JPH04164292A - Hydraulic device for control rod drive - Google Patents

Abstract

PURPOSE:To prevent an excessive pressure rise and prevent the occurrence of damage to each part by providing a bypass flow passage and a pressure release means in the valve box of a gate valve at a connection line between the upper cylinder chamber of a control rod drive mechanism and a scram discharge facility. CONSTITUTION:Normally, a ball 45 as a pressure release means is kept in contact with a seat section 51 under pressure by a spring 44, thereby interrupting a bypass flow passage 50. If a control rod drive hydraulic device 1 scrams with the main flow passage thereof closed due to the erroneous operation of gate valves 41 and 42, a section continuous to the upper cylinder chamber of a control rod drive mechanism, or the upstream port 48 of the valves 41 and 42 gives higher pressure. In addition, when the pressure becomes equal to or above the predetermined level, the ball 45 parts from the seat section 51 against the force of the spring 44, thereby enabling the pressure of the port 48 to be released to a downstream port 49 via the bypass flow passage 50. According to the aforesaid construction, an excessive pressure rise is prevented, even if the device 1 scrams with the gate valves 41 and 42 closed, and the damage of each section can be avoided. As a result, the safety and soundness of plant operation can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control rod drive hydraulic device used for operating a control rod drive mechanism in a boiling water nuclear reactor.

(Prior Art) Generally, the output of a boiling water reactor is controlled by controlling the flow rate of coolant and by inserting or withdrawing control rods.

In addition, in the event of a reactor emergency, control rods will be inserted (scram) to shut down the reactor.

Such insertion and withdrawal of the control rods is performed by a control rod drive mechanism, and this control rod drive mechanism is driven by supplying high pressure drive water from a control rod drive hydraulic device.

The above-mentioned control rod drive mechanisms are installed in large numbers at the bottom of the reactor in correspondence with the control rods that are inserted into and removed from the reactor core, and each control rod drive mechanism has a control rod drive mechanism that supplies driving water. One hydraulic device is installed at each location.

A conventional control rod drive hydraulic system is constructed as shown in FIG. In this control rod drive hydraulic system 1, a control rod drive mechanism 4 is inserted into a housing 3 attached to a lower head plate 2 of a reactor pressure vessel, and a lower cylinder chamber 5 of this control rod drive mechanism 4 is provided with a control rod drive mechanism 4. An insertion pipe 6 is connected.

One end of a pipe 9 provided with an air-operated valve 8 is connected to the insertion pipe 6 via a gate valve 7, and the other end of this pipe 9 is connected to an accumulator device 10.

This accumulator device 10 includes an accumulator 11 that stores the amount of water necessary to drive the control rod drive mechanism 4 during a scram, and an accumulator 11 that stores the amount of water necessary to drive the control rod drive mechanism 4 during a scram, and the water in the accumulator 1 that is necessary to insert the control rod 13 within a specified time. It has a nitrogen gas container 12 that stores nitrogen gas under pressure and volume.

Further, a drawing plumber 5 is connected to the upper cylinder chamber ``-4'' of the control rod drive mechanism 4. One end of a connecting plumber 8 equipped with air-operated valves 1-7 is connected to the extraction plumber 5 via a gate valve 16, and the other end of the connecting plumber 8 is connected to a gate valve 19 and a scram discharge pipe. It is connected to scram discharge equipment 20 via 21. The upper cylinder chamber 14 and the lower cylinder chamber 5 of the control rod drive mechanism 4 are partitioned by a drive piston 34, and the drive piston 34 is connected to the control rod 3.

FIG. 5 shows the structure of the gate valves 7, 16 and 19,
These gate valves include a valve box 23 having a valve seat 22, a valve cover 25 fastened to the valve box 23 with a bolt 24, and a gasket 26 interposed between the valve box 23 and the valve cover 25. Also,
The valve stem 27 is built into the valve cover 25, and the valve stem 27 and the valve cover 2
A ground 28 is provided between the bolts 29 and nuts 3.
The gland 28 is tightened by the gland presser 31 which is tightened at zero. Further, the upper end of the valve stem 27 has a valve stem 2
It has a handle 32 for raising and lowering the valve 7, and a valve body 33 at the lower end that seats on the valve seat 22 and closes the flow path when the valve stem 27 is lowered.

In the above configuration, the control rod drive hydraulic system 1 is operated by the gate valve 7 during normal operation of the nuclear power plant. ↑6 and 19
is fully open, and air-operated valve 8.1-7 is fully closed. If air-operated valve 8 suddenly opens during scram, nitrogen gas container 1
Water in the accumulator 11 is drained from the pipe 9 by the pressurized nitrogen gas in the pipe 9. It passes through the insertion pipe 6 and is rapidly supplied as driving water to the lower cylinder chamber 5 of the control rod drive mechanism 4. At the same time, the air-operated valve 17 also suddenly opens, and the return water from the upper cylinder chamber 14 of the control rod drive mechanism 4 is drained to the connecting plumber 8. It passes through the scram discharge piping 21 and is discharged to the scram discharge equipment 20.

Furthermore, when disassembling and inspecting the control rod drive hydraulic system 1, the gate valves 7, 16, and 19 are fully closed so that it can be isolated from other systems.

(Problem to be Solved by the Invention) If the conventional control rod drive hydraulic system 1 is scrammed with the gate valves 16 and 19 closed due to malfunction etc., the water in the upper cylinder chamber 14 of the control rod drive mechanism 4 will not be discharged. , because the scram, that is, the emergency insertion of the control rod 13 is not performed, and the area of the upper surface of the drive piston 34 is about 1/3 of the area of the lower surface, the pressure in the upper cylinder chamber 14 is about three times that of the lower cylinder chamber 5. There was a risk that the control rod drive mechanism 4 would be damaged.

The present invention was made in consideration of the above circumstances, and enables scramming even when scramming is performed with the gate valve closed.
Another object of the present invention is to provide a control rod drive hydraulic device that can prevent damage to the control rod drive mechanism.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the control rod drive hydraulic system according to the present invention, the upper cylinder chamber of the control rod drive mechanism that rapidly inserts the control rods during reactor scram is provided. A connection pipe that connects the extraction pipe connected to the scram discharge equipment and the scram discharge pipe connected to the scram discharge equipment, a first gate valve interposed between the connection pipe and the extraction pipe, and the above-mentioned connection pipe. In the control rod drive hydraulic device comprising a second gate valve interposed between the piping and the scram discharge piping, the first.
A bypass flow path is provided in both valve boxes of the second gate valve, and a pressure release means is provided on the bypass flow path.

(Function) In the present invention having the above-mentioned configuration, the first. Even if a scram occurs with the second gate valve closed due to malfunction, if the pressure in the part connected to the upper cylinder chamber exceeds a predetermined value, the pressure release means will operate and the pressure will be released through the bypass flow path. , it becomes possible to perform a scram and prevent damage to the control rod drive mechanism.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic system diagram showing an embodiment of the control rod drive hydraulic device according to the present invention, and FIG. 2 is an enlarged view of the main parts thereof. Note that the same reference numerals as in FIGS. 4 and 5 will be used to describe parts that are the same as or correspond to the conventional configuration.

In FIG. 1, the control rod drive hydraulic system 1 has an insertion pipe 6
and a control rod drive mechanism 4 via a withdrawal plumber 5, and an insertion pipe 6 is connected to a lower cylinder chamber 5 of the control rod drive mechanism 4. One end of a pipe 9 provided with an air-operated valve 8 is connected to the insertion pipe 6 via a gate valve 7, and the other end of this pipe 9 is connected to an accumulator device 10.

This accumulator device 10 includes an accumulator 11 that stores the amount of water necessary to drive the control rod drive mechanism 4 during a scram, and this accumulator. It has a nitrogen gas container 12 that stores nitrogen gas at the pressure and capacity necessary to insert the control rod 13 into the water in the water within a specified time.

Further, a drawing pipe 15 is connected to the upper cylinder chamber 14 of the control rod drive mechanism 4, and a connecting pipe 15 is provided with an air-operated valve 17 via a first gate valve 41. One end of the connecting plumber 8 is connected, and the other end of the connecting plumber 8 is connected via a second gate valve 42 to a scram exhaust pipe 21 that is connected to scram exhaust equipment.

The upper cylinder chamber 4 and the lower cylinder chamber 5 of the control rod drive mechanism 4 are separated by a drive piston 34, and the drive piston 34 is connected to the control rod 13.

FIG. 2 shows the structure of the gate valves 41 and 42 in this embodiment. 46, the valve cover 25 is fastened to the valve box 46 by the port 24, and the gasket 26 is interposed between the valve box 46 and the valve cover 25. Further, a valve stem 27 is built into the valve cover 25, and a gland 28 is provided between the valve stem 27 and the valve cover 25, and the gland 28 is tightened by a gland presser 31 fastened with a bolt 29 and a nut 3o. Further, the upper end of the valve stem 27 has a handle 32 that rotates to move the valve stem 27 up and down.
The lower end has a valve body 33 that seats on the valve seat 22 and closes the flow path when the valve stem 27 is lowered.

The valve box 46 has an upstream port 48 and a downstream port 49.
A bypass flow path 50 is provided, and a seat portion 51 is provided on the bypass flow path 50, and a ball 45 is pressed against the seat portion 51 by a spring 44 constituting a check valve. In this embodiment, the spring 44 and the ball 45 constitute a pressure release means. A plug 43 is attached to the valve box 46 through a seal 47 at the insertion opening for the spring 44 and ball 45, and this plug 43 receives the reaction force of the spring 44 pressing against the ball 45 of the check valve. ing.

In the gate valve 41, the upstream port 48 is connected to the extraction pipe 1.
5, and the downstream port 49 is connected to the connection pipe 18. Further, in the gate valve 41, the upstream port 48 is connected to the connection pipe 18, and the downstream port 49 is connected to the connecting pipe 18.
is connected to the scram discharge pipe 21.

Next, the operation of this embodiment will be explained.

Under normal conditions, the ball 45 is moved to the seat portion 5 by the spring 44.
1, and the bypass flow path 50 is blocked. If a scram occurs with the main flow path of the gate valve 41 or 42 closed, the pressure in the upstream port 48 will increase. When this pressure exceeds a predetermined pressure,
The ball 45 is separated from the seat portion 51 against the urging force of the spring 44. This opens the bypass channel 50 and allows water to escape to the downstream port 49.

That is, the control rod drive hydraulic system 1 has gate valves 41 and 4.
Even if there is a scram with the valve closed due to a malfunction in the upper cylinder chamber 1 of the control rod drive mechanism 4,
4, the ball 45 resists the biasing force of the spring 44 and moves toward the seat portion 51.
upstream port 48 of gate valves 41 and 42
The pressure can be released to the downstream port 49 through the bypass passage 50.

FIGS. 3(A) and 3(B) show another embodiment of the present invention, and the same or corresponding parts as in the first embodiment are given the same reference numerals and will be described. In this embodiment, instead of the ball 45 constituting the pressure release means, a valve body 52 with a chevron-shaped cross section is attached to the tip of the spring 44, and a valve body 53 has a tapered shape on the bypass passage 50. A seat portion 54 is formed. Thereby, the valve body 52 is brought into pressure contact with the seat portion 54 by the urging force of the spring 44.

Therefore, by providing the valve body 52 and the seat portion 54, the same function as in the embodiment described above can be obtained.

The other configurations and operations are the same as those in the first embodiment, so their explanation will be omitted.

〔Effect of the invention〕

As explained above, according to the present invention, in the unlikely event that the first cylinder is installed on the connecting pipe connecting the upper cylinder chamber of the control rod drive mechanism and the scram exhaust equipment. Even if a scram occurs with the second gate valve closed, if the pressure in the part connected to the upper cylinder chamber of the control rod drive mechanism exceeds a predetermined pressure, the pressure release means will be activated and the pressure will be reduced. It is possible to prevent the amount from rising too much. As a result, damage to various parts can be prevented, and the safety and soundness of plant operation can be improved.

-1,200-

[Brief explanation of drawings]

Fig. 1 is a schematic system diagram showing one embodiment of the control rod drive hydraulic system according to the present invention, Fig. 2 is a sectional view showing the gate valve of Fig. 1, and Figs. 3 (A) and (B) are A sectional view showing a gate valve in another embodiment of the control rod drive hydraulic device according to the invention, a sectional view showing its pressure release means, FIG. 4 is a schematic system diagram showing a conventional control rod drive hydraulic device, and FIG. 5 is a sectional view showing the gate valve of FIG. 4. FIG. DESCRIPTION OF SYMBOLS 1-... Control rod drive hydraulic device, 4... Control rod drive mechanism, 10... Accumulator device, 13... Control rod, 14... Upper cylinder chamber, 15... Piping for extraction, 18
... Connection piping, 21 ... Scram discharge piping, 41
...Gate valve (first gate valve), 42...Gate valve (second gate valve), 44...Spring (pressure release means)
, 45... Ball (pressure release means), 50... Bypass channel.

Claims (1)

[Claims] A connection pipe that connects a withdrawal pipe connected to the upper cylinder chamber of the control rod drive mechanism that rapidly inserts control rods during reactor scram and a scram discharge pipe connected to the scram discharge equipment, and a connection pipe and a withdrawal pipe connected to the scram discharge equipment. A control rod drive hydraulic system comprising a first gate valve interposed between the first gate valve and the scram discharge pipe, and a second gate valve interposed between the connection pipe and the scram discharge pipe. A control rod drive hydraulic device characterized in that a bypass flow path is provided in both valve boxes of the second gate valve, and a pressure release means is provided on the bypass flow path.