JPS589097A - Feedwater control device of bwr type reactor - 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 The present invention relates to a water supply control system for a boiling water nuclear reactor. Figure 1 shows the overall configuration of a boiling water nuclear power plant and the schematic configuration of a water supply control system. Regarding the steam circulation system, the reactor pressure vessel 2 is housed within the reactor containment vessel 1, the reactor core 18 is housed within the reactor pressure vessel, and the steam generated in the reactor core 18 is Inside the pressure vessel 2, it passes through a steam separator 4 and a steam dryer 3 located above the core, and then exits the pressure vessel 2v to a main steam pipe 2], a control valve 11
The 0th order reaches the main turbine 13 via the main turbine 13
The steam led to the reactor is returned to the reactor from the feed water pump 1941C after passing through condensate @15, condensate pump n1, condensate demineralizer 16, and feed water heating @17. Driven by.

The feed water returned from the main turbine 13 and the water falling from the steam separator 4 are sent to the lower part of the core by the recirculation pump 10 and are again used to cool the core.

Note that the bypass valve 12 is opened in the event of an accident, startup, etc., bypassing the main turbine 13 and sending steam directly to the condenser 15.

The feed water control system includes a reactor water level detector 5 that detects the reactor water level, a feed water flow meter 6 that detects the reactor inlet feed water flow rate, a main steam flow meter 7 that detects the reactor outlet steam flow rate, and these detectors or flow rates. and a water supply control device 8 that controls the water supply to the reactor based on the detected value by the meter. The present invention relates to this water supply control device 8.

Next, FIG. 2 shows a schematic diagram of the configuration of a conventional water supply control device 8. As shown in FIG. As shown in FIG. 2, the feed water control device 8 includes a mismatch control section A that controls the balance between the feed water flow rate and the main steam flow rate, and a water level control section B that maintains the reactor water level constant.
It is roughly divided into a flow rate control section C that controls the water supply pump flow rate.

The mismatch control unit A uses the main steam flow rate signal S detected by the main steam flow meter 7 and the detected feed water flow rate signal 8 applied to the feed water flow meter 6 as input signals, and operates the addition calculator Σ1.
Find the difference between both signals s and e S*, and the difference V1
The first water supply flow rate request signal S, which is output as the water supply flow rate request compensation code a, is sent to the addition calculation circuit Σ.

The water level control unit B includes a main steam flow rate signal 81 and a water level setting device B,
A water level setting signal 8111 having a preset value is used as an input signal. This water level setting signal S4 is corrected by a correction signal 54VC so that the steam/water separation efficiency is optimized. In other words, the optimal steam-water separation efficiency depends on the main steam flow rate (therefore,
This function generator BIK receives the main steam flow rate signal S, and generates a predetermined correction signal S, depending on the input value. 0 is output, and the correction signal 84 and the water level setting signal 8
ts are added together in the addition calculation circuit J, and as a result, the corrected water level setting signal 8. The zero-then-one corrected water level setting signal S, which is obtained, is input to the addition calculation circuit Σ4, and the reactor water level signal S, from the reactor water level detector 5 is subtracted. The resulting water level deviation signal8. is outputted as a second water supply flow demand compensation signal S via a flow rate limiter B1 and a proportional-integral controller (hereinafter referred to as a PI controller) B4V. This second water supply flow rate demand compensation code S is input to an addition calculation circuit J.

The addition calculation circuit receives a second water supply flow rate request signal S and a first water supply flow rate request compensation signal S from the mismatch control section A.

, and outputs the total water supply flow rate request signal S.

This total water supply flow rate request signal S is input to the flow rate control unit CK.

In the flow rate control unit C, the water supply pump flow rate 81 detected by the water supply flow meter 6 (Fig. 1) is calculated from the total water supply flow rate request signal.
0 is subtracted in the addition operation circuit Σ. The difference signal is input as a flow deviation signal S to the flow restrictor B, and then via the PI controller B to the function generator B? The O function generator B input to the water supply pump driving turbine 9
O-function generator B is for compensating for the nonlinear characteristics of the adjustment valve addition.

outputs an opening request signal 80 for the adjustment valve.

Next, the control operation of the above control system will be explained.

As an example of a case where a water level rise occurs due to a drop in core pressure, a situation will be described in which this occurs due to a misreading of the turbine bypass valve 12 (FIG. 1) (see FIG. 3).

First, when the turbine bypass valve 12 makes a false alarm, the main steam flow rate increases. This is because, in addition to the amount supplied to the main turbine 13, the amount is increased by the amount sent directly to the condensate 915 through the bypass path. When the main steam flow rate increases, the mismatch control unit outputs a water supply flow rate request signal S, which has the content of an increase in the water supply flow rate commensurate with the increase in the main steam flow rate. This increase in the main steam flow rate causes a decrease in core pressure, and as a result, the number of voids in the reactor rapidly increases due to the depressurization effect, resulting in a rise in the reactor water level. On the other hand, the water level control unit B outputs a water supply flow rate request signal S having the content of narrowing down the water supply flow rate in order to control the rise in the reactor water level.

When such a transient phenomenon occurs, the priority for the reactor should be to suppress the rise in the reactor water level. Nevertheless, the total water supply flow request signal S, given to the flow rate controller C, is the signal 8. of the mismatch controller AI- et al. water supply increase request and signal from water level control unit B8. As a result, the water supply flow rate reduction to suppress the rise in the reactor water level cannot be achieved sufficiently, and as a result, the reactor water level reaches the high water level trip point, forcing the plant to shut down. becomes. Here, the high water level trip point is defined as the reactor water level becoming too high, which reduces the efficiency of the steam separator 4, increases the amount of non-humidity contained in the steam supplied to the main turbine 13, and damages the turbine equipment. This is the water level set to protect against adverse effects.

As described above, with conventional water supply control devices, it is difficult to smoothly control the sudden rise in reactor water level due to a drop in core pressure.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a water supply control device that can eliminate the drawbacks of the conventional devices and minimize the sudden rise in reactor water level due to a drop in core pressure.

The first feature of the present invention is to monitor initial events that cause fluctuations in reactor internal pressure and reactor water level, and to narrow down the necessary water supply flow rate by separating the mismatch control unit from the control system when an abnormality occurs. It's in the middle of nowhere.

Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 4 shows a conceptual diagram of the control operation of the water supply control device according to the present invention, and FIG. 5 shows an embodiment of the water supply control device according to the present invention. Furthermore, among these figures, Figures 2 and 3 I! ! The same parts as 1 are denoted by the same reference numerals, and the explanation thereof will be omitted.

First, with reference to FIG. 4, we will explain the control operation concept of the feed water control device of the present invention. When an event that causes a pressure transient event that affects the reactor water level (hereinafter referred to as an "initial event" (in Figure 4, the bypass valve misidentification applies) occurs, the mismatch control section is disconnected and controlled by the circuit. The advantage is that the system is disconnected from the system and the water supply flow rate is restricted in this state.

In FIG. 5, the difference from the conventional control device (FIG. 2) is that a disconnection circuit B is provided between the mismatch control section A and the addition calculation circuit Σ. This disconnection circuit B is an occurrence signal S of an initial event that is thought to cause a fluctuation in the reactor core pressure and therefore a fluctuation in the reactor water level.

, a determination condition signal S21 for determining whether the signal content causes a reactor water level fluctuation, a disconnection pressure set value signal 814 corresponding to the pressure value at which disconnection should be performed, and a core pressure signal S, , V input. The signal is used to disconnect the mismatch controller A in response to an initial event preceding the pressure fluctuation and a drop in core pressure. The details are described below.

FIG. 6 shows an example of the configuration of the disconnection circuit B. Core pressure signal srs and separation pressure set value signal S, 4 is comparator A;
is input. Comparative good person has both signals S1. and S, 4, and as a result, if the value of the core pressure signal 18 is lower than the value of the disconnection pressure set value S□ (srs<SI4>, the disconnection command signal S, is output to the switch circuit A. .With this disconnection command signal 4 degrees, the switch circuit A is switched to the fence release side C1.

As a result, the mismatch control unit A is disconnected, and therefore the first water supply flow rate signal S is interrupted and sent to the addition calculation circuit Σ.

Moreover, the core pressure signal s1. If the value of is not less than the value of the disconnection pressure set value signal S, 4 (S+ S≧514)
is the disconnection command signal 8. . Therefore, the switch circuit 4 maintains the C connection as it is. This state is a normal state, and the first water supply flow rate signal B passes through the switch circuit circuit 4 up to the point t and is output to the addition calculation circuit. On the other hand, the initial event occurrence signal 81. and the judgment signal S,.

is input to the initial event determination circuit A. Here, the initial event occurrence signal 81. For example, according to the example shown in FIG.
The determination signal Sil+ is information necessary to determine whether opening the bypass valve 12 is correct for the plant, such as core pressure and reactor power. First of all -
Event occurrence signal S8. and judgment signal 8. Based on yK, the initial event judgment circuit determines whether an event that causes a rise in the water level is currently occurring or not.As a result of the 0 judgment, if it is determined that an initial event has occurred, it issues a disconnection command signal. S1. is sent to the switch circuit 4, and the switch A is switched to the disconnecting side C1. By this switching, the mismatch control section is disconnected and the first water supply flow rate request signal S is output.

It is cut off. If it is determined that no initial event has occurred, the disconnection command signal 811 is not issued, and therefore switches A, maintain their connection to C,@.

In this way, when the switch A is switched to the disconnecting side C, the switch A is connected to the ground A, and as a result, the signal S4 input to the addition circuit Σ. The content is to instruct the water supply flow i and the request ze. As a result, the content of the water supply flow rate request signal S, which is supplied to the flow rate control unit CK, becomes only the second water supply flow rate signal S, and the rotational speed of the water supply pump 19 is selectively controlled to S, resulting in a sudden decrease in the water supply amount.

Next, FIG. 7 shows a comparison between the feed water control device of the present invention and the conventional device in terms of the response of the feed water flow rate and the control response of the reactor water level.
Shown in a) and (b). In the figure, N shown by a solid line is for the present invention, and 0 shown by a broken line is for the conventional case. As can be seen, in the conventional method, the narrowing down of the onboard water flow is delayed due to the above-mentioned reasons, but according to the present invention, it can be narrowed down rapidly, so the rate of decrease in the water supply flow rate is extremely fast (Fig. ). Along with this, the reactor water level ((b
) Figure) does not increase significantly, and can be suppressed to the minimum without exceeding the plant trip [[T-] as in the conventional case.

As described above, according to the present invention, when the reactor pressure decreases due to some reason, the increase in the reactor water level can be suppressed to a minimum, thereby making it possible to avoid unnecessary plant trips.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the overall configuration of a boiling water nuclear power plant and the configuration of the water supply control system, Figure 2 is a block diagram showing the configuration of a conventional water supply control device, and Figure 3 is a diagram showing the configuration of a conventional water supply control system. 4 is an explanatory diagram of the operation of the water supply control device according to the present invention, FIG. 5 is a block diagram showing an embodiment of the water supply control device according to the present invention, and FIG. 6 is a diagram illustrating the disconnection circuit in the present invention. The block diagrams shown in FIGS. 7(a) and 7(b) are explanatory diagrams comparing the control response of the feed water flow rate and the reactor water level between the conventional system and the present invention.・Water level control section, C・
・・Water supply flow rate control unit, B, ・・Disconnection circuit, A,・・
・Comparison calculator, A,... Initial event judgment circuit, A4...
・Switch circuit, Sl...Steam flow rate signal, S,...
Water supply flow rate signal, S,...First water supply flow rate request signal, S,
...@22 water supply flow rate signal, S, ...total water supply flow rate signal,
Sl. ... Water supply pump flow rate signal, 811 ... Flow rate deviation signal, S11 ... Opening request signal, S□ ... Water level setting signal, S, 4 ... Disconnection pressure setting value signal -5rs"'
Output signal, Sl,...Initial event occurrence signal, S,?・・・
・Judgment signal, Sl, ... core pressure signal s 5lsl
s. ..., disconnection command signal.

Claims (1)

[Scope of Claims] 1. A mismatch control unit that outputs a first feed water flow rate request signal that controls the feed water flow rate and the reactor outlet steam flow rate to be in an equilibrium state using the feed water flow rate signal and the reactor outlet steam flow rate signal as input signals; a water level control unit that outputs a second water supply flow rate request signal for keeping the reactor water level constant using a reactor outlet steam flow rate signal and a preset reactor water level set value signal as input signals; Water supply control for a boiling water reactor, comprising: a feed water flow rate control unit that calculates a deviation between a sum signal of two feed water flow rate request signals and a feed water pump flow rate signal, and outputs a current control signal for a feed water pump based on the deviation signal. By inputting a reactor internal pressure signal and a detection signal of an initial event prior to a fluctuation in reactor water level as a prediction signal, and disconnecting the mismatch control section in response to this prediction signal, A water supply control device for a boiling water reactor, comprising a disconnection circuit that outputs a first water supply flow rate request signal. 2. The disconnection circuit compares the reactor pressure signal with a preset disconnection pressure set value signal, and when the reactor pressure signal is lower than the disconnection pressure set value, the disconnection command cooling signal of the mismatch control section is sent. A comparator that outputs an initial event detection signal is input, and depending on the content of the detection signal, a rise in the reactor water level is detected -f? An initial event determination circuit that determines whether or not a 71st period event has occurred and outputs a disconnection command signal for the mismatch control section when it has occurred; and an initial event determination circuit that outputs a first water supply flow rate request signal when receiving the disconnection command signal. It is equipped with a switch circuit that shuts off! A water supply control device for a boiling water reactor as claimed in claim 1, wherein the boiling water reactor has the following characteristics: