JPS6334405A - Recirculating flow controller for feed pump - Google Patents

Abstract

(57) [Abstract] 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 water supply control system for a power generation plant, and is capable of ensuring stability of a steam generator water level.

) [Background of the Invention] Conventional recirculation flow rate control devices (for example, Japanese Patent Application Laid-Open No. 57-875
Figures 7, 8, and 9 for the publication (No. 03 Publication).

This will be explained using FIG. Figure 7 is a system diagram of the reactor feed water pump system. Water supplied from the condensate system passes through a condensate pipe 1, is pressurized by a turbine-driven water supply pump 6 and a motor-driven water supply pump 7, and is supplied to the reactor through a water supply pipe 12. To explain the system around the water supply pump, the outlet piping of the turbine-driven water supply pump 6 is connected to a condenser 13 at a branch. This is composed of a recirculation system piping 10 and a recirculation flow rate control valve 8, and this recirculation flow rate control valve 8 detects the specified pump flow rate by measuring the suction flow rate 2 of the turbine-driven water supply pump, and then activates the recirculation valve. It consists of a recirculation flow rate control device 4 that opens and closes. The recirculation system of the motor-driven water pump 7 corresponds to that of the turbine-driven water pump, and the recirculation system piping 11. Recirculation flow rate control valve 9, suction flow rate measurement 3. Recirculation flow control device 5
It is composed of In this water pump recirculation system, the minimum flow rate is always the minimum amount of cooling water for the pump so that the flow rate passing through the water pump gradually decreases and does not exceed a specified temperature.

FIG. 8 is a block diagram of a conventional recirculation flow rate control device. In this figure, the output of a flow rate transmitter 16 that measures the water pump suction flow rate is converted to a current-voltage converter 17. It is connected via a flow rate opening/closing calculator 18 to flow rate switches 19 and 20 that determine the opening/closing timing of the recirculation flow rate control valve 8, and an automatic/manual regulator 21. The signal setter 22.23 for setting the opening of the recirculation flow rate control valve 8 is operated by the flow rate switch 19.20 and outputs a setting signal, which is selected by the signal switch 24 and then connected to the rate of change limiter 26 and the signal switch. 27
added to. The rate of change limiter 26 is the recirculation flow rate control valve 8
The switching rate is determined by the signal setting device 25.

Continuous change or instantaneous change is selected by signal switch 27, then manual/automatic signal switch 29, voltage-current converter 31. Via the electro-pneumatic converter 32, the recirculation flow regulating valve 8 of the water pump is controlled. Analog memory 30 outputs control signals during manual operation.

Figure 10 shows the state of the valve opening with respect to the time when the flow rate control valve is opened and closed. When it opens and closes like this, d→c-4)) -46. Here, a → b is an instantaneous opening operation (or closing operation) to prevent valve wear at minute openings of the control valve, and b → C is defined by the rate of change α, and the control valve opens at a constant rate of change. The rate of change α for operation (closing operation) is determined by the rate of change limiter 26 and signal setter 25 in FIG.

FIG. 9 is a simulated diagram of fluctuations in the reactor water level when a control valve control method such as No. 10 is executed according to the prior art. 9th
In the figure, the plant load decreases and the recirculation flow control valve a-
+b-+c indicates that the recirculation flow control valve is open, and when the plant load increases, the recirculation flow rate control valve is closed as indicated by d-46-4f. In this case, the rate of change in the opening/closing operation of the control valve is α. In I100 MW class nuclear power plants, the capacity of the recirculation flow control valve is 25% of that of the reactor feed water pump, and its capacity is approximately 1000 T/H in the case of a turbine-driven feed water pump. When the large-capacity recirculation flow rate control valve a-4b → C opens, the reactor water level changes as shown in (a) → (b) → (c), and a low reactor water level alarm occurs. The recirculation flow control valve is d -) e
When the reactor is closed like -4f, the water level of the reactor is (d)→(
e) → (e), and a reactor water level high alarm is generated. In the I100MW class nuclear coupler plant, the reactor water level high (low) alarm is normal water level ±ioam, and the time from fully open to fully closed (or fully closed to fully open) of the control valve was initially set to 3 minutes. However, the reactor water level at point (b) or - (e) is about ±15~20c from the normal water level! l also decreased (or increased), and a reactor water level high (or reactor water level low) alarm occurred. At nuclear power plants, efforts must be made to minimize the occurrence of alarms, and various efforts have been made to eliminate the occurrence of the above-mentioned alarms. First, the time it takes for the recirculation control valve to fully open → fully close (or fully close → fully open) is increased from the initial 3 minutes to 4 minutes, 5 minutes, 5.5 minutes, 6 minutes, and 6.5 minutes. By testing each time in the actual plant and finally setting it to 7 minutes, we were able to complete the adjustment. This time setting was made by the rate of change limiter 26 and signal generator 25 shown in FIG. Also set these times! ! Needless to say, it took a lot of effort and time to reach a temperature of 111 degrees.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the conventional control methods described above, and to design a control method that is simple and rational (economical).

[Summary of the invention]

In the present invention, the opening (or closing) rate of the recirculation flow rate control valve was conventionally fixed, but in the present invention, the best initial setting opening (or closing) rate is determined based on the reactor water level change rate. The system calculates the most appropriate opening (or closing) rate, and if the reactor water level reaches a level with some margin for alarm, the control valve is opened until the reactor water level recovers. The opening operation (or closing operation) is attempted to be resumed after the opening operation (or closing operation) is resumed.

[Embodiments of the invention]

An embodiment of the present invention will be described below. FIG. 1 shows a control block having a control function according to the present invention.

A measurement signal of the reactor water level 51 that is constantly measured is input to the control calculation section 50. The control calculation section constitutes the main part of the present invention, and its control function is described in Section 2.
Figure, Figure 3, Figure 4, Figure 511! This will be explained by l. As the plant load decreases, the suction flow rate of the pump gradually decreases, and the opening of the recirculation valve is detected (FIG. 8, 19), and its signal (FIG. 1, 19) is input to the control calculation unit 50. In FIG. 2, if the start flow of the recirculation valve opening operation is detected (1), the reactor position at that time is detected. Then, set the reactor water level as the initial water level L1 (2) First, set the reactor water level low warning water level 1 βh = Lx (3). will decrease,
In the 1100 MW Frass nuclear power generation plan +, the reactor water level low alarm value is normally water level -101. Therefore, in order to prevent an alarm from occurring even if this adjustment operates and the water level drops, a margin of βl is taken into consideration.This β1 is approximately 3 to 5al for an I100MWJX child plant. Calculate the difference Lr-Lz=La (4) between L2 and L2, and use the initial setting Tz (
5). This T1 is determined to be the most appropriate value for the plant by conducting several tests during the plant trial operation adjustment period.

This Tl is a number of 3 to 8 minutes for I100MW class atomic couplets. 0th order water level similarity permissible change rate = az (6)
Calculate and set. This β1 becomes a value to be compared with the water level normalization rate which changes in the process of opening the recirculation flow rate control valve.

Once the calculations and settings up to this point have been performed, the recirculation flow rate control valve is permitted to start operating at the valve opening rate γl corresponding to β1 (7), and the valve starts operating. Next, as the control valve begins to open, a portion of the reactor supply water is removed from the recirculation system piping (Figure 7, 10.1).
1) and falls into the condenser (Fig. 7, 13), so the reactor water level begins to fall.

Therefore, the water level decrease rate calculation α'1 is performed from the current water level and the water level measured just before (8), and then it is determined whether the recirculation valve opening rate needs to be corrected (9), that is, (1 )
If the current rate of change in water level decrease α'l is smaller than the initially set permissible rate of change in water level decrease α1, the valve opening rate is set to be exactly the same as the current opening rate γ1. After all, Tl is
This is because it is a value determined from the most appropriate valve opening/closing time T1 at the time of test run adjustment of the plant. (2) Also, the current rate of change in water level decrease α′l is the initially set allowable rate of change α
If it is larger than l, the related rate is corrected to a new correlation rate γ11 that is gentler than γ'1. This γ”l is the previous rate γ′
Compared to 1, the time from fully open to fully open is approximately 10 seconds to 20 seconds.
The corrected T11 is appropriate since the time becomes longer in seconds. Then, steps 7, 8, and 9 in FIG. 2 are repeated to correct the recirculation valve opening rate. Next, as the recirculation valve reversed the above corrective action and opened, the reactor level dropped.

When the reactor level low warning water level reaches the specified water level βs = 'Lz (Fig. 1, 38, Fig. 3, 10), the recirculation valve is opened and held at that position. In this case, as a condition for maintaining the valve opening degree, the suction flow rate of the water supply pump must be equal to or higher than the water supply pump overheating prevention flow rate (FIG. 1, 40). The reason for this is that even if a low reactor water level alarm occurs, priority should be given to protecting the water pump. Therefore, if the feedwater pump overheat prevention flow rate is not secured, the control valve will continue to open even if a low reactor water level alarm occurs.

Next, after the reactor water level has recovered to Lx, the valve opening operation is started at the latest opening rate (Fig. 3, 11), and while adding correction operations again, the recirculation valve is continued until it is fully open. If so, the program control ends (FIG. 3, 12). Figure 4,
FIG. 5 shows the control operation when the recirculation valve closes, and is constructed based on the same concept as the recirculation opening operation. Returning to the explanation of FIG. 1, the control calculation section 5
The signal from 0 is connected to a signal switch 27 and a memory circuit 36. 27 is used to switch between a signal for operating the control valve at a predetermined opening/closing rate and a signal (36) for maintaining the valve opening at the previous valve opening when the reactor water level becomes abnormal. The conditions for this signal switching are as follows. In other words, when the reactor water level change rate becomes larger than a predetermined value (39
), or when the reactor water level reaches the specified water level during low warning water level L! (38), or when the reactor water level high warning water level - reaches the specified water level Ls (37), when any of these three conditions (41) is satisfied, and when the feed water pump overheating prevention flow rate or higher (40) is simultaneously established. (42) to self-hold this signal 43
), switch the signal switch 27 from b to C, and memory (36)
This signal is used to maintain the opening of the control valve at the valve opening just before the reactor water level abnormality (37°38.39) occurs. Then, all three conditions (37, 38° 39) are canceled (44), and a certain specified time (
45) At the time point (46), the signal changer (27) transmits the signal a-40, and the control valve starts operating again. The signal from the signal switch (27) is transferred to the manual-automatic switch (8th
29), a voltage-to-current converter (FIG. 8, 31), and a voltage-to-air converter (FIG. 8, 32) to control the recirculation flow control valve. This control device can be implemented by employing a microprocessor. FIG. 11 shows control valve opening control when the present invention is applied, and FIG. 6 shows a simulation of the reactor water level at that time. First, to explain the opening operation of the control valve with reference to Fig. 11, a1 → a2 During this time, in order to prevent corrosion of the valve at a minute opening (as in the prior art), it is opened on a step at the specified rate and ([% positive is not added. ax→a3
The opening operation is as follows. An abnormality occurred in the reactor water level at point a3 (the rate of water level decline became too large or the water level became too close to the low water level alarm value), so the valve opening was changed to aδ→
It is held until a4, and when the water level abnormality is removed, it operates again at the specified rate and with corrections, from a4 to a5, to fully open. For valve closing operation, b1 → b2 → b8 → b
It operates as follows: 4→b8→b8→b7.

In the case of this simulation diagram, an abnormality occurred in the reactor water level at two locations, b2→b8 and ba→b3, so the valve opening degree was maintained. To explain Fig. 6, the valve opening is a → l.
) −* c and the opening operation, while the water level is (a) → (b)
Since the water level has dropped to the specified level at the point where it starts to drop (b), the valve opening degree has to be kept constant (c - + d), and the water level has recovered (c)', so the valve resumes the opening operation from d to e. Indicates that it has started as follows. Similarly, in the valve closing operation, the water level moves from f to g, and the water level rises as shown in (e) to (ch). At point g), the valve opening degree is maintained from g to h. After the water level recovers from the abnormality, the valve moves again from h to h. i-
It operates as shown in + j, and the water level is stably controlled as shown in (to)' → (g). That is, if the control method according to the present invention is applied, the reactor water level will be (a) → (b) → (c)' → (d) →
(e) → (ch) → (e)' → (g) The lowering of the water level or the rise of the water level in the diagonally shaded area is suppressed, and stable water level control is possible.

〔Effect of the invention〕

According to the present invention, it is possible to achieve stable control of the reactor water level, and it is possible to avoid the generation of an alarm for reactor water level abnormality (alarm value 2 normal water level ±101), which is desired to be avoided in a nuclear power plant.

[Brief Description of the Drawings] Fig. 1 is a control block diagram of an embodiment according to the present invention;
Figures 3, 4, and 5 are control function diagrams of the present invention, Figure 6 is an explanation of recirculation valve operation when the present invention is applied, and a simulated diagram of fluctuations in reactor water level, and Figure 7 8 shows a system system diagram around the reactor feed water pump, FIG. 8 shows a recirculation flow rate control block diagram in the prior art, and FIG. 9 shows an explanatory diagram of the recirculation valve operation according to the conventional control system. 1... Recirculation valve opening operation start flow rate detection, 2... Initial water L1.3... Low alarm water level 1βl=L x, 4... Water level difference Lx-Lz=La, 5... Initial time setting T1.6
...Water level l -1'

Claims (1)

[Claims] 1. The condensate of the condenser is sent to the steam generator of the power generation plant by a water supply pump, and the outlet side of the pump is equipped with a pipe branched from the pump outlet in order to ensure the minimum flow rate of the pump. The system has a recirculation flow rate control valve that adjusts the pump minimum flow rate, a flow rate detection device that detects the pump suction flow rate, and a water level detection device that detects the steam generator water level, and the recirculation flow rate is adjusted according to the suction flow rate of the feed water pump. In a water supply system where a control valve opens and closes, the recirculation valve that starts its opening operation (or closing operation) at a predetermined recirculation valve opening change rate (or closing change rate) constantly generates steam at an intermediate valve position. Calculate and monitor the water level change rate of the steam generator, and if the steam generator water level change rate becomes larger than the specified water level change rate, a new recirculation valve opening rate of change (or closing rate of change) that is slower than the initial rate of change of the recirculation valve is set. A recirculation flow rate control device for a water supply pump characterized by correcting and controlling the circulation valve opening change rate (or closing change rate). 2. In claim 1, The recirculation valve opens (or closes) at
(1) When the water level reaches just before the steam generator water level high warning level (2) When the water level reaches the steam generator water level just before the low warning water level (3) Steam generator water level change rate becomes abnormally large, the above (1), (2), (3)
If any of the above occurs and the pump suction flow exceeds the feedwater pump overheating prevention flow, stop the opening (or closing) of the recirculation flow control valve and adjust the valve opening to that position. A recirculation flow rate control device for a water supply pump, characterized in that the recirculation flow rate control device for a water supply pump is opened (or closed) again when all of the conditions (1), (2), and (3) above are eliminated.