JPS6175295A - Boiling water nuclear power plant control system - 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 [Field of Application of the Invention] The present invention relates to a control system for a boiling water (BWR) nuclear power plant. This invention relates to a nuclear power plant control system that allows nuclear reactor operation to continue without causing a reactor scram.

[Background of the invention]

Figure 3 shows a schematic diagram of the BWR nuclear power plant.

The reactor output is controlled by changing the rotation speed of the recirculation I pump 38 to increase or decrease the core flow rate of the reactor 35. The rotation speed of the recirculation pump is controlled by a recirculation flow rate control system 37. Furthermore, multiple outputs are controlled by inserting and withdrawing control rods into and out of the nuclear reactor using the control rod drive system 36.

Steam generated in the nuclear reactor 35 passes through a main steam line 39,
The turbine 3 is adjusted by the steam control valve 31 of the turbine.
2, after performing mechanical work, it is condensed into water in the condenser 33 and is again supplied to the reactor (the water supply piping is not shown). Also, by opening the turbine pipe/master valve 30, steam is sent to the condenser 33 through the bypass line 34.
can lead to. Next, a turbine control system that controls the steam control valve 31 and the turbine bypass valve 30 will be explained.

The turbine control system can be roughly divided into a pressure adjustment function that controls the reactor pressure according to the signal of the turbine inlet pressure detected by the pressure detector P, and a pressure adjustment function that controls the reactor pressure according to the detected turbine speed signal and load setting value. The steam control valve 31 and the turbine bypass valve 30 are mainly controlled in coordination with each other.

During normal operation, the opening degree of the steam control valve 31 is controlled so as to keep the pressure detected by the pressure detector P constant. For example, when this steam pressure increases (decreases) by more than the set value, the regulator valve 31 is opened (closed) and the turbine output is increased (
(reduced) to keep the steam pressure constant. If the steam pressure rises further and the pressure rise cannot be suppressed even if the control valve 31 is opened, the pie-arm valve 30 is opened to suppress the rise in steam pressure. This is the pressure adjustment function.

On the other hand, when the rotational speed of the turbine generator exceeds a set value due to sudden load fluctuations, the opening degree of the steam control valve 31 is reduced in priority to the pressure adjustment function in order to prevent overspeeding of the turbine. This is the speed/load adjustment function.

FIG. 4 is a diagram illustrating the operation of a turbine control system in the prior art.

In FIG. 4, a deviation signal between a pressure signal 12 measured by a pressure detector P installed in the reactor or main steam piping and a preset pressure setting value 13 is transmitted via a filter circuit 14. is input to the pressure regulator 15, which in turn creates the total main steam flow signal 1.

On the other hand, a deviation signal between the turbine speed signal 16 measured by the turbine speed detector and the turbine speed set value 17 is input to the speed regulator 18 to create a turbine speed control signal 19. Furthermore, this speed control signal Load setting which is the output signal of the load setting device to 19: It is recommended to add the value 20 to the speed/load control signal 2. Create.

The main steam flow rate signal l obtained above and the turbine speed
The load control signal 2 is input to the low value priority circuit 3, and the low value side signals of both are input to the regulator valve 3 as the steam regulator flow rate request signal 4.
1 opening degree control is performed. Incidentally, since the BWR nuclear power plant has four steam control valves 31, the control valve flow rate request signal 4 is input to each of these valves. In addition, since the steam flow rate characteristic of the opening degree of the regulator valve 310 is not linear, a function generator 21 is installed for each valve, and this allows the regulator valve flow rate request signal 4 to be adjusted to adjust the turbine so that it almost matches the regulator valve flow rate. It is designed to be converted into a valve opening degree control signal 22 and provided to each control valve 31.

On the other hand, the pinos 4s valve 30 is the pinos 4s valve # obtained by subtracting the steam regulating valve flow rate request signal 4 and the pinos 9s valve chattering prevention bias signal 23 during normal operation from the total main steam flow rate signal 1. , the opening degree is controlled by the quantity request signal 24.

In general, in B■ nuclear power plants, DIT (
Is it possible to adjust the reactor output based on the amount of steam bubbles? When the id amount changes, the neutron flux responds sensitively to this change.

Therefore, during normal operation, the steam control valve 31 is preferentially controlled by the total main steam flow rate signal 1 based on the pressure signal 12.
The load setting value 20 is rated (
(100%) is set approximately 10% above the total main steam flow rate signal l when outputting the turbine.

Generally, the speed regulation rate is 5 for every 100% control signal.
speed change (2,5 Hz for rated frequency 50 Hz)
frequency change).

This increases the turbine speed within 0.5% (i.e. 0.2%) such that the speed request signal 19 is within 10%.
The regulating valve 31 does not respond to a frequency increase of 5 Hz or less, and preferentially performs pressure control.

On the other hand, a turbine speed increase of 0.5 inch or more that causes the speed/load control signal 2 to decrease by 10% or more (i.e. 0.25 inch or more)
When the frequency rises above Hz), the speed/load control signal 2 becomes less than the total main steam flow rate signal 1, and the regulating valve 31 is controlled by the speed/load 1filj # signal 2, and the valve's soft operation is performed. will be held.

At this time, the surplus air due to the throttling operation of the steam control valve 31 is obtained by subtracting the control valve εr1 from the total main steam flow rate signal 1 and the quantity request date number 4 and the bias value 23. Processing is performed by opening the piston valve 30 in response to the arm valve flow rate request signal 24. In this manner, during normal operation, the steam control valve 31 and the pinoyasu valve 30 operate in coordination, and the reactor pressure remains unchanged and the ground operation continues at a constant rate.

Next, as shown in Figure 5, in the power transmission system, the power load unbalance relay (power plant output) is connected to the receiving side.
A large disturbance occurs to the extent that the relay that operates when the turbine is unbalanced does not operate, and a relatively large increase in turbine speed occurs (a 3-channel speed increase, or a 1.5Hz frequency increase). The response of a nuclear power plant when the rotation speed reaches the rated settling state will be explained.

When an accident such as a lightning strike occurs in a power transmission system, the power transmission circuit breaker operates and the load suddenly decreases, causing the system frequency to rise. Thereafter, the fault is removed by the operation of the power transmission system protection circuit, and the frequency settles to the rated value. Correspondingly, the turbine rotational speed changes as shown in FIG. 5(a).

At this time, due to the rise in the turbine speed signal 16, the υ speed control signal 19 becomes a negative value, and the speed/load control signal 2 becomes lower than its normal value. When the turbine speed increases by about 0.25 Hz, the speed/load control signal 2 becomes less than the total main steam flow rate signal 1, and the output of the low value priority circuit 3 becomes the speed/load control signal 2. Therefore, the speed/load control signal 2 becomes less than the total main steam flow rate signal 1. As the control signal 2 decreases, the opening degree of the steam control valve 31 is reduced, reducing the turpentine output.

Accordingly, the value obtained by subtracting the regulating valve flow rate request signal 4 from the total main steam flow rate signal 1 becomes a positive value and exceeds the chattering prevention bias 23. Therefore, the pinos valve flow rate request signal 24
The bypass valve 30 is opened, and the reactor pressure is controlled by the bypass valve 30.

After that, in the process of restoring the diturbine rotational speed to the rated value by removing the fault on the power transmission system side, the steam control valve 31 opens as the speed/load control signal 2 rises, and the pinoise valve 30 closes accordingly. Otherwise, normal plant operation will be resumed.

By the way, the capacity of the bypass valve 30 is 1 of the rated main steam flow rate.
Consider a plant with less than 00%. Assume that in such a ground, the turbine speed fluctuates as shown in FIG. 5 (-) due to fluctuations in the system frequency. At this time, the opening degree of the steam control valve 31 is throttled, and the flow rate of the steam control valve 31 fluctuates as shown in FIG. 5(d). The flow rate of the binosu valve 30 is controlled as shown in FIG. 5(,).

At this time, the reduced flow rate of the steam control valve 31 is passed to the piston valve 30. However, if the capacity of the pinox valve 30 is smaller than the reduction in the flow rate of the regulator valve, the amount of steam guided to the turbine side through the regulator valve and the bypass valve is reduced. Therefore, the reactor pressure increases as shown in FIG. 5(b). Is the nuclear power plant inside the reactor core as mentioned above? The behavior of neutron flux is very sensitive to changes in reactor pressure. Therefore, the neutron flux fluctuates due to reactor pressure fluctuations as described above, and the As shown in the figure (,), the neutron flux scram setting value is reached and a reactor scram occurs. The above reactor scram is caused by the decrease in steam flowing through the steam control valve 31
Occurs when the capacity is exceeded.

Figure 6 shows the system frequency and turbine control valve opening control signal 2.
2, the straight lines 40 and 41 are
The relationship is shown at a load setting of 110% and 70 inches, respectively. Now, consider a plant where the capacity of the P/J valve 30 is 25% of the rated main steam flow rate. While the rated (100%) steam flow rate is being generated in the reactor, when the system frequency increases and reaches frequency F1 where the opening degree of the control valve 31 becomes 75 degrees, the 4-way valve 30 becomes 25 degrees. Chi steam is flowing. If the system frequency further increases, the amount of steam flowing through the control valve 31 will decrease, but the amount of steam flowing through the bypass valve 30 will not increase (because the pi-gas valve capacity is 25 inches).

Therefore, when the system frequency is 21 or more, the reactor pressure increases and a scram occurs.

In this way, the capacity of the bypass valve is 100% of the rated steam flow rate.
%, the occurrence of the above event and the system frequency at which it occurs will differ depending on the load setting value, but in any case, (generated steam There is a critical frequency Fc at which (regulating valve flow rate) is reached, and above this frequency, reactor scram occurs and there is a problem that the operation cannot be continued.

[Purpose of the invention]

The object of the present invention is to allow the plant to continue operating without causing a scram even if there is a disturbance in the power system to the extent that the nonowarload unbalance relay does not operate and the system frequency increases due to an increase in tarpan speed. The aim is to provide an m-atom couplant control system that makes it possible.

[Summary of the invention]

The present invention includes a turbine steam control valve that controls the flow rate of steam entering the turbine from the reactor, and a bypass valve that is controlled to allow a surplus of the main steam flow rate from the reactor that is blocked by the turbine steam control valve to flow. A control system for a boiling water nuclear power plant is characterized in that when the turbine load suddenly decreases, steam is generated in a turbine control valve.

According to the control method of the present invention, the power system load applied to the turbine suddenly decreases during a change and at a rate of change that does not activate the power load unbalance relay, the rotation speed of the turbine increases, and the generator frequency increases. In the event of a short-term frequency increase, limit the opening of the turbine steam control valve as described above to avoid a scram caused by a rise in reactor pressure, and also to prevent a long-term frequency increase. In contrast, by lifting the above restrictions and reducing the reactor output, it becomes possible to continue operation while avoiding a pscrum.

[Embodiments of the invention]

An embodiment of a nuclear reactor power control system according to the present invention will first be briefly described with reference to FIG. The following explanation and Figures 1 and 2
In the figure, parts indicated by the same reference numerals as those in FIG. 4 are the same as those described in FIG. 4.

In response to the turbine inlet pressure signal detected by the main steam pressure detector 43, the pressure regulator 15 produces a gold main steam flow rate signal 1, which is transmitted to the low value priority circuit 3. Also, signal 1
is generated by the steam regulator flow rate request correction function generator 6 and becomes the steam regulator flow rate limit signal 7. Signal 7 corresponds to the total main steam flow rate minus the bypass valve capacity. The high value priority circuit 8 compares the steam regulator flow rate request signal 4 and the steam regulator flow rate limit signal 7, and outputs the signal on the high value side to the regulator valve serge 42. Therefore, the flow rate of the steam regulator valve 31 is reduced. is limited to the capacity of the bypass valve 30 or less.

On the other hand, the comparator 10 compares the output signal 9 of the high value priority circuit with the input signal 4, and when the state where the input signal 4 is smaller than the output signal 9 continues for a certain period of time, the comparator 10 outputs a reactor output reduction signal 11.
is outputted and given to the recirculation flow rate control device 37 (or control rod drive mechanism 36) to reduce the reactor power. This is to determine that the amount of power generation is too large when the regulator valve 31 is controlled for a certain period of time or more by the steam regulator flow rate restriction signal 7, and to reduce the reactor output. Next, the control device of this embodiment will be explained in more detail with reference to FIG. 2, 1.

In the following description, the signal value of the signal n is generally expressed in numeric characters.

This control device includes a function generator 6 for correcting steam regulating valve flow rate demand.
have. The load setting value 20 (signal value 820) and the total main steam flow rate signal 1 (signal value S,') passed through the reactor power calculation filter 5 are input to the function generator 6. The reactor power calculation filter 5 has a function of smoothing fluctuations in the nationwide steam flow rate signal 1 due to fluctuations in the main steam flow rate during transient periods and outputting the smoothed fluctuations as a signal equivalent to the reactor power. The output signal value of the function generator 6 for steam regulating valve flow rate request correction is assumed to be S7. However, b is the capacity of the bypass valve 30.

The steam control valve flow rate signal 7 and the control valve flow rate request signal 4 obtained above are input to the high value priority circuit 8, and the high value side signals of both become the corrected steam control valve flow rate signal 9.

The comparator 10 outputs a reactor power reduction signal 11 when the state of S, < S continues for a certain period of time.

The control of the regulating valve 31 by this control device differs depending on the magnitude relationship of each signal value. This will be explained below.

(+) When S,'< S2o and S1≦S2, that is, when the load setting is larger than the total main steam flow rate and the total main steam flow rate signal is smaller than the speed/load control signal.

At this time, S, = Sl. On the other hand, s, = s, '-b
Therefore, Sl and S,' are almost equal and the difference is sufficiently small compared to bK, so the magnitude relationship between S4 and 87 is that S4 is 8
Becomes larger than 7. Therefore, the signal value S after the high value priority circuit becomes equal to S4.

Furthermore, since S4=S, the comparator 10 does not output the reactor power reduction signal 11. Therefore, the steam control valve 31 performs pressure control similarly to a conventional turbine control system.

(11) When 81'<S2o and S2<s, -b, that is, the load setting is higher than the total main steam flow rate, and the speed/load request signal is equal to the value obtained by subtracting the capacity of the bypass valve 30 from the total main steam flow rate. When I was little.

At this time, in the conventional turbine control system, as explained in the background section of the invention, the reactor pressure increases and a high neutron flux scram occurs. On the other hand, in this device, 54=s2. s
A=s1'-b, and S4<S7.

Therefore, S, becomes S, that is, s,'-b. The steam control valve 31 is controlled to flow steam equal to the total main steam flow rate minus the steam valve capacity. On the other hand, the pi-gas valve 30 is fully opened, allowing steam to flow by the capacity of the binox valve. Therefore, all of the generated steam is guided to the turbine side by the control valve and the bypass valve. Therefore, no increase in reactor pressure occurs, the increase in neutron flux is suppressed, and no scram occurs.

If this state continues for a certain period of time or more, the turbine rotation speed increases. To prevent this, the comparator 10 outputs a reactor power reduction request signal 11. As a result, the amount of steam flow is suppressed, the state shifts to S2≧51-b, and the regulating valve 31 controls the turbine rotation speed.

(111) S,'<S2o and 51-b≦S2<Sl
When S,=S4, the same control as the conventional one is performed.

(1v) When S2o≦81' 59=84, and the same control as the conventional one is performed.

Table 1 shows the results summarizing the above.

Table 1 (Notes) 1. The magnitude relationship represents the magnitude relationship between S4 and 87 using an inequality sign.

2, S, becomes a request to reduce the reactor power at °'1''.

FIG. 7 shows the behavior of a nuclear power plant with a pinox valve capacity of 25 inches in response to disturbances in the system frequency when this reactor power control system is applied. Although the regulator -yP31 is throttled in response to the fluctuations in the turbine speed shown in FIG. be guided. Therefore, the increase in reactor pressure is suppressed, the increase in neutron flux is also small, and no scram occurs.

〔Effect of the invention〕

According to the present invention, when an increase in the power system frequency occurs, there is no mismatch between the amount of steam generated in the reactor and the steam flow rate due to the steam control valve and the piston valve, and therefore the reactor pressure does not increase. Since scrams due to increased neutron flux do not occur, nuclear power plants can continue to operate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the B■ nuclear power plant control method according to the present invention, FIG. 2 is a partial detailed diagram of FIG. 1, FIG. 3 is a schematic diagram of a BWR nuclear power plant, and FIG.
The figure is a block diagram of a conventional example of a BWR nuclear power plant control system, and FIGS. 5(a) to 5(f) are diagrams shown. Explanation of symbols 1... Total main steam flow rate signal 2... Speed/load control signal 3... Low value priority circuit 4
...Steam control valve flow rate request signal 5...Reactor output calculation filter 6...Steam control valve flow rate request correction function generator 7...
Steam regulator flow rate limit signal 8...High value priority circuit 9...Corrected steam regulator flow rate request signal 10...
Comparator 11... Reactor power reduction request signal 12...
Pressure signal 13... Pressure setting value 14... Filter circuit 15... Pressure regulator 16... Turbine speed signal 17... Speed setting value 18... Speed regulator 1
9... Turbine speed control signal 20... Load setting value
21...Function generator 22...Turbine adjustment valve opening control signal 23...Bias signal for bypass valve chattering prevention 24...Pinos 4 valve flow rate request signal 30...Turbine bypass valve 31...・Turbine steam control valve 32...P-BIY33...Condenser 34...Turbine control valve line 35...Nuclear reactor 36...Control rod drive mechanism 37...Recirculation flow rate control Device 38...Reactor recirculation pump 39...Main steam line 40...System frequency - Turbine moderation valve opening control signal line (load setting 110%) 41...System frequency - Turbine moderation valve opening Control signal line (load setting 70%) 42... Control valve servo 43... Main steam pressure detector 44... Turbine speed detector Fig. 1 Fig. 5, 5 (Sec)\ko (5eC) 2 .36 figure, 50 1″T ′QI PC′)2
Peripheral liquid number (Hl) (Ni-1a> ] (b) 7th section, 5- (S6C)

Claims (1)

[Claims] Boiling water equipped with a turbine steam control valve that controls the flow rate of steam entering the turbine from the nuclear reactor, and a bypass valve that is controlled to allow a surplus of the main steam flow rate from the reactor blocked by the turbine steam control valve to flow. In a type nuclear power plant, when the turbine load suddenly decreases, the opening control signal of the turbine steam control valve is limited so that the decrease in the flow rate of steam flowing to the turbine steam control valve is equal to or less than the capacity of the bypass valve,
Furthermore, when the turbine load continues to decrease for a certain period of time or more, the restriction on the opening control signal of the turbine steam control valve is released and a signal is generated to reduce the reactor output. control method.