JP2740000B2 - Reactor emergency stop device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a reactor emergency stop device for emergency stop of a reactor.

(Prior art) The emergency shutdown device for nuclear reactors is to insert all control rods in an emergency (scram) to protect the reactor when a situation that may impair the safety of the reactor occurs or is expected to occur. It has a function to make it work.

Hereinafter, a conventional reactor emergency stop device will be described with reference to the schematic configuration diagram of FIG.

FIG. 2 shows only a control rod drive mechanism for one control rod of the reactor and its emergency stop device. However, in practice, a plurality of control rods are provided, and multiplexing and Redundancy has been implemented.

In general, occurrence or anticipation of a situation that may impair the safety of a reactor is determined by whether or not a parameter important for reactor safety exceeds a certain set value. This important parameter is constantly monitored by the detector 1. The detection signal of the detector 1 is sent to the scrum logic circuit 2 and the necessity of the scrum operation is determined. When the scrum is required, the scrum signal S1 is generated.

 First, the emergency insertion operation of the control rod will be described.

The scram inlet valve 4 and the scrum outlet valve 5 of the water pressure control unit 3 are closed during normal operation, but the scram inlet valve 4 is opened during scram, and high-pressure driving water is supplied from the accumulator 6 to the cylinder 8 of the control rod drive mechanism 7. The scram outlet valve 5 is opened and the control rod drive mechanism 7 is opened.
The driving water of the cylinder upper part 9 is discharged to the scrum discharge container 10. Therefore, the control rod drive mechanism 7 is inserted into the reactor from below upward. The water pressure control unit 3 and the control rod drive mechanism 7 are provided for each control rod.

Next, the opening and closing control of the scrum inlet valve 4 and the scrum outlet valve 5 will be described.

The scrum inlet valve 4 and the scrum outlet valve 5 are pneumatically operated and are designed to open when air pressure is lost. Normally, instrumentation air is supplied to the scrum air header 11, and the air pressure keeps the scrum inlet valve 4 and scrum outlet valve 5 closed.

As described above, when the scrum signal S1 is generated, the scrum pilot valve 12 unique to each control rod operates to shut off the supply side of the instrumentation air and open the exhaust side, and the inside of the scrum air header 11 is opened. Because the air is exhausted,
The air pressure is lost, the scrum inlet valve 4 and the scrum outlet valve 5 open, the control rod drive mechanism operates, and the control rod is inserted urgently.

Furthermore, independently of the scrum pilot valve 12, a common emergency stop valve 13 is provided for all control rods, and the common emergency stop valve 13 also exhausts the scrum air header 11 with the scrum signal S1, A scrum operation can be performed.

As described above, the reactor emergency stop device exhausts the air in the scram air header 11 by the scrum signal S1, thereby urgently inserting the control rod to stop the nuclear fission reaction in the reactor.

On the other hand, as described above, the reactor emergency shutdown device is to insert all control rods urgently (scram) to protect the reactor in a situation where the safety of the reactor may be impaired. If the furnace emergency shutdown device loses its function,
Since the accident progresses very quickly thereafter, there is a case where the operator does not have enough time to converge the accident using another system and to ensure safety. Should such a situation occur, the safety of the reactor could not be maintained and a major accident could occur.

For this reason, reactor emergency shutdown devices are highly multiplexed and redundant, and are designed to be extremely reliable.
Although the probability of occurrence of such a situation is very small, considering the effects at the time of failure, there is a possibility that it is not necessarily negligible compared to the risk caused by other causes.

The most probable cause of the failure of the reactor emergency shutdown device is a failure of the scrum logic circuit 2 and then a failure of the detector 1. Therefore, in order to further improve the reliability of the reactor emergency shutdown function,
It is necessary to provide a logic circuit and a detector completely independent of the scrum logic circuit 2 or the detector 1.

As such equipment, alternative control rod insertion systems have been developed in the United States and other countries. This, as mentioned above,
Detectors that are completely independent of the reactor emergency shutdown device for parameters that would make the subsequent actions very severe for reactor safety in the event of a scrum failure14,
An alternative control rod insertion logic circuit 15 is provided. Then, for a parameter that has a very severe effect on the safety of the reactor, the alternative control rod insertion logic circuit 15 generates an alternative control rod insertion signal S2, thereby providing an independent control valve having the same function as the post-installation emergency stop valve 13. By operating the alternative control rod insertion valve 16, the air in the scrum air header 11 is exhausted, and the reliability of emergency insertion of the control rod is improved.

(Problems to be Solved by the Invention) By the way, in addition to the reactor emergency stop device as described above, it is necessary to further provide an alternative control rod insertion system.
It is very effective for improving the reliability of emergency insertion of control rods, but when this alternative control rod insertion system is fed back to an existing plant and added, there are the following problems. .

In other words, if the control rod insertion system is added to an existing plant, plant remodeling work to add the alternative control rod insertion valve 16 to the scrum air header 11 is required, which requires considerable cost. Required.

However, the main factor contributing to the loss of function of the reactor emergency stop device is not the failure of the back-up emergency stop valve 13 but the failure of the scram logic circuit 2 and the detector 1, and the addition of this alternative control rod insertion valve 16 The construction was difficult and there was a problem that it did not contribute much to the improvement of reliability in spite of the cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nuclear reactor emergency stop device that can significantly improve the reliability of a nuclear reactor emergency stop function and can be easily introduced into an existing plant. It is in.

[Constitution of the Invention] (Means and Actions for Solving the Problems) In order to achieve the above object, the present invention provides a detector for detecting a parameter of a reactor and a detection signal obtained from the detector. A logic circuit for generating an emergency stop signal for the reactor, and the emergency stop signal controls the exhaust valve specific to each control rod and a rear emergency stop valve common to all control rods to exhaust air from the air header. In a reactor emergency stop device for emergency stop of a reactor by urgently inserting a rod, a detector independent of the detector and a logic circuit independent of the logic circuit are provided, and the independent detector and the logic circuit Also, the invention is characterized in that the rear emergency stop valve is operated to make an emergency stop of the nuclear reactor.

According to the reactor emergency stop device of the present invention, the reliability of the reactor emergency stop device of the existing plant can be reduced only by adding a relatively inexpensive alternative control rod insertion logic circuit and a detector for monitoring an input signal to the logic circuit. Inexpensive and simple construction can greatly improve the performance.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of one embodiment of the present invention, and the same components as those of the conventional example shown in FIG.

 First, the emergency insertion operation of the control rod will be described.

The scram inlet valve 4 and the scrum outlet valve 5 of the water pressure control unit 3 are closed during normal operation, but the scram inlet valve 4 is opened during scram, and high-pressure driving water is supplied from the accumulator 6 to the cylinder 8 of the control rod drive mechanism 7. The scrum outlet valve 5 is opened at the same time as the
The driving water of the cylinder upper part 9 is discharged to the scrum discharge container 10. Therefore, the control rod drive mechanism 7 is inserted into the reactor from below upward. The water pressure control unit 3 and the control rod drive mechanism 7 are provided for each control rod.

Next, the opening and closing control of the scrum inlet valve 4 and the scrum outlet valve 5 will be described.

The scrum inlet valve 4 and the scrum outlet valve 5 are pneumatically operated and are designed to open when air pressure is lost. Normally, instrumentation air is supplied to the scrum air header 11, and the air pressure keeps the scrum inlet valve 4 and scrum outlet valve 5 closed.

As described above, when the scrum signal S1 is generated, the scrum pilot valve 12 unique to each control rod operates to shut off the supply side of the instrumentation air and open the exhaust side, and the inside of the scrum air header 11 is opened. Because the air is exhausted,
The air pressure is lost, the scrum inlet valve 4 and the scrum outlet valve 5 open, the control rod drive mechanism operates, and the control rod is inserted urgently.

Furthermore, independently of the scrum pilot valve 12, a common emergency stop valve 13 is provided for all control rods, and the common emergency stop valve 13 also exhausts the scrum air header 11 with the scrum signal S1, A scrum operation can be performed.

The emergency insertion operation of the control rod and the opening / closing control of the scrum inlet valve 4 and the scrum outlet valve 5 described above are the same as in the conventional example. In the present embodiment, a detector 14 independent of the conventional detector 1 is provided, and a detection signal for a parameter of a reactor pressure high and a reactor water level low, which makes it very difficult to cope with a scram failure, is provided by a scram. The alternative control rod insertion logic circuit 15 which is independent of the logic circuit 2 is input to generate an alternative control rod insertion signal S2 completely independent of the scrum signal S1,
The system is configured so that the existing rear emergency stop valve 13 is operated to exhaust the scrum air header 11 and to perform emergency insertion of the control rod.

In the case of the present embodiment, the scram logic circuit 2 and the detector 1 that have made the largest contribution to failure in the conventional reactor emergency stop device are made redundant and diversified. The properties are greatly improved. Furthermore, installation and remodeling of the alternative and complicated control valve for the complicated and expensive scrum air header 11 is not required, so it can be introduced into existing plants simply by adding relatively inexpensive logic circuits and detectors. Becomes

Further, in this embodiment, the case where the detector 14 is provided independently of the existing detector 1 has been described. However, if the existing detector 1 is used as the detector 14, the reactor emergency of the existing plant can be manufactured at a lower cost. The reliability of the stopping device can be improved.

Note that the detector 14 does not necessarily need to be installed for all scrum parameters, and only needs to be installed for parameters that make it extremely difficult to deal with a scrum failure as described above.

[Effects of the Invention] As described above, according to the present invention, the reliability of a nuclear reactor emergency shutdown device in which it is extremely difficult to mitigate the effects of a loss of function is greatly improved. And the safety of the reactor is further improved. Further, it is possible to relatively easily perform the introduction into the existing plant as well as the introduction into the new plant.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a reactor emergency stop device according to one embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional reactor emergency stop device. 1,14 ... Detector, 2 ... Scrum logic circuit 3 ... Hydraulic pressure control unit, 4 ... Scrum inlet valve 5 ... Scrum outlet valve, 6 ... Accumulator 7 ... Control rod drive mechanism, 8 ... Cylinder part 9 ... Cylinder upper part, 10 ... Scrum discharge container 11… Scrum air header 12… Scrum pilot valve 13… Emergency stop valve 15… Alternative control rod insertion logic circuit 16… Alternative control rod insertion valve

Claims (1)

(57) [Claims] 1. A detector for detecting parameters of a nuclear reactor,
A logic circuit that generates an emergency stop signal of the reactor based on the detection signal obtained from the detector, and an exhaust valve specific to each control rod and a post-installation emergency stop valve common to all control rods by the emergency stop signal. In a reactor emergency stop device for operating a reactor by urgently inserting a control rod by operating and exhausting air from an air header, a detector independent of the detector and a logic circuit independent of the logic circuit And the emergency stop valve is operated by the independent logic circuit to stop the reactor in an emergency.