JPS642238B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a reactor water level control device in a boiling water nuclear power plant, and in particular to a nuclear reactor water level control system that enables automatic adjustment of the reactor water level during reactor startup, shutdown, and recovery operations during reactor scram. Related to water level control device. Conventional boiling water nuclear power plants have two purposes: to remove impurities during reactor operation and maintain appropriate water quality in the reactor water, and to collect surplus water generated during reactor startup, shutdown, and fuel exchange. A reactor coolant purification system is installed that has the function of discharging water outside the reactor system. During normal operation of the reactor, the water supply control system is in automatic operation mode, and the reactor water level is optimally adjusted. Figure 1 shows a conventional reactor water level adjustment system.
Condensate exiting the condenser 6 is pressurized by a low-pressure condensate pump 5, a high-pressure condensate pump 4, and a feed water pump 3, and then is injected into the reactor 1 via a feed water regulating valve 2.
During normal operation of the reactor, the feed water control device 12 is in automatic mode, and the reactor water level is automatically controlled by adjusting the feed water regulating valve 2. At this time,
Reactor water is always maintained at specified water quality by the reactor coolant purification system. That is, the circulation pump 7
The reactor water sent out from the reactor is cooled by the reactor coolant purification system heat exchanger 8. Furthermore, impurities are removed by the purification system over-desalination equipment 9,
The water is returned to the reactor via return piping and water supply piping. At this time, the drainage regulating valve 10 is fully closed manually,
The communication valve 13 to the condenser 6 is also fully closed. However, when a nuclear reactor is started or shut down, excess water is generated that raises the reactor water level due to water injection due to sheet leakage in the water supply system and cooling water from the control rod drive hydraulic system into the reactor. Furthermore, in the reactor start-up mode, the temperature and pressure of the reactor water increases due to control rod withdrawal when the water supply control valve is in the manual mode, and surplus water is generated due to expansion of the reactor water. In such cases, operators must perform manual remote control while monitoring the reactor water level gauge in order to treat excess water generated during operation and optimally control the reactor water level. . That is, when the reactor water level rises, the drain control valve 10 is manually opened to drain excess water to the main condenser 6 through the reactor coolant purification system. Additionally, during the same period, if steam consumption due to bypass valve opening exceeds the amount of water injected into the reactor, the reactor water level may drop. In this case as well, the operator controls the reactor water level by adjusting the drainage regulating valve 10. However, when the drop in the reactor water level cannot be suppressed even if the drainage control valve 10 is fully opened, the operator injects water into the reactor through the water supply system to control the reactor water level. Even if we do not consider emergencies such as recovery operations during reactor scrams, the above-mentioned operations during reactor startup and shutdown operations are quite frequent and require one full-time operator to manually control the reactor water level. Become. Furthermore, if these operations are incorrectly performed, the reactor may scram during normal startup operation, which will affect the operating rate of the nuclear power plant. The present invention has been made in view of the above circumstances, and its purpose is to provide the following:
An object of the present invention is to obtain a reactor water level control device capable of optimally and automatically controlling the reactor water level even when a water supply control system is in manual mode. The device of the present invention has a function of automatically controlling the opening degree of one or both of the water supply regulating valve and the drainage regulating valve to adjust the reactor water level when the reactor water level changes beyond a specified value. It is characterized by Hereinafter, the present invention will be explained in detail with reference to Examples.
Figure 2 is a diagram showing an embodiment of the present invention, and is used during reactor start-up operation, normal shutdown, and adjustment operation after reactor scram recovery, etc., when the feed water control system cannot be put into automatic operation mode. For reactor water level control, the reactor coolant purification system is used to maintain reactor water quality and to adjust surplus water, as in the past. In FIG. 2, the reactor water level control unit 16 is composed of an electronic computer 19 and an analog memory 18, and includes a reactor water level detector 11, a reactor pressure detector 14, a water pump discharge pressure detector 15, and a drainage flow rate detector. 24 plant signals are taken in, and the opening degrees of the water supply regulating valve 2 and the drainage regulating valve 10 are calculated.
Further, based on the calculation results, the opening degrees of the water supply regulating valve 2 and the drainage regulating valve 10 are controlled to maintain the reactor water level appropriately. At this time, connection valve 1 to condenser 6
Leave number 3 open. In addition, water supply adjustment valve 2
The mode changeover switch 17 is configured to allow switching between control by the reactor water level control section 16 and control by the conventional water supply control device 12. The computer 19 includes an input signal processing section 20 that performs rationality checking, averaging, filter processing, etc. of the inputted plant signals, and an input signal processing section 20 that performs a rationality check, averaging, filter processing, etc. on the inputted plant signals, and an input signal processing section 20 that calculates the opening degrees of the water supply regulating valve 2 and the drainage regulating valve 10 based on the processed signals. a control calculation unit 21 that performs control, a monitoring and diagnosis unit 22 that monitors abnormal operation of the control unit 16, monitors abnormal operation of the plant side, and requests the control unit 16 to stop reactor water level control when an abnormality is detected; It is composed of an output signal processing section 23 that controls the analog memory 18 based on the calculation result of the calculation section 21. In addition to inputting the above-mentioned plant signals, the computer 19 calculates the opening degrees of the two regulating valves using water level setting values as shown in Table 1.

【table】

[Table] Hereinafter, an example of how the computer 19 calculates the openings of the two regulating valves 2 and 10 will be explained in detail using the water level control conceptual diagram in FIG. 3 and the flowcharts in FIGS. 4A to 4C. do. However, in Figures 4A to 4C, the detected water level is lower than the target water level level Lo.
Only the case where Lx is large is shown, and the reverse case is omitted, but the flow is exactly the same. First, in Fig. 4A, the steps are shown so that they can be used immediately when the valve opening calculation described later becomes necessary.
Water level change rate (dL/dt) i at time i at 400
[mm/sec] is calculated by the linear regression method from the current and past three water level Lx values Li, Li _-1 , ..., Li _-3 [mm]; (dL/dt) i≒3Li + Li _-1 −Li ₋₂ −3Li ₋₃ /10Δt……(1) However, Δt [sec] is the sampling synchronization of the water level Lx. Next, in step 401, the water level deviation ε _L that determines the control mode is calculated by ε _L =Lx−Lo [mm] (2). Here, as at the first point in Figure 3, (L _L <)
If Lx< _LH , and assuming that the high water level correction operation flag FH is not on at this time, the judgment in steps 402 and 403 will lead to the step in FIG. 4B.
Move to 408. Furthermore, since the flag is not on here, the process jumps to step 413 in FIG. 4C, and for the same reason, jumps to the flow outlet, completing one control operation. i.e.
While L _L <Lx <L _H , the water level control device 16 does not control the valve opening. When the reactor water level Lx rises and becomes Lx> _LH as at time _t1 in FIG. 3, the process proceeds to step 404 based on the determination at step 403. Here, the control constant K ₁
Using ~K ₃ [mm ³ /Kg] and water level lowering target time T _S [sec], the displacement W _D1 required to restore the water level to Lo
[Kg/sec] and the displacement W _D2 [Kg/sec] required to maintain the water level at Lo. Find it by. When proceeding further to step 405, first step 404
Calculate the valve C _V value from the required displacement determined by the following formula; However, W _DO [Kg/sec] is the current displacement, P _R
[Kg/cm ²・g] is the reactor pressure, Pcvw [Kg/cm ²・
g] is the pressure applied by the reactor coolant purification system, and Kc is the control constant. Furthermore, since the relationship between the valve C _V value and the valve opening X _D [%] is known in advance in the form X _D = f (C _V ), the valve opening manipulated variable X _D1 [%] required to recover the water level Lo. %], _and the _valve opening operation amount X _D2 [%] required to maintain _the water level Lo is X _D1 = f ( _CV1 ) - X _D0 (5). However, X _D0 is the current valve opening. After this calculation is completed, in step 406, the drain control valve 1 is
Outputs a command to open 0 by X _D1 , and in step 407 turns on plug FH during high water level correction operation. This FH ON causes steps 408 to 409.
However, while the water level Lx is greater than _L0 , the flow ends at step 413 in FIG. 4C. In other words, the high water level correction operation continues. By this correction operation, the water level Lx will be adjusted to the time shown in Figure 3.
It decreases as after t ₁ and reaches L ₀ at time t ₂ ,
Proceeding from step 410 (Figure 4B) to step 411,
Here, a command is output to close the valve opening by X _D2 ,
This keeps the water level Lx at Lo and flags
FH is turned off (step 412). After this, no control is performed as in the case of t< _t1 . The operation when the water level drops at times _t3 , _t4, etc. in FIG. 3 is similar. Next, at time t ₅ in Figure 3, Lx = L _L ,
For this reason, even if the drainage control valve 10 is controlled to be fully closed (X _D = 0%), the water level will drop due to high steam consumption.
Assuming that Lx decreases and reaches the drainage uncontrollable low water level detection level _LLL at time _t6 , this is the low water level flow corresponding to step 415 in Figure 4C (omitted from the diagram, condition of Lx < _LLL ) At each step of the low water level flow detected in step 416, 417, and 418, the water supply regulating valve 2 is increased by the opening degree XFCV, and the low water level correction operation flag FL is turned off. This FL off steps 403~407, 409~
Steps 414 and 415 without the control corresponding to 412
This is to continue water supply by repeating the judgment corresponding to (Lx>L _L , Lx<L _LL ). Further, the single operation opening XFCV of the water supply adjustment valve 2 is selected to be 5% as the minimum opening that can be used continuously from the viewpoint of rangeability when the startup water supply adjustment valve is applied. As this water supply continues, the water level Lx rises beyond the target level Lo and reaches _LH at time _t7 . Then,
Step 403 in Figure 4A, which is the flow of high water level correction
detects this, and the opening degree control for opening the drainage regulating valve 10 is performed in steps 404-406. If the water level Lx decreases as a result of this, the above-mentioned control from time t ₁ to _{t 2} in FIG. 3 is started. However, even if the opening degree X _D of valve 10 reaches 100% (fully open), the water level
When Lx increases and reaches the drainage uncontrollable high water level detection level _LHH at time _t3 , this is detected at step 415 in FIG. (If it is not fully closed at one time, it will be fully closed by controlling several times), and the water level Lx decreases. At this time, the flag FH is off, so the water level continues to fall, reaching L _L at time _t9 , and from then on, the same control as after time _t3 is entered. As described above, in the present invention, even when the reactor water level cannot be controlled by controlling only the drainage regulating valve 10, it is possible to control the opening of the drainage regulating valve 10 again by controlling the water supply regulating valve 2. It is characterized by shifting to and controlling the area where . This is intended to avoid as much as possible the adverse effects on the reactor caused by the control of the water supply regulating valve by giving priority to the control of the drainage regulating valve. As is clear from the above description, according to the present invention, the reactor water level can be adjusted optimally and automatically even when the water supply control system is in manual mode, such as during reactor startup, shutdown, and recovery operation after scram. It is possible to control the nuclear power plant effectively, and improve the operation rate of nuclear power plants.

[Brief explanation of drawings]

Figure 1 shows a conventional reactor water level control system;
FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a conceptual diagram of water level control according to the present invention, and FIGS. 4A to 4C are flowcharts showing computer processing procedures when the water level rises. 1... Nuclear reactor, 2... Water supply regulating valve, 6... Condenser, 10... Drainage regulating valve, 11... Water level detector,
16...Water level control unit, 19...Electronic computer, 21
...Control calculation section.

Claims (1)

[Scope of Claims] 1. A drainage control valve provided in a reactor coolant purification facility of a boiling water nuclear power plant, a water supply control valve provided in a reactor water supply facility, a reactor water level detector, and the detector. a water level control section that takes in the detected water level and controls the drainage adjustment valve and the water supply adjustment valve, and sets the reactor water level to the target value; When the detected water level exceeds the set range, the valve control of the drainage regulating valve is performed to adjust the water level only by the drainage control, and a second condition indicating that the water level cannot be controlled only by the drainage control When the above detection water level exceeds the setting range,
The control of the drainage regulating valve is temporarily suspended, and the water supply regulating valve is controlled to move the reactor water level to the above-mentioned first setting range by water supply control. A nuclear reactor water level control device having a configuration in which, after moving to a first setting range, a drainage adjustment valve is controlled to adjust the water level by the drainage control.