Flow measurement device of fast reactor

Abstract

To measure a flow rate of coolant accurately.SOLUTION: A flow measurement device 100 of fast reactor comprises: a flow rate measurement part 131 for measuring flow rate of coolant in a reflow piping 4 connecting a secondary system pump 2 circulating liquid metal sodium provided in the fast reactor as coolant and main piping 3 for supplying coolant to the secondary system pump 2, the reflow piping for reflowing coolant flowing in above a bearing 23 provided in the secondary system pump 2 to the main piping 3; a liquid level measurement part 132 for measuring liquid level of surface of coolant within the secondary system pump 2 to thereby generate liquid level data indicative of relation between time and liquid level; a change amount calculation part 133 for calculating a change amount of flow rate of coolant in the reflow piping 4 on the basis of differential data obtained by incompletely differentiating the liquid level data; and a main piping flow rate calculation part 134 for calculating flow rate of coolant in the main piping 3 on the basis of the measured flow rate of coolant and the calculated change mount of the flow rate of coolant.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a flow measurement device for a fast reactor. [Background technology]

[0002] In fast reactors that use liquid metal sodium as a coolant, the flow rate of the main pipe connected to the pump that circulates the coolant is measured. For example, Patent Document 1 discloses that the flow rate of the main system is calculated based on the flow rate of the coolant measured by a flow meter provided in a return pipe that connects the pump to the main system and returns the coolant from the pump to the main system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-210261 Summary of the Invention [Problem to be solved by the invention]

[0004] When the flow rate in the main pipe is constant, the level of the coolant inside the pump is also constant, but when the flow rate in the main pipe changes, the level of the coolant inside the pump also changes.When the level of the coolant inside the pump changes, the flow rate of the coolant flowing into the return pipe also changes, resulting in a problem that the flow rate of the main pipe calculated based on the flow rate of the coolant in the return pipe deviates from the actual flow rate of the coolant in the main pipe.

[0005] The present invention has been made in consideration of these points, and has as its object to measure the flow rate of a coolant with high accuracy. [Means for solving the problem]

[0006] A flow rate measurement device for a fast reactor according to a first aspect of the present invention includes: a flow rate measurement unit that measures a flow rate of the coolant in a return pipe that connects a pump that circulates liquid metal sodium as a coolant provided in the fast reactor to a main pipe that supplies the coolant to the pump and returns the coolant that has flowed above a bearing provided in the pump to the main pipe; a liquid level measurement unit that generates liquid level data that indicates a relationship between time and the liquid level by measuring a liquid level of the coolant inside the pump; a change amount calculation unit that calculates a change amount of the coolant flow rate in the return pipe based on differential data obtained by imperfectly differentiating the liquid level data generated by the liquid level measurement unit; and a main pipe flow rate calculation unit that calculates the coolant flow rate in the main pipe based on the coolant flow rate measured by the flow rate measurement unit and the change amount of the coolant flow rate calculated by the change amount calculation unit.

[0007] The change amount calculation unit may calculate the change amount of the coolant flow rate by multiplying the rate of change of the liquid level indicated by the differential data by the cross-sectional area of ​​the casing of the pump, and the main piping flow rate calculation unit may calculate the flow rate of the coolant in the main piping by subtracting the change amount of the coolant flow rate calculated by the change amount calculation unit from the flow rate of the coolant and multiplying the subtraction result by a predetermined coefficient.

[0008] The change amount calculation unit may calculate in advance the frequency of the liquid level fluctuation based on the liquid level data, and perform inexact differentiation of the liquid level data so as to smooth the liquid level fluctuation at higher frequencies including the calculated frequency.

[0009] The main piping flow rate calculation unit may set a rated power operation flow rate, which is the flow rate of the coolant in the main piping when the pump rotation speed during rated power operation of the fast reactor reaches the rated rotation speed, as 100% of the flow rate measurement range, and calculate a ratio of the calculated coolant flow rate to the rated power operation flow rate. [Effects of the Invention]

[0010] According to the present invention, it is possible to measure the flow rate of the coolant with high accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing a piping system around a pump of a secondary main cooling system. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a flow rate measuring device. [Figure 3] FIG. 10 is a diagram showing simulation results of the flow rate of sodium in the main pipe and the reflux pipe of the fast reactor according to the present embodiment and the flow rate of sodium measured by a flow rate measuring device. [Figure 4] 4 is a flowchart showing a processing flow in the flow measurement device. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Outline of the piping system for the secondary main cooling system of a fast reactor] The flow rate measuring device 100 for a fast reactor according to this embodiment is a device that is installed in a fast reactor and measures the flow rate of coolant in a main pipe through which liquid metal sodium circulates as coolant inside the fast reactor. In explaining the flow rate measuring device 100 for a fast reactor, the piping system of the secondary main cooling system of the fast reactor will be explained with reference to the drawings. In the following explanation, the flow rate measuring device 100 for a fast reactor will also be simply referred to as the flow rate measuring device 100. Liquid metal sodium will also be simply referred to as sodium.

[0013] Figure 1 shows the piping system around the pump in the secondary main cooling system of a fast reactor. As shown in Figure 1, the secondary main cooling system 1 of the fast reactor is provided with a secondary system pump 2, a main pipe 3, a return pipe 4, a pump overflow column 5, a level setting valve 6, a flow meter 7, and a level gauge 8.

[0014] The secondary pump 2 circulates sodium and has a casing 21, a shaft 22, a bearing 23, and an impeller 24. The secondary pump 2 is, for example, a vertical free-level centrifugal pump having a free liquid level of liquid metal sodium within the casing 21 and a sealed cover gas above the free liquid level to absorb the increase in volume of the liquid metal sodium due to thermal expansion.

[0015] A shaft 22, a bearing 23, and an impeller 24 are housed inside the casing 21. The shaft 22 is supported by the bearing 23, and the impeller 24 is provided at the tip of the shaft 22. The shaft 22 and the impeller 24 rotate under the control of a pump control device (not shown). As the impeller 24 rotates, sodium guided from the main pipe 3 into the inside of the casing 21 is pumped to the intermediate heat exchanger.

[0016] The main pipe 3 is connected to the secondary system pump 2 and the steam generator, and supplies low-temperature sodium that has passed through the steam generator to the secondary system pump 2. The return pipe 4 is connected to the main pipe 3 and to a position in the casing 21 above the bearing 23. The return pipe 4 is also provided with a pump overflow column 5 for removing bubbles that have formed in the pipe, a level setting valve 6, and a flow meter 7. The return pipe 4 returns leak flow sodium, which is sodium that has leaked upward from the gap between the casing 21 and the bearing 23 and the gap between the bearing 23 and the shaft 22, to the main pipe 3 via the pump overflow column 5 and the level setting valve 6.

[0017] The flow meter 7 measures the flow rate of sodium flowing through the reflux pipe 4 and outputs information indicating the measured flow rate to the flow measurement device 100. The level meter 8 measures the level of the sodium liquid inside the secondary pump 2. For example, the level meter 8 has a displacement sensor housed inside a guide tube (not shown) provided inside the casing 21. The level meter 8 measures the level of the sodium liquid by generating electromagnetic induction using a coil provided in the displacement sensor and detecting eddy currents generated in the sodium. The level meter 8 outputs information indicating the measured level of the sodium liquid to the flow measuring device 100.

[0018] 2 is a diagram showing the configuration of the flow measurement device 100. The flow measurement device 100 is, for example, a computer, and includes a communication unit 110, a storage unit 120, and a control unit . The communication unit 110 is a communication interface that enables the flow measurement device 100 to communicate with other devices such as the flow meter 7 and the level meter 8, for example.

[0019] The storage unit 120 is, for example, a read-only memory (ROM) and a random access memory (RAM). The storage unit 120 stores various programs for causing the flow measurement device 100 to function. The storage unit 120 stores programs for causing the control unit 130 of the flow measurement device 100 to function as a flow rate measurement unit 131, a liquid level measurement unit 132, a change amount calculation unit 133, a main pipe flow rate calculation unit 134, and an output unit 135.

[0020] The control unit 130 is, for example, a CPU (Central Processing Unit). The control unit 130 executes the program stored in the storage unit 120, causing the control unit 130 of the flow measurement device 100 to function as a flow rate measurement unit 131, a liquid level measurement unit 132, a change amount calculation unit 133, a main pipe flow rate calculation unit 134, and an output unit 135.

[0021] The flow rate measuring unit 131 measures the flow rate of sodium as a coolant in the return pipe 4. Specifically, the flow rate measuring unit 131 measures the flow rate of sodium in the return pipe 4 by acquiring, via the communication unit 110, from the flow meter 7, information indicating the flow rate of sodium measured by the flow meter 7.

[0022] The liquid level measuring unit 132 generates liquid level data indicating the relationship between time and liquid level by measuring the liquid level of the sodium inside the secondary pump 2. Specifically, the liquid level measuring unit 132 acquires information indicating the liquid level of the sodium inside the secondary pump 2 measured by the liquid level gauge 8 from the liquid level gauge 8 at predetermined time intervals (for example, every few tens of milliseconds) via the communication unit 110. The liquid level measuring unit 132 generates liquid level data that associates the time at which the information indicating the liquid level was acquired with the liquid level corresponding to that time.

[0023] The flow rate measuring unit 131 may adjust the scale of the flow rate acquired from the flow meter 7. Similarly, the liquid level measuring unit 132 may adjust the scale of the liquid level acquired from the liquid level meter 8 in accordance with the scale adjusted by the flow rate measuring unit 131.

[0024] The change amount calculation unit 133 calculates the amount of change in the flow rate of sodium in the reflux pipe 4 based on the differential data obtained by incompletely differentiating the liquid level data generated by the liquid level measurement unit 132. Specifically, the change amount calculation unit 133 first calculates in advance the frequency of the liquid level fluctuation based on the liquid level data. The frequency of the liquid level fluctuation is the frequency of the liquid level fluctuation that is not accompanied by a change in the power output of the fast reactor, and is, for example, a frequency that corresponds to the liquid level pulsation that is accompanied by the vibration of the secondary system pump 2 or the like.

[0025] Then, the change amount calculation unit 133 generates differential data indicating the rate of change of the liquid level by performing imperfect differentiation of the liquid level data using an imperfect differentiator that differentiates after passing the data through a low-pass filter so as to smooth fluctuations in the liquid level corresponding to frequencies equal to or higher than the calculated frequency. Here, the imperfect differentiator is represented by the transfer function of the following equation (1): T D is the differential time, and η is the inverse of the differential gain, which are set based on the calculated frequency of the liquid level fluctuation.

[0026]

number

[0027] Then, the change amount calculation unit 133 calculates the change amount of the flow rate of sodium by multiplying the rate of change of the liquid level indicated by the generated differential data by the cross-sectional area of ​​the casing 21 of the secondary pump 2. Here, it is assumed that the cross-sectional area of ​​the casing 21 of the secondary pump 2 is constant in the height direction of the casing 21.

[0028] The main pipe flow rate calculation unit 134 calculates the flow rate of sodium in the main pipe 3 based on the flow rate of sodium measured by the flow rate measurement unit 131 and the amount of change in the flow rate of sodium calculated by the amount of change calculation unit 133. The main pipe flow rate calculation unit 134 calculates the flow rate of leak flow sodium in the secondary system pump 2 by subtracting the amount of change in the flow rate of sodium calculated by the amount of change calculation unit 133 from the flow rate of sodium measured by the flow rate measurement unit 131. The main pipe flow rate calculation unit 134 calculates the flow rate of sodium in the main pipe 3 by further multiplying the calculated flow rate of leak flow sodium by a predetermined coefficient corresponding to the ratio between the flow rate in the main pipe 3 and the flow rate of leak flow sodium.

[0029] Then, the main piping flow rate calculation unit 134 sets the flow rate during rated power operation, which is the flow rate of sodium in the main piping 3 when the rotation speed of the pump during rated power operation of the fast reactor reaches the rated rotation speed, as the 100% flow rate in the flow rate measurement range. Then, the main piping flow rate calculation unit 134 calculates the ratio of the calculated sodium flow rate to the flow rate during rated power operation.

[0030] For example, flow rate information indicating the flow rate of sodium in the main pipe 3 calculated by the main pipe flow rate calculation unit 134 when the rotation speed of the secondary system pump 2 during rated power operation of the fast reactor reaches the rated rotation speed is stored in advance in the storage unit 120. Then, the main pipe flow rate calculation unit 134 calculates the ratio of the calculated flow rate of sodium in the main pipe 3 to the flow rate during rated power operation indicated by the flow rate information stored in the storage unit 120.

[0031] 3 is a diagram showing the results of a simulation of the flow rates of sodium in the main pipe 3 and the reflux pipe 4 of the fast reactor according to this embodiment, and the flow rate of sodium measured by the flow rate measuring device 100. The example shown in FIG. 3 shows the change in the flow rate ratio over time when the power is reduced from rated power operation. In the graph shown in FIG. 3, the solid line indicates the flow rate ratio in the main pipe 3, the dashed line indicates the flow rate ratio in the main pipe 3 calculated by the flow rate measuring device 100, and the dashed-dotted line indicates the flow rate ratio in the reflux pipe 4. It is assumed that the sodium level in the secondary system pump 2 is set high by the level setting valve 6.

[0032] When the flow rate of sodium in the main pipe 3 changes, the change in the flow rate of sodium in the reflux pipe 4 lags behind the change in the flow rate of sodium in the main pipe 3. For example, when the power of a fast reactor is reduced from rated power operation, the decrease in the flow rate of sodium in the reflux pipe 4 lags behind the decrease in the flow rate of sodium in the main pipe 3. As a result, as shown in Figure 3, the ratio of the flow rate of sodium in the reflux pipe 4 to that in rated power operation becomes higher than the ratio of the flow rate of sodium in the main pipe 3 to that in rated power operation.

[0033] In contrast to this, the flow rate measuring device 100 performs correction using the inexact differentiation of the sodium level in the secondary pump 2 with respect to the flow rate in the return pipe 4, thereby making it possible to obtain a measurement result that is close to the ratio of the flow rate in the main pipe 3, as shown in Fig. 3. When the sodium level in the secondary pump 2 is set low by the level setting valve 6, the flow rate in the return pipe 4 decreases faster than the flow rate in the main pipe 3, in contrast to when the sodium level is set high. Even in this case, the flow rate measuring device 100 can obtain a measurement result that is close to the ratio of the flow rate in the main pipe 3, based on the flow rate in the return pipe 4.

[0034] The output unit 135 outputs flow rate information indicating the ratio of the flow rate calculated by the main pipe flow rate calculation unit 134. For example, the output unit 135 outputs the flow rate information to a display device (not shown) via the communication unit 110.

[0035] [Operation flow] Next, a description will be given of the flow of processing in the flow measurement device 100. Fig. 4 is a flowchart showing the flow of processing in the flow measurement device 100. The flowchart shown in Fig. 4 is assumed to be executed repeatedly. First, the flow rate measuring unit 131 measures the flow rate of sodium in the reflux piping 4 (S1). In parallel with the measurement of the flow rate of sodium in the reflux piping 4 by the flow rate measuring unit 131, the liquid level measuring unit 132 measures the liquid level of sodium inside the secondary pump 2, thereby generating liquid level data indicating the relationship between time and liquid level (S2).

[0036] The change amount calculation unit 133 calculates the rate of change of the liquid level by generating differential data indicating the rate of change of the liquid level by performing inexact differentiation of the liquid level data generated in S2 (S3). The change amount calculation unit 133 calculates the amount of change of the flow rate of sodium by multiplying the rate of change of the liquid level indicated by the differential data generated in S3 by the cross-sectional area of ​​the casing 21 of the secondary pump 2 (S4).

[0037] The main pipe flow rate calculation unit 134 subtracts the multiplication result in S4 from the sodium flow rate measured in S1, and multiplies the subtraction result by a predetermined coefficient to calculate the sodium flow rate in the main pipe 3 (S5). The main pipe flow rate calculation unit 134 calculates the ratio of the calculated sodium flow rate in the main pipe 3 to the flow rate during rated power operation (S6). The output unit 135 outputs the calculation result in S6 as information indicating the sodium flow rate in the main pipe 3 (S7).

[0038] [Effects of this embodiment] As described above, the flow rate measuring device 100 for a fast reactor according to this embodiment includes a change amount calculating unit 133 that calculates a change amount of the coolant flow rate in the return pipe 4 based on differential data obtained by imperfectly differentiating liquid level data generated by measuring the liquid level of the coolant inside the secondary pump 2, and a main pipe flow rate calculating unit 134 that calculates the coolant flow rate in the main pipe 3 based on the coolant flow rate measured by the flow rate measuring unit 131 and the change amount of the coolant flow rate calculated by the change amount calculating unit 133. In this way, the main pipe flow rate calculating unit 134 calculates the change amount of the coolant flow rate in the return pipe 4 based on the differential data obtained by imperfectly differentiating the liquid level data, thereby correcting the discrepancy between the coolant flow rate in the main pipe 3 and the coolant flow rate in the return pipe 4 that occurs in response to a change in the coolant flow rate in the main pipe 3, and therefore the coolant flow rate can be measured with high accuracy.

[0039] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist. For example, in the above embodiments, the flow rate measuring device 100 has been described as measuring the flow rate of the main pipe 3 in the secondary main cooling system, but is not limited to this.

[0040] The flow measurement device 100 may measure the flow rate of the main pipe in the primary main cooling system. In this case, the flow measurement device 100 may include a flow rate measurement unit that measures the flow rate of the coolant in a return pipe that connects the primary pump and the main pipe that supplies coolant to the primary pump and returns the coolant that has flowed above a bearing provided in the primary pump to the main pipe; a liquid level measurement unit that generates liquid level data indicating the relationship between time and the liquid level by measuring the liquid level of the coolant inside the primary pump; a change amount calculation unit that calculates the amount of change in the flow rate of the coolant in the return pipe based on differential data obtained by imperfectly differentiating the liquid level data; and a main pipe flow rate calculation unit that calculates the flow rate of the coolant in the main pipe based on the coolant flow rate measured by the flow rate measurement unit and the amount of change in the coolant flow rate calculated by the change amount calculation unit. In this manner, the flow measurement device 100 can accurately measure the flow rate of the main pipe in the primary main cooling system.

[0041] Furthermore, all or part of the device can be configured in any unit, functionally or physically, distributed or integrated. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0042] 1 Secondary main cooling system 2 Secondary pump 3 Main piping 4 Reflux piping 5. Pump overflow column 6 Level setting valve 7 Flowmeter 8 Liquid level gauge 100 Flow measuring device 110 Communications Department 120 Storage section 130 Control Unit 131 Flow measurement section 132 Liquid level measurement section 133 Change amount calculation unit 134 Main piping flow rate calculation section 135 Output section

Claims

1. a flow rate measuring unit that connects a pump that circulates liquid metal sodium as a coolant provided in a fast reactor to a main pipe that supplies the coolant to the pump, and that measures a flow rate of the coolant in a return pipe that returns the coolant that has flowed above a bearing provided in the pump to the main pipe; a liquid level measuring unit that measures the liquid level of the coolant inside the pump and generates liquid level data that indicates a relationship between time and the liquid level; a change amount calculation unit that calculates a change amount of the coolant flow rate in the return pipe based on differential data obtained by incompletely differentiating the liquid level data generated by the liquid level measurement unit; a main pipe flow rate calculation unit that calculates the flow rate of the coolant in the main pipe based on the flow rate of the coolant measured by the flow rate measurement unit and the amount of change in the flow rate of the coolant calculated by the amount of change calculation unit; A flow rate measuring device for a fast reactor having the same.

2. the change amount calculation unit calculates a change amount of the coolant flow rate by multiplying a rate of change of the liquid level indicated by the differential data by a cross-sectional area of ​​a casing of the pump; the main pipe flow rate calculation unit subtracts the amount of change in the coolant flow rate calculated by the change amount calculation unit from the coolant flow rate, and multiplies the result of the subtraction by a predetermined coefficient to calculate the coolant flow rate in the main pipe. The flow rate measuring device for a fast reactor according to claim 1.

3. the change amount calculation unit calculates in advance a frequency of the liquid level fluctuation based on the liquid level data, and performs inexact differentiation of the liquid level data so as to smooth the liquid level fluctuation of a higher frequency including the calculated frequency. The flow rate measuring device for a fast reactor according to claim 1.

4. the main piping flow rate calculation unit defines a rated power operation flow rate, which is the flow rate of the coolant in the main piping when the rotation speed of the pump during rated power operation of the fast reactor reaches the rated rotation speed, as 100% of the flow rate measurement range, and calculates a ratio of the calculated coolant flow rate to the rated power operation flow rate; The flow rate measuring device for a fast reactor according to claim 1.

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