JPS61265402A - Feed water controller for nuclear power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a water supply control device for a nuclear power plant.

[Technical background of the invention]

Figure 3 shows the schematic configuration of a conventional water supply control device.
This water supply control device controls the water supply flow ff1 to the reactor pressure vessel 1.
2 to properly control the cooling water level 3 in the reactor pressure vessel 1.
is kept constant and stable. That is, this water supply control device controls the water supply flow rate 2. The cooling water level 3 and the main steam flow rate 4 are measured by a feed water flow detector 5. Water level detector6.
Detected by the main steam flow rate detector 7, these are detected by the main control calculation unit 8
The discharge flow rates of the motor-driven water supply pump 17 and the turbine-driven water supply pump 18 are calculated using the water supply control valve 12.13 and the steam control valve 15, which are operating ends.
By doing so, the cooling water level 3 within the reactor pressure vessel 1 is kept constant.

Specifically, the cold water level 3 detected by the water level detector 6 is compared with a set value, and the deviation between the feed water flow rate 2 and the main steam flow 14 is added and input to the main control calculation unit 8. Ru. This main control calculation unit 8 executes proportional and integral calculations for the above inputs, and sends the results to the water supply gap valves 12, 13# and the steam control valve 15 via switchers io and '+i, respectively. supplying. These water supply control valves 12, 13 and steam control valve 15 are connected to the motor-driven water supply pump (hereinafter referred to as M/D).
It controls the discharge flow rate of each of the water supply pump (hereinafter referred to as the water supply pump) 17 and the turbine-driven water supply pump (hereinafter referred to as the T/D water supply pump) 18, and the valve opening degree is adjusted by a signal from the main control calculation unit 8. It has become so. In addition, in the figure, 14 indicates a governor, and 16 indicates a pump driving turbine.

The M/D water pump 17 and the T/D water pump 18
The condensate discharged from the high-pressure condensate pump 21 is sucked through the water supply suction header 20, and this is transferred to the water supply discharge header 19.
It supplies water to the reactor pressure vessel 1 via the water supply discharge header 19, and is connected in parallel to the water supply discharge header 19. In addition, these water supply pumps 17 and 18 are appropriately selected depending on the operating state (load) of the plant, and between each of the water supply pumps 17 and 18 and the water supply discharge header 19, there is a discharge pipe from the water supply pump. A water pump recirculation system 23,24 is connected which returns the cooled water to a condenser (not shown). These recirculation systems 23 and 24 are used to suppress the power loss of the pump when the water pump is operating at a small flow rate to heat, which increases the temperature of the water supply below a specified temperature. 24 is a recirculation flow rate adjustment valve 25
゜26 is provided. These recirculation flow regulating valves 2
5.26 is a suction flow rate detector 27 installed at each suction part of the M10 water supply pump 17 and the T10 water supply pump 18.
The signal from 28 is configured to cause the valve opening to control the recirculation flow rate to the control condenser. Note that a low-pressure condensate pump 22 is connected in series downstream of the high-pressure condensate pump 21. Further, the water supply control valve 12 is used only at the time of starting up the plant, and after that, it is in the full state.

Therefore, water supply control of the M/D water supply pump 17 during operation is performed by the water supply 111ffi valve 13.

Further, the water supply control valve 12.13 and the steam control valve 15 can be manually operated by connecting the switching device 10.11 to the manual operating device 9 side.

[Problems with background technology]

By the way, the reason why the M/D water pump 17 and the T/D water pump 18 are installed in parallel is to provide a backup of the same capacity in case one of the water pumps trips. This is also a feature of power generation plants. Generally, two 25% capacity M/D water pumps 17 and two 50% capacity T/D water pumps 18 are installed, depending on the operating status (load) of the plant, as shown in Table 1. When the plant output is 20%, the water supply pump is switched from electric motor drive to turbine drive, and when the plant output is 40%, the T/D water pump 18 is switched from operating one unit to two.
Switching to standby operation, water is being supplied to the reactor pressure vessel 1.

However, when switching the water supply pump from electric motor drive to turbine drive, or from operating one T/D water pump 18 to operating two T/D water pumps, water supply control and recirculation control may interfere with each other. As a result, the suction flow rate of the feedwater pump fluctuates, making it difficult to keep the cooling water level 3 in the reactor pressure vessel 1 constant and stable.

Hereinafter, as an example, a case will be described in which the water supply pump is switched from electric motor drive to turbine drive.

While the M/D feedwater pump 17 is in operation, the cooling water level 3 in the reactor pressure vessel 1 is controlled by the feedwater control valve 13. When switching the water supply pump from electric motor drive to turbine drive from this state, the T/D water pump 18 is first started to increase the rotation speed, and then the rotation speed is kept constant. Next T/D
The rotation speed of the water supply pump 18 is gradually increased by the manual operation device 9, the discharge pressure of the T/D water supply pump 18 is brought close to the pressure of the water supply discharge header 19 (pressure equalization control), and the discharge pressure of the M/D water supply pump 18 is be equal to or higher than Thereafter, the rotation speed of the T/D water pump 18 is further increased manually, and the discharge flow rate of the T/D water pump 18 is gradually increased. At this time, the water supply control of the M/D water supply pump 17 is automatic, and the water supply control valve 13 is throttled by the amount that the flow rate has increased by the T/D water supply pump 18, and the M/D water supply pump 17 is automatically controlled.
Decrease the water supply flow rate from the D water supply pump 17. When this flow rate adjustment progresses further and the water supply flow rate from the T/D water supply pump 18 and the water supply flow rate from the M/D water supply pump 17 become equal, the switch 11 is moved from the manual operation device 9 side to the main control calculator 8 side. Switch to At the same time, the switch 10 is switched from the main control calculator 8 side to the manual operating device 9 side to give a lowering command. This lowering command is generally an integral action,
The main control calculation unit 8 gives an increase request to the T/D water supply pump 18, thereby proceeding until the switching is completed (shifting to rotation speed control). Then, when the water supply flow rate 2 to the reactor pressure vessel 1 is completely switched from the M/D water supply pump 17 to the T/D water supply pump 18, the drive motor (not shown) of the M/D water supply pump 17 is turned off. Stop.

When switching the water supply pump from electric motor drive to turbine drive in this way, the recirculation system 2 of each water supply pump 17 and 18
3.24 is automatically operated, and the recirculation system 24 of the T/D water pump 18 decreases the flow rate by the amount that the water supply flow rate increases, thereby keeping the suction flow rate of the T/D water pump 18 constant. . However, when the recirculation flow rate of the T/D water supply pump 18 decreases, since the high pressure condensate pump 21 and the low pressure condensate pump 22 are installed in series downstream of the water supply suction header 20, the condensate pump 21. Even if the discharge pressure of the T/D water pump 18 increases and the rotational speed of the T/D water pump 18 remains constant, the suction flow rate increases. Since this increase in the suction flow rate is larger than the decrease in the recirculation flow l, it is fed back again to the recirculation system 24 (positive feedback in this case), and the flow rate 111J of the T/D feed water pump 18 is 15 or the governor 14) operates in the divergent direction without waiting for the correction operation of the main control calculation unit 8. This acts as a disturbance on the water supply system, making it impossible to switch from the M/D water pump 17 to the T/D water pump 18.

This phenomenon will be explained in more detail with reference to FIG.
Reactor pressure vessel 1 during independent operation of M/D feed water pump 17
The water supply flow rate supplied to is QA, and the discharge pressure (water supply discharge header 19) at that time is P. From this state, the T/D water pump 18 is started, and pressure equalization is controlled.
When this is performed, water supply from the T/D water pump 18 is started at the intersection of the rotational speed r1 of the T/D water pump 18 and the throttling loss a of the recirculation flow rate adjustment valve 26 (water supply start point).

At this time, the high pressure condensate pump 21 and the low pressure condensate pump 22 are operated at the discharge pressure P1.

In this state, the M/D water supply pump 17 is switched to the T/D water supply pump 18, but when the water supply flow rate from the T/D water pump 18 occurs, the suction flow rate increases, so the recirculation flow rate adjustment valve 26 is restricted. It will be done. As a result, the recirculation flow rate of the T/D water pump 18 changes from Qa to Qo (the throttling loss increases and the resistance curve shifts from a to b).
The discharge pressure of the high-pressure and low-pressure condensate pumps 21 and 22 increases from Pl to P2 by the amount of change (ΔQ-) at this time.

Even though the rotation speed of the T/D water supply pump is constant (rr), the discharge pressure increases (r2) L/ , which results in an increase in the feedwater flow l to QD. At the same time, the suction flow rate also increases, so the recirculation flow valve 26 is further throttled and finally becomes fully closed.

By repeating the above, the water supply flow rate of the T/D water supply pump 18 increases to the switching point flow rate QA, so in order to switch the water supply pump, the high pressure and low pressure condensate pumps 21.2
The rotation speed of the T/D water supply pump 18 must be lowered by the amount that the discharge pressure of No. 2 has increased, and the water supply flow rate must be reduced. In this case, the recirculation flow rate of the T/D water supply pump 18 falls below the set value, and the recirculation flow rate adjustment valve 24 opens and eventually becomes fully open, causing interference between water supply control and recirculation control. We share each other. This occurs because the system loss between the T/D water supply pump 18 and the water supply discharge header 19 is very small, so the change in the water supply flow rate with respect to the change in the discharge pressure of the high-pressure and low-pressure condensate pumps 21 and 22 is large.

[Purpose of the invention]

The present invention has been made to solve the above problems, and its purpose is to provide a water supply control device that can prevent interference between water supply control and recirculation control when switching the water supply pump.

[Summary of the invention]

In order to achieve the above object, the present invention provides a water supply control device in which a turbine-driven water supply pump and a turbine-driven water supply pump are connected in parallel to the water supply discharge header, in which a first line is connected to the discharge line of the turbine-driven water supply pump.
At the same time, a second on-off valve is installed in the discharge line of the electric motor-driven water supply pump, and a third on-off valve is connected between the upstream side of the first on-off valve and the downstream side of the second on-off valve. It is characterized by being connected via.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing an embodiment of the water supply control device according to the present invention. In the figure, the same parts as in FIG. This embodiment differs from the conventional example in that a first on-off valve 31 is installed in the discharge line of the T/D water pump 18, and a second on-off valve 32 is installed in the discharge line of the M/D water pump 17. , and the upstream side of the first on-off valve 31 and the downstream side of the second on-off valve 32 are connected via the third on-off valve 33.

Next, the effect of the above configuration will be explained.

When the M/D pump 17 is operating independently, the first and third on-off valves 31 and 33 are fully opened, and the water supply control valve 13 controls the water supply. When switching the water supply pump from electric motor drive to turbine drive from this state, first
8 and increase the rotation speed, then keep the rotation speed constant. In addition, at this time, the recirculation flow rate adjustment valve 26 of the recirculation system 24
is fully open, and the T/D water supply pump 18 is performing recirculation operation. Next, in this state, the second on-off valve 32 is gradually closed, and the third on-off valve 33 is gradually opened.

As a result, the cooling water discharged from the T/D water supply pump 18 passes through the third on-off valve 33 and is supplied to the water supply discharge header 19 via the water supply control valve 12.

Then, the switch 10 is transferred from the main control calculation section 8 to the manual operation device 9.
After switching to and performing pressure equalization, turn the water supply pump to M/D.
The water supply pump 17 is switched to the T/D water supply pump 18.

At this time, the recirculation flow rate of the T/D water pump 18 changes from <Qa to Qc as shown in FIG.
The discharge pressure JJ changes from rl to r2, but water supply! li
T/D because throttle control is performed from 1 valve 12 IC
The water supply flow rate of the water supply pump 18 is Qo', but Qo'
= Q day, so the suction flow l does not increase. As a result, the flow feedback to the recirculation system 24 is appropriately controlled without divergence. After the switching from the M/D water pump 17 to the T/D water pump 18 is completed, the first on-off valve 31 is gradually opened and the T/D water pump 18
The cooling water level 3 in the reactor pressure vessel 1 is kept constant and stable by controlling the rotation speed of the reactor pressure vessel 1 by the main calculation control unit 8.

〔Effect of the invention〕

As described above, according to the present invention, the first on-off valve is installed in the discharge line of the turbine-driven water supply pump, and the second on-off valve is installed in the discharge line of the motor-driven water supply pump, and the first on-off valve is installed in the discharge line of the motor-driven water supply pump. By connecting the upstream side of the on-off valve and the downstream side of the second on-off valve via the third on-off valve, interference between water supply control and recirculation control can be prevented when switching the feed water pump, and the reactor The cooling water level inside the pressure vessel can always be kept constant and stable.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a configuration diagram showing the main parts of the water supply control device according to the present invention, and FIG.
The figure is a diagram showing the relationship between the water supply flow rate and discharge pressure, Figures 3 and 4 show conventional examples, Figure 3 is a schematic diagram of the water supply control device, and Figure 4 is a diagram showing the relationship between the water supply flow rate and discharge pressure. FIG. 1... Reactor pressure vessel, 5... Water supply flow rate detector. 6...Water level detector, 7...Main steam flow rate detector, 8.
・・Main control calculation unit, 12.13 ・・Water supply control valve, 15
...Steam control valve, 17...M/D water supply pump, 18
...T/D water supply pump, 19...water supply discharge header +
, 25.26... Recirculation valve, 31... First on-off valve. 32... Second on-off valve, 33... Third on-off valve. Applicant's agent Patent attorney Takehiko Suzue 1i12 Figure

Claims (1)

[Claims] In a water supply control device in which a motor-driven water supply pump and a turbine-driven water supply pump are connected in parallel to a water supply discharge header,
A first on-off valve is installed in the discharge line of the turbine-driven water supply pump, and a second on-off valve is installed on the discharge line of the motor-driven water supply pump, and a second on-off valve is installed on the upstream side of the first on-off valve and a second on-off valve. A water supply control device for a nuclear power plant, characterized in that the downstream side of the valve is connected to the downstream side of the valve via a third on-off valve.