JPS6129798A - Controller for flow rate at core for nuclear power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a core flow rate control Il device for a nuclear power plant, and particularly to a system for controlling the flow of coolant in a core coolant flow path.
: Detects the flow rate fluctuation of the coolant, and based on this, the flow rate i
The present invention relates to a core flow rate control device for a nuclear power plant that performs lJ'aI.

[Technical background of the invention and its problems] In general, in nuclear power plants, the core coolant flow path is very complex and forms parallel flow paths, so when the coolant flow condition changes, the pump Even if the rotational speed is constant, small sudden fluctuations may occur in the coolant flow ω.

Such a sudden change in the coolant flow rate causes a change in the core coolant temperature distribution in the reactor core within a short period of time as the coolant passes through the core, and the resulting change in reactivity causes the neutron flux to change. results in fluctuations.

This variation in neutron flux further causes variation in coolant temperature, and due to the reactivity effect caused by this, variation in neutron flux is
This continues until the initial reactivity disturbance is compensated for, generally causing peak-like fluctuations.

For example, in a nuclear power plant, there are two coolant channels, each consisting of one coolant-driven pump and multiple fluid systems in several layers, creating a flow that recirculates within the reactor vessel. think about.

In such a system, the outlet piping of the coolant-driven pump in a3 is provided with a branch part in the middle. When a vortex is generated in the flow at this branch, a pressure loss occurs at this branch, and even when the rotation speed of the coolant drive pump is the same, the flow rate of the cold 7j'l material changes.

Therefore, if the operation is in a state where there is a vortex during rated operation, that is, a state where the pressure drop is large, and for some reason a transition occurs at this branch part to a state where there is no vortex, that is, a state where the pressure drop is small, The coolant flow rate suddenly increases, which causes a sudden and variable increase in the core flow rate.

For example, in a boiling water reactor, changes in core flow rate result in changes in the behavior of steam bubbles within the reactor core, resulting in changes in neutron flux. Therefore, a sudden fluctuating increase in core flow rate can also cause a sudden fluctuating increase in neutron flux to cause IC, and an alarm or °C due to high neutron flux can cause a scram.

Since such scrams are undesirable because they cause a decrease in the operating rate of the power plant, there has been a desire for a device that can avoid such a situation.

Note that FIG. 6 shows the change in neutron flux due to the aforementioned sudden change in the coolant flow rate, where the curve a shows the change in the neutron flux, and the curve 2 shows the sudden change in the coolant flow rate.

[Object of the Invention] The present invention has been made in order to cope with the conventional situation. It is an object of the present invention to provide a core control device for a nuclear power plant that can appropriately control the core flow rate.

[Summary of the Invention] That is, the present invention includes a flow rate fluctuation detection means for detecting a flow rate fluctuation of coolant due to turbulence in the flow of coolant in a core coolant flow path and outputting a flow rate fluctuation signal, and a flow rate fluctuation signal inputted to the flow rate fluctuation signal. The present invention is a reactor core drift control device for a nuclear power plant, comprising a flow rate set value compensating means for outputting a flow rate compensation signal to a flow rate control system to compensate for the flow fluctuation.

[Embodiment J of the Invention Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the nuclear power plant core flow control system of the present invention, and this nuclear power plant core flow rate control is performed by flow rate fluctuation detection means 3, flow rate set value compensating means 71, and pressure setting. The main part from the point change signal generating means 5 is t.
1 has been completed.

In the figure, reference numeral C 6 indicates a recirculation pipe connected to a recirculation pump a3. This recirculation pipe 6 is branched into a plurality of parts from a branch L7, and each is connected to a jet pump.

The branching part 7 has an AE (Acoustic
n+1ssion) A sensor 8 is provided. This AE sensor 8 detects the sound generated in the branching section 7 and outputs this sound as an acoustic signal to the flow rate fluctuation detection means 3.

The flow rate fluctuation detection means 3 inputs the acoustic signal from the AE sensor 8, and determines the presence or absence of a vortex in the branch portion 7 based on this signal.

In other words, since the output of the AE sensor 8 changes depending on the state of the flow in the branch 7, by selecting a specific frequency band and determining the magnitude of the signal, it is possible to detect whether a vortex is occurring in the branch 7. It can be detected.

The flow rate fluctuation detection means 3 quickly determines the transition from a state with a vortex to a state without a vortex, for example, and sends a flow rate fluctuation signal S1 to a flow rate set value compensating means 4 and a pressure set point change signal generating means 5. Output to.

The flow rate set value compensating means 4 inputs the flow rate fluctuation signal S1 and outputs a flow rate compensation signal S2 to the flow rate control system 9.

That is, for example, when a transition occurs from a state with a vortex to a state without a vortex in the branching section 7, the magnitude of the sudden and fluctuating increase in the core flow rate is almost fixed, so it is necessary to take steps to compensate for this. A predetermined amount of flow rate compensation signal S2 is output to the flow rate control system 9.

The pressure set point change signal generating means 5 receives the flow rate fluctuation signal S1 and applies a pressure set point change signal $3 having a predetermined waveform to the pressure set point of the pressure control system 10. Core aging system for nuclear power plants
In the L device, when the flow rate fluctuation detection means 3 inputting the sound signal from the ΔE sensor 8 detects, for example, a transition from a state with a vortex to a state without a vortex in the branch part 7, this flow rate fluctuation detection means 3 outputs a flow M fluctuation signal S1 to the diversion set value compensating means 4, and the flow rate set value compensating means 4, which has input this flow rate fluctuation signal S1, outputs a flow rate compensation signal $2 to the flow rate control system 9. This reduces the recirculation pump speed and suppresses sudden fluctuations in the recirculation flow rate caused by the transition of the flow in the branch 7 to a vortex-free state.

Figure 2 shows the response when the flow rate setting value of the recirculation system is changed.
The song Field shows the variation in recirculation flow rate. As is clear from the figure, the neutron flux follows the change in the set value of the recirculation flow rate with a delay r of about 3 to 4 seconds.

Further, in this embodiment, the pressure set point change signal generating means 5 receives the flow rate fluctuation signal S1 from the flow rate fluctuation detecting means 3.
In order to alleviate the effects of sudden fluctuating flow rate changes leading to increased neutron flux, a force set point change signal S3 that temporarily lowers the force set point is output to the pressure set point of the pressure control system 10.

That is, by lowering the pressure set point in this way, the steam bubbles in the reactor core increase, and the increase in neutron flux can be suppressed due to the negative reactivity effect.

Figure 3 shows the response of the neutron flux when the pressure set point is changed. It can be seen that the neutron flux responds with a delay of about 1 to 2 seconds after the pressure set point change.

Figure 4 shows the response of the nuclear power plant when a disturbance is applied to the core flow control system of the nuclear power plant configured as described above for rapid recirculation at a rate of 2%/sec. In the figure, the curved line C indicates the variation in the neutron flux, and the curve ht indicates the variation in the recirculation flow rate.

As is clear from the figure, according to the core flow rate control device for a nuclear power plant described above, fluctuations in neutron flux can be suppressed to a very small level, and scrams can be reliably avoided.

FIG. 5 shows another embodiment of the nuclear power plant core flow rate control device of the present invention. In this embodiment, a pair of flow rate fluctuation detection means 3a and 3b are provided, and one of the flow rate fluctuation detection means 3a and 3b is provided. The means 3a receives a signal from the Δ[sensor 8] which is distributed to the branch section 7 of the A system, and the signal from the ΔF sensor 8 which is distributed to the branch section 7 of the B system. A signal is input.

Then, the flow 1 is detected from the pair of flow rate fluctuation detection means 3a13b.
Only when the fluctuation signal S1 is output at the same time, the recirculation flow rate J3 and the force setting point are changed.

゛In other words, in general, when fluctuations in flow rate occur simultaneously in the two recirculation channels of system A and J: and B, the sudden fluctuation in core flow rate becomes extremely large, and scram due to high neutron flux occurs. Although the possibility increases, the core flow 1 control device configured as described above can perform the above-mentioned control operation only in this case.

In addition, in the embodiment described below, the branch part 7 of the recirculation flow path
Although an example has been described in which the AE sensor 8 is used as a means for detecting the state of the flow, the present invention is not limited to such an embodiment, and detection can also be performed using an accelerometer, for example. Furthermore, it is also possible to directly measure the differential pressure in the branch portion 7, and it is also possible to detect it by measuring the flow rate in the coolant flow path.

[Effects of the Invention] As described above, according to the core flow rate control device for a nuclear power plant of the present invention, neutrons can be suppressed even when coolant flow fluctuations occur due to turbulence in the coolant flow in the core coolant flow path. Fluctuations in the flux can be suppressed to a minimum, and scrams in the nuclear reactor can be effectively avoided.

[Brief explanation of drawings]

Figure 1 shows an embodiment of the core flow control system for a nuclear power plant according to the present invention. Figure 2 shows a graph showing the response when changing the recirculation flow rate set value. J1.
; Figure 4 is a graph showing the response of change 11 &; Figure 4 is a graph showing the response to a single sudden fluctuation in C@recirculation by the nuclear power plant core flow control system shown in Figure 1; Figure 5 is a graph showing the response of the present invention. This is a block diagram showing an example of a core flow control system for a nuclear power plant. The sixth law is a graph showing fluctuations in neutron flux due to fluctuations in flow rate. 3.3a, 3h...Flow rate fluctuation detection means 4...Flow rate constant value compensation means 5...
......Pressure set point change signal generation means 9-
---...-...Flow control system 10...
・・・・・・Pressure control system S1・・・・・・・・・Flow rate fluctuation signal S2-・・・・・・・・・・・・Flow Φ? ili
Compensation signal S3・・・・・・・・・Pressure set point change (
Patent Attorney No. M Patent Attorney Suyama - Substitute Figure 2 Figure 3 Figure 4 Figure 6

Claims (2)

[Claims] (1) Flow rate fluctuation detection means for detecting coolant flow rate fluctuations due to disturbances in the flow of coolant in the core coolant flow path and outputting a flow rate fluctuation signal; and a means for inputting the flow rate fluctuation signal to compensate for the flow rate fluctuations. 1. A reactor core flow rate control device for a nuclear power plant, comprising: flow rate set value compensating means for outputting a flow rate compensation signal to a flow rate control system. (2) The core flow rate control device for a nuclear power plant according to claim 1, wherein the flow rate fluctuation detection means detects the flow rate fluctuation based on the presence or absence of a vortex in the coolant flow path.