JP2005326301A - Reactor power measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactor power measuring apparatus which suppresses an increase in wiring number and simultaneously simplifies the constitution. <P>SOLUTION: The apparatus comprises a case 3 placed in the core 13 of the reactor as extension along the axis of the reactor, an ion chamber 1 for detecting γ rays arranged by dispersing in the position different from the extension direction of the case 3 in the case 3, and a calculation means 9 for calculating the power of the reactor from the variation of electric quantity caused by the ionization of the γ rays in the ion chamber 1 for γ-ray detection. The calculation means 9 is so constituted as to transmit signal commanding protection operation of the reactor according to the information of the calculated reactor power. In this manner, TIP detector and a plurality of temperature detectors substituting the TIP detectors become unnecessary, and the increase of the number of wiring is suppressed and simultaneously constitution of reactor power measuring arrangement can be simplified. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reactor power measuring device that is installed in a nuclear reactor and detects the power of the reactor.

  In nuclear power plants, the heat output is taken out by the fission reaction by the fuel placed in the core part in the reactor pressure vessel, but when the output fluctuates and rises for some reason, the output that can ensure the soundness of the fuel Before exceeding the level, it is necessary to perform protective actions such as shutting down the reactor safely. For this reason, a reactor power measuring device is provided in the core of a nuclear reactor or the like to measure the output of the reactor and to perform a protective operation such as stopping the reactor according to the measured output. .

  A conventional reactor power measurement device includes a plurality of LPRM assemblies each housing a plurality of local power range monitor (hereinafter abbreviated as LPRM) detectors composed of neutron detectors. Yes. A plurality of LPRM detectors included in the LPRM assembly are arranged in the cylinder so as to be dispersed in the extending direction of the cylinder. A plurality of LPRM assemblies having such a structure are evenly arranged in the core in a state in which the cylindrical body extends along the axial direction of the reactor in the reactor pressure vessel.

  The LPRM assembly has a double-pipe structure in which an inner cylinder is inserted along the axial direction of the reactor inside the cylinder, and a single traveling in-core instrument (Traveling Incore Probe) is formed in the inner cylinder. System (hereinafter abbreviated as TIP) detector moves. That is, the LPRM detectors arranged along the axial direction of the nuclear reactor and the inner cylinder in which the TIP detector moves are provided in parallel in the cylindrical body, and the TIP detector is arranged in the axial direction of the nuclear reactor. It moves along the axial direction of the reactor in parallel with the LPRM detectors lined up along the line.

  Each LPRM detector is electrically connected to an average output range monitor (hereinafter referred to as “APRM”) unit via a separately provided wiring. In the LPRM detector, neutrons collide with the fission material applied to the LPRM detector, and an ionization current signal is generated by the collision ionization action between the fission fragments generated by the fission and the purge gas in the detector. In the APRM unit, the ionization current signal generated in each LPRM detector, that is, the signal from each LPRM detector included in each LPRM assembly evenly arranged in the reactor core is averaged to obtain each LPRM detector. The signal from is converted into output information of the entire reactor. The APRM unit monitors the reactor output with the averaged signal, and if an abnormality occurs in the reactor and the reactor output exceeds a preset value, a control rod operation monitoring system or reactor Sends a signal to command the protection operation of the reactor to an emergency shutdown system.

Here, the LPRM detector applies ²³⁵ U and ²³⁴ U as a fission material to the electrode inside the LPRM detector in order to detect the neutron flux generated in proportion to the nuclear fission in the nuclear reactor fuel, and the LPRM detection. The neutron flux is output as an ionization current signal by utilizing the ionization action of the gas in the LPRM detector when the neutron that has entered the chamber is absorbed by ²³⁵ U and causes fission. ^{234 U,} in order to suppress the decrease in sensitivity caused by the combustion of ^{235 U,} by reproducing the ²³⁵ U by reaction of ²³⁴ U and neutrons, which extends the life of LPRM detectors. However, in LPRM detectors composed of such neutron detectors, the sensitivity decreases corresponding to the neutron irradiation amount, so periodic calibration is required to accurately measure the reactor output. It becomes.

TIP detectors are used to calibrate the sensitivity of such LPRM detectors. The TIP detector is composed of a neutron detector having the same configuration as the LPRM detector coated with ²³⁵ U and ²³⁴ U, but moves in the inner cylinder along the axial direction of the reactor by a driving mechanism. Further, the TIP detector is pulled out from the inner cylinder by a driving mechanism except when the TIP detector is used, and is in a standby position outside the furnace where neutrons are not irradiated. Thereby, in the TIP detector, a decrease in sensitivity due to neutron irradiation is suppressed. When performing calibration, the TIP detector is inserted into the inner cylinder of the LPRM assembly from the standby position by the drive mechanism, and travels in the inner cylinder at a plurality of positions along the axial direction of the reactor. Output ionization current signal corresponding to neutron flux. Then, based on the ionization current signal output at each position by the TIP detector, a value to be indicated by the LPRM detector is calculated, and based on the calculated value to be indicated and the indication value of the current LPRM detector. By obtaining and correcting the calibration gain of the LPRM detector, the decrease in sensitivity of the LPRM detector is compensated.

  As described above, in the conventional reactor power measuring device, since the TIP detector that moves in the inner cylinder is provided, the configuration of the device is complicated by the drive mechanism of the TIP detector, and maintenance work, etc. Problems such as increased complexity and cost.

  On the other hand, a reactor output measuring apparatus having a configuration in which a plurality of detectors arranged in the axial direction of the reactor are provided instead of the TIP detector moving in the inner cylinder without using the TIP detector moving in the inner cylinder. Has been proposed (see, for example, Patent Documents 1-5).

  In these reactor power measuring devices, a plurality of LPRM detectors arranged in parallel to the LPRM detector in the axial direction of the reactor are disposed in a cylinder constituting an LPRM assembly in which the LPRM detectors are arranged in the axial direction of the reactor. A temperature detector is provided, and the temperature in the core correlated with γ rays is detected by the temperature detector to calculate the γ dose, and the reactor output is measured from the calculated γ dose. Therefore, based on the value of the reactor power calculated based on the temperature detected by the temperature detector at each position, the value to be indicated by the LPRM detector is calculated, and the calculated value to be indicated and the current LPRM are calculated. The sensitivity of the LPRM detector can be calibrated by obtaining the calibration gain of the LPRM detector based on the indicated value of the detector.

JP-A-6-289182 (page 3-4, FIG. 1) Japanese Patent Laid-Open No. 10-170855 (page 4, FIG. 1) Japanese Patent Laid-Open No. 11-264887 (pages 7-8, FIG. 1) Japanese Patent Laid-Open No. 2001-99978 (page 4-5, FIG. 1) JP 2003-177193 A (page 3, FIG. 4)

  By the way, one wiring for one LPRM detector of one LPRM assembly is extended from the LPRM assembly in the nuclear reactor to the APRM unit or the central control room installed outside the containment vessel. It is. For example, in a 1100 MWe boiling water nuclear power plant, since 43 LPRM assemblies having four LPRM detectors are installed in the core, a large number of wires such as 172 are installed outside the reactor containment vessel from the LPRM assembly. It will be pulled to the APRM unit. The APRM unit is usually installed in a central control room or the like. For this reason, a large number of wires are drawn from the reactor containment vessel to the central control room.

  Further, when a plurality of temperature detectors are provided in the cylinders constituting the LPRM assembly instead of the TIP detector, one wiring is connected to one temperature detector of one LPRM assembly. From the assembly, it is drawn to a gamma dose calculating means for calculating a gamma dose installed outside the reactor containment vessel. For example, assuming that the number of temperature detectors is two or more times the number of LPRMs, the number of wires such as three or more times that of the configuration using the TIP detector is stored in the reactor from the LPRM assembly. It will be in the state pulled out of the container. Since the γ dose calculation means is usually installed in a central control room or the like, when a plurality of temperature detectors are provided in the cylinder constituting the LPRM assembly instead of the TIP detector, the TIP detector is used. As a result, a large number of wires, such as three times or more that of the conventional configuration, are drawn from the reactor containment vessel to the central control room.

  The wiring from the LPRM assembly is drawn out of the reactor containment vessel through a through portion provided in the reactor containment vessel. For this reason, when the wiring between the LPRM assembly and the γ-ray calculating means and the APRM unit located outside the reactor containment vessel is increased several times, the penetration portion provided in the reactor containment vessel There is a need to increase the number of wires, and the wiring work becomes complicated due to the connection and routing of a large number of wires in the penetrating part and other places.

  As described above, when a plurality of temperature detectors are provided in the cylinders constituting the LPRM assembly instead of the TIP detectors, it is possible to eliminate the TIP detectors and simplify the device configuration. The increase leads to problems such as complicated installation work of the reactor power measuring device, increased work volume and cost, and complicated maintenance work. Therefore, there is a demand for a reactor power measurement device that can simplify the configuration of the device while suppressing an increase in the number of wires.

  An object of the present invention is to simplify the configuration of a reactor power measuring device while suppressing an increase in the number of wires.

  The reactor power measuring device according to the present invention includes a cylindrical body installed in the core of a nuclear reactor so as to extend along the axial direction of the nuclear reactor, and the cylindrical body at different positions in the extending direction of the cylindrical body. An ionization chamber for detecting γ-rays arranged in a distributed manner, and a calculation means for calculating the output of the reactor based on a change in the amount of electricity generated by the ionizing action of γ-rays in the ionization chamber for γ-ray detection, This calculation means solves the above-mentioned problem by adopting a configuration for transmitting a signal for instructing a protection operation of the reactor in accordance with the calculated output information of the reactor.

  The present inventors provide a LPRM detector when the sensitivity of the LPRM detector comprising a neutron detector for detecting the amount of neutron is reduced by the neutron irradiation when the TIP detector or a plurality of temperature detectors replacing the TIP detector is reduced. Since it is provided for correcting the detection value in the case of TRM, a TIP detector or a plurality of temperature detectors instead of the TIP detector can be used by using a detector whose sensitivity is not easily lowered as an LPRM detector. I thought about losing. Since the γ dose changes in correlation with the amount of neutrons, the reactor power can be detected by detecting the γ dose, so we considered using a detector that detects the γ dose as the LPRM detector. .

  Here, the plurality of temperature detectors instead of the TIP detector detects the γ dose from the temperature based on the fact that the change in the γ dose and the temperature change are correlated. However, there is a time difference between the change in the γ dose and the change in the temperature in the furnace corresponding to the change in the γ dose. For this reason, when a temperature detector is used for LPRM detection in order to detect a γ dose, when an abnormality occurs in the reactor output, a time difference occurs between the actual occurrence of the abnormality and the execution of the protective operation. The problem arises.

  Therefore, by using an ionization chamber for detecting γ-rays as an LPRM detector as in the configuration of the present invention, when a reactor power abnormality occurs, the reactor can be protected with little time difference. Become. Furthermore, in the ionization chamber for γ-ray detection, the sensitivity is hardly lowered. Therefore, by adopting the configuration as in the present invention, it is not necessary to use a TIP detector or a plurality of temperature detectors instead of the TIP detector, and the configuration of the reactor power measuring device can be achieved while suppressing an increase in the number of wires. It can be simplified.

  Further, five or more γ-ray detection ionization chambers are installed in the cylinder at different positions in the extending direction of the cylinder, and the calculation means is a γ-ray detection ionization chamber at each position in the cylinder. Information on the output of the reactor at each position calculated based on the change in the amount of electricity generated is transmitted. By adopting such a configuration, the ionization chamber for detecting γ-rays is placed at the upper part, the central part, the bottom part of the core, the intermediate position between the upper part and the central part, and the position inside the cylinder corresponding to the intermediate position between the central part and the bottom part. The calculation means transmits the output information of the reactor that is installed and measured by the ionization chamber for detecting γ-rays at each position, so that the power distribution of the reactor can be monitored based on the information transmitted from the calculation means.

  Furthermore, if the ionization chamber for detecting γ-rays has a configuration in which eight or nine γ-ray detection ionization chambers are dispersed at different positions in the extending direction of the cylinder, the number of atoms is suppressed while suppressing an increase in the number of wires. This is preferable because the measurement accuracy of the power distribution of the furnace can be improved.

  In addition, an A / D conversion means for converting an analog signal corresponding to a change in the amount of electricity generated in the ionization chamber for detecting γ-rays into a digital signal is provided. The A / D conversion means is installed in the reactor containment vessel, and is configured to transmit a digital signal to the calculation means via an optical fiber cable connected between the respective optical communication units. With such a configuration, by installing the A / D conversion means in the reactor containment vessel, the optical fiber cable penetrates the penetration portion provided in the wall of the reactor containment vessel and the reactor containment vessel It will be pulled out. For this reason, the number of wires drawn out from the inside of the reactor containment vessel can be reduced as compared with the case of drawing out the wires for electrical connection from the ionization chamber for detecting γ rays to the outside of the containment vessel.

  ADVANTAGE OF THE INVENTION According to this invention, the structure of a reactor power measuring device can be simplified, suppressing the increase in the number of wiring.

  Hereinafter, an embodiment of a reactor power measuring apparatus to which the present invention is applied will be described with reference to FIG. FIG. 1 is a diagram schematically showing a schematic configuration of a reactor power measuring device to which the present invention is applied in a state where it is installed in a nuclear power plant.

  As shown in FIG. 1, the reactor power measuring device of this embodiment includes a plurality of γ-ray detection ionization chambers 1 serving as local area power monitor (hereinafter referred to as LPRM) detectors. LPRM assembly 5 accommodated in the body 3, LPRM field board 7 serving as A / D conversion means for converting analog signals into digital signals, and average output area monitor serving as computing means for computing reactor power and the like ( Average Power Range Monitor Unit (hereinafter abbreviated as APRM) unit 9 and the like.

  The plurality of γ-ray detection ionization chambers 1 are installed in the cylinder 3 of the LPRM assembly 5 while being dispersed in the extending direction of the cylinder 3. The LPRM assembly 5 is installed in the core 13 in the nuclear reactor pressure vessel 11 of the nuclear power plant in a state extending along the axial direction, that is, the height direction of the nuclear reactor. Accordingly, the plurality of γ-ray detection ionization chambers 1 are arranged in a state of being dispersed and arranged in the core 13 along the axial direction of the nuclear reactor. Further, the wires 15 connected to the individual γ-ray detection ionization chambers 1, that is, the same number of wires 15 as the number of γ-ray detection ionization chambers 1 installed in the cylinder 3 are the cylinders of the LPRM assembly 5. The body 3 is pulled out from one end, usually the lower end. In the nuclear power output detection apparatus of this embodiment, the LPRM assembly 5 has nine γ-ray detection ionization chambers 1.

  The reactor power measuring apparatus includes a plurality of such LPRM assemblies 5, and the plurality of LPRM assemblies 5 are equally distributed in the core 13 in a state of extending along the axial direction of the reactor as described above. It is distributed and arranged. At this time, the γ-ray detection ionization chambers 1 installed at the same position in the cylinder 3 of each LPRM assembly 5 are installed so as to come to the same position in the height direction in the core 13. Therefore, a plurality of γ-ray detection ionization chambers 1 are installed evenly distributed at the same height of the core 13. In the nuclear power output detection apparatus of the present embodiment, the LPRM assembly 5 has nine γ-ray detection ionization chambers 1, so that the γ-ray detection ionization chamber has nine stages in the height direction in the core 13. 1 is provided, and each stage is provided with γ-ray detection ionization chambers 1 corresponding to the number of LPRM assemblies 5 installed in the core 13. In FIG. 1, only one LPRM assembly 5 is drawn for easy understanding of the drawing, but actually, a plurality of LPRM assemblies 5 are installed in the core 13.

  The LPRM field board 7 is installed in a space between the reactor pressure vessel 11 and the reactor containment vessel 17 containing the reactor pressure vessel 11, and an A / D conversion circuit for converting an analog signal into a digital signal, An optical communication circuit 7 a for converting an electrical signal from the A / D conversion circuit into an optical signal and transmitting the optical signal via the optical fiber cable 19 is provided. The wiring 15 from the LPRM assembly 5 is connected to an input terminal provided on the A / D conversion circuit side of the LPRM field board 7. On the other hand, an optical fiber cable 19 is connected to an output terminal provided on the optical communication circuit 7a side.

  The APRM unit 9 is installed in a central control room of a nuclear power plant or the like, performs an average process of ionization current signals from each γ-ray detection ionization chamber 1 of each LPRM assembly 5, and calculates the output of the entire reactor. Is. In addition, the APRM unit 9 compares the calculated reactor output information with a preset set value, and when the reactor output is equal to or higher than the set value, the operation of the reactor is safely performed. A signal for commanding a protection operation such as stopping is transmitted.

  In the calculation of the output of the reactor in which the γ-ray detection ionization chamber 1 in the APRM unit 9 is an LPRM detector, although there is a difference in current value, in principle, the conventional neutron detection ionization chamber is replaced with the LPRM. This is the same as when a detector is used. Further, the APRM unit 9 not only calculates the output of the reactor for the protection operation, but also the ionization current from each γ-ray detection ionization chamber 1 installed at the same position of each LPRM assembly 5. An average process is performed for each signal, and information on the output of the reactor for each position in the height direction of the core 13 is calculated and transmitted.

  Such an APRM unit 9 of this embodiment has an input terminal to which an optical fiber cable 19 is connected, and has an optical communication circuit 9a for converting an optical signal input from the input terminal into an electrical signal. doing. Therefore, the optical fiber cable 19 having one end connected to the LPRM field board 7 passes through the through portion 17a provided in the reactor containment vessel 17 and is drawn to the outside of the reactor containment vessel 17, and the other end is the APRM unit. 9 is connected to an input terminal provided in the optical communication circuit 9a. That is, the LPRM field board 7 and the APRM unit 9 are optically connected via the optical fiber cable 19. The penetrating portion 17a is closed with the optical fiber cable 19 penetrating by being filled with an appropriate resin material or the like.

  The APRM unit 9 also has an output terminal that outputs an electrical signal corresponding to the reactor output information calculated by the APRM unit 9, and the central control of the nuclear power plant via the wiring 21 connected to the output terminal. It is electrically connected to a process computer 23 installed in a room or the like. The process computer 23 is a part of the control device of the nuclear power plant, and performs a protective operation such as safely stopping the operation of the nuclear reactor when receiving a signal instructing a protective operation from the APRM unit 9. Further, the process computer 23 receives information on the output of the reactor for each position in the height direction of the core 13 from the APRM unit 9 and monitors the power distribution in the core 13.

  Here, when the sensitivity of the LPRM detector composed of a neutron detector for detecting the amount of neutrons is reduced due to neutron irradiation, the TIP detector or a plurality of temperature detectors replacing the TIP detector is reduced. Since it is provided to correct the detection value in the LPRM detector, a TIP detector or a plurality of TIP detectors can be substituted for the TIP detector by using a detector whose sensitivity is unlikely to decrease as the LPRM detector. We thought about eliminating the temperature detector. Since the γ dose changes in correlation with the amount of neutrons, the reactor power can be detected by detecting the γ dose, so we considered using a detector that detects the γ dose as the LPRM detector. .

  A plurality of temperature detectors instead of the conventionally used TIP detectors detect the γ dose from the temperature based on the correlation between the change in γ dose and the temperature change. However, there is a time difference between the change in the γ dose and the change in the temperature in the furnace corresponding to the change in the γ dose. For this reason, when a temperature detector is used for LPRM detection in order to detect a γ dose, when an abnormality occurs in the reactor output, a time difference occurs between the actual occurrence of the abnormality and the execution of the protective operation. The problem arises.

On the other hand, in the reactor power measuring apparatus of the present embodiment, the γ-ray detection ionization chamber 1 that does not use ²³⁵ U and ²³⁴ U is used as the LPRM detector, so the sensitivity of the LPRM detector is reduced. rare. Furthermore, unlike the detection of γ dose using a temperature detector, the γ-ray detection ionization chamber 1 can detect a change in γ dose with little time difference. For this reason, it is not necessary to use a TIP detector or a plurality of temperature detectors in place of the TIP detector, and a drive mechanism required when using the TIP detector or a plurality of temperature detectors provided in place of the TIP detector are provided. Wiring can be eliminated. Further, when a reactor power measurement device having a measurement accuracy comparable to that of the reactor power measurement device of the present embodiment is formed with a configuration in which a conventional LPRM assembly includes an LPRM detector and a temperature detector, Since the number of detectors installed in one LPRM assembly can be smaller than that in the conventional reactor power measuring device, the number of wirings can be reduced. Therefore, the configuration of the reactor power measuring device can be simplified while suppressing an increase in the number of wires.

  Furthermore, since the reactor power measurement device of the embodiment can suppress an increase in the number of wires, the installation work of the reactor power measurement device can be simplified, the amount of work and man-hours can be reduced, the cost can be reduced, maintenance work and management work Can be simplified. In addition, in the reactor power measuring device of this embodiment, there is no drive mechanism for the TIP detector, and the number of detectors is reduced compared to the case where a plurality of temperature detectors are used instead of the TIP detector. , The maintenance work of the device can be simplified.

  Furthermore, in the conventional reactor power measurement device, the calibration operation of the LPRM detector is required at a frequency of about once a month, which is a burden on the operator in the nuclear power plant. However, in the reactor power measuring device of the present embodiment, the sensitivity of the γ-ray detection ionization chamber 1 hardly decreases, so that the burden on the operator in the operation of the nuclear power plant can be reduced.

In addition, when the LPRM detector uses a fission material such as ²³⁵ U and ²³⁴ U, notification to the government office or the like is required. However, in the reactor power measurement device of this embodiment, the LPRM detector Is an ionization chamber 1 for detecting γ-rays that does not use fission substances, so that notification to the government office is not required, and management work in using the reactor power measurement device can be simplified.

  By the way, the ionization current signal generated by the LPRM detector is also used for monitoring the power distribution of the reactor by the core performance calculation. However, in a configuration in which a TIP detector or a plurality of temperature detectors replacing the TIP detector is provided as in a conventional reactor power detection device, the diameter of the cylinder is within the cylinder of one LPRM assembly. Due to restrictions, usually only 4 or less LPRM detectors can be installed. That is, the output of the reactor can be detected only at a position of 4 or less in the axial direction of the reactor, that is, in the height direction. Therefore, in the conventional reactor power detection device, in order to measure the power distribution of the reactor with higher accuracy than that measured by the LPRM detector, for example, once a month, the TIP detector or the temperature detector increases the core power. The reactor power distribution is monitored by measuring the reactor power at more positions than the position where the vertical LPRM detector is installed.

  On the other hand, if the TIP detector and a plurality of temperature detectors replacing the TIP detector are eliminated as in the reactor power measuring device of the present embodiment, a plurality of temperature detectors are monitored when the reactor power distribution is monitored. The distribution of reactor power is detected only with the ionization chamber for detecting γ-rays. Therefore, in the reactor power measuring apparatus of this embodiment, five or more γ-ray detection ionization chambers 1 are dispersed in different positions in the extending direction of the cylinder 3 in the cylinder 3 of one LPRM assembly 5. It is installed. In the reactor power measuring apparatus of this embodiment, a TIP detector and a plurality of temperature detectors instead of the TIP detector are not required. More LPRM detectors than the above can be installed in the cylinder. In this way, the measurement accuracy of the power distribution of the reactor by the LPRM detector is improved by installing more LPRM detectors than the conventional one in the cylinder.

  At this time, as the number of γ-ray detection ionization chambers 1 installed in the cylinder 3 of one LPRM assembly 5 increases, the measurement accuracy of the reactor power distribution can be further improved. Since the number of wires increases by the number of boxes 1, it is not desirable that the number of γ-ray detection ionization chambers 1 is too large in order to suppress an increase in the number of wires. Therefore, in order to further improve the measurement accuracy of the power distribution of the reactor while suppressing the increase in the number of wires, the number of γ-ray detection ionization chambers 1 installed in the cylinder 3 of one LPRM assembly 5 is , 8 or 9 is desirable.

  Furthermore, in the conventional reactor power measuring device, the measurement of the reactor power by the TIP detector and the temperature detector requires several hours including various adjustment times, so it is only once a month. Not done. However, in the reactor power measurement apparatus of this embodiment, the ionization chamber 1 for γ-ray detection is used as the LPRM detector, and the signal from the ionization chamber 1 for γ-ray detection is arbitrarily set as an on-line signal at a necessary frequency. It can be taken out. For this reason, it is possible to monitor the power distribution with higher accuracy than the conventional monitoring of the power distribution of the reactor by the core performance calculation using the conventional LPRM detector.

  Furthermore, in the reactor power measuring device of the present embodiment, the LPRM field panel 7 is installed in the reactor containment vessel 17, and the LPRM field panel 7 and the APRM unit 9 are connected by an optical fiber cable 19. For this reason, the optical fiber cable 19 is drawn out from the penetration part 17 a of the reactor containment vessel 17. For this reason, the number of wirings drawn from the inside of the reactor containment vessel to the outside of the reactor containment vessel can be reduced as compared with the conventional case where the electrical wiring is drawn out from the penetration portion of the reactor containment vessel. In addition, since the number of wires drawn out from the reactor containment vessel to the outside of the reactor containment vessel is reduced, the number of through portions of the reactor containment vessel can be reduced. In addition, by using optical transmission between the LPRM field board 7 and the APRM unit 9, it is possible to construct a system that is resistant to noise caused by lightning and the like.

  Further, in a plant having a relatively small core, the number of LPRM assemblies that can be arranged in the core is smaller than in a plant having a relatively large core, and therefore, an LPRM detector for inputting to the APRM unit for obtaining the average output of the core. In other words, the number of LPRM detectors connected to one APRM unit is also small. However, the APRM unit is a reactor power measuring device installed in, for example, a boiling water nuclear power plant in order to be able to perform a core protection operation even if an APRM unit failure occurs. Necessary. For this reason, in the conventional reactor power measurement device, the signal from the same LPRM detector is shared between different APRM units by inputting the signal of one LPRM detector to two different APRM units. Thus, the signal from each LPRM detector is provided to a 6-channel APRM unit.

  However, if the signal from one LPRM detector is shared between different APRM units in this way, if the LPRM detector fails and outputs an incorrect signal, the erroneous signal is sent to two different APRM units. Will be input. Therefore, in the conventional reactor power measurement device, the failure of the APRM unit can be compensated by using 6 channels. However, when the LPRM detector fails, the LPRM detector covers two APRM units having different influences of the failure. There is a possibility that reliability may be lowered.

  On the other hand, in the reactor power measuring device of the present embodiment, the number of γ-ray detection ionization chambers 1 serving as LPRM detectors included in one LPRM assembly 5 is larger than that in the conventional reactor power measuring device. The positions of adjacent LPRM detectors are close. For this reason, in the reactor power measuring apparatus of this embodiment, one LPRM is obtained by inputting signals from the γ-ray detection ionization chambers 1 adjacent to each other in the same LPRM assembly 5 to different APRM units 9. The failure of the APRM unit can be compensated similarly to the case where the signal from the detector is shared between different APRM units.

  Therefore, signals from the γ-ray detection ionization chambers 1 adjacent to each other in the same LPRM assembly 5 are input to different APRM units 9, and further, the same γ-ray detection ionization chambers 1 are input to different APRM units 9. The signal from each γ-ray detection ionization chamber 1 is completely separated for each APRM unit 9 by appropriately distributing the signals from the respective γ-ray detection ionization chambers 1 to the respective APRM units 9. To do. Thereby, it is possible to eliminate sharing of signals from the same LPRM detector among different APRM units, and it is possible to reduce the influence of the failure of the LPRM detector on the protection operation, thereby improving the reliability.

  Further, the present invention is not limited to the configuration of the present embodiment, and various types can be used as long as a γ-ray detection ionization chamber is used as an LPRM detector and five or more γ-ray detection ionization chambers are provided in one LPRM assembly. Can be configured.

It is a figure which shows typically the schematic structure of one Embodiment of the reactor power measuring device to which this invention is applied in the state installed in the nuclear power plant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ionization chamber for gamma ray detection 3 Tubular body 5 LPRM assembly 7 LPRM field board 9 APRM unit 11 Reactor pressure vessel 13 Reactor core 17 Reactor containment vessel 15, 21 Wiring 19 Optical fiber cable 23 Process computer

Claims (4)

Cylindrical body installed in the reactor core extending along the axial direction of the nuclear reactor, and γ-ray detection arranged in the tubular body at different positions in the extending direction of the cylindrical body An ionization chamber, and a calculation means for calculating the output of the nuclear reactor based on a change in the amount of electricity generated by the ionization action of γ-rays in the ionization chamber for γ-ray detection. Reactor output measuring device that transmits a signal to command the protection operation of the reactor according to the output information. Five or more γ-ray detection ionization chambers are installed in the cylinder so as to be dispersed at different positions in the extending direction of the cylinder, and the calculation means includes γ-ray detection ionization at each position in the cylinder. The reactor power measuring device according to claim 1, wherein information on the power output of the reactor at each position calculated based on a change in the amount of electricity generated in the box is transmitted. 3. The reactor output according to claim 2, wherein eight or nine gamma ray detection ionization chambers are installed in the cylinder in a distributed manner at different positions in the extending direction of the cylinder. Measuring device. A / D conversion means for converting an analog signal corresponding to a change in the amount of electricity generated in the ionization chamber for detecting γ-rays into a digital signal, each of the A / D conversion means and the calculation means includes an optical communication unit The A / D conversion means is installed in a nuclear reactor containment vessel, and transmits a digital signal to the arithmetic means via an optical fiber cable connected between the optical communication sections. The reactor power measuring device according to any one of claims 1 to 3, wherein

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