JPS6236199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor power adjustment device that automatically controls the generator output of a boiling water nuclear power plant according to a given output change pattern.

In order to ensure the integrity of the fuel cladding, boiling water nuclear power plants use an operating method (hereinafter referred to as preconditioning) that suppresses the rate of increase in reactor power when initially creating a specific core power distribution. driving) is taken. A reactor power adjustment device is a device that automatically controls generator output according to a predetermined output change pattern, but when used for preconditioning operation, it is necessary to Plant disturbances may cause the reactor power to rise above the allowable value.

An object of the present invention is to provide a nuclear reactor power adjustment device that can protect a nuclear reactor from plant disturbances that occur during preconditioning operation.

The present invention relates to a reactor power adjustment device that automatically controls the reactor output and generator output by adjusting the reactor recirculation flow rate. In order to prevent the reactor output from being automatically controlled beyond the allowable increase rate, two operating modes (normal mode and preconditioning mode) are provided. In the preconditioning mode, the output pattern is Actual plant data shows that the rate of change is approximately 0.5%/H or less, and the control accuracy under such an output pattern is 0.4% or less in terms of generator output deviation, and when controlling the output increase at 0.5%/H. , the control output operation of the reactor power regulator changes the recirculation pump speed request signal for 20 minutes or more.
The following operations are carried out by making full use of the characteristics such as the ability to change the temperature by 0.2% to 0.5% every 30 minutes.

(a) Automatically sets down the generator output deviation large emergency stop setting value from approximately 2% in steady mode to approximately 0.5%, and resets the upper limit control value of the increase command output of the recirculation pump speed request signal. It automatically sets down to a value close to the dead band of the circulation flow control system, and the synergistic effect of both allows operations to maintain the reactor output within the allowable rate of increase, while at the same time preventing non-sustainable disturbances. for,
This allows the automatic output control operation to continue effectively.

(b) If the manipulated variable calculation result shows a significant positive value two or more times in a specified sampling period (approximately 1 minute), the output control will be stopped in an emergency.

(c) Calculate the reactor power from the average power range neutron flux signal, and from the calculated reactor power for the past few minutes,
Calculate the reactor power change rate using the least squares method,
If this exceeds the specified value, the output control will be brought to an emergency stop.

The above monitoring method uses a neutron flux signal, but since this signal normally has fluctuations of about 1%, statistical processing as described above can be performed to prevent unnecessary control stoppages. It was designed so that it would not last.

FIG. 1 is a block diagram of the output control loop of a nuclear power plant to which the present invention is applied.

A boiling water reactor 1 includes a control rod drive mechanism 11 that inserts control rods into the reactor to adjust reactivity, and a recirculation pump 2 that forcibly circulates cooling water within the reactor core to improve power density. The cooling water introduced into the furnace is boiled, and the generated steam drives the generator turbine 10. The recirculation pump 2 is driven by a pump motor 3 and a generator 4. generator 4
is an M-G set motor and is started by a motor 6 via a fluid coupling 5, but the generator output is adjusted by the degree of coupling between the generator 4 and the motor 6, that is, the degree of coupling of the fluid coupling 5. . This fluid joint 5
is controlled by a recirculation flow controller 8 via a control unit 7. The recirculation pump 2, pump motor 3, generator 4, fluid coupling 5, motor 6, control unit 7, and recirculation flow rate control device 8 constitute a recirculation flow rate adjusting means. As a higher level control device of the recirculation flow rate control device 8, a reactor power adjustment device 9, which is a reactor power adjustment device according to the present invention, is provided. The reactor power adjustment device 9 calculates a recirculation pump speed request signal 15 based on the output pattern selection signal 12 (load request signal) and the output signal 13 of the generator 14 driven by the turbine 10, and outputs the recirculation pump speed request signal 15 to the recirculation flow rate control device 8.
Output to. The recirculation flow rate controller 8 receives the recirculation pump speed request signal 15 and the speed signal 17 of the recirculation pump 2 as feedback signals, and outputs a control signal to the control unit 7 of the fluid coupling 5. The rotation of the generator 4 for the recirculation pump is controlled by a fluid coupling 5, and the speed of the recirculation pump 3 is controlled by the generator 4. The core flow rate of the nuclear reactor 1 changes approximately in proportion to the recirculation flow rate, changing the reactor power. The steam generated in the nuclear reactor is sent to the turbine 10, which changes the turbine speed and the output of the generator 14.

FIG. 2 is a block diagram showing an embodiment of the present invention.

The reactor power adjustment device 9 is composed of an operation panel 91, an analog memory 92, and a signal converter 93, with a digital processing device 90 as its core. Further, the digital processing device 90 is, for example, a microcomputer, and is composed of an input signal processing section 901, a pattern creation storage section 902, a target generator output signal generation section 903, a control calculation section 904, an output pattern data section 905, and a monitoring section. It consists of a diagnostic section 906 and has the following functions. The pattern creation storage unit 902 stores a large amount of output pattern data, and when a specific pattern is selected with a pushbutton switch on the operation panel 91, the selected pattern data D _P is sent to the target generator output signal generation unit 9.
Output to 03. When activation is applied from the operation panel 91, the target generator output signal generation section 903
Using the panel pattern data, a time-function target generator output signal Sg is output to the control calculation unit 904. The control calculation unit 904 calculates the manipulated variable using the following equation from the target generator output signal Sg and the generator output S _F , which is a feedback signal, at one-minute intervals.

DM=GK・EMWG, EMWG=GMWGT−AMWG …(1) However, DM: Recirculation pump speed command manipulated variable [%] GK: Control constant EMWG: Generator output deviation GMWGT: Target generator output [MWe] AMWG: Time average generator output [MWe] The manipulated variable DM is converted into an increase/decrease number of pulses using the following formula in order to be output to the analog memory 92.

However, NPPO: Number of speed increase command pulses NNPO: Number of speed reduction command pulses DB: Manipulated variable dead band [%] CP: Pulse conversion constant [pieces/%] Pulse command data D calculated using the above formula _PC is the output signal processing The pulse increase command P
_I or pulse reduction command P _D and is input into the analog memory 92. Analog memory output S _AM changes in response to the input pulses and outputs a recirculation pump speed request signal 15 to recirculation flow controller 8 via signal converter 93 .

Note that the monitoring/diagnosis section 906 outputs an emergency stop signal as described later based on the output of the average neutron monitor.

FIG. 3 is a processing flowchart of the control calculation unit 904.

After calculating the generator output deviation using equation (1) above, check whether the operation mode is normal mode or preconditioning mode, and if it is in preconditioning mode, set the large deviation set value UEMW to preconditioning mode. Set down to the large deviation setting value (approximately 0.5% of the generator's rated output) in running mode, and monitor the deviation using the following formula.

｜EMWG｜≦UEMW……(3) If the above equation does not hold, a large deviation emergency shutdown instruction is issued, and from then on, the analog memory output is held and the reactor output is maintained.

If the generator output deviation is within the allowable value, the above
Equations (1) and (2) are used to calculate the manipulated variable and command pulse, respectively. Next, the operation mode is checked, and if the preconditioning mode is selected, the number of increased pulses is controlled to a value close to the dead band of the recirculation system (for example, about 0.3% based on the speed request signal).

In the above processing flow, in the preconditioning mode, the large deviation setting value for emergency stop due to large generator output deviation is automatically set down, and the calculated manipulated variable is controlled low to synergize the two. This effect prevents the reactor output from rising above the allowable value.

FIG. 4 is a principle diagram of the synergistic effect of the automatic setup of the manipulated variable upper limit value and the large deviation setting value for emergency stop with large generator output deviation according to the present invention. When a disturbance Pd in terms of reactor power is given, the control device output Pc in terms of reactor power increases in proportion to the disturbance Pd,
At the same time, the reactor output deviation Eg also increases, but the control device output Pc comes to show a constant value at the point where the large deviation set value is reached.

Next, check whether the current pulse output command is an increase command, and if it is an increase command, check whether an increase command was output last time, and if it is an increase command twice in a row, make an emergency stop. Issue a command and hold the analog memory output. In the present invention, the control operation of the recirculation pump speed during preconditioning operation is performed when the output increases (generator output, rate of increase of about 0.4%/H) and when constant output is controlled (at this time, the recirculation pump speed is (It is necessary to adjust the pump speed as the xenon concentration changes).The pump operates once every 20 to 30 minutes, so when outputting increased pulses twice in succession, Obviously, this is a case where a disturbance that reduces the generator output has occurred, and the abnormality is detected and the output control is stopped.

FIG. 5 is a flowchart of the monitoring and diagnosis section 906. In precondition mode, the rate of change in reactor output is monitored and an emergency shutdown occurs if the rate of change is large. This will be explained in detail below.

Reactor output needs to be precisely calculated using heat balance, but for this purpose, the feed water flow rate,
It requires a large number of input signals such as feed water temperature and reactor pressure, and a large number of input constants, which increases the amount of calculation and calculation time. Therefore, the average power range neutron flux signal (APRM) is used, but the sensitivity of the APRM signal deteriorates due to the neutron irradiation of the detector of the local power range monitor (LPRM), so the gain of the sensitivity correction is periodically changed. A calibration is performed and the signal being calibrated is not available. Further, the APRM signal usually has large fluctuations, and statistical processing is required to accurately capture the output change of about 0.4%/H, which is the output increase rate limit value during preconditioning operation. Therefore, in the present invention, the reactor output is calculated using the following equation.

However, CTP: Reactor power RTP(i): Core average heat flux level CAP(i): APRM(i): Calibration constant Note that RTP(i) is a digital filter that converts the APRM(i) signal into a digital filter with a time constant of 5 seconds. This is a ring-processed signal.

Next, the reactor power change rate is calculated using equation (5).

CRCTP ^k =3.0・(CTP ^k−3 CTP ^k )+CTP ^k
-2 CTP ^k-1 /10・θ……(5) However, CRCTP ^k : Reactor power change rate at current step k [%/min] CTPk: Reactor power at current step k [%] ] θ: Sampling period [minutes] Next, check whether the operation mode is normal mode or preconditioning mode, and if it is preconditioning mode, check whether the output change rate is within the specified value, and set the specified value. If it exceeds the limit, it is assumed that the output has increased abnormally due to disturbance, the output control is stopped urgently, and the analog memory output is held.

In the embodiment described above, when an attempt is made to output an increased pulse twice in succession, a significant disturbance is detected and an emergency stop is performed.
Furthermore, due to sampling period considerations, it is also possible to use a method that continues three times or an equivalent method.

As is clear from the above, according to the present invention, the preconditioning operation at the time of plant startup, etc.
When this is done automatically by the reactor power adjustment device, it is possible to suppress an increase in the reactor power beyond the allowable value due to plant disturbances that would lead to a decrease in the generator output.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the output control loop of a boiling water nuclear power plant including a reactor power adjustment device to which the present invention is applied, Figure 2 is a functional block diagram of an embodiment of the present invention, and Figure 3 is a control calculation. 904, FIG. 4 is an explanatory diagram showing the principle of the synergistic effect of the automatic set-down of the upper limit of the manipulated variable and the large deviation setting value of the generator output deviation emergency stop according to the present invention, and FIG. 9 is a flowchart of part 906. 1... Nuclear reactor, 2... Reactor recirculation pump, 3... Pump motor, 4... M-G set generator, 5... Fluid coupling, 6... M-G set motor, 7... Control unit, 8... Recirculation flow rate control Device, 9... Reactor power adjustment device, 10... Turbine, 14... Generator, 90... Digital processing device, 91... Operation panel, 92... Analog memory, 93... Signal converter,
901...Input signal processing section, 902...Pattern creation storage section, 903...Target generator output signal generation section, 9
04...Control calculation unit, 906...Monitoring diagnosis unit.

Claims (1)

[Scope of Claims] 1. A nuclear reactor that generates steam, a turbine that obtains rotational power from the steam from the nuclear reactor, a generator that generates electric power by being rotationally driven by the turbine, and a generator that generates electric power by being rotationally driven by the turbine. at least a recirculation flow rate adjustment means for recirculating the coolant and adjusting the recirculation flow rate thereof, the recirculation flow rate adjustment means adjusting the recirculation flow rate of the coolant according to an output change pattern of the generator. In a boiling water reactor power plant where the generator output is controlled, the generator output deviation is calculated based on the pattern signal and the generator output signal, and then it is determined whether the mode is normal mode or preconditioning mode. When in the dayning mode, the large deviation setting value for emergency stop due to large generator output deviation is automatically set down, and the large deviation setting value thus set down is compared with the generator output deviation determined above. If the deviation of the comparison result is large, the control operation is stopped and the manipulated variable is maintained, while the comparison result is calculated based on the generator output deviation when in the preconditioning mode when the comparison result is within the tolerance value. A nuclear reactor power regulating device characterized in that a control value of a manipulated variable is automatically set down, and the manipulated variable thus obtained is applied to the recirculation flow rate regulating means. 2. The reactor power adjustment device according to claim 1, wherein an emergency stop signal is generated when the calculation result of the manipulated variable shows a significant positive value two or more times in a row. 3. In the preconditioning mode, the rate of change is determined by the least squares method from the reactor output calculation result and the immediately preceding reactor output data, and an emergency stop signal is generated when the value is greater than a specified value. A nuclear reactor power adjustment device according to claim 1.