JPH0235398A - Output controlling device of nuclear power plant - Google Patents

Abstract

PURPOSE:To obtain an output controlling device with a quick respondence enough to keep a stable operation by suppressing an excess increment of neutron flux during an output change operation and by preventing a nuclear reactor scram therewith. CONSTITUTION:An adjusting valve for a turbine steam is controlled by an output signal of a pressure control system 22 adjusted by a deviation signal between a neutron signal and a standard signal. A load deviation signal is obtained by the deviation signal and accumulators 32e and 32f, and a pressure setting point is regulated by the load deviation signal, a regulating circuit 21 for the pressure setting point and accumulators 32b and 32c. Moreover, an MG set is controlled by the load deviation signal adjusted by a feed-forward circuit 27, and by a main controller 16, a velocity controller 17 and 18 and by a position regulator 20 for a scooping tube, and also a recirculation pump velocity is controlled to regulate a recirculation flow rate. An adjuster 30 is constituted with a filter 31, an accumulator 32a to obtain a deviation between the neutron signal and the standard value, a limiter 33 and a hysteresis filter 34.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an output control device in a boiling water nuclear power plant, and in particular to an output control device for a nuclear power plant that suppresses a transient increase in neutron flux. Regarding equipment.

(Prior Art) A conventional boiling water nuclear power plant control system will be explained with reference to FIG.

In the boiling water reactor 1, light water is used as a coolant and a moderator. When this cooling water passes through the fuel assembly of the reactor core 2, it absorbs the heat generated by nuclear fission of uranium in the fuel and becomes steam. Thus, the steam generated in the reactor 1 is transferred to a steam separator 4. It passes through a steam dryer 5 and is led from a pressure vessel 6 to a turbine 8 via a main steam pipe 7. The steam that has done work in the turbine 8 becomes condensed water in the condenser 9, and is transferred to the feed water heater 10. The water is returned to the reactor pressure vessel 6 via the feed water pump 11.

In general, control rods 3 are used to make large changes in output when starting or stopping a nuclear reactor, to adjust the output distribution, and to compensate for long-term changes in core reactivity due to fuel combustion. Perform this on the circulation flow rate control system.

The recirculation flow rate is driven by the recirculation pump 12;
The recirculation flow rate control system adjusts the recirculation flow rate by changing the power frequency of the induction motor that drives the recirculation pump 12 and changing the pump rotation speed. The recirculation flow rate control system includes a recirculation pump MG set 1 to 1 consisting of a variable frequency generator 13, a drive motor 14, and a fluid coupling 15 between them, and a main controller 16 to control it. Speed request limiter 17. It is composed of a speed controller 19 and a droplet tube position adjuster 20.

Further, the pressure control system 22 attempts to control the pressure of the nuclear reactor 1 at a constant level by operating a control valve 26 so that the amount of steam flowing to the turbine 8 matches the amount of steam generated in the reactor core.

A conventional nuclear power plant output control system uses a recirculation control system and a pressure control system 22 in coordination. When the load deviation is positive, an increase command is given to the recirculation flow rate controller to increase the reactor power by increasing the core flow rate. On the other hand, the pressure set point regulator 21 gives a command to the pressure control system 22 to open the turbine steam control valve, temporarily extracts the steam flow rate, and attempts to improve the initial response of the plan mill output. However, at this time, the feedforward circuit 27 is configured to compensate for the fact that the load deviation becomes small and the output control by the recirculation control system becomes slow. d3, code 2 in the diagram
3 is a control valve 4, 24 is a pressure sensor, 29 is a turbine steam stop valve, 28 is a turbine bypass valve, 29 is a main steam isolation valve, and 30 is a safety relief valve.

(Problem to be solved by the invention) By the way, when increasing the load set point and increasing the output from Plan 1, the following steps are taken: Increase in load set point → Increase in load deviation → Increase in main controller output signal → Increase in recirculation pump speed It is stabilized by the process of field→increase in core flow rate→decrease in core average void fraction→increase in reactivity→increase in neutron flux→increase in heat output horn→increase in core average void fraction→decrease in reactivity→decrease in neutron flux reach. When the rate of change in output is fast, there is a possibility that the neutron flux is temporarily accompanied by an overshoot. On the other hand, the main controller 16. which controls the plan l-output. Pressure set point regulator 21. The control constants of the feedforward circuit 27 are normally adjusted so as to maximize the output adjustment ability while ensuring plant stability. One of the important variables for this stability index is neutron flux.

Generally, when making the above adjustments, there is little margin for the reactor scram level due to the neutron flux peak value or neutron flux height.
There is a possibility that the neutron flux will rise excessively due to pressure fluctuations, core flow fluctuations, etc., leading to unnecessary reactor scrams. Therefore, in order to prevent unnecessary reactor scrams from occurring, the reactor scram level due to high neutron flux is adjusted to have a margin of 100%, but as a result, the load following function is lower than the original function. A problem arises in that the settings are set somewhere.

The present invention has been made in view of the above circumstances, and its purpose is to provide a highly responsive power control device that can prevent reactor scram and continue stable operation by suppressing an excessive increase in neutron flux during power change operation. It's about doing.

Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention provides an output control device for a boiling water type nuclear fuel burner 1, which is equipped with a recirculation control system and a pressure control system. A neutron flux reference value is set, and when this neutron flux reference value is exceeded, the deviation signal between this reference value and the neutron flux measurement value is obtained by passing it through a filter with hysteresis characteristics, and the signal obtained is used as a correction signal. It is characterized by being configured to suppress an excessive increase in neutron flux.

(Function) According to the power control device of Nuclear Power Buran 1 to 1 of the present invention, by setting a neutron flux reference value, when there is a margin in the reactor scram level, operation is performed by making maximum use of the ability of the power control device. . Further, by performing correction based on the deviation signal between the reference value and the measured neutron flux value, the intensity of the correction can be increased as the reactor scram level is approached. Furthermore, by having a filter with hysteresis characteristics, it is possible to maintain the stability of the control system even when the intensity of correction is increased.

(Example) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an embodiment of the present invention. Note that the same parts as in FIG. 5 will be described with the same reference numerals, but the description of the overlapping parts will be omitted.

In this embodiment, the returbine steam control valve is controlled using a signal obtained by correcting the output of the pressure control system 22 using a neutron flux signal and a reference value deviation signal. Also, this deviation signal and the adder 32e
, f to obtain a load deviation signal, and the pressure set point is adjusted by the load deviation signal, pressure set point adjustment circuit 21 and adder 321), and C. Roughly speaking, the signal obtained by correcting the load deviation signal by the foot-off word circuit 27 and the main controller 16
．． Speed controller 17. A speed controller 19 and a scoop tube position adjuster 20 are configured to control the MG sets 1 to 1 and control the recirculation pump speed to adjust the recirculation flow rate. An example of the corrector 30 for the pressure control system 22 includes a filter 31, an adder 32a for determining the deviation between the neutron flux signal and a reference value, a limiter 33, and a hysteresis filter 34.

The filter 31 is for cutting high frequency noise of the neutron flux signal, and may have a short time constant. The standard value of neutron flux is set below the reactor scram level with sufficient margin. That is, this reference value is a value that is above the rated value of the standardized neutron flux and below the reactor scram level.

The hysteresis filter 34 is a filter with a hysteresis characteristic, which generally has a parallelogram shape as shown in FIG. 2, and the output signal is the same in the rising direction and the falling direction of the input signal. It has the characteristic that it swells with a width that does not pass through the path. The hysteresis filter 3 is intended to compensate for the loss of stability and oscillation of the control system as a whole when the correction ability based on the neutron flux signal is increased, but it is not shown in Fig. 3. By making it a parallelogram, it is possible to achieve optimal characteristics.

Next, the operation of this embodiment will be explained.

In order to maintain the turbine inlet pressure constant, the pressure control system 22 adjusts the opening degree of the turbine steam control valve 26 so that an amount of steam commensurate with the output of the reactor 1 flows. Therefore, the output signal of the pressure control system 22 is
This value corresponds to the amount of steam that the turbine 8 obtains via the , that is, the actual load. Therefore, the output signal of the pressure control system 22 is combined with the actual load signal, added to the load setting point using the adder 32e, and further added with a bias using the adder 32f, and the signal is used as the load deviation signal. do.

Here, the response of Plan 1 to when a load deviation occurs will be explained using FIG. 4. Figure 4 is a characteristic diagram showing the response of the plant variables in Figure 1, where the horizontal axis is time in seconds, the vertical axis is the core flow rate, neutron flux, and main steam flow rate in %, and the reactor pressure is
Kg/cm'f'). According to this embodiment, the neutron flux does not reach the reactor scram level Jh as shown by the solid line (A) in FIG. In other words, load set point increases → load deviation occurs → main controller output increases → recirculation pump speed increases → core flow rate increases → core average void fraction decreases → reactivity increases → neutron flux increases → neutron flux The reference value is exceeded → the pressure control system output signal increases by the corrector 30 of the present invention → the turbine steam control valve opening degree increases and the load deviation signal decreases → the reactor pressure decreases d3 and the recirculation pump speed decrease command → the core average void ratio The increase in neutron flux is suppressed through the following process: increase in core flow rate and decrease in core flow overload rate → further increase in core average void rate → neutron flux decreases to below the reference value → zero output of corrector → settling.

However, conventionally, as shown by the broken line (b) in FIG. 4, the neutron flux may increase and reach 1 at the reactor scram level. Solid lines (c), (d), and (e) represent the core flow rate, main steam flow rate, and reactor pressure, respectively.

Next, the shape of the hysteresis filter 34 having a non-parallelogram shape, which is one of the features of the present invention, will be explained with reference to FIG. When the neutron flux rises above the reference value, the hysteresis filter power rises through path A in FIG. Hysteresis filter power increases further,
After exceeding the hysteresis width and reaching Po, it passes through path B and the bisteresis filter output increases as the hysteresis filter power increases. The hysteresis filter output serves as a correction signal to the output signal of the pressure control system 22, and acts in the direction of suppressing the increase in neutron flux as described above. Roughly the hysteresis filter power increases and reaches the turning point P.
1, the neutron flux suppression effect becomes excessive by taking path C and making the amount of increase in the hysteresis filter output relative to the upper back of the bisteresis filter input smaller than that of path B, and the neutron flux changes oscillally. to prevent

When the hysteresis filter output reaches the turning point P2 and begins to decrease, it follows a path and the hysteresis filter output also decreases. The slope of the route is gentle,
Therefore, the amount of decrease in the hysteresis filter output with respect to the decrease in the hysteresis filter input is small, and the neutron flux can be reduced while correcting the error in the neutron flux suppression effect.

Furthermore, as the hysteresis filter power decreases and crosses the bending point P3, the hysteresis filter output greatly decreases according to the path [. . By setting the slope of path B higher, the effect of suppressing the neutron flux is increased, and the slope of path B is set higher.

By appropriately selecting the slope of [, it is possible to prevent the suppressing effect from becoming too strong.

By using the hysteresis filter 34 having a non-parallelogram shape in this way, the amount of correction increases and the effect of suppressing the neutron flux becomes excessive, making the control system unstable as shown by the dashed line in Figure 4. This can prevent vibration from occurring.

[Effects of the Invention] According to the present invention, stable operation can be continued by preventing unnecessary reactor scrams while suppressing the excessive increase in neutron flux during power change operation during power change operation, and preventing system load fluctuations. As a result, it is possible to significantly increase the rate of availability for nuclear power plants.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the nuclear power plant output horn suppression device according to the present invention, FIG. 2 is a diagram showing a hysteresis filter having a parallelogram shape, and FIG. A diagram showing a hysteresis filter having parallelogram shape, FIG. 4 is a diagram showing responses of plan 1 to variables in FIG. 1,
FIG. 5 is a schematic diagram of a conventional boiling water nuclear power plant 1 to control system. 2...Reactor core 4...Steam water separator 6...Pressure vessel 8...Turbine 10...Feed water heater 12...Recirculation pump...Reactor. 3...Control rod. 5...Steam dryer. 7... Main steam pipe. 9... Condenser. 11...Water pump. 13... Variable frequency generator 14... Drive motor 15... Fluid coupling 16... Main controller 1Y... Speed demand limiter 19... Speed controller 20... Scoop pipe position adjustment Pressure set point regulator 22... Pressure control system 23... Control valve servo 24... Pressure sensor 25... Turbine steam stop valve 26... Turbine steam control valve 27... Feet forward circuit 28...Turbine bypass valve 29...Main steam isolation valve 30...Relief safety valve 31...Filters 32a-g...Adder 33...Limiter 34...Hysteresis filter (8733 ) Agent Patent Attorney Yoshiaki Inomata (Baka
1 person) 1/1 A iVl,,)I'>B ``→9Q 烱灼 1me ni Hane Pekoya ○

Claims (1)

[Claims] (1) In the output control device of a boiling water nuclear power plant equipped with a recirculation control system and a pressure control system, a neutron flux reference value is set, and if this neutron flux reference value is exceeded, this reference value and neutron flux An output control device for a nuclear power plant, characterized in that a signal obtained by passing a deviation signal from a measured value through a filter having a hysteresis characteristic is used as a correction signal, and the correction signal is configured to suppress a transient increase in neutron flux.