JP2011196961A - Method and apparatus for measuring radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for measuring radiation which can precisely perform simultaneous counting of cascade γ rays having different amounts of energy.SOLUTION: Γ-ray detection signals output from a radiation detector 1A, which detects the cascade γ rays, are input into a pulse height discriminator 5A and a delay circuit 6A. The pulse height discriminator 5A removes the γ-ray detection signals having larger amounts of energy than a setting energy and outputs the γ-ray detection signals having equal or smaller amounts of energy than the setting energy (for example, detection signals of cascade γ rays) to a linear gate 7A. The linear gate 7A outputs the γ-ray detection signals from the delay circuit 6A to a summing amplifier 8 when the γ-ray detection signals is input from the pulse height discriminator 5A. The γ-ray detection signals output from the radiation detector 1B are processed similarly by the pulse height discriminator 5B and the linear gate 7B, and input into the summing amplifier 8. A multichannel wave height analyzer 10 performs the simultaneous counting of the cascade γ rays with the output of the summing amplifier 8.

Description

  The present invention relates to a radiation measurement method and a radiation measurement apparatus, and more particularly to a radiation measurement method and a radiation measurement apparatus suitable for measuring cascade γ rays emitted from a radionuclide to be measured.

  During operation of a nuclear power plant, the radiation dose rate in the reactor containment vessel is very high compared to the periodic inspection of the plant, so the reactor primary piping (for example, the recirculation piping connected to the reactor pressure vessel) On the other hand, measurement with a portable survey meter used for periodic inspection is not performed. In addition, during operation of a nuclear power plant, radiation measurement of the reactor primary system piping using a general radiation monitor other than a portable survey meter is not performed.

  When a nuclear radiation measurement is performed on the reactor primary system piping using a general radiation monitor including a portable survey meter during the operation of the nuclear power plant, the measurement target nuclide is the inner surface of the reactor primary system piping. Co-60, Co-58, Mn-54, Fe-59, etc. adhering to the surface. During operation of the nuclear power plant, there are background γ rays due to disturbing radionuclides (N-13, N-16, F-18, O-19, etc.) contained in the cooling water flowing in the reactor primary system piping. For this reason, it is difficult to measure the measurement target nuclide with the radiation monitor provided in the reactor primary system piping. In order to minimize the influence of background γ-rays, it is conceivable to apply a simultaneous counting method of cascade γ-rays emitted from the measurement target nuclide.

JP-A-8-101275 and JP-A-11-194170 propose a radiation monitoring system to which a radiation counting method is applied. The radiation monitor system disclosed in Japanese Patent Application Laid-Open No. HEI 8-101275 discloses a measurement target placed between a main detector and a gate detector to detect cascaded γ rays emitted from the measurement target. Each is detected with a vessel. When a radiation detection signal is output from the gate detector, the radiation detection signal output from the main detector is input to the counter because the non-coincidence circuit blocks the radiation detection signal output from the main detector. Not. The counter counts the radiation detection signal from the main detector input to the non-simultaneous counting circuit when the radiation detection signal is not output from the gate detector. As a result, γ rays generated by β ⁺ decay (annihilation γ rays radiated from disturbing radionuclides such as N-13) are not counted, and only the radiation detection signals to be measured output from the main detector are counted. be able to.

  JP-A-8-101275 discloses a radioactive substance inspection apparatus that performs simultaneous determination on each radiation detection signal output from two radiation detectors and performs signal processing on the radiation detection signal determined to be simultaneous. Is described.

JP-A-8-101275 Japanese Patent Laid-Open No. 11-194170

  As will be described later, the inventors have newly announced that when cascade gamma rays having a plurality of energies are simultaneously emitted from the measurement target nuclide, it may be difficult to simultaneously count the cascade gamma rays. I found it. In order to support simultaneous counting of cascaded gamma rays with multiple energies, the output level area of each wave height discriminator connected to each radiation detector that detects cascaded gamma rays with multiple energies is expanded and detected. It is necessary to cope with a radiation detection signal having the energy of the cascaded γ-rays. However, if the output level region of the wave height discriminator is expanded, an accidental coincidence may occur and the measurement accuracy may deteriorate. In particular, when the influence of interfering radionuclides is strong, that is, when the dose rate of background γ-rays is higher than the cascade γ-rays of the measurement target nuclides, measurement is difficult even using the conventional coincidence method.

  Each radiation monitor system to which the coincidence counting method described in Japanese Patent Application Laid-Open Nos. 8-101275 and 11-194170 is applied corresponds to the case where the energy of cascade γ-rays simultaneously emitted from the measurement target nuclides is different. Has not been made.

  An object of the present invention is to provide a radiation measurement method and a radiation measurement apparatus capable of improving the accuracy of coincidence counting of cascade γ rays having different energies.

A feature of the present invention that achieves the above-described object is that the first and second radiation detectors detect cascade γ-rays radiated from the measurement target nuclide having different energies, respectively.
It is smaller than the total energy of each cascade gamma ray radiated from the measurement target nuclide, and larger than the largest energy of those cascade gamma rays emitted from the measurement target nuclide. Adding a first γ-ray detection signal having an energy equal to or lower than the first set energy set in the energy range and a second γ-ray detection signal having an energy equal to or lower than the first set energy to generate an addition signal;
It is to count the sum signal having the total energy of cascade γ rays in which the energy radiated from the measurement target nuclide is different.

  A first γ-ray detection signal output from the first radiation detector having energy equal to or lower than the first set energy, and a second γ-ray detection signal output from the second radiation detector having energy equal to or lower than the first set energy. Is added to generate the addition signal, so that it is possible to suppress the coincidence coincidence due to the influence of γ rays having energy larger than the first set energy. Therefore, it is possible to improve the accuracy of coincidence of cascade γ-rays with different energies radiated from measurement target nuclides existing in an environment where γ-rays having energy larger than the first set energy are emitted.

Preferably, the first γ-ray detection signal output from the first radiation detector is input to the first gate signal generator and the first delay device, respectively, and the first γ-ray detection signal input by the first gate signal generator. The first gate opening signal is not output when the energy of the first γ-ray detection signal is equal to or lower than the first setting energy, and the first gate opening signal is not output. The time required for the first delay device to output the first γ-ray detection signal input and the first gate signal generator to output the first gate open signal after the first γ-ray detection signal is input. When the first gate device receives the first gate open signal from the first gate signal generator, the first gamma ray detection signal input from the first delay device is sent to the adder. The force,
The second γ-ray detection signal output from the second radiation detector is input to the second gate signal generator and the second delay device, respectively, and the energy of the input second γ-ray detection signal is input by the second gate signal generator. When the energy is larger than the first set energy, the second gate open signal is not output, and when the energy of the input second γ-ray detection signal is lower than the first set energy, the second gate open signal is output. Then, the second delay device delays the input second γ-ray detection signal by a time required for the second gate signal generator to input the second γ-ray detection signal and output the second gate open signal. When the second gate device receives the second gate open signal from the second gate signal generator, the second gamma ray detection signal input from the second delay device is output to the adder,
It is desirable that the addition signal is generated by an addition device that receives the first γ-ray detection signal output from the first gate device and the second γ-ray detection signal output from the second gate device.

  When the first gate device receives the first gate open signal from the first gate signal generator, the first gate device outputs the first γ-ray detection signal input from the first delay device to the adder, and the second gate device When the second gate open signal is input from the two-gate signal generator, the second γ-ray detection signal input from the second delay device is output to the adder. The first γ-ray detection signal, which is the output of the first radiation detector that has detected the cascade γ-rays, and the second radiation detector that has detected other cascade γ-rays having substantially different energy output from the measurement target nuclide. The second γ-ray detection signal, which is the output of, can be input to the adder at substantially the same time. Thereby, the structure which gives time information to the 1st and 2nd gamma ray detection signal is unnecessary, and it is possible to perform simultaneous counting of cascade gamma rays with different energy radiated from the measurement target nuclide with a simple structure. Furthermore, as described above, it is possible to improve the accuracy of coincidence counting of cascade γ rays with different energies radiated from the measurement target nuclide.

In addition, cascade γ-rays with different energies emitted from the measurement target nuclide are detected by the first radiation detector and the second radiation detector, respectively.
When the third radiation detector detects γ-rays that are Compton scattered in the first radiation detector, a third γ-ray detection signal is output, and the fourth radiation detector γ-rays that are Compton scattered in the second radiation detector. Output a fourth γ-ray detection signal when
When the third radiation detector does not output the third γ-ray detection signal and the fourth radiation detector does not output the fourth γ-ray detection signal, the cascaded γ-rays radiated from the measurement target nuclide are counted. A first γ-ray detection signal having energy lower than a first set energy set in a range of energy smaller than the total energy and larger than the largest energy among the energy of cascade γ-rays radiated from the measurement target nuclide; Adding a second γ-ray detection signal having energy equal to or lower than the first set energy to generate an addition signal;
The object of the present invention can also be achieved by counting the sum signal having the total energy of the cascade γ-rays with different energies radiated from the measurement target nuclide.

  When the third radiation detector detects γ-rays that are Compton scattered in the first radiation detector, a third γ-ray detection signal is output, and the fourth radiation detector γ-rays that are Compton scattered in the second radiation detector. Is output when the third radiation detector does not output the third γ-ray detection signal and the fourth radiation detector does not output the fourth γ-ray detection signal. Since the first γ-ray detection signal having the energy lower than the energy and the second γ-ray detection signal having the energy lower than the first set energy are added to generate the addition signal, the first radiation detector or the second radiation detector When Compton scattering of γ rays occurs, a γ ray detection signal of Compton scattered γ rays is not input to the adder. For this reason, incidental coincidence due to the detection of γ-rays having energy in the vicinity of the cascade γ-rays by γ-rays generated by Compton scattering of background γ-rays can be suppressed. Therefore, it is possible to further improve the accuracy of coincidence counting of cascade γ rays with different energies radiated from the measurement target nuclide.

Preferably, the first γ-ray detection signal output from the first radiation detector is input to the first gate signal generator and the first delay device, respectively, and the first γ-ray detection signal input by the first gate signal generator. The first gate opening signal is not output when the energy of the first γ-ray detection signal is equal to or lower than the first setting energy. The time required for the first delay device to output the first γ-ray detection signal input and the first gate signal generator to output the first gate open signal after the first γ-ray detection signal is input. When the third γ-ray detection signal output from the third radiation detector is input to the third delay device, and the first delay device outputs the input first γ-ray detection signal. The delay device outputs the input third γ-ray detection signal, and the first gate device inputs the first gate open signal from the first gate signal generator when the third γ-ray detection signal is not output from the third delay device. The first γ-ray detection signal input from the first delay device is output to the adder,
The second γ-ray detection signal output from the second radiation detector is input to the second gate signal generation device and the second delay device, respectively, and the second gate signal generation device inputs the energy of the input second γ-ray detection signal. Is larger than the first set energy, the second gate open signal is not output, and when the energy of the input second γ-ray detection signal is equal to or lower than the previous one set energy, the second gate open signal is The second delay device delays the input second γ-ray detection signal by the time required until the second gate signal generator inputs the second γ-ray detection signal and outputs the second gate open signal. The fourth γ-ray detection signal output from the fourth radiation detector is input to the fourth delay device, and when the second delay device outputs the input second γ-ray detection signal, the fourth delay device is output. Outputs the input fourth γ-ray detection signal, and the second gate device receives the second gate open signal from the second gate signal generator when the fourth γ-ray detection signal is not output from the fourth delay device. And outputting the second γ-ray detection signal input from the second delay device to the adder,
It is desirable that the addition signal is generated by an addition device that receives the first γ-ray detection signal output from the first gate device and the second γ-ray detection signal output from the second gate device.

  According to the present invention, accidental coincidence can be suppressed, and coincidence counting of cascade γ rays with different energies can be performed with high accuracy.

It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 1 which is one suitable Example of this invention. It is explanatory drawing which shows the state which has arrange | positioned the radiation detection apparatus shown in FIG. 1 in the reactor primary system piping vicinity of a measuring object. It is explanatory drawing which shows an example of the energy spectrum of the gamma ray radiated | emitted from the nuclear reactor primary piping at the time of operation | movement of a boiling water nuclear power plant. It is explanatory drawing which shows the removal setting energy set to the energy smaller than the minimum of the coincidence peak in the energy spectrum shown by FIG. It is explanatory drawing which shows the energy spectrum of the gamma ray in the state which removed the gamma ray detection signal which has energy larger than removal setting energy. FIG. 6 is an enlarged view near the coincidence peak in the energy spectrum shown in FIG. 5. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 2 which is another Example of this invention. It is explanatory drawing which shows the energy spectrum of the gamma ray obtained in Example 2. FIG. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 3 which is another Example of this invention. It is a block diagram of the modification of the radiation measuring device used in Example 3. FIG. It is a block diagram of the other modification of the radiation measuring device used in Example 3. FIG. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 4 which is another Example of this invention. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 5 which is another Example of this invention. It is a block diagram of the modification of the radiation measuring device used in Example 5. FIG. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 6 which is another Example of this invention. It is a block diagram of the radiation measuring device used for the radiation measuring method of Example 7 which is another Example of this invention.

  The inventors have newly found that when cascade gamma rays having a plurality of energies are emitted from the measurement target nuclide, accidental coincidence counting is performed, and coincidence counting of these cascade gamma rays may be difficult. I found it. Therefore, the inventors measured the dose rate of background γ rays in order to improve the accuracy of coincidence counting of cascade γ rays having multiple energies while avoiding accidental coincidence in cascade γ rays having multiple energies. A method of simultaneous counting of cascaded γ-rays was studied, which enables accurate counting of cascaded γ-rays having a plurality of energies even when the target nuclides are higher than cascaded γ-rays having a plurality of energies. The result of this examination will be described below.

Examples of radionuclides that emit cascade gamma rays include Al-26, K-42, Ti-51, V-48, Mn-52, Mn-54, Co-56, Co-58, Co-60, and Y. -88, Nb-94, Ag-110, In-116, Sb-124, Te-132, Cs-134, Tl-208, and the like. The cascade γ-ray emission process will be described. For example, Co-60 undergoes β ^- decay with a half-life of 5.27 years. By this decay, Co-60 is destroyed into Ni-60 in an excited state. Since the excited Ni-60 is in the ground state, cascade gamma rays having this ground state energy are emitted from the excited Ni-60. This cascade γ-ray has two or more energies, and is emitted in the 4π direction at almost the same time. The time difference radiated from Ni-60 between, for example, γ-rays having an energy of 1.17 MeV and γ-rays having an energy of 1.33 MeV emitted from excited Ni-60 is approximately 0.4 ps. Since this time difference is the same time in the pulse measurement processing time of a normal radiation monitor system, it can be ignored. The time difference associated with the emission of cascade gamma rays from other radionuclides can be ignored, as is the time difference in cascade gamma rays emitted from Ni-60.

  For example, there are N-13, N-16, F-18, O-19, and the like as disturbing radionuclides contained in the cooling water flowing in the reactor primary system piping.

A general radiation detector is used as the plurality of radiation detectors that detect cascade γ rays emitted from the measurement target nuclide at substantially the same time. For example, as the scintillation radiation detector, any one of NaI (Tl), CsI (Ce), LaCl ₃ (Ce), LaBr ₃ (Ce), BGO, GSO (Ce), and LuAG (Pr) was used. The scintillation radiation detector is a semiconductor radiation detector using Si, Ge, CdTe, CZT or the like as the semiconductor radiation detector. Any radiation detector can be used in the radiation measurement method of the present invention.

  For example, a radionuclide adhering to the inner surface of the reactor primary system pipe becomes a measurement target nuclide. The reactor primary system piping is connected to a reactor pressure vessel having a core disposed therein. Cooling water flowing in the reactor primary system piping is used to cool a plurality of fuel assemblies loaded in the core. Radionuclides adhering to the inner surface of the reactor primary system piping and γ rays radiated from the radionuclides contained in the cooling water flowing in the reactor primary system piping are radiated from the reactor primary system piping. The inventors examined the cascade γ rays emitted from the measurement target nuclide.

  An example of an energy spectrum by γ rays radiated from the reactor primary system piping is shown in FIG. The energy spectrum illustrated in FIG. 3 is an energy spectrum when Co-60 is a measurement target nuclide and N-16 is a disturbing radionuclide. As Co-60, there are Co-60 attached to the inner surface of the reactor primary system piping and Co-60 contained in the cooling water flowing in the reactor primary system piping. N-16 is contained in the cooling water flowing in the reactor primary system piping.

  N-16 (nuclide to be disturbed) emits 6.1 MeV γ-rays, and the energy spectrum shown in FIG. 3 is N-16 total absorption peak 22, Compton distribution 23 by Compton scattering, and single due to electron pair production. An escape peak 24, a double escape peak 25, and the like are included. When the radiation intensity of Co-60 adhering to the inner surface of the reactor primary system piping is smaller than the radiation intensity of N-16 contained in the cooling water flowing in the reactor primary system piping, the Co-60 total absorption peak region 26 Cascade γ-rays with different energies of Co-60, ie 1.17 MeV and 1.33 MeV cascade γ-rays, may be hidden in the N-16 Compton distribution 23 . For this reason, it becomes difficult to discriminate the total absorption peak of Co-60 from the background component.

  In consideration of simultaneous counting of cascade γ-rays having different energies, the inventors of a pair of cascade γ-rays having different energies radiated from the measurement target nuclide and simultaneously counting a pair of cascade γ-rays. From the total energy (when there are multiple measurement target nuclides, the lowest total energy of the total energy of a pair of cascade γ rays counted simultaneously among the respective cascade γ rays emitted from those measurement nuclides) And the largest energy among the cascade γ-rays radiated from the measurement target nuclide (if there are multiple measurement target nuclides, the largest of the cascade γ-rays emitted from those measurement nuclides) To remove high energy of γ rays within a range of energy greater than (large energy) The removal setting energy (first setting energy) 27 was set (see FIG. 4). By removing γ-rays having an energy higher than the removal setting energy 27, the total energy of a pair of cascade γ-rays counted simultaneously can be obtained.

  For example, in Co-60, since the total energy of the pair of cascade γ rays is 2.5 MeV, the removal setting energy 27 is set to 2.0 MeV. As a result, by removing γ-rays having an energy higher than 2.0 MeV from the detected γ-rays, it is possible to eliminate the influence of the high energy of N-16, the nuclide to be disturbed, and suppress coincidence coincidence. can do.

  Among the detected γ-rays having an energy less than or equal to the removal setting energy 27, the total energy of the γ-rays detected by one radiation detector and the other γ-rays detected by the other radiation detector is the measurement target. When the total energy (set energy) of a pair of cascade γ-rays radiated from the nuclide is reached, the coincidence is performed assuming that these γ-rays are a pair of cascade γ-rays radiated from the measurement target nuclide. Since γ rays having energy exceeding the removal setting energy 27 are removed, γ rays having energy in the N-16 high energy region 28 are not counted.

  A pair of cascade γ rays (for example, 1.17 MeV cascade γ rays and 1.33 MeV cascade γ rays emitted from a measurement target nuclide (eg, Co-60) attached to a structural member (eg, primary reactor piping) Are detected separately by two radiation detectors arranged in the vicinity of the structural member. Among the many γ-ray detection signals output from these radiation detectors, γ-ray detection signals having energy exceeding the removal setting energy 27 (2.0 MeV in the case of Co-60 as an example) are removed. Of the many γ-ray detection signals output from the respective radiation detectors, 2 are γ-ray detection signals having energy equal to or less than the removal setting energy 27 and are output separately from the two radiation detectors substantially simultaneously. By adding two γ-ray detection signals, an addition signal of these γ-ray detection signals can be obtained. The energy of this added signal (the total value of the energy of each of the two γ-ray detection signals) becomes the total energy of the pair of cascade γ-rays radiated from the measurement target nuclide (setting energy: 2.5 MeV for Co-60). Then, these γ-ray detection signals are based on a pair of cascade γ-rays emitted from the measurement target nuclide (for example, Co-60). A coincidence peak 29 (see FIG. 5) can be obtained by counting the sum signal having the total energy of a pair of cascade γ rays emitted from the measurement target nuclide. Simultaneous counting of cascade γ-rays with different energies radiated from the measurement target nuclide means that the γ-ray detection signal output from one radiation detector that detects one cascade γ-ray emitted from the measurement target nuclide, It is to add other γ-ray detection signals output from other radiation detectors that detect other cascade γ-rays having different energies that are radiated substantially simultaneously from the measurement target nuclide.

  FIG. 6 is an enlarged view of the vicinity of the coincidence peak 29 shown in FIG. Even in the vicinity of the coincidence peak 29, as shown in FIG. 6, there is an accidental coincidence component (incident coincidence distribution 31). Also in the coincidence coincidence distribution 31, the coincidence coincidence peak 30 in which the count value of the coincidence coincidence shows a maximum value is formed. The count value of the coincidence coincidence peak 30 is very small compared to the count value of the coincidence peak 29. For this reason, the accuracy of coincidence counting of cascaded γ rays emitted from the measurement target nuclide is remarkably improved.

  As the coincidence coincidence existing in the vicinity of the coincidence peak 29, for example, when the measurement target nuclide is Co-60 and the interfering radionuclide is N-16, one of a pair of γ rays to be subjected to the coincidence count is When the component produced by the Co-60 cascade γ-ray and the other by N-16 Compton scattering is input to the radiation detector with energy near the Co-60 cascade γ-ray, or two radiation detections When a component generated by N-16 Compton scattering is input to the detector with energy in the vicinity of the Co-60 cascade gamma rays, or Co-60 cascade gamma rays from different sources are input to the two radiation detectors. It is time to

  The coincidence coincidence peak 30 and the coincidence coincidence distribution 31 shown in FIG. 6 are examples of background components. The incident coincidence peak 30 is obtained when each component generated by Co-60 cascade γ-ray and N-16 Compton scattering is input to the radiation detector with energy near the Co-60 cascade γ-ray 13. Alternatively, it occurs when Co-60 cascade gamma rays from different sources are input to the two radiation detectors. The coincidence coincidence distribution 31 indicates that when components generated by N-16 Compton scattering are input to the two radiation detectors with energy in the vicinity of the Co-60 cascade γ-ray 13 or the Co-60 cascade γ. This is a distribution observed when each component generated by the line and N-16 Compton scattering has energy near the Co-60 cascade γ-ray 13 and is input to the radiation detector.

  An embodiment of the present invention will be described below in consideration of the following examination results.

  A radiation measurement method according to the first embodiment which is a preferred embodiment of the present invention will be described with reference to FIGS.

  A radiation measurement apparatus used in the radiation measurement method of the present embodiment will be described with reference to FIGS. The radiation measuring device 45 of this embodiment includes radiation detecting devices 16A and 16B, a signal processing device 17, and a display device 11. The radiation detection device 16A includes a radiation detector (first radiation detector) 1A and a preamplifier 3A connected to the radiation detector 1A, and the radiation detection device 16B includes a radiation detector (second radiation detector) 1B and It has a preamplifier 3B connected to the radiation detector 1B. The high voltage power source 2A is connected to the radiation detector 1A, and the high voltage power source 2B is connected to the radiation detector 1B. As the preamplifiers 3A and 3B, feedback resistor type preamplifiers, transistor reset type preamplifiers, and the like are used.

As the radiation detectors 1A and 1B, scintillation radiation detectors (or semiconductor radiation detectors), which are general radiation detectors, are used. As a scintillation radiation detector, scintillation radiation using any of NaI (Tl), CsI (Ce), LaCl ₃ (Ce), LaBr ₃ (Ce), BGO, GSO (Ce), LuAG (Pr), etc. It is a detector. The semiconductor radiation detector is a semiconductor radiation detector using Si, Ge, CdTe, CZT, or the like.

  The signal processing device 17 includes an output branching unit 4A, a high level wave high discriminator 5A, a delay circuit 6A, a linear gate 7A, an output branching unit 4B, a high level wave high discriminator 5B, a delay circuit 6B, a linear gate 7B, an addition amplifier (addition) Apparatus) 8, a linear amplifier 9, and a multichannel wave height analyzer (counter) 10. The signal selection device includes a high level wave high discriminator (first gate signal generator) 5A, a delay circuit (first delay device) 6A, a linear gate (first gate device) 7A, and a high level wave height discriminator (second gate signal). Generator 5B, delay circuit (second delay device) 6B, and linear gate (second gate device) 7B. The output branching device 4A, the high level wave height discriminator 5A, the delay circuit 6A, and the linear gate 7A process the γ-ray detection signal output from the radiation detector 1A. The output branching device 4A is connected to the preamplifier 3A and the delay circuit 6A. Linear gate 7A is connected to delay circuit 6A. A high level wave height discriminator 5A is connected to the output branching device 4A and the linear gate 7A.

  The output branching device 4B, the high level wave height discriminator 5B, the delay circuit 6B, and the linear gate 7B process the γ-ray detection signal output from the radiation detector 1B. The output branching device 4B is connected to the preamplifier 3B and the delay circuit 6B. Linear gate 7B is connected to delay circuit 6B. A high level wave height discriminator 5B is connected to the output branching device 4B and the linear gate 7B.

  The summing amplifier 8 is connected to the linear gates 7A and 7B and further connected to the linear amplifier 9. A multi-channel wave height analyzer 10 is connected to the linear amplifier 9 and the display device 11.

  The radiation measurement method of the present embodiment measures radiation for a reactor primary system piping (hereinafter referred to as primary system piping) of a boiling water nuclear plant. Although not shown, the boiling water nuclear power plant has a nuclear reactor in which a reactor core is disposed in a reactor pressure vessel. A plurality of fuel assemblies (not shown) including nuclear fuel material are loaded in the core. The primary system pipe 18 (see FIG. 2) is, for example, a recirculation system pipe and is connected to a reactor pressure vessel.

  During operation of the boiling water nuclear power plant, the cooling water (coolant) in the reactor pressure vessel is boosted by driving a recirculation pump (not shown) provided in the primary system pipe 18, and the reactor Injected from a nozzle of a jet pump (not shown) provided in the pressure vessel. The cooling water present around the nozzle (not shown) in the reactor pressure vessel is sucked into the bell mouth (not shown) of the jet pump by the action of the injected cooling water and supplied to the reactor core. The The cooling water supplied to the reactor core is heated by heat generated by fission of nuclear fuel material in the fuel assembly, and a part thereof becomes steam. This steam is guided to the turbine by a main steam pipe (not shown) connected to the reactor pressure vessel.

  As shown in FIG. 2, the heat insulating material 20 surrounds the outer surface of the primary system pipe 18 and is attached to the primary system pipe 18. Cooling water 19 containing radionuclides (for example, Co-58, Co-60, Mn-54, Fe-59, N-13, N-16, F-18, O-19, etc.) in the reactor pressure vessel However, Co-58, Co-60, Mn-54, and Fe-59 as the measurement target nuclides 12 adhere to the inner surface of the primary system pipe 18. N-13, N-16, F-18, and O-19 contained in the cooling water 19 are interfering radionuclides 14. Many of these interfering radionuclides 14 are short half-life nuclides that exist only during operation of a boiling water nuclear plant. Background gamma rays 15 are emitted from interfering radionuclides 14.

  The radiation detectors 1A and 1B operate by applying a voltage from the high-voltage power supplies 2A and 2B. The voltages applied to the radiation detectors 1A and 1B are set to set voltages. This set voltage is a fixed value or an arbitrarily set value. In the present embodiment, high voltage power supplies 2A and 2B that can arbitrarily adjust the set voltage are used. The high voltage power supplies 2A and 2B adjust the voltage applied to the radiation detectors 1A and 1B so that the energy resolution of the radiation detectors 1A and 1B is optimized. When the energy resolution of the radiation detectors 1A and 1B does not hinder the detection of the cascade γ-ray 13 by adjusting the applied voltage, the radiation detectors 1A and 1B are changed by changing the applied voltage with the high-voltage power supplies 2A and 2B. It is possible to adjust the gain of each γ-ray detection signal output from.

  The radiation detection devices 16 </ b> A and 16 </ b> B are arranged so as to face the measurement region 21 of the primary system pipe 18. A number of gamma rays including the cascade gamma rays 13 are emitted from the primary system pipe 18. Respective γ rays incident on the radiation detectors 1A and 1B are detected by the radiation detectors 1A and 1B. A pair of cascade γ-rays 13 having different energies are also emitted from the measurement target nuclide 12 attached to the inner surface of the primary system pipe 18 which is the measurement region 21 and detected by the radiation detectors 1A and 1B. A γ-ray detection signal output when the radiation detector 1A detects γ-rays is referred to as a γ-ray detection signal A for convenience. A γ-ray detection signal output when the radiation detector 1B detects γ-rays is referred to as a γ-ray detection signal B for convenience.

  In the present embodiment, the measurement target nuclide 12 attached to the inner surface of the primary pipe 18 in the measurement region 21 will be described as Co-60. One cascade gamma ray 13 emitted from Co-60 substantially identically is a cascade gamma ray of 1.17 MeV, and the other cascade gamma ray 13 is a cascade gamma ray of 1.33 MeV. When the radiation detector 1A detects a 1.17 MeV cascade γ-ray 13, it outputs a 1.17 MeV γ-ray detection signal A. When the radiation detector 1B detects the 1.33 MeV cascade γ-ray 13, it outputs a 1.33 MeV γ-ray detection signal B.

  The γ-ray detection signal A output from the radiation detector 1A that has detected γ-rays is input to the preamplifier 3A and amplified. The output branching device 4A outputs the γ-ray detection signal A input from the preamplifier 3A to each of the high level wave height discriminator 5A and the delay circuit 6A. The output branching devices 4A and 4B may be output branching devices such as T-type connectors that are normally used.

  The high level wave height discriminator 5A does not output the first gate opening signal when the energy of the input γ-ray detection signal A is larger than the removal setting energy 27, and the energy of the input γ-ray detection signal A is set to be removed. When the energy is 27 or less, the first gate open signal is output. In other words, the high level wave height discriminator 5A outputs the first gate open signal only when the energy of the input γ-ray detection signal A is equal to or less than the removal setting energy 27. The first gate opening signal output from the high level wave height discriminator 5A is input to the linear gate 7A.

  When the measurement target nuclide is Co-60, the removal setting energy 27 is set to 2.0 MeV, for example. In the high level wave height discriminator 5B, 2.0 MeV is set as the removal setting energy 27. When the high-level wave height discriminator 5A receives the γ-ray detection signal A having energy of 2.0 MeV or less, for example, when the γ-ray detection signal A of 1.17 MeV is input from the radiation detector 1A, the first gate An open signal is output to the linear gate 7A. When the radiation detector 1A detects, for example, cosmic rays and gamma rays emitted from N-16 of 6.1 MeV contained in the cooling water 19 flowing in the primary system pipe 18, the radiation detector 1A detects cosmic rays. Γ-ray detection signal A1 having the energy of 6.1 and 6.1 MeV γ-ray detection signal A2. The high level wave height discriminator 5A to which the γ-ray detection signals A1 and A2 are input does not output the first gate open signal.

  2.0 MeV set as the removal setting energy 27 in the high-level wave height discriminators 5A and 5B is 1.17 MeV cascade γ-rays 13 and 1 emitted from Co-60, which is a measurement target nuclide, and counted simultaneously. The energy is less than the total energy (2.5 MeV) of the cascade γ rays 13 of 33 MeV and larger than the largest energy (1.33 MeV) among the energy of the cascade γ rays emitted from Co-60. For example, when Co-58, Co-60, Mn-54, and Fe-59 are measurement nuclides, the removal setting energy 27 set in the high-level wave height discriminators 5A and 5B is set to Co-58, A pair of cascades that are larger than the largest energy of cascade gamma rays emitted from each of Co-60, Mn-54, and Fe-59 and that are simultaneously counted by the cascade gamma rays emitted from those measurement objects It is set to a value smaller than the smallest lower limit value among the total energy lower limit values of γ rays.

The delay circuit 6A that receives the γ-ray detection signal A output from the output branching device 4A outputs the γ-ray detection signal A after being delayed by a set time T ₁ from the time when the γ-ray detection signal A is input. The set time T ₁ for delaying the output of the γ-ray detection signal A is such that the energy of the input γ-ray detection signal A is removed from the time when the high-level wave height discriminator 5A inputs the γ-ray detection signal A. This is the time required until the first gate open signal is output when the determination process is performed and the determination is “Yes”. The γ-ray detection signal A output from the delay circuit 6A is input to the linear gate 7A.

  The linear gate 7A outputs the γ-ray detection signal A input from the delay circuit 6A to the summing amplifier 8 at the same time as the input time of the first gate opening signal output from the high level wave height discriminator 5A.

The γ-ray detection signal B output from the radiation detector 1B is amplified by the preamplifier 3B and input to the output branching unit 4B. The output branching device 4B outputs the γ-ray detection signal B to each of the high level wave height discriminator 5B and the delay circuit 6B. The high level wave height discriminator 5B performs a determination process similar to that of the high level wave height discriminator 5A on the input γ-ray detection signal B. When the energy of the γ-ray detection signal B input to the high-level wave height discriminator 5B is 2.0 MeV or less which is the removal setting energy 27, for example, the energy of the γ-ray detection signal B is 1.33 MeV. Sometimes, the high level wave height discriminator 5B outputs the second gate open signal to the linear gate 7B. Delay circuit 6B, similar to the delay circuit 6A, only time set the entered γ ray detection signal B T ₂ delayed outputs to the linear gate 7B. Set time T ₂ is the delay time of the delay circuit 6B, a high-level pulse height discriminator 5B is from the time you enter the γ ray detection signal B, the energy of the input γ ray detection signal B is removed setting energy 27 follows This is the time required to output the second gate open signal when this determination is “Yes” and is the same as the set time T ₁ in the delay circuit 6A. The linear gate 7B outputs the γ-ray detection signal B input from the delay circuit 6B to the addition amplifier 8 at the same time as the input time of the γ-ray detection signal B output from the high level wave height discriminator 5B.

  The adding amplifier 8 adds the γ-ray detection signal A output from the linear gate 7A and the γ-ray detection signal B output from the linear gate 7B. This addition is a coincidence of cascade gamma rays with different energies. The γ-ray detection signal A and the γ-ray detection signal B output from the linear gate 7A and the linear gate 7B substantially at the same time are 1.17 MeV cascaded γ-rays 13 emitted from Co-60, which is the measurement target nuclide. Incident on the radiation detector 1A and incident on the radiation detector 1B of the 1.33 MeV cascade γ-ray 13 at substantially the same time are output substantially simultaneously from the respective radiation detectors. It is. The summing amplifier 8 substantially generates two γ-ray detection signals (γ-ray detection signals A and B) generated when the radiation detectors 1A and 1B detect cascade γ-rays 13 having different energies, respectively. Input simultaneously and add these γ-ray detection signals. That is, these signals are simultaneously counted.

  The linear amplifier 9 inputs a signal (for convenience, referred to as an addition signal) generated by adding (simultaneously counting) the γ-ray detection signal A and the γ-ray detection signal B by the addition amplifier 8 and inputs the addition signal. Amplify linearly. The addition signal linearly amplified by the linear amplifier 9 is input to the multichannel wave height analyzer 10. The multichannel wave height analyzer 10 counts the added signal for each energy (wave height value). The total energy of each cascade γ-ray (a 1.17 MeV cascade γ-ray and a 1.33 MeV cascade γ-ray) 13 with different energies radiated from the measurement target nuclide Co-60 is 2.5 MeV. The multichannel wave height analyzer 10 also counts this 2.5 MeV addition signal among the input addition signals. The count value for each energy of the added signal obtained by the multichannel wave height analyzer 10 (including the count value of the total energy of each cascade γ-ray 13 having different energy radiated from a certain measurement target nuclide) is displayed on the display device 11. Is displayed.

  In this embodiment, γ-ray detection having an energy higher than the removal setting energy 27 (2.0 MeV) that causes the coincidence coincidence due to the above-described operation of the high level wave height discriminator 5A, the delay circuit 6A, and the linear gate 7A. It is possible to prevent the signal A from being input to the summing amplifier 8 from the linear gate 6A. Further, due to the above-described operation of the high level wave height discriminator 5B, the delay circuit 6B, and the linear gate 7B, the γ-ray detection signal B having an energy higher than the removal setting energy 27 (2.0 MeV) that causes the coincidence coincidence is generated. Input from the linear gate 6B to the summing amplifier 8 can be prevented. For this reason, when the addition amplifier 8 adds the γ-ray detection signal A and the γ-ray detection signal B (simultaneous counting), the γ-ray detection signal A or the γ-ray detection signal B having energy higher than the removal setting energy 27 and others. Addition of the γ-ray detection signals (coincident coincidence) can be avoided. Since the coincidence coincidence is remarkably reduced, the influence of the γ-ray detection signal having an energy higher than the removal setting energy 27 is remarkably lowered, and the coincidence of each cascade γ-ray with different energy radiated from the measurement target nuclide is accurately performed. Can be done well. Thereby, the coincidence peak 29 of each cascade γ-ray having different energy radiated from the measurement target nuclide can be accurately observed.

  In this example, the signal selection device (high level wave height discriminator 5A, delay circuit 6A, linear gate 7A, high level wave height discriminator 5B, delay circuit 6B and linear gate 7B) was radiated from the measurement target nuclide. Since the γ-ray detection signal of the background γ-ray 15 having energy corresponding to the total energy of the cascade γ-rays having different energies is not input to the adding amplifier 8, the γ-ray of the high-energy background γ-ray 15 on the energy spectrum. It is possible to measure the coincidence peak of a pair of cascade γ rays in the absence of a detection signal. In addition, even when a background component due to accidental coincidence appears in the energy spectrum, the coincidence peak can be determined from the total energy of each cascade γ-ray emitted from the measurement target nuclide, so highly accurate cascade γ-ray coincidence can be performed. It becomes possible.

  When the linear gate 7A receives the first gate open signal from the high level wave height discriminator 5A, the γ-ray detection signal A input from the delay circuit 6A is output to the addition amplifier 8, and the linear gate 7B receives the high level wave height. When the second gate opening signal is input from the discriminator 5B, the γ-ray detection signal B input from the delay circuit 6B is output to the adder amplifier 8. Therefore, one cascaded γ-ray output from a certain measurement target nuclide Γ-ray detection signal A that is the output of the radiation detector 1A that has detected the γ-ray, and γ that is the output of the radiation detector 1B that has detected other cascade γ-rays with different energies that are output substantially simultaneously from the measurement target nuclide. The line detection signal B can be input to the summing amplifier 8 substantially simultaneously. Thereby, it is not necessary to provide a configuration for giving time information to the γ-ray detection signals A and B, and it is possible to perform simultaneous counting of cascade γ-rays with different energy radiated from the measurement target nuclide with a simple configuration.

  In the multichannel wave height analyzer 10, not only 2.5 MeV for the pair of cascade γ rays 13 emitted from Co-60, but also the total energy of the pair of cascade γ rays emitted from Co-58, emitted from Mn-54. It is possible to count each added signal having the total energy of the pair of cascade γ rays and the total energy of the pair of cascade γ rays emitted from Fe-59. These count values are also displayed on the display device 11.

  In the radiation measurement method of the present embodiment that can significantly suppress accidental coincidence, the radiation detectors 1A and 1B of the radiation measurement device 45 are disposed, for example, in the vicinity of the primary system pipe 18 of the boiling water nuclear power plant. As a result, during the operation of the boiling water nuclear power plant in which the dose rate of the background γ rays emitted from the interfering radionuclide 14 is high, the dose rate in the measurement region of the primary piping 18 is continuously measured with high accuracy. be able to.

  A radiation measurement method according to embodiment 2, which is another embodiment of the present invention, will be described with reference to FIG.

  First, the radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measurement apparatus 45A of the present embodiment has a configuration in which the signal processing device 17 is replaced with the signal processing device 17A in the radiation measurement device 45 of the first embodiment. The other configuration of the radiation measuring apparatus 45A is the same as that of the radiation measuring apparatus 45. The signal processing device 17A has a configuration in which the high level wave height discriminators 5A and 5B are replaced with high level / low level wave height discriminators 32A and 32B in the signal processing device 17, and the other configuration of the signal processing device 17A is a signal processing device. 17 is the same.

  The radiation measurement method of the present embodiment will be described focusing on the processing in the high level / low level wave height discriminators 32A and 32B that are different from the signal processing device 17 used in the first embodiment.

  Similarly to the first embodiment, the radiation detectors 1A and 1B separately generate cascade γ-rays 13 having different energies emitted from the measurement target nuclides 12 attached to the inner surface of the primary system pipe 18 in the measurement region 21 of the primary system pipe 18. To detect. The γ-ray detection signal A output from the radiation detector 1A is input to the high level / low level wave height discriminator 32A and the delay circuit 6A via the preamplifier 3A and the output branching unit 4A. The γ-ray detection signal B output from the radiation detector 1B is input to the high level / low level wave height discriminator 32B and the delay circuit 6B via the preamplifier 3B and the output branching device 4B.

  The high level / low level wave height discriminators 32A and 32B set not only the removal setting energy 27 (first setting energy) but also the removal setting energy 49 (second setting energy). The removal setting energy 49 is lower than the removal setting energy 27, and is the total absorption peak region of the measurement target nuclide (when the measurement target nuclide is Co-60, the total absorption peak region 26 of Co-60). The energy is set to be smaller than the lower limit energy and larger than zero. The energy region between the removal setting energy 27 and the removal setting energy 49 is a gate passage region 34 as shown in FIG. The high-level / low-level wave height discriminator 32 </ b> A receives a γ-ray detection signal A having energy included in the gate passage region 34 (γ-ray detection signal A having energy between the removal setting energy 27 and the removal setting energy 49). When input, the first gate open signal is output to the linear gate 7A. The high-level / low-level wave height discriminator 32B generates a γ-ray detection signal B having energy included in the gate passage region 34 (γ-ray detection signal B having energy between the removal setting energy 27 and the removal setting energy 49). When input, the 21st gate open signal is output to the linear gate 7B. In this embodiment, since the measurement target nuclide is Co-60, the removal setting energy 27 set by the high level / low level wave height discriminators 32A and 32B is 2.0 MeV, and the removal setting energy 49 is 1.0 MeV. It is. However, the removal setting energy 27 and the removal setting energy 49 are not limited to these values.

Set time T ₃ for delaying the delay circuit γ ray detection signal A inputted in 6A in this embodiment, high-level and low-level pulse height discriminator 32A is from the time you enter the γ ray detection signal A, and input γ rays This is the time required to output the first gate opening signal when the energy of the detection signal A is the energy in the gate passage region 34. Setting time T ₄ for delaying the γ-ray detection signal B inputted in the delay circuit 6B is a high level and low level pulse height discriminator 32B is, from the time you enter the γ ray detection signal B, and the input of the γ ray detection signal B This is the time required to output the second gate opening signal when the energy is in the gate passage region 34. Setting time _{T 4} in the delay circuit 6B is the same as the set time _{T 3} in the delay circuit 6A.

  The γ-rays or X-rays having lower energy than the Co-60 total absorption peak region 26 of the measurement target nuclide 12 (referred to as Co-60) by the disturbing radionuclide 14 detected by each of the radiation detectors 1A and 1B are The component is not related to the coincidence peak 29 obtained by coincidence of the cascade γ rays 13 emitted from the measurement target nuclide. As in the first embodiment, if the output to the summing amplifier 8 of the γ-ray detection signals A and B having energy exceeding the removal setting energy 27 is blocked in the linear gates 7A and 7B, the low gain obtained by the summing amplifier 8 can be obtained. There is a possibility that a sum signal of energy γ rays (or X rays) and other γ rays is input to the multichannel wave height analyzer 10.

  When an addition signal reflecting low-energy γ-rays (or X-rays) is input to the multi-channel wave height analyzer 10 and the multi-channel wave height analyzer 10 counts the added signals, the multi-channel wave height analyzer 10 The dead time due to the analog-to-digital conversion time provided may increase. When a γ-ray detection signal having an energy exceeding the removal setting energy 27 and a γ-ray detection signal having an energy less than the removal setting energy 49 are input, the gate opening signal (first and second gate opening signal) is not output high. The radiation measuring apparatus 45A equipped with the level / low level wave height discriminators 32A and 32B exceeds the removal setting energy 27 when the gamma rays emitted from the measurement region 21 are detected by the radiation detectors 1A and 1B in the same measurement time. Multi-channel pulse height analyzer by reducing dead time compared to radiation measuring device 45 provided with high level wave height discriminators 5A and 5B that do not output a gate open signal only when a γ-ray detection signal having high energy is input. The count value of the coincidence count obtained at 10 increases. Therefore, the measurement error in the radiation measuring apparatus 45A provided with the high level / low level wave height discriminators 32A and 32B can be reduced.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Furthermore, since the present embodiment includes the high-level / low-level wave height discriminators 32A and 32B, γ-rays (or X-rays) having lower energy than the cascade γ-rays 13 of the measurement target nuclide 12 are high-level and low-level. Little is output from the level wave height discriminators 32A and 32B. For this reason, the dead time in the multi-channel wave height analyzer 10 can be suppressed, and faster and more accurate simultaneous counting can be performed.

  A radiation measurement method according to embodiment 3, which is another embodiment of the present invention, will be described with reference to FIG.

  First, the radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measuring apparatus 45B of the present embodiment has a configuration in which the signal processing device 17 is replaced with the signal processing device 17B in the radiation measuring device 45 of the first embodiment, and a thermometer 35 and a gain adjusting device (control device) 36 are added. Other configurations of the radiation measuring apparatus 45B are the same as those of the radiation measuring apparatus 45. The signal processing device 17B is different from the signal processing device 17 in that the gain of the summing amplifier 8 can be adjusted based on the output of the gain adjusting device 36. The other configuration of the signal processing device 17B is the same as that of the signal processing device 17. The same.

  A thermometer 35 is installed in an area where the radiation detectors 1A and 1B are arranged. The thermometer 35 is connected to the gain adjusting device 36, and the gain adjusting device 36 is connected to the high-voltage power supplies 2 A and 2 B and the summing amplifier 8. As the thermometer 35, a general thermometer such as a thermocouple or a resistance temperature detector is used.

  In the radiation measurement method according to the present embodiment, a description will be given focusing on the differences from the radiation measurement method according to the first embodiment. The thermometer 35 measures the temperature near the radiation detectors 1A and 1B in the area where the radiation detectors 1A and 1B are installed. The measured temperature is input from the thermometer 35 to the gain adjusting device 36. The gain adjusting device 36 controls the high-voltage power supplies 2A and 2B and the summing amplifier 8 based on the input temperature. Specifically, the gain adjusting device 36 controls the high voltage power source 2A to adjust the voltage applied from the high voltage power source 2A to the radiation detector 1A, and controls the high voltage power source 2B to change the voltage from the high voltage power source 2B to the radiation detector 1B. The applied voltage is adjusted, and the summing amplifier 8 is controlled to adjust the gain value of the summing amplifier 8.

  Similarly to the signal processing device 17, the signal processing device 17 </ b> B processes the γ-ray detection signals A and B output from the preamplifiers 3 </ b> A and 3 </ b> B. The multichannel wave height analyzer 10 counts the sum signal output from the summing amplifier 8.

  In the radiation detectors 1A and 1B, the output level of the output γ-ray detection signal has temperature dependence. The output gains of the radiation detectors 1A and 1B are adjusted by controlling the high-voltage power supplies 2A and 2B based on the temperature measured by the thermometer 35 and adjusting the voltages applied to the radiation detectors 1A and 1B. Therefore, the temperature dependence of the radiation detectors 1A and 1B can be eliminated, and temperature compensation can be performed for the γ-ray detection signals output from these radiation detectors. Therefore, changes due to temperature of the γ-ray detection signals output from the radiation detectors 1A and 1B can be suppressed, and more accurate γ-ray detection signals can be output from the respective radiation detectors.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In the present embodiment, each voltage applied to the radiation detectors 1A and 1B is adjusted by a gain adjusting device 36 that inputs the temperatures in the vicinity of the radiation detectors 1A and 1B measured by the thermometer 35. Since the gain is adjusted, deterioration of the energy resolution of the energy spectrum obtained by the multichannel wave height analyzer 10 can be suppressed.

  The radiation measuring device 45B may be changed like the radiation measuring device 45C shown in FIG. 10 or like the radiation measuring device 45D shown in FIG. The radiation measuring device 45C has a configuration in which the voltage applied to the radiation detectors 1A and 1B from the high voltage power supplies 2A and 2B is adjusted by a gain adjusting device 36 that inputs the output of the thermometer 35. In the radiation measuring device 45C, the gain adjusting device 36 does not adjust the gain of the summing amplifier 8. The radiation measuring device 45D has a configuration in which the gain of the summing amplifier 8 is adjusted by a gain adjusting device 36 that inputs the output of the thermometer 35. In the radiation measuring device 45D, the gain adjusting device 36 does not control the high voltage power supplies 2A and 2B. The configuration of the radiation measurement devices 45C and 40D other than the gain adjustment device 36 is the same as that of the radiation measurement device 45B. The radiation measuring devices 45C and 40D have a part of the function of the gain adjusting device 36 in the radiation measuring device 45B.

  A radiation measurement method according to embodiment 4, which is another embodiment of the present invention, will be described with reference to FIG.

  First, the radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measuring apparatus 45E of the present embodiment has a configuration in which the signal processing apparatus 17 is replaced with the signal processing apparatus 17E in the radiation measuring apparatus 45 of the first embodiment. Other configurations of the radiation measuring apparatus 45E are the same as those of the radiation measuring apparatus 45. The signal processing device 17E has a configuration in which a coincidence counter 37 is added to the signal processing device 17. Other configurations of the signal processing device 17E are the same as those of the signal processing device 17. A coincidence counter 37 is connected to the multichannel wave height analyzer 10 and the display device 11.

  In the radiation measurement method of the present embodiment, a pair of cascade γ-rays 13 having different energies radiated from the measurement target nuclide 12 attached to the measurement region 21 on the inner surface of the primary cooling system pipe 18 are separately separated from the radiation detector 1A. , 1B. The γ-ray detection signals A and B respectively output from these detectors are processed by a high-level wave height discriminator, a delay circuit and a linear gate in the same manner as the signal processing device 17 used in the first embodiment, and are added amplifiers. 8 is input. The addition signal generated by the addition amplifier is input to the multichannel wave height analyzer 10 through the linear amplifier 9. The multichannel wave height analyzer 10 outputs a count value of the addition signal corresponding to the energy of the addition signal. These count values are input to the coincidence counter 37 and the display device 11. The coincidence counter 37 obtains a count value for the total energy of the energy of a pair of cascade γ rays radiated for each measurement target nuclide 12 using the input count value corresponding to the energy of each addition signal. As described above, the coincidence counter 37 can simultaneously count a pair of cascade γ rays emitted from the various types of measurement objects 12.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Furthermore, since the present embodiment is provided with the coincidence counter 37, it is possible to easily know the same clock value of a pair of cascade γ-rays radiated from the various types of measurement objects 12.

  The coincidence counter 37 may be connected to the linear amplifier 9 instead of the multichannel wave height analyzer 10. The coincidence counter 37 counts, among the addition signals output from the linear amplifier 9, the addition signal having the total energy of a pair of cascade γ rays having different energies emitted from the measurement target nuclide. Thereby, simultaneous counting of the pair of cascade γ rays can be performed.

  A radiation measurement method according to embodiment 5, which is another embodiment of the present invention, will be described with reference to FIG.

  First, the radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measurement apparatus 45G of this embodiment includes radiation detection apparatuses 16C and 16D, a signal processing apparatus 17G, and a display apparatus 11. Furthermore, the radiation measurement apparatus 45G includes high-voltage power supplies 2A, 2B, 40A, and 40B.

  The radiation detection device 16C has a configuration in which a Compton suppression detector 39A and a preamplifier 41A are added to the radiation detection device 16A. The other configuration of the radiation detection device 16C is the same as that of the radiation detection device 16A. A Compton suppression detector 39A is connected to the preamplifier 41A and the high voltage power source 40A. The Compton suppression detector 39A surrounds the radiation detector 1A. The radiation detection device 16D has a configuration in which a Compton suppression detector 39B and a preamplifier 41B are added to the radiation detection device 16B. Other configurations of the radiation detection device 16D are the same as those of the radiation detection device 16D. A Compton suppression detector 39B is connected to the preamplifier 41B and the high voltage power supply 40B. The Compton suppression detector 39B surrounds the radiation detector 1B.

The Compton suppression detectors 39A and 39B use scintillation radiation detectors (or semiconductor radiation detectors), which are general radiation detectors, similarly to the radiation detectors 1A and 1B. As a scintillation radiation detector, scintillation radiation using any of NaI (Tl), CsI (Ce), LaCl ₃ (Ce), LaBr ₃ (Ce), BGO, GSO (Ce), LuAG (Pr), etc. It is a detector. The semiconductor radiation detector is a semiconductor radiation detector using Si, Ge, CdTe, CZT, or the like.

  The signal processing device 17G has a configuration in which, in the signal processing device 17, the linear gates 7A and 7B are replaced with linear gates 43A and 43B, and delay circuits 42A and 42B are added. Other configurations of the signal processing device 17G are the same as those of the signal processing device 17. Delay circuit 42A is connected to preamplifier 41A and linear gate 43A. The linear gate 43A is connected to the high level wave height discriminator 5A, the delay circuit 6A, and the summing amplifier 8. Delay circuit 42B is connected to preamplifier 41B and linear gate 43B. The linear gate 43B is connected to the high level wave height discriminator 5B, the delay circuit 6B, and the summing amplifier 8. The signal selection device in this embodiment includes a high level wave height discriminator 5A, a delay circuit 6A, a delay circuit (third delay device) 42A, a linear gate (third gate device) 43A, a high level wave height discriminator 5B, and a delay circuit 6B. , A delay circuit (fourth delay device) 42B and a linear gate (fourth gate device) 43B are included.

  A radiation measurement method according to this embodiment will be described. The radiation detectors 1A and 1B and the Compton suppression detectors 39A and 39B are disposed, for example, in the vicinity of the primary piping 18 of the boiling water nuclear power plant. The radiation detectors 1A and 1B face the measurement region 21 of the primary system pipe 18. During operation of the boiling water nuclear power plant, each γ-ray radiated from the primary system pipe 18 is detected by the radiation detectors 1A and 1B. One of a pair of cascade γ rays 13 of different energies radiated from a measurement target nuclide (for example, Co-60) adhering to the inner surface of the primary system pipe 18 in the measurement region 21 is detected by the radiation detector 1A. It is assumed that the other cascade γ-ray 13 is detected by the radiation detector 1B.

The γ-ray detection signal A output from the radiation detector 1A is input to the high level wave height discriminator 5A and the delay circuit 6A. Similarly to the signal processing device 17 used in the first embodiment, the high level wave height discriminator 5A linearly converts the first gate opening signal when the energy of the input γ-ray detection signal A is equal to or less than the removal setting energy 27. Output to the gate 43A. The high level wave height discriminator 5A does not output the first gate open signal to the linear gate 43A when the energy of the input γ-ray detection signal A is larger than the removal setting energy 27. Delay circuit 6A, the entered γ ray detection signals, likewise, only the set time T ₁ is a time required for the output of the first gate opening signal of a high level pulse height discriminator 5A is delayed as in Example 1 Linear gate Output to 43A.

The Compton suppression detector 39A detects γ-rays incident on the radiation detector 1A and Compton scattered by the radiation detector 1A. The Compton suppression detector 39A that detects Compton scattered γ rays outputs a γ ray detection signal A3. delay circuits have entered the γ ray detection signal A3 42A is delayed by the set time T ₅ the γ ray detection signal A3 and outputs the linear gate 43A. Set time T _5, the time required until the radiation detector 1A is detected and output by γ ray detection signals A and γ-rays are inputted to the linear gate 43A, the γ-rays are Compton scattered in the radiation detector 1A Thus, the time required for the γ-ray detection signal A3 output from the Compton suppression detector 39A to be input to the linear gate 43A when detected by the Compton suppression detector 39A is set to be the same.

  The linear gate 43A inputs the γ-ray detection signal A from the delay circuit 6A at substantially the same time as the input time of the first gate opening signal output from the high level wave height discriminator 5A, and from the delay circuit 42 at that time. When the γ-ray detection signal A3 is not input, the γ-ray detection signal A input from the delay circuit 6A is output to the summing amplifier 8. The linear gate 43A does not output the γ-ray detection signal A from the delay circuit 6A when the γ-ray detection signal A3 is input from the delay circuit 42A.

  The γ-ray detection signal B output from the radiation detector 1B is input to the high level wave height discriminator 5B and the delay circuit 6B. Similarly to the signal processing device 17 used in the first embodiment, the high level wave height discriminator 5B outputs the second gate opening signal to the linear gate 43B when the energy of the γ-ray detection signal B is equal to or less than the removal setting energy 27. Output to.

The Compton suppression detector 39B detects γ-rays incident on the radiation detector 1B and Compton scattered by the radiation detector 1B. The Compton suppression detector 39B that detects the Compton-scattered γ-ray outputs a γ-ray detection signal B3. delay circuits have entered the γ ray detection signal B3 42B is delayed by the set time T ₆ the γ ray detection signal B3 for output to the linear gate 43B. Set time T _6, the time required until the radiation detector 1B is detected and output by γ ray detection signals B and γ-rays are inputted to the linear gate 43B, the γ-rays are Compton scattered in the radiation detector 1B Thus, the time required for the γ-ray detection signal AB output from the Compton suppression detector 39B to be input to the linear gate 43B when detected by the Compton suppression detector 39B is set to be the same. Set time _{T 5} and the set time _{T 6} is the same.

  The linear gate 43B inputs the γ-ray detection signal B from the delay circuit 6B at substantially the same time as the input time of the second gate opening signal output from the high level wave height discriminator 5B, and from the delay circuit 42B at that time. When the γ-ray detection signal B3 is not input, the γ-ray detection signal B input from the delay circuit 6B is output to the addition amplifier 8. The linear gate 43B does not output the γ-ray detection signal B from the delay circuit 6B when the γ-ray detection signal B3 is input from the delay circuit 42B.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Furthermore, since the present embodiment includes Compton suppression detectors 39A and 39B, the γ-rays Compton scattered by the radiation detectors 1A and 1B can be detected by the Compton suppression detectors 39A and 39B. When γ rays scattered by Compton are detected by the Compton suppression detectors 39A and 39B, the γ ray detection signals A and B output from the delay circuits 6A and 6B are added to the summing amplifier 8 by the functions of the linear gates 43A and 43B. Is not entered. For this reason, counting of the Compton distribution 23 caused by the background γ rays 15 of the interfering radionuclide 14 can be suppressed. Therefore, it is possible to suppress the coincidence coincidence due to detection of γ-rays having energy in the vicinity of the cascade γ-rays 13 caused by Compton scattering of the background γ-rays 15. The accuracy of the simultaneous coefficient of cascade γ rays in this embodiment can be further improved.

  The radiation measuring device 45G may be changed like the radiation measuring device 45H shown in FIG. The radiation measuring device 45H has a configuration in which the signal processing device 17G is replaced with a signal processing device 17H in the radiation measuring device 45G. The other configuration of the radiation measuring apparatus 45H is the same as that of the radiation measuring apparatus 45G.

  The signal processing device 17H has a configuration in which wave height discriminators 46A and 46B are added to the signal processing device 17G. Other configurations of the signal processing device 17H are the same as those of the signal processing device 17G. A wave height discriminator 46A is connected to the preamplifier 41A and the delay circuit 42A. A wave height discriminator 46B is connected to the preamplifier 41B and the delay circuit 42B.

The pulse height discriminator 46A has an energy larger than the high setting energy (or energy larger than the high setting energy and energy lower than the high setting energy in the γ-ray detection signal A3 input from the preamplifier 41A and less than the low setting energy. Γ-ray detection signal A3 having any energy) is removed, and γ-ray detection signal A3 having energy equal to or lower than the high setting energy (or energy between the high setting energy and the low setting energy) is supplied to delay circuit 42A. Output. The wave height discriminator 46B delays only the γ-ray detection signal B3 having energy lower than or equal to the high setting energy (or energy between the high setting energy and the low setting energy) in the γ-ray detection signal B3 input from the preamplifier 41B. Output to the circuit 42B. Each component other than the wave height discriminators 46A and 46B in the signal processing device 17H functions in the same manner as those in the signal processing device 17G. However, the set times T ₅ and T ₆ of the delay circuits 42A and 42B are shorter than the set times T ₅ and T ₆ of the radiation measuring device 45G by the time required for processing by the wave height discriminators 46A and 46B.

  The radiation measuring device 45H can obtain each effect produced by the radiation measuring device 45G. Furthermore, the radiation measuring device 45H removes the output caused by the braking X-ray generated by the metal that may be installed around the radiation detectors 1A and 1B by installing the wave height discriminators 46A and 46B. It becomes possible to remove energy gamma rays.

  A radiation measurement method according to embodiment 6, which is another embodiment of the present invention, will be described with reference to FIG.

  The radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measurement apparatus 45I of the present embodiment has a configuration in which the signal processing device 17 is replaced with the signal processing device 17I in the radiation measurement device 45 of the first embodiment. Other configurations of the radiation measuring apparatus 45I are the same as those of the radiation measuring apparatus 45.

  The signal processing device 17I is a DSP device 48 in which the signal processing device 17 is configured by a digital signal processor (DSP). The DSP device 48 performs digital processing of the γ-ray detection signals A and B output from the preamplifiers 3A and 3B. Such a DSP device 48 includes output branching devices 4A and 4B, high-level wave height discriminators 5A and 5B, delay circuits 6A and 6B, linear gates 7A and 7B, and an addition amplifier provided in the signal processing device 17 that performs analog processing. 8. Each of the processing functions of the linear amplifier 9 and the multichannel wave height analyzer 10 is provided.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Furthermore, in this embodiment, since digital processing is executed by the signal processing device 17I, it is possible to perform cascade γ-ray coincidence counting at higher speed and higher accuracy than in the first embodiment.

  A radiation measurement method according to embodiment 7, which is another embodiment of the present invention, will be described with reference to FIG.

  The radiation measuring apparatus used for the radiation measuring method of a present Example is demonstrated using FIG. The radiation measurement apparatus 45J according to the present embodiment has a configuration in which the radiation detection apparatus 16E is added to the radiation measurement apparatus 45 according to the first embodiment, and the signal processing apparatus 17 is replaced with the signal processing apparatus 17J. Other configurations of the radiation measuring apparatus 45J are the same as those of the radiation measuring apparatus 45.

  The radiation detection device 16E includes a radiation detector 1C and a preamplifier 3C connected to the radiation detector 1C. A high voltage power source 2C is connected to the radiation detector 1C. The signal processing device 17J has a configuration in which an output branching device 4C, a high level wave height discriminator 5C, a delay circuit 6C, and a linear gate 7C are added to the signal processing device 17. Other configurations of the signal processing device 17J are the same as those of the signal processing device 17.

  The output branching device 4C connected to the preamplifier 3C is connected to the high level wave high discriminator 5C and the delay circuit 6C. A linear gate 7C is connected to the high level wave height discriminator 5C, the delay circuit 6C and the summing amplifier 8.

  The radiation detectors 1 </ b> A, 1 </ b> B, and 1 </ b> C are arranged toward the measurement region 21 of the primary system pipe 18. Each gamma ray radiated | emitted from the measurement area | region 21 of the primary system piping 18 is detected by radiation detector 1A, 1B, 1C. The output branching device 4C, the high level wave height discriminator 5C, the delay circuit 6C, and the linear gate 7C function in the same manner as the output branching device 4A, the high level wave height discriminator 5A, the delay circuit 6A, and the linear gate 7A.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Furthermore, in this embodiment, the number of processing systems (output branching device, high level wave height discriminator, delay circuit and linear gate) of the radiation detection device and the signal processing device is increased as compared with the first embodiment. The detection efficiency of the cascade γ rays 13 in the measuring device 45J is improved, and the coincidence peak 29 can be measured in a short time.

  Each embodiment described above is a radiation measurement method applied to the primary piping of a boiling water nuclear plant, but other nuclear plants such as a pressurized water nuclear plant and a fast breeder reactor plant, and a nuclear fuel reprocessing facility, etc. It can be applied to radiation measurement in nuclear fuel material handling facilities.

  The present invention can be applied to radiation instrumentation in nuclear fuel material handling facilities such as nuclear power plants and nuclear fuel reprocessing facilities.

  1A, 1B, 1C ... Radiation detector, 2A, 2B, 2C, 40A, 40B ... High voltage power supply, 4A, 4B, 4C ... Output branching device, 5A, 5B, 5C ... High level wave high discriminator, 6A, 6B, 6C , 42A, 42B ... delay circuit, 7A, 7B, 7C, 43A, 43B ... linear gate, 8 ... summing amplifier, 10 ... multichannel wave height analyzer, 17, 17A-17E, 17G-17J ... signal processing device, 35 ... Thermometer 36 ... Gain adjusting device 37 ... Simultaneous counting counter 39A, 39B ... Compton suppression detector 45, 45A-45E, 45G-45J ... Radiation measuring device 48 ... DSP device.

Claims (19)

Cascade gamma rays with different energies radiated from the measurement target nuclide are detected by the first radiation detector and the second radiation detector, respectively.
Energy that is smaller than the total energy of the cascade γ-rays radiated from the measurement target nuclide and simultaneously counted, and larger than the largest energy among the energy of the cascade γ-rays radiated from the measurement target nuclide A first γ-ray detection signal output from the first radiation detector having energy equal to or lower than a first set energy set in a range of the second radiation detector having energy equal to or lower than the first set energy. The second γ-ray detection signal output from is added to generate an addition signal,
The radiation measurement method, wherein the sum signal having the total energy of the cascade γ-rays having different energy radiated from the measurement target nuclide is counted. The first γ-ray detection signal output from the first radiation detector is input to a first gate signal generator and a first delay device, respectively.
When the energy of the input first γ-ray detection signal is larger than the first set energy, the first gate signal generator does not output the first gate open signal and the input first γ-ray detection Outputting the first gate opening signal when the energy of the signal is equal to or lower than the first set energy;
The first delay device receives the input first γ-ray detection signal, and only the time required for the first gate signal generator to output the first gate open signal after the first γ-ray detection signal is input. Output with delay,
When the first gate device receives the first gate open signal from the first gate signal generator, the first gamma ray detection signal input from the first delay device is output to the adder,
The second γ-ray detection signal output from the second radiation detector is input to a second gate signal generator and a second delay device, respectively.
When the energy of the input second γ-ray detection signal is larger than the first set energy, the second gate signal generator does not output the second gate open signal and the input second γ-ray detection Outputting the second gate open signal when the energy of the signal is equal to or lower than the first set energy;
The second delay device inputs the input second γ-ray detection signal, and only the time required for the second gate signal generation device to output the second gate open signal after the second γ-ray detection signal is input. Output with delay,
When the second gate device receives the second gate open signal from the second gate signal generator, the second gamma ray detection signal input from the second delay device is output to the adder,
The generation of the addition signal is performed by the addition device that receives the first γ-ray detection signal output from the first gate device and the second γ-ray detection signal output from the second gate device. The radiation measurement method described.   The first γ-ray detection signal having an energy between the second set energy and the first set energy, which is smaller than the lower limit energy of the total absorption peak region of the measurement target nuclide, The radiation measurement method according to claim 1, wherein the radiation measurement method is performed by adding the second γ-ray detection signal having energy between the second set energy and the first set energy. The second set energy and the first set energy of the first gamma ray detection signal input to the first gate signal generator are lower than the lower limit energy of the total absorption peak region of the measurement target nuclide. The first gate opening signal is output from the first gate signal generator when the energy is between
When the energy of the second γ-ray detection signal input to the second gate signal generator is between the second set energy and the first set energy, the second gate open signal is the second gate. The radiation measurement method according to claim 2, wherein the radiation measurement method is output from a signal generator.   The temperature of the region where the first and second radiation detectors are arranged is measured with a thermometer, and the voltage applied to the first radiation detector from the first power source and the first are measured based on the temperature measured with the thermometer. The radiation measurement according to claim 2 or 4, wherein at least one of a voltage applied to the second radiation detector from two power sources and a gain of the adding device is controlled based on a temperature measured by the thermometer. Method. Cascade gamma rays with different energies radiated from the measurement target nuclide are detected by the first radiation detector and the second radiation detector, respectively.
The third radiation detector outputs a third γ-ray detection signal when detecting the γ-rays that are Compton scattered in the first radiation detector, and the fourth radiation detector is Compton scattered in the second radiation detector. When a γ ray is detected, a fourth γ ray detection signal is output,
When the third radiation detector does not output the third γ-ray detection signal and the fourth radiation detector does not output the fourth γ-ray detection signal, the coincidence radiated from the measurement target nuclide is counted. The energy is smaller than the total energy of the cascade γ-rays and has an energy equal to or lower than a first set energy set in an energy range larger than the largest energy among the energy of the cascade γ-rays radiated from the measurement target nuclide. The addition signal is obtained by adding the first γ-ray detection signal output from the first radiation detector and the second γ-ray detection signal output from the second radiation detector having energy equal to or lower than the first set energy. Generate
The radiation measurement method, wherein the sum signal having the total energy of the cascade γ-rays having different energy radiated from the measurement target nuclide is counted. The first γ-ray detection signal output from the first radiation detector is input to a first gate signal generator and a first delay device, respectively.
When the energy of the input first γ-ray detection signal is larger than the first set energy, the first gate signal generator does not output the first gate open signal and the input first γ-ray detection When the energy of the signal is equal to or lower than the first set energy, the first gate open signal is output;
The first delay device receives the input first γ-ray detection signal, and only the time required for the first gate signal generator to output the first gate open signal after the first γ-ray detection signal is input. Output with delay,
The third γ-ray detection signal output from the third radiation detector is input to a third delay device,
When the first delay device outputs the input first γ-ray detection signal, the third delay device outputs the input third γ-ray detection signal,
When the first gate device receives the first gate open signal from the first gate signal generator when the third γ-ray detection signal is not output from the third delay device, the first gate device receives an input from the first delay device. Output the first γ-ray detection signal to the adder,
The second γ-ray detection signal output from the second radiation detector is input to a second gate signal generator and a second delay device, respectively.
When the energy of the input second γ-ray detection signal is larger than the first set energy, the second gate signal generator does not output the second gate open signal and inputs the second γ-ray detection. When the signal energy is equal to or lower than the first set energy, the second gate open signal is output,
The second delay device inputs the input second γ-ray detection signal, and only the time required for the second gate signal generation device to output the second gate open signal after the second γ-ray detection signal is input. Output with delay,
The fourth γ-ray detection signal output from the fourth radiation detector is input to a fourth delay device,
When the second delay device outputs the input second γ-ray detection signal, the fourth delay device outputs the input fourth γ-ray detection signal,
When the second gate device receives the second gate open signal from the second gate signal generator when the fourth γ-ray detection signal is not output from the fourth delay device, the second gate device receives an input from the second delay device. Output the second γ-ray detection signal to the adder,
The generation of the addition signal is performed by the addition device that receives the first γ-ray detection signal output from the first gate device and the second γ-ray detection signal output from the second gate device. The radiation measurement method described.   The first γ-ray detection signal having the energy between the second set energy and the first set energy, which are lower than the lower limit energy of the total absorption peak region of the measurement target nuclide, The radiation measurement method according to claim 6, wherein the radiation measurement method is performed by adding the second γ-ray detection signal having energy between the second set energy and the first set energy. The second set energy and the first set energy of the first gamma ray detection signal input to the first gate signal generator are lower than the lower limit energy of the total absorption peak region of the measurement target nuclide. The first gate opening signal is output from the first gate signal generator when the energy is between
When the energy of the second γ-ray detection signal input to the second gate signal generator is between the second set energy and the first set energy, the second gate open signal is the second gate. The radiation measurement method according to claim 7, which is output from a signal generator. A first radiation detector and a second radiation detector that detect cascade γ-rays of different energies emitted from the measurement target nuclide,
The energy is smaller than the total energy of the cascade γ-rays radiated from the measurement target nuclide and larger than the largest energy among the energies of the cascade γ-rays radiated from the measurement target nuclide. A first γ-ray detection signal output from the first radiation detector having an energy equal to or lower than a set first setting energy, and an output from the second radiation detector having an energy equal to or lower than the first setting energy. A signal selection device that outputs a second γ-ray detection signal and does not output the first γ-ray detection signal and the second γ-ray detection signal having an energy larger than the first set energy;
An adding device that generates an addition signal by adding the first γ-ray detection signal and the second γ-ray detection signal output from the signal selection device;
A radiation measuring apparatus, comprising: a counting device that counts the sum signal having the total energy of the cascade γ-rays output from the adding device and radiated from the measurement target nuclide. The signal selection device is
The first γ-ray detection signal output from the first radiation detector is input, and when the energy of the input first γ-ray detection signal is larger than the first set energy, a first gate open signal is output. A first gate signal generator that outputs the first gate open signal when the energy of the input first γ-ray detection signal is equal to or lower than the first set energy without output;
The first γ-ray detection signal input by the first gate signal generator is input, the first γ-ray detection signal is input, and the first γ-ray detection signal is input by the first gate signal generator after the first γ-ray detection signal is input. A first delay device that delays and outputs a time required to output a gate open signal;
A first gate device that outputs the first γ-ray detection signal input from the first delay device to the adder when the first γ-ray detection signal output from the first gate signal generator is input;
When the second γ-ray detection signal output from the second radiation detector is input, and the energy of the input second γ-ray detection signal is larger than the first set energy, a second gate opening signal is output. A second gate signal generation device that outputs the second gate open signal when the energy of the input second γ-ray detection signal is equal to or lower than the first set energy without output;
The second γ-ray detection signal input by the second gate signal generator is input, the second γ-ray detection signal is input, and the second γ-ray detection signal is input by the second gate signal generator after the second γ-ray detection signal is input. A second delay device that delays and outputs the time required to output the gate open signal;
A second gate device that outputs the second γ-ray detection signal input from the second delay device to the adder when the second gate open signal is input from the second gate signal generator;
The radiation measuring device according to claim 10 provided.   The first γ-ray detection signal having energy between the second set energy that is lower than the lower limit energy of the total absorption peak region of the measurement target nuclide and the first set energy, the second set energy, and the The radiation measurement apparatus according to claim 10, further comprising the signal selection device that outputs the second γ-ray detection signal having energy between first setting energy to the adding device.   When the energy of the input first γ-ray detection signal is between the second set energy and the first set energy, which is lower than the lower limit energy of the total absorption peak region of the measurement target nuclide, The energy of the first gate signal generation device that outputs a 1-gate open signal to the first gate device and the input 21st γ-ray detection signal is an energy between the second set energy and the first set energy. The radiation measurement apparatus according to claim 11, further comprising: the second gate signal generation device that outputs the second gate opening signal to the second gate device.   A thermometer for detecting the temperature of the region where the first and second radiation detectors are arranged, and a voltage applied to the first radiation detector from the first power source and the first based on the temperature measured by the thermometer 14. A control device that controls at least one of a voltage applied to the second radiation detector from two power sources and a gain of the adding device based on a temperature measured by the thermometer. The radiation measurement apparatus according to any one of the above. A first radiation detector and a second radiation detector that detect cascade γ-rays of different energies emitted from the measurement target nuclide,
A third radiation detector that detects Compton scattered γ-rays in the first radiation detector and outputs a third γ-ray detection signal;
A fourth radiation detector that detects the Compton-scattered γ-rays in the second radiation detector and outputs a fourth γ-ray detection signal;
When the third radiation detector does not output the third γ-ray detection signal and the fourth radiation detector does not output the fourth γ-ray detection signal, the simultaneous radiated from the measurement target nuclide is counted. The energy is smaller than the total energy of the cascade γ-rays and not more than the first set energy set in the energy range larger than the largest energy among the energy of the cascade γ-rays radiated from the measurement target nuclide. A signal selection device that outputs a first γ-ray detection signal output from the first radiation detector, and a second γ-ray detection signal output from the second radiation detector, having energy equal to or lower than the first set energy; ,
An adding device that generates an addition signal by adding the first γ-ray detection signal and the second γ-ray detection signal output from the signal selection device;
A radiation measuring apparatus, comprising: a counting device that counts the summed signal output from the adder and emitted from the measurement target nuclide and having the total energy of the cascade γ-rays having different energies. The signal selection device is
The first γ-ray detection signal output from the first radiation detector is input, and when the energy of the input first γ-ray detection signal is larger than the first set energy, a first gate open signal is output. A first gate signal generator that outputs the first gate open signal when the energy of the input first γ-ray detection signal is equal to or lower than the first set energy without output;
The first γ-ray detection signal input by the first gate signal generator is input, the first γ-ray detection signal is input, and the first γ-ray detection signal is input by the first gate signal generator after the first γ-ray detection signal is input. A first delay device that delays and outputs a time required to output a gate open signal;
The third γ-ray detection signal output from the third radiation detector is input, and the third γ-ray detection signal is output when the first γ-ray detection signal input by the first delay device is output. A third delay device;
The first γ-ray detection input from the first delay device when the first gate open signal is input from the first gate signal generator when the third γ-ray detection signal is not output from the third delay device. A first gate device for outputting a signal to the adder;
When the second γ-ray detection signal output from the second radiation detector is input, and the energy of the input second γ-ray detection signal is larger than the first set energy, a second gate opening signal is output. A second gate signal generation device that outputs the second gate open signal when the energy of the input second γ-ray detection signal is equal to or lower than the first set energy without output;
The second γ-ray detection signal input by the second gate signal generator is input, the second γ-ray detection signal is input, and the second γ-ray detection signal is input by the second gate signal generator after the second γ-ray detection signal is input. A second delay device that delays and outputs the time required to output the gate open signal;
The fourth γ-ray detection signal output from the fourth radiation detector is input, and the fourth γ-ray detection signal is output when the second γ-ray detection signal input by the second delay device is output. A fourth delay device;
The second γ-ray detection input from the second delay device when the fourth gate detection signal is not output from the fourth delay device and the second gate open signal is input from the second gate signal generator. A second gate device for outputting a signal to the adding device;
The radiation measuring device according to claim 15 provided.   The first γ-ray detection signal having energy between the second set energy that is lower than the lower limit energy of the total absorption peak region of the measurement target nuclide and the first set energy, the second set energy, and the The radiation measurement apparatus according to claim 15, further comprising the signal selection device that outputs the second γ-ray detection signal having energy between first setting energy to the adding device.   When the energy of the input first γ-ray detection signal is between the second set energy and the first set energy, which is lower than the lower limit energy of the total absorption peak region of the measurement target nuclide, The energy of the first gate signal generation device that outputs a 1-gate open signal to the first gate device and the input 21st γ-ray detection signal is an energy between the second set energy and the first set energy. The radiation measurement apparatus according to claim 16, further comprising: the second gate signal generation device that outputs the second gate opening signal to the second gate device.   A third wave height discriminating device for outputting the third γ-ray detection signal output from the third radiation detector to the third delay device, wherein the signal selection device has an energy equal to or lower than a third set energy; and The fourth wave height discriminating device that outputs the fourth γ-ray detection signal output from the fourth radiation detector, having energy equal to or lower than three set energy, to the fourth delay device. Radiation measurement device.

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