Core flow rate measurement device and core flow rate measurement method for advanced boiling water reactor

Abstract

To easily detect the actual rotational speed of a reactor internal pump to measure the core flow rate.SOLUTION: A core flow rate measurement device 10 for an advanced boiling water reactor in which a plurality of reactor internal pumps 4 serving as reactor recirculation pumps are installed in a reactor pressure vessel 2 which is disposed inside a reactor containment vessel 1 and houses a core 3, and which measures the flow rate of coolant flowing to the core by the reactor internal pumps as the core flow rate, includes: current measurement means 11 which is disposed outside the reactor containment vessel 1 and measures a current supplied to a drive motor 4A of the reactor internal pump; pump rotation speed detection means 12 which is disposed outside the reactor containment vessel 1 and detects the actual rotational speed of the reactor internal pump by analyzing the current measured by the current measurement means 11; and core flow rate calculation means 13 which is disposed outside the reactor containment vessel 1 and calculates the core flow rate by using the actual rotational speed detected by the pump rotation speed detection means 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a core flow rate measuring device for an advanced boiling water reactor and a method for measuring the core flow rate of an advanced boiling water reactor.

Background Art

[0002] In a boiling water type light water reactor including an advanced boiling water reactor (ABWR), the core flow rate is measured for core management. In particular, in the measurement of the core flow rate in an advanced boiling water reactor equipped with a reactor internal pump (RIP), there are known methods for calculating the core flow rate from the measurement results of the core support plate differential pressure, and measurement methods by calculation using the relationship between the flow rate and differential pressure of the reactor internal pump, pump head, pump rotation speed, feed water flow rate, and feed water entropy, etc.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the measurement of the core flow rate, various improvements have been proposed to improve its accuracy and response (Patent Documents 1 and 2). In addition, a method has been proposed for measuring the discharge flow rate of the reactor internal pump with an ultrasonic flow meter regardless of the relationship between the flow rate and differential pressure of the reactor internal pump, pump head, and pump rotation speed, etc. (Patent Document 3).

[0005] In Patent Document 3 among these, when an ultrasonic probe is installed on the main body of an in-reactor pump and the discharge flow rate of the in-reactor pump is measured using ultrasonic waves to thereby measure the core flow rate, since the ultrasonic probe and cables are arranged inside the reactor containment vessel, radiation shielding such as lead seals is required for the ultrasonic probe and the like, and wiring inside the reactor containment vessel is also necessary. Further, in order to lead this cable to the central control room, penetrations through the reactor containment vessel, wiring inside the reactor building, power amplifiers, and other circuits are required. These works require a great deal of man-hours and costs, and also require parts costs and calibration costs as annual maintenance costs for equipment maintenance, and man-hours for work also occur.

[0006] Furthermore, the ultrasonic probe installed on the in-reactor pump requires regular maintenance and replacement in case of failure, and for this reason, the number of days for periodic inspections increases, which may hinder the improvement of the operating rate of the nuclear power plant.

[0007] Incidentally, during operation, the inside of the reactor containment vessel of a boiling water reactor light water reactor is filled with radiation and nitrogen, so even if a failure occurs in the ultrasonic probe, circuit, wiring, etc. inside the reactor containment vessel described above, it is impossible to perform repairs or the like without stopping the nuclear power plant.

[0008] The embodiment of the present invention has been made in consideration of the above circumstances, and an object thereof is to provide a core flow rate measurement device for an improved boiling water reactor and an improved boiling water reactor core flow rate measurement method capable of easily detecting the actual rotational speed of an in-reactor pump and measuring the core flow rate.

Means for Solving the Problems

[0009] In the core flow rate measuring device of the improved boiling water reactor according to an embodiment of the present invention, a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and accommodating a reactor core, and the flow rate of coolant flowing into the reactor core by this reactor internal pump is measured as the core flow rate. In the core flow rate measuring device of the improved boiling water reactor, current measuring means installed outside the reactor containment vessel and measuring the current supplied to the drive motor of the reactor internal pump, pump rotation speed detecting means installed outside the reactor containment vessel and analyzing the current measured by the current measuring means to detect the actual rotation speed of the reactor internal pump, and core flow rate calculating means installed outside the reactor containment vessel and calculating the core flow rate using the actual rotation speed detected by the pump rotation speed detecting means are provided, and it is characterized in that it is configured to have these components.

[0010] Further, in the core flow rate measuring device of the improved boiling water reactor according to an embodiment of the present invention, a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and accommodating a reactor core, and the flow rate of coolant flowing into the reactor core by this reactor internal pump is measured as the core flow rate. In the core flow rate measuring device of the improved boiling water reactor, current measuring means installed outside the reactor containment vessel and measuring the current supplied to the drive motor of the reactor internal pump, pump rotation speed detecting means installed outside the reactor containment vessel and analyzing the current measured by the current measuring means to detect the actual rotation speed of the reactor internal pump, core flow rate calculating means installed outside the reactor containment vessel and calculating the core flow rate using the actual rotation speed of the reactor internal pump, pump rotation speed measuring means provided with a sensor installed in the reactor internal pump and measuring the actual rotation speed of the reactor internal pump by this sensor, and switching means for selectively switching between the actual rotation speed from the pump rotation speed detecting means and the actual rotation speed from the pump rotation speed measuring means and inputting them to the core flow rate calculating means are provided, and it is characterized in that it is configured to have these components.

[0011] In the method for measuring the core flow rate of a modified boiling water reactor according to an embodiment of the present invention, a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and accommodating a reactor core, and the flow rate of the coolant flowing into the reactor core by this reactor internal pump is measured as the core flow rate. In the method for measuring the core flow rate of a modified boiling water reactor, a current measuring means installed outside the reactor containment vessel measures the current supplied to the drive motor of the reactor internal pump, a pump rotation speed detecting means installed outside the reactor containment vessel analyzes the current measured by the current measuring means to detect the actual rotation speed of the reactor internal pump, and a core flow rate calculating means installed outside the reactor containment vessel calculates the core flow rate using the actual rotation speed detected by the pump rotation speed detecting means. It is characterized by having the steps of.

Effects of the Invention

[0012] According to the embodiment of the present invention, the actual rotation speed of the reactor internal pump can be easily detected and the core flow rate can be measured.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. [A] First Embodiment (Figs. 1 to 3) Fig. 1 is a block diagram showing the configuration of a core flow rate measuring device for a modified boiling water reactor according to the first embodiment. In a modified boiling water reactor (ABWR) among boiling water reactors (light water boiling water reactors), a plurality (for example, ten) of reactor internal pumps 4 as reactor recirculation pumps are installed at the bottom of a reactor pressure vessel 2 installed in a reactor containment vessel 1 and accommodating a core 3, and a coolant circulates in the reactor pressure vessel 2 by this reactor internal pump 4.

[0015] Power (electric power) from the plant bus is supplied to the drive motor 4A of the reactor internal pump 4 through a power cable 8 passing through a penetration portion 9 of the reactor containment vessel 1 via a power receiving breaker 5, an input transformer 6, and an inverter 7. Electric power, particularly current, having a frequency corresponding to the required speed (required rotational speed) for the reactor internal pump 4 is adjusted and supplied to the drive motor 4A of the reactor internal pump 4 by the inverter 7.

[0016] The core flow rate measuring device 10 of the modified boiling water reactor of the first embodiment measures the flow rate of the coolant flowing into the core 3 by the reactor internal pump 4 in the reactor pressure vessel 2 as the core flow rate, and is configured to include a current measuring means 11, a pump rotational speed detecting means 12, and a core flow rate calculating means 13.

[0017] The current measuring means 11 is installed outside the reactor containment vessel 1 in the power cable 8 and measures the current supplied to the drive motor 4A of the reactor internal pump 4. Specifically, the current measuring means 11 measures the current supplied to the drive motor 4A as time series data capable of analyzing the frequency and noise present in this current by measuring the temporal change of the current by high-speed sampling. This current measuring means 11 may be installed not only in the power cable 8 but also in the output circuit of the inverter 7 or the like as long as it is outside the reactor containment vessel 1.

[0018] The pump rotation speed detection means 12 is installed outside the reactor containment vessel 1, and analyzes the current measured by the current measurement means 11 by spectrum analysis to detect the actual rotation speed of the reactor internal pump 4. This pump rotation speed detection means 12 is configured to include a spectrum calculation unit 14, a peak detection unit 15, and a rotation speed calculation unit 16, which will be described in detail later.

[0019] The core flow rate calculation means 13 is installed outside the reactor containment vessel 1, and uses the actual rotation speed of the reactor internal pump 4 detected by the pump rotation speed detection means 12 and other parameters to calculate the flow rate of the coolant flowing into the core 3 by the reactor internal pump 4 (core flow rate) in the reactor pressure vessel 2. The above other parameters include the pressure difference between the pump suction pressure and the core inlet pressure by the reactor internal pump 4, and the temperature of the coolant in the reactor pressure vessel 2.

[0020] The spectrum calculation unit 14 that constitutes the pump rotation speed detection means 12 calculates by converting the current measured by the current measurement means 11 into a spectrum 17 (Figure 2) by fast Fourier transform. The spectrum 17 shown in this Figure 2 has the horizontal axis representing the frequency and the vertical axis representing the magnitude of the frequency component (signal intensity or amplitude of the frequency component). Generally, the spectrum 17 obtained by fast Fourier transform has the magnitudes of the frequency components arranged at equal intervals (i.e., for each frequency with a predetermined resolution α) from 0 Hz to the maximum frequency in terms of processing.

[0021] Among the spectrum 17 shown in Figure 2, the vicinity of the power frequency component (i.e., the frequency component of the driving current) 18 is enlarged and shown in Figure 3. As shown in this Figure 3, the spectrum 17 includes the power frequency component 18 and the frequency components 19 and 20 of the sidebands that depend on the actual rotation speed of the reactor internal pump 4. These frequency components 19 and 20 of the sidebands are present on both sides of the power frequency component 18.

[0022] The peak detection unit 15 that constitutes the pump rotation speed detection means 12 shown in FIG. 1 analyzes the spectrum 17 calculated by the spectrum calculation unit 14, and detects the peak due to the power frequency component 18 and the peaks due to the frequency components 19 and 20 of the sidebands generated depending on the actual rotation speed of the reactor internal pump 4. Generally, since the maximum frequency component in the spectrum 17 is the power frequency component 18, the peak detection unit 15 can easily detect the peak of this power frequency component 18.

[0023] Various methods can be considered for searching for the peaks of the frequency components 19 and 20 of the sidebands that depend on the actual rotation speed of the reactor internal pump 4. For example, in the case of the reactor internal pump 4, when the number of poles of the drive motor 4A is P and the value of the power frequency component 18 is F (Hz), the approximate value of the frequency component corresponding to the actual rotation speed of the reactor internal pump 4 is represented by F±(2F / P) (Hz). Therefore, the peak detection unit 15 detects the maximum frequency component among the frequency components in the vicinity of this approximate value as the peaks of the frequency components 19 and 20 of the sidebands.

[0024] Here, the above-mentioned "vicinity" refers to the range of frequency components for obtaining the maximum value (peak) determined with reference to the resolution α of the frequency components of the spectrum 17. For example, the "vicinity" is preset so as to target a determined number of points (frequencies) before and after (larger or smaller) the calculated value of F±(2F / P) (Hz) in the spectrum 17 obtained by fast Fourier transform.

[0025] In addition, as the peaks of the frequency components 19 and 20 of the sidebands existing on both sides of the power frequency component 18, in addition to the actual rotation speed of the reactor internal pump 4, slip×number of poles (number of poles of the drive motor 4A), etc. are assumed. However, in order to exclude such slip×number of poles, etc., it is necessary to observe the spectrum 17 in advance and determine in advance which peak the peak detection unit 15 should detect.

[0026] Other methods for reasonably searching for the peaks of the frequency components 19 and 20 of the sideband waves are shown below. Since the reactor internal pump 4 is operated at a variable speed (rotation speed) according to a request from a reactor recirculation flow rate control system (not shown), the value F (Hz) of the frequency component (power supply frequency component 18) of the drive current supplied to the drive motor 4A of the reactor internal pump 4 is different each time. On the other hand, since the value Fr (Hz) of the frequency component (frequency component corresponding to the required rotation speed) corresponding to the rotation speed required for the reactor internal pump 4 can be easily obtained from the reactor recirculation flow rate control system, the value F´ (Hz) of the power supply frequency component 18 is calculated as F´ = Fr × 2 / P.

[0027] Therefore, the approximate value of the frequency component corresponding to the actual rotation speed of the reactor internal pump 4 is expressed as F´ ± (2F´ / P) (Hz) using the above value F´ (Hz), and the peak detection unit 15 detects the maximum frequency component from among the frequency components in the vicinity of this approximate value as the peaks of the frequency components 19 and 20 of the sideband waves.

[0028] The rotation speed calculation unit 16 that constitutes the pump rotation speed detection means 12 shown in FIG. 1 reads the values Fs1 (Hz) and Fs2 (Hz) of the frequency components 19 and 20 of the sideband waves where the peak detected by the peak detection unit 15 exists from the spectrum 17, and the value Fs (Hz) of the frequency component (frequency component corresponding to the actual rotation speed) corresponding to the actual rotation speed of the reactor internal pump 4 is calculated as Fs = F - Fs1 or Fs = Fs2 - F, or Fs = F´ - Fs1 or Fs = Fs2 - F´. Further, the rotation speed calculation unit 16 calculates the actual rotation speed of the reactor internal pump 4 from the value Fs (Hz) of the frequency component corresponding to the actual rotation speed calculated as described above.

[0029] Note that the resolutions of the values F, F' of the power frequency component 18, the values Fs1, Fs2 of the sideband frequency components 19, 20, and the value Fs of the frequency component corresponding to the actual rotation speed of the reactor internal pump 4, which are obtained by the pump rotation speed detection means 12, are subject to the constraint of the resolution α of the spectrum 17 shown in FIGS. 2 and 3. However, by setting a long data acquisition time (period) for calculating the spectrum 17 in the current measurement means 11 and the spectrum calculation unit 14, within the constraint range of the hardware and software of the current measurement means 11 and the spectrum calculation unit 14, it is possible to improve the resolutions of the above-mentioned values F, F', Fs1, Fs2, and Fs respectively.

[0030] In the core flow rate measurement device 10 of the improved boiling water reactor configured as described above, the current measurement means 11 installed outside the reactor containment vessel 1 measures the current supplied to the drive motor 4A of the reactor internal pump 4, and the pump rotation speed detection means 12 installed outside the reactor containment vessel 1 spectrum-analyzes the current measured by the current measurement means 11 to detect the actual rotation speed of the reactor internal pump 4. The core flow rate calculation means 13 installed outside the reactor containment vessel 1 calculates the core flow rate using the actual rotation speed detected by the pump rotation speed detection means 12 and the like. By sequentially performing these steps, the core flow rate of the coolant flowing from the inside of the reactor pressure vessel 2 toward the core 3 is measured.

[0031] Since it is configured as described above, according to the first embodiment, the following effect (1) is achieved. (1) The current measurement means 11 and the pump rotation speed detection means 12 constituting the core flow rate measurement device 10 of the improved boiling water reactor are installed outside the reactor containment vessel together with the core flow rate calculation means 13. Therefore, in particular, the construction of the current measurement means 11 and the pump rotation speed detection means 12 is inexpensive, and their maintenance can be easily performed. As a result, the actual rotation speed of the reactor internal pump 4 can be easily detected by the current measurement means 11 and the pump rotation speed detection means 12, and the core flow rate can be calculated and measured by the core flow rate calculation means 13 using this actual rotation speed.

[0032] [B]Second Embodiment (FIG. 4) FIG. 4 is a block diagram showing the configuration of the core flow rate measuring device of the improved boiling water reactor according to the second embodiment. Regarding the parts similar to those in the first embodiment in this second embodiment, the same reference numerals as those in the first embodiment are given to simplify or omit the description.

[0033] The difference between the core flow rate measuring device 25 of the improved boiling water reactor of this second embodiment and the first embodiment is that pump rotation speed measuring means 26 for measuring the actual rotation speed of the reactor internal pump 4 by a speed sensor 28 installed in the reactor internal pump 4 is installed in parallel with the pump rotation speed detecting means 12 of the first embodiment, and a switching means 27 for alternately switching the actual rotation speed of the reactor internal pump 4 from the pump rotation speed measuring means 26 and the actual rotation speed of the reactor internal pump 4 from the pump rotation speed detecting means 12 and inputting them to the core flow rate calculating means 13 is provided.

[0034] The speed sensor 28 in the pump rotation speed measuring means 26 is installed in a hole drilled in the casing of the reactor internal pump 4. Further, a notch is machined on the shaft of the reactor internal pump 4. The speed sensor 28 outputs an electrical signal in response to the passage of the notch on the rotating shaft during the operation of the reactor internal pump 4. This electrical signal reaches a converter 30 installed in the reactor containment vessel 1 through a signal cable 29, and further reaches a power unit 32 installed outside the reactor containment vessel 1 through the signal cable 29 passing through the penetration portion 31 of the reactor containment vessel 1. The converter 30 and the power unit 32 perform signal processing on these signals to obtain a rotation speed signal for measuring the actual rotation speed of the reactor internal pump 4. The pump rotation speed measuring means 26 is constituted by having the above-described speed sensor 28, signal cable 29, converter 30, and power unit 32.

[0035] In the core flow rate calculation means 13 of the core flow rate measurement device 25 of the improved boiling water reactor, the core flow rate is calculated using either the actual rotation speed of the reactor internal pump 4 measured by the pump rotation speed measurement means 26 that is alternatively switched and input by the switching means 27 or the actual rotation speed of the reactor internal pump 4 detected by the pump rotation speed detection means 12, along with other parameters and the like.

[0036] Since it is configured as described above, according to the second embodiment, when the switching means 27 causes the actual rotation speed of the reactor internal pump 4 from the pump rotation speed detection means 12 to be input to the core flow rate calculation means 13, in addition to the same effect as the effect (1) of the first embodiment, the following effect (2) is achieved.

[0037] (2) When the switching means 27 inputs the actual rotation speed of the reactor internal pump 4 measured by the pump rotation speed measurement means 26 to the core flow rate calculation means 13 and a failure occurs in the pump rotation speed measurement means 26 while the core flow rate calculation means 13 is calculating the core flow rate, the switching means 27 can cause the actual rotation speed of the reactor internal pump 4 detected by the pump rotation speed detection means 12 to be input to the core flow rate calculation means 13 and have the core flow rate calculation means 13 calculate the core flow rate.

[0038] Since the pump rotation speed detection means 12 is installed outside the reactor containment vessel 1 and detects the actual rotation speed of the reactor internal pump 4 by analyzing the current supplied to the drive motor 4A of the reactor internal pump 4, it is not necessary to repair the failed pump rotation speed measurement means 26 inside the reactor containment vessel 1. As a result, in response to a failure of the pump rotation speed measurement means 26, it is possible to quickly take measures using the inexpensive and simple pump rotation speed detection means 12, and the core flow rate of the coolant inside the reactor pressure vessel 2 can be continuously measured.

[0039] As described above, some embodiments of the present invention have been explained. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. Also, those replacements, changes, and combinations are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0040] 1... Reactor containment vessel, 2... Reactor pressure vessel, 3... Reactor core, 4... Reactor internal pump, 4A... Drive motor, 10... Core flow rate measuring device for an improved boiling water reactor, 11... Current measuring means, 12... Pump rotation speed detecting means, 13... Core flow rate calculating means, 14... Spectrum calculation unit, 15... Peak detection unit, 16... Rotation speed calculation unit, 17... Spectrum, 18... Power frequency component, 19, 20... Sideband frequency components, 25... Core flow rate measuring device for an improved boiling water reactor, 26... Pump rotation speed measuring means, 27... Switching means, 28... Speed sensor

Claims

1. In a core flow rate measuring device for a modified boiling water reactor in which a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and housing a reactor core, and the flow rate of coolant flowing into the reactor core by the reactor internal pumps is measured as the core flow rate, current measuring means installed outside the reactor containment vessel for measuring the current supplied to the drive motor of the reactor internal pump; pump rotation speed detecting means installed outside the reactor containment vessel for analyzing the current measured by the current measuring means to detect the actual rotation speed of the reactor internal pump; core flow rate calculating means installed outside the reactor containment vessel for calculating the core flow rate using the actual rotation speed detected by the pump rotation speed detecting means, characterized in that it is configured to have. A core flow rate measuring device for a modified boiling water reactor.

2. In a core flow rate measuring device for a modified boiling water reactor in which a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and housing a reactor core, and the flow rate of coolant flowing into the reactor core by the reactor internal pumps is measured as the core flow rate, current measuring means installed outside the reactor containment vessel for measuring the current supplied to the drive motor of the reactor internal pump; pump rotation speed detecting means installed outside the reactor containment vessel for analyzing the current measured by the current measuring means to detect the actual rotation speed of the reactor internal pump; core flow rate calculating means installed outside the reactor containment vessel for calculating the core flow rate using the actual rotation speed of the reactor internal pump; pump rotation speed measuring means provided with a sensor installed in the reactor internal pump, and measuring the actual rotation speed of the reactor internal pump by this sensor; switching means for selectively switching the actual rotation speed from the pump rotation speed detecting means and the actual rotation speed from the pump rotation speed measuring means and inputting them to the core flow rate calculating means, characterized in that it is configured to have. A core flow rate measuring device for a modified boiling water reactor.

3. The pump rotation speed detecting means includes a spectrum calculation unit that converts the current measured by the current measuring means into a spectrum and calculates it. A peak detection unit that analyzes the spectrum calculated by the spectrum calculation unit and detects a peak due to a frequency component that occurs depending on the actual rotation speed of the reactor internal pump; A method for measuring the core flow rate of an improved boiling water reactor according to claim 1 or 2, characterized in that it comprises a calculated rotation speed calculation unit that reads the frequency component where the peak detected by the peak detection unit exists and calculates the actual rotation speed of the reactor internal pump.

4. In a method for measuring the core flow rate of an improved boiling water reactor, in which a plurality of reactor internal pumps are installed as reactor recirculation pumps in a reactor pressure vessel installed in a reactor containment vessel and accommodating a reactor core, and the flow rate of the coolant flowing into the reactor core by the reactor internal pump is measured as the core flow rate, A step of measuring, by current measurement means installed outside the reactor containment vessel, the current supplied to the drive motor of the reactor internal pump; A step of detecting, by pump rotation speed detection means installed outside the reactor containment vessel, the actual rotation speed of the reactor internal pump by analyzing the current measured by the current measurement means; A method for measuring the core flow rate of an improved boiling water reactor, characterized by comprising a step of calculating the core flow rate by core flow rate calculation means installed outside the reactor containment vessel using the actual rotation speed detected by the pump rotation speed detection means.

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