JPH0441798B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a reactor pressure control system for a boiling water nuclear reactor for power generation, which suppresses pressure fluctuations in a reactor pressure vessel when frequency disturbances occur in a power system; The present invention also relates to a reactor pressure control device that suppresses large fluctuations in neutron flux due to pressure fluctuations.

[Technical background of the invention]

Figure 4 shows boiling water reactor (hereinafter referred to as BWR)
The diagram shows an outline of a power generation facility equipped with This fourth
To explain the power generation equipment based on the figure, a reactor pressure vessel 2 containing a reactor core 1 is connected to a turbine 5 through a main steam pipe 4 in which a main steam control valve 3 is interposed, and further connected to the turbine 5. Connected condenser 6
is connected to the reactor pressure vessel 2 by a water supply pipe 7. Further, the main steam pipe 4 is provided with a branched turbine bypass pipe 9 on the upstream side of the main steam control valve 3, in which a turbine bypass valve 8 is interposed. The other end of this bypass pipe 9 is connected to the condenser 6. On the other hand, a generator 10 is connected to the turbine 5.

In this power generation facility, the coolant (soft water) in the reactor pressure vessel 2 is heated as it passes through the reactor core 1 . The coolant becomes main steam, and this main steam is supplied to the turbine 5 through the main steam pipe 4.
Rotate the turbine 5. The rotation of the turbine 5 drives the generator 10. On the other hand, the main steam after driving the turbine 5 flows into the condenser 6, is cooled and liquefied, and is returned to the reactor pressure vessel 2 through the water supply pipe 7.

Note that the turbine bypass valve 8 installed in the turbine bypass pipe 9 has the following functions.

First, it has the functions of steam processing during startup, steam processing using decay heat during shutdown, and suppressing a pressure rise in the reactor pressure vessel 2 due to an abnormality within the reactor.

Second, it has a function to suppress pressure rise due to main steam cutoff during sudden load changes due to load cutoff, main generator turbine trip, etc.

Thirdly, it has a function of discharging surplus steam when suppressing frequency fluctuations due to load fluctuations in the power system.

By the way, a nuclear reactor control device is provided in a power generation plant to control the main steam control valve 3 and the turbine bypass valve 8.

To explain this reactor pressure control system based on its operation, a turbine speed signal 5a given from the turbine 5 is compared with a turbine speed set value 5b by a speed comparator (subtractor) 11, and both signals 5
The difference between a and 5b is output as a speed comparator output signal 11a. Speed comparator output signal 11 in this case
a indicates frequency change. Next, the speed comparator output signal 11a is converted by the load adjuster 12 into a change in load according to the load adjustment rate, and is output as a load adjuster output signal 12a. In this case, the load adjustment rate is normally set so that a 5% frequency change becomes a 100% load change. On the other hand, the load setting device 15
Load setter output signal given by (usually 100%)
15a is added to a load setting bias (usually 10%) 15b provided for normal pressure control by the pressure regulator 17 in the addition calculator 14, and outputted as a load setting signal 14a. Further, the load adjuster output signal 12a and the load setting signal 14a are added by the addition calculator 13 and outputted as a load setting deviation signal 13a. On the other hand, the pressure signal 2a and the set pressure signal 2b given from the reactor pressure vessel 2 are compared and calculated by the pressure regulator 17, and the result of this calculation is output as a pressure regulator output signal (usually 100%) 17a. In addition, the load setting deviation signal 13a and the pressure regulator output signal 1
7a are compared by the low value priority circuit 16, and the signal indicating the lower value is the low value priority circuit output signal 16.
It is output as a. The main steam control valve 3 is controlled by this low value priority circuit output signal 16a. Further, the low value priority circuit output signal 16a and the pressure regulator output signal 17a are compared in the differential pressure calculator 18, and this difference is outputted as a bypass valve control signal 18a, and this bypass valve control signal 18a causes the turbine bypass Valve 8 is controlled.

Next, to further explain the operation of this reactor pressure control device based on specific numerical values, in the normal operating state, the turbine speed signal 5a and the turbine speed set value 5b are equal, so the load adjuster output signal 1
Since the value of 2a is zero, the load setting deviation signal 13
The value output from the addition calculator 13 as a is the value of the load setting signal 14a, that is, 110%. and,
The load setting deviation signal 13a is output from the low value priority circuit 16.
value 110% and the value of pressure regulator output signal 17a
The smaller value of 100% is 100% for main steam control valve 3.
is output to. In addition, the pressure regulator output signal 17a
A difference of 0% between the low value priority circuit output signal 16a and the low value priority circuit output signal 16a is output to the turbine bypass valve 8 as the bypass valve control signal 18a.

On the other hand, when frequency fluctuation occurs, the speed comparator 11 outputs a speed comparator output signal 11a indicating the frequency deviation. This speed comparator output signal 11a is converted into a change in load according to the load adjustment rate, and is sent to the addition calculator 13 as a load adjuster output signal 12a. In this case, addition operator 1
The value of the load regulator output signal 12a input to 3 is
If it is greater than 10%, this addition operator 13 outputs
Load setting deviation signal 13a with a value less than 100%
is output to the low value priority circuit 16. The low value priority circuit 16 outputs a low value priority circuit output signal 16a having a value of less than 100% to the main steam control valve 3, and the main steam control valve 3 is throttled.
On the other hand, the difference between the pressure regulator output signal 17a and the low value priority circuit output signal 16a is output from the differential pressure calculator 18 to the turbine bypass valve 8, and the turbine bypass valve 8 is opened. As a result, surplus steam from the main steam control valve 3 is released into the turbine bus pass pipe 9.
It will be sent to the condenser 6 through.

[Problems with background technology]

However, when comparing the current response speeds of the main steam control valve 3 and the turbine bypass valve 8, the turbine bypass valve 8 is capable of faster response than the main steam control valve 3. This is due to differences in the mechanisms and control circuits between the main steam control valve 3 and the turbine bypass valve 8, but this difference in operating speed is due to the rate of increase/decrease in frequency due to the operation of the main steam control valve 3. This becomes even more noticeable when the critical rate of change is exceeded.

Such frequency fluctuations occur, for example, in the following cases.

That is, if a failure such as a short circuit or ground fault occurs in the power transmission system in the vicinity of a nuclear reactor power plant, an overcurrent will flow in the power transmission path. In this case, the generator 10 and the power transmission system are temporarily separated to protect the generator.
For this reason, the generator 10 is placed in a no-load state and is accelerated, and the frequency increases as shown in FIG. 5 a ₁ to _{a 2} .

Further, after that, a failure avoidance operation on the grid side is performed, and when the generator 10 and the power transmission grid are connected again, the load on the generator is returned to the original state. Therefore, following this change in load, the frequency also begins to return to its original value as shown at a ₂ to a ₃ in FIG.

However, in this case, the sudden connection to the power transmission system temporarily induces load fluctuations, and the frequency increases again as shown at a ₃ to a ₄ in FIG. 5. Thereafter, as the load fluctuation subsides, the frequency returns to a stable state as shown at a ₄ to a ₅ in FIG. 5.

To explain the operation of the reactor pressure control system during this time, when frequency fluctuations such as a ₁ to a ₅ in Fig. 5 occur, the main steam control valve 3 changes as shown in Fig. 5 a ₁ to a ₅ . On the other hand, a request with the polarity reversed is issued to the turbine bypass valve 8, and on the other hand, a request is issued to the turbine bypass valve 8 which has an inverse characteristic to the request to the main steam control valve 3, that is, a request similar to a ₁ to a ₅ in FIG.

In this case, since the turbine bypass valve 8 has a quick response, it performs an operation close to the request, that is, the operations b ₂ to b ₅ in FIG. 6 . On the other hand, the main steam control valve 3 has a slow response and cannot follow the demand if the frequency fluctuation range exceeds 1.5 Hz due to load fluctuation and the period becomes less than about 2 to 3 seconds. Therefore, the main steam control valve 3 performs the operations _c1 to _c3 in FIG. 6, ignoring the portions _a2 to _a4 in FIG. 5.

As a result, the pressure in the reactor increases to p ₁ ,
This increase in pressure gives a positive reactivity to the reactor, and the neutron flux increases, reaching φ ₁ . Therefore, if this φ ₁ exceeds the neutron high scram set point, the reactor will reach scram.

In Fig. 6, φ ₂ is the neutron flux after the scram, and b ₅ to b ₆ are the pressure increase in the reactor pressure vessel 2 due to the function of the turbine bypass valve 8 to discharge excess steam due to load fluctuations in the power system. This indicates that it has shifted to an inhibitory function.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to control the operating speed of the turbine bypass valve in accordance with the operating speed of the main steam control valve when a frequency disturbance occurs in the power system, thereby reducing the reactor pressure. It is an object of the present invention to provide a nuclear reactor pressure control device capable of suppressing pressure fluctuations within a vessel and suppressing large fluctuations in neutron flux.

[Summary of the invention]

The present invention provides a speed comparator that adds a turbine speed signal and a turbine speed setting value and outputs the result as a speed comparator output signal, and a load adjustment that converts the speed comparator output signal into a change in load according to a load adjustment rate. a load adjuster that outputs as a regulator output signal; an addition calculator that adds the load adjuster output signal and the load setting signal and outputs the result as a load setting deviation signal; and a pressure signal from the reactor pressure vessel. a pressure regulator that outputs a corresponding pressure regulator output signal; and a main circuit that compares the load setting deviation signal and the pressure regulator output signal and outputs a signal indicating the lower value as a low value priority circuit output signal. a low value priority circuit for controlling the steam control valve; a differential pressure calculator for adding the pressure regulator output signal and the low value priority circuit output signal and outputting the result as a turbine bypass valve control signal; If the rising/falling rate of change does not exceed the operating range of the main steam regulating valve, the turbine bypass valve signal is output to the turbine bypass valve, while the rising/falling rate of change of the turbine bypass valve signal a turbine bypass valve operation limiter that outputs a signal to the turbine bypass valve that limits the rising/falling rate of change of the turbine bypass valve signal so that it does not exceed the operating range of the main steam control valve; It is something that you have.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on embodiments shown in the drawings. Note that the same reference numerals are used for the same parts as in the conventional one, and the explanation thereof will be omitted.

FIG. 1 shows a power generation facility equipped with an embodiment of the reactor pressure control device according to the present invention, and the reactor pressure control device of this power generation facility includes a bypass valve operation restriction device 19.
have. The bypass valve operation limiting device 19 includes a load setting deviation signal 13a, a low value priority circuit output signal 16a, and a bypass valve control signal 1.
8a is input, and on the other hand, a turbine bypass valve operation limiting device output signal 19a is outputted from this bypass valve operation limiting device 19 toward the turbine bypass valve 8.

Next, the specific configuration of the bypass valve operation limiting device 19 will be explained. As shown in FIG.
and a change rate limiter 22.

Here, the signal discriminator 20 inputs the load setting deviation signal 13a, the low value priority circuit output signal 16a, and the load setting zero signal 16b, and outputs the signal discriminator output signal 20a to the turbine bypass valve control signal switch 21. is being done. The rate of change limiter 22 is configured to input the turbine bypass valve control signal 18a and output a rate of change limiter output signal 22a to the turbine bypass valve control signal switch 21. Further, the turbine bypass valve control signal switch 21 is connected to the turbine bypass valve control signal 18.
a, inputs the signal discriminator output signal 20a and the rate of change limiter output signal 22a, and inputs the turbine bypass valve control signal 18a and the rate of change limiter output signal 22
a is output as a turbine bypass valve operation limiting device output signal 19a.

Next, the configuration of the bypass valve operation limiting device 19 will be explained in more detail based on its function.

The load setting deviation signal 13a, the low value priority circuit output signal 16a, and the load setting zero signal 16b are compared in the signal discriminator 20, and the signal currently controlling the main steam control valve 3, that is, the low value priority circuit output signal 16a is determined. It is determined whether the signal is the pressure regulator output signal 17a used during normal operation or the load setting deviation signal 13a used when the load fluctuates. In this case, a "positive" signal is used as the load setting zero signal 16b when the load is normal, and a "negative" signal is used when a load shedding or turbine trip occurs. The discrimination result of this signal discriminator 20 is outputted to the turbine bypass valve control signal switch 21 as a signal discriminator output signal 20a.

Further, the turbine bypass valve control signal 18a is
A rate of change limiter 22 limits the rate of change of the rise and fall so that it does not exceed the operating limit rate of change of the main steam control valve 3. For example, rate of change limiter 2
The rate of change setting value in 2 varies depending on the main steam control valve 3 used in the plant and its control system, so the setting value for the opening and closing limit change rate of the main steam control valve 3 of the target plant increases and decreases. used as.

Further, the turbine bypass valve control signal 18a and the rate of change limiter output signal 22a are alternatively outputted to the turbine bypass valve 8 by the turbine bypass valve control signal switch 21 as the turbine bypass valve operation limiter output signal 19a. That is, when the discrimination result of the signal discriminator 20 is the pressure regulator output signal 17a, the turbine bypass valve control signal 18
a is turbine bypass valve operation limiting device output signal 1
It is output to the turbine bypass valve 8 as 9a.
On the other hand, as for the signal, the discrimination result of the discriminator 20 is the load setting deviation signal 13a, and the load setting zero signal 16b
is “positive”, the rate of change limiter output signal 22a is equal to the turbine bypass valve operation limit output signal 1
It is output to the turbine bypass valve 8 as 9a.
Further, when the load setting zero signal 16b is "negative", the turbine bypass valve control signal 18a is outputted to the turbine bypass valve 8 as the turbine bypass valve operation limiter output signal 19a to quickly open the turbine bypass valve 8. .

FIG. 3 shows the response characteristics of a power plant equipped with the reactor pressure control device of the example when the same frequency disturbance as shown in FIG. 5 is applied, and the operation of the main steam control valve 3 is It is similar to that shown in FIG. On the other hand, the operation of the turbine bypass valve 8 is different from that shown in FIG. 6 and is designed to approximately follow the response of the main steam control valve 3. As a result, good reactor pressure control is achieved.

In this way, in the range where the main steam control valve 3 is controlled by disturbances in the system frequency, the turbine bypass valve 8 follows the main steam control valve 3 and moves in an antisymmetric manner. It has a similar effect.

That is, according to the reactor pressure control system of the embodiment, as long as the frequency change rate does not exceed the operating limit rate of the main steam control valve 3, reactor pressure fluctuations can be suppressed as in the conventional case. On the other hand, in a range where the frequency change rate exceeds the operating limit rate of the main steam control valve 3, reactor pressure control with less pressure fluctuation is possible. Therefore, fluctuations in neutron flux are also reduced, so that the health and operability of the plant can be improved.

〔Effect of the invention〕

As explained above, the present invention includes a speed comparator that adds a turbine speed signal and a turbine speed setting value and outputs the result as a speed comparator output signal, and a speed comparator output signal that adjusts the speed comparator output signal to changes in load according to a load regulation rate. a load adjuster that converts the converted signal and outputs it as a load adjuster output signal; an addition calculator that adds the load adjuster output signal and the load setting signal and outputs the result as a load setting deviation signal; and a reactor pressure vessel. A pressure regulator outputs a pressure regulator output signal according to a pressure signal from the pressure regulator, and a low value priority circuit outputs a signal indicating whichever is the lower value by comparing the load setting deviation signal and the pressure regulator output signal. a low value priority circuit that outputs as a signal and controls the main steam control valve; a differential pressure calculator that adds the pressure regulator output signal and the low value priority circuit output signal and outputs the result as a turbine bypass valve control signal; If the rising/falling rate of change of the turbine bypass valve signal does not exceed the operating range of the main steam control valve, the turbine bypass valve signal is output to the turbine bypass valve, while the rising/falling rate of change of the turbine bypass valve signal a turbine that outputs to the turbine bypass valve a signal that limits the rate of change of rise and fall of the turbine bypass valve signal so that it does not exceed the operating range of the main steam control valve when Since the turbine bypass valve has a bypass valve operation limiter, the turbine bypass valve operates in accordance with the main steam control valve even when the system frequency fluctuation exceeds the operating limit speed of the main steam control valve. Therefore, stable reactor pressure control is possible without sudden pressure fluctuations in the reactor pressure vessel or large fluctuations in neutron flux.

Note that this device is particularly effective in plants having a full-capacity bypass system.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a power generation facility equipped with a reactor pressure control device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a bypass valve operation restriction device of the reactor pressure control device of FIG. Figure 3 is a graph showing the response characteristics of the power generation equipment in Figure 1 to the frequency disturbances in Figure 5;
Fig. 4 is a schematic configuration diagram of a conventional power generation equipment, Fig. 5 is a graph showing an example of frequency disturbance, and Fig. 6 is a graph showing the response characteristics of the power generation equipment shown in Fig. 4 to the frequency disturbance shown in Fig. 5. . DESCRIPTION OF SYMBOLS 1... Nuclear reactor, 2... Reactor pressure vessel, 5... Turbine, 11... Speed comparator, 12... Load adjuster, 13
...Additional calculator, 16...Low value priority circuit, 17...Pressure regulator, 18...Differential pressure calculator, 19...Bypass valve operation restriction device.

Claims (1)

[Claims] 1 A speed comparator that adds a turbine speed signal and a turbine speed setting value and outputs the result as a speed comparator output signal, and a load adjuster output that converts the speed comparator output signal into a change in load according to a load adjustment rate. a load adjuster that outputs as a signal; an addition calculator that adds the load adjuster output signal and the load setting signal and outputs the result as a load setting deviation signal; and a pressure according to the pressure signal from the reactor pressure vessel. A pressure regulator that outputs a regulator output signal, and a main steam control valve that compares the load setting deviation signal and the pressure regulator output signal and outputs a signal indicating the lower value as a low value priority circuit output signal. a differential pressure calculator that adds the pressure regulator output signal and the low value priority circuit output signal and outputs the result as a turbine bypass valve control signal; and a rise/fall of the turbine bypass valve signal. If the rate of change does not exceed the operating range of the main steam regulator, the turbine bypass valve signal is output to the turbine bypass valve, and on the other hand, the rate of increase or decrease of the turbine bypass valve signal does not exceed the operating range of the main steam regulator. and a turbine bypass valve operation limiter that outputs a signal to the turbine bypass valve that limits the rate of change of the rise/fall of the turbine bypass valve signal so that it does not exceed the operating range of the main steam control valve. Characteristic reactor pressure control device.