JP3357975B2 - Reactor power control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor power control device for automatically controlling a control rod when starting a nuclear power plant to control the power, and more particularly to an integration process for a control signal given to a control system. The present invention relates to a reactor power control device suitable for a control mode obtained by performing.

[0002]

2. Description of the Related Art The output of an improved boiling water nuclear power plant at the time of start-up is increased in the order of start-up → critical → attainment of rated pressure → incorporation of generator → attainment of rated output. Among them, the prior art will be described in the process of raising the temperature and increasing the pressure from the reactor criticality to the rated pressure. In the control in this process, the turbine bypass valve and the control valve are closed, the control rod inserted into the reactor core is pulled out in a state where steam does not flow out of the reactor, and the reactor is heated and pressurized.

[0003] There are the following two main operational restrictions during the temperature raising and pressurizing process. (i) The reactor cycle (time until the neutron flux becomes e = 2.71 times) is kept below a certain value so that the reactor protection function such as scram does not operate due to the rapid rise of the neutron flux when the control rod is pulled out.

(Ii) Limit the temperature change rate of the reactor water (for example, 55 ° C./h) so as not to give a thermal shock to each member constituting the reactor.
Keep below.

[0005] Since the latter condition (ii) is more severe, generally a temperature change rate equal to or lower than a limit value is set as a target value, and the control rod is operated so that the temperature change rate becomes the target value. . Here, the reactor water temperature does not necessarily mean the temperature of the coolant in the reactor core. In a general boiling water reactor, the temperature of the coolant measured in the pipe drawn from the reactor pressure vessel is called the reactor water temperature because the reactor water temperature in the reactor core is not directly measured. For this reason, there is a time delay between the temperature of the coolant in the core and the measured value of the reactor water temperature.

[0006] A conventional control rod operation procedure of the operator at the time of starting is shown below. First, the control rod is gradually withdrawn from the subcritical reactor to bring it into a supercritical state with a reactor cycle of about 100 to 200 seconds. The process up to this point is called the critical process, after which the temperature increasing process of increasing the reactor pressure to the rated pressure starts. At the beginning of the heating and pressurizing process, until the reactor water temperature starts to rise and negative reactivity is applied to the core,
Neutrons rise while maintaining the core cycle. The operator has a measure of the neutron flux level at which the temperature change rate of the reactor water is close to the target value from the past operation results. Insert it and pull out the control rod if it is likely to fall far short of the target.

When the reactor water temperature rises, the neutron flux stops rising and starts to decrease. After the time delay, the measured value of the rate of change in the reactor water temperature also changes from rising to decreasing. At this time,
If the measured value of the temperature change rate does not reach the target value, the control rod is pulled out again and the temperature change rate is waited. By repeating the above operation, once the measured temperature change rate reaches the target value, the measured temperature change rate is about 10 ° C / h from the target temperature change rate.
Wait for the temperature to drop, check that the furnace cycle is long enough, and pull out a small amount of control rod. This operation is repeated to maintain the temperature change rate of the reactor water at a constant value.

The above-described operation of the control rod by the operator requires skill in order to efficiently raise the temperature and pressure, and is time-consuming and burdensome due to the large number of operations. For this reason, some automatic operation methods have been conventionally proposed. The first
In the conventional method, while observing the measured value of the reactor water temperature change rate,
The proportional integral calculation is performed on the deviation from the target temperature change rate, and the control rod is operated based on the result. In addition, the second conventional method (described in Japanese Patent Publication No. 3-81693)
In the temperature increasing step, the control target value is calculated from the target temperature change rate and the current temperature change rate, and the timing of the control rod operation is determined.

[0009]

The reactivity of the control rod has a so-called non-linearity having a region with a large reactivity and a region with a small reactivity at the same amount of withdrawal. In addition, the neutron flux changes immediately due to the operation of the control rod, but until the change in the reactor water temperature change is measured, the heat transfer time from the fuel rod to the coolant in the core and the temperature measurement from the core The flow time to the point, the delay time of the measuring instrument such as the heat capacity of the thermocouple, and the delay time due to the time averaging operation for calculating the temperature change rate from the temperature occur, and this delay time is on the order of several minutes. . Therefore, when the control rod is operated based on the deviation between the target value and the measured value of the reactor water temperature change rate as in the first conventional method, the deviation in the region where the control rod reactivity in the integrator operation is small is small. It is difficult to keep the target reactor water temperature change rate due to the accumulation of water and the time delay of temperature detection.

In the second conventional method, since the control target value is constant, the reactor water temperature change rate cannot follow the target value in a region where the control rod reactivity is small, and the integrator for calculating the target neutron flux is used. Will accumulate deviation. As a result, when shifting to a region where the control rod reactivity is large, excessive reactivity is applied, and the rate of change in reactor water temperature may be 55 ° C./h or more.

An object of the present invention is to provide a reactor power control apparatus capable of causing a control parameter to properly follow a target value and suppressing overshoot of the target value even when the input reactivity has nonlinearity. To provide.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reactor power control apparatus, comprising: a logarithmic converter for logarithmic neutron flux levels taken from a neutron flux monitor connected to a neutron detector; A temperature change rate calculator for calculating the rate of change of the reactor water temperature taken from the detector, a least squares calculator for removing fluctuations in the rate of change of the reactor water temperature, and a specified time based on the past temperature change rate data. The advance compensation function for predicting the temperature change rate data of the previous reactor water temperature, the target reactor water temperature change rate setting device for inputting the target reactor water temperature change rate, and the setting of the target temperature change rate gradually. A rate-of-change limiter that increases the output of the rate-of-change limiter and the output of the advance compensation function unit, and a proportional integrator that converts the deviation into a neutron flux level that gives a target reactor water temperature change rate; Conversion from the proportional integrator The control rod operation is determined based on the deviation between the neutron flux target value obtained and the current neutron flux output from the logarithmic converter, and if the deviation is determined to be equal to or greater than a specified value, a control rod operation command is output. A control rod operation determination circuit, a comparison circuit that outputs a limit signal for limiting an integrator operation of the proportional integrator based on a deviation value between an output of the proportional integrator and an output of the logarithmic converter, and detects a reactor pressure. A comparator that determines that the deviation between the signal of the pressure gauge to be set and the output of the target reactor pressure setter that sets the target reactor pressure is equal to or less than a specified value and outputs a control rod stop command. so,
Achieved.

[0013]

[0014]

[0015]

[0016]

[0017]

By limiting the integral output, the target value of the control parameter can be controlled independently of the nonlinear characteristic of the control rod reactivity.
Burst can be suppressed and control following the control target value can be performed.

Also, during output control by the control rod operation, the control target value change characteristic of the proportional integration result and the control parameter are controlled.
If there is a time delay in the data change characteristic, hunting of the control rod operation (repeated insertion / removal) may be caused, or if the temperature measurement value fluctuates, the control rod operation may hunt if used directly for control. These problems can be avoided by providing a function of predicting the temperature change rate a specified time later from the past change characteristics (temperature change rate advance compensation function).

Further, at the beginning of the control, there is a difference between the control parameter and the control target value. If the control target value is set in a pulsed manner in this state, the control rod is excessively pulled out and the target value is turned off. Although a burst is obtained, this overshoot can be suppressed by limiting the rate of change.

Further, by making the proportional / integral gain variable, it is possible to perform control with good tracking of the target temperature change rate.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a reactor power control device according to one embodiment of the present invention. In FIG. 1, a reactor power control device 1 includes a logarithmic converter 14 for converting a neutron flux level taken from a neutron flux monitor 6 connected to a neutron detector 4 into a logarithm, and a temperature having a thermometer (thermocouple) 5. Temperature change rate calculator 10 for calculating the rate of change of the reactor water temperature taken from detector 7, least square calculator 11 for removing fluctuations in the rate of change of the reactor water temperature, and advance compensation function 12 for the reactor water temperature A target reactor water temperature change rate setter 8 for inputting a target reactor water temperature change rate; a change rate limiter 9 for gradually increasing the target temperature change rate setting; A proportional integrator 13 for calculating a neutron flux providing a change rate; and a control rod operation determining circuit 16 for determining a control rod operation based on a deviation between a neutron flux target value and a current neutron flux.
A comparison circuit (integration limiting means) 15 for outputting an integrator limiting signal from the deviation value, and a pressure gauge 22 for detecting the reactor pressure
And a comparator 20 for judging that the deviation between the target signal and the target reactor pressure setter 19 for setting the target reactor pressure is equal to or less than a specified value, and outputting a control stop command.

Next, the control operation of the reactor power control device in the temperature raising and boosting control after reaching the criticality will be described. First, after the core reaches criticality, the reactor power control device 1 of FIG. 1 starts automatically or by an operator's command. Containment container 21
The output signal of the neutron flux detector 4 installed in the reactor and the reactor water temperature signal output from the thermocouple 5 installed in the reactor piping are input to the neutron flux monitor 6 and the temperature detector 7, respectively. You. The detection signal of the neutron flux detector 4 is transmitted to the neutron flux monitor 6
And the detection signal of the reactor water temperature by the thermocouple 5 is converted to a temperature signal by the temperature detector 7.

At the start of the temperature increase control, first, the target reactor pressure setting unit 19 sets the target reactor pressure and the target reactor water temperature change rate setter 8 sets the target reactor water temperature change rate. Make settings.

The change rate of the target reactor water temperature gradually increases at a specified rate by the change rate limiter 9. The output of the reactor water temperature change rate calculator 10 fluctuates in the actual machine characteristics, and if this value is used for control as it is, there is a possibility that the control rod operation repeats withdrawal / insertion. In order to prevent this, the least-square operation is performed by the least-square arithmetic unit 11 for a certain specified time, and the average reactor water temperature change rate is obtained. Further, the thermocouple 5 has a detector time constant, and furthermore, the temperature of the core part further rises before the temperature inside the furnace rises due to the withdrawal of the control rod 2, and the reactor water whose temperature has risen becomes thermoelectric. Since it takes time to reach the position of pair 5 and to detect the temperature, the advance compensation function 12 predicts the reactor water temperature at a certain point in time.

The output of the change rate limiter 9 and the advance compensation function 1
If there is a deviation from the output of No. 2, the deviation amount is set to 0.
Control rod must be operated as follows. The calculation for determining the control rod operation amount will be described below. The deviation between the rate-of-change limiter 9 and the advance compensation function 12 is converted into a target neutron flux level by a proportional integration circuit 13. The reason for this is that the neutron flux level and the temperature change rate are approximately proportional. Therefore, the target neutron flux level calculated by the proportional integrator 13 is compared with the neutron flux level logarithmically converted from the output of the neutron flux monitor 6. Here, the reason that the output of the neutron flux monitor 6 is logarithmically converted by the logarithmic converter 14 is that the output of the neutron flux monitor 6 changes about 100 times in the temperature raising and boosting control process, so that a wide change can be easily controlled. This is to convert the value to a proper value.

A deviation between the output of the proportional integrator 13 and the output of the neutron flux logarithmic converter 14 is input to a control rod operation determination circuit 16. If the deviation is equal to or greater than a specified value, a control rod pull-out command ( Alternatively, an insertion command 18 is output. The pull-out / insertion command is input to the control rod operation system, and the control rod 2 is operated by driving the control rod drive motor 3 (not shown).

The output of the proportional integrator 13 and the neutron flux lo
The deviation from the g operation output is input to the comparison circuit 15. When the comparison circuit 15 detects a deviation equal to or greater than a specified value,
The integrator operation of the proportional integrator 13 is restricted.

Next, details and effects of the functions described above will be described. When the control rod installed in the center of the reactor core is pulled out, the input reactivity increases, the nuclear fission of the fuel in the reactor proceeds, and the reactor water temperature rises. On the other hand, when the reactor installed at the outer peripheral portion distant from the center of the reactor core is pulled out, the input reactivity is low, the nuclear fission of the fuel in the reactor does not proceed, and the rise in reactor water temperature is small. Pull out the control rod at the center of the core,
The order of withdrawing the control rods at the outer peripheral portion is determined by the control rod withdrawal sequence determined at the time of starting the reactor. In the state where the control rod at the outer periphery of the core having a small input reactivity is operated by the control, as shown in FIG. 2A, the actual temperature change rate (dashed line) follows the rise of the target temperature change rate (solid line). Phenomenon occurs.

If the deviation between the target temperature change rate and the actual reactor water temperature change rate is large and the deviation is continuously input to the proportional integration circuit 13 (FIG. 1), the calculation of the integral output continues to increase. At this time, even if the operation of the control rod in accordance with the control rod withdrawal sequence shifts to a location where the reactivity input is large in the central part of the core, the accumulated value of the integrator is obtained despite the control rod withdrawal. Because it does not decrease, the control rod is pulled out excessively, and the temperature change rate exceeds the target value.
May be lost. Therefore, in the present embodiment, in order to prevent this overshoot, when the deviation between the proportional integrator 13 and the logarithmic calculation output of the neutron flux level exceeds a specified value, the output of the integrator is limited. That is, FIG.
In (b), the integrator output gradually increases until time t2, and when the condition of integrator limitation (deviation ≧ specified value) of the comparison circuit 15 is satisfied at the time t2, the integrator output is set to a constant value. Enforce restrictions to keep. Then, the control region shifts to a region where the control rod reactivity is large, and at the time point t3 when the deviation between the target reactor water temperature change rate and the current temperature change rate becomes small, a normal integration operation is performed excluding this restriction.

The integrator restriction condition may be a deviation amount between the target reactor water temperature change rate and the current reactor water temperature change rate, in addition to the above conditions. As a method of limiting the integration of the integrator, instead of keeping the output of the integrator constant, the integration time may be increased when the integration limiting condition is satisfied, so that the rise of the output of the integrator may be reduced. .

The technique of limiting the integrator is not only a technique effective in the temperature raising / pressurizing process, but can also be similarly applied to start control by a control rod of another nuclear power plant (for example, a generator output control process). is there. That is, the target parameter
If the feedback parameter does not follow the motor, the overshoot of the target value can be reduced by determining that the control rod reactivity is in a small area and by limiting the integration.

Next, the function of limiting the temperature change rate will be described. The target temperature change rate is 10 ° C / h to 40
C / h. On the other hand, the temperature change rate at the start of the control is almost 0 ° C./h, and if the target temperature change rate is 40 ° C.
/ H, and when this value is used as a target value in the control, the difference between the target temperature change rate and the current temperature change rate is controlled.
Input to the proportional integrator as 40 ° C./h. As a result, the deviation due to the integrator is accumulated, which causes the control rod to be pulled out too much. Therefore, as shown in FIG. 3, a change rate limiter is provided to output a target temperature change rate at a specified time t with respect to a set target temperature change rate. As a result, the deviation between the target reactor water temperature change rate at the beginning of the control and the current reactor water temperature change rate is small, and the deviation does not accumulate in the integrator. FIG. 4 shows the control characteristics when the temperature change rate limitation is not provided, and FIG. 5 shows the characteristics when the temperature change rate limitation is provided. By providing a change rate limit, the overshoot of the reactor water temperature change rate can be reduced.

Next, the function of compensating for the rate of change of the reactor water temperature will be described. When the control rod is pulled out, the neutron flux rises accordingly. The reactor water temperature also rises according to the level of the neutron flux rise, but the rise of the reactor water temperature is delayed from the rise of the neutron flux. Causes of the delay include the delay time constant of the reactor water temperature detector and the transfer delay time until the reactor water at the center of the core reaches the reactor water temperature detector. It costs.

As shown in FIG. 1, in the temperature raising / pressurizing control, the control rod is operated with the deviation between the target neutron flux level finally obtained by the proportional integral calculation from the deviation of the temperature change rate and the current neutron flux level. I do. Therefore, if there is a difference between the temperature change rate characteristic and the neutron flux change characteristic, the temperature change rate cannot follow the target value. To prevent this, FIG.
As described above, a lead compensating function is provided for obtaining a quadratic curve from the past temperature change rate data and predicting the temperature change rate data a specified time later. By using the temperature change rate value predicted by the advance compensation function for the control, the neutron flux change characteristic and the temperature change characteristic match, and control following the target value becomes possible. FIG. 7 shows the control characteristics when the advance compensation is not provided, and FIG. 8 shows the control characteristics when the advance compensation is provided. With this advance compensation function, a large change in the temperature change rate can be suppressed.

Next, an embodiment in which the integration time of the integrator is made variable will be described. As in the description of the function of limiting the temperature change rate described above, when the target temperature change is set in a pulsed manner, the deviation from the current temperature change rate increases, the deviation is accumulated in the integrator, and the control rod It will be over-extracted. As one means for preventing this, the integration time is made variable according to the deviation amount between the target reactor water temperature change rate and the current temperature change rate. For example, when the deviation amount is large as shown in FIG. 9A, the integration time is shortened as shown in FIG. 9B, and when the deviation amount is small as shown in FIG. Also lengthen. If the deviation of the temperature change rate is large, shortening the integration time will increase the integrated value earlier, increase the control rod withdrawal amount, increase the reactor water temperature sharply, and increase the target reactor water temperature change rate and the current When the deviation of the temperature change rate becomes small, the integrator output gradually increases by increasing the integration time, and the control rod withdrawal amount decreases. As a result, the reactor water temperature change rate can quickly follow the target value. As a result, it is possible to reduce the target value overshoot of the reactor water temperature change rate. Although the integration time has been described as being variable, it is possible to cope with this by making the proportional gain variable according to the deviation amount.

When the deviation between the reactor pressure and the setting of the target reactor pressure setter 17 becomes equal to or less than the specified value in the comparator 20 by the above control, the temperature increase / pressure control is stopped.

[0038]

According to the present invention, even in the automatic control of the control rod having the non-linearity of the reactivity, it is possible to perform the control with good followability to the target change rate.

[Brief description of the drawings]

FIG. 1 is a functional configuration diagram of a reactor power control device according to one embodiment of the present invention.

FIG. 2A is a diagram illustrating a relationship between a control parameter value and a control target value, and FIG. 2B is a diagram illustrating a limitation of an integrator.

FIG. 3 is an explanatory diagram of functions of a change rate limiter.

FIG. 4 is a graph showing a change in reactor water temperature when a target temperature change rate restriction is not performed.

FIG. 5 is a graph showing a change in reactor water temperature when a target temperature change rate restriction is performed.

FIG. 6 is an explanatory diagram of a function of advance compensation.

FIG. 7 is a diagram showing a change in reactor water temperature when the advance compensation function is not provided.

FIG. 8 is a diagram showing a change in reactor water temperature when a function of advance compensation is provided.

9A is a graph showing the relationship between the target temperature change rate and the actual temperature change rate, and FIG. 9B is a graph showing the relationship between the magnitude of both the change rates and the integration time.

[Explanation of symbols]

1 ... Reactor power control device, 2 ... Control rod, 3 ... Drive mode
4, neutron flux detector, 5: thermocouple, 6: neutron flux monitor, 7: temperature detector, 8: target reactor water temperature change rate setting device, 9: change rate limiter, 10: temperature change rate Computing unit, 11: Least square computing unit, 12: Lead compensation function, 13: Proportional integrator, 14
... logarithmic converter, 15 ... comparison circuit, 16 ... control rod operation judgment circuit, 17 ... integration limit signal, 18 ... control rod withdrawal and insertion signal, 19 ... target reactor pressure setter, 20 ... comparator, 21 ... atom Reactor containment vessel, 22 ... Atomic pressure detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 7/00, 7/08

Claims (1)

(57) [Claims] 1. A logarithmic converter for converting a neutron flux level taken from a neutron flux monitor connected to a neutron detector to a logarithm, and a temperature for calculating a rate of change of reactor water temperature taken from a temperature detector having a thermometer. Rate-of-change calculator, least-squares calculator for removing fluctuations in the reactor water temperature change rate, advance compensation for predicting the temperature-change rate data of the reactor water temperature a specified time ahead based on past temperature change rate data a functional unit, and the target reactor water temperature change rate setter for entering the reactor water temperature change rate of the target, and the change rate limiter gradually increasing the setting of the target temperature change rate, the change rate limiter A proportional integrator for converting the deviation between the output and the output of the advance compensation function unit into a neutron flux level that gives a target reactor water temperature change rate; a neutron flux target value converted by the proportional integrator; From logarithmic converter The control rod operation is determined based on the deviation from the current neutron flux, and a control rod operation determination circuit that outputs a control rod operation command when the deviation is determined to be equal to or greater than a specified value, and an output of the proportional integrator. And a comparison circuit for outputting a limit signal for limiting the integrator operation of the proportional integrator based on a deviation value between the output of the logarithmic converter and a target for setting a signal of a pressure gauge for detecting a reactor pressure and a target reactor pressure. A reactor power control device comprising: a comparator that determines that a deviation from the output of the reactor pressure setter is equal to or less than a specified value and outputs a control rod stop command.