the second determination value D2, the α-ray component reduction calculation unit detects an average value of the detection values V (i + 1) and V (i−1). The measured value Z (i) corresponding to the value V (i) is assumed. That is, Z (i) = [V (i + 1) + V (i−1)] / 2, and the measured value Z (i) is obtained (S104) and Z (i) is output (S106).

  In step S104, instead of using the average value of the detection values V (i + 1) and V (i-1) as the measurement value Z (i), the tendency of at least one of these detection values is reflected. Another value may be the measured value Z (i). For example, the weighted average value of the detection values V (i + 1) and V (i-1) may be used as the measurement value Z (i).

  As described above, the α-ray component reduction calculation unit includes the detection values V (i−1), V (i), and V (i + 1) (first detection value, second detection value, and third detection value) that are sequentially obtained with time. The detection value) is determined based on at least one of the detection values V (i−1) and V (i + 1) when the peak formation condition is satisfied, and a determination unit that determines whether the peak formation condition is satisfied. And a measurement value determination unit that sets the correction value as a radiation measurement value corresponding to the detection value V (i) when the peak formation condition is satisfied. When the peak formation condition is not satisfied, the measurement value determining unit sets a value based on the detection value V (i) as a radiation measurement value corresponding to the detection value V (i).

  According to the α-ray component reduction calculation unit, it is determined whether or not the detection value V (i) is a peak value with respect to the preceding and subsequent detection values V (i−1) and V (i + 1) (Step S102 and S103). That is, the increase in the detection value V (i) with respect to the detection value V (i−1) is not less than the determination value D1, and the decrease in the detection value V (i + 1) with respect to the detection value V (i) is not less than the determination value D2. It is determined whether or not a certain peak formation condition is satisfied.

  When this peak formation condition is not satisfied, the detected value V (i) is directly used as the measured value Z (i) corresponding to the time variable i. On the other hand, when the peak formation condition is satisfied, the average value of the detection values V (i + 1) and V (i−1) is obtained as a correction value, and this correction value is set as the measurement value Z (i).

  Returning to FIG. The α-ray component reduction calculating unit 40 measures the measured values Z (1), Z (2), Z (3),... corresponding to the detected values V (1), V (2), V (3),. Are obtained and output to the display smoothing unit 42. The display smoothing unit 42 is similar to the moving averaging process represented by (Equation 1) for the measurement values Z (1), Z (2), Z (3),. A moving average process is performed, and an interpolation process is performed to obtain a display signal, which is output to the display unit 18 in FIG. In this moving averaging process, the smoothing degree may be different from the moving averaging process for the detected values V (1), V (2), V (3),. Further, depending on the extraction time T, the interpolation process may not necessarily be executed. The display unit 18 displays the radiation measurement value represented by the display signal as a numerical value, a graph, a graphic, or the like.

  According to the α ray component reduction process, a radiation measurement value in which an error component based on α rays is suppressed is obtained by three detection values obtained in time series. After three detection values are obtained for the first time, a radiation measurement value in which an error component based on α rays is suppressed is obtained every time one detection value is newly obtained. As a result, the process of suppressing the error component based on the α ray is quickly performed.

  FIG. 7 conceptually shows examples of the detected value V (i) and the measured value Z (i) for i = 0 to 19. The horizontal axis represents the time represented by the time variable i, and the vertical axis represents the detected value V (i) and the measured value Z (i). In this example, the peak formation conditions are satisfied at i = 2, i = 6, and i = 18. That is, the condition that the first difference V (2) −V (1) is equal to or greater than the determination value D1 and the second difference V (2) −V (3) is equal to or greater than the determination value D2. Further, the condition that the first difference V (6) −V (5) is greater than or equal to the determination value D1 and the second difference V (6) −V (7) is greater than or equal to the determination value D2, and further The condition that the first difference V (18) −V (17) is greater than or equal to the determination value D1 and the second difference V (18) −V (19) is greater than or equal to the determination value D2 is satisfied. Therefore, Z (2), Z (6), and Z (18) can be obtained by using Z (i) = [V (i + 1) + V ( i-1)] / 2. For the other measured values Z (i), the detected value V (i) is directly used as the measured value Z (i) as shown by the black circles in FIG. As shown in FIG. 7, the measured values Z (2), Z (6) and Z (18) are reduced in value relative to the detected values V (2), V (6) and V (18). ing. On the other hand, the detection values V (10) to V (14) have relatively large values, but the peak formation conditions are not satisfied, and thus the values as they are are measured values Z (10) to Z (14). It is said that. As described above, according to the α-ray component reduction processing, the α-ray component is reduced from the measured value, and other radiation-based components can be reflected in the measured value.

  As described above, the difference between the peak value of the detection value due to the α-ray component and the detection values before and after that varies depending on the degree of smoothing of the detection signal. Further, if the determination values D1 and D2 in the α-ray component reduction processing are too small, it is possible to make an erroneous determination that the peak formation condition is satisfied even though the detection value becomes a peak value due to a factor other than the α-ray. Sex occurs. On the other hand, if the determination values D1 and D2 in the α-ray component reduction process are too large, there is a possibility of erroneous determination that the peak formation condition is not satisfied even though the peak formation condition is actually satisfied. Occurs. Therefore, the α-ray component reduction calculation unit 40 may set the determination values D1 and D2 according to the degree of smoothing in the calculation smoothing unit 38.

  When the process executed by the arithmetic smoothing unit 38 is a low-pass filter process, a numerical value representing the degree of smoothing includes a rising time constant in a step response. When a step signal whose value rises in steps from 0 to 1 at a certain time is input to the circuit, the signal output from the circuit reaches 1- (1 / e) times the convergence value. Is defined as the time until. e is the base of the natural logarithm. The greater the rise time constant, the greater the degree of smoothing.

  The arithmetic smoothing unit 38 may be configured such that the degree of smoothing is variable according to the control of the control unit 24 of FIG. In this case, smoothing information indicating the degree of smoothing may be given to the α-ray component reduction calculation unit 40. The smoothing information includes, for example, an integer n of 0 or more shown in (Equation 1). Further, when the process executed by the arithmetic smoothing unit 38 is a low-pass filter process, the smoothing information may be a rising time constant τ. The α-ray component reduction calculation unit 40 sets determination values D1 and D2 according to the smoothing information.

  In the above-described embodiment, the example in which the detection signal is smoothed after the discretization unit 36 has been described. However, the detection unit 30 in FIG. 2 may perform the smoothing process on the detection signal. . In this case, the detection unit 30 may include a smoothing circuit that performs a smoothing process. That is, the detection signal may be smoothed in at least one of the detection unit 30 and the calculation smoothing unit 38.

DESCRIPTION OF SYMBOLS 10 Radiation measuring instrument, 12 Ionization chamber, 14 Measurement part, 16 Front panel, 18 Display part, 20 Operation button, 22 Operation part, 24 Control part, 26 Collector electrode, 28 Electrode layer, 30 Detection part, 31 High voltage generation part, 32 arithmetic processing units, 36 discretization units, 38 calculation smoothing units, 40 α-ray component reduction calculation units, 42 display smoothing units.

Claims (4)

A detector for detecting radiation by an ionization chamber;
The first detection value, the second detection value, and the third detection value that are sequentially obtained from the detection unit as time elapses are peak formation conditions, and the second detection value is the first detection value and the third detection value. A determination unit that determines whether or not a peak formation condition that is a peak value for is satisfied,
A correction unit that determines a correction value based on at least one of the first detection value and the third detection value when the peak formation condition is satisfied;
And a measurement value determining unit that sets the correction value as a radiation measurement value corresponding to the second detection value when the peak formation condition is satisfied. The radiation measuring instrument according to claim 1,
The peak formation conditions are:
A first difference that is a difference between the second detection value and the first detection value is equal to or greater than a predetermined first determination value, and a second difference that is a difference between the second detection value and the third detection value is A radiation measuring instrument including a condition that a predetermined second determination value or more is included. The radiation measuring instrument according to claim 2,
A smoothing unit that performs a smoothing process on the detection value detected by the detection unit;
The determination unit
The radiation measuring instrument, wherein the first determination value and the second determination value are set according to a degree of smoothing by the smoothing unit. The radiation measuring instrument according to any one of claims 1 to 3,
The measurement value determining unit
When the peak formation condition is not satisfied, a value based on the second detection value is set as a radiation measurement value corresponding to the second detection value.

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