JP2015141158A - Radiation measuring apparatus, apparatus for identifying whether fuel debris is present and measuring position of fuel debris using the same, and method of determining whether fuel debris is present and measuring position of fuel debris - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate a gamma-ray sum peak of interference nuclides from a gamma-ray peak of a measuring target nuclide, and to identify whether a fuel debris is present and the position of the fuel debris in a nuclear reactor plant.SOLUTION: A radiation measuring apparatus comprises: a radiation detector 1 for detecting a radiation; a gamma-ray energy analyzer 3; a display device 4 for displaying a gamma-ray energy distribution; a collimator 91 for limiting a viewing angle of the radiation incident on the radiation detector 1; collimator drive means; and a shield body 25 for shielding the radiation detector 1. The collimator drive means moves the collimator 91 forward or backward with respect to the radiation detector 1 and the shield body 25, thereby making variable the viewing angle of the radiation incident on a radiation incident unit. The gamma-ray energy analyzer 3 finds a sum peak count value generated by the simultaneous incidence of a plurality of gamma-rays radiated from a plurality of radioactive nuclides other than the measuring target nuclide from a gamma-ray peak count value of the gamma-ray energy distribution, and calculates a gamma-ray peak count value of the measuring target nuclide from a difference between a gamma-ray peak count value of the measuring target nuclide obtained by the gamma-ray energy distribution and the sum peak count value.

Description

  The present invention relates to a radiation measuring apparatus capable of discriminating a γ-ray peak of a target nuclide obtained from a γ-ray energy distribution from a γ-ray peak of an interfering nuclide, presence / absence of fuel debris using the same, position measurement apparatus, and presence / absence of fuel debris And a position measuring method.

  In response to the accident at the Fukushima Daiichi NPS in March 2011, fuel debris detection technology that can be applied to reactor pressure vessels, reactor containment vessels, pressure suppression chambers, and torus chambers is required. It has been. As one method for estimating the presence or absence of fuel debris, there is a method of measuring specific radiation emitted from the fuel debris. Typical examples are Ce-144 and Eu-154. There are reports that fuel debris was investigated by measuring the gamma rays emitted from Ce-144 in the accident at Unit 3 in the US. However, Ce-144 has a short half-life (about 239 days), and it is unclear whether it is appropriate as a measurement target at this time. On the other hand, Eu-154 has a long half-life (about 8.6 years) and a relatively large content inside the fuel assembly, so it is a promising measurement target for estimating the presence or absence of fuel debris. In order to measure the gamma rays radiated from Eu-154, it is necessary to apply a radiation detector and analyzer capable of nuclide analysis. When Eu-154γ rays are measured at these nuclear reactor facilities, the interfering nuclides are Cs-137, Cs-134, Co-60, Co-58, etc. existing in the atmosphere. A 1274 keV γ-ray peak emitted from Eu-154 and a 1264 keV sum peak generated when energy is applied at the radiation detector almost simultaneously by a 662 keV γ-ray emitted from Cs-137 and a 602 keV γ-ray emitted from Cs-134. Discrimination is necessary. These interfering nuclides are present throughout the reactor facilities and are susceptible to interference levels. The radioactivity distribution of these interfering nuclides is complicated, and the radioactivity distribution and geometric conditions may change with time.

  In general environments such as laboratories, nuclide analysis using Ge semiconductor detectors with excellent energy resolution is possible, so it is possible to discriminate between Eu-154 and thumb peak of interfering nuclides. It is difficult to apply from the viewpoints of ease of use, maintainability, detectors including a refrigerator, and device size.

  Non-Patent Document 1 relates to γ-ray spectrometry using a Ge semiconductor detector, and describes a method for excluding interference peaks including thumb peaks. This calculates the contribution coefficient from the emission ratio of the γ-ray nuclide that generates the interference peak and the detection efficiency of the Ge semiconductor detector, and excludes the influence of the interference peak based on the contribution coefficient.

  Patent Document 1 sets a different coincidence gate time width in each of the two coincidence circuits, and eliminates the coincidence coincidence that occurs probabilistically by subtracting the same clock value obtained therefrom. is there.

Radioactivity measurement method series 7 Gamma-ray spectrometry using germanium semiconductor detector (revised in 1992): Ministry of Education, Culture, Sports, Science and Technology, Science and Technology Policy Bureau, Nuclear Safety Division, Disaster Prevention and Environment Office, pages 142-145

JP 2013-61206 A

  However, Non-Patent Document 1 is intended to calibrate a Ge semiconductor detector and is applied between a known radiation source and a Ge semiconductor detector disposed at a predetermined distance, and the radionuclide and geometric conditions are clear. It assumes a certain case.

  Therefore, it is difficult to apply in an environment where the radioactive distribution in which fuel debris exists and the geometric conditions are unknown.

  In Patent Document 1, the measurement object is a cascade γ-ray, and the γ-ray is counted by two or more radiation detectors and a coincidence counting circuit. The coincidence coincidence that occurs in this apparatus occurs when two different γ-rays enter the respective radiation detectors and are counted within a range that satisfies the coincidence gate time width.

  However, no consideration is given to reducing the sum peak generated when a plurality of γ rays radiated from a radionuclide (interfering nuclide) different from the measurement target nuclide are incident on one radiation detector almost simultaneously.

  The present invention relates to a radiation measuring apparatus capable of discriminating a γ-ray sum peak of interfering nuclides and a γ-ray peak of a target nuclide, and capable of estimating the presence / absence and position of fuel debris, a fuel debris presence / absence / position measuring apparatus, and a fuel The object is to provide a method for measuring the presence and position of debris.

A radiation measurement apparatus according to the present invention is a radiation measurement apparatus that is arranged in a nuclear reactor facility and estimates the presence and position of fuel debris by detecting a γ-ray peak of a measurement target nuclide,
A radiation detector for detecting radiation;
A γ-ray energy analyzer that processes a signal of radiation detected by the radiation detector;
A display device for displaying the γ-ray energy distribution obtained by the γ-ray energy analysis unit;
A collimator disposed in front of the radiation detector, having a path for the radiation, and limiting a viewing angle of radiation incident on the radiation detector;
Collimator driving means for driving the collimator;
A shield covering the radiation detector,
The collimator driving means makes the viewing angle of radiation incident on the radiation detector variable by moving the collimator back and forth with respect to the radiation detector and the shield,
The γ-ray energy analysis unit is configured to detect a plurality of γ-rays emitted from one radionuclide or a plurality of radionuclides different from a measurement target nuclide based on a γ-ray peak count value of the γ-ray energy distribution and a predetermined signal processing time. The sum peak count value generated by simultaneous incidence is obtained, and the γ-ray peak count value of the measurement target nuclide is calculated from the difference between the γ-ray peak count value of the measurement target nuclide obtained from the γ-ray energy distribution and the sum peak count value. It is characterized by that.

Another aspect of the present invention is a fuel debris presence / absence and position measuring device for estimating the presence / absence and position of fuel debris in a nuclear reactor facility,
The radiation measuring apparatus according to the present invention;
A moving device equipped with the radiation measuring device;
A rotating mechanism that rotates the radiation measuring device in a direction perpendicular to the floor;
A position recognition sensor for recognizing the position of the mobile device;
Position estimation means for estimating the position of the mobile device using information of the position recognition sensor;
The measurement position of the radiation measuring device is calculated from the position of the moving device estimated by the position estimating means, and the measurement data measured by the radiation measuring device is registered in the CAD data of the moving environment of the moving device from the calculation result. Radiation mapping means is provided.

Another aspect of the present invention is a method for measuring the presence and position of fuel debris for estimating the presence and position of fuel debris in a nuclear reactor facility,
A fuel debris presence / absence and position measuring device comprising the radiation measuring device according to the present invention, a moving device equipped with the radiation measuring device, and a rotating mechanism for rotating the radiation measuring device in a direction perpendicular to the floor surface. Driving to detect a gamma ray peak of the target nuclide,
Estimating the position of the mobile device using information of a position recognition sensor that performs position recognition of the mobile device;
Calculating the presence / absence of the fuel debris and the measurement position of the position measuring device from the estimated position of the moving device;
A step of registering the measurement data measured by the position measurement device and the presence / absence of the fuel debris in the CAD data of the movement environment of the moving device from the calculation result, and creating a radiation mapping.

  According to the present invention, a gamma ray sum peak of an interfering nuclide and a gamma ray peak of a measurement target nuclide can be discriminated, and a radiation measuring apparatus capable of estimating the presence / absence and position of fuel debris and the measurement of the presence / absence and position of fuel debris using the same. Apparatus and methods can be provided.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a conceptual diagram which shows an example of the reactor building in which the radiation measuring device which concerns on this invention is arrange | positioned. It is a block diagram which shows an example of the gamma ray energy analysis part which comprises the radiation measuring device which concerns on this invention. It is a figure which shows an example of the gamma ray energy distribution obtained in the gamma ray energy analysis part of the radiation measuring device which concerns on this invention. It is a relationship diagram of signal processing time, energy resolution, and sum peak count rate. The It is a top view which shows typically the radiation measuring device of Example 5. FIG. It is a figure which shows an example of the gamma ray energy distribution obtained in the gamma ray energy analysis part of the radiation measuring device of Example 5. It is a block diagram which shows typically the radiation measuring device of Example 6. FIG. It is a block diagram which shows typically the radiation measuring device of Example 7. FIG. It is a top view which shows typically the radiation measuring device of Example 1. FIG. It is a top view which shows the state which moved the collimator to the front surface in FIG. 9A. 6 is a plan view schematically showing another example of a radiation path of the collimator of Embodiment 1. FIG. It is a top view which shows typically the radiation measuring device of Example 2. FIG. It is a top view which shows the state which moved the collimator to the front surface in FIG. 10A. FIG. 10B is a plan view of the collimator of FIG. 10A. It is a top view which shows typically the radiation measuring device of Example 3. FIG. It is a top view which shows the state which moved the collimator to the front surface in FIG. 11A. It is a top view which shows typically another example of the radiation measuring device of Example 3. FIG. It is a top view which shows typically the radiation measuring device of Example 4. FIG. It is a top view which shows the state which moved the collimator to the front surface in FIG. 12A. It is a figure which shows typically an example of the presence or absence and position measuring apparatus of the fuel debris which concerns on this invention. It is the elements on larger scale of FIG. 13A. It is a figure which shows the procedure which produces the three-dimensional map of a radiation source. It is a system block diagram which creates the three-dimensional map of a radiation source.

  The present invention exists in large quantities in reactor facilities such as reactor pressure vessels, reactor containment vessels, pressure suppression chambers, torus chambers, etc., and the radioactivity distribution is complicated, and the radioactivity distribution changes with time. Measurement of γ-ray energy distribution, radiation measurement device that reduces the influence of thumb peak due to this interfering nuclide, presence / absence of fuel debris and position measurement device using radiation measurement device, and This is based on new knowledge obtained through various studies on the presence and location of fuel debris and its position.

  In this knowledge, by providing a radiation detector, a γ-ray energy analysis unit, and a display device, the γ-ray energy detected by the radiation detector is displayed in the form of a γ-ray energy distribution. Measurement obtained from the gamma ray energy distribution by obtaining the sum peak count value generated by the incidence of two gamma rays emitted from the interfering nuclides from the gamma ray peak count value of the gamma ray energy distribution and the signal processing time for processing the signal. By calculating the γ-ray peak net count value of the target nuclide based on the difference between the γ-ray peak count value and the sum peak count value of the target nuclide, the energy resolution for discriminating the monochromatic γ-ray peak of the target nuclide and the interfering nuclide is improved. While maintaining, it is possible to discriminate the γ-ray peak by the measurement target nuclide and the sum peak formed by the two γ-rays by the interfering nuclide, and calculate the γ-ray peak net count value of the measurement target nuclide. As a result, the presence or absence of fuel debris can be estimated with high accuracy in an environment where there is a large amount in the nuclear reactor facility and the radioactivity distribution is complicated and the radioactivity distribution and geometric conditions may change over time.

  Furthermore, in addition to the above-described configuration, the radiation measuring apparatus according to the present invention is disposed on the front surface of the radiation detector, has a radiation path, and restricts the incident direction of the radiation incident on the radiation detector; Collimator driving means for driving the collimator, and by moving the collimator back and forth with respect to the radiation detector by the collimator driving means, the viewing angle of the radiation incident on the radiation incident portion can be changed in a short time. The radiation can be measured accurately and the position of the fuel debris can be estimated.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a radiation measuring apparatus and method according to the invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing an example of a reactor building in which a radiation measuring apparatus according to the present invention is arranged. As shown in FIG. 1, the radiation measuring apparatus according to the present invention includes a radiation detector 1, an electric cable 2, a γ-ray energy analysis unit 3, and a display device 4. The application point is a general nuclear power plant. Here, it demonstrates using the conceptual diagram of a boiling water reactor as an example. The boiling water reactor is composed of a reactor building 5, a reactor containment vessel 6, a reactor pressure vessel 7, a reactor water recirculation system 8, a reactor pressure suppression chamber 9, a torus chamber 10, a penetration portion 11, and the like. . In order to confirm the presence or absence of fuel debris 12 in these facilities, the radiation detector 1 includes, for example, a reactor containment vessel 6, a reactor pressure vessel 7, a reactor pressure suppression chamber 9 as shown in FIG. The inside of the torus chamber 10 is accessed. When accessing, the existing penetration part 11 or an intrusion route constructed by construction or the like is used. The radiation detector 1 is connected to an electric cable 2. The electric cable 2 is connected to a γ-ray energy analysis unit 3 installed in the reactor building 5. The analysis result obtained by the γ-ray energy analysis unit 3 is displayed on the display device 4 through various cables. Here, although the γ-ray energy analysis unit 3 and the display device 4 are installed in the reactor building 5, they can be installed outside the reactor building 5.

  The present invention includes a configuration of an apparatus that estimates the presence / absence of fuel debris by discriminating a γ-ray sum peak of interfering nuclides and a γ-ray peak of a measurement target nuclide, and a configuration of an apparatus that estimates the position of fuel debris. The configuration of these two devices will be described in detail below.

(Estimation of fuel debris)
First, the configuration of an apparatus for estimating the presence / absence of fuel debris by discriminating the γ-ray sum peak of interfering nuclides from the γ-ray peak of the target nuclide will be described. The fuel debris 12 is composed of nuclear fuel U and Pu, fission products, and a molten in-core structure. It should be noted that the constituent ratio, shape, and geometric conditions of the elements of the fuel debris 12 are considered to vary depending on the location where the fuel debris 12 exists. In order to detect the presence or absence of the fuel debris 12, it is necessary to detect components contained in the fuel debris 12. Examples of components for detection include Ce-144 and Eu-154. For example, there is a report that the fuel debris 12 was investigated by measuring gamma rays radiated from Ce-144 in the accident on the United States Three Mile Island. However, Ce-144 has a short half-life (about 239 days), and it is unclear whether it is appropriate as a measurement target at this time. On the other hand, Eu-154 has a long half-life (about 8.6 years) and a relatively high content inside the fuel assembly. Therefore, in order to estimate the presence or absence of the fuel debris 12, that is, the occurrence and location of the fuel debris 12, it is considered effective to use Eu-154 as a measurement target.

  In this embodiment, a case where Eu-154 is a measurement target nuclide for estimating the presence / absence of the fuel debris 12 will be described below as an example. Here, Eu-154 has a characteristic of emitting γ-rays of 123 keV, 723 keV, 873 keV, 1004 keV, and 1274 keV.

In these facilities, fission products such as Cs-137 and Cs-134, and Co-60 and Co-58 generated by activation of reactor structures are present in the background. To do. Here, Cs-137 emits 662 keV gamma rays and has a characteristic of decaying with a half-life of about 30 years. Cs-134 emits gamma rays of 602 keV, 796 keV, 802 keV, and 1365 keV, and has a characteristic of decaying with a half-life of about 2 years. In addition, Co-60 emits 1173 keV and 1332 keV γ rays and has a characteristic of decaying with a half-life of about 5 years. Co-58 mainly emits gamma rays of 511 keV and 811 keV and has a characteristic of decaying with a half-life of about 70 days. In order to detect Eu-154 which is a measurement target in these background environments, it is necessary to apply the radiation detector 1 equipped with a sensor capable of nuclide analysis. The sensor applied here is CdTe, CZT, TlBr if it is a semiconductor detector, and LaBr ₃ (Ce), LaCl ₃ (Ce), LSO, LYSO, GAGG (Ce), LuAG if it is a scintillation detector. One of (Pr), NaI (Tl), YAP (Ce), and GSO is used. A gamma camera or a scintillation detector such as LaBr ₃ (Ce) can be used. The output signal of the radiation detector 1 on which any of these sensors is mounted is transmitted to the γ-ray energy analysis unit 3 at the subsequent stage via an electric cable 2 having high noise resistance such as a coaxial cable.

  FIG. 2 is a block diagram showing an example of a γ-ray energy analyzing unit constituting the radiation measuring apparatus according to the present invention, and FIG. 3 is a γ-ray energy obtained by the γ-ray energy analyzing unit of the radiation measuring apparatus according to the present invention. It is a figure which shows an example of distribution. As shown in FIG. 2, the γ-ray energy analyzer 3 shapes a waveform shaping amplifier 13 that shapes the output signal transmitted from the radiation detector 1 via the electric cable 2, and a pulse that extends the output signal of the waveform shaping amplifier 13. The stretcher 14, the analog-digital converter 15 for digitizing the output signal of the pulse stretcher 14, and the γ-ray energy distribution 17 formed from the digitized signal and transmitted to the display device 4 are transmitted. The processing unit 16 is configured. As shown in FIG. 3, the γ-ray energy distribution 17 has γ-ray energy on the horizontal axis and a count value on the vertical axis, and a γ-ray peak 18 can be observed from the γ-ray energy analysis 17. Line peak count values can be derived. Although FIG. 2 shows a case where the γ-ray energy analysis unit 3 includes the waveform shaping amplifier 13, the pulse stretcher 14, the analog-digital converter 15, and the processing unit 16, the present invention is not limited thereto. For example, the γ-ray energy analysis unit 3 may include an analog-digital converter 15 that digitizes an output signal transmitted from the radiation detector 1 via the electric cable 2 and a processing unit 16.

  The γ-ray energy analysis unit 3 has a signal processing time for processing this output signal. Here, the signal processing time is a time for processing one output signal, and means that other output signals input within this time are not counted. In general, the signal processing time of the γ-ray energy analysis unit 3 is determined by digitalizing the output signal of the preceding pulse stretcher 14 in the analog / digital converter 15 and reading the peak value or pulse integral value. Conversion time. When the digital conversion time is shortened, it is the waveform shaping time in the waveform shaping amplifier 13 that determines the signal processing time next. In the present embodiment, as an example, a processing method when the digital conversion time is sufficiently short and the waveform shaping time in the waveform shaping amplifier 13 is a factor for determining the signal processing time will be described.

  In order to measure Eu-154 as a measurement target nuclide, an algorithm for reducing the influence of Cs-137, Cs-134, Co-60, and Co-58 in the background is required. Here, there are many background nuclide peaks in the region below 1000 keV and the accompanying Compton distribution. Therefore, there is a concern about the degradation of the SN ratio in the γ-ray peak measurement in the region below 1000 keV. The In this embodiment, a case where a 1274 keV γ-ray peak is detected from the energy of γ-ray radiated from Eu-154 will be described as an example. The background when detecting the 1274 keV gamma-ray peak of Eu-154 is that the 1365 keV gamma-ray peak emitted by Cs-134, the 1332 keV gamma-ray peak emitted by Co-60, and the Cs-134 This is a 1264 keV sum peak composed of the sum of the energy of radiated 602 keV γ rays and the energy of 662 keV γ rays emitted by Cs-137. When a 602 keV γ-ray peak emitted by Cs-134, which is an isotope of Cs, and a 662 keV γ-ray peak emitted by Cs-137 are accidentally detected almost simultaneously by the radiation detector 1, 1264 keV The sum peak appears. Here, the sum peak formed by the γ-rays radiated from the background nuclide is formed from, for example, a 662 keV γ-ray peak emitted from Cs-137 and a 569 keV γ-ray peak emitted from Cs-134. 1231 keV sum peak, Cs-137 emits a 662 keV gamma ray peak and Cs-134 emits a 563 keV gamma ray peak, 1225 keV sum peak emitted by Cs-134, Cs-134 emits a 602 keV gamma ray peak and Cs A 1171 keV sum peak formed from a 569 keV gamma-ray peak emitted by -134, a 165 keV gamma-ray peak emitted by Cs-134 and a 563 keV gamma-ray peak emitted by Cs-134, a Cs-sum sum peak, Cs -96 keV emitted by -134 1271 keV sum peak formed from the 475 keV γ-ray peak emitted from the γ-ray peak and Cs-134, formed from the 802 keV γ-ray peak emitted from the Cs-134 and the 475 keV γ-ray peak emitted from Cs-134 There is a thumb peak at 1277 keV. In the embodiment of the present specification, a 264 keV gamma ray peak emitted from Cs-134 and a sum peak of 1264 keV formed from 662 keV emitted from Cs-137 will be described below as an example.

  In order to discriminate between the 1274 keV γ-ray peak of Eu-154, which is the target nuclide, and the 1365 keV γ-ray peak of Cs-134, which is the interfering nuclide, and 1332 keV γ-ray peak, of Co-60, the energy resolution of the radiation detector 1 Is preferably 5% or less. Here, the energy resolution of the radiation detector 1 is represented by a value obtained by dividing the half-value width obtained at the γ-ray peak 18 shown in FIG. 3 by the γ-ray energy to be measured. In this embodiment, the γ-ray peak 18 of the measurement object Eu-154 has an energy resolution of 5%, a half width of 63.7 keV (γ-ray energy 1274 keV), and γ of Cs-134 and Co-60 which are interfering nuclides. Since the half width of the line peak is about 70 keV, it is possible to discriminate these γ-ray peaks with an energy resolution of 5%. However, the sum peak of 1264 keV cannot be distinguished by the energy resolution of the sensor applied as the radiation detector 1, here 5%. For this reason, in order to enable peak discrimination of Eu-154 which is a measurement target nuclide, it is necessary to exclude the influence of this thumb peak. That is, an algorithm for calculating the sum peak count value is required. Furthermore, the disturbing nuclides that make up Sam Peak are present in large quantities in the nuclear reactor facility, and the radioactivity distribution is complex, and exists in an environment where the radioactivity distribution and geometric conditions change with time. In order to realize the calculation of the sum peak count value in these environments, the sum peak count rate Nsum is derived by the equation (1) in the present embodiment.

Nsum = N602 keV × N662 keV × ts (1)
Here, the peak count rate of the 602 keV γ-ray peak obtained by the γ-ray energy analysis unit 3 is N602 keV, the peak count rate of the 662 keV γ-ray peak is N662 keV, and the signal processing time of the γ-ray energy analysis unit 3 is ts. And Here, the signal processing time ts is a time for processing one output signal as described above, and is a waveform shaping time in the waveform shaping amplifier 13. Therefore, N602 keV and N662 keV are the peak count rate of the γ-ray peak of 602 keV and the peak count rate of the γ-ray peak of 662 keV at the signal processing time ts, respectively.

  By using this equation (1), it is possible to calculate the contribution of the thumb peak without considering the geometric condition of the radiation detector 1 and the radiation source, the emissivity of γ rays, and the Becquerel number. When the sum peak count value is derived, it is derived by multiplying the measurement time tm by the sum peak count rate Nsum. Note that the measurement time tm is appropriately set to a desired time such as 10 sec, 1 min, 1 hr.

  Based on this calculation result, the γ-ray peak count value of the measurement object (Eu-154) is calculated. When this is the γ-ray peak net count rate Nnet, Nnet is derived by equation (2).

Nnet = Ngross-Nsum (2)
Here, the peak count rate of the 1274 keV γ-ray peak obtained by the γ-ray energy analysis unit 3 is Ngross. In order to derive the peak count value of the 1274 keV γ-ray peak, the measurement time tm is derived by multiplying the γ-ray peak net count rate Nnet.

  The processing unit 16 constituting the γ-ray energy analysis unit 3 includes a processor such as a CPU (not shown) and various storage units for storing various programs executed by the processor and data. The algorithm for deriving the γ-ray peak net count rate Nnet according to equations (1) and (2) is stored as a program in this storage unit.

  The γ-ray energy analysis unit 3 integrates output signals input from the radiation detector 1 through the electric cable 2 for the measurement time tm, and obtains Ngross × tm as the peak count value of the γ-ray peak 18 shown in FIG. . The processing unit 16 calculates the γ-ray peak net count rate Nnet of Eu-154, which is the measurement target nuclide, from the measured peak count value (Ngross × tm) and the equations (1) and (2) stored in the storage unit. Is calculated.

  FIG. 4 shows the relationship between signal processing time, energy resolution, and sum peak count rate. Here, the signal processing time 19 is a waveform shaping time in the waveform shaping amplifier 13. If the waveform shaping time is shortened, the energy resolution 20 tends to deteriorate because the time for processing the information included in the output signal of the radiation detector 1 is shortened. Further, the sum peak count rate 21 tends to decrease as the signal processing time 19 is shorter, as shown by the equation (1). That is, the energy resolution 20 is inversely proportional to the signal processing time 19, and the thumb peak count rate 21 is proportional to the signal processing time 19. In addition, the energy resolution setting region 22 for discriminating between the 1274 keV γ-ray peak of Eu-154 and the 1365 keV of Cs-134 and the 1332 keV γ-ray peak of Co-60 is temporarily maintained as 5% or less as described above. Suppose. In this case, as shown in FIG. 4, the signal processing time setting area 23 is set between 0.05 μs and 10 μs. However, depending on the sensor applied to the radiation detector 1, the lower limit value 0.05 μs of the signal processing time setting area 23 may exceed the upper limit value 5% of the energy resolution setting area 22. In this case, the signal processing time setting area 23 is set within a range that satisfies the upper limit value 5% of the energy resolution setting area 22.

  In FIG. 4, the sum peak count rate 21 is the sum peak count value per unit time, and the sum peak is caused by the fact that a plurality of γ-rays are accidentally detected by the radiation detector 1 as described above. is there. Therefore, the sum peak count rate 21 which is the occurrence probability is proportional to the signal processing time, and the sum peak count rate 21 of the interfering nuclides has a relationship proportional to the signal processing time in any radionuclide. In the present embodiment, the sum peak due to two γ rays emitted from Cs-134 and Cs-137, which are Cs isotopes, has been described as an example. However, the sum peak includes a plurality of γ rays emitted from different radionuclides. When the radiation is detected simultaneously by the radiation detector 1, the same phenomenon occurs when a plurality of γ rays emitted from the same radionuclide existing at different locations are detected simultaneously by the radiation detector 1. The thumb peak is not limited to two γ rays, and the same applies when a plurality of γ rays are simultaneously detected by the radiation detector 1.

  Although the calculation of Nsum by the γ-ray energy analysis unit 3 is performed by the equation (1) stored in the storage unit, the sum peak count rate 21 is signal processing regardless of the type of interfering nuclides as described above. Since it is proportional to time, the graph shown in FIG. 4 may be stored in the storage unit as a function. In this case, the waveform shaping time of the waveform shaping amplifier 13 constituting the γ-ray energy analysis unit 3 corresponds to the signal processing time ts in the equation (1), and Nsum can be uniquely obtained from the waveform shaping time and this function. it can.

  In FIG. 4, the upper limit value of the energy resolution related to the setting of the signal processing time is 5%. However, the upper limit value is not limited to this, and may be 7% or 8%, for example.

  The radiation measuring apparatus according to the present embodiment includes a radiation detector 1, an electric cable 2, a γ-ray energy analysis unit 3, and a display device 4. In the γ-ray energy analysis unit 3, the γ obtained by the γ-ray energy analysis unit 3 is provided. Using the formulas (1) and (2) from the peak count value of the line peak 18 and the signal processing time 19 and the peak count value of the γ-ray peak to be measured (Ngloss × tm), the γ-ray peak net count rate of the measurement target (Nnet) is derived.

  According to the present embodiment, the thumb peak of the interfering nuclide can be discriminated from the gamma ray peak of the measurement target nuclide. As a result, it exists in large quantities in nuclear reactor facilities such as the reactor containment vessel 6, the reactor pressure vessel 7, the reactor pressure suppression chamber 9, the torus chamber 10, and the like, and its radioactivity distribution is complicated, and the radioactivity changes over time. It is possible to estimate the presence or absence of fuel debris in an environment where the distribution and geometric conditions may change.

(Estimation of fuel debris position)
Next, the configuration of an apparatus that accurately estimates the position of fuel debris in a short time will be described.

  FIG. 9A is a plan view schematically showing the radiation measuring apparatus according to the first embodiment, and FIG. 9B is a plan view showing a state in which the collimator 91 is moved to the front surface (radiation incident side) in FIG. 9A. As shown in FIG. 9A, the radiation measuring apparatus according to the present invention is disposed on the radiation detector 1, the shield 25 covering the radiation detector 1, the front surface of the radiation detector (radiation incident side), and the radiation path. A collimator 91 for limiting the viewing angle (incident direction) of the radiation incident on the radiation detector, and the collimator 91 with respect to the radiation detector 1 to control the collimator 91 and the viewing angle 95a of the radiation detector 1 Collimator driving mechanisms 92a and 92b, a γ-ray energy analyzing unit 3, a display device 4, and an electric cable 2 are provided as collimator driving means for moving back and forth (relative to the radiation detector 1 and the shield 25). The radiation detector 1, the shield 25, the collimator 91, and the collimator driving mechanisms 92a and 92b are referred to as a radiation measurement head 90.

As the radiation detector 1, a semiconductor detector such as a gamma camera or CdTe, or a LaBr ₃ (Ce) scintillation detector can be used. The shield 25 blocks radiation from outside the field of view to the radiation detector 1. The shield 25 is preferably made of lead.

  The collimator 91 is disposed in front of the radiation detector 1, has a hollow cylindrical radiation passage 96, shields radiation from outside the field of view into the radiation detector 1, and enters the radiation detector 1. Limit the viewing angle (incident direction) of radiation (γ rays). As a material of the collimator 91, a material that becomes a radiation shield such as tungsten or lead is suitable.

  The collimator driving mechanisms 92a and 92b move the collimator 91 back and forth with respect to the radiation detector 1 and the shield 25, thereby making the viewing angle 95a of the radiation incident on the radiation detector 1 variable. The collimator driving mechanisms 92a and 92b are not particularly limited, but a linear motion mechanism such as a ball screw is preferable. At this time, the position of the collimator 91 with respect to the radiation detector 1 is transmitted to the γ-ray energy analyzer 6 by a position sensor such as an encoder (not shown) attached to a motor (not shown). The radiation measured by the radiation detector 1 is converted into an electrical signal, transmitted to the γ-ray energy analysis unit 6, and formed into a histogram with a predetermined energy width. This histogram-formed energy spectrum is transmitted to the display device 7 and displayed. Here, the γ-ray energy analysis unit 6 uses the configuration according to the present invention described above. Needless to say, the configuration of the display device 7 varies depending on the type of the radiation detector 1.

  FIG. 9B is a diagram illustrating a state in which the collimator is moved to the front surface in FIG. 9A. By separating the distance between the collimator 91 and the radiation detector 1, the viewing angle changes from 95a to the viewing angle 95b, and the viewing angle of the radiation incident on the radiation detector 1 is limited. At this time, care must be taken to configure the shield 25 and the collimator 91 so that radiation incident from outside the field of view does not interfere with the measurement. Initially, as shown in FIG. 9A, measurement is performed in a state where the viewing angle 95a is wider (in a state where the radiation measurement range is wider), and when the target radiation is not detected, the measurement is moved to another measurement range and becomes the target. When radiation is detected, measurement is performed in a range where the viewing angle 95b is narrower as shown in FIG. Thus, as a first step of measurement, it is possible to reduce the number of measurements until detection of the radiation to be measured by performing detection of the radiation to be measured in a wider range. Measurement time is shortened. Furthermore, as a second step of measurement, narrowing the viewing angle can improve the estimation accuracy of the positions of the radiation source and fuel debris.

  FIG. 9C is a plan view schematically illustrating another example of the radiation path of the collimator according to the first embodiment. The path of the radiation is not limited to the hollow cylindrical shape as shown in FIG. 9A. For example, as shown in FIG. 9C, the diameter of the path monotonously decreases along the direction in which the radiation enters the radiation detector. It may have a hollow truncated cone shape. Since the passage 96 shown in FIG. 9A has more shield parts (portions other than the passage 96) of the collimator 91, the effect of shielding the radiation incident from outside the field of view is further enhanced. As a result, detection with higher sensitivity can be achieved. It can be carried out. On the other hand, the passage 96 ′ shown in FIG. 9C has fewer shield parts (portions other than the passage 96 ′) that constitute the collimator 91 ′, so that the collimator 91 ′ can be further reduced in weight. Therefore, it is preferable that the shape of the radiation path is appropriately selected according to the purpose such as the high sensitivity detection and the weight reduction of the collimator. The shape of the radiation passage of the collimator is not limited to that described above, and may be any shape as long as it is a radiation passage.

  10A is a plan view schematically showing the radiation measuring apparatus according to the second embodiment, and FIG. 10B is a plan view showing a state in which the collimator is moved to the front in FIG. 10A. The radiation measurement head 90 ″ shown in FIGS. 10A and 10B is obtained by changing the shape of the collimator 91 in the configuration of the radiation measurement head 90 in FIG. 9A described above. In this embodiment, the collimator radiation path 96 ″ includes a first path portion 100 and a second path portion 101 in order from the radiation incident side along the direction in which the radiation enters the radiation detector. Is done. The first passage portion 100 has a hollow frustoconical shape in which the diameter of the passage monotonously decreases along the direction in which the radiation enters the radiation detector. The second passage portion 101 has a hollow cylindrical shape. With such a shape, the difference between the viewing angles 95a and 95b can be made larger (the viewing angle 95a can be made larger than that of the embodiment 1), and the number of measurements can be further reduced. Overall measurement time is also reduced.

Next, preferable dimensions of the first passage portion 100 and the second passage portion 101 will be described. FIG. 10C is a plan view of the collimator of FIG. 10A. Here, the relational expression of each dimension shown in FIG. 10C is as follows.
L1 = t1 / tanα (5)
t3 = t2- (t2-t1) / 2 (6)
α = atan (t3 / L0) (7)
Therefore, the effective viewing angle α is naturally determined when the dimensions of t1, t2, and L0 are determined, and the length (L1) of the second passage portion 101 is determined. The first passage portion 100 (L0) is preferably determined in consideration of the size of the collimator, the weight of the collimator, and the like.

  FIG. 11A is a plan view schematically illustrating the radiation measuring apparatus according to the third embodiment, and FIG. 11B is a plan view illustrating a state in which the collimator is moved to the front surface in FIG. 11A. The radiation measurement head 90 ″ shown in FIG. 11A and FIG. 11B changes the structure of the collimator and the shield (the structure of the gap between the collimator and the shield) in the configuration of the radiation measurement head 90 ″ of FIG. 10A described above. FIG. In the present embodiment, the collimator 91 ″ ″ includes the body portion 104 and the first flange portion 102 provided at the end portion of the body portion 104 on the radiation detector side and protruding toward the shield 25 ′. Have. Further, the shield 25 ′ is provided at the end on the radiation incident side, and has a second flange portion 103 that protrudes toward the trunk portion 104 (when seen from the upper surface, the trunk portion 104 and the first flange are provided). The ridgeline of the part 102 has a crank shape). By adopting such a configuration, radiation outside the viewing angle that has entered from between the body portion 104 and the second flange portion 103 is attenuated between the body portion 104 and the shield 25 ′. The influence of radiation incident from outside the corner can be reduced, and the measurement accuracy can be improved. As a result, the radiation measurement accuracy and the estimation accuracy of the positions of the radiation source and the fuel debris can be improved. Further, when the collimator 91 ″ ″ is moved to the front surface, the first flange portion 102 and the second flange portion 103 serve as stoppers and are not completely detached from the shield 25 ′.

  FIG. 11C is a plan view schematically illustrating another example of the radiation measuring apparatus according to the third embodiment. As shown in FIG. 11C, it is needless to say that the shape of the collimator and the shape of the shield described above can also be applied when the radiation path has a hollow cylindrical shape.

  FIG. 12A is a plan view schematically showing an example of the radiation measuring apparatus according to the fourth embodiment, and FIG. 12B is a plan view showing a state where the collimator is moved to the front surface in FIG. 12A. The radiation measurement head 90 '' '' '' shown in FIGS. 12A and 12B has a shape in which the collimator 91 '' '' '' covers the shield 25 '' in the configuration of the radiation measurement head 90 of FIG. 9A described above. It is a thing.

  FIG. 5 is a block diagram schematically showing an example of a radiation measuring apparatus according to the present invention. In the present embodiment, a shutter shield 26 that closes the radiation path is provided on the radiation incident side of the collimator 91 of the radiation measuring apparatus described with reference to FIG. 9A, and the background is reduced by opening and closing the shutter. Is. The γ-ray energy analysis unit 3 shown in FIG. 5 is the same as that in the first embodiment.

  As shown in FIG. 5, the radiation measuring apparatus further includes a shutter shield 26 and shutter shield driving means (a drive device 27 that drives the shutter shield 26 and a control device 28 that controls the drive device 27). Have. The installation location of the shutter shield driving unit is not limited to the mode illustrated in FIG. 5, and may be provided in the collimator 91 or may be provided in the shield 25.

  FIG. 6 is a diagram illustrating an example of the γ-ray energy distribution obtained by the γ-ray energy analysis unit of the radiation measuring apparatus according to the fifth embodiment, and illustrates an example of the γ-ray energy distribution by turning the shutter on / off. In FIG. 6, the γ-ray energy distribution indicated by the dotted line 29 indicates a distribution obtained when the shutter mechanism is turned on, that is, when the driving shield 27 drives the shutter shield 26 to limit the incident γ dose. Further, the γ-ray energy distribution indicated by the solid line 30 indicates a distribution obtained when the shutter mechanism is turned off. Since the shielding effect is enhanced by applying the shutter, the count value of the γ-ray peak as in the γ-ray energy distribution 29 is reduced as compared with the γ-ray energy distribution 30 obtained under the shutter-off condition. From the γ-ray energy distribution obtained under these conditions, the γ-ray peak net count rate of the measurement object obtained under each condition is defined as Nneton and Nnetoff. This is derived from the equations (1) and (2) described in the first embodiment. The attenuation rate of the γ-ray to be measured by the shutter shield is D1. From this, the γ-ray peak net count rate Ns in consideration of the presence or absence of the shielding effect is derived by Equation (3).

Ns = Nneton / D1 (3)
Specifically, the γ-ray energy analyzing unit 3 constituting the radiation measuring apparatus integrates the output signal input from the radiation detector 1 via the electric cable 2 for the measurement time tm under the condition of the shutter “on”, and performs measurement. Ngrossoff × tm is obtained as the peak count value of the target γ-ray peak. Thereafter, as in the first embodiment, the sum peak count rate Nsum is obtained from, for example, the waveform shaping time ts according to the equation (1) stored in the storage unit (not shown) in the γ-ray energy analysis unit 3, and the equation (2) is obtained. Nneton is calculated by executing the calculation. Ns is derived by processing this Nneton according to Equation (3) using D1 prepared in the database of the γ-ray energy analysis unit in advance.

  There is also a method of deriving the γ-ray peak net count rate Ns by taking into account the presence or absence of the shielding effect and calculating the formula (4) by counting the count rates according to shutter on / off.

Ns = (Ngrossoff−Ngrosson) − (N602 keVoff × N662 keVoff × ts) (4)
Here, the peak count rate of the 1274 keV γ-ray peak obtained when the shutter is turned off is defined as Ngrossoff. The peak count rate of the 602 keV γ-ray peak is N602 keVoff, and the peak count rate of the 662 keV γ-ray peak is N662 keVoff. Further, the γ-ray energy analyzing unit 3 constituting the radiation measuring apparatus integrates the output signal input from the radiation detector 1 through the electric cable 2 for the measurement time tm under the shutter-off condition, and the γ of the measurement target Ngrossoff × tm is obtained as the peak count value of the line peak. Thereafter, the shutter shield 26 is driven by the driving device 27, and data is collected under the condition of shutter turning as described above. The derivation method using Equation (4) is effective for effectively removing the background component when the γ-ray energy of the measurement target is sufficiently attenuated due to the shielding effect of the shutter shield and cannot be derived as a peak. is there. As in the first embodiment, the γ-ray peak net count rate Ns is calculated in the storage unit of the processing unit 16 in the γ-ray energy analysis unit 3 in consideration of the shielding effect according to the equations (3) and (4). Algorithms are stored as programs, and these derivation algorithms can be arbitrarily selected.

  As described above, in this example, by obtaining the γ-ray peak net count rate Ns of the measurement target nuclide, compared with the above-described embodiment, the back indicated by the hatched portion in the γ-ray peak 18 shown in FIG. The influence of the ground component can be reduced.

  In this embodiment, Ns is calculated by measuring two cycles. However, the present invention is not limited to this, and the measurement time under the shutter-on condition is set to be shorter than the measurement time under the shutter-off condition. May be.

  As described above, in this embodiment, the collimator 91, the shielding body 25, the shutter shielding body 26, the drive mechanism 27, and the control device 28 are provided, and the presence / absence of the shielding effect is determined from the γ-ray measurement values obtained under the shutter on / off conditions. The γ-ray peak net count rate for the measurement target nuclide is derived.

  According to the present example, in addition to the effects of the above-described embodiment, the background component can be reduced in the detection of the γ-ray peak by the measurement target nuclide, and highly accurate radiation measurement can be performed. Furthermore, by adding the collimator driving mechanisms 92a and 92b to the present embodiment, the measurement time can be shortened and the debris estimation accuracy can be improved.

  FIG. 7 is a configuration diagram schematically showing another example of the radiation measuring apparatus according to the present invention. In FIG. 7, the same components as those in the first embodiment are denoted by the same reference numerals. In the present embodiment, the radiation detector 1 constituting the radiation measuring apparatus is mounted on the moving mechanism, and it is possible to estimate the presence or absence of the fuel debris 12 in a section that is difficult for an operator to access. And different.

  As shown in FIG. 7, a moving mechanism 31 on which the radiation detector 1 is mounted, and a moving mechanism control device 32 that can remotely control the moving mechanism 31 are provided. The moving mechanism 31 is an amphibious moving mechanism that includes a land moving mechanism such as a crawler or a wheel and an underwater moving mechanism such as a thruster. The moving mechanism control device 32 is installed in a relatively low dose rate environment outside the reactor building or inside the reactor building, and the radiation detector 1 mounted on the moving mechanism 31 in response to an instruction input from an operator. Move to a desired position in a narrow space, underwater or in a high dose rate environment.

  The γ-ray energy analyzing unit 3 and the display device 4 constituting the radiation measuring apparatus shown in FIG. 7 are placed in the environment at a relatively low dose rate outside the reactor building or inside the reactor building, like the movement mechanism control device 32. Installed.

  After positioning the radiation detector 1 by the moving mechanism control device 32 to a section or the like that is difficult to be accessed by a worker, the γ-ray peak net count rate Nnet to be measured or the γ-ray peak net count rate Ns considering the shielding effect is calculated. The processing unit 16 in the γ-ray energy analysis unit 3 calculates the same as in Example 1 and Example 2, respectively.

  According to the present embodiment, in addition to the effects of the first embodiment, it is possible to estimate the presence or absence of fuel debris with high accuracy in sections where workers are difficult to enter, such as in water, at a high dose rate, or in narrow spaces.

  FIG. 8 shows a configuration diagram of a radiation measuring apparatus according to another embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In this embodiment, in addition to the radiation detector shown in the first embodiment, a neutron detector is connected in parallel, and the γ-ray peak measurement of the measurement object and the neutron generated by the spontaneous fission are respectively measured. This improves the accuracy of estimation.

  As shown in FIG. 8, the neutron detector 33 and the neutron analysis unit 35, the radiation detector 1 and the γ-ray energy analysis unit 3 are connected in parallel to the processing unit 36, and the processing result by the processing unit 36 is displayed from the display device 4. It constitutes a radiation measurement device. The neutron detector 33 detects neutrons generated by spontaneous fission such as U, Pu, and Cm contained in the fuel debris 12. The output signal of the neutron detector 33 is transmitted to the neutron analysis unit 35 via the electric cable 34, and the neutron analysis unit 35 derives the count rate by neutrons. The processing unit 36 processes the count rate by neutrons and the count rate of Eu-154γ rays that are measurement targets, and displays the result on the display device 4. When the counting rate by neutron is detected with these configurations, it can be said that there is a possibility that the fuel debris 12 exists in the measurement region. Further, when the count rate by Eu-154 as a measurement target is measured, there is a possibility that the fuel debris 12 exists with high accuracy.

  As the neutron detector 33, for example, a semiconductor detector, a gas detector, or a scintillation detector is used.

  The calculation of the Eu-154 γ-ray peak net count rate Nnet by the γ-ray energy analysis unit 3 is performed in the same manner as in the first embodiment. Further, the radiation detector 1 may be housed in the shield 25, provided with a collimator and a shutter mechanism, and the γ-ray peak net count rate Ns considering the shielding effect may be calculated in the same manner as in the fifth embodiment. .

  According to the present embodiment, by collecting the counting rate of γ-rays and neutrons of the measurement target nuclide, suppose that the γ-rays of the measurement target nuclide are not detected and only the neutrons are detected, or neutrons are detected. Even in the situation where only the γ-ray of the measurement nuclide is detected, the presence or absence of fuel debris can be estimated.

  Further, as described above, it is possible to estimate the presence / absence of fuel debris from the count rate by neutrons, and further improve the estimation accuracy of the presence / absence of fuel debris from the count rate by γ-rays of the measured nuclides.

  In this example, an embodiment in which the above-described radiation measuring device according to the present invention is mounted on a moving device and fuel debris is detected is taken as an example of a torus chamber on the basement floor of a reactor building, and FIGS. It explains using. FIG. 13A is a diagram schematically illustrating an example of the presence / absence of fuel debris and position measurement apparatus according to the present invention, and FIG. 13B is a partially enlarged view of FIG. 13A. In FIG. 13A, the torus chamber 130 is submerged by about half, the suppression chamber 131 is also almost full, and the fuel debris 12 is present at a plurality of locations on the floor surface of the torus chamber 130 and in the suppression chamber 131. The fuel debris 12 is detected by the presence / absence of fuel debris and the position measurement device 140 (hereinafter referred to as the fuel debris detection device 140). The fuel debris detection device 140 has a configuration in which the radiation measurement device according to the present invention described above is mounted, and the radiation measurement head 141 is mounted on the moving device 143 in combination with the rotation mechanism unit 142. Each drive unit (not shown) of the rotation mechanism unit 142 and the moving device 143 is driven by receiving a command by a control device (not shown). At least one camera (not shown) is mounted on the moving device 143 in front of the device, and an operation is performed based on the video. Similarly to the above-described embodiment, the debris 12 is also measured in the state where the viewing angle is wide (95a) first, and when a thing that seems to be fuel debris 12 is detected, the state where the viewing angle is narrowed (95b) ) To measure.

  FIG. 14 is a diagram showing a procedure for creating a three-dimensional map of the radiation source, and FIG. 15 is a system block diagram for creating a three-dimensional map of the radiation source. Hereinafter, the specific presence / absence of the fuel debris 12 and the position estimation procedure will be described with reference to FIGS. 14 and 15. The fuel debris detection device 140 is mounted with a group of position sensors (not shown) such as a gyro sensor, an inclinometer, and sonar. When the fuel debris detection device 140 is thrown into the torus chamber, the distance from the front, rear, left and right wall surfaces is measured by sonar at the thrown position, and the direction is determined from the gyro sensor. The initial position data input means 150 sends the sonar and gyro sensor position data stored in the position sensor group data storage unit 31 to the mobile device position estimation unit 32, and the CAD data reading unit receives the CAD data in the CAD data storage unit 33. The data is read and sent to the mobile device estimation unit 32. In the mobile device position estimation unit 32, the position data of the position sensor group is read into the CAD data, and the estimated position of the debris detection device 20 is displayed on the CAD data.

  At this time, the virtual image of the camera mounted on the estimated fuel debris detection device 140 in the CAD data is displayed on the virtual image display unit 35 at the same time. The feature amount extracted from this image and the feature amount extracted from the camera image mounted on the fuel debris detection device 140 are subjected to image processing in the moving device position correcting unit 37, an error is calculated, and the result is calculated as the moving device position estimating unit 32. And the position of the fuel debris detection device 140 is updated.

  When performing fuel debris detection, the position sensor group data reading means 151 stores sonar, gyroscope, and camera image data in the position sensor data storage unit 31 at the measurement position. Next, in the self-position estimation unit 152, the mobile device estimation unit 32 updates the self-position of the debris detection device 20 in the same manner as in the initial position estimation.

  Next, in the radiation measurement position estimation means 153, position sensor data (not shown) of the rotation mechanism unit 11 and position sensor data of the collimator driving mechanisms 92a and 92b are read by the radiation measurement position estimation unit, and the viewing angle and measurement of the radiation detector 1 are measured. Calculate the range. Finally, the radiation data registration unit 154 checks the radiation source mapping unit with the structure in the measurement range existing in the CAD data, and considers the attenuation of the radiation from the distance from the radiation detector 1 and the density of each structure. Then, the debris position and strength when debris is present on the structure are estimated. Here, if the camera is attached to the rotation mechanism unit 142 in order to measure the measurement range of the radiation measurement head 90, the debris position and intensity can be easily estimated.

  By repeating the above measurement and accumulating data, the position identification accuracy of the fuel debris can be efficiently improved with a smaller number of measurements.

  In the present specification, Eu-154 has been described as an example of a measurement target nuclide, but is not limited to this. The presence or absence of fuel debris is estimated based on a counting rate using γ rays with another radionuclide as a measurement target nuclide. It may be configured.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace the configurations of other embodiments with respect to a part of the configurations of the embodiments.

  DESCRIPTION OF SYMBOLS 1 ... Radiation detector, 2,34 ... Electric cable, 3 ... Gamma ray energy analysis part, 4 ... Display apparatus, 5 ... Reactor building, 6,133 ... Reactor containment vessel, 7 ... Reactor pressure vessel, 8 ... Reactor water recirculation system, 9 ... Reactor pressure suppression chamber, 10 ... Torus chamber, 11 ... Penetration part, 12 ... Fuel debris, 13 ... Waveform shaping amplifier, 14 ... Pulse stretcher, 15 ... Analog-digital converter, 16 , 36 ... processing unit, 17, 29, 30 ... gamma ray energy distribution, 18 ... gamma ray peak, 19 ... signal processing time, 20 ... energy resolution, 21 ... sum peak count rate, 22 ... energy resolution setting region, 23 ... signal Processing time setting area, 25, 25 '... shield, 26 ... shutter shield, 27 ... drive device, 28 ... control device, 31 ... movement mechanism, 32 ... control device for movement mechanism, 33 ... neutron detector, 3 ... Neutron analysis section, 90, 90 ', 90 ", 90" ", 90" ", 90" "", 141 ... Radiation measurement head, 91, 91 ", 91", 91 " ′, 91 ″ ″, 91 ″ ″ ″ ... Collimator, 92a, 92b ... Collimator driving mechanism, 95a, 95b ... Viewing angle, 96, 96 ', 96 "... Radiation passageway, 100 ... First Passage portion, 101 ... second passage portion, 102 ... first flange portion, 103 ... second flange portion, 104 ... body portion, 130 ... torus chamber, 131 ... suppression chamber, 132 ... vent pipe, 140 ... fuel Debris presence / absence and position measuring device, 142... Rotating mechanism, 143.

Claims (11)

A radiation measurement device that is disposed in a nuclear reactor facility and detects the presence and position of fuel debris by detecting a γ-ray peak of a target nuclide,
A radiation detector for detecting radiation;
A γ-ray energy analyzer that processes a signal of radiation detected by the radiation detector;
A display device for displaying the γ-ray energy distribution obtained by the γ-ray energy analysis unit;
A collimator disposed in front of the radiation detector, having a path for the radiation, and limiting a viewing angle of radiation incident on the radiation detector;
Collimator driving means for driving the collimator;
A shield covering the radiation detector,
The collimator driving means makes the viewing angle of radiation incident on the radiation detector variable by moving the collimator back and forth with respect to the radiation detector and the shield,
The γ-ray energy analysis unit is configured to detect a plurality of γ-rays emitted from one radionuclide or a plurality of radionuclides different from a measurement target nuclide based on a γ-ray peak count value of the γ-ray energy distribution and a predetermined signal processing time. The sum peak count value generated by simultaneous incidence is obtained, and the γ-ray peak count value of the measurement target nuclide is calculated from the difference between the γ-ray peak count value of the measurement target nuclide obtained from the γ-ray energy distribution and the sum peak count value. A radiation measuring apparatus characterized by that.   The radiation measurement apparatus according to claim 1, wherein the radiation passage has a hollow cylindrical shape. The path of radiation is
A first passage portion and a second passage portion provided in order from the radiation incident side along the direction in which the radiation enters the radiation detector,
The first passage portion has a hollow truncated cone shape in which the diameter of the passage monotonously decreases along the direction in which the radiation enters the radiation detector.
The radiation measurement apparatus according to claim 1, wherein the second passage portion has a hollow cylindrical shape.   The radiation measurement apparatus according to claim 1, wherein the radiation path has a hollow truncated cone shape in which a diameter of the path monotonously decreases along a direction in which the radiation enters the radiation detector. The collimator includes a body part, and a first flange part provided at an end part of the body part on the radiation detector side and projecting toward the shield,
The said shielding body is provided in the edge part of the incident side of the said radiation, and has a 2nd flange part which protrudes toward the said trunk | drum, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Radiation measurement equipment.   The radiation measuring apparatus according to claim 1, wherein the collimator has a shape that covers the shield. The collimator has a shutter shield for closing the radiation path on the radiation incident side of the radiation path,
The radiation measuring apparatus according to claim 1, further comprising a shutter shield driving unit that drives the shutter shield.   The γ-ray energy analysis unit calculates a γ-ray peak count value of the measurement target nuclide when the shutter shield is on and off, and calculates a difference between the calculated coefficient values of the measurement target nuclide γ. The radiation measuring apparatus according to claim 7, wherein a line peak count value is used. A fuel debris presence / absence and position measuring device for estimating the presence / absence and position of fuel debris in a nuclear reactor facility,
The radiation measurement apparatus according to any one of claims 1 to 8,
A moving device equipped with the radiation measuring device;
A rotating mechanism that rotates the radiation measuring device in a direction perpendicular to the floor;
A position recognition sensor for recognizing the position of the mobile device;
Position estimation means for estimating the position of the mobile device using information of the position recognition sensor;
The measurement position of the radiation measuring device is calculated from the position of the moving device estimated by the position estimating means, and the measurement data measured by the radiation measuring device is registered in the CAD data of the moving environment of the moving device from the calculation result. A fuel debris presence / absence and position measuring device comprising a radiation mapping means. A method for measuring the presence and position of fuel debris to estimate the presence and position of fuel debris in a nuclear reactor facility,
9. A fuel comprising: the radiation measuring apparatus according to claim 1; a moving device including the radiation measuring apparatus; and a rotation mechanism unit that rotates the radiation measuring apparatus in a direction perpendicular to the floor surface. Detecting the presence or absence of debris and detecting the γ-ray peak of the target nuclide by driving the position measuring device;
Estimating the position of the mobile device using information of a position recognition sensor that performs position recognition of the mobile device;
Calculating the presence / absence of the fuel debris and the measurement position of the position measuring device from the estimated position of the moving device;
The presence or absence of fuel debris and the measurement data measured by the position measurement device are registered in the CAD data of the movement environment of the mobile device from the calculation result, and the step of creating radiation mapping is included. And position measuring method. The step of detecting the γ-ray peak of the measurement target nuclide is performed by bringing the collimator closest to the radiation detector and detecting the γ-ray peak of the measurement target nuclide with the largest viewing angle. Change the measurement position by driving the presence / absence and position measurement device,
11. The gamma ray peak of the measurement target nuclide is detected by moving the collimator to the front at a measurement position where the gamma ray peak of the measurement target nuclide is detected and reducing the viewing angle. The presence / absence and position measuring method of fuel debris described in 1.

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