JPS61282705A - Feed water controller for nuclear 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] [Technical Field of the Invention] The present invention provides a boiling water atomic saw plant (hereinafter referred to as a BWR plant) that, when a generator load shedding occurs,
The present invention relates to a reactor water supply control system that corrects the water level behavior of the reactor water level, improves the ability to suppress water level fluctuations, and makes it possible to secure margin for the reactor water level low scram set point.

[Background Art of the Invention and Problems thereof] Generally, in a BWR plant, when generator load shedding occurs, voids are generated due to reactor coolant recirculation trip and reactor pressure drop, and then nuclear Reactor water level rises. Due to this temporary rise in the reactor water level, the water supply control system reduces the water supply flow rate. At the same time, selective control rods are inserted and recirculation pump trips are performed, resulting in a decrease in reactor power, a reduction in voids, and a significant drop in reactor water level. As described above, due to the large drop in the reactor water level, the margin for the reactor water level low scram set point became strict, and there was a risk that the transition to isolated operation within the power plant after generator load shedding would be delayed.

[Purpose of the Invention] The present invention has been made based on the above points, and its purpose is to reduce the amount of water level drop in the reactor due to generator load shedding, and to reduce the amount of water level drop in the reactor due to generator load shedding, and to lower the reactor water level low scram set point. An object of the present invention is to provide a nuclear reactor water supply control device that can secure a margin for

[Summary of the Invention] In other words, the reactor water supply control device according to the present invention can control the three elements of the steam flow rate from the reactor, the water supply flow rate to the reactor, and the water level of the reactor, or only the water level of the reactor. In order to suppress a large drop in the reactor water level, a reactor water level correction circuit is installed, and the water supply control signal is corrected by the set point adjustment signal from the reactor water level correction circuit. This system is characterized by preventing a decrease in the water supply flow rate and, in turn, a significant decrease in the reactor water level.

In other words, instead of the conventional control that attempts to reduce the water supply flow rate due to the temporary rise in the reactor water level when the generator is stopped, this is corrected by the reactor water level correction circuit to suppress the drop in the water supply flow rate. This will prevent a significant drop in the reactor water level/υ.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing the configuration of a reactor water supply control II device. Reference numeral 1 in the figure is a reactor pressure vessel, and a reactor core 2 is accommodated within this reactor pressure vessel 1. The coolant 3 flows upward through the reactor core 2, and its temperature increases due to the heat of nuclear reaction in the reactor core. The heated coolant 3 enters a two-phase flow state of water and steam, flows into a steam separator installed above the reactor core 2, and is separated into steam and water. The separated internal steam flows into the steam dryer and is dried to become dry steam, which is transferred to the turbine 5 via the main steam pipe 4 and
to drive. A generator 6 is connected to the turbine 5, and the turbine 5 is driven to generate electricity. The generated power obtained by the power generation is supplied to the power transmission line 8 via the circuit breaker 7 . A condenser 9 is connected to the turbine 6, and the steam that has done work in the turbine 5 is introduced into the condenser 9 and condensed to become condensed water. The condensate flows into the water supply pipe 1 through a condensate line (not shown) and is returned into the reactor pressure vessel 1 by the water supply pump 11.

A turbine steam control valve 12 is inserted in the main steam pipe 4 in front of the turbine 5, and a bypass pipe 13 is provided between the turbine steam control valve 12 and the condenser 9. ing. A bypass valve 14 is inserted into this bypass piping 13, forming a bypass system. This bypass system has the following functions. That is, when the generator 6 stops, it is necessary to stop the supply of steam to the turbine 5, and therefore an operation is performed to reduce the reactor output, but it takes a certain amount of time before the steam flow rate decreases due to such operation. Therefore, if left as is, steam will be supplied to the turbine 5 in an amount close to that during rated operation, which may impair the health of the turbine 5. Therefore, an operation is performed to bypass the steam to the condenser 9 via the bypass system. Further, the bypass system of this embodiment has a function of bypassing all of the steam flow rate during rated operation when it is 100%, and is called a 100% bypass plant.

Next, the configuration of a reactor feed water flow rate control device that controls the flow rate of feed water supplied into the reactor pressure vessel 1 via the water supply pipe 10 will be described. A steam flow rate detector 21 is inserted into the main steam pipe 4, and a water supply flow rate detector 22 is inserted into the water supply pipe 10. Also, reactor pressure vessel 1
A reactor water level detector 23 is installed to detect the level of reactor water inside the reactor. Normally, reactor feed water control is performed using so-called three-element control based on detection signals from the main steam flow rate detector 21, feed water flow rate detector 22, and reactor water level detector 23. When stopping or starting a nuclear reactor, so-called single-element control is performed based only on the reactor water level among the three elements mentioned above, thereby controlling the water supply flow rate. This will be explained in detail below.

Reference numeral 31 in the figure indicates a first comparator, and this first comparator 31 receives a steam flow rate detection signal 21A from the steam flow rate detector 21 and a feed water flow rate detection signal 22A from the feed water flow rate detector 22. is input.

The first comparator 31 compares these signals and outputs a deviation signal 31A to the second comparator (adder) 32. On the other hand, the water level detection signal 23A from the reactor water level detector 23 is output to the third comparator 33. This third comparator 3
3, a setting signal 34A is output from the water level setting device 34. The third comparator 33 compares these signals and outputs a deviation signal 33A to the second comparator 32.

This second comparator 32 compares this deviation signal 33A and the deviation signal 31A, and outputs a deviation signal 32A to the water supply controller 36 via the changeover switch 35. This water supply controller 36 has a built-in integral function, and the above deviation signal 3
2A, a control signal 36A is output to the water supply turbine 37. The water supply turbine 37 is driven based on the control signal 36A to drive the water supply pump 11 and supply a predetermined amount of water. The changeover switch 35 has contacts X and Y, and the contact X side is closed when performing the above-mentioned three-line control. Contact Y is opened in the case of single element control, which will be described later. Further, when rated operation is being performed, the steam flow rate detection signal 21A and the water supply flow rate detection signal 22A are equal, so the deviation signal 31A is zero. Similarly, the deviation signal 32A output from the reactor water level detector 32 to the feed water controller 36 is zero, and in that case, the feed water controller 36 outputs the rated flow rate control signal 36 to supply the rated flow rate.
A will be output to the water supply turbine 37.

Next, the case of single element control will be explained. In this case, the contact of the changeover switch 35 is switched to the Y side, and the deviation signal 33A from the third comparator 33 is directly input to the water supply controller 36. In other words, the water supply flow rate is controlled only by the reactor water level. As mentioned above, such single-element control is used, for example, when stopping a nuclear reactor during periodic inspections or restarting it, and when the other two elements are in an unstable state. It will be adopted from

A reactor water level correction circuit 41 is installed in the water supply flow rate control device having the above configuration. In other words, if the generator 6 is stopped, there is a risk that the reactor water level will drop significantly after the next rise in the reactor water level, and the margin for the reactor low water level scram set point will become smaller, causing unnecessary There is a risk of a nuclear reactor scram occurring. This is because, due to the above-mentioned temporary rise in the reactor water level, a control signal is output to reduce the water supply flow rate in order to lower this. The correction circuit 41 corrects the control signal to suppress a significant decrease in the water supply flow rate and the resulting significant decrease in the reactor water level.

The reactor water level correction circuit 41 is comprised of a program function generator 42 and a reactor water level set point regulator 43, and outputs a set point adjustment signal 41A. Further, the reference numeral 44 in the figure is an opening/closing contact, and this opening/closing contact 44 includes:
An operating state circuit 45 is connected. That is, during normal operation, the operating state circuit 45 does not operate.
Therefore, the opening/closing contactor 44 is in an open state as shown in the figure, and the set point adjustment signal 41A from the correction circuit 41 is not output. On the other hand, when the generator 6 is stopped, the operating state circuit 45 is activated by the stop signal.
The opening/closing contact 44 is closed.

Therefore, the set point adjustment signal 41A is outputted to the third comparator 33 via the switching contact 44. This allows the third
The deviation signal 33A from the comparator 33 is corrected and output to the second comparator 32. As a result of the above actions, the feed water flow rate reduction signal based on the primary rise in the reactor water level is corrected.
The reduction in water supply flow rate and the resulting significant drop in reactor water level will be alleviated.

More specifically, due to the temporary rise in the reactor water level, the reactor water level detector 23 outputs a detection signal 23A exceeding the setting signal 34A to the third comparator 33. Therefore, if this is not equivalently corrected, control will be performed to suppress the rise in the reactor water level in accordance with the deviation, and as a result, the water supply flow rate will be reduced.

The correction circuit 41 according to this embodiment corrects this, alleviates the decrease in the feed water flow rate and the resulting significant decrease in the reactor water level, and secures margin for the reactor water level low scram set point. .

The operation will be explained based on the above configuration. First, during rated operation, the three-element control is performed as described above, and the second comparator 32 outputs the deviation signal 32A to the flow rate controller 36. Accordingly, the flow rate controller 36 outputs a control signal 36A indicating the rated flow rate to the water supply turbine 37. This allows water to be supplied at the rated flow rate.

Furthermore, single-element control is performed when the reactor is shut down or restarted during periodic inspections, etc. That is, the contact Y side of the changeover switch 35 is closed, and the deviation signal 33A from the third comparator 33 is output directly to the flow rate controller 36. Similarly, the control signal 3 from the flow rate controller 36 is as follows.
6A is output, and desired water supply control is performed via the water supply turbine 37.

Next, a case where the generator 6 stops will be explained.

When the generator 6 stops, the turbine 5 begins to accelerate as the load increases, as described above. In order to prevent such acceleration of the turbine and damage to the turbine 5 caused by it, the turbine steam control valve 12 is throttled and at the same time the bypass valve 1 is closed.
4 is released. As a result, steam is not supplied to the turbine 5, but directly bypassed to the condenser 5A. Simultaneously with this operation, selective control rod insertion and recirculation pump 1 - rip operation are performed, and the station is shifted to independent operation. Here, fluctuations in the water supply flow rate and the reactor water level immediately after the generator 6 stops will be explained. FIG. 2 is a diagram showing time changes in the reactor water level, with time on the horizontal axis and water level on the vertical axis. Line A1 in the figure shows the conventional case, and line A2 shows the case of the present example. Indicate the case. FIG. 3 is a diagram in which the horizontal axis shows time and the vertical axis shows the ratio of the water supply flow rate to the rated time. Line 81 in the figure shows the conventional case, and line 82 shows the case of this embodiment. show. Note that line C in FIG. 2 shows changes in reactor pressure. As is clear from FIG. 2, immediately after the generator 6 stops, the reactor water level temporarily rises (indicated by the cylinder @a in the figure). Conventionally, such a temporary rise in the reactor water level would affect water supply control and reduce the water supply flow rate (as shown in Figure 3).
At the same time, a phenomenon occurred in which the reactor water level dropped significantly due to the reduction in voids caused by the shutdown of the recirculation pump and the reduction in reactor power due to the insertion of selective control rods (
(Indicated by C in the figure). As mentioned above, as a result, the margin for the reactor water level low scram set point becomes strict.

However, in the case of this embodiment, the above-mentioned correction circuit 4
1 is activated. That is, when the generator 6 is stopped, the operating state circuit 45 is activated and the opening/closing contact 44 is opened. By opening and closing the opening/closing contact 44, a set point adjustment signal 41A is output to the third comparator 33. As a result, the deviation signal 33A output from the third comparator 33 is outputted to the second comparator 32 in a corrected state=13-. Specifically, the signal is smaller than the deviation signal that is not corrected. The deviation signal 33A corrected above by the comparator 32 in box 2 below
is compared with the deviation signal 31A from the first comparator 31, and a deviation signal 32A is output to the flow rate controller 36 via the contact X. The flow rate controller 36 outputs a control signal 36A to the water supply turbine 37 based on this deviation signal 32A. The control signal 36A output at this time is designed to reduce the amount of decrease in the water supply flow rate compared to the conventional one (indicated by cylinder number d in FIG. 3). Therefore, the reactor water level will not fall as drastically as before, and specifically, as shown in Figure 2, it will rise by about 15 cm (35 cm -
20cm = 15cm).

It goes without saying that when the generator 6 is not stopped and is in a normal state, the operating state circuit 45 does not operate and the opening/closing contact 44 is in an open state.

According to this embodiment, the following effects can be achieved. That is, when the generator 6 is stopped, the deviation signal 3214-3A output from the third comparator 33 is corrected by the set point adjustment signal 41A from the correction circuit 41, causing a temporary rise in the reactor water level. It is possible to reduce the extent of the decrease in the water supply flow rate caused by this, thereby preventing a decrease in the supply water flow rate and a significant decrease in the reactor water level due to the decrease in the supply water flow rate. As a result, a sufficient margin for the reactor water level low scram set point can be secured, and unnecessary reactor scrams can be prevented.

[Effects of the Invention] As detailed above, according to the reactor water supply control device according to the present invention, it is possible to prevent a decrease in the water supply flow rate when the generator is stopped and a significant decrease in the reactor water level due to this, It is possible to secure a sufficient margin for the reactor water level low scram set point, prevent unnecessary reactor scrams, maintain the health of the plant, and improve the operating rate.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams showing one embodiment of the present invention.
FIG. 2 is a system diagram showing the configuration of the reactor water supply control device, FIG. 2 is a diagram showing temporal changes in the reactor water level, and FIG. 3 is a diagram showing temporal changes in the water supply flow rate. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel, 2... Reactor core, 3... Coolant, 4... Main steam piping, 5... Turbine, 6...
Generator, 10... Water supply piping, 11... Water supply pump,
21... Steam flow path detector, 22... Water supply flow rate detector, 23... Reactor water level detector, 41... Reactor water level correction circuit, 42... Function generator for program, 43・
...Reactor water level set point regulator. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (2)

[Claims] (1) Boiling water type in which water supply to the reactor is controlled using three elements: steam flow rate from the reactor, water supply flow rate to the reactor, and reactor water level, or a single element of only the reactor water level. In the reactor water supply control system of a nuclear reactor, a reactor water level correction circuit is installed in order to suppress the large drop in the reactor water level that is predicted in advance when a generator load cutoff occurs, and A nuclear reactor water supply control device, characterized in that a water supply control signal is corrected using a set point adjustment signal to prevent a drop in the water supply flow rate and a significant drop in the reactor water level. (2) The reactor water supply control system according to claim 1, wherein the reactor water level correction circuit is comprised of a program function generator and a reactor water level set point regulator. .