JP6258065B2 - Radiation measurement equipment - Google Patents

Description

  The present invention relates to a radiation measuring apparatus, and more particularly to an apparatus for separately measuring a plurality of types of radiation.

  Radiation measurement devices are used in facilities that handle radiation, such as hospitals and laboratories. For example, the radiation contained in the wastewater is measured and the wastewater is handled according to the radiation concentration. Some radiation measurement apparatuses use a scintillator and a photomultiplier tube. The scintillator generates light in response to detection of radiation. The photomultiplier tube outputs a pulsed signal according to the light generated by the scintillator. The radiation measuring device counts the signal output from the photomultiplier tube and obtains a radiation measurement value such as the number of decays based on a count value (count rate) per predetermined time. Examples of the scintillator include a solid scintillator in which the scintillator is placed as a solid solution in plastic or the like, and a liquid scintillator in which the scintillator is dissolved in a liquid.

  As a radiation measuring apparatus using a solid scintillator, Patent Document 1 describes a β-ray nuclide concentration measuring apparatus. In this apparatus, the measured peak value for each nuclide is determined from the measured spectrum. The true peak value is obtained by subtracting the mixed value between the nuclides from each measured peak value, and the measurement is performed for each nuclide based on the respective true peak value.

  Patent Document 2 describes a multi-nuclide fraction measurement method using a liquid scintillator. In this method, for each quenching level, a reference spectrum is obtained by spectrum measurement on a reference sample of each nuclide. Further, the sample spectrum is obtained by measuring the spectrum of the sample. Then, for each quenching level, a reference spectrum of each nuclide is synthesized, and when the residual between the synthesized spectrum and the sample spectrum is minimized, each nuclide from which the synthesized spectrum is obtained is obtained. Measurements for each nuclide are obtained based on the reference spectrum.

  Patent Document 3 describes a liquid scintillation system based on an external standard source channel ratio method (ESCR method) or the like. This system measures in advance a quenching index indicating the degree of quenching, and corrects the radiation count value using a correction coefficient corresponding to the quenching index. The correction coefficient is obtained based on a correction coefficient curve prepared in advance by measuring a set of standard samples.

JP-A-5-209965 Japanese Patent Laid-Open No. 6-265639 JP-A-7-306271

  When measuring a plurality of types of radiation using a radiation measurement apparatus, the radiation is measured in a wide energy range. Therefore, the radiation measuring apparatus is required to be able to measure in a wide energy range. On the other hand, a noise spectrum having a narrow energy width exists on the lower side of the energy spectrum of the radiation to be measured. Therefore, the radiation measuring apparatus is required to have a sufficient energy resolution for detecting a narrow band noise spectrum and suppressing the influence thereof.

  However, in the conventional radiation measuring apparatus, it may be difficult to measure radiation in a wide energy range while maintaining sufficient energy resolution. For this reason, the configuration and processing may be complicated, such as using a plurality of scintillators having different characteristics, or performing a plurality of measurements while switching the measurement energy range, energy resolution, and the like.

  An object of the present invention is to separate and measure a plurality of types of radiation with a simple configuration.

The present invention includes a detection unit that outputs a signal in response to detection of radiation, a plurality of analysis units that obtain radiation count rates for a plurality of different energy ranges based on the same detection signal output from the detection unit, A separation measurement unit that obtains a radiation measurement value for any one of a plurality of types of radiation based on a radiation count rate obtained by each of the plurality of analysis units, and the plurality of analysis units include a first analysis. A second analysis unit having a lower limit of an energy range for obtaining a radiation count rate equal to that of the first analysis unit and an upper limit of an energy range for obtaining a radiation count rate being greater than that of the first analysis unit, The energy resolution for the radiation count rate required by one analysis unit is higher than the energy resolution for the radiation count rate required by the second analysis unit. At least one of the second analysis units includes a level adjustment unit that adjusts the level of the detection signal in accordance with the energy resolution of the calculated radiation count rate, and the separation measurement unit is obtained by the first analysis unit. A contamination value that is included in the radiation count rate and that is not included in the measurement target and that is obtained based on the radiation count rate that the second analysis unit obtains, and a radiation count rate that the first analysis unit obtains Based on this, a radiation measurement value is obtained for the radiation to be measured .

In the present invention, a plurality of analysis units obtain radiation count rates for a plurality of different energy ranges based on the same detection signal. Accordingly, it is not always necessary to use a plurality of detection units, and radiation measurement can be quickly performed with respect to a plurality of energy ranges with a simple configuration. In the present invention, at least one of the first analysis unit and the second analysis unit further includes a level adjustment unit that adjusts the level of the detection signal in accordance with the energy resolution. As a result, the scales of the radiation count rates required in the first analysis unit and the second analysis unit are aligned, and the process executed by the separation measurement unit is simplified.

The plurality of analysis units in the present invention include a first analysis unit and a second analysis unit having different energy ranges in which a radiation count rate is required and energy resolution. Second assay, the lower limit of the energy range for obtaining the radiation count rate equal to the first analyzer, the upper limit is greater than the first mass analyzer. The first analysis unit has a higher energy resolution than the second analysis unit. As a result, it is possible to suppress the influence of a narrow band noise spectrum in a low energy region and perform measurement in a wide energy range.

Preferably, each of the plurality of analysis unit, obtain Preparations multichannel analyzer for determining the spectrum of the radiation counting rate in the energy range corresponding to itself.

  Preferably, each of the plurality of analysis units includes a discrimination unit that discriminates the detection signal into one or a plurality of energy ranges, and one energy range based on the detection signals discriminated into one energy range. And a counting unit for obtaining the radiation count rate.

  According to such a configuration, the configuration is simpler than using a general multi-channel analyzer.

  Preferably, the detection unit includes a liquid scintillator that emits light according to the detected radiation, and a photomultiplier tube that outputs a detection signal according to the light emitted from the liquid scintillator. The unit obtains a radiation measurement value for β rays based on the degree of quenching in the liquid scintillator.

  According to the present invention, a plurality of types of radiation can be separated and measured with a simple configuration.

It is a figure which shows the structure of a radiation measuring device. It is a figure which illustrates the rough form of the wide spectrum calculated | required by 2nd MCA. It is a figure which illustrates the outline of the narrow range spectrum calculated | required by 1st MCA. It is a figure which shows the energy spectrum of each nuclide. It is a flowchart which shows the process which a isolation | separation measurement part performs. It is a figure which shows the structure of the radiation measuring device which concerns on a modification.

FIG. 1 shows a configuration of a radiation measuring apparatus according to an embodiment of the present invention. The radiation measuring apparatus converts light emitted from the liquid scintillator 10 into a pulse signal in response to detection of radiation, and measures radiation based on a count value (counting rate) per predetermined time of the pulse signal. The counting rate is measured as an energy spectrum, and based on an analysis process for the energy spectrum, radiation from a plurality of nuclides is separated and measured. The nuclide to be measured is, for example, tritium ( ³ H), carbon 14 ( ¹⁴ C), phosphorus 32 ( ³² P), strontium 90 ( ⁹⁰ Sr), etc., and β-rays radiated therefrom are measured. .

  The photomultiplier tube 12-1 and the photomultiplier tube 12-2 are arranged at positions where the liquid scintillator 10 is sandwiched. The liquid scintillator 10 and each photomultiplier tube constitute a detection unit that outputs a pulse signal as a detection signal in response to detection of radiation.

  When light is emitted from the liquid scintillator 10, each photomultiplier tube outputs a pulse signal from the terminal TT and the terminal TE. The pulse signal output from the terminal TT is a pulse signal for timing detection. The pulse signal output from the terminal TE is a pulse signal for measuring the peak value.

  A pulse signal is output from the terminal TT of the photomultiplier tube 12-1 to the waveform shaping amplifier 14-1. The waveform shaping amplifier 14-1 shapes the waveform of the pulse signal and outputs it to the AND circuit 15. A pulse signal is output from the terminal TT of the photomultiplier tube 12-2 to the waveform shaping amplifier 14-2. The waveform shaping amplifier 14-2 shapes the waveform of the pulse signal and outputs it to the AND circuit 15. The AND circuit 15 outputs a pulse timing signal corresponding to the logical product of the two pulse signals output from the waveform shaping amplifiers 14-1 and 14-2 to the first multi-channel analyzer 22 and the second multi-channel analyzer 24. . Each multi-channel analyzer counts an energy analysis pulse signal, which will be described later, according to the timing indicated by the pulse timing signal. In the following description, the first multi-channel analyzer 22 and the second multi-channel analyzer 24 are referred to as a first MCA 22 (Multi Channel Analyzer) and a second MCA 24, respectively.

  A pulse signal is output from the terminal TE of the photomultiplier tube 12-1 to the buffer amplifier 16-1. The buffer amplifier 16-1 outputs the pulse signal to the addition buffer amplifier 18 while maintaining the characteristics related to the peak value of the pulse signal. A pulse signal is output from the terminal TE of the photomultiplier tube 12-2 to the buffer amplifier 16-2. The buffer amplifier 16-2 outputs the pulse signal to the addition buffer amplifier 18 while maintaining the characteristics related to the peak value of the pulse signal. The addition buffer amplifier 18 outputs an energy analysis pulse signal obtained by adding the pulse signals to the level adjustment amplifier 20 and the second MCA 24.

  The level adjustment amplifier 20 multiplies the energy analysis pulse signal by an adjustment gain G and outputs the result to the first MCA 22. Here, the adjustment gain G is determined based on how many times the energy resolution of the first MCA 22 is set to the energy resolution of the second MCA 24.

  When radiation is continuously detected one after another in the liquid scintillator 10, energy analysis pulse signals are sequentially input to the first MCA 22 and the second MCA 24. The first MCA 22 obtains an energy spectrum based on energy analysis pulse signals that are successively input. That is, the energy analysis pulse signal is discriminated into one of a plurality of energy channels based on the peak value, and the count rate is obtained for each channel. At this time, the first MCA 22 counts each energy analysis pulse signal according to the timing indicated by the pulse timing signal output from the AND circuit 15. The first MCA 22 outputs energy spectrum data to the separation measurement unit 26. The horizontal axis of the energy spectrum thus obtained is energy determined by the peak value, and the vertical axis is the count rate in each energy channel.

  The second MCA 24 obtains an energy spectrum based on the energy analysis pulse signals that are successively input by the same process as the process executed by the first MCA 22. The second MCA 24 outputs energy spectrum data to the separation measurement unit 26.

  When the first MCA 22 and the second MCA 24 count the energy analysis pulse signal according to the pulse timing signal, the frequency of counting noise is reduced, and the noise included in the energy spectrum is suppressed.

  As described above, the level adjustment amplifier 20 and the first MCA 22 constitute a liquid scintillator 10 as a detection unit and a first analysis unit that obtains an energy spectrum (radiation efficiency) based on detection signals from each photomultiplier tube. The second MCA 24 constitutes a second analysis unit that obtains an energy spectrum based on the detection signal.

  Here, it is assumed that the energy resolution of the first MCA 22 is higher than the energy resolution of the second MCA 24 and is an adjustment gain G times. Further, the lower limit of the energy range of each energy spectrum obtained by the first MCA 22 and the second MCA 24 is assumed to be 0 and the same. The upper limit of the energy range of the energy spectrum obtained by the second MCA 24 is larger than that of the energy spectrum obtained by the first MCA 22 and is an adjustment gain G times. That is, the second MCA 24 obtains an energy spectrum in a wider energy range than the first MCA 22. For example, the upper limit of the energy range of the energy spectrum required by the second MCA 24 is 10 times, 100 times the upper limit of the energy range of the energy spectrum required by the first MCA 22.

  Therefore, in the following description, the energy spectrum obtained by the first MCA 22 is referred to as a narrow spectrum, and the energy spectrum obtained by the second MCA 24 is referred to as a wide spectrum.

  FIG. 2 illustrates an outline of the wide spectrum required by the second MCA 24. The energy range of the wide spectrum is 0 or more and E3 or less. This wide spectrum is due to radiation emitted from three nuclides. Since the energy spectra of the three nuclides are combined, the curvature of the curve representing the energy spectrum is not uniform.

  FIG. 3 illustrates an outline of a narrow-range spectrum obtained by the first MCA 22. The energy range of the narrow spectrum is 0 or more and E2 or less. This narrow-range spectrum is obtained by cutting out a portion of 0 or more and E2 or less from the energy range of a wide-range spectrum and setting the energy resolution to an adjustment gain G times. For the radiation on the higher frequency side than the energy E2, the measured value is removed by the first MCA 22.

  In the radiation measurement environment, there is a noise spectrum with a narrow energy width in the vicinity of energy 0 on the lower frequency side than the narrow range spectrum shown in FIG. The first MCA 22 has a function of suppressing such a narrow band noise spectrum by pulse height discrimination with sufficient energy resolution.

  In FIG. 4, the outline of each energy spectrum of the nuclide A, the nuclide B, and the nuclide C is illustrated. The energy spectrum 32A drawn with a broken line is due to the nuclide A. The energy spectrum 32B drawn by a solid line is due to the nuclide B, and the energy spectrum 32C drawn by a one-dot chain line is due to the nuclide C. The energy spectrum 32C of the nuclide C overlaps with each energy spectrum (32A, 32B) of the nuclide A and the nuclide B on the low frequency side. The energy spectrum 32B of the nuclide B overlaps the energy spectrum 32A of the nuclide A on the low frequency side. The wide spectrum shown in FIG. 3 corresponds to the sum of the energy spectra of nuclide A, nuclide B, and nuclide C.

For example, nuclide A, nuclide B, and nuclide C are tritium ( ³ H), carbon 14 ( ¹⁴ C), and phosphorus 32 ( ³² P), respectively. It should be noted that the energy spectrum shown in FIGS. 2 to 4 is a rough outline for explanation, and is strictly different from that actually measured.

  Next, a process in which the separation measurement unit 26 in FIG. 1 calculates the number of decays as the radiation measurement value for the nuclide A, the nuclide B, and the nuclide C will be described. In this process, the energy range to be measured is divided into a plurality of windows corresponding to each nuclide, the count rate is obtained for each window in order from the high frequency side window, and the decay number of each nuclide is obtained based on each count rate. It is. When the energy spectrum of the nuclide that is not the measurement target is mixed in one window, the contribution of the energy spectrum of the nuclide that is not the measurement target is excluded using the data measured in advance. Hereinafter, such multi-window processing will be specifically described.

  First, as shown in FIG. 4, a first window W1, a second window W2, and a third window W3 are set as energy ranges for which a counting rate is required for an energy range to be measured. . That is, the first window W1 is set in an energy range of energy 0 or more and less than E1. Then, the second window W2 is set in the energy range of energy E1 or more and less than E2, and the third window W3 is set in the energy range of energy E2 or more and E3 or less. This setting is performed in advance by a user operation.

  The third window W3 is set in a region overlapping with the energy spectrum of the nuclide C at a higher frequency than each energy spectrum of the nuclide A and nuclide B. The second window W2 is set in a region where the energy spectra of the nuclide B and the nuclide C are mixed in a lower region than the third window W3 and higher than the energy spectrum of the nuclide A. The first window W1 is set to a region where the energy spectrum of the nuclide A, the nuclide B, and the nuclide C is mixed, which is lower than the second window W2.

  In the separation measurement unit 26, processing for the first window W1 and the second window W2 is performed using a narrow spectrum, and processing for the third window W3 is performed using a wide spectrum.

  Here, a case where two adjacent windows are in contact with each other is taken up, but they may be separated from each other. That is, an area that does not belong to any window may be interposed between adjacent windows.

  In order to execute the multi-window process, the following data is stored in the storage unit 28 in advance. These data are obtained in advance by actual measurement under the premise that the first window W1, the second window W2, and the third window W3 are set.

  The storage unit 28 stores an ESCR value for the liquid scintillator 10 containing the sample or an ESCR value equivalent to the ESCR value. The ESCR value is an index value indicating the degree of quenching, and is obtained by an external standard channel ratio method (ESCR method) as described in Patent Document 3. Quenching means that the luminous efficiency of the scintillator is reduced due to the inclusion of the sample, or the emitted light is attenuated, so that the radiation counting efficiency is lowered. The energy spectrum of each nuclide changes depending on the degree of queuing. On the other hand, when the degree of quenching is determined, the energy spectrum of each nuclide is also determined. Therefore, by knowing the degree of quenching, the ratio of the counting efficiency to each window can be obtained for each nuclide.

  The storage unit 28 stores a nuclide C mixing ratio d database in which ESCR values and nuclide C mixing ratios d are associated with each other. Here, when the count rate for the nuclide C in the third window W3 is N, the count rate based on the nuclide C is mixed into the count rate in the second window W2 by N / d. It is a value indicating that. According to the nuclide C mixing ratio d database, the nuclide C mixing ratio d corresponding to the ESCR value is obtained.

  The storage unit 28 stores a nuclide C mixture ratio e database in which the ESCR values and the nuclide C mixture ratio e are associated with each other. Here, when the count rate for the nuclide C in the third window W3 is N, the count rate based on the nuclide C is mixed into the count rate in the first window W1 by N / e. It is a value indicating that. According to the nuclide C mixing ratio e database, the nuclide C mixing ratio e corresponding to the ESCR value is obtained.

  The storage unit 28 stores a nuclide B mixture ratio f database in which the ESCR values and the nuclide B mixture ratio f are associated with each other. Here, when the count rate for the nuclide B in the second window W2 is N, the count rate based on the nuclide B is mixed into the count rate in the first window W1 by N / f. It is a value indicating that. According to the nuclide B contamination ratio f database, the nuclide B contamination ratio f corresponding to the ESCR value is obtained.

  In the storage unit 28, the counting efficiency η1 for the nuclide A in the first window W1, the counting efficiency η2 for the nuclide B in the second window W2, and the counting efficiency η3 for the nuclide C in the third window W3 are set as ESCR values. A counting efficiency database associated with each other is stored. The counting efficiency represents the ratio of the counting rate measured in one window with respect to the number of decays of a certain nuclide, and depends on the degree of quenching. That is, by dividing the count rate actually measured for one nuclide in one window by the counting efficiency, the number of decays for that nuclide can be obtained.

  FIG. 5 shows a flowchart in which the separation measurement unit 26 obtains the decay number ξ (A) of the nuclide A, the decay number ξ (B) of the nuclide B, and the decay number ξ (C) of the nuclide C, respectively. . The separation measurement unit 26 executes the program stored in the storage unit 28 and executes processing according to this flowchart. That is, the separation measurement unit 26 performs multi-window processing based on the wide spectrum, the narrow spectrum, and the above data stored in the storage unit 28.

  The separation measurement unit 26 obtains the count rate N3 in the third window W3 based on the wide spectrum data output from the second MCA 24 (S101). That is, the separation measurement unit 26 obtains the sum total of the count rates obtained for each channel belonging to the third window W3 as the count rate N3. The separation measuring unit 26 refers to the counting efficiency database in the storage unit 28, reads the counting efficiency η3 corresponding to the ESCR value (S102), and obtains the decay number of the nuclide C based on the following (Equation 1) (S103). .

  (Expression 1) ξ (C) = N3 / η3

  The separation measurement unit 26 obtains the count rate N2 in the second window W2 based on the narrow-range spectrum data output from the first MCA 22 (S104). That is, the separation measuring unit 26 obtains the sum total of the count rates obtained for each channel belonging to the second window W2 as the count rate N2. Further, the separation measurement unit 26 refers to the nuclide C mixing ratio d database in the storage unit 28 and reads the nuclide C mixing ratio d corresponding to the ESCR value (S105). Further, the separation measurement unit 26 refers to the counting efficiency database, reads the counting efficiency η2 corresponding to the ESCR value (S106), and obtains the decay number of the nuclide B based on the following (Expression 2) (S107).

  (Expression 2) ξ (B) = (N2−N3 / d) / η2

  Here, N3 / d is a count rate for the nuclide C included in the count rate N2 for the second window W2. (N2-N3 / d) is obtained by subtracting the count rate (mixed value) for nuclide C from the count rate N2, and is the count rate for nuclide B. By dividing this counting rate by the counting efficiency η2, the number of decays of nuclide B can be obtained.

  That is, as shown in (Equation 2), the separation measurement unit 26 includes the mixed value (N3 / d) based on the energy spectrum of the non-measurement nuclide C mixed in the second window W2, and the second window W2. The decay number ξ (B) for the nuclide B is obtained based on the count rate N2 and the count efficiency η2.

  The separation measurement unit 26 obtains the count rate N1 in the first window W1 based on the narrow-range spectrum data output from the first MCA 22 (S108). That is, the separation measuring unit 26 obtains the sum total of the count rates obtained for each channel belonging to the first window W1 as the count rate N1. Further, the separation measuring unit 26 refers to the nuclide C mixing ratio e database in the storage unit 28 and reads the nuclide C mixing ratio e corresponding to the ESCR value (S109). In addition, the separation measurement unit 26 refers to the nuclide B contamination ratio f database in the storage unit 28 and reads the nuclide B contamination ratio f corresponding to the ESCR value (S110). Further, the separation measurement unit 26 refers to the counting efficiency database, reads the counting efficiency η1 corresponding to the ESCR value (S111), and obtains the decay number of the nuclide A based on the following (Equation 3) (S111).

  (Expression 3) ξ (A) = [N 1 −N 3 / e− (N 2 −N 3 / d) / f] / η 1

  Here, N3 / e is a count rate for nuclide C included in the count rate N1. (N2-N3 / d) / f is a count rate for nuclide B included in the count rate N1. [N1-N3 / e- (N2-N3 / d) / f] is obtained by subtracting each count rate (mixed value) for nuclide B and nuclide C from the count rate N1 for the first window W1. , The counting rate for nuclide A. By dividing this counting rate by the counting efficiency η1, the number of decays of nuclide A can be obtained.

  That is, as expressed in (Equation 3), the separation measurement unit 26 determines that the mixed value (N3 / e) of the nuclide C outside the measurement target mixed in the first window W1 is not measured. The decay number ξ (A) for the nuclide A is determined based on the mixed value (N2−N3 / d) / f of the nuclide B energy spectrum, the count rate N1 in the first window W1, and the count efficiency η1.

  The separation measurement unit 26 converts each decay number obtained for the nuclide A, the nuclide B, and the nuclide C into a predetermined unit such as becquerel and outputs it to a monitor 30 as a display unit. The monitor 30 displays the number of decays for each nuclide.

  The calculation order and the data reading order in steps S101 to S111 are just an example. The separation measurement unit 26 may obtain the decay number for each nuclide based on (Equation 1) to (Equation 3) in other calculation orders and data reading orders. For example, the count rates N1 to N3 are obtained first, and the nuclide C mixture ratio d, the nuclide C mixture ratio e, the nuclide B mixture ratio f, and the count efficiencies η1 to η3 are read from the storage unit 28, ) To (Equation 3) may be calculated.

  Further, the separation measurement unit 26 may display a narrow-range spectrum or a wide-range spectrum on the monitor 30, and the user may set each window based on the displayed spectrum. Further, here, an example in which an ESCR value is used as an index value indicating the degree of quenching has been described. As such an index value, an index value obtained by another method such as an external standard method (ESR method) or a sample channel ratio method (SCR method) may be used.

  Generally, when a plurality of types of radiation are measured by a radiation measuring apparatus, the radiation is measured in a wide energy range. Therefore, the radiation measuring apparatus is required to be able to measure in a wide energy range. On the other hand, there is a noise spectrum with a narrow energy width on the lower side of the energy spectrum of the radiation to be measured. Therefore, the radiation measuring apparatus is required to have a sufficient energy resolution for detecting a narrow band noise spectrum and suppressing the influence thereof.

  The energy resolution of the first MCA 22 used in the present embodiment is higher than the energy resolution of the second MCA 24. Further, the upper limit of the energy range of the wide spectrum obtained by the second MCA 24 is larger than that of the narrow spectrum obtained by the first MCA 22. The first MCA 22 having the higher energy resolution suppresses the influence on the measurement by the narrow band noise spectrum in the low energy region. As a result, the influence of the noise spectrum can be suppressed and measurement can be performed in a wide energy range.

  In the radiation measurement apparatus according to the present embodiment, energy spectra having different energy ranges are obtained for the common energy analysis pulse signal using two multi-channel analyzers. As a result, radiation measurement can be quickly performed for a plurality of energy ranges with a simple configuration.

  FIG. 6 shows a configuration of a radiation measuring apparatus according to a modification. This radiation measurement apparatus is the same as the radiation measurement apparatus shown in FIG. 1 except that the first MCA 22 is replaced with a first wave height discrimination counting unit 34 and the second MCA 24 is replaced with a second wave height discrimination counting unit 36. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The first wave height discrimination counting unit 34 includes a first wave height discrimination unit 38, a first counting unit 40, a second wave height discrimination unit 42, and a second counting unit 44. The first wave height discriminating unit 38 discriminates among the pulse signals for energy analysis inputted one after another within the energy range of the first window W1 according to the crest value, and outputs it to the first counting unit 40. The first counting unit 40 counts the energy analysis pulse signal discriminated by the first wave height discriminating unit 38 and outputs the count rate N1 to the separation measuring unit 26.

  The second wave height discriminating unit 42 discriminates among the pulse signals for energy analysis that are successively input within the energy range of the second window W <b> 2 according to the peak value, and outputs the discriminated signal to the second counting unit 44. The second counting unit 44 counts the energy analysis pulse signal discriminated by the second wave height discriminating unit 42 and outputs the count rate N2 to the separation measuring unit 26.

  The second wave height discrimination counting unit 36 includes a third wave height discrimination unit 46 and a third counting unit 48. The third wave height discriminating unit 46 discriminates among the pulse signals for energy analysis inputted one after another within the energy range of the third window W3 according to the crest value, and outputs it to the third counting unit 48. The third counting unit 48 counts the energy analysis pulse signal discriminated by the third wave height discriminating unit 46 and outputs the count rate N3 to the separation measuring unit 26.

  The separation measuring unit 26 uses the count rates N1 and N2 output from the first wave height discrimination counting unit 34 and the count rate N3 output from the second wave height discrimination counting unit 36 according to the above-described multi-channel processing and For A, nuclide B and nuclide C, the decay number ξ (A), decay number ξ (B) and decay number ξ (C) are determined.

  According to such a configuration, since the peak height discrimination and counting are performed only for the necessary windows, the configuration is simpler than when a multi-channel analyzer is used.

  DESCRIPTION OF SYMBOLS 10 Liquid scintillator, 12-1, 12-2 Photomultiplier tube, 14-1, 14-2 Waveform shaping amplifier, 15 AND circuit, 16-1, 16-2 Buffer amplifier, 18 addition buffer amplifier, 20 level adjustment amplifier , 22 First multi-channel analyzer (first MCA), 24 Second multi-channel analyzer (second MCA), 26 Separation measurement unit, 28 Storage unit, 30 Monitor, 32A, 32B, 32C Energy spectrum, 34 First wave height discrimination counting unit , 36 2nd wave height discrimination counting part, 38 1st wave height discrimination part, 40 1st counting part, 42 2nd wave height discrimination part, 44 2nd counting part, 46 3rd wave height discrimination part, 48 3rd counting part.

Claims (4)

A detector that outputs a signal in response to detection of radiation;
Based on the same detection signal output from the detection unit, a plurality of analysis units for obtaining a radiation count rate for a plurality of different energy ranges;
Based on the radiation count rate obtained by each of the plurality of analysis units, a separation measurement unit for obtaining a radiation measurement value for any of a plurality of types of radiation, and
Equipped with a,
The plurality of analysis units include:
A first analysis unit;
A lower limit of an energy range for obtaining a radiation count rate is equal to the first analysis unit, and an upper limit of an energy range for obtaining a radiation count rate is greater than the first analysis unit, and a second analysis unit,
The energy resolution for the radiation count rate required by the first analyzer is higher than the energy resolution for the radiation count rate required by the second analyzer,
At least one of the first analysis unit and the second analysis unit includes a level adjustment unit that adjusts the level of the detection signal according to an energy resolution for a required radiation count rate,
The separation measuring unit is
The mixed value of radiation that is not measured and included in the radiation count rate obtained by the first analysis unit, the contamination value obtained based on the radiation count rate obtained by the second analysis unit, and the first analysis unit A radiation measurement apparatus that obtains a radiation measurement value for the radiation to be measured based on the radiation count rate that is required . The radiation measurement apparatus according to claim 1 ,
The plurality of each analysis portion, the radiation measuring apparatus characterized by obtaining Bei multichannel analyzer for determining the spectrum of the radiation counting rate in the energy range corresponding to itself. The radiation measurement apparatus according to claim 1 or 2,
Each of the plurality of analysis units is
A discriminator for discriminating the detection signal into one or more energy ranges;
Based on the detection signal discriminated into one energy range, a counting unit for obtaining the radiation count rate for the one energy range;
A radiation measurement apparatus comprising: In the radiation measuring device according to any one of claims 1 to 3 ,
The detector is
A liquid scintillator that emits light in response to the detected radiation;
A photomultiplier tube that outputs the detection signal in response to light emitted from the liquid scintillator,
The separation measurement unit obtains a radiation measurement value for β rays based on a degree of quenching in the liquid scintillator.

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