JP2011169612A - Pressure pulsation measuring method of main steam pipework - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure strain in a pipework circumferential direction of main steam pipework caused by pressure pulsation by using strain gauges having a smallest possible number of sheets, and to achieve an improvement of the reliability of measured data collection in pressure pulsation measurement of the main steam pipework for transporting steam for driving turbines of an atomic power plant facility. <P>SOLUTION: The strain gauges for measuring the strain in the circumferential direction of the pipework of the main steam pipework are disposed in a plurality of pairs, a pair of the strain gauges being 2 leaves disposed in point symmetrical positions each other to the center of the cross section in the radial direction of the pipework of the main steam pipework. Thereby, the reliability of the measured data collection is improved while the strain component generated by bending is eliminated, and the strain component generated by the external force in the axis direction of the pipework is eliminated by disposing the strain gauge for measuring the strain in the pipework axis direction of the main steam pipework. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for measuring pressure pulsation in a main steam pipe of a nuclear power generation facility using a strain gauge.

  As a conventional technique for evaluating and confirming the soundness of a dryer, a steam dryer installed in a pressure vessel of a boiling water reactor, sensors such as strain gauges, accelerometers, and pressure sensors are directly attached to the outer surface of the dryer. There is a method for measuring the stress generated in the dryer. With this method, the stress generated in the dryer can be measured with high accuracy, but in a reactor that is in operation, the dryer is held in the water even during periodic inspections, so a new sensor can be installed or replaced. Sometimes special work such as underwater welding is required.

  Therefore, as another conventional technique for evaluating and confirming the soundness of the dryer, pressure gauges in the main steam pipe are installed by installing strain gauges or pressure sensors at multiple locations on the main steam pipe and measuring the vibration in the circumferential direction of the pipe. A method of calculating pulsation and estimating pressure pulsation (stress acting on a dryer) in a steam dome using analysis or the like is disclosed (for example, Patent Document 1).

  In the method of directly measuring the pressure pulsation in the main steam pipe by installing the pressure sensor inside the main steam pipe, there is a possibility that the measurement accuracy of the pressure sensor is lowered due to the influence of the vortex generated in the steam flow. Also, if there is a flow, the pressure sensor itself may cause pressure pulsation or a resonance point. Furthermore, since the pipe size is large, the work for mounting the pressure sensor inside the main steam pipe is difficult. Therefore, it has been proposed to measure a pressure pulsation in the pipe by attaching a strain gauge to the outer wall surface of the main steam pipe without using a pressure sensor (see Patent Document 1).

JP 2007-155361 A

  When measuring the pressure pulsation in the pipe with a strain gauge attached to the outer wall surface of the main steam pipe, if the pressure pulsation is small and the generated pipe circumferential strain is very small, the main steam pipe is separated from the internal pressure pulsation. The influence of the strain component generated by the acting bending and the external force in the axial direction becomes large, and the measurement accuracy of the pressure pulsation is lowered. Therefore, it is necessary to devise and install a plurality of strain gauges for one measurement location of the main steam pipe so that the influence of these strain components can be excluded.

  In addition, considering the failure of the strain gauge, it is desirable to install multiple strain gauges for one measurement location in order to ensure the reliability of measurement data collection for each measurement location. .

  However, since there is an upper limit on the number of electrical penetrations that can transmit signals between the inside and outside of the containment vessel, the containment of the reactor from the strain gauges installed in the main steam piping inside the containment vessel There are a limited number of electrical penetrations that can be used to transmit measurement data to the operation floor outside the vessel, and there is an upper limit on the number of strain gauges that can be used. Moreover, there is a problem that the position where the strain gauge can be installed is limited due to the fact that a large number of pipe supports are attached to the main steam pipe.

  In other words, when a strain gauge is attached to the outer wall surface of the main steam pipe to measure pressure pulsations in the pipe, the strain component in the pipe circumferential direction can be measured with high accuracy within a limited number of pipes, and measurement data can be collected. It is desirable to determine an efficient placement position of the strain gauge that can improve the reliability of the strain gauge.

  The purpose of the present invention is to determine the placement position of such an efficient strain gauge so that the strain component in the pipe circumferential direction can be accurately measured, and the reliability of measurement data collection can be improved. The object is to provide a method for measuring pressure pulsation in a main steam pipe.

  In order to achieve the above object, the present invention has devised the following means for the position of the strain gauge.

  In order to eliminate the strain component caused by the external force in the bending direction acting on the main steam pipe, two points on the outer wall surface that are point-symmetric with respect to the pipe radial direction centroid are measured for one measurement point of the main steam pipe. A set of point positions is used to install two strain gauges that measure strain in the pipe circumferential direction.

  In addition to the strain gauge that measures the strain in the circumferential direction of the pipe, in addition to the strain gauge that measures the strain in the circumferential direction of the pipe for one measurement location of the main steam pipe, in order to exclude the strain component generated by the axial external force acting on the main steam pipe Install at least one strain gauge to measure axial strain.

  Also, in order to improve the reliability of measurement data collection, multiple strain gauges are not evenly arranged on the outer circumference of the pipe in the pipe radial direction cross section of the main steam pipe. It is installed close to each other at two points on the outer wall surface that are point-symmetric.

  According to the present invention, even when the strain caused by the pressure pulsation of the main steam pipe is small, the strain component due to the bending and the axial external force acting on the main steam pipe is excluded from the data measured by the strain gauge, and the pressure pulsation It is possible to accurately obtain the strain only in the circumferential direction of the pipe caused by.

  Even when a strain gauge failure occurs, the measurement data of the strain gauge paired with the failed strain gauge can be used, and the reliability of measurement data collection can be improved.

1 is a schematic view of a boiling water reactor to which the present invention is applied. It is explanatory drawing which shows the basic arrangement | positioning form of the strain gauge in this invention. 3 is an explanatory diagram illustrating an arrangement example of strain gauges in the pipe radial direction according to Embodiment 1. FIG. It is explanatory drawing which shows the example of arrangement | positioning of the strain gauge in Embodiment 2 in the pipe-axis direction. 10 is an explanatory diagram illustrating an arrangement example of strain gauges in a pipe radial direction according to Embodiment 2. FIG. It is a comparison table of the number of measurement data that can be collected when a strain gauge fails. It is explanatory drawing which shows the example of arrangement | positioning of the strain gauge in Embodiment 3 in the piping-axis direction. It is explanatory drawing which shows the example which has arrange | positioned the strain gauge in the same plane in a piping axis direction. It is explanatory drawing which shows the example of arrangement | positioning of the strain gauge in Embodiment 4 in the pipe-axis direction. It is explanatory drawing which shows the example of arrangement | positioning of the strain gauge in Embodiment 5 in the pipe radial direction. It is explanatory drawing which shows the example of arrangement | positioning of the strain gauge in Embodiment 5 in the pipe-axis direction.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view of a boiling water reactor (also referred to as BWR (Boiling Water Reactor)) of a nuclear power generation facility to which the present invention is applied. As shown in FIG. 1, a boiling water reactor includes a reactor pressure vessel (RPV (Reactor Pressure Vessel)) 1, a main steam pipe 2 connected to the reactor pressure vessel 1, and an upper portion of the reactor pressure vessel 1. A steam dome 3 located in the reactor, a dryer 4 installed in the reactor pressure vessel 1, and a plurality of safety relief valves (SRVs) 5 connected to the main steam pipe 2. . FIG. 1A is a schematic vertical sectional view of the upper part of the boiling water reactor, and FIG. 1B is a schematic horizontal sectional view.

  As shown in FIG. 1 (b), four main steam pipes 2 are usually installed in the reactor pressure vessel 1. FIG. 1A shows two of the main steam pipes 2, and two pressure pulsation measurement points 6 for measuring pressure pulsation with a strain gauge are provided on one of them.

  In order to evaluate the soundness of the dryer 4, when measuring the pressure pulsation in one of the main steam pipes 2, it is necessary to solve the wave equation for obtaining the pressure pulsation waveform in the pipe. There are two unknowns in the equation: amplitude and phase. Therefore, it is necessary to install two or more pressure pulsation measurement points 6 in the pipe axis direction of the main steam pipe 2. Normally, in order to accurately grasp the influence of the attenuation of pressure pulsation and estimate the pressure pulsation of the steam dome 3, the position of the pressure pulsation measurement point 6 is as shown in FIG. And two locations near the downstream SRV 5 that serves as a pressure pulsation sound source.

  Since the pressure pulsation in the main steam pipe 2 deforms the main steam pipe 2 in the pipe circumferential direction, the magnitude of the pressure pulsation can be measured by measuring the deformation amount (strain amount). In general, affixed strain gauges used for strain measurement have a predetermined measurement direction, so the strain gauge measurement direction matches the pipe circumferential direction in order to measure strain in the pipe circumferential direction caused by pressure pulsation. Let

  The main steam pipe 2 in an actual working environment is subjected to bending and an external force in the axial direction due to vibrations and the like acting on the entire pipe. Since the deformation in the pipe circumferential direction also occurs due to the action of these external forces, the measured strain in the pipe circumferential direction includes not only the strain component caused by pressure pulsation but also the strain component caused by bending and axial external force. It is. Since the pressure pulsation in the pipe of the main steam pipe 2 is minute and the distortion in the pipe circumferential direction caused by the pressure pulsation is also minute, in order to accurately measure the pressure pulsation, it is necessary to exclude the distortion component caused by these external forces. Here, the amount of strain in the pipe circumferential direction of the main steam pipe 2 is the sum of the strain component mainly caused by pressure pulsation in the pipe and the strain component caused by bending and axial external force acting on the main steam pipe 2. The strain component in the pipe circumferential direction, which is theoretically analyzed only by pressure pulsation, is obtained from the strain gauge measurement data.

  FIG. 2 shows a basic strain gauge arrangement for excluding strain components caused by bending and axial external force from the amount of strain in the pipe circumferential direction of the main steam pipe 2. The amount of strain generated by the external force in the bending direction has the same absolute value and the opposite sign at two points that are point-symmetric with respect to the pipe radial direction centroid. Therefore, two circumferential measuring strain gauges 71 for measuring the amount of strain in the circumferential direction of the pipe by measuring two points symmetrical with respect to the pipe radial direction centroid and matching the measurement direction with the circumferential direction of the pipe. If installed, the strain component caused by the external force in the bending direction can be excluded by calculating the average value of the measured values of both.

  In addition, by installing at least one axial measurement strain gauge 72 that measures the amount of strain in the pipe axis direction by adjusting the measurement direction to the pipe axis direction, the axial external force acting on the pipe can be obtained. By obtaining the strain component in the pipe circumferential direction caused by the axial external force from the theoretical formula, the influence can be excluded. The strain component in the pipe axis direction includes a strain component caused by pressure pulsation and a strain component caused by external force acting on the pipe, but the influence of the pressure pulsation is negligible and is ignored.

  In addition, in order to obtain more accurately the strain component in the pipe circumferential direction caused by pressure pulsation in the pipe, two axially measuring points are set with two points symmetrical about the pipe radial cross-section centroid. In the same manner as described above, the strain component in the pipe axis direction due to the external force in the bending direction is also excluded from the strain amount in the pipe axis direction measured by the strain gauge 72 for axial measurement. Thus, it is preferable to obtain a strain component generated by an external force in the axial direction.

<Embodiment 1>
First, as Embodiment 1, as a first embodiment for improving the reliability of measurement data collection, a case where a plurality of circumferential measurement strain gauges 71 are equally installed in the circumferential direction of the pipe will be described. In the example shown in FIG. 3, four sets (eight pieces) of circumferential measurement strain gauges 71 are equally installed in the pipe circumferential direction, and one set (two pieces) of axial measurement strain gauges 72 are installed in the pipe axial direction. Yes. A specific procedure for calculating a strain component caused by pressure pulsation in the pipe in this case will be described.

  Here, the strain amounts measured by the circumferential direction measurement strain gauge 71 are ε1 to ε8, the strain amounts measured by the axial direction measurement strain gauge 72 are ε9, ε10, and the pipe circumference caused by the pressure pulsation in the pipe. The strain amount in the direction is εh, the bending strain amount in the pipe axis direction is εM, and the expansion / contraction strain amount in the pipe axis direction is εc. Also, t (i) is the pipe thickness of the i-th pressure pulsation measurement point 6 and Young's modulus E and Poisson's ratio ν are known material constants.

  The amount of strain caused by bending in the pipe axial direction is the same in absolute value and opposite in sign at two points that are point-symmetric with respect to the pipe radial cross-sectional centroid. Therefore, the pipe internal pressure Ph and the axial external force are unknown. For Fc and bending moment M, the basic equation of elasticity can be derived (reference: Japan Society of Mechanical Engineers (new edition) Mechanical Engineering Handbook, A4 Material Mechanics, page: A4-6). These can be solved.

  As a calculation procedure, first, in order to remove a strain component caused by bending, ε1 to ε8 are set as a set of two circumferential measuring strain gauges 71 at a point-symmetrical position with respect to the pipe radial direction centroid. Average. At this time, for example, when the circumferential measurement strain gauge 73 (71) marked with an X in the lower part of FIG. 3 is out of order, the circumferential measurement is paired with the circumferential measurement strain gauge 73 (71). The measurement data of the strain gauge 74 (71) for use is excluded from the calculation, and the remaining three sets of measurement data (circles in FIG. 3) are used.

  The value obtained by averaging includes, in addition to the strain εh in the pipe circumferential direction caused by pressure pulsation, the component of Poisson contraction deformation due to the amount of expansion strain εc in the pipe axis direction. The amount of strain εh in the pipe circumferential direction can be obtained by subtracting from the value obtained by averaging. Note that the average value of the strain amounts ε9 and ε10 measured by the axial direction measuring strain gauge 72 is used as the expansion and contraction strain amount εc in the pipe axis direction.

<Embodiment 2>
Next, as a second embodiment, a case where a plurality of sets of circumferential measurement strain gauges 71 are arranged close to each other in the pipe circumferential direction will be described as a second embodiment for further improving the reliability of measurement data collection. . FIG. 4 shows details of the arrangement of strain gauges in the axial direction in the X part of the main steam pipe 2 of FIG. 1, and FIG. 5 shows details of the arrangement of strain gauges in the same circumferential direction of the pipe.

  In the second embodiment, as shown in the examples of FIGS. 4 and 5, a plurality of circumferential direction measuring strain gauges 71 installed in the circumferential direction of the pipe are installed close to each other in the circumferential direction of the pipe. Also, a set (two) of strain gauges 72 for axial measurement is installed in the vicinity of the circumferential measurement strain gauge 71 installed close to each other at a point-symmetrical position with respect to the pipe radial direction centroid. ing.

  Of the amount of strain in the circumferential direction of the pipe measured by the strain gauge 71 for circumferential direction measurement, the strain component in the circumferential direction caused by the external force in the bending direction is point-symmetric with respect to the pipe radial direction centroid as described above. It can be excluded by installing a strain gauge with a set of different positions and averaging the measured values of both.

  Further, as described above, the strain component in the circumferential direction due to the external force in the axial direction may be excluded by installing the strain gauge 72 for axial measurement and obtaining and subtracting the Poisson contraction deformation component from the measured value. it can. In the second embodiment, a set (two) of axial strain gauges 72 for axial measurement are installed at point symmetric with respect to the pipe radial direction centroid, and the measured values of both are averaged. Since the strain component in the pipe axis direction caused by the external force in the bending direction can be excluded, the circumferential strain component caused by the pressure pulsation can be obtained with higher accuracy.

  Next, the effect of improving the reliability of measurement data collection according to the second embodiment will be described by comparison with the first embodiment (FIG. 3). In the second embodiment shown in FIGS. 4 and 5 and the first embodiment shown in FIG. 3, four sets (eight pieces) of circumferential direction measuring strain gauges 71 are installed in the circumferential direction of the pipe. .

  By the way, in order to exclude the influence of the external force in the bending direction as described above, it is necessary to collect measurement data for a set of two sheets installed at point symmetric positions with respect to the pipe diameter sectional centroid. Therefore, the number of sets of measurement data that can be collected when all of these circumferential direction strain gauges 71 are operating normally, that is, the number of measurement data that can be collected is four.

  First, consider the case where the strain gauges are equally arranged as in the first embodiment (FIG. 3). In this case, if one circumferential direction measuring strain gauge 71 breaks down, the number of pieces of measurement data that can be collected decreases by one and becomes three. In addition, when two circumferential measurement strain gauges 71 fail, the number of measurement data that can be collected is three when the two failed strain gauges are paired with each other, and in other cases The number of measurement data that can be collected is reduced by two to two.

  On the other hand, in the second embodiment, since the circumferential direction measurement strain gauges 71 are arranged close to each other, even if measurement data of other strain gauges adjacent to each other are used instead of the failed strain gauge, Strain components in the circumferential direction of the pipe caused by bending can be sufficiently excluded. Therefore, for example, even when the circumferential measurement strain gauge 73 (71) marked with a cross in the lower part of FIG. 5 fails, the measurement data of the other strain gauges 71 adjacent thereto is used to obtain the circumferential direction. The measurement data of the circumferential measurement strain gauge 74 (71) paired with the measurement strain gauge 73 (71) can be used (thick broken line in FIG. 5). Therefore, even if one circumferential direction measurement strain gauge 71 fails, the number of measurement data that can be collected remains four (circles in FIG. 5).

  FIG. 6 shows the occurrence probability of the number of measurement data that can be collected with respect to the number of failures in the circumferential direction measurement strain gauge 71 when the gauges are arranged close to each other in the pipe circumferential direction as in the second embodiment and as in the first embodiment. A comparison is made with respect to a case where gauges are evenly arranged in the pipe circumferential direction. FIG. 6 shows the number of strain gauge failures for each stage, and the occurrence probability for each number of measurement data collections is shown in each column. The probability of occurrence indicates that the number of measurement data that can be collected tends to increase as the value increases for a certain number of gauge failures. That is, it can be said that the higher the probability of occurrence when the number of measurement data collections is large and the smaller the probability of occurrence when the number of measurement data collections is small, the higher the reliability of measurement data collection for strain gauge failure.

The method for calculating the occurrence probability will be described by taking as an example the case where the number of gauge failures is “3” in the second embodiment. First, the number of combinations for selecting three gauges of failure from eight strain gauges is ₈ C ₃ = 56. The number of combinations including all three failure gauges among the four strain gauges close to each other is twice the number of combinations selected from the four, and 2 × ₄ C ₃ = 8 ways It is. In this case, since the four strain gauges facing the side including the failed gauge are all normal, the number of measurement data that can be collected is four, and the probability of occurrence is 8/56. In other cases, the number of normal gauges in the four adjacent gauges is one for three and the other for two, so the number of measurement data that can be collected is three. The probability is 1-8 / 56 = 48/56. From the symmetry, when the number of failures is “1”, the number of failures is “7”, when the number of failures is “2”, the number of failures is “6”, and the number of failures is “3”. In this case, the occurrence probability is symmetric with respect to the case where the number of failures is “5”.

Next, a method of calculating the probability of occurrence when the number of gauges is “3” in the case where gauges are evenly arranged in the pipe circumferential direction (Embodiment 1) will be described. First, the number of combinations for selecting three gauges of failure from eight strain gauges is ₈ C ₃ = 56. If two of the three strain gauges in failure are paired with each other, the number of measurement data that can be collected is two. Since the number of combinations of two gauges forming a pair is ₄ C ₁ = 4, and the method of selecting the remaining one is ₆ C ₁ = 6, the number of combinations in this case is 4 × 6 = There are 24 streets. Therefore, the occurrence probability that the number of measurement data that can be collected is two is 24/56. In other cases, the measurement data of all three sets including the failure gauge is invalid, so the number of measurement data that can be collected is one, and the probability of occurrence is 1-24 / 56 = 32/56 It becomes.

  As described above, even if the failure probability of strain gauges is the same, a plurality of sets of circumferential measurement strain gauges 71 are arranged close to each other at two points symmetrical with respect to the pipe radial direction centroid. Therefore, the measurement data can be collected more than when a plurality of sets of circumferential direction measurement strain gauges 71 are evenly arranged in the circumferential direction of the pipe, and the reliability of measurement data collection can be improved.

  As another effect, the strain gauge installation position in the circumferential direction of the pipe is consolidated into two positions, so the time required for strain gauge installation work and maintenance work can be shortened, and the amount of exposure to workers can be reduced. Is possible.

<Embodiment 3>
Next, as a third embodiment, in the measurement of pressure pulsation, the problem that the phase of the pressure pulsation wave cannot be specified when the distance between the pressure pulsation measurement points coincides with the wavelength of the pressure pulsation wave or an integral multiple of the wavelength is avoided. Therefore, a case where a plurality of sets of circumferential measurement strain gauges 71 are installed at different positions in the pipe axis direction will be described.

  In order to evaluate the soundness of the dryer 4, when measuring the pressure pulsation in one of the main steam pipes 2, the amplitude and phase for obtaining the pressure pulsation waveform in the pipe are defined as unknowns. It is necessary to solve the wave equation. Since there are a plurality of pressure pulsation frequency bands to be measured, it is necessary to solve the wave equation for each frequency band, but the distance between two pressure pulsation measurement points 6 (see FIG. 1) installed in the pipe axis direction is If the pressure pulsation wave coincides with the wavelength or an integral multiple of the wavelength, the wave equation cannot be solved.

  Therefore, in order to avoid the problem that the distance between the pressure pulsation measurement points coincides with the wavelength of the pressure pulsation wave or an integral multiple of the wavelength, one pressure pulsation measurement point 6 (see FIG. 1) of the main steam pipe 2 is used. A plurality of circumferential measurement strain gauges 71 for measuring strain in the pipe circumferential direction are installed at different positions in the pipe axis direction.

  FIG. 7 shows details of the arrangement of strain gauges in the pipe axis direction of the main steam pipe 2 of FIG. In the example of FIG. 7, the circumferential direction measuring strain gauges 71 are arranged in four pairs (eight) equally in the circumferential direction of the pipe, with a pair of two strain gauges centered on the pipe radial direction centroid. The positions of each set in the pipe axis direction are different from each other. In addition, two strain gauges 72 for axial measurement are installed as a set in the vicinity of the center in the pipe axial direction of each set at a point symmetric with respect to the pipe radial direction centroid.

  Of the amount of strain in the pipe circumferential direction measured by the circumferential direction measurement strain gauge 71, the strain component in the pipe circumferential direction due to the external force in the bending direction and the strain component in the pipe circumferential direction due to the axial external force are: It can be excluded by the same method as in the first embodiment. In addition, since the difference in the position in the pipe axis direction of each set of the circumferential measurement strain gauges 71 is sufficiently small with respect to the total length of the pipe, the pipe axis direction caused by the axial external force measured by the axial measurement strain gauge 72 Are assumed to be the same at the positions of each set of the circumferential measurement strain gauges 71.

  For comparison with the third embodiment, a case where eight circumferential direction measurement strain gauges 71 are installed in the same plane in the pipe axis direction as shown in FIG. 8 will be described. As described above, in order to solve the wave equation of the pressure pulsation in the pipe, there are two unknowns, the amplitude and the phase. Therefore, it is necessary to measure the pressure pulsation at two or more places in the pipe axis direction. However, as shown in FIG. 8, when the distance between the pressure pulsation measurement points 6 coincides with the wavelength of the pressure pulsation wave 8 or an integral multiple of the wavelength, the phase difference cannot be obtained, and the wave equation is I can't solve it. Thus, when the circumferential direction measurement strain gauge 71 is installed in the same plane in the pipe axis direction, the distance between the pressure pulsation measurement points 6 is equal to the wavelength of the pressure pulsation wave 8 or an integer multiple of the wavelength. Pressure pulsation cannot be obtained (marked with x in FIG. 8).

  On the other hand, in the third embodiment, each set of circumferential measurement strain gauges 71 at one measurement location is installed so that the positions in the pipe axis direction are different from each other. Is equal to the wavelength of the pressure pulsation wave 8 to be obtained or an integral multiple of the wavelength, measurement data for other sets can be obtained. Therefore, the problem that the distance between the pressure pulsation measurement points 6 matches the wavelength of the pressure pulsation wave 8 or an integral multiple of the wavelength can be avoided for any frequency component, and the frequency band of the pressure pulsation that can be measured is widened. (Circles in FIG. 7).

<Embodiment 4>
In the third embodiment, the circumferential direction measurement strain gauges 71 are arranged equally in the pipe circumferential direction with a pair of two strain gauges paired around the pipe radial direction sectional centroid as shown in FIG. In this way, each set of circumferential direction measuring strain gauges 71 may be arranged at the same position in the circumferential direction of the pipe. Further, each set of circumferential direction measuring strain gauges 71 may be arranged at positions close to each other in the pipe circumferential direction. At this time, by disposing each set of the circumferential direction measurement strain gauges 71 at at least two different positions in the pipe axis direction, the distance between the pressure pulsation measurement points 6 is changed to the pressure pulsation wave 8 as in the third embodiment. The problem of coincidence with the wavelength or an integral multiple of the wavelength can be avoided.

<Embodiment 5>
When it is clear that the influence of the axial external force acting on the main steam pipe 2 is small, for example, as shown in FIGS. 10 and 11, the strain in the pipe axis direction is measured in the second and third embodiments. The installation of the strain gauge 72 for axial measurement may be omitted.

  Although the description of the embodiment has been completed above, the embodiment of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, the number of strain gauges installed in the pipe axis direction and the pipe circumferential direction may be changed according to the situation. Further, the arrangement form in the pipe circumferential direction may be other than equal or close, and the combination of the arrangement in the pipe circumferential direction and the arrangement in the pipe axial direction may be any.

  The present invention is applicable to domestic and foreign boiling water reactors that measure pressure pulsations in main steam piping. The present invention can also be applied to the case where the soundness evaluation of a moisture separator, which is a secondary system facility of a pressurized water reactor (PWR (Pressurized Water Reactor)), is performed by measuring the pressure pulsation in the main steam pipe. Is possible.

1 Reactor pressure vessel (RPV)
2 Main steam piping 3 Steam dome 4 Dryer 5 Safety relief valve (SRV)
6 Pressure pulsation measurement location 8 Pressure pulsation wave 71 Strain gauge for circumferential measurement 72 Strain gauge for axial measurement 73 Faulty strain gauge 74 Strain gauge paired with faulty strain gauge

Claims (7)

A method for measuring pressure pulsation of a main steam pipe for transporting steam for driving a turbine of a nuclear power generation facility using a strain gauge installed on an outer wall surface of the main steam pipe,
A strain gauge for measuring the amount of strain in the pipe circumferential direction of the main steam pipe with respect to one measurement point in the pipe axis direction of the main steam pipe is mutually connected with respect to the pipe radial direction sectional centroid of the main steam pipe. At least one set is installed as a set of two pieces installed at a point symmetrical position,
Close to the strain gauge that measures the strain amount in the pipe circumferential direction of the main steam pipe, at least one strain gauge that measures the strain amount in the pipe axis direction of the main steam pipe is installed,
A pressure pulsation measurement method for a main steam pipe, wherein a strain component in a pipe circumferential direction caused by the pressure pulsation of the main steam pipe is obtained from a strain amount measured by the plurality of strain gauges. In the pressure pulsation measuring method of the main steam piping according to claim 1,
A method for measuring pressure pulsations in a main steam pipe, wherein a plurality of sets of the two pairs of strain gauges for measuring the amount of strain in the pipe circumferential direction of the main steam pipe are installed close to each other. In the pressure pulsation measuring method of the main steam piping according to claim 1,
A main steam characterized in that a plurality of sets of the two pairs of strain gauges for measuring the strain amount in the pipe circumferential direction of the main steam pipe are installed at different positions in the pipe axis direction of the steam pipe. Method for measuring pressure pulsation in piping. In the main steam piping pressure pulsation measuring method according to claim 2,
A method for measuring the pressure pulsation of a main steam pipe, wherein each set of the two strain gauges installed in a plurality of groups close to each other is installed at at least two different positions in the pipe axial direction of the steam pipe. . A method for measuring pressure pulsation of a main steam pipe for transporting steam for driving a turbine of a nuclear power generation facility using a strain gauge installed on an outer wall surface of the main steam pipe,
A strain gauge that measures the amount of strain in the pipe circumferential direction of the main steam pipe is connected to one measurement point in the pipe axial direction of the main steam pipe with respect to the radial sectional centroid of the main steam pipe. Two sets installed at symmetrical positions are taken as one set, and each set is placed close to each other, and multiple sets are installed.
A pressure pulsation measurement method for a main steam pipe, wherein a strain component in a pipe circumferential direction caused by the pressure pulsation of the main steam pipe is obtained from a strain amount measured by the plurality of strain gauges. A method for measuring pressure pulsation of a main steam pipe for transporting steam for driving a turbine of a nuclear power generation facility using a strain gauge installed on an outer wall surface of the main steam pipe,
A strain gauge for measuring the amount of strain in the pipe circumferential direction of the main steam pipe with respect to one measurement point in the pipe axis direction of the main steam pipe is mutually connected with respect to the pipe radial direction sectional centroid of the main steam pipe. Two sets installed at a point-symmetrical position as a set, a plurality of sets are installed at different positions in the pipe axis direction of the steam pipe,
A pressure pulsation measurement method for a main steam pipe, wherein a strain component in a pipe circumferential direction caused by the pressure pulsation of the main steam pipe is obtained from a strain amount measured by the plurality of strain gauges. In the pressure pulsation measurement method of the main steam piping according to claim 5,
A method for measuring the pressure pulsation of a main steam pipe, wherein each set of the two strain gauges installed in a plurality of groups close to each other is installed at at least two different positions in the pipe axial direction of the steam pipe. .

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