JPH04291198A - Instrumented interlock circuit for reactor water level - Google Patents

Abstract

PURPOSE:To protect a turbine and also to improve a rate of operation by a method wherein stoppage of the turbine is suspended for several seconds and operation of a reactor is continued when a transitional fluctuation in a rise of a reactor water level occurs and when it is transient. CONSTITUTION:Reactor water level high setting 13 and reactor water level high-high setting 14 are provided and an output signal from a reactor waver level gage 12 is inputted to these settings 13 and 14. A signal of the reactor water level high setting 13 and a stop signal 17 from a control circuit 20 of a recirculation pump are inputted to a time limit circuit 18. A command signal circuit 21 which makes comparison with a signal of the reactor water level high-high setting 14 when a rise of a reactor water level occurs, and makes the time limit circuit 18 transmit a signal 19 showing that this time limit circuit 18 is not in a process of operation, is provided. In the case when the reactor water level high signal 15 continues after a prescribed time as well or when a reactor water level high-high signal 16 is outputted, a turbine 6 is stopped by delivering a command signal 22 to the turbine 6.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor water level instrumentation interlock circuit for a boiling water nuclear reactor.

0003

[Prior Art] Conventional reactor water level instrumentation interlock circuits for boiling water reactors have only a reactor water level high set point;
Regardless of the type of transient fluctuation, if the reactor water level rises and a reactor water level high signal is issued, the turbine is stopped.

Factors that cause the reactor water level to rise in boiling water type light water reactors can be roughly divided into two types: abnormalities in the water supply control system and a large amount of water being brought into the reactor, and recirculation for circulating coolant. There are two types of problems caused by the circulation pump stopping. In the former case, the reactor water level continues to increase monotonically because a large amount of feed water flow is brought in continuously, and the temperature of the feed water is low, so positive reactivity is injected into the reactor core and the reactor output increases. It is common for the numbers to increase at the same time. On the other hand, in the latter case, the rise in the reactor water level is temporary, and even if the reactor water level is set high, the water supply control system is healthy, so the water supply flow rate is automatically adjusted. It is suppressed and the reactor water level returns to its original state. Conventionally, even in such a case, once a reactor water level high signal is issued, the turbine is stopped and the reactor is also scrammed.

[0005]

[Problems to be Solved by the Invention] When the water level of a nuclear reactor rises, moisture in the steam generated in the reactor generally increases, which is unfavorable in terms of efficiency and health of the turbine. Furthermore, although stopping the turbine when the reactor water level is high is a necessary interlock, it is permissible for a limited period of time. However, in cases where the water level rises temporarily, such as when the recirculation pump stops, and the reactor water level can be expected to drop immediately due to a sound water supply control system, the turbine and reactor shutdown may occur. It would be better to aim to improve the operating rate of nuclear power plants by avoiding such problems and continuing operation.

[0006] The present invention was made to solve the above problem. Normally, the turbine is stopped by a high reactor water level signal, but if the reactor water level rises due to the stoppage of the recirculation pump, , the reactor can continue to operate without stopping the turbine due to the reactor water level high signal, and in the unlikely event that the reactor water level high signal continues for more than a few seconds, or To provide a reactor water level instrumentation interlock circuit for a boiling water reactor configured to protect the turbine and improve the operating rate of the reactor by stopping the turbine when a reactor water level high signal is issued. be. [Structure of the invention]

[0007]

[Means for Solving the Problems] The present invention provides a reactor water level high setting and a reactor water level high setting that input an output signal from a reactor water level gauge, and recirculates the water level high signal of the reactor water level high setting. Control that includes a time limit circuit that inputs a stop signal of a pump control circuit, and outputs a command signal to a turbine by comparing a signal indicating that this time limit circuit is not in operation with a water level at-high signal for the reactor water level at-high setting. It is characterized by being equipped with a circuit.

[0008]

[Operation] If an abnormality occurs in the water supply control system that supplies water to the reactor and a large amount of water is brought in, the reactor water level will rise. The generation of a high reactor water level signal causes the turbine to immediately shut down, preventing moisture-enriched steam from being directed to the turbine. Additionally, the reactor will also be scrammed at the same time as the turbine is shut down.

On the other hand, if the reactor water level rises due to the stoppage of the recirculation pump, even if a reactor water level high signal occurs,
Turbine shutdown is suspended by a timed circuit that starts operating at the same time. An appropriate setting value for the time limit circuit is 5 to 10 seconds, and if the reactor water level high signal is still output after 5 to 10 seconds, the turbine is stopped. However, normally, when the reactor water level rises due to the recirculation pump stopping, the water supply flow rate is automatically throttled by the operation of a healthy water supply control system, and the reactor water level quickly returns to its original level. As a result, turbine shutdown is avoided and the reactor can continue to operate.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reactor water level instrumentation interlock circuit according to the present invention will be described with reference to the drawings. Figure 1 schematically shows the parts of a boiling water reactor that are related to the present invention, and Figures 2 and 3 show cases in which the feed water flow rate increases abnormally due to a failure in the feed water control system and the recirculation pump stops. Fig. 4 shows the temporal response of the reactor water level and feed water flow rate in the case where the reactor water level and the feed water flow rate are the same.

In FIG. 1, a reactor pressure vessel 1 is connected to a water supply pipe 2, and the water supply pipe 2 is provided with a water supply pump 3. The feed water pump 3 sends a feed water flow rate to the reactor pressure vessel 1 according to a command from the water supply control circuit 4 . Further, a main steam pipe 5 is connected to the reactor pressure vessel 1 to guide steam generated in the reactor to a turbine 6.

On the other hand, inside the reactor pressure vessel 1 there are a reactor core 7 that generates heat, a stand pipe 8, a steam separator 9, a steam dryer 10, etc., and in order to circulate coolant in the reactor core 7, A recirculation pump 11 is provided.

[0013] Under normal operating conditions, the reactor water level is near the middle of the steam-water separator 9, and the reactor water level height setting in the current design is approximately 40 to 50 cm higher than this. now,
In such a boiling water reactor, if the feed water pump 3 continues to send the maximum flow rate of water to the reactor due to, for example, a failure in the feed water control circuit 4, the water level in the reactor will become monotonous as shown in Figure 2. To increase. On the other hand, when the recirculation pump 11 stops, the reactor water level initially increases as shown in Figure 3, but the reactor water level immediately drops below the reactor water level setting due to automatic throttling of the water supply flow rate. . According to the results of dynamic characteristic analysis, in the current design, the reactor water level exceeds the reactor water level height setting for only a few seconds.

Next, the interlock circuit will be explained with reference to FIG. In FIG. 4, a reactor water level height setting 13 and a reactor water level at most setting 14 are provided, and the output signal from the reactor water level gauge 12 is input to these settings 13 and 14. The reactor water level setting signal 13 and the stop signal 17 from the recirculation pump control circuit 20 are input to the time limit circuit 20 . A control circuit 21 is provided which transmits a signal 19 from a time limit circuit 18 indicating that the time limit circuit 18 is not in operation, in comparison with a signal from a reactor water level setting 14 when a rise in the reactor water level occurs. If the reactor water level high signal continues after a certain period of time, or if the reactor water level high signal is output, command signal 2 is sent to the turbine 6.
2 to stop the turbine 6.

[0015] Therefore, the water level signal from the reactor water level gauge 12 is determined by the reactor water level high setting 13 and the reactor water level maximum setting 1.
4, and if it exceeds that, the reactor water level high signal 15 or the reactor water level at most signal 16 is input to the control circuit 21. A stop signal 17 generated from the control circuit 20 of the recirculation pump and indicating that the pump has stopped is also led to the control circuit 21, and when the high water level signal 15 and the stop signal 17 are established simultaneously, the time limit circuit 18 is activated. .

The control circuit 21 causes the turbine to be stopped only when either the signal 19 indicating that the time limit circuit 18 is not in operation or the water level high signal 16 are established.
outputs a command signal 22 to the turbine 6. Time limit circuit 18
During the operation duration, the reactor water level continues to exceed the reactor water level height setting 13, and steam with slightly increased moisture flows into the turbine 6.
Even if the turbine is sent to the

Further, the reactor water level height setting 13 is determined to be as low as possible within the range of water level fluctuations in the reactor during normal operation. This value is set to prevent the reactor water level from rising to this level even if a limited number of recirculation pumps out of the many recirculation pumps in the current design stop. Considering what has been decided, it is possible to set it lower than this. In addition, by setting it to a low value in this way, a reactor water level high signal can be issued quickly when it is desired to stop the turbine or reactor quickly, such as when there is an abnormality in the water supply control system, making it a preferable design.

[0018] Furthermore, the reactor water level is set at a level such that if the reactor water level rises any further, the moisture content of the steam sent to the turbine will increase abnormally, so the turbine must be stopped immediately. .

[0019]

According to the present invention, in the case of a temporary rise in the water level of the recirculation pump, the reactor can be operated continuously for several seconds without stopping the turbine. Furthermore, the turbine can be protected by stopping the turbine even when the time limit circuit is in operation.

[Brief explanation of the drawing]

FIG. 1 is a system diagram including one embodiment of a reactor water level instrumentation interlock circuit according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the reactor water level and the water supply flow rate when the water supply flow rate increases.

FIG. 3 is a characteristic diagram showing the relationship between the reactor water level and the water supply flow rate when the recirculation pump is stopped.

FIG. 4 is a system diagram showing a control circuit provided in the reactor water level instrumentation interlock circuit of FIG. 1;

[Explanation of symbols]

1... Reactor pressure vessel, 2... Water supply pipe, 3... Water supply pump, 4
... water supply control circuit, 5 ... main steam pipe, 6 ... turbine, 7 ... core, 8 ... stand pipe, 9 ... steam separator, 10 ... steam dryer, 11 ... recirculation pump, 12 ... reactor water level gauge, 1
3...Reactor water level high setting, 14...Reactor water level high setting, 1
5...Reactor water level high signal, 16...Reactor water level high signal, 1
7... Recirculation pump stop signal, 18... Time limit circuit, 19...
A signal indicating that the time limit circuit is not in operation, 20... Control circuit of the recirculation pump, 21... Control circuit, 22... Command signal.

Claims (1)

[Claims] [Claim 1] Provide a reactor water level high setting and a reactor water level maximum setting for inputting an output signal from a reactor water level gauge,
A time limit circuit is provided to input a water level high signal for the reactor water level high setting and a stop signal for the control circuit of the recirculation pump, and a time limit circuit is provided to input a water level high signal for the reactor water level high setting and a stop signal for the control circuit of the recirculation pump, and a signal indicating that the time limit circuit is not in operation and a water level high signal for the reactor water level high setting are provided. An instrumentation interlock circuit for reactor water level, comprising a control circuit for outputting a command signal to a turbine in comparison with a signal.