A two-phase flow measurement system for special-shaped rod bundle channels in nuclear reactors

Abstract

The present invention discloses a two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel, wherein a first electrode group is attached to the side of a first rod bundle facing the special-shaped rod bundle channel, a second electrode group is attached to the side of a second rod bundle facing the special-shaped rod bundle channel, a third electrode group is attached to the side of a bent rod bundle facing the special-shaped rod bundle channel, and a fourth electrode group is attached to the side of a fourth rod bundle facing the special-shaped rod bundle channel, wherein the first electrode group and the fourth electrode group each include two electrodes, and the second electrode group and the third electrode group each include three electrodes. By changing the position, number and angle of the electrodes, the accuracy of the two-phase flow measurement in the special-shaped rod bundle channel is improved.

Description

Technical Field

[0001] The invention relates to the technical field of two-phase flow measurement, and in particular to a two-phase flow measurement system for a special-shaped rod bundle channel of a nuclear reactor. Background Art

[0002] The measurement of two-phase flow in the rod bundle channel of a nuclear reactor is based on the different materials inside the detected area, which have different resistances, thereby achieving the measurement of the detected area. In actual measurement, it is necessary to first inject current into the detected area, and then measure the potential through electrodes arranged around it. If the material in the detected area changes, the magnitude of the potential measured on the electrode will change. By measuring the change in potential on the electrode, the material distribution in the detected area can be inferred. This method has the advantages of non-invasiveness, fast speed, simple system, and low cost, and is widely used in the field of two-phase flow measurement.

[0003] When using a sub-channel cavitation meter for measurement, the electrodes are arranged around the measured area, so the measured area has specific application conditions. For ordinary detection areas, the two-phase flow characteristics of different areas can be measured by changing the position of the electrodes. For example, by arranging the cavitation meter around the channel, the voltage signal within the sub-channel range can be measured.

[0004] For example, Chinese patent (CN105784785B) discloses a two-phase flow measurement system for a nuclear reactor rod bundle channel based on electrical resistance tomography, including a patch electrode group, an electrical resistance tomography module, a data acquisition card and a computer; each patch electrode group includes eight patch electrodes, a single rod bundle channel is formed in the middle of each adjacent four rod bundles, each single rod bundle channel is configured with a patch electrode group, and two electrodes are attached to the side of each rod bundle facing the single rod bundle channel, such as Figure 1 shown.

[0005] However, due to various factors, the rod bundle may be deformed, resulting in the single rod bundle channel formed in the middle of the four rod bundles being irregular or even closed (collectively referred to as the special-shaped rod bundle channel, such as Figure 2 As shown in the figure), the original patch electrodes cannot accurately receive signals, resulting in low measurement accuracy. Summary of the invention

[0006] In view of the problem of low two-phase flow measurement accuracy when a nuclear reactor rod bundle has a special-shaped rod bundle channel in the prior art, the present invention proposes a two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel, and a method of changing the position, number and angle of electrodes to improve the accuracy of two-phase flow measurement in the special-shaped rod bundle channel.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel, wherein a first electrode group is attached to the side of a first rod bundle facing the special-shaped rod bundle channel, a second electrode group is attached to the side of a second rod bundle facing the special-shaped rod bundle channel, a third electrode group is attached to the side of a bent rod bundle facing the special-shaped rod bundle channel, and a fourth electrode group is attached to the side of a fourth rod bundle facing the special-shaped rod bundle channel, wherein the first electrode group and the fourth electrode group each include two electrodes, and the second electrode group and the third electrode group each include three electrodes.

[0009] Preferably, in the nuclear reactor, when no deformation occurs, four adjacent rod bundles are respectively marked as the first rod bundle, the second rod bundle, the third rod bundle, and the fourth rod bundle, and a single rod bundle channel is formed in the middle; when the third rod bundle is deformed, the mark is updated to a bent rod bundle, and the positions and marks of the first rod bundle, the second rod bundle, and the fourth rod bundle remain unchanged, and a special-shaped rod bundle channel is formed in the middle.

[0010] Preferably, the line connecting the center of the first rod bundle and the center of the fourth rod bundle is used as the dividing line, the five electrodes on the right side of the dividing line are the exciting electrodes, and the five electrodes on the left side of the dividing line are the receiving electrodes.

[0011] Preferably, each of the electrode groups is respectively connected to a corresponding signal processing circuit, which measures the voltage signal on each electrode and sends it to a data acquisition card. The controller obtains the voltage signal through the data acquisition card and obtains the two-phase flow characteristics of the special-shaped rod bundle channel by calibrating the voltage signal.

[0012] Preferably, the angle between adjacent electrodes in each electrode group is 30°.

[0013] Preferably, the signal processing circuit includes a signal source for providing an excitation current signal, a gate array for controlling the excitation electrodes, a gate array for controlling the receiving electrodes, an interface for communication and a control core for logic control.

[0014] Preferably, the signal source is composed of two operational amplifiers, one of which is configured as a Howland circuit to form a current source; and the other operational amplifier is configured as a follower.

[0015] Preferably, the control core is a micro signal processor MSP430, which is used to complete the control instruction generation, data / command communication, and synchronization trigger signal generation of the gate array.

[0016] In summary, due to the adoption of the above technical solution, compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The present invention ensures the measurement of two-phase flow in the special-shaped rod bundle channel by changing the arrangement position and number of electrodes; and ensures the integrity of the measurement range by changing the electrode angle. By changing the positions of the excitation electrode and the receiving electrode, it is ensured that the entire special-shaped rod bundle channel area can achieve the measurement of two-phase flow. Through frequency multiplexing and trigger synchronization, it is ensured that the entire rod bundle channel area can achieve the measurement of two-phase flow. Through experimental calibration and simulation calibration methods, the feasibility of the calibration results is guaranteed, and the authenticity of the cavitation fraction finally obtained is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic diagram of a two-phase flow measurement system for a special-shaped rod bundle channel of a nuclear reactor in the prior art.

[0019] Figure 2 Schematic diagram of a special-shaped rod bundle channel according to an exemplary embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the arrangement of the electrode group of the special-shaped rod bundle channel according to an exemplary embodiment of the present invention.

[0021] Figure 4 A potential line distribution diagram generated by the electrode group of the present invention at different closure degrees according to an exemplary embodiment of the present invention; Figure 4 (a) shows the potential line distribution diagram generated by the electrode group under the straight rod; Figure 4 (b) shows the potential line distribution diagram of the electrode group when the closure degree is 50%; Figure 4 (c) shows the potential line distribution diagram of the electrode group when the closure degree is 80%; Figure 4 (d) shows the potential line distribution diagram generated by the electrode group when the closure degree is 100%.

[0022] Figure 5 Schematic diagram of a calibration curve of a special-shaped channel according to an exemplary embodiment of the present invention.

[0023] Figure 6 Schematic diagram of calibration simulation of a special-shaped channel calibration curve according to an exemplary embodiment of the present invention.

[0024] Figure 7 FIG. 4 is a schematic diagram of the division of excitation electrodes and receiving electrodes according to an exemplary embodiment of the present invention.

[0025] Figure 8 Schematic diagram of the angle between adjacent electrodes in an electrode group according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0027] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] There are n×m rod bundles in the rod bundle channel of a nuclear reactor, where n and m are both natural numbers greater than or equal to 2; among these rod bundles, a single rod bundle channel is formed in the middle of every four adjacent rod bundles. When the rod bundle is deformed, the channel formed in the middle of every four adjacent rod bundles is a special-shaped rod bundle channel, and the deformed rod bundle is marked as a bent rod bundle, such as Figure 2 As shown. Due to the irregular or even closed conditions in the special-shaped rod bundle channel, the original cavitation instrument cannot receive signals well. Therefore, the present invention solves the problem of being unable to measure the special-shaped rod bundle channel by changing the electrode position, number and angle.

[0029] The invention provides a two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel, comprising four electrode groups, each electrode group is respectively connected to a corresponding signal processing circuit, and each signal processing circuit is connected to a controller.

[0030] like Figure 3 As shown, when no deformation occurs, the four adjacent rod bundles are marked as the first rod bundle, the second rod bundle, the third rod bundle, and the fourth rod bundle. When the third rod bundle is deformed, its position changes and can be marked as a bent rod bundle, while the positions of the first rod bundle, the second rod bundle, and the fourth rod bundle remain unchanged.

[0031] In this embodiment, the diameter of the rod bundle is 9.5 mm, the center distance between adjacent rod bundles is 12.6 mm, the length of the electrode is 10 mm, and the width is 1 mm.

[0032] In this embodiment, a first electrode group is attached to the side of the first rod bundle facing the special-shaped rod bundle channel, a second electrode group is attached to the side of the second rod bundle facing the special-shaped rod bundle channel, a third electrode group is attached to the side of the bent rod bundle facing the special-shaped rod bundle channel, and a fourth electrode group is attached to the side of the fourth rod bundle facing the special-shaped rod bundle channel.

[0033] In this embodiment, the signal source generates an excitation voltage signal, which is converted into an excitation current signal through a signal processing circuit and loaded into the corresponding electrode group. The data acquisition card collects the AC voltage signal of the test area through the signal processing circuit and transmits it to the controller for analysis.

[0034] In this embodiment, the first electrode group and the fourth electrode group each include two electrodes, and the second electrode group and the third electrode group each include three electrodes.

[0035] In this embodiment, Figure 7 As shown, a total of 10 electrodes in 4 electrode groups are divided into excitation electrodes and receiving electrodes. The midpoints of the two rod bundles with fewer electrodes are connected as the dividing line, one side of the dividing line is the excitation electrode, and the electrode on the other side is the receiving electrode; this setting structure is conducive to the electrode group to adapt to the bending of the rod bundle and even to the impact of contact with other rod bundles. In actual use, the measured area is filled with two-phase fluid, and the AC voltage signals of different amplitudes are received through the huge difference in conductivity between bubbles and electrolyte water, which are converted into DC voltage signals under the action of the signal processing circuit.

[0036] For example, there are two electrodes in the first electrode group and the fourth electrode group, and three electrodes in the second electrode group and the third electrode group. Therefore, the line connecting the center O1 of the first rod bundle and the center O1 of the fourth rod bundle is used as the dividing line, and the five electrodes on the right side of the dividing line are the excitation electrodes, and the five electrodes on the left side of the dividing line are the receiving electrodes. The electric field distribution formed by this structure is the most uniform compared with other electrode arrangements. For example, there can be three or six electrodes on the right side of the dividing line, and seven or four electrodes on the left side of the dividing line. However, the electric field distribution formed in this way has deviations and is not uniform, but measurement can also be achieved.

[0037] In this embodiment, Figure 8 As shown, the coverage of the received signal in the measured area can be increased by setting the angle a between adjacent electrodes in each electrode group. For example, the arrangement mode in which the angle a is 30° ensures that the voltage signal is concentrated in the special-shaped rod bundle channel.

[0038] The arrangement of electrodes in the prior art is suitable for regular channels. When the rod bundle is deformed, the potential lines between the electrodes will change, resulting in inaccurate measurement. The present invention arranges the positions and angles of the electrodes to ensure that the potential lines are uniform even when the rod bundle is deformed, resulting in higher measurement accuracy.

[0039] like Figure 4As shown in the figure, it is a potential line distribution diagram generated by the electrode group of the present invention. It can be seen that the equipotential lines are obviously more densely distributed between the rod bundle channels at different closures (straight rod, 50%, 80%, 100%), and the overall distribution is more uniform. The denser the distribution, the greater the electric field strength, the more the measurement signal changes with the change of the two-phase flow, and the higher the sensitivity of the electrode; the more uniform the distribution, the better the linearity of the electrode measurement.

[0040] In this embodiment, the signal processing circuit has the characteristics of low power consumption and low cost, including a signal source for providing an excitation current signal, a gate array for controlling the excitation electrode, a gate array for controlling the receiving electrode, an interface for communication, and a control core for logic control. Among them, the signal source is composed of two operational amplifiers, one of which is configured as a Howland circuit to form a current source; and the other operational amplifier is configured as a follower. The gate array is composed of 4 single-pole 8-throw switches, two of which are used to control the electrodes loaded by the excitation current source, and the other two switches are used to control the electrodes connected to the test output signal. The electrodes for measuring the AC voltage signal are connected to the four groups of switches at the same time, and the output electrode voltage is converted into a single-ended signal output through an instrumentation amplifier.

[0041] The signal source is used to provide an accurate current excitation signal. A wide-band video operational amplifier can be used to ensure low signal noise and that the output current frequency can quickly follow the input voltage signal frequency change. The current source receives the accurate voltage signal generated by the external voltage signal source and outputs an accurate excitation current signal.

[0042] The gate array chip has a control speed of nanoseconds, ensuring that the electrode selection speed can meet the speed required by the sub-channel cavitation meter measurement.

[0043] The control core is the micro signal processor MSP430, which is used to complete the control instruction generation, data / command communication, and synchronous trigger signal generation of the gate circuit

[0044] In this embodiment, a data acquisition card connected to the output end of the signal processing circuit is also included, which is used to collect the potential information on the measuring electrode and simultaneously collect the synchronous trigger signal of each signal processing circuit to facilitate data processing by the subsequent controller.

[0045] In this embodiment, the controller is used to obtain the distribution of the two-phase flow in the rod cluster channel in real time using the voltage data obtained by the acquisition card; and is also used to configure the signal processing circuit and set appropriate acquisition modes and parameters. It is worth noting that in the solution disclosed in this embodiment, the electrodes at the boundaries of the rod cluster area are not used to measure the two-phase flow in the rod cluster channel, but four electrode groups are used to measure each special-shaped rod cluster channel.

[0046] The calibration curve obtained by multi-physics calculation software and the curve obtained by experimental calibration are collated, and the experimental data are integrated, and the working points of full water and full gas are added for calibration. In order to achieve higher accuracy, different functions are selected to cover the calibration results, and the functions that meet the requirements are selected for fitting, and finally the calibration curve of the special-shaped rod bundle channel (such as Figure 5 ).

[0047] According to the voltage signal measured in the experiment, the required two-phase flow characteristics are obtained by performing data processing with the obtained special-shaped rod bundle channel calibration curve.

[0048] The method for obtaining the calibration curve of the special-shaped channel is:

[0049] A. Four simulated rod bundles are placed in the calibration box to form a special-shaped rod bundle channel, and then an insulating rod is used to simulate the bubbles in the special-shaped rod bundle channel. Insulating rods of different diameters are moved in the special-shaped rod bundle channel to measure dynamic points, and multiple insulating rods are clustered together to measure static points.

[0050] In the actual calibration process, the measured voltage is normalized using the following formula:

[0051]

[0052] In formula (1), V represents the voltage measured in real time, V * Represents the normalized voltage, V min The minimum voltage is when it is filled with air, V max The maximum voltage is when it is full of water; then MATLAB is used to normalize the voltage V under different working conditions. * Processing is performed to obtain a calibration curve of normalized voltage.

[0053] B. Figure 6 As shown, circles of different sizes can be filled in the channel of the special-shaped rod bundle to simulate the experimental process of bubbles passing through. Due to the influence of bubbles on the electric field in the channel, the electric field norm at the receiving electrode is measured by multi-physics field calculation software and integrated. From the integral relationship, it can be seen that the measured voltage is:

[0054]

[0055] In formula (2), V n Indicates the measured voltage, represents the electric field norm.

[0056] After calculation, the voltage under different numbers of bubbles is matched with the electrode group to obtain a simulated calibration curve.

[0057] In this embodiment, since there is uncertainty at points with fewer electrodes due to uneven electric field distribution, the calibration curve of the normalized voltage and the simulated calibration curve are sorted to obtain the calibration curve of the special-shaped rod bundle channel.

[0058] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel, wherein a first electrode group is attached to the side of the first rod bundle facing the special-shaped rod bundle channel, a second electrode group is attached to the side of the second rod bundle facing the special-shaped rod bundle channel, a third electrode group is attached to the side of the bent rod bundle facing the special-shaped rod bundle channel, and a fourth electrode group is attached to the side of the fourth rod bundle facing the special-shaped rod bundle channel, characterized in that: The first electrode group and the fourth electrode group each include two electrodes, and the second electrode group and the third electrode group each include three electrodes; The line connecting the center of the first rod bundle and the center of the fourth rod bundle is used as the dividing line, the five electrodes on the right side of the dividing line are the excitation electrodes, and the five electrodes on the left side of the dividing line are the receiving electrodes; In the nuclear reactor, when no deformation occurs, four adjacent rod bundles are marked as a first rod bundle, a second rod bundle, a third rod bundle, and a fourth rod bundle, respectively, and a single rod bundle channel is formed in the middle; When the third rod bundle is deformed, the mark is updated to a bent rod bundle, the positions and marks of the first rod bundle, the second rod bundle and the fourth rod bundle remain unchanged, and a special-shaped rod bundle channel is formed in the middle.

2. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel according to claim 1, characterized in that: Each of the electrode groups is respectively connected to a corresponding signal processing circuit. The signal processing circuit measures the voltage signal on each electrode and sends it to a data acquisition card. The controller obtains the voltage signal through the data acquisition card and obtains the two-phase flow characteristics of the special-shaped rod bundle channel by calibrating the voltage signal.

3. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel according to claim 1, characterized in that: The angle between adjacent electrodes in each electrode group is 30°.

4. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel according to claim 2, characterized in that: The signal processing circuit includes a signal source for providing an excitation current signal, a gate array for controlling an excitation electrode, a gate array for controlling a receiving electrode, an interface for communication and a control core for logic control.

5. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel according to claim 4, characterized in that: The signal source is composed of two operational amplifiers, one of which is configured as a Howland circuit to form a current source; and the other operational amplifier is configured as a follower.

6. A two-phase flow measurement system for a nuclear reactor special-shaped rod bundle channel according to claim 4, characterized in that: The control core is a micro signal processor MSP430, which is used to complete the control instruction generation, data / command communication, and synchronous trigger signal generation of the gate array.

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