JP2875827B2 - Control rod drive hydraulic system - Google Patents

Description

The present invention relates to a control rod driven hydraulic system for a boiling water reactor,
In particular, the present invention relates to a control rod drive hydraulic system suitable for efficiently draining waste water and sludge in a scrum discharge container to a drain water tank.

[Prior Art] FIG. 3 is a system diagram of a control rod drive hydraulic system in a conventional boiling water reactor facility. The control rod drive mechanism 3 includes a drive piston 2 connected to the control rod 1, and pressurizes the drive piston 2 by introducing high-pressure water into the lower piston chamber of the drive piston 2 during scram, and inserts the control rod 1 into the core. It is supposed to. At this time, the water staying at the upper part of the drive piston and the reactor coolant leaking from the seal part of the drive piston are discharged from the reactor pressure vessel. Therefore, a scram inlet valve 5 is provided in the middle of a driving water pipe 21 for guiding the high-pressure water stored in the accumulator 4 to the piston lower chamber, and a driving water pipe 22 for discharging the coolant in the pressure vessel.
A scram outlet valve 6 is provided in the middle, and an operating air pipe 23 and a scram pilot valve 7 are provided so as to open and close both the scrum inlet valve 5 and the scram outlet valve 6 each constituted by an air differential valve. . Normally, instrument air is supplied to the operating air pipe 23, and both the scrum inlet valve 5 and the scrum outlet valve 6 are closed by pneumatic pressure. When the instrument air in the pipe 23 is released, the scrum inlet valve 5 and the scrum outlet valve 6 are opened, and the control rod 1 is inserted into the core.

The coolant discharged from the pressure vessel is not directly discharged to the drain water tank 20, but is temporarily stored in a scrum discharge vessel 8 provided on the way. Scrum discharge container 8
Is connected to the drain water tank 20 by a drain pipe 25, and a drain valve 9 for opening and closing the communication is provided in the middle thereof. A pipe 26 communicates with the uppermost end of the scrum discharge container 8 (one is connected to, for example, the drain water tank 20), and the vent valve 10 is connected to the pipe 26. The drain valve 9 and the vent valve 10 are air-operated valves, and are connected to an operating air pipe 24. The pilot air valve 11 for drain valve for supplying and discharging instrument air is provided in the operating air pipe 24. When a scrum signal is input to the pilot solenoid valve 11, instrument air is supplied to the operating air pipe 24, the drain valve 9 and the vent valve 10 are closed, and cooling is performed through the driving water pipe 22 and the scram outlet valve 6. The material is stored in the scrum discharge container 8.

When the scrum reset signal enters the pilot valves 7, 11,
The scrum inlet valve 5 and the scrum outlet valve 6 close, and the drain valve 9 and the vent valve 10 open simultaneously. As a result, the coolant in the scrum discharge vessel 8 is drained by its own weight.
Drain water tank 20 is drained through 25.

As a conventional technique for simultaneously opening the drain valve and the vent valve when draining the coolant from the scrum discharge container,
There is JP-A-57-199992.

[Problems to be Solved by the Invention] The scram discharge vessel needs to secure a sufficient receiving space volume to receive the coolant (scram drainage) discharged from the reactor pressure vessel during scram. For this reason, the drain valve and the vent valve are opened during the operation of the reactor, and the scrum discharge container is always kept in an empty normal state. However, the reactor coolant discharged from the pressure vessel contains sludge, and when the coolant is discharged to the scram discharge vessel and drained to the drain water tank, the sludge accumulates in the scram discharge vessel or drains. There is a possibility that it may adhere to the inside of the pipe and cause clogging. With such sludge buildup,
There is a concern that the amount of scrum drainage that can actually be received in the scrum discharge vessel will be reduced and the scrum function will be reduced. In addition, if sludge adheres to the drain pipe and becomes clogged, rapid drain cannot be performed, re-scram operation becomes impossible, and furthermore, operation operation time cannot be reduced. Further, since such sludge has a high radiation dose, the radiation dose around the drain pipe, which is a scrum discharge container, is large and dangerous. Therefore, if the sludge can be discharged together with the drain from the scrum discharge container to the drain water tank, the above-mentioned problems can be solved.However, the conventional drain discharge method, that is, the drain valve and the vent valve are used. In the method of opening and draining at the same time, since the drainage is performed only by the weight of the coolant in the scrum discharge container, sludge cannot be discharged together.
In addition, the scrum action does not happen so often,
This is a rare operation. For this reason, in order to maintain the scrum discharge container, it is better to be able to discharge the sludge at the time of periodic inspection, but in the past, no consideration was given to such a situation in the past. is there.

It is an object of the present invention to provide a control rod drive hydraulic system capable of discharging sludge accumulated in a scrum discharge container and sludge attached to a drain pipe at the time of periodic inspection.

[Means for Solving the Problems] The above object is to provide a pressurizing means for applying pressure to the scrum discharge container during a periodic inspection, and a control means for opening the vent valve a predetermined time after opening the drain valve. This is achieved by providing

[Operation] Before the coolant flows into the scrum discharge container, air is contained in the scrum discharge container. This air does not have an outlet because the vent valve is closed at the time of scram, and is compressed in the scrum discharge container as the coolant flows into the scrum discharge container, and finally the scrum discharge container is filled with the coolant, 70 kg of the same pressure as the pressure in the pressure vessel
/ cm ² pressure is reached. Using the pressure of the compressed air, the coolant is drained from the scrum discharge container. In order to utilize the pressure of the compressed air, the drain valve is opened prior to opening the vent valve (the compressed air escapes when the vent valve is opened). Thereby, drainage is performed vigorously, and sludge attached to the scrum discharge container and the drain pipe is also discharged together.

At the time of the periodic inspection, sludge and the like can be removed at the same time by applying pressure to the coolant in the scrum discharge container by the pressurizing means and draining the coolant at the same pressure.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a control rod drive hydraulic system according to one embodiment of the present invention. Only the components different from the conventional control rod drive hydraulic system described with reference to FIG. 3 will be described.

The control rod drive hydraulic system in this embodiment is provided with a pilot solenoid valve 12 that opens and closes a vent valve 10 that is also an air-operated valve and a pilot solenoid valve 12 that opens and closes a drain valve 9 that is an air-operated valve. , This pilot solenoid valve
The configuration is such that a scrum signal, which is a control signal of 12, is supplied to the pilot solenoid valve 12 through a delay circuit 13.

At the time of scrum, a scrum signal is sent to the pilot solenoid valve 7,
11 and the delay circuit 13. As a result, the scram inlet valve 5 and the scram outlet valve 6 are opened, the control rod 1 is inserted into the core, the drain valve 9 and the vent valve 10 are closed, and the reactor discharged from the reactor pressure vessel is discharged. The coolant starts to be received by the scrum discharge vessel 8. The amount of coolant discharged by inserting the control rod 1 into the core in the entire stroke is about 1/4 of the volume of the scrum discharge container 8. However, there is a leakage of the coolant from the seal portion inside the control rod drive mechanism, which flows into the scrum discharge container 8 (this continues unless the scrum outlet valve 6 is closed), and finally the scrum discharge container 8 Is filled with coolant. As the coolant flows into the scram discharge vessel 8, the air that has entered the vessel 8 before the scram is gradually compressed because the vent valve 10 is closed and there is no escape path, and finally the pressure in the pressure vessel And the same pressure.

When a signal for resetting the scrum is input, first, the pilot solenoid valve 7 closes the scrum inlet valve 5 and the scrum outlet valve 6. At the same time, the pilot solenoid valve 11 opens the drain valve 9. Thereby, the scrum discharge container 8
The compressed air inside expands, and the coolant in the scrum discharge container 8 is drained to the drain water tank 20 through the drain valve 9 and the drain pipe 25. At this time, sludge adhering to the inside of the container 8 and the drain pipe 25 is also discharged to the drain water tank 20 together. On the other hand, the delay circuit 13 that has received the scrum reset signal sends a control signal to the pilot solenoid valve 12 after the required time has elapsed, and the vent valve 10 is opened. At this time, since the pressure of the compressed air in the scrum discharge container 8 is almost equal to the external pressure, the force for pushing out the coolant is weakened. If the vent valve 10 is not opened as it is, the pressure of the air in the scrum discharge container 8 becomes negative relative to the external pressure, and conversely, the coolant is prevented from being drained. Therefore, at this time, by opening the vent valve 10, a passage for introducing air from the outside into the scrum discharge container 8 is secured, and the coolant is quickly drained to the drain water tank 20.

In the above-described embodiment, the delay circuit 13 is provided, and the vent valve 10 is opened after a predetermined time has elapsed from the input of the scrum reset signal. This is because the volume of the scrum discharge container 8 and the size of its drain hole are changed. For example, it is possible to calculate in advance how long after the start of draining the vent valve 10 should be opened. Instead of this delay circuit 13,
It goes without saying that a control device for detecting the pressure in the scrum discharge container 8 and opening the vent valve 10 when the detected pressure reaches a predetermined value may be provided.

In the above-described embodiment, sludge and the like are discharged in synchronization with the scram reset of the nuclear reactor plant, but the scram operation of the plant is rare in practice. Therefore, in order to remove sludge and maintain the plant, it is necessary to discharge sludge at the time of periodic inspection of the plant. Therefore, a control rod driving hydraulic system according to an embodiment capable of performing such an operation at the time of periodic inspection will be described with reference to FIG.

In the control rod drive hydraulic system according to the present embodiment, a pilot solenoid valve 12 is provided separately from the pilot solenoid valve 11, similarly to the embodiment of FIG. A nitrogen gas cylinder is used as a pressurizing means.
The cylinder 16 is connected to a pipe 26 via a manual valve 15 for gas filling and a check valve 14 for preventing backflow, and a pressure detector 17 for monitoring the pressure in the scrum discharge vessel 8 is connected to the pipe 26. The control circuit 13 'is configured to control the pilot solenoid valve 12 based on the detected pressure and an input signal (scram simulation signal).

At the time of the periodic inspection, first, a signal simulating a scrum signal is given to the pilot solenoid valves 11 and 12, and the drain valve 9 and the vent valve 10 are closed. Next, a certain amount of water is poured into the scrum discharge container 8 (however, it is not filled with water).
In this normal state, the gas pressure reducing valve 15 of the nitrogen gas cylinder 16 is opened, and high-pressure nitrogen gas is sealed in the scrum discharge container 8. This sealed gas simulates the compressed air of the first embodiment described above. After that, a signal for resetting the scrum simulation signal is input. Then, the drain valve 9 is opened immediately, and the injection water in the scrum discharge container 8 is drained by the nitrogen gas pressure, and the sludge is discharged to the drain water tank 20 at once with this drain water. With this discharge, the pressure in the scrum discharge container 8 decreases, but when the pressure drops to a certain predetermined pressure, the control device 13 ′ knows this from the detection signal of the pressure detector 17 and opens the vent valve 10.

The control device 13 'according to the present embodiment operates in the same manner as the first embodiment during plant operation. That is, when the coolant is drained from the scram discharge container 8 to the drain water tank 20, first, the drain valve is opened by the scrum reset signal, and when the pressure in the scrum discharge container 8 decreases to the predetermined pressure, the vent is released. The valve 10 is opened.

In the second embodiment, the vent valve is opened by detecting the pressure in the scrum discharge container. However, it goes without saying that the vent valve may be opened a predetermined time after the drain valve is opened. .

[Effects of the Invention] According to the present invention, since the sludge of the scrum discharge container and the drain pipe can be removed, clogging of the pipe can be avoided, and the scrum discharge container can be always kept in an empty normal state. The reliability of the container is improved. In other words, since water is prevented from staying in the scram discharge container, it is possible to secure a space for receiving drainage from the control drive mechanism during scram, and to avoid unnecessary generation of scrum due to a rise in the water level in the scrum discharge container. In addition, it is possible to prevent a decrease in operation efficiency of the plant.

Furthermore, the reactor coolant flows into the scram discharge vessel, and the sludge that flows in at that time has a high radiation dose and is dangerous, but in the present invention, this sludge is quickly discharged to an external drain water tank. As a result, the radiation dose around the drain pipe can be reduced, and the sludge can be easily treated.

Furthermore, since the drain time of the scrum discharge container is shortened, the plant operability is improved, for example, the operation time can be shortened and the re-scram operation can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control rod driving hydraulic system according to a first embodiment of the present invention, FIG. 2 is a configuration diagram of a control rod driving hydraulic system according to a second embodiment of the present invention, and FIG. It is a block diagram of a control rod drive hydraulic system. 1 ... control rod, 2 ... drive piston, 3 ... control rod drive mechanism,
4 ... Accumulator, 5 ... Scrum inlet valve, 6 ... Scrum outlet valve, 7 ... Scrum pilot solenoid valve, 8 ... Scrum discharge vessel, 9 ... Drain valve, 10 ... Vent valve, 11,12 ... Pilot solenoid valve, 13 ... Delay Circuit, 13 '... Control device, 14 ...
Check valve, 15: pressure reducing valve, 16: nitrogen gas cylinder, 17: pressure detector, 20: drain water tank.

Claims (1)

(57) [Claims] 1. A scram discharge vessel for temporarily receiving scram discharge water from a control rod drive mechanism of a boiling water reactor, a drain valve for draining waste water in the scrum discharge vessel to a drain water tank, and a drain valve A control rod drive hydraulic system including a vent valve that opens an air hole in the scrum discharge container to facilitate the drain operation, and pressurizing means for applying pressure to the scrum discharge container during periodic inspection; and A control device for opening the vent valve a predetermined time after the valve is opened.