JPS61246591A - Method of controlling flow rate of feed water - Google Patents

Abstract

PURPOSE:To enable to increase the operating rate of a nuclear reactor, by stabilizedly feeding low-rate feed water to it at the time when loading operation is made in a reactor plant itself after loading of a power plant is shut off, by stopping one of a plurality of feed water pumps at the time when the generator of a power plant shuts off loading. CONSTITUTION:The steam generated from a nuclear reactor 1 works in a turbine 2, and its exhaust gas is condensated in a condenser 4. The condensate from the condenser 4 is pressurized by a low pressure condensate pump 5, a high-pressure condensate pump 7, and a feed water pump (RFP) 9, returning to the nuclear reactor 1. The quantity of steam generated from the nuclear reactor 1 is suddenly and largely decreased when loading from a power generator is shut off. At this time a loading shut-off signal is output by a power load unbalance relay, for example, in a power generator 3 to actuate an RFP stopping device 15, which stops operation of an RFP 9a. But the other RFP 9b in operation is continuously operated although the number of revolution is decreased. By this method the flow rate lower than that by a full feed water system can be secured for the nuclear reactor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a condensate water absorption system of a power plant, and more particularly to a water supply control method for supplying stable water supply to a steam generator.

[Background of the invention]

The problems of the conventional condensate water supply system as disclosed in Japanese Patent Application Laid-Open No. 52-57403 will be explained using FIGS. 9 and 10 using a general power generation plant as an example. Conventionally, when a power plant shifts to isolated load operation after the generator load is cut off due to a problem with the system power supply, the required amount of water to be supplied to the reactor (or steam generator) is approximately 10% of the rated flow rate.
4, so it is necessary to rapidly reduce the discharge flow rate of the water supply pump. However, in general, water supply pumps control the water supply flow rate by controlling the rotational speed.When operating two pumps to ensure a low flow rate, as shown in Figure 1, the water supply pump (RF
'P) The rotation speed change 51 in two-unit operation is the low rotation speed limit value,
In other words, in order to go below the critical speed 52, the critical rotation speed is 5.
Maintained at 2 or higher. As a result, excessive water supply to the reactor 1 causes a rise in the water level of the reactor 1 and a plant scram. .

[Purpose of the invention]

An object of the present invention is to provide a water supply device with high reliability and excellent stability.

[Summary of the invention]

The principle of the present invention will be explained with reference to FIG. FIG. 11 shows the flow rate and head of the water supply pump that controls the rotation speed as y. When the rotation speed is decreased, the curve changes from 1ON to 5N, and the curve 52N is the critical rotation speed.

On the other hand, the necessary head (system head) curve determined from the pressure of reactor 1 and the pressure loss of the condensate water supply system is the water pump (
In the condensate bonpuni series operation at RFP) platform, the curve changes as shown by curve 538, and at the required water supply amount (for example, 56Q), the operating point is P, and RFP becomes 5N in rotation speed. Here, if the RFP two-car operation flow rate (below point 57Q) shifts to K, R
The FP rotation speed reaches the critical rotation speed of 52NK, so the flow point is 57.
It cannot be lowered below Q, and the total amount of water supplied will be twice the flow rate of 57Q.

On the other hand, the system head curve when R and FP are one unit is: ・R, FPXI, condensate Bondani series: Curve 558・RF
PXI, condensate pump 1 series: As shown by curve 548, the rotation speed increases at low flow rates.

Furthermore, by opening the recirculation valve 12 that branches off from the discharge of the water supply pump 10 and returns to the condenser 4, the flow rate of the RFP 10 itself increases, so the rotational speed of the RFP increases. A stable flow rate can be ensured even at low flow rates.

[Embodiments of the invention]

An embodiment of the present invention will be explained with reference to FIGS. 1 to 3. The difference from the conventional method is that an R and FP stop device 15 is provided to stop one water pump in response to a load cutoff signal from the generator 3 (for example, a power load unbalance relay).

The steam generated from the nuclear reactor 1 works in a turbine, and its exhaust gas becomes condensed water in a condenser 4. Condensate from the condenser 4 is pumped through a low pressure condensate pump 5, a high pressure condensate pump 7, and a water supply pump (hereinafter referred to as R).
FP) 9 and returns to the reactor 1.

Here, when a generator load cutoff occurs, the amount of steam generated from the reactor 1 rapidly decreases. Therefore, as shown in FIG. 2, it is necessary to rapidly reduce the amount of water supplied. Therefore, by using the interlock shown in FIG. 3 and stopping one of the RFPs 9a, the rotational speed of the RFP 9b during operation decreases as the water supply changes along the curve 58 shown in FIG. This makes it possible to secure a flow rate lower than that of other water supply systems.

A second embodiment of the present invention is shown in FIG. 5 and FIG. 1g6.

The difference from FIG. 1 is that a recirculation valve opening device is provided to open the recirculation valve 12 of the water supply pump 9 in response to a load cutoff signal.

In this embodiment, as shown in FIG. 6, the rotation speed curve 59 is higher than the rotation speed change curve 58 in FIG. 4, so that more stable water supply is possible.

A third embodiment of the present invention is shown in FIGS. 7 and 8.

The difference from FIG. 5 is that a pump system stop device 17 is provided that stops the water supply pump 9 and one series of condensate pumps 5 and 7 on the upstream side in response to a load cutoff signal. In this example, when the amount of water supplied is low, it is possible to operate at a higher rotation speed than in the above two embodiments, and low output operation is possible without dropping to a dangerous rotation speed.

In this way, the design methods for increasing the rotation speed of the water supply pump at low flow rates include: ■reducing the number of water supply pumps, ■opening the water pump recirculation valve, and ■reducing the number of upstream pumps. It is possible to take measures as necessary depending on the characteristics and limit value of critical rotation speed.

〔Effect of the invention〕

According to the present invention, it is possible to stably supply a small amount of water during single-load operation within the plant after the load of the power generation plant is cut off, and the operating rate is improved.

[Brief explanation of the drawing]

1st. Figures 4 to 4 are diagrams of one embodiment of the present invention; Figure 5;
'h, Figure-6 is the second embodiment of the present invention, Figure 7, Figure 8.
9 and 10 are illustrations of conventional problems, and FIG. 11 is an illustration of the principle of the present invention. 1... Nuclear reactor, 2... Turbine, 3... Generator,
4... Condenser, 5... Low pressure condensate pump, 7... High pressure condensate pump, 9... Water supply pump, 12... RFP
Recirculation valve, 14...Load cutoff detector, 15...R
, FP stop device.

Claims (1)

[Claims] 1. In a condensate water supply system consisting of two or more condensate pumps that send water from a condenser to a steam generator in a power plant, and two or more water supply pumps, piping, and valves. . A water supply flow rate control method, characterized in that the water supply pump is stopped when the generator load is interrupted. 2. The water supply flow rate control method according to claim 1, characterized in that two or more of the condensate pump and the water supply pump are stopped when the generator load is interrupted. 3. The water supply flow rate control method according to claim 1, characterized in that a portion of the water supply is returned to the condenser from the discharge side of the water supply pump when the generator load is interrupted.