JPS63241498A - Nuclear-reactor feedwater controller - 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 [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor feed water control device disposed in a boiling water nuclear power plant.

(Prior Art) Generally, a boiling water nuclear power plant (hereinafter referred to as BWR) is configured as shown in FIG.

That is, the reactor core 1 is housed in a pressure vessel 2, and steam generated by heating in the reactor core 1 is collected in a gas phase part 2a,
It is sent to the turbine 4 through the main steam pipe 3. The steam generated by rotating the generator 5 via the turbine 4 is returned to water by the condenser 6, and the water in the condenser 6 is fed to the water supply pump 7.
The water is sent to the liquid phase part 2b of the pressure vessel 2 through the water supply pipe 8.

Further, a water supply control device 9 is disposed in the BWR in order to keep the water level in the pressure vessel 2 constant.

A conventional water supply control device 9 receives a reactor water level signal 10 and controls the speed of the water supply pump 7 using a water supply control signal 11 that compensates for changes in water level, thereby changing the water supply flow rate. Furthermore, since the water level changes based on the mismatch flow rate obtained by subtracting the feed water flow rate flowing into the pressure vessel 2 from the main steam flow rate flowing out of the pressure vessel 2, the main steam flow rate signal 12 and the feed water flow rate signal 13 are also input to determine the water level. Predicts changes and controls water supply.

In the above BWR plant, in order to prevent the turbine 4 from overspeeding when the load of the generator 5 occurs,
The steam control valve 14 is suddenly closed. At the same time, bypass valve 15
is opened to release excess steam directly to the condenser 6. Further, at this time, by inserting a control rod into the reactor core 1 or reducing the recirculation flow rate, the thermal output of the reactor is lowered and the amount of steam generated in the reactor is reduced.

In this way, the reactor is operated at low output, and after the power system is restored, the output is increased, and the generator 5 is reconnected to start power transmission.

The graph in FIG. 4, where the vertical axis is each reactor parameter and the horizontal axis is time, shows the reactor state when generator load shedding occurs in a BWR equipped with the conventional water supply control device 9.
Showing response.

As shown in this graph, a decrease in core inlet flow rate causes a decrease in reactor power, which causes a decrease in pressure and increases the steam volume below the water surface, causing the water level to rise. On the other hand, a reduction in power reduces the steam generation in the core and the water level falls. As the power decreases, the main steam flow rate decreases, and the water supply decreases accordingly, but before it stabilizes, the reactor water level undergoes significant changes due to the rapid changes in the core flow rate, pressure, and power output.

(Problems to be Solved by the Invention) As explained above, in a WR equipped with a conventional water supply control device, when a generator load cutoff occurs, the reactor water level fluctuates significantly.

However, if the water level rises significantly, the conditions for the steam sent to the turbine side will deteriorate, causing the reactor to undergo an emergency shutdown (
However, if the water level drops significantly, it will be scrammed to prevent core exposure.

Therefore, it is desirable to minimize fluctuations in the reactor water level, but with conventional water supply control equipment, it is difficult to control the water level in the event of sudden changes in flow rate, pressure, and output as described above. There was a problem.

The present invention has been made in response to such conventional circumstances,
The present invention aims to provide a water supply control device that can maintain a constant water level even during sudden changes such as when a generator load is cut off.

[Structure of the Invention] (Means for Solving Problems) The feed water control device of the present invention inputs a reactor water level signal, a main steam flow rate signal, and a feed water flow rate signal, and generates a feed water control signal according to these signals. In the reactor feed water control system, which controls the feed water pump to maintain the water level in the pressure vessel within a certain range, the reactor pressure signal, circulating flow rate signal, feed water temperature signal, and neutron flux signal are input to the reactor core. A change in the void ratio is calculated, a change in the amount of steam under the water surface is estimated from this change in the void ratio, a change in the water level in the pressure vessel is predicted, and a water supply control correction signal is generated in accordance with the water supply flow rate to compensate for this water level change. It is characterized by comprising means for outputting and correcting the water supply control signal.

(Function) In the feedwater control device of the present invention, the reactor pressure signal, circulation flow rate signal, feedwater temperature signal, and neutron flux signal are inputted to calculate the void ratio change in the reactor core, and from this void ratio change, the Means is provided for estimating a change in the amount of steam, predicting a change in water level in the pressure vessel, and correcting the water supply control signal by outputting a water supply control correction signal in accordance with a feed water flow rate that compensates for this water level change.

Therefore, even in a situation where the reactor core flow rate, pressure, and output fluctuate rapidly, such as when the generator load is cut off, fluctuations in the reactor water level can be minimized.

(Example) Hereinafter, the present invention will be described in detail with regard to an example shown in the drawings.

FIG. 1 shows a BWR in which a water supply control device according to an embodiment of the present invention is installed, and the same parts as in the BWR shown in FIG.

The feed water control device of this embodiment includes a reactor pressure signal 21, a circulation flow rate signal 22, a feed water temperature signal 23, and a neutron flux signal 24.
is input, estimates the change in the amount of steam below the water surface, converts this into a water level change, calculates the water supply flow rate to compensate for this water level change, and outputs the water supply control correction signal 25. Then, the reactor water level signal 10, main steam flow rate signal 12, and feed water flow rate signal 13 are input to predict the water level change, and the feed water control correction signal 25 is input to predict the water supply considering the water level change due to the change in the amount of steam below the water surface. control signal 27
and a control device 28 that outputs the water to the water supply pump 7.

Next, the operation of the water supply control device having the above configuration will be explained.

The subsurface steam amount change estimating device 26 first calculates the void fraction (steam volume fraction) change in the reactor core. It utilizes the fact that core thermal output Q is expressed by a nonlinear function f as α=f (P, W, h, Q). That is, in order to estimate each of these factors from measurable values, the reactor pressure signal 21, circulating flow rate signal 22, and feed water temperature signal 23 are used.
, using the neutron flux signal 24, the void fraction change α in the reactor core
is calculated using a formula similar to the above formula, and the change in the amount of steam below the water surface is estimated from this void fraction change and the reactor internal structure up to the core and water surface.

Once the change in the amount of steam under the water surface is determined in this way, it is easy to convert it into a change in water level, calculate the feed water flow rate to compensate for this change in water level, and output the feed water control correction signal 25 to the control device 28. do.

The control device 28 receives a reactor water level signal 10 and a main steam flow rate signal 1.
2 and the feed water flow rate signal 13 are inputted to calculate the feed water flow rate that compensates for water level changes due to mismatch flow rates between the conventional main steam flow rate and the feed water flow rate, and in addition to this, the feed water control correction signal from the subsurface steam amount change estimation device 26 is calculated. A new water supply control signal 27 in which 25 is added is output to the water supply pump 7 to control the flow rate of water supply flowing into the pressure vessel 2.

The graph in Figure 2, where the vertical axis is each reactor parameter and the horizontal axis is time, shows the BWR in which the water supply control device of this embodiment is installed.
The figure shows the response of the reactor state when generator load shedding occurs.

As is clear from this graph, in a BWR equipped with the water supply control system of this embodiment, even in situations where the reactor core flow rate, pressure, and neutron flux fluctuate rapidly and in a complex manner, the reactor water level fluctuations can be suppressed to a smaller extent than in the past.

[Effects of the Invention] As is clear from the above description, the water supply control device of the present invention is effective against sudden fluctuations in core flow rate, reactor pressure, and output, such as when generator load interruption occurs. Even though
Fluctuations in the reactor water level can be suppressed to a smaller extent than in the past, avoiding unnecessary reactor shutdowns, increasing the operating efficiency of the reactor, and contributing to the economic efficiency of power generation.

[Brief explanation of the drawing]

Figure 1 shows a BW equipped with a water supply control device according to an embodiment of the present invention.
A schematic system diagram of the R plant; Fig. 2 is a graph for explaining the state during load shedding in the BWR plant equipped with the water supply control device shown in Fig. 1; and Fig. 3 is a diagram of the BWR plant equipped with the conventional water supply control device. FIG. 4, a schematic system diagram of WR Plan I, is a graph for explaining the state at load shedding in a BWR plant equipped with the water supply control device shown in FIG. 3. 1......Core 2...Pressure vessel 7...Water pump 10...
...Reactor water level signal 12...Main steam flow rate signal 21...Reactor pressure signal 22.
...... Circulating flow rate signal 23 ...... Feed water temperature signal 24 ...... Neutron flux signal 25 ...... Water supply control correction Signal 26...
.....Subsurface steam amount change estimation device 27...
...Water supply control signal 28...Control device applicant Japan Atomic Energy Corporation applicant
Toshiba Corporation Agent Patent Attorney Su 111 - Figure 3 Figure 4

Claims (1)

[Claims] (1) Input the reactor water level signal, main steam flow rate signal, and feed water flow rate signal, and output the feed water control signal according to these signals to control the feed water pump to maintain the water level in the pressure vessel within a certain range. In the reactor feedwater control system, the reactor pressure signal, circulation flow rate signal, feedwater temperature signal, and neutron flux signal are input to calculate the void ratio change in the reactor core, and from this void ratio change, the change in the amount of steam below the water surface is calculated. Atom characterized by comprising means for correcting the water supply control signal by estimating and predicting a water level change in the pressure vessel, and outputting a water supply control correction signal according to a water supply flow rate that compensates for this water level change. Reactor water supply control device.