JP4413910B2 - Jet pump flow rate measurement method and device for pipe breakage - Google Patents

Description

This invention is for measuring a differential pressure between a diffuser of a jet pump and a lower plenum for measuring a flow rate of a jet pump that sends cooling water from an annulus portion in a pressure vessel of a boiling water reactor to a lower plenum . The present invention relates to a method for determining a breakage of a pipe disposed in an annulus portion from a diffuser, and a jet pump flow measurement pipe breakage determination apparatus used in the method.

In a boiling water reactor (BWR), as shown in FIG. 4, in a pressure vessel 1, a core 2, a support plate 3 that supports the core 2 from below, and a shroud 4 that surrounds the core 2 from the side. And a large number of large jet pumps 5 arranged around the shroud 4 so as to surround the shroud 4 and for sending the cooling water in the annulus 1a to the lower plenum 1b below the support plate 3. These jet pumps 5 are, as shown in detail in FIG. 5 for two of them, an upwardly opened suction port 5a for sucking cooling water, and an external pump into the pressure vessel 1 feeding a nozzle 5b to draw sent pressurized cooling water annulus portion 1a to the suction port in 5a is blown downward into the suction port in 5a, the cooling water sucked into the suction port within 5a to the lower plenum 1b Court head and a cone-shaped diffuser 5c.

In the boiling water reactor (BWR), as shown in FIGS. 4 and 5, in order to measure the flow rate of water sent by each jet pump 5, a small water pressure is taken out from the diffuser 5 c of each jet pump 5. The jet pump differential pressure gauge 8 corresponding to each jet pump 5 that measures the differential pressure between the bore pipe 6 and the small bore pipe 7 for taking out the water pressure in the lower plenum 1b and the water pressure taken out through the small bore pipes 6 and 7. And a small-diameter pipe 9 for extracting water pressure at a position 1c below the core 2 in the shroud 4 and small-diameter pipes 7 and 9 for detecting the differential pressure of each part in the pressure vessel 1 The differential pressure of the water pressure extracted by the support plate differential pressure gauge 10 that measures the differential pressure of the water pressure, the small-diameter pipe 11 that extracts the water pressure at the position 1d above the core 2 in the shroud 4, and the small-diameter pipes 9 and 11 measurement And the core differential pressure gauge 12 is provided that.

  Incidentally, in recent years, any of the small-diameter pipes 6 for taking out the water pressure in the diffuser 5c of the jet pump 5 is disposed in the annulus portion 1a from the diffuser 5c, for example, at a portion indicated by symbol BK in the figure. There are some events that are broken due to the influence of vibration during operation. If this event occurs during the operation of the reactor, it may be first detected as a change in signal level, but even in that case, it is not always clear from other causes. For this reason, it is necessary to confirm that the cause is the cut of the small-diameter pipe 6 by placing the underwater television camera in the pressure vessel 1 after stopping the reactor and opening the lid of the pressure vessel 1. is there.

  That is, conventionally, an event that the small-diameter pipe 6 for taking out the water pressure in the diffuser 5c of the jet pump 5 is broken during the operation of the nuclear reactor, and even if the signal level of the jet pump differential pressure gauge 8 changes, that is the cause. Is a failure of the small-diameter pipe 6 or other factors (for example, clogging of foreign matter into the small-diameter pipe 6). Because we had to prepare in consideration of the case, we could not always prepare for efficient inspection and repair work.

  Therefore, when a significant change appears in the flow rate level of the jet pump 5, it can be clearly determined whether or not the cause is a breakage in the small-diameter pipe 6 that takes out the water pressure in the diffuser 5c. Being able to confirm that the cutting event has not occurred repeatedly during operation was an issue that led to efficient operation and maintenance of the nuclear power plant.

SUMMARY OF THE INVENTION An object of the present invention is to advantageously solve the above-described problem, and a jet pump flow measurement pipe breakage determination method according to the present invention includes an annulus portion around a shroud surrounding a core in a boiling water reactor. For measuring the flow rate of a jet pump that sends cooling water from its annulus part to the lower plenum below the support plate that supports the core from below, the difference between the inside of the diffuser of the jet pump and the lower plenum A first differential pressure that is a differential pressure between the diffuser and the lower plenum when determining the breakage of the pipe disposed in the annulus portion from the diffuser among the pipes for measuring pressure; a second differential pressure is a differential pressure between the reactor core and the lower plenum in the shroud to measure respectively, the correlation between the first differential pressure and a second pressure difference that they measured And valence, when the correlation is observed, is characterized in determining that Setsuson pipe disposed within the annulus from the diffuser there.

The jet pump flow measurement pipe breakage determination device of the present invention used in the above method includes a first differential pressure gauge that measures a first differential pressure that is a differential pressure between the diffuser and the lower plenum, and the shroud. A second differential pressure gauge that measures a second differential pressure that is a differential pressure between the core in the core and the lower plenum, and a first differential pressure gauge and a second differential pressure gauge that are measured by the first differential pressure gauge. A breakage determining means that evaluates a correlation between the measured second differential pressure and determines that there is a breakage of a pipe disposed in the annulus portion from the diffuser when the correlation is found; It is characterized by comprising.

Since the flow rate of the jet pump is converted from the first differential pressure that is the differential pressure between the diffuser and the lower plenum of the jet pump, the differential pressure between the diffuser and the lower plenum is measured. If a pipe breaks from the diffuser into the annulus, the pipe is opened into the annulus at the cut, and should be the pressure difference between the diffuser and the lower plenum. The output signal of the first differential pressure gauge indicating the first differential pressure substantially indicates the differential pressure between the annulus portion and the lower plenum . In this case, since the annulus portion and the position above and below the core inside the shroud communicate with each other via the top of the shroud, the first differential pressure (the output signal of the first differential pressure gauge) is A significant correlation is shown between the second differential pressure (the output signal of the second differential pressure gauge), which is the differential pressure between the core in the shroud and the lower plenum , which has not been particularly correlated until then. It becomes like this.

  Therefore, according to the jet pump flow measurement pipe breakage determination method of the present invention, the difference between the first differential pressure measured by the first differential pressure gauge and the second differential pressure measured by the second differential pressure gauge. When the correlation is evaluated and the correlation is found, it is determined that the pipe disposed in the annulus from the diffuser is broken, so it is clearly determined whether or not the pipe is broken. can do.

  Further, according to the jet pump flow measurement pipe breakage judging device of the present invention, the breakage judging means has the first differential pressure measured by the first differential pressure gauge and the second difference measured by the second differential pressure gauge. When the correlation between the pressure and the pressure is evaluated and a correlation is seen, it is determined that the pipe disposed in the annulus portion is broken from the diffuser, so whether or not the pipe is broken. Can be automatically and clearly determined.

  In the present invention, a coherence value may be used as an index for the correlation evaluation.

Also. In the present invention, the second differential pressure may be a differential pressure between a portion of the shroud below the core and the lower plenum .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the jet pump flow measurement pipe breakage determination method of the present invention and the configuration of the jet pump flow measurement pipe breakage determination apparatus of the present invention used therein, and FIG. FIG. 3 is a flowchart showing how to obtain a coherence value when the jet pump flow measurement pipe breakage determination apparatus of the embodiment determines a breakage based on the method of the embodiment, and FIG. 3 shows the jet pump flow measurement of the embodiment. It is a color photograph which shows the graph which illustrates the change state of a coherence value in case a pipe breakage determination apparatus determines with a cut based on the method of the said Example.

  The jet pump flow measurement pipe breakage judgment device of this embodiment is provided in the same nuclear reactor as the conventional one shown in FIGS. 4 and 5, and in FIG. 1 and FIG. Similar parts are denoted by the same reference numerals.

That is, the boiling water reactor (BWR) provided with the jet pump flow measurement pipe breakage determination device of this embodiment is also provided in the pressure vessel 1 with the core 2 and the figure as shown in FIGS. Although not shown in FIG. 1, a support plate 3 that supports the core 2 from below, a shroud 4 that surrounds the core 2 from the side, and an annulus that surrounds the shroud 4 in an annulus portion 1 a around the shroud 4. A large number of large-scale jet pumps 5 for sending the cooling water in the section 1a to the lower plenum 1b below the support plate 3 are provided. These jet pumps 5 are suction ports opened upward for sucking the cooling water. 5a, a nozzle 5b for blowing the pressurized water sent from the external pump into the pressure vessel 1 downward into the suction port 5a and drawing the cooling water in the annulus portion 1a into the suction port 5a, and the suction port The cooling water sucked into a and a diffuser 5c frusto conical sent to the lower plenum 1b.

In this boiling water reactor, in order to measure the flow rate of the water sent by each jet pump 5, the small-diameter pipe 6 for taking out the water pressure in the diffuser 5c of each jet pump 5 and the water pressure in the lower plenum 1b are used. A jet corresponding to each jet pump 5 as a first differential pressure gauge that measures the differential pressure between the small-diameter pipe 7 to be taken out and the water pressure taken out by the small-diameter pipes 6 and 7 as the first differential pressure. A pump differential pressure gauge 8 is provided, and a small-diameter pipe 9 for taking out water pressure at a position 1c below the core 2 in the shroud 4 in order to detect the differential pressure of each part in the pressure vessel 1, and in this embodiment A support plate differential pressure gauge 10 as a second differential pressure gauge for measuring the differential pressure of the water pressure taken out by the small-diameter pipes 7 and 9 as the second differential pressure, and a position 1d above the core 2 in the shroud 4 Take out the water pressure of There are provided a core pipe 11 and a core differential pressure gauge 12 for measuring the differential pressure of the water pressure taken out by the small diameter pipes 9, 11. These jet pump differential pressure gauge 8, support plate differential pressure gauge 10, and core differential pressure gauge 12 Constitutes the measurement system 13.

  In this boiling water reactor, the analog differential pressure signals respectively measured by the jet pump differential pressure gauge 8, the support plate differential pressure gauge 10, and the core differential pressure gauge 12 of the measurement system 13 are converted into digital signals at a high frequency. As a data recording processing device for recording substantially continuously, for example, a transient phenomenon recording device 14 having a hard disk drive device, and from the transient phenomenon recording device 14 in this embodiment, a differential pressure signal and a support plate of the jet pump differential pressure gauge 8 There is provided a data analysis device 15 constituted by a normal personal computer as a breakage determination means for reading and analyzing the differential pressure signal of the differential pressure gauge 10 as digital data. Therefore, in this embodiment, the jet pump differential pressure gauge 8, the support plate differential pressure gauge 10, and the data analysis device 15 constitute a jet pump flow measurement pipe breakage determination device.

In this boiling water reactor, the flow rate of each jet pump 5 is measured in terms of the first differential pressure that is the differential pressure between the diffuser 5c of the jet pump 5 and the lower plenum 1b. Of the pipes 6 and 7 for measuring the differential pressure between the diffuser 5c and the lower plenum 1b, a portion of the small-diameter pipe 6 for taking out the water pressure in the diffuser 5c from the diffuser 5c into the annulus portion 1a. When a cut occurs, the pipe 6 is opened into the annulus portion 1a at the cut portion , and the jet pump showing the first differential pressure that should be the differential pressure between the diffuser 5c and the lower plenum 1b. The output signal of the differential pressure gauge 8 substantially indicates the differential pressure between the annulus portion 1a and the lower plenum 1b.

In this case, since the annulus portion 1a and the position above and below the core 2 inside the shroud 4 communicate with each other via the top of the shroud 4, the first differential pressure (jet pump differential pressure gauge 8 Output signal) is a second differential pressure (output signal of the support plate differential pressure gauge 10), which is a differential pressure between the lower portion of the core 2 in the shroud 4 and the lower plenum 1b, which has not been particularly correlated until then. A significant correlation is exhibited.

  However, in the jet pump flow measurement pipe breakage determination method of this embodiment, the data analysis device 15 that forms a part of the jet pump flow measurement pipe breakage determination apparatus of this embodiment is based on a program given in advance. The first differential pressure that is an output signal of the jet pump differential pressure gauge 8 and the second differential pressure that is an output signal of the support plate differential pressure gauge 10 are frequently transmitted from the transient recording device 14 (for example, at intervals of several tens of milliseconds). When the correlation between the first differential pressure and the second differential pressure is read out and a correlation of a predetermined level or more is found, the small-diameter pipe disposed in the annulus portion 1a from the diffuser 5c It is determined that there are 6 cuts.

  Here, the evaluation of the correlation between the first differential pressure and the second differential pressure can be performed, for example, by obtaining a coherence value by a procedure as shown in FIG. 2 and using it. First, in order to analyze the noise component of the time series signal x (t) representing the first differential pressure, for example, the time series signal is approximated as a sum of triangular waves (Fourier transform is performed).

  Next, a power spectral density distribution Px (f) corresponding to the time series signal x (t) is defined from the Fourier component X (f) by the following equation.

  Similarly, the power spectral density distribution Py (f) can be defined from the Fourier component Y (f) for other time series signals y (t) representing the second differential pressure, for example, and the cross spectral density distribution S is combined. (F) can also be defined.

  The coherence value Coh (f) is defined by the following equation using the above-described equation, and this is used as an index indicating the correlation.

FIG. 3 exemplifies the change state of the coherence value when the jet pump flow measurement pipe breakage determination device of this embodiment determines that there is breakage based on the jet pump flow measurement pipe breakage determination method of this embodiment. Specifically, among the 20 jet pumps 5 of JP-01 to JP-01, the coherence value of JP-16 indicated by the curve A in the figure is much larger than that of other jet pumps in the frequency region of 1 Hz or less. Yes. As is apparent from this figure, the data analysis device 15 has a coherence value of 0.5 or more, for example, in the region of the frequency 10 ⁻¹ Hz or lower with the coherence values 0.5 and 0.8 as threshold values, for example. If it is less than 0.8, there is a sign of cutting, and if the calculated coherence value is 0.8 or more, there is cutting, and if the calculated coherence value is less than 0.5, it is determined that there is no cutting. It can be automatically and clearly determined whether or not the small-diameter pipes 6 of the 20 jet pumps 5 of JP-01 to 20 are broken, including signs of breakage.

Although the present invention has been described based on the illustrated example, the present invention is not limited to the above-described example. For example, the cut determination unit has a correlation greater than a predetermined value using a correlation coefficient instead of using a coherence value. It may be evaluated whether or not .

  Thus, according to the jet pump flow measurement pipe breakage determination method and the apparatus used therefor according to the present invention, it is clearly determined whether or not the jet pump flow measurement pipe is broken even during the operation of the nuclear reactor. This makes it possible to start preparations for repairs and repairs without having to wait for underwater television camera shooting while the reactor is stopped.

  In addition, it can be confirmed periodically during operation of the reactor that the jet pump flow rate measurement piping is not broken.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows one Example of the jet pump flow measurement piping breakage determination method of this invention, and the structure of the jet pump flow measurement pipe breakage determination apparatus of this invention used there. It is a flowchart which shows how to obtain | require a coherence value in case the jet pump flow measurement piping breakage determination apparatus of the said Example determines a breakage based on the method of the said Example. It is a color photograph which shows the graph which illustrates the change state of a coherence value when the jet pump flow measurement piping breakage determination apparatus of the said Example determines with a breakage based on the method of the said Example. It is sectional drawing which shows the structure in the pressure vessel of a nuclear reactor. It is a perspective view which shows the jet pump in the said pressure vessel.

DESCRIPTION OF SYMBOLS 1 Pressure vessel 1a Annulus part 1b Lower plenum 1c Position below the core 1d Position above the core 2 Core 3 Support plate 4 Shroud 5 Jet pump 5a Inlet 5b Nozzle 5c Diffuser 6, 7, 9, 11 Small bore piping 8 Jet Pump differential pressure gauge 10 Support plate differential pressure gauge 12 Core differential pressure gauge 13 Measurement system 14 Transient phenomenon recording device 15 Data analysis device

Claims (4)

A jet pump that is provided in an annulus around a shroud surrounding a core in a pressure vessel of a boiling water reactor, and sends cooling water from the annulus to a lower plenum below a support plate that supports the core from below. Among the pipes for measuring the differential pressure between the diffuser of the jet pump and the lower plenum for the flow rate measurement of, when determining the breakage of the pipe disposed in the annulus portion from the diffuser,
Measuring a first differential pressure that is a differential pressure between the diffuser and the lower plenum, and a second differential pressure that is a differential pressure between the core and the lower plenum in the shroud ,
The correlation between the measured first differential pressure and the second differential pressure is evaluated, and when the correlation is found, it is determined that there is a breakage in the pipe disposed in the annulus portion from the diffuser. A jet pump flow rate measurement method for determining pipe breakage.   The jet pump flow measurement pipe breakage determination method according to claim 1, wherein a coherence value is used as an index for the evaluation of the correlation. 3. The jet pump flow measurement pipe breakage determination method according to claim 1, wherein the second differential pressure is a differential pressure between a portion of the shroud below the core and the lower plenum . A first differential pressure gauge that measures a first differential pressure that is a differential pressure between the diffuser and the lower plenum ;
A second differential pressure gauge that measures a second differential pressure that is a differential pressure between the core in the shroud and the lower plenum ;
The correlation between the first differential pressure measured by the first differential pressure gauge and the second differential pressure measured by the second differential pressure gauge is evaluated, and when a correlation is found, the diffuser determines the annulus. A breakage judging means for judging that there is a breakage of the pipe disposed in the section;
A jet pump flow rate measurement pipe breakage judging device used in the jet pump flow rate measurement pipe breakage judgment method according to any one of claims 1 to 3.