JP3119884B2 - Instrument interlock circuit for reactor water level - Google Patents

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 reactor.

[0003]

2. Description of the Related Art A conventional reactor water level instrumentation interlock circuit of a boiling water reactor has only a reactor water level high set point,
The reactor water level rises regardless of the type of transient fluctuation, and the turbine is stopped when a high reactor water level signal is output.

[0004] Reactor water levels in a boiling water reactor are raised mainly because an abnormality occurs in the water supply control system and a large amount of water is brought into the reactor. There are two things due to the stoppage of the circulation pump. In the former case, the reactor water level continues to increase monotonically because a large amount of feedwater is continuously introduced, and the temperature of the feedwater is low.
Normally, the reactor core power is increased at the same time as positive reactivity is injected into the core. On the other hand, in the latter case, the reactor water level rise is temporary, and even if the reactor water level rises, the water supply control system is sound and the water supply flow rate is automatically increased. Suppressed, the reactor water level returns to its original state again. Conventionally, even in such a case, once a reactor water level high signal is output, the turbine is stopped and the reactor is also scrammed.

[0005]

When the reactor water level rises, the moisture in the steam generated in the reactor generally increases, which is not desirable in terms of turbine efficiency and soundness. Shutting down the turbine at a high reactor water level is a necessary interlock, but is acceptable for a limited time. However, in cases where the water level rises temporarily as in the case where the recirculation pump is stopped and the water level of the reactor can be expected to drop immediately due to a sound water supply control system, the turbine and the reactor must be stopped. Therefore, it is preferable that the operation of the nuclear power plant be improved by avoiding the problem and continue the operation.

The present invention has been made in order to solve the above-mentioned problem. Usually, the turbine is stopped at a high reactor water level signal. However, when the reactor water level rises due to the stoppage of the recirculation pump, the present invention has been made. , So that the reactor can be continuously operated without stopping the turbine at the reactor water level high signal, and if the reactor water level high signal continues for more than a few seconds, In order to protect the turbine when the reactor water level signal is output, it is necessary to provide a reactor water level instrumentation interlock circuit for the boiling water reactor configured to stop the turbine and improve the operation rate of the reactor. is there. [Configuration of the Invention]

The present invention provides a reactor water level high setting and a reactor water level high setting for inputting a signal from a reactor water level meter,
A time limit circuit for inputting a water level high signal of the reactor water level setting and a stop signal of a control circuit of the recirculation pump is provided, and a signal indicating that the time limit circuit is not operating or the water level of the reactor water level high setting is high. A control circuit for outputting a command signal to the turbine when any of the signals is input is provided.

[0008]

[Operation] When an abnormality occurs in a water supply control system for supplying water to the reactor and a large amount of water is brought in, the reactor water level rises. The occurrence of a high reactor water level signal causes the turbine to shut down immediately and prevent moisture-rich steam from being directed to the turbine. At the same time as the turbine shuts down, the reactor also scrams.

On the other hand, if the reactor water level rises due to the stoppage of the recirculation pump, even if the reactor water level high signal is generated,
Shutdown of the turbine is suspended by a timed circuit that starts operation at the same time. The set value of the time limit circuit is appropriately 5 to 10 seconds. If the reactor water level high signal is output after 5 to 10 seconds, the turbine is stopped. However, when the reactor water level normally rises due to the stoppage of the recirculation pump, the reactor water level immediately returns to the original level due to the automatic reduction of the feedwater flow rate by the operation of the sound water supply control system. As a result, the shutdown of the turbine is avoided, and the reactor can be operated continuously.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an interlock circuit for a reactor water level instrument according to the present invention will be described with reference to the drawings. FIG. 1 schematically shows a portion of a boiling water reactor related to the present invention, and FIGS. 2 and 3 show a case where a feedwater flow rate is abnormally increased due to a failure of a feedwater control system and a case where a recirculation pump is stopped. FIG. 4 shows a temporal response of the reactor water level and the feedwater flow rate in the case of FIG.

In FIG. 1, a water supply pipe 2 is connected to a reactor pressure vessel 1, and a water supply pump 3 is provided in the water supply pipe 2. The feedwater pump 3 feeds a feedwater flow rate to the reactor pressure vessel 1 according to a command from the feedwater control circuit 4. Further, a main steam pipe 5 is connected to the reactor pressure vessel 1, and guides 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, a stand pipe 8, a steam separator 9, a steam dryer 10 and the like for generating heat. A recirculation pump 11 is provided.

In a normal operation state, the water level of the reactor is near the middle of the steam separator 9, and the reactor water level setting in the present design is about 40 to 50 cm higher. Now, in such a boiling water reactor, assuming that the feedwater pump 3 keeps sending the maximum feedwater flow rate to the reactor because, for example, the feedwater control circuit 4 has failed, the water level of the reactor becomes as shown in FIG. Increase monotonically. On the other hand, when the recirculation pump 11 stops, the reactor water level initially increases as shown in FIG. 3, but the reactor water level immediately falls below the reactor water level setting due to the automatic reduction of the feedwater flow rate. . According to the results of the dynamic characteristic analysis, the reactor water level exceeds the reactor water level setting for only a few seconds in the current design.

Next, the interlock circuit will be described with reference to FIG. In FIG. 4, a reactor water level high setting 13 and a reactor water level high setting 14 are provided, and an output signal from the reactor water level gauge 12 is input to these settings 13 and 14. The signal of the reactor water level setting 13 and the stop signal 17 from the control circuit 20 of the recirculation pump are input to the time limit circuit 18 . Reactor water level height setting 14 water level height
Signal 16 and a timed circuit if the reactor water level rises
The time limit circuit 18 to 18 is a signal 19 is not in operation providing a control circuit 21 for receiving. The control circuit 21 controls the recirculation pump.
If the reactor water level high signal 15 continues after a certain period of time after the stop signal 17 from the control circuit 20 is established , or if the reactor water level high signal 16 is output , a command signal 22 is sent to the turbine 6,
The turbine 6 is stopped.

When the reactor water level based on the water level signal from the reactor water level gauge 12 is higher than the reactor water level setting 13 and exceeds the reactor water level setting 13, the interlock circuit sets the reactor water level high signal 15 to a time limit. The signal is input to the control circuit 21 via the circuit 18 . Ma
In addition, the reactor water level based on the water level signal from
If the reactor height is set higher than the maximum setting14,
The reactor water level at most signal 16 is input to the control circuit 21. Control circuit
A stop signal 17 generated from the control circuit 20 of the recirculation pump and indicating that the pump has stopped is led to 21, and the time limit circuit 18 is activated by the simultaneous establishment of the high water level signal 15 and the stop signal 17.

The rise in the reactor water level causes the reactor water level
If the signal 15 is input to the control circuit 21,
Signal 19 indicating that 18 is not operating and high water level signal
The control circuit 21 outputs a command signal 22 to the turbine 6 so that the turbine is stopped for the first time when any of the conditions 16 is satisfied. The operation time of the time limit circuit 18 is set within a range in which the soundness of the turbine is allowed even if the reactor water level continues to exceed the reactor water level high setting 13 and steam with slightly increased moisture is sent to the turbine 6. Ru determined Tei.

The reactor water level setting 13 is set as low as possible within the range of the water level fluctuation of the reactor during normal operation. This value is set so that the reactor water level rise in the current design will not reach this setting even if a limited number of pumps out of a large number of recirculation pumps stop. Considering what has been decided, it can be set lower than this. Also, by setting such a low value, as in the case of an abnormality in the water supply control system,
This is a preferable design because the reactor water level high signal can be issued as soon as possible when the turbine or the reactor is to be shut down soon.

The reactor water level is set at such a level that if the reactor water level rises above this level, the turbine must be stopped immediately because the steam moisture sent to the turbine abnormally increases. .

[0019]

According to the present invention, when the water level of the recirculation pump rises temporarily, the reactor can be continuously operated without stopping the turbine for several seconds. Further, the turbine can be stopped even during the operation of the time limit circuit to protect the turbine.

[Brief description of the drawings]

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 a relationship between a reactor water level and a feedwater flow rate when the feedwater flow rate increases.

FIG. 3 is a characteristic diagram showing a relationship between a reactor water level and a feedwater flow rate when a 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, 13: Reactor water level high setting, 14: Reactor water level high setting, 15 ... Reactor water level high signal, 16 ... Reactor water level high signal, 17 ... Recirculation pump stop signal, 18 ... Time limit circuit, 19 ... Time limit circuit Signal indicating that is not operating, 20 ... control circuit of recirculation pump, 21 ...
Control circuit, 22 ... command signal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21D 3/04

Claims (1)

(57) [Claims] A reactor water level setting and a reactor water height setting for inputting a signal from a reactor water level meter are provided, and a water level high signal for the reactor water level setting and a stop signal for a control circuit of a recirculation pump are provided. A time signal circuit is provided, and a command signal is output to the turbine when either the signal indicating that the time circuit is not operating or the high water level signal of the high reactor water level is input. A reactor water level instrumentation interlock circuit comprising a control circuit.