JP5260407B2 - LPRM signal cable misconnection determination method and apparatus at startup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine misconnections of signal cables, arising from LPRM detectors at the starting a boiling-water reactor, since the boiling water reactor has gone into critical state, until a boiling-water reactor storage vessel is subjected to final inspection. <P>SOLUTION: A method for determining misconnections of the signal cables arising from a plurality of detectors, fixedly arranged at mutually different heights, in a guide tube installed in a pressure vessel of the boiling-water reactor for detecting thermal neutrons, includes the steps combining two each of all signals to be output from the plurality of detectors; evaluating signal correlations as to all of those combinations; and determining the misconnections, on the basis of the evaluation of the signal correlations as to all of those combinations, and an evaluation whether a phase delay of signals to be output from other combinations of detectors than those disposed at the lowest part of a reactor core of the boiling-water reactor occurs sequentially from a lower detector to an upper detector under predetermined conditions. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method and apparatus for determining an erroneous connection of a signal cable of an LPRM (local output region monitor) installed in a pressure vessel of a boiling water reactor, and in particular, an LPRM signal at the time of starting the boiling water reactor. The present invention relates to a method and an apparatus for determining a cable misconnection. It should be noted that the time when the boiling water reactor is started refers to the period from when the boiling water reactor reaches criticality until the inside of the boiling water reactor containment vessel is finally inspected.

  In a boiling water reactor, as shown in FIG. 6, in order to monitor the thermal neutron flux distribution in the reactor pressure vessel 10, a number of local output region monitors are provided between the fuels 11 in the reactor pressure vessel 10. (LPRM) 12 are installed in a distributed manner, and each LPRM 12 is installed in the reactor pressure vessel 10 through the bottom wall of the reactor pressure vessel 10 in order to detect thermal neutrons at a plurality of heights. Guide tube 13, a plurality of detectors 14 </ b> A to 14 </ b> D fixedly arranged at different heights in the guide tube 13, and a movable in-core reactor (not shown) that moves up and down electrically in the guide tube 13 In recent years, a guide cable for signal cables from a plurality of detectors 14A to 14D in the guide tube 13 of the LPRM 12 is used. At the lower end of the lower connector portion 15A~15D 13, erroneous connection for cable 16A~16D leading to the monitoring device of the thermal neutron flux distribution is scattered.

  This event can be detected by checking the difference between the LPRM output value and the TIP output value, or by checking the discrepancy between the control rod (CR) insertion / extraction position and the LPRM output value close to the CR. There is sex. However, in order to determine the final erroneous connection, it is necessary to stop the operation of the boiling water reactor and visually inspect the cable connector portion in the boiling water reactor containment vessel.

  As described above, the determination of the event is conventionally made when the difference between the LPRM output value and the TIP output value is large during the operation of the boiling water reactor, or when the CR insertion / extraction position is changed to the erroneous connection LPRM signal. It was limited to cases that had an impact, and the possibility of being overlooked could not be denied. Even when it seems that an erroneous connection has been detected, it cannot be determined whether it is an erroneous connection by itself or other factors such as signal drift of the LPRM detector. Moreover, since the said connection part exists in a nuclear reactor containment vessel, the visual inspection during operation | movement of a nuclear reactor is impossible. Therefore, even if the possibility of an incorrect connection is pointed out, it is necessary to consider factors other than the incorrect connection as a countermeasure, and therefore it is not always possible to prepare for efficient inspection and repair.

  Therefore, the present inventors described the thermal neutron flux density based on the fluctuation of the coolant density linked to the fluctuation of the void amount in the pressure vessel in the boiling water reactor in operation described in Japanese Patent Application No. 2008-56889. When the phase delay of the signal indicating the fluctuation of the signal is sequentially generated in the upper detector with respect to the lower detector, there is no erroneous connection, and the phase delay is sequentially generated in the upper detector with respect to the lower detector. In this case, an LPRM signal cable erroneous connection determination method for determining that there is an erroneous connection when not present is proposed.

"Summary of light water reactor power plant" Nuclear Safety Research Association, September 2008, pp.70-71

  However, the LPRM signal cable misconnection determination method described in the specification of Japanese Patent Application No. 2008-56889 has made it possible to determine the LPRM signal cable misconnection during operation of the boiling water reactor. In order to return to a normal connection even if stagnation is detected, there is a problem that it is necessary to wait until the boiling water reactor is stopped in the next periodic inspection or the like.

The object of the present invention is to advantageously solve the above problems, and the gist of the present invention is as follows.
1. In determining an erroneous connection in signal cables from a plurality of detectors that are fixedly arranged at different heights in LPRM guide tubes installed in a pressure vessel of a boiling water reactor and detect thermal neutrons,
When starting up the boiling water reactor, all the signals output from the plurality of detectors are combined in two, and the correlation of the signals is evaluated for all the combinations,
At least one of a combination of a signal output from a detector installed at the bottom of the core of the boiling water reactor and a signal output from a detector other than the detector installed at the bottom of the core. If the combination shows a strong correlation, determine that there is a misconnection,
All combinations of signals output from detectors installed at the bottom of the core of the boiling water reactor and signals output from detectors other than the detector installed at the bottom of the core are weakly correlated. , The correlation of each signal output from two adjacent detectors other than the detector installed at the bottom of the core of the boiling water reactor is classified into a first group, The combinations showing weaker correlation than the first group are classified into the second group and grouped,
When the grouping by the first group and the second group for all the combinations is different in at least one classification compared to the grouping for all the combinations at the time of normal connection Determines that there is a misconnection,
Combinations in which the grouping by the first group and the second group for all the combinations is the same as the grouping for all the combinations at the time of normal connection and is classified into the second group Among them, when the phase delay of the signals output from the detectors other than the detectors arranged at the bottom of the core of the boiling water reactor does not sequentially occur in the upper detector with respect to the lower detector An LPRM signal cable incorrect connection determination method at startup, wherein it is determined that there is an incorrect connection.

2. 2. The startup LPRM signal cable misconnection determination method according to claim 1, wherein the correlation is evaluated by coherence.

3. In an apparatus for judging erroneous connection in signal cables from a plurality of detectors fixedly arranged at different heights in a guide tube of LPRM installed in a pressure vessel of a boiling water reactor and detecting thermal neutrons ,
Phase difference detection means for detecting a phase difference in signals output from the plurality of detectors when the boiling water reactor is started up,
A signal correlation evaluation unit that evaluates the correlation of signals for all of the combinations of all the signals output from the plurality of detectors at the time of startup of the boiling water reactor,
At least one of a combination of a signal output from a detector installed at the bottom of the core of the boiling water reactor and a signal output from a detector other than the detector installed at the bottom of the core. If the combination shows a strong correlation, determine that there is a misconnection,
All combinations of signals output from detectors installed at the bottom of the core of the boiling water reactor and signals output from detectors other than the detector installed at the bottom of the core are weakly correlated. , A combination showing a strong correlation with signals output from two adjacent detectors other than the detector installed at the bottom of the core of the boiling water reactor is classified into a first group, The combinations showing weaker correlation than the first group among the combinations are classified into the second group and grouped.
When the grouping by the first group and the second group for all the combinations is different in at least one classification compared to the grouping for all the combinations at the time of normal connection Determines that there is a misconnection,
Combinations in which the grouping by the first group and the second group for all the combinations is the same as the grouping for all the combinations at the time of normal connection and is classified into the second group Among them, when the phase delay of the signals output from the detectors other than the detectors arranged at the bottom of the core of the boiling water reactor does not sequentially occur in the upper detector with respect to the lower detector A connection state determination means for determining that there is an erroneous connection;
Determination result output means for outputting a determination result made by the connection state determination means;
An LPRM signal cable erroneous connection determination device at the time of startup, comprising:

4). 4. The startup LPRM signal cable misconnection determination device according to claim 3, wherein the signal correlation evaluation unit evaluates the correlation by coherence.

  According to the start-up LPRM signal cable misconnection determination method of the present invention, a plurality of thermal neutrons that are fixedly arranged at different heights in guide tubes installed in a pressure vessel of a boiling water reactor are detected. When determining the incorrect connection in the LPRM signal cable from the detector, the correlation of the signals output from each detector when the boiling water reactor is started up is the distance of each detector from the core of the boiling water reactor, Paying attention to the point that depends on the distance between each detector, all the signals output from multiple detectors are combined in two, and the correlation of the signals is evaluated for all the combinations, and the evaluation and predetermined Under the above conditions, whether the phase delay of the signals output from the detectors other than the detector arranged at the bottom of the core of the boiling water reactor is sequentially generated in the upper detector with respect to the lower detector In order to determine whether there is a misconnection of the LPRM signal cable based on the evaluation of whether or not the LPRM signal cable is connected at the start-up, which is the period from when the boiling water reactor reaches the criticality until the boiling reactor containment is finally checked, If it is determined that there is a signal cable misconnection, full operation of the boiling water reactor can be performed after the normal connection is restored.

  According to the start-up LPRM signal cable misconnection determination method of the present invention, all signals output from a plurality of detectors are combined in two, and the correlation of signals is evaluated by coherence for all of the combinations. Thus, the correlation can be easily evaluated.

  Also, according to the start-up LPRM signal cable misconnection determination device of the present invention, thermal neutrons are detected by being fixedly arranged at different heights in guide tubes installed in a pressure vessel of a boiling water reactor. When determining misconnections in signal cables from multiple detectors, the correlation between the signals output from each detector at the start of the boiling water reactor is the distance between each detector and the core of the boiling water reactor. Focusing on the point that depends on the distance between each detector, the phase difference detection means detects the phase difference in the signals output from the multiple detectors when the boiling water reactor starts up, and evaluates the signal correlation The means sets all the signals output from the plurality of detectors to a combination of two, evaluates the correlation of the signals for all the combinations, and the connection state determination means sets the signal for all the combinations. Seki's evaluation, and under certain conditions, the phase delay of the signal output from the detector other than the detector placed at the bottom of the boiling water reactor core is detected above the detector below It is determined whether there is an incorrect connection of the LPRM signal cable based on the evaluation of whether or not there is a sequential occurrence in the reactor, and the determination result output means indicates that the boiling water reactor is critical Since it is output at start-up, which is the period from when it reaches the boiling reactor containment vessel to the final inspection, if it is determined that there is an incorrect connection of the LPRM signal cable, the boiling water atom Full-scale operation of the furnace can be performed.

  According to the start-up LPRM signal cable misconnection determination device of the present invention, the signal correlation evaluation means sets all signals output from the plurality of detectors to combinations of two, and correlates signals for all the combinations. By evaluating with coherence, the correlation can be easily evaluated.

It is a block diagram which shows the structure of one Example of the starting LPRM signal cable incorrect connection determination apparatus of this invention for enforcing one Embodiment of the LPRM signal cable incorrect connection determination method of starting of this invention. It is explanatory drawing which shows the fuel assembly in the pressure vessel of a boiling water reactor, the cooling water flow path between them, and the guide tube of LPRM. It is explanatory drawing which shows the phase difference image of the output signal at the time of boiling water reactor start-up of the four cables of LPRM. (A)-(c) is explanatory drawing which shows the aspect which evaluates the correlation of two signals used by the method of the said embodiment by coherence. It is explanatory drawing which shows the correspondence table with the aspect of a coherence and phase difference, and the aspect of a misconnection used with the method of the said embodiment. It is explanatory drawing which shows the fuel in the pressure vessel of a boiling water reactor, and the guide tube of LPRM.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the start-up LPRM signal cable misconnection determination device of the present invention for carrying out the embodiment of the start-up LPRM signal cable misconnection determination method of the present invention. FIG. 2 is a diagram illustrating a start-up LPRM signal cable erroneous connection determination apparatus according to the present embodiment, which includes a phase difference detection unit 1 as a phase difference detection unit, a signal correlation evaluation unit 2 as a signal correlation evaluation unit, and a connection state determination unit. A connection state determination unit 3 and a determination result output unit 4 as a determination result output unit. Specifically, based on a program given in advance, the phase difference detection unit 1 and the signal correlation evaluation unit 2 And a connection state determination unit 3 and a determination result output unit 4.

  By the way, in the pressure vessel 10 as shown on the right side of the boiling water reactor as shown in FIG. 6, a plurality of fuel assemblies 11A each including a plurality of fuels 11 are arranged side by side as shown in FIG. The cooling water W as a coolant flows from the bottom to the top through the vertical flow paths in the fuel assemblies 11A. When the density of the cooling water W fluctuates, the fluctuation propagates to the upper part of the flow path with a time delay, and the fluctuation of the thermal neutron flux density passing through the cooling water W is also changed from the lower part of the flow path to the upper part of the flow path. Propagate with time delay.

  As shown in FIGS. 2 and 6, a guide tube 13 of the LPRM 12 is disposed between the fuel assemblies 11A so as to extend in the vertical direction along the cooling water flow path. For example, four detectors 14 </ b> A to 14 </ b> D are fixedly arranged to detect the density of the thermal neutron flux passing through the cooling water W.

  However, in the apparatus of this embodiment, the cables 16A to 16D connected to the connector portions 15A to 15D below the lower end portion of the guide tube 13 of the signal cables from the four detectors 14A to 14D are detected by the phase difference detection. The phase difference detection unit 1 is connected to the unit 1, and the phase difference detection unit 1 subtracts the phase of the lower detector signal from the phase of the upper detector signal for each pair of output signals from the cables 16A to 16D. To obtain the phase difference. Further, the coherence of the same set of signals is obtained and, for example, the average value of the phase difference in the frequency band in which the coherence value is sufficiently high is evaluated. Detect phase difference due to propagation.

  The detection result of the phase difference is sent from the phase difference detection unit 1 to the connection state determination unit 3. Here, the four detectors 14A to 14D output signals with a time delay sequentially from the bottom to the top of the detector 14A at the bottom of the core, that is, in the order of the detectors 14B, 14C, and 14D. Therefore, if the cables 16A to 16D are correctly connected to the connector portions 15A to 15D below the lower end of the guide tube 13, the output signals of those cables 16A to 16D are sent from the bottom of the core as illustrated in FIG. The cable 16B connected to the second detector 14B has a phase difference sequentially from bottom to top, that is, in the order of the cables 16C and 16D connected to the detectors 14C and 14D, respectively. Here, as illustrated in FIG. 3, only the output signal of the cable 16A shows a change independent of the other cables 16B, 16C, and 16D, which is the core of the boiling water reactor to which the cable 16A is connected. In the vicinity of the detector A installed at the bottom, since the nuclear reaction has not yet occurred sufficiently, the neutron flux density is very low, and the noisy signal component unrelated to the behavior of neutrons is dominant. is there.

  Normally, the gas phase velocity of the core part is about 7 m / s and the core length is less than 4 m. Therefore, the time for the above-described fluctuation of the void amount to pass through the core part is less than about 0.6 seconds. Since it is sufficiently shorter than about 2 seconds or more of the period that is the reciprocal of the obtained frequency band, the output signal is delayed by about one period between the bottom detector 14A and the top detector 14D. Because there is no, there is no misjudgment of delay and advance.

  Moreover, in the apparatus of this embodiment, the cables 16A to 16D connected to the connector portions 15A to 15D below the lower end portion of the guide tube 13 of the signal cables from the four detectors 14A to 14D are subjected to the signal correlation evaluation. The signal correlation evaluation unit 2 is connected to the unit 2 and obtains the correlation of the signals for each pair of the cables 16A to 16D.

  Common indexes for evaluating the correlation between two signals selected from each signal output from each detector include, for example, covariance, correlation coefficient, cross correlation function, cross spectrum, coherence, and the like. The covariance is an average value of products of deviations from the average value of each signal in the two signals, and indicates that there is no correlation when the value is 0, but the original signal when the value is other than 0. Since the value changes depending on the value, general interpretation is difficult. The correlation coefficient is normalized to be a value of −1 to +1 by dividing the covariance between two signals by the product of the standard deviation of each signal, and when the value is close to −1 Indicates that the negative correlation is strong, the value is close to 0, the correlation is low, and the value is close to 1, the positive correlation is strong. The cross-correlation coefficient is an index that expresses the displacement of the correlation coefficient between two signals as a function of time. For example, when there is a phase difference between two signals, one signal is divided by the corresponding time. The cross-correlation coefficient is maximized when shifted by a distance. The cross spectrum is a frequency component obtained when the cross-correlation function is Fourier-transformed and is an index for observing the correlation between two signals on the frequency. And difficult to interpret. Coherence is a standardized handling and interpretation of the cross spectrum. When the value is 0, there is no correlation, and when the value is 1, there is a strong correlation. Any of the above can be used to evaluate the correlation between the two signals used in the present invention. However, it is preferable to use a correlation coefficient and coherence that are easy to handle and interpret the value indicating the correlation, and use coherence. Is more preferable.

  FIGS. 4A to 4C are explanatory diagrams illustrating an aspect in which the signal correlation evaluation unit 2 of the above embodiment evaluates the correlation between two signals by coherence. In FIG. 4, the horizontal axis represents frequency, and the vertical axis represents coherence. Curve 21 is cable 16A and cable 16B, curve 22 is cable 16A and cable 16C, curve 23 is cable 16A and cable 16D, and curve 24 is cable 16B and cable. 16C, a curve 25 indicates the coherence in the combination of the cable 16B and the cable 16D, and a curve 26 indicates the coherence in each combination of the cable 16C and the cable 16D. 4A to 4C show a case where the cables 16A to 16D are normally connected.

  As apparent from the curves 21 to 23 in FIGS. 4A to 4C, the combinations of the cables connected to the cable 16A, that is, the cables 16A and 16B, the cables 16A and 16C, and the cables 16A and 16D. The coherence of the combination is very small. This is because the neutron flux density is very low around the detector A installed at the bottom of the core of the boiling water reactor to which the cable 16A is connected. This is because an irrelevant noise-like signal component is dominant, and the correlation with a signal at a high neutron density around the detectors B, C, D is low.

  Moreover, in this embodiment, the coherence of each combination of the cable 16A to the cable 16D connected to each detector was evaluated by a frequency integral value. That is, as shown in FIGS. 4A to 4C, the coherence of the combination of the cable 16B and the cable 16C is the area S1, the coherence of the combination of the cable 16C and the cable 16D is the area S2, and the cable 16B and the cable 16D. The coherence of the combination is an area S3, and their sizes are S1> S2> S3.

  The coherence obtained in this way is sent from the signal correlation evaluation unit 2 to the connection state determination unit 3.

  Based on the phase difference sent from the phase difference detector 1 and the coherence sent from the signal correlation evaluator 2, the connection state determiner 3 determines the connection states of the cables 16A to 16D according to the following three steps. To do.

(1) Connection state determination for the cable 16A As described above, when the cable A is normally connected, the coherence of the combination with the cable 16A becomes very small, so conversely, the cable 16A and the cable 16B, When at least one of the combinations of the cable 16A and the cable 16C and the cable 16A and the cable 16D indicates a large coherence, the connection state determination unit 3 determines that the cable 16A is erroneously connected, and the erroneous connection is The determination result that there is is sent to the determination result output unit 4.

(2) Connection state determination of the cables 16B, 16C, and 16D when the cable 16A is determined to be normally connected When the connection state determination unit 3 determines that the cable 16A is normally connected, the coherence shown in FIG. Based on the correspondence table between the phase difference mode and the erroneous connection mode, the presence / absence of erroneous connection is determined. The cable 16A to cable 16D are arranged in a total of 24 ways, but when the cable 16A is determined to be normally connected, as shown in FIG. 5, it is limited to 6 ways of normal connection and erroneous connections 1 to 5. What is necessary is just to determine about these six ways. In FIG. 5, A, B, C, and D in the “LPRM arrangement” column indicate the arrangement order of the cables 16A, 16B, 16C, and 16D, and are AB, A-C, A-D, and B-. For C, BD, and CD, the combinations of cable 16A and cable 16B, cable 16A and cable 16C, cable 16A and cable 16D, cable 16B and cable 16C, cable 16B and cable 16D, cable 16C and cable 16D, respectively As for the phase difference, (−) indicates that the D signal is delayed with respect to B, and (+) indicates that the D signal is advanced with respect to B.

  Here, the signals output from the two adjacent cables excluding the combination with the cable 16A at the time of normal connection, that is, BC and CD have high coherence because the detectors are relatively close to each other. Classifies the cable combinations exhibiting these large coherences into the first group, and each of the cable combinations exhibiting a smaller coherence than the first group, ie, AB, AC, AD, BD, respectively. Grouping is performed to classify the combinations into group 2.

  In the case of erroneous connections 1 to 5, the combinations of the cables 16A to 16D in FIG. 5 are similarly grouped into the first group and the second group, and the cables 16A to 16D in FIG. When at least one of the combinations is different from the grouping at the time of normal connection, the connection state determination unit 3 determines that the cable 16A is erroneously connected, and the erroneous connection is detected. The determination result that there is is sent to the determination result output unit 4.

(3) When the classification by the first group and the second group of all combinations of the cables 16A to 16D in FIG. 5 is the same as the classification at the time of normal connection In the case of the erroneous connection 5 at the stage of (2) above, In other words, the LPRM arrangement is narrowed down to ADCB, but in BD, the normal phase difference is (−), but in the case of incorrect connection, it is (+). 3 determines that the cable 16A is erroneously connected, and sends a determination result that the cable 16A is erroneously connected to the determination result output unit 4.

  The determination result sent from the connection state determination unit 2 to the determination result output unit 4 according to the above (1) to (3) is displayed and output on a screen of a screen display device, for example.

  By the way, when the boiling reactor is started up, since the nuclear reaction around the detector A installed at the bottom of the core of the boiling water reactor is not sufficient, the magnitude of the coherence is BC, C- Focusing on the fact that D >> BD >> AB, AC, and AD, the coherence of BC and CD is set to the first group, BD, AB, and A−. The correspondence table shown in FIG. 5 is established by setting the coherence of C and AD to the second group. However, after the start-up of the boiling reactor has been completed and full-scale operation has begun, a nuclear reaction has sufficiently occurred around the detector A installed at the bottom of the core of the boiling water reactor and is connected to the cable 16A. Since the coherence of the cable combination to be increased also increases, the coherence becomes dependent on the distance between the detectors 14A to 14D, and the magnitude of the coherence is AB, BC, CD> BD , A-C> A-D, and it is impossible to make the determination as in (1) above, thereby making it impossible to narrow down the misconnection pattern into five patterns as shown in FIG. Therefore, it is possible to determine misconnection.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described examples, and can be appropriately changed within the scope of the claims. For example, in the method of the present invention, coherence is improved. Although the evaluation is based on the area, it may be evaluated by a coherence value at a specific frequency.

  According to the start-up LPRM signal cable misconnection determination method and apparatus of the present invention, whether the signal cable from the LPRM detector is misconnected is stored in the boiling reactor after the boiling water reactor reaches the criticality. Since it is determined at the time of start-up that is a period until the container is finally inspected, when it is determined that there is an incorrect connection, the boiling water reactor can be fully operated after the normal connection is restored.

DESCRIPTION OF SYMBOLS 1 Signal correlation evaluation part 2 Phase difference detection part 3 Connection state determination part 4 Determination result output part 10 Reactor pressure vessel 11 Fuel 11A Fuel assembly 12 LPRM
13 Guide tubes 14A-D Detectors 15A-D Connectors 16A-D Cable 21 Coherence between cable 16A and cable 16B at normal connection 22 Coherence between cable 16A and cable 16C at normal connection 23 Cable 16A at normal connection Coherence 24 with cable 16D Coherence between cable 16B and cable 16C at normal connection 25 Coherence between cable 16B and cable 16D at normal connection 26 Coherence between cable 16C and cable 16D at normal connection

Claims (4)

In determining an erroneous connection in signal cables from a plurality of detectors that are fixedly arranged at different heights in LPRM guide tubes installed in a pressure vessel of a boiling water reactor and detect thermal neutrons,
When starting up the boiling water reactor, all the signals output from the plurality of detectors are combined in two, and the correlation of the signals is evaluated for all the combinations,
At least one of a combination of a signal output from a detector installed at the bottom of the core of the boiling water reactor and a signal output from a detector other than the detector installed at the bottom of the core. If the combination shows a strong correlation, determine that there is a misconnection,
All combinations of signals output from detectors installed at the bottom of the core of the boiling water reactor and signals output from detectors other than the detector installed at the bottom of the core are weakly correlated. , The correlation of each signal output from two adjacent detectors other than the detector installed at the bottom of the core of the boiling water reactor is classified into a first group, The combinations showing weaker correlation than the first group are classified into the second group and grouped,
When the grouping by the first group and the second group for all the combinations is different in at least one classification compared to the grouping for all the combinations at the time of normal connection Determines that there is a misconnection,
Combinations in which the grouping by the first group and the second group for all the combinations is the same as the grouping for all the combinations at the time of normal connection and is classified into the second group Among them, when the phase delay of the signals output from the detectors other than the detectors arranged at the bottom of the core of the boiling water reactor does not sequentially occur in the upper detector with respect to the lower detector An LPRM signal cable incorrect connection determination method at startup, wherein it is determined that there is an incorrect connection.   2. The startup LPRM signal cable misconnection determination method according to claim 1, wherein the correlation is evaluated by coherence. In an apparatus for judging erroneous connection in signal cables from a plurality of detectors fixedly arranged at different heights in a guide tube of LPRM installed in a pressure vessel of a boiling water reactor and detecting thermal neutrons ,
Phase difference detection means for detecting a phase difference in signals output from the plurality of detectors when the boiling water reactor is started up,
A signal correlation evaluation unit that evaluates the correlation of signals for all of the combinations of all the signals output from the plurality of detectors at the time of startup of the boiling water reactor,
At least one of a combination of a signal output from a detector installed at the bottom of the core of the boiling water reactor and a signal output from a detector other than the detector installed at the bottom of the core. If the combination shows a strong correlation, determine that there is a misconnection,
All combinations of signals output from detectors installed at the bottom of the core of the boiling water reactor and signals output from detectors other than the detector installed at the bottom of the core are weakly correlated. , A combination showing a strong correlation with signals output from two adjacent detectors other than the detector installed at the bottom of the core of the boiling water reactor is classified into a first group, The combinations showing weaker correlation than the first group among the combinations are classified into the second group and grouped.
When the grouping by the first group and the second group for all the combinations is different in at least one classification compared to the grouping for all the combinations at the time of normal connection Determines that there is a misconnection,
Combinations in which the grouping by the first group and the second group for all the combinations is the same as the grouping for all the combinations at the time of normal connection and is classified into the second group Among them, when the phase delay of the signals output from the detectors other than the detectors arranged at the bottom of the core of the boiling water reactor does not sequentially occur in the upper detector with respect to the lower detector A connection state determination means for determining that there is an erroneous connection;
Determination result output means for outputting a determination result made by the connection state determination means;
An LPRM signal cable erroneous connection determination device at the time of startup, comprising:   4. The startup LPRM signal cable erroneous connection determination device according to claim 3, wherein the signal correlation evaluation unit evaluates the correlation by coherence.

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