JPS5837517B2 - Recirculation flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recirculation flow rate control device used for reactor power control in a boiling water nuclear power plant.

Conventional recirculation flow control devices require either a manual knob on the main controller or a manual knob on the manual/automatic switch.
Recirculation flow control is accomplished by operating the main controller in automatic mode or by a speed demand signal from the turbine inlet pressure regulator.

To increase the power of the reactor, increase the recirculation flow rate to a predetermined value of 1.
This is done by pulling the control rod at the

When power increases, if the components of the recirculation flow rate control device malfunction or fail in the direction of increasing output, or if the operator erroneously operates in the direction of increasing output, the reactor power will increase on a certain predetermined curve. The high neutron flux reaches the scram point, leading to an emergency shutdown of the reactor.

Since nuclear power plants require a large amount of capital for their equipment, it is desirable to continue operating them at as high a load factor as possible, so it is desirable to avoid emergency reactor shutdowns as much as possible.

Furthermore, if the increase in output stops near the rated output point, the fuel rods will be in a very severe thermal condition, which poses a problem in terms of ensuring safety.

The present invention was made to solve the above problems, and when the recirculation flow rate increases and the output increases due to a malfunction or failure of the component equipment of the recirculation control device or an operator's erroneous operation, a certain predetermined situation will occur. We have developed a recirculation flow rate control device that avoids an emergency shutdown of the reactor by suppressing the increase in flow rate within the specified range, and that prevents the stingers from becoming thermally severe even when the output increases near the rated output point. The purpose is to provide.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a boiling water type nuclear steam supply system using a recirculation flow rate control device 1 according to the present invention.

In FIG. 1, steam generated in a nuclear reactor 2 is sent to a turbine 4 via a main steam pipe 3, and is converted from mechanical energy to electrical energy by a generator 5.

The steam after driving the turbine 4 is condensed in a condenser 6 and returned to the reactor 2 via a water supply pipe 8 by a reactor feed water pump 7.

The turbine inlet pressure regulator 9 inputs the turbine inlet pressure signal ST from the main steam pipe 3 and the load signal SL from the turbine 4, and outputs a speed request signal SR to the recirculation flow rate control device 1.

The recirculation flow rate control device 1 also receives a core flow rate signal X and a reactor output signal y.

The above-mentioned core flow rate signal This is the signal to be used.

1, the above reactor output signal y is averaged from a plurality of signals from the local power range monitor 14 provided in the reactor core 13, and is output as a signal representing the reactor power by the average power range monitor (
APRM)15 is output.

The recirculation flow rate control device 1 changes the degree of coupling between the motor and generator of the recirculation MG device 16 based on the third input described above.

When this feed rate changes, the rotational speed of the recirculation pump motor 17 changes, and the speed of the recirculation pump 18 changes.

As a result, the flow rate of the reactor core 13 is increased or decreased, and the output of the nuclear reactor 2 is controlled.

FIG. 2 is a flowchart of the recirculation flow rate control device 1.

When a signal from the turbine inlet pressure regulator 9 is input as shown in FIG. 2, or when a manual operation is performed, a speed request signal SR is sent from the main controller 19.

This signal SR is sent to a speed request error limiter 22 via a speed request limiter 20 and a manual/automatic switch 21.

The speed request limiter 20 has a speed request signal S below a set value.
Prevent R.

When the signal SR is blocked, the manual/automatic switch 21 is switched to manual, and the speed request signal S is manually operated.
You can get R.

The speed request error limiter 22 outputs an excessive speed request signal S.
Limit R to a width within a set value.

Speed request signal S passed through the speed request error limiter 22
R' is sent to an arithmetic circuit 23 that inputs the core flow rate signal X and the reactor output signal y.

This arithmetic circuit 23 sends the reactor output signal y to the pump speed limiter 24 or sends the speed request signal SR' from the speed request error limiter 22 to the scoop tube operating device 25 according to the logic to be established next. .

FIG. 3 is a block diagram mainly depicting the arithmetic circuit 23. As shown in FIG.

The logic of this arithmetic circuit 23 determines constants A and B, and the fourth
In the figure, the range of the horizontal axis X is 0%, X≦105%, and the vertical axis y
The range of
(a) If y<y', the speed request signal SR' bypasses the pump speed limiter 24 and is sent to the scoop pipe operator 25, thereby controlling the recirculation MG device 16. The rotation speed of the recirculation pump motor 17 is increased, the speed of the recirculation pump 18 is increased, and the core flow rate is set to increase (b) If y>y', the y signal is A pump speed limit signal is sent to the speed limiter 24 and sent to the scoop tube operator 25, which controls the recirculation MG device to reduce the speed of the recirculation pump motor 17 and reduce the speed of the recirculation pump 18. is set so that the core flow rate decreases.

Furthermore, κ, X or y is x=105% or y=ii
o%, the runback signal S is sent from the arithmetic circuit 23 regardless of the speed request signal SR' or the y signal.
B is sent to pump speed limiter 24.

The pump speed limiter 24 then outputs a minimum pump speed request signal which controls the recirculation iMG device 16 to cause the recirculation pump motor 17 and recirculation pump 18 to run back to the minimum pump speed value. Decrease the rotation speed.

In the above configuration, when the reactor 2 is started and the output is increased by withdrawing the control rods, the operating point moves on the bottom pump speed constant curve 26 shown in FIG. 4, and reaches ioo% output. A point P is reached where a control rod pattern is formed.

When the output increases, the recirculation flow rate is increased and the operating point is moved from the above point P on the straight line 27 to the rated output point Q1.

During movement from point P to point Q, for example at point R in Figure 5, if the components of the recirculation flow control device malfunction or fail in the direction of increasing output, or if the operator erroneously operates in the direction of increasing output. In the conventional system, the reactor power continues to rise on the solid line 28 and reaches the high neutron scram set line 29, which causes the reactor 2 to come to an emergency shutdown.

However, in the apparatus according to the present invention, there is a limit indicated by the broken line 30 by the arithmetic circuit 23, so even if the output of the nuclear reactor increases due to the above-mentioned reasons, the solid line 28
Since the recirculation pump speed is limited to the point T where T intersects with the broken line 30, an emergency shutdown of the reactor will not occur as in the conventional system.

Even if a malfunction or malfunction as described above occurs at the rated output point Q, the output will not rise beyond the limit value indicated by the broken line 30, and an emergency shutdown of the reactor can be avoided.

Furthermore, if the reactor output signal y reaches 110% or the core flow signal You can avoid difficult situations.

As explained above, in the recirculation flow rate control device according to the present invention, the core flow rate signal X indicating the flow rate in the reactor core is
and a reactor output signal y indicating the output of the reactor,
7 is obtained from 1z y'=AX0B, and when y is larger than y', a speed request signal is sent from the arithmetic circuit to the pump speed limiter, and the pump speed limiter sends the pump to the scoop pipe operator. A speed limit signal is output to limit the speed of the recirculation pump.

When X reaches x=105% or y reaches y=iio%, a runback signal is sent from the arithmetic circuit to the pump speed limiter, and the pump minimum speed request signal is sent from the pump speed limiter to the scoop pipe. is sent to the operator and the recirculation pump speed is run back to a minimum value of 1.

If y is smaller than y', the main controller, speed demand limiter,
The speed request signal that has passed through the manual/automatic switch and the speed request error limiter is sent from the arithmetic circuit to the scoop pipe operator, and the speed of the recirculation pump is increased.

Therefore, according to the present invention, even if an increase in output occurs due to a malfunction or failure of the components of the recirculation flow rate control device or an operator's erroneous operation, an emergency shutdown of the reactor can be avoided.
Moreover, it is possible to provide a recirculation flow rate control device that does not put the fuel rods into a thermally severe state.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an embodiment of a boiling water type nuclear steam supply system using a recirculation flow rate control device according to the present invention, and Figure 2 is a block diagram of the recirculation flow rate control device of the same embodiment. FIG. 3 is a block diagram showing the arithmetic circuit of the same embodiment, and FIGS. 4 and 5 are diagrams showing the reactor power-core flow rate characteristics of the same embodiment, respectively. 1... Recirculation flow rate control device, 2... Nuclear reactor, 9...
・Turbine inlet pressure regulator, 10... Jet pump, 11... Flow rate converter, 12... Core flow meter, 13
...Reactor core, 14...Local power range monitor, 15...
・Average output area monitor, 16... Recirculation iMG device, 1
7... Recirculation pump motor, 18... Recirculation pump.

Claims (1)

[Claims] 1. In a boiling water nuclear power plant, a main controller that issues a speed request signal when a signal is input from a turbine inlet pressure regulator or during manual operation, and that prevents the speed request signal from being below a set value. A speed request limiter, a manual/automatic switch that outputs a speed request signal when a speed request signal passing through the speed request limiter is input or when a manual operation is performed, and an excessive speed among the signals from the switch outputting a speed request signal based on a speed request error limiter that limits the request signal within a set value, a core flow signal X from a core flow meter and a reactor output signal y from a reactor power detector; An arithmetic circuit that outputs a runback signal when X or y reaches a predetermined level greater than XsY at the rated output, and a speed request signal and runback signal from this arithmetic circuit are input and the pump speed is adjusted. A pump speed limiter that outputs a limit signal or a pump minimum speed request signal, a speed request signal from this pump speed limiter, and a speed request signal normally output from the above calculation circuit are input, and the speed of the recirculation pump is determined. A recirculation flow rate control device comprising: a scoop pipe operating device that outputs a control signal to a recirculation MG device installed to control the recirculation flow rate. 2 The above arithmetic circuit converts predetermined constants A,
Calculate the function value y' expressed as y' = Ax + B with B and x as variables, and compare this y' with the above reactor output signal y. If y <y', the above speed request error is calculated. Claim 1, characterized in that the pump is configured to send a speed request signal from the limiter to the scoop tube operating device, and to send a signal y to the pump speed limiter when y>y'. Recirculation flow control device as described in Section.