JP2005172471A - Automatic thermal limit value monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic thermal limit value monitor capable of evaluating an output distribution of a fuel assembly, using measured values of a γ-thermometer and an LPRM, and capable of enhancing evaluation precision of a thermal monitoring index value of fuel. <P>SOLUTION: The thermal monitoring index value is found from the measured value by the stationary type γ-thermometer 8, based on a relative relation between the measured value by the stationary type γ-thermometer 8 and the thermal monitoring index value, using the thermal monitoring index value of the fuel based on the in-furnace output distribution calculated in a nuclear reactor output monitor 10, the thermal monitoring index value is corrected based on a variation by the nuclear reactor output monitor 10, a corrected thermal monitoring index value is compared with a thermal operation limit value, and an alarm and an automatic control deterring signal are output to an automatic output controller 25 for conducting automatic control for a core flow rate or a control rod, when judging a run-out from the thermal operation limit value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention evaluates the thermal evaluation index value of the fuel by using the value of the in-core power detector of the boiling water reactor (BWR), monitors the compliance with the operation limit value, and The present invention relates to an automatic thermal limit value monitoring device that issues an automatic operation inhibition signal to an automatic operation control device.

  In general, in boiling water reactors, as a constant monitoring device, a device that evaluates and monitors at least the power distribution in the core, a local power region monitor (LPRM) for monitoring the neutron flux across the horizontal section of the core and the height direction. And an average power range monitor (APRM) for monitoring the average power level of the core.

  The above-mentioned apparatus for evaluating and monitoring the power distribution in the core is designed to obtain the thermal power of the nuclear reactor by calculating the heat balance to the core, and to perform the thermal evaluation in the core. The neutron flux detector is configured to monitor neutrons at the installation position of the neutron flux detector and provide information such as a local increase in output. The APRM calculates the core average output level equivalent value by averaging the output signals of the LPRM, and when the calculated value exceeds a predetermined set value, has a role of outputting a signal such as an alarm or a scrum. Is.

  That is, FIG. 4 is a plan view showing a schematic configuration of the core of the BWR, in which a large number of fuel assemblies 1 are arranged in a square lattice shape, and a cross-like shape is formed at the center of the four fuel assemblies 1. The control rod 2 is disposed so as to be movable in the axial direction. In consideration of the symmetry of the arrangement of the fuel assemblies 1 installed in the core, a plurality of detector assemblies 3 are arranged in the core so that the entire core can be measured uniformly. As shown in FIG. 5, this detector assembly 3 includes a local output region monitor (LPRM) 5 for detecting the amount of neutrons composed of fission ionization chambers in a protective tube 4 penetrating the core along the axial direction. Four bodies are arranged at predetermined intervals, and a mobile neutron detector (TIP) 7 for sensitivity calibration of the LPRM5 is inserted into a guide tube 6 provided adjacent to the LPRM5. These LPRM5 Reactor power measurement and control are performed by the output of. The LPRM5 signals are collected and collected in an average power range monitor (APRM), and the average value of the signals is used to monitor changes in the neutron flux in the core.

  The neutron detector used as the LPRM uses a fission counter in which a fission material such as uranium 235 is applied to an electrode and an ionized gas is enclosed in the tube. For this reason, since the detection sensitivity deteriorates due to a decrease in fission material due to neutron irradiation, calibration is performed using the TIP. The TIP is the same neutron detector as the LPRM, but is usually kept outside the furnace and moved inside the detector assembly only when the LPRM is calibrated to compare and calibrate the LPRM.

  Thus, since the TIP is moved in the height direction within the detector assembly, continuous neutron flux measurement is possible in the height direction, and LPRMs that have only four locations in the height direction can be measured. It is also used to form a neutron flux distribution in the height direction by complementing the measured values.

  By the way, the improved boiling water nuclear power plant (ABWR) has a function of automatically performing an operation at the time of changing the reactor power including a control rod operation. As a protection function for this automatic control, there is an automatic thermal limit value monitoring device (ATLM). This device monitors whether the thermal index value of the fuel is operating within the operation limit value, and if it exceeds the operation limit value, issues an automatic control inhibition signal to the automatic operation control system, and automatically Operation control is stopped. FIG. 6 shows an example of the configuration of the ATLM.

  The thermal condition of the reactor fuel is regularly evaluated and monitored by the reactor power monitoring device 10. The fuel thermal monitoring index includes a critical power ratio monitoring index and a linear power density monitoring index. These thermal monitoring indices are evaluated based on the fuel output distribution.

  Therefore, the output signal 11 from the LPRM 5 is input to the reactor power measuring device 12, and the reactor power measuring device 12 averages the output signal 11 of the LPRM to calculate a core average power level equivalent value. Then, the LPRM signal 13 and the APRM signal 14 corresponding to the core average power level are input to the reactor power monitoring device 10 from the reactor power measurement 12. The reactor power monitoring device 10 is further supplied with plant data signals 16 such as the core flow rate and control rod insertion position from the plant data measuring device 15, and a mobile neutron flux detector which is a reactor power detector. A TIP signal 17 by (TIP) 7 is input, and the output distribution of the fuel portion is evaluated using these signals. Next, the fuel thermal monitoring index value is evaluated based on the output distribution. In order to perform automatic control of nuclear reactor operation control, that is, change of core flow rate or automatic change of control rod insertion position (control rod pattern), is the fuel thermal monitoring index value within operational limits? It is necessary to monitor at high speed, for example, at a cycle of about 100 ms.

  However, in order to evaluate the thermal monitoring index value in the reactor power monitoring apparatus 10, a large amount of calculation is required, and it is not possible to calculate with a calculation time that can withstand high-speed monitoring.

  Therefore, the automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value data 19 evaluated by the reactor power monitoring device 10 and the LPRM signal 20 at the time of calculating the fuel thermal monitoring index value. The change in the thermal monitoring index is obtained by sequentially acquiring the LPRM signal 21 and the APRM signal 22 and the core flow signal 23 and the control rod position signal 24 from the reactor power measuring device 12, and the thermal monitoring index value and LPRM value The thermal monitoring index value of the fuel is evaluated in accordance with the value of the LPRM signal 21 and the like using the proportional relationship. When this evaluation value exceeds a preset operation limit value, an automatic control inhibition signal 26 is issued to the automatic output control device 25.

  Next, an example of a method for evaluating the thermal index value of the fuel in the automatic thermal limit value monitoring device 18 will be described. Evaluation of the fuel thermal monitoring index value by the automatic thermal limit value monitoring device 18 classifies the fuel region surrounded by the LPRM 5 as the monitoring region. An example of the radial arrangement of the monitoring areas is shown in FIG. An area S surrounded by LPRM3 is one of the monitoring areas. The division of the monitoring area in the height direction differs depending on the type of monitoring index. The limit power ratio monitoring index greatly depends on the output of the entire fuel assembly. For this reason, the monitoring area for the limit output ratio monitoring index is one area in the entire height direction. On the other hand, the linear power density monitoring index directly depends on the power distribution in the height direction. For this reason, the monitoring area for the line power density monitoring index is divided into four in the height direction with the LPRM position in the height direction as the center.

An example of an evaluation formula for the limit output ratio monitoring index value in the automatic thermal limit value monitoring device 18 is shown in Formula 1.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCLPRMA (M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SCLPRMM (M): Sum of LPRM values in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
FIG. 8 shows an example of a target LPRM for which the sum of the monitoring area number LPRM values for the M: limit power ratio monitoring index is taken. That is, the values of all the LPRMs 5 in the four in-core detector assemblies 3 that define the monitoring region are summed by the limit output monitoring LPRM signal generating device 31. However, in the example of FIG. 8, LPRM at the lowest position is excluded, but it may be included. The evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the limit power ratio monitoring region. The correction coefficient A (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

An example of an evaluation formula of the line power density monitoring index value in the automatic thermal limit value monitoring apparatus 1 is shown in Formula 2.

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLLPRMA (N, M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SLLPRMM (N, M): Total LPRM value in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: height direction number of the monitoring area with respect to the linear power density monitoring index An example of a target LPRM for which the sum of LPRM values is taken is shown in FIG. That is, the values of the four LPRMs 5 positioned in the height direction N in the four in-core detector assemblies 3 that define the monitoring region are totaled by the LPRM signal generation device 32 for monitoring the linear power density. In FIG. 9, the symbols A, B, C, and D are used to represent the position in the height direction. The evaluation value of the line power density monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the line power density monitoring region. The correction coefficient B (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

  As the A factor and B factor appearing in Equation 1 and Equation 2, values including a margin coefficient are used to supplement the simplicity of Equation 1 or Equation 2 for evaluating the thermal monitoring index value.

  The power distribution of the fuel assembly varies depending on the state of the reactor. For example, a change in the core flow rate mainly causes a change in the power distribution in the height direction, and a change in the control rod insertion position causes a change in the power distribution of the entire core. In particular, when the insertion position of the control rod changes, the output distribution of the fuel assembly adjacent to the control rod whose insertion position has changed greatly changes. The power distribution of adjacent fuel assemblies also changes.

  The automatic thermal limit value monitoring apparatus uses LPRM to capture the change in the power distribution in the core, but LPRM is only installed in four locations in the axial direction. For this reason, the change of the power distribution in the core height direction cannot be captured with sufficient accuracy by LPRM alone.

  In order to compensate for this drawback, the reactor power monitoring device uses TIP that can continuously measure the power distribution in the height direction. However, since TIP is not a detector that is always installed in the furnace, information on continuous power distribution is periodically obtained by TIP, and the degree of change in power distribution at other times is taken in by LPRM information. It can be evaluated by the power distribution calculation function by the reactor core simulator of the reactor power monitoring device itself. On the other hand, in the automatic thermal limit value monitoring device, the change in the power distribution after taking in the information in the reactor power monitoring device relies only on the change in LPRM.

  From the above, it is necessary to set a correction amount with a large margin for the A factor and B factor appearing in Equations 1 and 2, and in some cases, there is still a sufficient margin, but the output There is a problem that an automatic control blocking signal may be issued to the automatic control device 25.

  Recently, as described in Japanese Patent Laid-Open No. 9-2111136, a γ-ray detector (γ thermometer) that does not require a driving device has been used in the configuration of LPRM instead of TIP. The γ thermometer measures the temperature of the γ-ray heating element in the detector assembly with a thermocouple, and measures the heat generated when the γ-rays emitted from the fuel rods are absorbed by the heating element. Therefore, since the detection sensitivity is hardly degraded by neutron irradiation, it can be installed in the furnace.

  As shown in FIG. 10, the arrangement of the γ thermometer 8 in the core radial direction is the same as that of the LPRM 5, and the arrangement in the height direction is arranged at the same position as the LPRM and further at an intermediate position thereof. 7 to 9 places are arranged in the vertical direction. Therefore, the γ-ray heat generation distribution obtained from the γ thermometer has an advantage that a more detailed distribution can be obtained than the LPRM 5 having only four places in the height direction, and the measured values of the γ thermometer and LPRM are used for fuel. The output distribution of the assembly can be evaluated, and the thermal monitoring index value of the fuel can be evaluated.

In view of such a point, the present invention can evaluate the output distribution of the fuel assembly by using the measured values of the γ thermometer 8 and the LPRM 5, improve the evaluation accuracy of the thermal monitoring index value of the fuel, It is an object of the present invention to obtain an automatic thermal limit value monitoring device capable of sending a more reliable automatic control inhibition signal to an output automatic control device.
Japanese Patent Laid-Open No. 9-2111136

  The invention according to claim 1 uses the thermal monitoring index value of the fuel based on the power distribution in the reactor calculated in the reactor power monitoring apparatus, and calculates the fixed γ at the time when the thermal monitoring index value is calculated. Based on the relative relationship between the measured value of the thermometer and the above-mentioned thermal monitoring index value, the current thermal monitoring index value is obtained from the measured value of the current fixed γ thermometer, and the core flow rate and control rod insertion The thermal monitoring based on the amount of change in the core thermal power output by the APRM signal configured based on the position and the measured value of LPRM from the time point when the fuel power monitoring index value is calculated by the reactor power monitoring device to the present time The index value is corrected, the corrected thermal monitoring index value is compared with the thermal operation limit value, and when it is determined that the thermal operation limit value is deviated, the core flow rate or the control rod is automatically controlled. Automatic output control An alarm and an automatic control inhibition signal are output to the control device.

The invention according to claim 2 is characterized in that, in the automatic thermal limit value monitoring apparatus according to claim 1, the fuel thermal monitoring index value is calculated by the following equations (3) and (4).

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Number in the height direction of the monitoring region with respect to the linear power density monitoring index. The invention according to claim 3 is the automatic thermal limit value monitoring device according to claim 1 or 2, wherein the fixed type is based on a change in the APRM signal. A transient correction processing device is provided for a transient change in the measured value of the γ thermometer.

  The invention according to claim 4 is the automatic thermal limit value monitoring device according to claim 3, wherein the transient correction processing device is a fixed γ thermometer arranged at the same position as the measured value of the LPRM and the LPRM. Compared with the value after the transient correction processing of the measured value, the value of the transient correction processing of the fixed γ thermometer is further corrected so as to correspond to the change of the measured value of the local output detector To do.

  The present invention uses the thermal monitoring index value of the fuel based on the power distribution in the furnace, and the measured value of the fixed γ thermometer at the time of calculating the thermal monitoring index value and the thermal monitoring index value Based on the relative relationship, the current thermal monitoring index value is obtained from the current measurement value of the fixed γ thermometer, so accurate automatic thermal limit value monitoring can be performed, which makes it reliable. It is possible to transmit a highly efficient automatic output control inhibition signal to the automatic output control device, and to enable more efficient operation of the nuclear reactor.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In the figure, the same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a diagram showing an overall configuration diagram of an automatic thermal limit value monitoring apparatus according to an embodiment of the present invention and other apparatuses related to the automatic thermal limit value monitoring apparatus. The measured value 27 of the γ thermometer 8 is input, and the reactor power monitoring device 10 receives the LPRM signal 13 from the reactor power measuring device 12 and the APRM signal 14 calculated by the reactor power measuring device 12. In addition to the input, the γ thermometer measurement value 28 is input, the power distribution in the furnace is evaluated, and the thermal index value of the fuel is evaluated based on the power distribution. The automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value 19 and the γ thermometer measurement value 29 when the index value is calculated from the reactor power monitoring device 10. . The time when this data is input will be referred to as the initialization time of the automatic thermal limit value monitoring device 18.

During the period from the initialization time of the automatic thermal limit value monitoring device 18 to the next initialization time, the current γ thermometer measurement value signal 30 is received from the reactor power measurement device 12. And the thermal monitoring index value of the fuel is calculated by Equation 3 and Equation 4 from the γ thermometer measurement value.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Monitoring area height direction number for the line power density monitoring index The monitoring area number M is the same as in the case of the conventional automatic thermal limit value monitoring device using LPRM, but N appears in the line power density monitoring area. Corresponds to a γ thermometer. That is, the number of line power density monitoring regions in the height direction is equal to the number N of γ thermometers installed in the height direction.

  The automatic thermal limit value monitoring device 18 also incorporates a signal 22 of the average power region monitor APRM from the reactor power measurement device 12, and this signal is incorporated in order to capture changes in the core thermal power output. Therefore, other signals that can capture changes in the core thermal power may be used. For example, the value of the core thermal power monitor TPM may be used instead of APRM. In addition, the automatic thermal limit value monitoring device 18 incorporates plant data measurement values 23 and 24 such as a core flow rate and a control rod insertion position. Based on these data, the difference in the state of the plant between the initialization time of the automatic thermal limit value monitoring device 18 and the present time is recognized, the A factor and the B factor of the equations 3 and 4 are obtained, and the thermal monitoring of the fuel is performed. Evaluate the indicator value. When this evaluation value is compared with the operation limit value and the operation limit value is deviated, an automatic control inhibition signal 26 is issued to the output automatic control device 25.

  The A factor and B factor of Equation 3 and Equation 4 are set so as to include a margin, but when the automatic thermal limit value monitoring device 18 operates based on the γ thermometer 8, Since the change in the power distribution of the core can be captured more accurately than the automatic thermal limit value monitoring device that operates based on LPRM, it is possible to reduce the margin included in the A factor and B factor. As a result, it is possible to send an accurate and highly reliable automatic control blocking signal by the output automatic control device 25.

  Next, a second embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. The embodiment of FIG. 2 is obtained by adding a γ thermometer value transient correction device 33 to the automatic thermal limit value monitoring device 18 with respect to the embodiment of FIG.

  Since the γ thermometer measures the temperature of the metal part heated by γ rays, the response when the power of the core changes is slightly delayed from the LPRM that measures neutrons. However, the response delay of the γ thermometer can be estimated and evaluated with higher accuracy than the response change of the neutron flux. The γ thermometer value transient correction device 33 is a device that takes in the APRM signal 22 from the reactor power measurement device 12 and corrects the γ thermometer signal 30 by using the change in this signal. Thus, the automatic thermal limit value monitoring device 18 evaluates the fuel thermal monitoring index using the γ thermometer value corrected by the γ thermometer value transient correction device 33. By adding this correction, a more accurate automatic thermal limit value monitoring device can be obtained. A device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Next, a third embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. In the embodiment of FIG. 3, the LPRM signal 21 is further input to the γ thermometer value transient correction device 33 described in the embodiment of FIG. 2, and the LPRM signal 21 is used. . Thus, by using this LPRM signal, it is possible to capture a local change in neutron flux in the core. By comparing the measured value of the γ thermometer detector corresponding to the LPRM detector position with the LPRM value, the delay of the γ thermometer value with respect to the change in output at the LPRM detector position can be corrected. By adding, it can be set as a more accurate automatic thermal limit value monitoring apparatus. Similar to the second embodiment, a device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Examples of the method for correcting the transient of the γ thermometer measurement value according to the second embodiment and the third embodiment include methods disclosed in Japanese Patent Laid-Open Nos. 2001-99981 and 2001-83280.

The block diagram which shows 1st Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 2nd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 3rd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The figure which shows the example of horizontal arrangement | positioning of the in-furnace output detector assembly. The figure which shows the example of the vertical direction arrangement | positioning of the in-furnace output detector assembly by a prior art. The block diagram of one Example of the automatic thermal limit value monitoring apparatus by a prior art. The example of the monitoring area | region of an automatic thermal limit value monitoring apparatus. The example of the LPRM signal preparation apparatus for limit output ratio monitoring. The example of the LPRM signal preparation apparatus for line power density monitoring. The figure which shows the example of a vertical direction arrangement | positioning of (gamma) thermometer.

Explanation of symbols

1 Fuel assembly
2 Control rod
3 Detector assembly
4 protection tube
5 Local output area monitor (LPRM)
8 γ thermometer 10 Reactor power monitoring device
11 LPRM signal
12 Reactor power measuring device
13 LPRM signal
14 APRM signal
15 Plant data measuring device
16 Plant data signal
17 TIP signal
18 Automatic thermal limit value monitoring device
19 Fuel monitoring index value
20 LPRM signal when calculating thermal monitoring index value
21 LPRM signal
22 APRM signal
23 Core flow rate signal
24 Control rod position signal
25 Automatic output control device
26 Automatic control blocking signal
27 γ thermometer measured value
28 γ thermometer measured value
29 γ thermometer measured value when index value is calculated
30 γ thermometer measured value
31 LPRM signal generator for limit output ratio monitoring
32 LPRM signal generator for line power density monitoring
33 γ thermometer value transient correction device

  The present invention evaluates the thermal evaluation index value of the fuel by using the value of the in-core power detector of the boiling water reactor (BWR), monitors the compliance with the operation limit value, and The present invention relates to an automatic thermal limit value monitoring device that issues an automatic operation inhibition signal to an automatic operation control device.

  In general, in boiling water reactors, as a constant monitoring device, a device that evaluates and monitors at least the power distribution in the core, a local power region monitor (LPRM) for monitoring the neutron flux across the horizontal section of the core and the height direction. And an average power range monitor (APRM) for monitoring the average power level of the core.

  The above-mentioned apparatus for evaluating and monitoring the power distribution in the core is designed to obtain the thermal power of the nuclear reactor by calculating the heat balance to the core, and to perform the thermal evaluation in the core. The neutron flux detector is configured to monitor neutrons at the installation position of the neutron flux detector and provide information such as a local increase in output. The APRM calculates the core average output level equivalent value by averaging the output signals of the LPRM, and when the calculated value exceeds a predetermined set value, has a role of outputting a signal such as an alarm or a scrum. Is.

  That is, FIG. 4 is a plan view showing a schematic configuration of the core of the BWR, in which a large number of fuel assemblies 1 are arranged in a square lattice shape, and a cross-like shape is formed at the center of the four fuel assemblies 1. The control rod 2 is disposed so as to be movable in the axial direction. In consideration of the symmetry of the arrangement of the fuel assemblies 1 installed in the core, a plurality of detector assemblies 3 are arranged in the core so that the entire core can be measured uniformly. As shown in FIG. 5, this detector assembly 3 includes a local output region monitor (LPRM) 5 for detecting the amount of neutrons composed of fission ionization chambers in a protective tube 4 penetrating the core along the axial direction. Four bodies are arranged at predetermined intervals, and a mobile neutron detector (TIP) 7 for sensitivity calibration of the LPRM5 is inserted into a guide tube 6 provided adjacent to the LPRM5. These LPRM5 Reactor power measurement and control are performed by the output of. The LPRM5 signals are collected and collected in an average power range monitor (APRM), and the average value of the signals is used to monitor changes in the neutron flux in the core.

  The neutron detector used as the LPRM uses a fission counter in which a fission material such as uranium 235 is applied to an electrode and an ionized gas is enclosed in the tube. For this reason, since the detection sensitivity deteriorates due to a decrease in fission material due to neutron irradiation, calibration is performed using the TIP. The TIP is the same neutron detector as the LPRM, but is usually kept outside the furnace and moved inside the detector assembly only when the LPRM is calibrated to compare and calibrate the LPRM.

  Thus, since the TIP is moved in the height direction within the detector assembly, continuous neutron flux measurement is possible in the height direction, and LPRMs that have only four locations in the height direction can be measured. It is also used to form a neutron flux distribution in the height direction by complementing the measured values.

  By the way, the improved boiling water nuclear power plant (ABWR) has a function of automatically performing an operation at the time of changing the reactor power including a control rod operation. As a protection function for this automatic control, there is an automatic thermal limit value monitoring device (ATLM). This device monitors whether the thermal index value of the fuel is operating within the operation limit value, and if it exceeds the operation limit value, issues an automatic control inhibition signal to the automatic operation control system, and automatically Operation control is stopped. FIG. 6 shows an example of the configuration of the ATLM.

  The thermal condition of the reactor fuel is regularly evaluated and monitored by the reactor power monitoring device 10. The fuel thermal monitoring index includes a critical power ratio monitoring index and a linear power density monitoring index. These thermal monitoring indices are evaluated based on the fuel output distribution.

  Therefore, the output signal 11 from the LPRM 5 is input to the reactor power measuring device 12, and the reactor power measuring device 12 averages the output signal 11 of the LPRM to calculate a core average power level equivalent value. Then, the LPRM signal 13 and the APRM signal 14 corresponding to the core average power level are input to the reactor power monitoring device 10 from the reactor power measurement 12. The reactor power monitoring device 10 is further supplied with plant data signals 16 such as the core flow rate and control rod insertion position from the plant data measuring device 15, and a mobile neutron flux detector which is a reactor power detector. A TIP signal 17 by (TIP) 7 is input, and the output distribution of the fuel portion is evaluated using these signals. Next, the fuel thermal monitoring index value is evaluated based on the output distribution. In order to perform automatic control of nuclear reactor operation control, that is, change of core flow rate or automatic change of control rod insertion position (control rod pattern), is the fuel thermal monitoring index value within operational limits? It is necessary to monitor at high speed, for example, at a cycle of about 100 ms.

  However, in order to evaluate the thermal monitoring index value in the reactor power monitoring apparatus 10, a large amount of calculation is required, and it is not possible to calculate with a calculation time that can withstand high-speed monitoring.

  Therefore, the automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value data 19 evaluated by the reactor power monitoring device 10 and the LPRM signal 20 at the time of calculating the fuel thermal monitoring index value. The change in the thermal monitoring index is obtained by sequentially acquiring the LPRM signal 21 and the APRM signal 22 and the core flow signal 23 and the control rod position signal 24 from the reactor power measuring device 12, and the thermal monitoring index value and LPRM value The thermal monitoring index value of the fuel is evaluated in accordance with the value of the LPRM signal 21 and the like using the proportional relationship. When this evaluation value exceeds a preset operation limit value, an automatic control inhibition signal 26 is issued to the automatic output control device 25.

  Next, an example of a method for evaluating the thermal index value of the fuel in the automatic thermal limit value monitoring device 18 will be described. Evaluation of the fuel thermal monitoring index value by the automatic thermal limit value monitoring device 18 classifies the fuel region surrounded by the LPRM 5 as the monitoring region. An example of the radial arrangement of the monitoring areas is shown in FIG. An area S surrounded by LPRM3 is one of the monitoring areas. The division of the monitoring area in the height direction differs depending on the type of monitoring index. The limit power ratio monitoring index greatly depends on the output of the entire fuel assembly. For this reason, the monitoring area for the limit output ratio monitoring index is one area in the entire height direction. On the other hand, the linear power density monitoring index directly depends on the power distribution in the height direction. For this reason, the monitoring area for the line power density monitoring index is divided into four in the height direction with the LPRM position in the height direction as the center.

An example of an evaluation formula for the limit output ratio monitoring index value in the automatic thermal limit value monitoring device 18 is shown in Formula 1.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCLPRMA (M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SCLPRMM (M): Sum of LPRM values in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
FIG. 8 shows an example of a target LPRM for which the sum of the monitoring area number LPRM values for the M: limit power ratio monitoring index is taken. That is, the values of all the LPRMs 5 in the four in-core detector assemblies 3 that define the monitoring region are summed by the limit output monitoring LPRM signal generating device 31. However, in the example of FIG. 8, LPRM at the lowest position is excluded, but it may be included. The evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the limit power ratio monitoring region. The correction coefficient A (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

An example of an evaluation formula of the line power density monitoring index value in the automatic thermal limit value monitoring apparatus 1 is shown in Formula 2.

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLLPRMA (N, M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SLLPRMM (N, M): Total LPRM value in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: height direction number of the monitoring area with respect to the linear power density monitoring index An example of a target LPRM for which the sum of LPRM values is taken is shown in FIG. That is, the values of the four LPRMs 5 positioned in the height direction N in the four in-core detector assemblies 3 that define the monitoring region are totaled by the LPRM signal generation device 32 for monitoring the linear power density. In FIG. 9, the symbols A, B, C, and D are used to represent the position in the height direction. The evaluation value of the line power density monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the line power density monitoring region. The correction coefficient B (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

  As the A factor and B factor appearing in Equation 1 and Equation 2, values including a margin coefficient are used to supplement the simplicity of Equation 1 or Equation 2 for evaluating the thermal monitoring index value.

  The power distribution of the fuel assembly varies depending on the state of the reactor. For example, a change in the core flow rate mainly causes a change in the power distribution in the height direction, and a change in the control rod insertion position causes a change in the power distribution of the entire core. In particular, when the insertion position of the control rod changes, the output distribution of the fuel assembly adjacent to the control rod whose insertion position has changed greatly changes. The power distribution of adjacent fuel assemblies also changes.

  The automatic thermal limit value monitoring apparatus uses LPRM to capture the change in the power distribution in the core, but LPRM is only installed in four locations in the axial direction. For this reason, the change of the power distribution in the core height direction cannot be captured with sufficient accuracy by LPRM alone.

  In order to compensate for this drawback, the reactor power monitoring device uses TIP that can continuously measure the power distribution in the height direction. However, since TIP is not a detector that is always installed in the furnace, information on continuous power distribution is periodically obtained by TIP, and the degree of change in power distribution at other times is taken in by LPRM information. It can be evaluated by the power distribution calculation function by the reactor core simulator of the reactor power monitoring device itself. On the other hand, in the automatic thermal limit value monitoring device, the change in the power distribution after taking in the information in the reactor power monitoring device relies only on the change in LPRM.

  From the above, it is necessary to set a correction amount with a large margin for the A factor and B factor appearing in Equations 1 and 2, and in some cases, there is still a sufficient margin, but the output There is a problem that an automatic control blocking signal may be issued to the automatic control device 25.

  Recently, as described in Japanese Patent Application Laid-Open No. 9-2111136, a γ-ray detector (γ thermometer) that does not require a driving device can be used in the configuration of LPRM instead of TIP. The γ thermometer measures the temperature of the γ-ray heating element in the detector assembly with a thermocouple, and measures the heat generated when the γ-rays emitted from the fuel rods are absorbed by the heating element. Therefore, since the detection sensitivity is hardly degraded by neutron irradiation, it can be installed in the furnace.

  As shown in FIG. 10, the arrangement of the γ thermometer 8 in the core radial direction is the same as that of the LPRM 5, and the arrangement in the height direction is arranged at the same position as the LPRM and further at an intermediate position thereof. 7 to 9 places are arranged in the vertical direction. Therefore, the γ-ray heat generation distribution obtained from the γ thermometer has an advantage that a more detailed distribution can be obtained than the LPRM 5 having only four places in the height direction, and the measured values of the γ thermometer and LPRM are used for fuel. The output distribution of the assembly can be evaluated, and the thermal monitoring index value of the fuel can be evaluated.

In view of such a point, the present invention can evaluate the output distribution of the fuel assembly by using the measured values of the γ thermometer 8 and the LPRM 5, improve the evaluation accuracy of the thermal monitoring index value of the fuel, It is an object of the present invention to obtain an automatic thermal limit value monitoring device capable of sending a more reliable automatic control inhibition signal to an output automatic control device.
Japanese Patent Laid-Open No. 9-2111136

  The invention according to claim 1 uses the thermal monitoring index value of the fuel based on the power distribution in the reactor calculated in the reactor power monitoring apparatus, and calculates the fixed γ at the time when the thermal monitoring index value is calculated. Based on the relative relationship between the measured value of the thermometer and the above-mentioned thermal monitoring index value, the current thermal monitoring index value is obtained from the measured value of the current fixed γ thermometer, and the core flow rate and control rod insertion The thermal monitoring based on the amount of change in the core thermal power output by the APRM signal configured based on the position and the measured value of LPRM from the time point when the fuel power monitoring index value is calculated by the reactor power monitoring device to the present time The index value is corrected, the corrected thermal monitoring index value is compared with the thermal operation limit value, and when it is determined that the thermal operation limit value is deviated, the core flow rate or the control rod is automatically controlled. Automatic output control An alarm and an automatic control inhibition signal are output to the control device.

The invention according to claim 2 is characterized in that, in the automatic thermal limit value monitoring apparatus according to claim 1, the fuel thermal monitoring index value is calculated by the following equations (3) and (4).

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Number in the height direction of the monitoring region with respect to the linear power density monitoring index. The invention according to claim 3 is the automatic thermal limit value monitoring device according to claim 1 or 2, wherein the fixed type is based on a change in the APRM signal. A transient correction processing device is provided for a transient change in the measured value of the γ thermometer.

  The invention according to claim 4 is the automatic thermal limit value monitoring device according to claim 3, wherein the transient correction processing device is a fixed γ thermometer arranged at the same position as the measured value of the LPRM and the LPRM. Compared with the value after the transient correction processing of the measured value, the value of the transient correction processing of the fixed γ thermometer is further corrected so as to correspond to the change of the measured value of the local output detector To do.

  The present invention uses the thermal monitoring index value of the fuel based on the power distribution in the furnace, and the measured value of the fixed γ thermometer at the time of calculating the thermal monitoring index value and the thermal monitoring index value Based on the relative relationship, the current thermal monitoring index value is obtained from the current measurement value of the fixed γ thermometer, so accurate automatic thermal limit value monitoring can be performed, which makes it reliable. It is possible to transmit a highly efficient automatic output control inhibition signal to the automatic output control device, and to enable more efficient operation of the nuclear reactor.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In the figure, the same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a diagram showing an overall configuration diagram of an automatic thermal limit value monitoring apparatus according to an embodiment of the present invention and other apparatuses related to the automatic thermal limit value monitoring apparatus. The measured value 27 of the γ thermometer 8 is input, and the reactor power monitoring device 10 receives the LPRM signal 13 from the reactor power measuring device 12 and the APRM signal 14 calculated by the reactor power measuring device 12. In addition to the input, the γ thermometer measurement value 28 is input, the power distribution in the furnace is evaluated, and the thermal index value of the fuel is evaluated based on the power distribution. The automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value 19 and the γ thermometer measurement value 29 when the index value is calculated from the reactor power monitoring device 10. . The time when this data is input will be referred to as the initialization time of the automatic thermal limit value monitoring device 18.

During the period from the initialization time of the automatic thermal limit value monitoring device 18 to the next initialization time, the current γ thermometer measurement value signal 30 is received from the reactor power measurement device 12. And the thermal monitoring index value of the fuel is calculated by Equation 3 and Equation 4 from the γ thermometer measurement value.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Monitoring area height direction number for the line power density monitoring index The monitoring area number M is the same as in the case of the conventional automatic thermal limit value monitoring device using LPRM, but N appears in the line power density monitoring area. Corresponds to a γ thermometer. That is, the number of line power density monitoring regions in the height direction is equal to the number N of γ thermometers installed in the height direction.

  The automatic thermal limit value monitoring device 18 also incorporates a signal 22 of the average power region monitor APRM from the reactor power measurement device 12, and this signal is incorporated in order to capture changes in the core thermal power output. Therefore, other signals that can capture changes in the core thermal power may be used. For example, the value of the core thermal power monitor TPM may be used instead of APRM. In addition, the automatic thermal limit value monitoring device 18 incorporates plant data measurement values 23 and 24 such as a core flow rate and a control rod insertion position. Based on these data, the difference in the state of the plant between the initialization time of the automatic thermal limit value monitoring device 18 and the present time is recognized, the A factor and the B factor of the equations 3 and 4 are obtained, and the thermal monitoring of the fuel is performed. Evaluate the indicator value. When this evaluation value is compared with the operation limit value and the operation limit value is deviated, an automatic control inhibition signal 26 is issued to the output automatic control device 25.

  The A factor and B factor of Equation 3 and Equation 4 are set so as to include a margin, but when the automatic thermal limit value monitoring device 18 operates based on the γ thermometer 8, Since the change in the power distribution of the core can be captured more accurately than the automatic thermal limit value monitoring device that operates based on LPRM, it is possible to reduce the margin included in the A factor and B factor. As a result, it is possible to send an accurate and highly reliable automatic control blocking signal by the output automatic control device 25.

  Next, a second embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. The embodiment of FIG. 2 is obtained by adding a γ thermometer value transient correction device 33 to the automatic thermal limit value monitoring device 18 with respect to the embodiment of FIG.

  Since the γ thermometer measures the temperature of the metal part heated by γ rays, the response when the power of the core changes is slightly delayed from the LPRM that measures neutrons. However, the response delay of the γ thermometer can be estimated and evaluated with higher accuracy than the response change of the neutron flux. The γ thermometer value transient correction device 33 is a device that takes in the APRM signal 22 from the reactor power measurement device 12 and corrects the γ thermometer signal 30 by using the change in this signal. Thus, the automatic thermal limit value monitoring device 18 evaluates the fuel thermal monitoring index using the γ thermometer value corrected by the γ thermometer value transient correction device 33. By adding this correction, a more accurate automatic thermal limit value monitoring device can be obtained. A device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Next, a third embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. In the embodiment of FIG. 3, the LPRM signal 21 is further input to the γ thermometer value transient correction device 33 described in the embodiment of FIG. 2, and the LPRM signal 21 is used. . Thus, by using this LPRM signal, it is possible to capture a local change in neutron flux in the core. By comparing the measured value of the γ thermometer detector corresponding to the LPRM detector position with the LPRM value, the delay of the γ thermometer value with respect to the change in output at the LPRM detector position can be corrected. By adding, it can be set as a more accurate automatic thermal limit value monitoring apparatus. Similar to the second embodiment, a device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Examples of the method for correcting the transient of the γ thermometer measurement value according to the second embodiment and the third embodiment include methods disclosed in Japanese Patent Laid-Open Nos. 2001-99981 and 2001-83280.

The block diagram which shows 1st Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 2nd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 3rd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The figure which shows the example of horizontal arrangement | positioning of the in-furnace output detector assembly. The figure which shows the example of the vertical direction arrangement | positioning of the in-furnace output detector assembly by a prior art. The block diagram of one Example of the automatic thermal limit value monitoring apparatus by a prior art. The example of the monitoring area | region of an automatic thermal limit value monitoring apparatus. The example of the LPRM signal preparation apparatus for limit output ratio monitoring. The example of the LPRM signal preparation apparatus for line power density monitoring. The figure which shows the example of a vertical direction arrangement | positioning of (gamma) thermometer.

Explanation of symbols

1 Fuel assembly
2 Control rod
3 Detector assembly
4 protection tube
5 Local output area monitor (LPRM)
8 γ thermometer 10 Reactor power monitoring device
11 LPRM signal
12 Reactor power measuring device
13 LPRM signal
14 APRM signal
15 Plant data measuring device
16 Plant data signal
17 TIP signal
18 Automatic thermal limit value monitoring device
19 Fuel monitoring index value
20 LPRM signal when calculating thermal monitoring index value
21 LPRM signal
22 APRM signal
23 Core flow rate signal
24 Control rod position signal
25 Automatic output control device
26 Automatic control blocking signal
27 γ thermometer measured value
28 γ thermometer measured value
29 γ thermometer measured value when index value is calculated
30 γ thermometer measured value
31 LPRM signal generator for limit output ratio monitoring
32 LPRM signal generator for line power density monitoring
33 γ thermometer value transient correction device

  The present invention evaluates the thermal evaluation index value of the fuel by using the value of the in-core power detector of the boiling water reactor (BWR), monitors the compliance with the operation limit value, and The present invention relates to an automatic thermal limit value monitoring device that issues an automatic operation inhibition signal to an automatic operation control device.

  In general, in boiling water reactors, as a constant monitoring device, a device that evaluates and monitors at least the power distribution in the core, a local power region monitor (LPRM) for monitoring the neutron flux across the horizontal section of the core and the height direction. And an average power range monitor (APRM) for monitoring the average power level of the core.

  The above-mentioned apparatus for evaluating and monitoring the power distribution in the core is designed to obtain the thermal power of the nuclear reactor by calculating the heat balance to the core, and to perform the thermal evaluation in the core. The neutron flux detector is configured to monitor neutrons at the installation position of the neutron flux detector and provide information such as a local increase in output. The APRM calculates the core average output level equivalent value by averaging the output signals of the LPRM, and when the calculated value exceeds a predetermined set value, has a role of outputting a signal such as an alarm or a scrum. Is.

  That is, FIG. 4 is a plan view showing a schematic configuration of the core of the BWR, in which a large number of fuel assemblies 1 are arranged in a square lattice shape, and a cross-like shape is formed at the center of the four fuel assemblies 1. The control rod 2 is disposed so as to be movable in the axial direction. In consideration of the symmetry of the arrangement of the fuel assemblies 1 installed in the core, a plurality of detector assemblies 3 are arranged in the core so that the entire core can be measured uniformly. As shown in FIG. 5, this detector assembly 3 includes a local output region monitor (LPRM) 5 for detecting the amount of neutrons composed of fission ionization chambers in a protective tube 4 penetrating the core along the axial direction. Four bodies are arranged at predetermined intervals, and a mobile neutron detector (TIP) 7 for sensitivity calibration of the LPRM5 is inserted into a guide tube 6 provided adjacent to the LPRM5. These LPRM5 Reactor power measurement and control are performed by the output of. The LPRM5 signals are collected and collected in an average power range monitor (APRM), and the average value of the signals is used to monitor changes in the neutron flux in the core.

  The neutron detector used as the LPRM uses a fission counter in which a fission material such as uranium 235 is applied to an electrode and an ionized gas is enclosed in the tube. For this reason, since the detection sensitivity deteriorates due to a decrease in fission material due to neutron irradiation, calibration is performed using the TIP. The TIP is the same neutron detector as the LPRM, but is usually kept outside the furnace and moved inside the detector assembly only when the LPRM is calibrated to compare and calibrate the LPRM.

  Thus, since the TIP is moved in the height direction within the detector assembly, continuous neutron flux measurement is possible in the height direction, and LPRMs that have only four locations in the height direction can be measured. It is also used to form a neutron flux distribution in the height direction by complementing the measured values.

  By the way, the improved boiling water nuclear power plant (ABWR) has a function of automatically performing an operation at the time of changing the reactor power including a control rod operation. As a protection function for this automatic control, there is an automatic thermal limit value monitoring device (ATLM). This device monitors whether the thermal index value of the fuel is operating within the operation limit value, and if it exceeds the operation limit value, issues an automatic control inhibition signal to the automatic operation control system, and automatically Operation control is stopped. FIG. 6 shows an example of the configuration of the ATLM.

  The thermal condition of the reactor fuel is regularly evaluated and monitored by the reactor power monitoring device 10. The fuel thermal monitoring index includes a critical power ratio monitoring index and a linear power density monitoring index. These thermal monitoring indices are evaluated based on the fuel output distribution.

  Therefore, the output signal 11 from the LPRM 5 is input to the reactor power measuring device 12, and the reactor power measuring device 12 averages the output signal 11 of the LPRM to calculate a core average power level equivalent value. Then, the LPRM signal 13 and the APRM signal 14 corresponding to the core average power level are input to the reactor power monitoring device 10 from the reactor power measurement 12. The reactor power monitoring device 10 is further supplied with plant data signals 16 such as the core flow rate and control rod insertion position from the plant data measuring device 15, and a mobile neutron flux detector which is a reactor power detector. A TIP signal 17 by (TIP) 7 is input, and the output distribution of the fuel portion is evaluated using these signals. Next, the fuel thermal monitoring index value is evaluated based on the output distribution. In order to perform automatic control of nuclear reactor operation control, that is, change of core flow rate or automatic change of control rod insertion position (control rod pattern), is the fuel thermal monitoring index value within operational limits? It is necessary to monitor at high speed, for example, at a cycle of about 100 ms.

  However, in order to evaluate the thermal monitoring index value in the reactor power monitoring apparatus 10, a large amount of calculation is required, and it is not possible to calculate with a calculation time that can withstand high-speed monitoring.

  Therefore, the automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value data 19 evaluated by the reactor power monitoring device 10 and the LPRM signal 20 at the time of calculating the fuel thermal monitoring index value. The change in the thermal monitoring index is sequentially acquired from the reactor power measurement device 12 with the LPRM signal 21 and the APRM signal 22, and the core flow signal 23 and the control rod position signal 24, and the thermal monitoring index value and the LPRM value The thermal monitoring index value of the fuel is evaluated in accordance with the value of the LPRM signal 21 and the like using the proportional relationship. When this evaluation value exceeds a preset operation limit value, an automatic control inhibition signal 26 is issued to the automatic output control device 25.

  Next, an example of a method for evaluating the thermal index value of the fuel in the automatic thermal limit value monitoring device 18 will be described. Evaluation of the fuel thermal monitoring index value by the automatic thermal limit value monitoring device 18 classifies the fuel region surrounded by the LPRM 5 as the monitoring region. An example of the radial arrangement of the monitoring areas is shown in FIG. An area S surrounded by LPRM3 is one of the monitoring areas. The division of the monitoring area in the height direction differs depending on the type of monitoring index. The limit power ratio monitoring index greatly depends on the output of the entire fuel assembly. For this reason, the monitoring area for the limit output ratio monitoring index is one area in the entire height direction. On the other hand, the linear power density monitoring index directly depends on the power distribution in the height direction. For this reason, the monitoring area for the line power density monitoring index is divided into four in the height direction with the LPRM position in the height direction as the center.

An example of an evaluation formula for the limit output ratio monitoring index value in the automatic thermal limit value monitoring device 18 is shown in Formula 1.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCLPRMA (M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SCLPRMM (M): Sum of LPRM values in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
FIG. 8 shows an example of a target LPRM for which the sum of the monitoring area number LPRM values for the M: limit power ratio monitoring index is taken. That is, the values of all the LPRMs 5 in the four in-core detector assemblies 3 that define the monitoring region are summed by the limit output monitoring LPRM signal generating device 31. However, in the example of FIG. 8, LPRM at the lowest position is excluded, but it may be included. The evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the limit power ratio monitoring region. The correction coefficient A (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

An example of an evaluation formula of the line power density monitoring index value in the automatic thermal limit value monitoring apparatus 1 is shown in Formula 2.

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLLPRMA (N, M): Sum of LPRM values in the monitoring area by the automatic thermal limit value monitoring device
SLLPRMM (N, M): Total LPRM value in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: height direction number of the monitoring area with respect to the linear power density monitoring index An example of a target LPRM for which the sum of LPRM values is taken is shown in FIG. That is, the values of the four LPRMs 5 positioned in the height direction N in the four in-core detector assemblies 3 that define the monitoring region are totaled by the LPRM signal generation device 32 for monitoring the linear power density. In FIG. 9, the symbols A, B, C, and D are used to represent the position in the height direction. The evaluation value of the line power density monitoring index value by the reactor power monitoring device is the strictest fuel assembly value among the monitoring index values of the fuel assemblies in the line power density monitoring region. The correction coefficient B (M) is a coefficient depending on the core thermal output, the core flow rate, and the control rod insertion position.

  As the A factor and B factor appearing in Equation 1 and Equation 2, values including a margin coefficient are used to supplement the simplicity of Equation 1 or Equation 2 for evaluating the thermal monitoring index value.

  The power distribution of the fuel assembly varies depending on the state of the reactor. For example, a change in the core flow rate mainly causes a change in the power distribution in the height direction, and a change in the control rod insertion position causes a change in the power distribution of the entire core. In particular, when the insertion position of the control rod changes, the output distribution of the fuel assembly adjacent to the control rod whose insertion position has changed greatly changes. The power distribution of adjacent fuel assemblies also changes.

  The automatic thermal limit value monitoring apparatus uses LPRM to capture the change in the power distribution in the core, but LPRM is only installed in four locations in the axial direction. For this reason, the change of the power distribution in the core height direction cannot be captured with sufficient accuracy by LPRM alone.

  In order to compensate for this drawback, the reactor power monitoring device uses TIP that can continuously measure the power distribution in the height direction. However, since TIP is not a detector that is always installed in the furnace, information on continuous power distribution is periodically obtained by TIP, and the degree of change in power distribution at other times is taken in by LPRM information. It can be evaluated by the power distribution calculation function by the reactor core simulator of the reactor power monitoring device itself. On the other hand, in the automatic thermal limit value monitoring device, the change in the power distribution after taking in the information in the reactor power monitoring device relies only on the change in LPRM.

  From the above, it is necessary to set a correction amount with a large margin for the A factor and B factor appearing in Equations 1 and 2, and in some cases, there is still a sufficient margin, but the output There is a problem that an automatic control blocking signal may be issued to the automatic control device 25.

  Recently, as described in Japanese Patent Application Laid-Open No. 9-2111136, a γ-ray detector (γ thermometer) that does not require a driving device can be used in the configuration of LPRM instead of TIP. The γ thermometer measures the temperature of the γ-ray heating element in the detector assembly with a thermocouple, and measures the heat generated when the γ-rays emitted from the fuel rods are absorbed by the heating element. Therefore, since the detection sensitivity is hardly degraded by neutron irradiation, it can be installed in the furnace.

  As shown in FIG. 10, the arrangement of the γ thermometer 8 in the core radial direction is the same as that of the LPRM 5, and the arrangement in the height direction is arranged at the same position as the LPRM and further at an intermediate position thereof. 7 to 9 places are arranged in the vertical direction. Therefore, the γ-ray heat generation distribution obtained from the γ thermometer has an advantage that a more detailed distribution can be obtained than the LPRM 5 having only four places in the height direction, and the measured values of the γ thermometer and LPRM are used for fuel. The output distribution of the assembly can be evaluated, and the thermal monitoring index value of the fuel can be evaluated.

In view of such a point, the present invention can evaluate the output distribution of the fuel assembly by using the measured values of the γ thermometer 8 and the LPRM 5, improve the evaluation accuracy of the thermal monitoring index value of the fuel, It is an object of the present invention to obtain an automatic thermal limit value monitoring device capable of sending a more reliable automatic control inhibition signal to an output automatic control device.
Japanese Patent Laid-Open No. 9-2111136

  The invention according to claim 1 uses the thermal monitoring index value of the fuel based on the power distribution in the reactor calculated in the reactor power monitoring apparatus, and calculates the fixed γ at the time when the thermal monitoring index value is calculated. Based on the relative relationship between the measured value of the thermometer and the above-mentioned thermal monitoring index value, the current thermal monitoring index value is obtained from the current measured value of the fixed γ thermometer, and the core flow rate, control rod insertion The thermal monitoring based on the amount of change in the core thermal power output by the APRM signal configured based on the position and the measured value of LPRM from the time point when the fuel power monitoring index value is calculated by the reactor power monitoring device to the present time The index value is corrected, the corrected thermal monitoring index value is compared with the thermal operation limit value, and when it is determined that the thermal operation limit value is deviated, the core flow rate or the control rod is automatically controlled. Automatic output control An alarm and an automatic control inhibition signal are output to the control device.

The invention according to claim 2 is characterized in that, in the automatic thermal limit value monitoring apparatus according to claim 1, the fuel thermal monitoring index value is calculated by the following equations (3) and (4).

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Number in the height direction of the monitoring region with respect to the linear power density monitoring index. The invention according to claim 3 is the automatic thermal limit value monitoring device according to claim 1 or 2, wherein the fixed type is based on a change in the APRM signal. A transient correction processing device is provided for a transient change in the measured value of the γ thermometer.

  The invention according to claim 4 is the automatic thermal limit value monitoring device according to claim 3, wherein the transient correction processing device is a fixed γ thermometer arranged at the same position as the measured value of the LPRM and the LPRM. Compared with the value after the transient correction processing of the measured value, the value of the transient correction processing of the fixed γ thermometer is further corrected so as to correspond to the change of the measured value of the local output detector To do.

  The present invention uses the thermal monitoring index value of the fuel based on the power distribution in the furnace, and the measured value of the fixed γ thermometer at the time of calculating the thermal monitoring index value and the thermal monitoring index value Based on the relative relationship, the current thermal monitoring index value is obtained from the current measurement value of the fixed γ thermometer, so accurate automatic thermal limit value monitoring can be performed, which makes it reliable. It is possible to transmit a highly efficient automatic output control inhibition signal to the automatic output control device, and to enable more efficient operation of the nuclear reactor.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In the figure, the same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a diagram showing an overall configuration diagram of an automatic thermal limit value monitoring apparatus according to an embodiment of the present invention and other apparatuses related to the automatic thermal limit value monitoring apparatus. The measured value 27 of the γ thermometer 8 is input, and the reactor power monitoring device 10 receives the LPRM signal 13 from the reactor power measuring device 12 and the APRM signal 14 calculated by the reactor power measuring device 12. In addition to the input, the γ thermometer measurement value 28 is input, the power distribution in the furnace is evaluated, and the thermal index value of the fuel is evaluated based on the power distribution. The automatic thermal limit value monitoring device 18 receives the fuel thermal monitoring index value 19 and the γ thermometer measurement value 29 when the index value is calculated from the reactor power monitoring device 10. . The time when this data is input will be referred to as the initialization time of the automatic thermal limit value monitoring device 18.

During the period from the initialization time of the automatic thermal limit value monitoring device 18 to the next initialization time, the current γ thermometer measurement value signal 30 is received from the reactor power measurement device 12. And the thermal monitoring index value of the fuel is calculated by Equation 3 and Equation 4 from the γ thermometer measurement value.

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Monitoring area height direction number for the line power density monitoring index The monitoring area number M is the same as in the case of the conventional automatic thermal limit value monitoring device using LPRM, but N appears in the line power density monitoring area. Corresponds to a γ thermometer. That is, the number of line power density monitoring regions in the height direction is equal to the number N of γ thermometers installed in the height direction.

  The automatic thermal limit value monitoring device 18 also incorporates a signal 22 of the average power region monitor APRM from the reactor power measurement device 12, and this signal is incorporated in order to capture changes in the core thermal power output. Therefore, other signals that can capture changes in the core thermal power may be used. For example, the value of the core thermal power monitor TPM may be used instead of APRM. In addition, the automatic thermal limit value monitoring device 18 incorporates plant data measurement values 23 and 24 such as a core flow rate and a control rod insertion position. Based on these data, the difference in the state of the plant between the initialization time of the automatic thermal limit value monitoring device 18 and the present time is recognized, the A factor and the B factor of the equations 3 and 4 are obtained, and the thermal monitoring of the fuel is performed. Evaluate the indicator value. When this evaluation value is compared with the operation limit value and the operation limit value is deviated, an automatic control inhibition signal 26 is issued to the output automatic control device 25.

  The A factor and B factor of Equation 3 and Equation 4 are set so as to include a margin, but when the automatic thermal limit value monitoring device 18 operates based on the γ thermometer 8, Since the change in the power distribution of the core can be captured more accurately than the automatic thermal limit value monitoring device that operates based on LPRM, it is possible to reduce the margin included in the A factor and B factor. As a result, it is possible to send an accurate and highly reliable automatic control blocking signal by the output automatic control device 25.

  Next, a second embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. The embodiment of FIG. 2 is obtained by adding a γ thermometer value transient correction device 33 to the automatic thermal limit value monitoring device 18 with respect to the embodiment of FIG.

  Since the γ thermometer measures the temperature of the metal part heated by γ rays, the response when the power of the core changes is slightly delayed from the LPRM that measures neutrons. However, the response delay of the γ thermometer can be estimated and evaluated with higher accuracy than the response change of the neutron flux. The γ thermometer value transient correction device 33 is a device that takes in the APRM signal 22 from the reactor power measurement device 12 and corrects the γ thermometer signal 30 by using the change in this signal. Thus, the automatic thermal limit value monitoring device 18 evaluates the fuel thermal monitoring index using the γ thermometer value corrected by the γ thermometer value transient correction device 33. By adding this correction, a more accurate automatic thermal limit value monitoring device can be obtained. A device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Next, a third embodiment of the present invention relating to an automatic thermal limit value monitoring apparatus will be described with reference to FIG. In the embodiment of FIG. 3, the LPRM signal 21 is further input to the γ thermometer value transient correction device 33 described in the embodiment of FIG. 2, and the LPRM signal 21 is used. . Thus, by using this LPRM signal, it is possible to capture a local change in neutron flux in the core. By comparing the measured value of the γ thermometer detector corresponding to the LPRM detector position with the LPRM value, the delay of the γ thermometer value with respect to the change in output at the LPRM detector position can be corrected. By adding, it can be set as a more accurate automatic thermal limit value monitoring apparatus. Similar to the second embodiment, a device corresponding to the γ thermometer value transient correction device 33 may be incorporated in the reactor power measurement device 12.

  Examples of the method for correcting the transient of the γ thermometer measurement value according to the second embodiment and the third embodiment include methods disclosed in Japanese Patent Laid-Open Nos. 2001-99981 and 2001-83280.

The block diagram which shows 1st Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 2nd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The block diagram which shows 3rd Embodiment of the automatic thermal limit value monitoring apparatus in this invention. The figure which shows the example of horizontal arrangement | positioning of the in-furnace output detector assembly. The figure which shows the example of the vertical direction arrangement | positioning of the in-furnace output detector assembly by a prior art. The block diagram of one Example of the automatic thermal limit value monitoring apparatus by a prior art. The example of the monitoring area | region of an automatic thermal limit value monitoring apparatus. The example of the LPRM signal preparation apparatus for limit output ratio monitoring. The example of the LPRM signal preparation apparatus for line power density monitoring. The figure which shows the example of a vertical direction arrangement | positioning of (gamma) thermometer.

Explanation of symbols

1 Fuel assembly
2 Control rod
3 Detector assembly
4 protection tube
5 Local output area monitor (LPRM)
8 γ thermometer 10 Reactor power monitoring device
11 LPRM signal
12 Reactor power measuring device
13 LPRM signal
14 APRM signal
15 Plant data measuring device
16 Plant data signal
17 TIP signal
18 Automatic thermal limit value monitoring device
19 Fuel monitoring index value
20 LPRM signal when calculating thermal monitoring index value
21 LPRM signal
22 APRM signal
23 Core flow rate signal
24 Control rod position signal
25 Automatic output control device
26 Automatic control blocking signal
27 γ thermometer measured value
28 γ thermometer measured value
29 γ thermometer measured value when index value is calculated
30 γ thermometer measured value
31 LPRM signal generator for limit output ratio monitoring
32 LPRM signal generator for line power density monitoring
33 γ thermometer value transient correction device

Claims (4)

  Using the thermal monitoring index value of the fuel based on the power distribution in the reactor, calculated by the reactor power monitoring device, the measured value of the fixed γ thermometer at the time of calculating the thermal monitoring index value and the above thermal The current thermal monitoring index value is obtained from the current measurement value of the fixed γ thermometer based on the relative relationship with the static monitoring index value, and further based on the core flow rate, the control rod insertion position, and the LPRM measurement value. The thermal monitoring index value is corrected based on the amount of change in the core thermal power from the APRM signal configured as described above from the time point when the thermal monitoring index value of the fuel is calculated by the reactor power monitoring device to the present time. Compared to the thermal monitoring index value and the thermal operation limit value, when it is determined that the thermal operation limit value is deviated, the automatic flow control device that automatically controls the core flow rate or control rod Alarm and And an automatic thermal limit monitoring device, which outputs an automatic control inhibition signal. 2. The automatic thermal limit value monitoring apparatus according to claim 1, wherein the thermal monitoring index value of the fuel is calculated by the following formulas (3) and (4).

here,
FCPRA (M): Evaluation value of the limit power ratio monitoring index value by the automatic thermal limit value monitoring device
FCPRM (M): Evaluation value of the limit power ratio monitoring index value by the reactor power monitoring device
SCGTA (M): Sum of γ thermometer measured values in the monitoring area by automatic thermal limit value monitoring device
SCGTM (M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
A (M): Correction factor corresponding to changes in core conditions (A factor)
M: Monitoring area number for the limit output ratio monitoring index

here,
FLHGRA (N, M): Evaluation value of the linear power density monitoring index value by the automatic thermal limit value monitoring device
FLHGRM (N, M): Evaluation value of the line power density monitoring index value by the reactor power monitoring device
SLGTA (N, M): Sum of γ thermometer measured values in the monitoring area by the automatic thermal limit value monitoring device
SLGTM (N, M): Sum of γ thermometer measurements in the monitoring area by the reactor power monitoring device
B (N, M): Correction factor corresponding to changes in the core state (B factor)
M: Radial direction number of the monitoring area for the linear power density monitoring index
N: Height direction number of the monitoring area for the linear power density monitoring index   3. The automatic thermal limit value monitoring device according to claim 1, further comprising a transient correction processing device for a transient change in a measurement value of the fixed γ thermometer based on a change in the APRM signal.   The transient correction processing device compares the measured value of the LPRM with the value after the transient correction processing of the measured value of the fixed γ thermometer arranged at the same position as the LPRM, and the local output detector 4. The automatic thermal limit value monitoring apparatus according to claim 3, wherein the value of the transient correction processing of the fixed γ thermometer is further corrected so as to correspond to the change of the measured value.

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