JPS6398519A - Liquid metal flow rate measuring device of high speed breeder reactor - Google Patents

Abstract

PURPOSE:To obtain the flow rate output and temp. output in an average flow speed region, by arranging an eddy current type flowmeter and a thermometer in the same well at the place in piping generating the average flow speed of a liquid metal. CONSTITUTION:A structure wherein a thermocouple type thermometer 19 is provided in the same well as an eddy current type flowmeter is incorporated in a measuring pipe 4. The output voltages from the secondary coils 9, 10 of the eddy current type flowmeter are converted by a flow rate converter 12 to be outputted to a temp. compensation device 21. The output signal from the thermocouple type thermometer 19 is converted by a temp. converter 20 to be outputted to the temp. compensation device 21. In the temp. compensation device 21, the signal from the flow rate converter 12 is compensated by the signal from the temp. converter 20 to be outputted as a flow rate signal improved in accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to measuring the flow rate of liquid metal in a fast breeder reactor, and particularly to a flow meter suitable for measuring the flow rate in large-diameter piping.

[Conventional technology]

Conventionally, electromagnetic flowmeters have been mainly used as liquid metal (sodium) flowmeters in liquid metal cooled fast breeder reactors. Excitation power source 1. Excitation coil 2. When liquid flows through the measurement tube 4 to which a magnetic field is applied perpendicularly to the flow direction by an electromagnet consisting of a core 3 and a magnetic field perpendicular to the flow direction, an electromotive force proportional to the flow rate of the liquid is induced in the liquid. This electromotive force is detected by a pair of electrodes 5 and 6 placed opposite each other in a position perpendicular to the flow direction of the measuring tube 4 in the magnetic field, and converted by the flow rate converter 7 to calculate the volumetric flow rate. It is something to be measured.

[Problem that the invention seeks to solve]

When measuring the flow rate of liquid metal in large-diameter piping using an electromagnetic flowmeter, it is necessary to calibrate the actual flow because the linearity between the flow rate and the output electromotive force cannot be maintained. There were problems in that an actual flow calibration test had to be performed using a large-scale device, and that measurement performance deteriorated due to increased fluid temperature dependence and fluctuation of the output electromotive force.

In addition, there is an ultrasonic flowmeter as a large-mouth, large-pipe directional flowmeter. An ultrasonic flow meter has an ultrasonic transmitter and receiver attached to the outer wall of a pipe, and utilizes the principle that the apparent propagation speed of ultrasonic waves varies depending on the velocity of the fluid. In addition to the fact that the propagation velocity of an ultrasonic flow meter changes depending on the temperature,
Measurement errors occur when the wall thickness of the piping changes due to corrosion or adhered substances, and correction is also extremely complicated.

The purpose of the present invention is to achieve high reliability and good measurement performance with simple correction even in the measurement of liquid metal flow rate in large-diameter piping, and to
The object of the present invention is to provide a flowmeter that does not require actual flow calibration.

[Means for solving problems]

The above purpose is to use an eddy current flowmeter to measure the flow rate, install the eddy current flowmeter at a point in the pipe that indicates the average flow velocity, and also install a thermometer in the same well, and collect the output signal from the thermometer. and a flow rate signal that fluctuates due to changes in fluid temperature. In addition, in the specific example, the flow velocity in the pipe is the fastest in the center of the pipe and becomes slower as it approaches the periphery, so the average flow velocity in the pipe is determined by the following method. .

(1) Install a flow meter and a thermometer at a location that indicates the average flow velocity in the pipe (at any location on the same circumference).

Or (2) Install multiple flowmeters and thermometers in the radial direction within the piping and average the output signals.

[Effect]

Eddy current flowmeters have the detection end installed inside the measurement tube, and the output characteristics essentially do not change even if the measurement tube has a large diameter, so there is no need to perform actual flow calibration. Both signals can be taken out so that a change in the flowmeter output due to the change can be compensated for by both signals from the thermocouple thermometer provided in the same well of the eddy current flowmeter.

Furthermore, with respect to the redundancy required when applied to a nuclear reactor, since the flowmeter is small, reliability can be easily improved by installing it to indicate the average flow velocity in the piping.

[Example] Hereinafter, a specific example of the present invention will be described with reference to FIGS. 1, 2, and 5.
This will be explained with reference to FIGS. 6 and 7.

FIG. 6 shows a principle diagram of an eddy current flowmeter. The eddy current flowmeter has the same detection principle as the eddy current flowmeter used as the fuel assembly outlet flowmeter, and the primary coil 8,
Secondary coil 9, 10. Primary power supply 11. It is composed of a flow rate converter 12 and a well 13. The primary coil 8 is AC excited by the primary power source 11.aThe secondary coil 9 and the secondary coil 10 form a differential coil, so the well 13
When there is no flow in the external fluid, voltage is induced in the secondary coils 9 and 10 by the magnetic field of the current flowing through the primary coil 8, but the induced voltage in the secondary coil 9 and the induced voltage in the secondary coil 1o are Since there is no potential difference, the voltage output to the flow rate converter 12 is canceled out and becomes zero. However, when the fluid is flowing, for example, in the direction shown by the solid line 14, and the magnetic field by the primary coil is created in the direction shown by the dotted chain a15, the magnetic field by the primary coil and the fluid intersect.

Eddy currents are generated in the directions shown in the two-point silver fi16.17. The direction of this eddy current is opposite in the vicinity of the secondary coil 9 and in the vicinity of the secondary coil 10 because the direction of the magnetic field where the fluid intersects is different. The magnetic field caused by these eddy currents acts in the direction of canceling the magnetic field caused by the current flowing through the primary coil 8 near the secondary coil 9, and acts in the direction of being added to the magnetic field caused by the current flowing through the primary coil 8 near the secondary coil 10. work.

As a result, a potential difference occurs between the induced voltage of the secondary coil 9 and the induced voltage of the secondary coil 10, which is sent to the flow rate converter 12 as an output voltage. This output voltage is proportional to the fluid flow rate and is converted by the flow rate converter 12.

Further, as shown in FIG. 5, the output from the flow rate converter 12 fluctuates due to changes in fluid temperature. This is because the electrical resistance of the fluid changes due to changes in fluid temperature.

The main cause is fluctuations in the magnitude of eddy currents, and in order to accurately measure the flow rate, it is necessary to temperature compensate the output signal from the flow rate converter 12.

FIG. 1 is a diagram in which an eddy current flowmeter and a thermocouple thermometer 19 provided in the same well 13 are assembled into a measuring tube 4. Furthermore, since the flow velocity of the fluid increases as it approaches the center of the measuring tube 4, the drawing shows an average flow velocity source and four flowmeters. A plurality of flowmeters are installed in the measurement pipe, and the output from each flowmeter is output to the calculator 22. As shown by the arrows in FIG. 7, the flow velocity in the pipe is fast in the center and slows down as it approaches the periphery. The arithmetic unit 22 detects the distribution of flow velocity and outputs it to the flow rate converter 12 as an output signal based on the average flow velocity. Suitable for a wide range of applications where changes in flow velocity distribution within the pipe cannot be ignored. Output voltages from the secondary coils 9 and 10 of the eddy current flowmeter are converted by a flow rate converter 12 and output to a temperature compensator 21. The output signal from the thermocouple thermometer 19 is converted by a temperature converter 20 and output to a temperature compensator 21.

It can also be used as a temperature signal if necessary.

The temperature compensator 21 compensates the signal from the flow rate converter 12 with the signal from the temperature converter 20 and outputs it as a highly accurate flow rate signal.

The temperature compensator 21 corrects the change in the flow rate-output characteristic depending on the temperature of the fluid as shown in FIG. 5, and the configuration is shown in FIG. Multiplied by the temperature signal passed through function generator 30. As a result, the gradient of the flow rate-output characteristic shown in FIG. 5 is corrected by temperature, and the flow rate-output characteristic shown in FIG. 9, which is independent of temperature, is obtained.

The function generator 30 is used to correct when the temperature dependence of the flow rate-output characteristic includes nonlinearity, and can be omitted when the nonlinearity is small.

According to this example, even when measuring the flow rate of liquid metal in large-diameter piping, the flow rate can be measured with high accuracy even if the output characteristics may change significantly, and if it is desired to measure the temperature in addition to the flow rate, temperature compensation can be used. Since the signal from the thermometer in use can be used, there are effects such as the ability to reduce the amount of material used.

〔Effect of the invention〕

As described above, according to the present invention, since it is possible to obtain the flow rate output and temperature output in the average flow velocity range, the need for actual flow calibration can be reduced without significantly changing the output characteristics.
Since the surface output is obtained in the same range and in the average flow velocity range, there is an effect that the accuracy when the surface output is used for temperature compensation is improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view in the fluid flow direction and a signal processing diagram of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line 1-1 in FIG. 1, and FIG.
The figure shows the principle of an electromagnetic flowmeter, and Figure 4 shows the flow velocity of an electromagnetic flowmeter.
Output electromotive force graph, Figure 5 shows the flow rate of the eddy current flowmeter.
Flow converter output graph diagram, Figure 6 is a principle diagram of an eddy current flowmeter, and Figure 7 is a cross-sectional diagram in the fluid flow direction and signal processing diagram when multiple flowmeters are installed in consideration of flow velocity distribution. , 8th
The figure is a detailed block diagram of the temperature compensator circuit in Figure 1, and Figure 9 is a detailed block diagram of the temperature compensator circuit in Figure 1.
The figure is a flow rate-output characteristic graph diagram after temperature correction. 4...Measuring tube, 8...Primary coil, 9, 10...
Secondary coil, 12...Flow rate converter, 19...Thermocouple thermometer, 20...Temperature converter, 21...Temperature compensator, -°, Agent Patent attorney Katsuma Ogawa ゝ'□・1.・
Nocha (mouth 2 (...Naedo Yuzu Compensation) 9...Juku τ light to Yi A needle 7 Kasumi 3rd Z Rikuori member Koi 1 Shi 1 Shiki V fruit 4 Yasa I what conflict At present, it's a bit boring.

Claims (1)

[Claims] 1. A nuclear reactor equipped with a fast breeder reactor that uses liquid metal as a coolant and piping through which the liquid metal flows,
An eddy current flowmeter and a thermometer are installed in the same well at or near a location in the piping where the average flow velocity of the liquid metal occurs, and the output lines of both measuring devices are brought out of the piping. A liquid metal flow rate measurement device for a fast breeder reactor characterized by the following features: 2. In claim 1, the output lines of both of the measuring devices are connected to the input side of the temperature compensator of the eddy current flowmeter to be taken out of the piping. A liquid metal flow rate measurement device for a fast breeder reactor.