JP2013113646A - Reactor vibration monitoring apparatus and reactor vibration monitoring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor vibration monitoring apparatus and a reactor vibration monitoring method for monitoring minute relative vibrations among pieces of equipment to evaluate soundness and abnormality of the equipment inside a reactor pressure vessel.SOLUTION: Ultrasound oscillated by one ultrasonic sensor is radiated to a plurality of pieces of equipment producing relative vibrations, reflection waves from the equipment are processed, and the relative vibrations are calculated. The relative calculations may be calculated on the basis of detection time differences of the respective reflection waves.

Description

  The present invention relates to a reactor vibration monitoring apparatus and a reactor vibration monitoring method for monitoring the vibration state of in-reactor equipment such as a jet pump installed in a pressure vessel of a nuclear reactor.

  Taking the case of a general boiling water reactor (BWR) as an example, the internal structure of the RPV and the jet pump will be described. FIG. 1 is a schematic sectional view of a reactor pressure vessel (RPV) 101 for a boiling water reactor (BWR). The RPV 101 has a generally cylindrical shape and is closed by a bottom head 102 at one end and a removable top head 103 at the other end.

  Inlet nozzle 108 extends through the sidewall of RPV 101 and is coupled to jet pump 109. When the jet pump 109 is installed, a larger amount of cooling water than the amount of cooling water drawn out of the RPV 101 by the recirculation pump can be supplied to the core 105. Furthermore, by controlling the flow rate of the core 105, it is possible to control the output by utilizing the change in the reactivity due to the void effect (the effect that the density of cooling water decreases due to the generation of bubbles and the reactivity of the reactor decreases). Is possible.

  FIG. 2 shows a front view of the jet pump, and the structure of the jet pump 109 will be described. In FIG. 2, 201 is a riser elbow, 202 is a riser tube, 203 is a transition piece, 204 is an elbow, 110 is a nozzle, 111 is a throat, 112 is a diffuser, 205 is a bracket, 206 is a support, 207 is a wedge, 208 is a riser brace It is. The throat 111 and the diffuser 112 are connected by a slip joint 209 and have a gap 210. When there is a pressure difference between the inside and outside of the slip joint 209, a cooling fluid flows through the gap 210. Further, the flow direction of the driving fluid 211 is changed by about 180 ° by the elbow 204 after the riser pipe 202 is raised. At this time, a jet pump beam 212 (beam) is attached to resist the fluid reaction force applied to the elbow 204.

  As described above, the jet pump is a device that can be affected by fluid vibration because it has a high-speed flow and mixed flow inside and a leak flow from the gap 210 of the slip joint. In order to ensure the long-term soundness of the jet pump, it is necessary to monitor and evaluate the vibration state of the jet pump. A jet pump is an example of equipment to be evaluated in this way.

For example, Patent Literatures 1 to 3 disclose this vibration monitoring method and apparatus.
For example, in Patent Document 1, an ultrasonic sensor is installed on the outer surface of a pressure vessel, an ultrasonic pulse is transmitted to the jet pump via the pressure vessel or reactor water, the ultrasonic velocity of the pressure vessel, the ultrasonic velocity of the reactor water, Reactor vibration monitoring that measures the change in the propagation time of ultrasonic waves to determine the vibration amplitude of the reactor internals based on the thickness of the pressure vessel and the distance between the pressure vessel and the reactor internals An apparatus is disclosed.

  Further, in Patent Document 2, a reflection surface having a planar shape capable of reflecting ultrasonic waves on the surface of an object to be monitored or a corner reflector having an orthogonal plane as a reflection surface is attached and reflected by the reflection surface of this reflector. A vibration / deterioration monitoring device that receives ultrasonic waves and measures the vibration displacement of a monitoring object is disclosed.

  Furthermore, in Patent Document 3, by detecting and reflecting reflected ultrasonic pulses reflected from the inside of the reactor pressure vessel wall, vibration of an internal device having an inclination or curvature is detected without attaching a reflector. A nuclear reactor vibration monitoring device is disclosed.

Japanese Patent No. 3785559 Japanese Patent No. 4551920 JP 2011-133241 A

  Damage due to vibration is greatly affected by collision and wear due to relative vibration between devices. However, in general, relative vibration accompanying contact with other equipment has a smaller amplitude than vibration of a single device, and is more difficult to measure than vibration measurement of a single device.

  The above-described prior art discloses a technique for detecting vibration of a single device. When using conventional technology to measure the vibrations of multiple devices with multiple sensors and calculating the relative vibration by taking the difference, the accuracy decreases due to the ultrasonic path, strength, delay material characteristics, etc. of each sensor. Is concerned.

  The present invention is intended to solve the above-mentioned problems, and its purpose is to monitor reactor relative vibrations that monitor minute relative vibrations between devices in order to evaluate the soundness and abnormality of the devices in the reactor pressure vessel. It is to provide an apparatus and a reactor vibration monitoring method.

In order to achieve the above object, the present invention has at least the following features.
The present invention is characterized in that ultrasonic waves oscillated from one ultrasonic sensor are irradiated to a plurality of devices that perform relative vibration, reflected waves from the plurality of devices are processed, and the relative vibration is calculated.

The relative vibration may be calculated based on a detection time difference between the reflected waves.
Further, the reflected wave may be processed to calculate the vibration displacement of the reflecting surface.

Further, the range of the recording time of the reflected waveform may be determined based on the reflected waveform formed by each reflected wave.
Further, the transmission of the ultrasonic wave may be performed by one pulse or a plurality of continuous pulses.

The plurality of devices that vibrate relatively include a jet pump throat and diffuser, a jet pump wedge and bracket, or a jet pump throat and bracket.
Further, the presence / absence of an abnormality may be determined by comparing the calculated amplitude of the relative vibration with a threshold value obtained by prior analysis or evaluation at the time of manufacturing the device.

  Moreover, you may provide a reflector in at least 1 reflective surface among the reflective surfaces of the said some apparatus.

ADVANTAGE OF THE INVENTION According to this invention, in order to evaluate the soundness and abnormality of the apparatus in a reactor pressure vessel, the reactor vibration monitoring apparatus and reactor vibration monitoring method which monitor the minute relative vibration between apparatuses can be provided.

It is sectional drawing which shows the structure inside the boiling water reactor which concerns on embodiment of this invention. It is explanatory drawing of a jet pump. It is a figure explaining the Example of the reactor vibration monitoring apparatus which is this invention. It is a figure explaining the propagation path of the ultrasonic wave in the Example of the reactor vibration monitoring apparatus which is this invention. It is a figure explaining the received waveform in the Example of the reactor vibration monitoring apparatus which is this invention. It is a figure which shows the setting of the recording range of an ultrasonic wave in the Example of the reactor vibration monitoring apparatus which is this invention, and a vibration measuring method.

  An embodiment of the present invention will be described using a boiling water reactor as an example with reference to the drawings. FIG. 1 is a schematic sectional view of a reactor pressure vessel (RPV) 101 for a boiling water reactor (BWR). The RPV 101 has a generally cylindrical shape and is closed by a bottom head 102 at one end and a removable top head 103 at the other end. A core shroud (shroud) 104 generally surrounds the core 105 within the RPV 101. The shroud 104 has a substantially cylindrical shape and is supported by a shroud support structure 106. An annular space (annulus portion) 107 is formed between the cylindrical RPV 101 and the cylindrical shroud 104.

  Inlet nozzle 108 extends through the sidewall of RPV 101 and is coupled to jet pump 109. The cooling fluid (driving fluid) boosted by a recirculation pump (not shown) is ejected from the nozzle 110 and sucks the cooling fluid (driven fluid) of the annulus portion 107. The driving fluid and the driven fluid are mixed in the throat 111, the static pressure is recovered by the diffuser 112, which is a diffusion site, passes through the lower plenum 113, and is supplied to the core 105. When the jet pump 109 is installed, a larger amount of cooling water than the amount of cooling water drawn out of the RPV 101 by a recirculation pump (not shown) can be supplied to the core 105. Furthermore, by controlling the flow rate of the core 105, it is possible to control the output by utilizing the change in the reactivity due to the void effect (the effect that the density of cooling water decreases due to the generation of bubbles and the reactivity of the reactor decreases). Is possible. Steam generated in the core 105 becomes superheated steam by the separator 114 and the dryer 115, and drives a turbine (not shown) through the main steam nozzle 116. On the other hand, the water separated by the separator 114 and the dryer 115 is mixed with water returned to the reactor by a water supply system (not shown) in the annulus 107 and supplied again to the core 105 by the jet pump 109. Is done.

  FIG. 2 shows a front view of the jet pump, and the structure of the jet pump 109 will be described. In FIG. 2, 201 is a riser elbow, 202 is a riser tube, 203 is a transition piece, 204 is an elbow, 110 is a nozzle, 111 is a throat, 112 is a diffuser, 205 is a bracket, 206 is a support, 207 is a wedge, 208 is a riser brace It is. The throat 205 and the diffuser 112 are connected by a slip joint 209 and generally have a gap 210. When there is a pressure difference between the inside and outside of the slip joint 209, a cooling fluid flows through the gap 210. Further, the flow direction of the driving fluid 211 is changed by about 180 ° by the elbow 204 after the riser pipe 202 is raised. At this time, a jet pump beam 212 (beam) is attached to resist the fluid reaction force applied to the elbow 204.

  FIG. 3 is a diagram for explaining an embodiment of the reactor vibration monitoring apparatus of the present invention. As shown in FIG. 3, the embodiment includes an ultrasonic sensor 301, an ultrasonic transmission / reception unit 302, a coaxial line 303 connecting them, and an ultrasonic signal processing unit 304 that records and processes an ultrasonic reception waveform. Is done.

  The ultrasonic sensor 301 is attached to a position on the outer surface of the RPV 101 where the ultrasonic wave 305 efficiently hits a plurality of in-reactor devices 306A and 306B. There are two methods for attaching a heat-resistant ultrasonic sensor: a method in which a soft metal such as gold, silver or copper is sandwiched between them, or a method in which the sensor is physically attached with high-temperature adhesive, brazing or high-temperature solder. Any technique may be used as long as it is known and can transmit and receive ultrasonic waves stably even at high temperatures. When installing the ultrasonic sensor 301, the installation position may be determined by detecting a plurality of ultrasonic reflected waves reflected from the in-reactor devices 306A and 306B, and the temperature condition and measurement at the time of installation may be determined. Considering differences in temperature conditions, especially changes in the sound speed of the medium with respect to temperature changes, expansion and contraction due to temperature changes in the reactor equipment, etc., the ultrasonic propagation path under each temperature condition is analyzed in advance using simulation etc. Then, the installation position of the ultrasonic sensor 301 may be determined.

  A coaxial line 303 connecting the ultrasonic sensor 301 and the ultrasonic transmission / reception unit 302 is connected between the RPV 101 and the reactor containment vessel (PCV) 307, and is connected to the ultrasonic transmission / reception unit 302 through a wiring drawing hatch 308 of the PCV 307. The In this state, the ultrasonic wave 305 is transmitted from the ultrasonic sensor 301, and the transmitted ultrasonic wave 305 is reflected by the in-reactor devices 306 </ b> A and 306 </ b> B via the RPV 101 and the reactor water 309 and is received by the ultrasonic sensor 301 again. Is done.

  The received ultrasound echo is received as an electrical signal by the ultrasound transmitting / receiving unit 302, and the waveform is recorded over time. Here, if the in-reactor devices 306A and 306B vibrate in the horizontal direction on the paper surface, the propagation distance of the ultrasonic wave 305 changes with time. The time positions of the reflected waves (407A and 407B in FIG. 6 to be described later) stored with time in the ultrasonic signal processing unit 304 correspond to the vibration of the in-reactor devices 306A and 306B on the time axis. It changes (602A and 602B in FIG. 6). Since 1/2 of the product of the difference between the two reflected waves on the time axis and the sound speed of the reactor water corresponds to the relative distance between the in-reactor devices 306A and 306B, the change in the time difference is detected. It is possible to calculate the relative vibration (603 in FIG. 6 described later) of the in-furnace equipment. In addition, by performing a fast Fourier transform process (FFT) generally used for the time-varying vibration waveform of each reflected wave and the waveform of the relative vibration (602A, 602B, and 603), the vibration and the relative vibration of the monitoring target are performed. Can be obtained. The above is the embodiment and basic operation principle of the vibration state monitoring method according to the present invention.

  Next, the ultrasonic propagation path in the above embodiment will be described in detail with reference to FIG. In the embodiment, the monitoring target, that is, the ultrasonic reflection surface includes, for example, the throat 111 of the jet pump 109 and the outer surface of the diffuser 112. Other monitoring targets in the jet pump 109 include the outer surface of the wedge 207 and the bracket 205 or the outer surface of the throat 111 and the bracket 205.

  When ultrasonic waves are transmitted from the ultrasonic sensor 301 (ultrasonic element 301a) to this reflecting surface, the ultrasonic waves propagate through the front plate 401 inside the ultrasonic sensor 301, and the acoustic impedance (sound speed × density) between the front plate and the RPV 101. ) Propagates to the RPV 101 with a transmittance corresponding to the difference of), and reflects 403 into the front plate with a reflectance corresponding to the acoustic impedance. Similarly, the ultrasonic wave 402 propagated to the RPV 101 is divided into a transmitted wave 404 to the reactor water and a reflected wave 405 in the RPV. Here, the transmittance from the RPV 101 to the reactor water is as low as about 5% (3.5% at 300 ° C.) at room temperature because of the large difference in acoustic impedance, and the reflectance is 95% (96.5% at 300 ° C.). ) And higher. For this reason, most of the ultrasonic waves transmitted from the ultrasonic sensor 301 are subjected to multiple reflections within the RPV 101. For this reason, this multiple reflected wave 406 may become noise as reverberation.

  Furthermore, the ultrasonic wave 404 propagated into the reactor water reaches the in-reactor equipment 306A and 306B. In this embodiment, since there are two reflecting surfaces (in-reactor devices 306A and 306B), the reflected waves 407A and 407B from the two reflecting surfaces are timed by a time corresponding to twice the distance between the reflecting surfaces. And is received by the ultrasonic sensor 301 (ultrasonic element 301a) through a path opposite to the ultrasonic wave propagation path described so far. In the embodiment of the present invention, for example, if an ultrasonic wave of one wave (sine wave 1 cycle (sine wave single pulse)) is transmitted, the multiple reflected wave 406 in the RPV 101 is one cycle of sine wave. The reflected wave of the present embodiment is obtained as one cycle of two sine waves 407A and 407B shifted on the time axis, and the reflection reflected on the reflection surface from the ultrasonic signal including a plurality of reflected waves. It is possible to easily discriminate only the wave and specify the waveform to be recorded.

  The difference between the waveforms and the method for determining the waveform recording range will be described with reference to FIGS. FIG. 5 shows an outline of all waveforms recorded at the time when ultrasonic waves are transmitted and received by the ultrasonic sensor, and the case of the reflector of the prior art and the case of the embodiment of the present invention are compared. The waveform of the prior art shown in FIG. 5 is the same as that of the embodiment of the present invention in which the ultrasonic pulse is transmitted to a single device, the reflected wave is received and the vibration displacement of the single device is measured. The outline of all the waveforms when transmitting the ultrasonic wave of is shown. Further, as shown in FIG. 5, all the recorded waveforms include a plurality of waveforms 501 of the multiple reflected waves 406 in the RPV 101, and also a noise waveform 502 associated with the shape echo.

  In the case of the prior art, since the reflected wave 503 is processed from the monitoring target of a single device, the reflected waveform is a waveform corresponding to one wave similar to the multiple reflected wave waveform 501 and the noise waveform 502. It is difficult to specify the reflected wave 503. In particular, when a reflector such as a corner reflector is provided, the reflected waveform 503 is further specified when the multiple reflected wave waveform 501 and the noise waveform 502 are measured from a single device with the same intensity as the reflected waveform. Is difficult. In addition, as described above, when the temperature of the RPV and the reactor water in which the ultrasonic wave propagates changes, the sound speed also changes. Therefore, the time position of the reflected waveform 503 moves on the time axis, and the identification becomes more difficult. .

  On the other hand, when two reflecting surfaces in the embodiment of the present invention are used, a reflected waveform 407 having two reflected waves 407A and 407B is obtained from the reflecting surfaces of the two devices as shown in FIG. Will be. The time interval between the two reflected waves 407A and 407B corresponds to twice the distance between the two reflecting surfaces as described above. In addition, the multiple reflection waveform 501 in the RPV 101 and the noise waveform 502 accompanying the shape echo are independent single pulses, whereas the reflection waveform 407 in this embodiment is a pair with a constant interval on the time axis. Since it is a pulse and the waveform itself is different from the multiple reflection waveform 501 and the noise waveform 502, the identification is easy. Furthermore, even if the position of the two reflected waveforms 407 on the time axis changes due to a change in the sound speed of the medium accompanying a temperature change, it can be easily identified as long as there is no interference with multiple reflected waves or noise waves. is there. In addition, shape echo shows the reflected wave by the corner | angular part etc. of the reflective surface of an apparatus.

  In this embodiment, an example of transmitting ultrasonic waves for one wave (single pulse) is shown, but the present invention is not limited to one wave, and may be for two waves or more. In short, it is sufficient that the wave number is such that the reflection waveform is a pair of waveforms from the reflection surfaces of the two devices by one ultrasonic oscillation. Even in the case of multiple wavenumbers, the reflection waveform of the prior art has a waveform with a double wavenumber similar to the multiple reflection waveform 501 and the noise waveform 502, and it is difficult to specify the reflection waveform 503 from the device. Qualitatively, the smaller the distance between the two devices, the smaller the wave number.

  As shown in FIG. 5, after specifying the reflected waveform 407 having two reflected waves, as shown in the upper and middle diagrams of FIG. 6, the range including these two reflected waves 407A and 407B is exceeded. A sound wave recording range 601 is set, and a waveform is recorded over time. In this case, when the monitoring target vibrates, only these two reflected waves 407A and 407B, that is, only the reflected waveform 407, move to the left and right with the vibration on the time axis. The changes over time of the two reflected waves 407A and 407B are shown in 602A and 602B shown in the lower diagram of FIG. 6, respectively.

In addition, relative vibration is obtained by using the time difference (Δt) between the two reflected waves and the sound velocity Vw of the reactor water at the monitoring target portion to obtain the distance ΔH between the two reflecting surfaces from the equation (1), and the change with time. It can be obtained by calculating. A change 603 of the relative vibration with time is indicated by reference numeral 603 shown in the lower diagram of FIG.

ΔH (t) = Vw × Δt / 2 (1)

In addition, the amplitude of relative vibration can also be calculated | required also as the difference of the distance which calculates | requires the distance from two reflective surfaces from arrival time.

  By monitoring the amplitude of this relative vibration, it is possible to measure abnormalities such as a decrease in plate thickness due to reflected wave wear, and changes in the vibration state due to secular changes. It is also possible to evaluate the vibration state by comparing with the vibration threshold value obtained in (1).

  In addition, it is possible to measure the vibration by transmitting ultrasonic pulses separately to the two devices and taking the difference, but it is also possible to measure the relative vibration, but the ultrasonic path, strength, delay material characteristics, etc. in each sensor Therefore, there is a concern about the decrease in accuracy. On the other hand, according to the present embodiment, since two reflected waves are received by one ultrasonic sensor, a decrease in accuracy due to a difference in transmission path and sensor can be removed, and highly accurate measurement is possible.

  In the above description, a sine wave has been described as an example, but a pulse having a sharp point as shown in FIG. 3, a square wave, a triangular wave, or the like may be used. In short, any waveform may be used as long as the reflected waveform is a pair of waveforms from the reflecting surfaces of the two devices by one ultrasonic oscillation. Qualitatively, a pointed shape is preferred as the distance between the two devices becomes narrower.

  In the above description, the monitoring target device having a curved reflection surface has been described. However, when the detection signal of the reflected wave is small, a reflector such as a reflector or a corner reflector may be used for the reflection surface. .

  Although the present invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, the invention is not limited to those disclosed embodiments, and conversely, It should be understood that various modifications and equivalent arrangements are included within the spirit and scope of the claims.

DESCRIPTION OF SYMBOLS 101: Reactor pressure vessel (RPV) 102: Bottom head 103: Top head 104: Core shroud 105: Core 106: Shroud support structure 107: Annular space (annulus part) 108: Inlet nozzle 109: Jet pump 110: Nozzle 111 : Throat 112: Diffuser 113: Lower plenum 114: Separator 115: Dryer 116: Main steam nozzle 201: Riser elbow 202: Riser pipe 203: Transition piece 204: Elbow 205: Bracket 206: Support 207: Wedge 208: Riser brace 209: Slip Joint 210: Gap 211: Driving fluid 212: Jet pump beam 301: Ultrasonic sensor 301a: Ultrasonic element 302: Ultrasonic transmitting / receiving unit 303: Coaxial line 304: Sonic wave signal processing unit 305: Ultrasound 306A: In-reactor equipment 306B: In-reactor equipment 307: Reactor containment vessel (PCV) 308: Hatch 309: Reactor water 401: Front plate 402: Propagation in front plate 403: Reflection 404: Transmitted wave to reactor water 405: Reflected wave in RPV 406: Multiple reflected wave in RPV 407: Reflected waveform from reflection surface of two devices 407A: Reflected wave from reactor device 306A 407B: Reactor device Reflected wave from 306B 501: Waveform of multiple reflected wave in RPV 101 502: Noise waveform accompanying shape echo 503: Reflected waveform from single device 504: Reflected waveform 601: Recording range 602A: Vibration of reflected waveform from reactor device 306A 602B: Vibration of reflected waveform from reactor equipment 306B 603: Relative vibration between reactor equipment 306A and 306B

Claims (14)

One ultrasonic sensor provided on the outer surface of the reactor pressure vessel, which transmits ultrasonic waves and receives the reflected waves;
An ultrasonic transmission / reception unit that controls the transmission performed simultaneously to a plurality of devices that vibrate relatively in the reactor pressure vessel, and the reception of each reflected wave from a reflection surface of the plurality of devices for the transmission;
An ultrasonic signal processing unit that processes the reflected waves and calculates relative vibrations between the reflecting surfaces of the plurality of devices;
A reactor vibration monitoring apparatus characterized by comprising: In claim 1,
The reactor signal monitoring unit according to claim 1, wherein the ultrasonic signal processing unit calculates the relative vibration by obtaining a distance between the reflecting surfaces based on a detection time difference between the reflected waves. In claim 1,
The reactor vibration monitoring apparatus, wherein the ultrasonic signal processing unit calculates a vibration displacement of the reflecting surface. In claim 1,
A reactor vibration monitoring apparatus, wherein a range of a recording time of the reflected waveform is determined based on a reflected waveform formed by each reflected wave. In claim 1,
The reactor vibration monitoring apparatus, wherein the ultrasonic signal processing unit transmits the ultrasonic wave by one pulse or a plurality of continuous pulses. In claim 1,
A reactor vibration monitoring apparatus, characterized in that a reflector is provided on at least one of the plurality of reflection surfaces. In claim 1,
The reactor vibration monitoring apparatus, wherein the plurality of devices that vibrate relatively are a jet pump throat and diffuser, a jet pump wedge and bracket, or a jet pump throat and bracket. A transmission step of simultaneously transmitting ultrasonic waves from the outer surface of the reactor pressure vessel to a plurality of relatively vibrating devices in the reactor pressure vessel;
Receiving each reflected wave from the reflecting surface of the plurality of devices for the transmission; and
A relative vibration calculating step of processing the reflected wave and calculating a relative vibration of the plurality of devices;
A reactor vibration monitoring method characterized by comprising: In claim 8,
In the relative vibration calculation step, the relative vibration is calculated based on a detection time difference between the reflected waves. In claim 8,
A reactor vibration monitoring method comprising: a vibration displacement calculating step of processing the reflected wave and calculating a vibration displacement of the reflecting surface. In claim 8,
A reactor vibration monitoring method, comprising: determining a range of a recording time of the reflected waveform based on a reflected waveform formed by each reflected wave. In claim 8,
In the transmitting step, the ultrasonic vibration is transmitted by one pulse or a plurality of continuous pulses. In claim 8,
The reactor vibration monitoring method characterized in that the plurality of devices that vibrate relatively are a jet pump throat and diffuser, a jet pump wedge and bracket, or a jet pump throat and bracket. In claim 10,
A reactor vibration monitoring method, wherein the presence or absence of an abnormality is determined by comparing the calculated amplitude of the relative vibration with a threshold value obtained by a prior analysis or an evaluation at the time of manufacture of the device.

Images