JPH0650355B2 - Control rod drive mechanism - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a control rod drive mechanism (hereinafter referred to as CRD) of a boiling water reactor (hereinafter referred to as BWR).

[Technical background of the invention]

A conventional example will be described with reference to FIGS. 1 to 7. First
The figure is a vertical sectional view showing a schematic configuration of a BWR. Reference numeral 1 in the figure
Indicates a reactor pressure vessel, in which the reactor water 2 is stored, and the shroud 3 is erected at an inner circumferential side with a space. Inside the shroud 3, the upper and lower parts are supported by the upper lattice plate 4 and the core support plate 5, respectively, and the fuel assemblies 6 and the control rods (hereinafter referred to as CR) 7 of a reciprocal number are loaded to form the core 8. is doing. A shroud head 9 is installed on the upper end of the shroud 3, a steam separator 10 is installed above the shroud head 9, and a steam dryer (not shown) is installed above it.

Below the control rod 7, an electric control rod drive mechanism (hereinafter CR
11) is installed. The CRD 11 is a control rod drive mechanism housing (hereinafter referred to as a CRD housing) 12 fixed through the bottom wall of the reactor pressure vessel 1, and a control rod drive mechanism main body (hereinafter referred to as CRD housing) fixedly inserted into the CRD housing 12 from below. The main body) 13). Reference numeral 14 in the drawing denotes a control rod guide tube (hereinafter referred to as CR guide tube). The CRD 11 is used to insert and extract the CR 7 into the core 8 and fix the CR 7 at an appropriate position in the core 8 to control the core output.

Next, the configuration of the CRD 11 will be described in detail with reference to FIG. An outer tube 15 is housed on the inner peripheral side of the CRD housing 12, and a CRD main body flange 16 is integrally attached to the lower end of the outer tube 15. A cylinder tube 32 is accommodated on the inner peripheral side of the outer tube 15, and a hollow hollow piston 17 is accommodated on the inner peripheral side of the cylinder tube 16 so as to be vertically movable. A connecting member 18 is attached to the upper end of the hollow piston 17, and is connected to the CR 7 via the connecting member 18. A drive piston 19 having a large diameter is integrally attached to the lower end of the hollow piston 17.

A ball screw shaft 20 is penetratingly arranged in the hollow piston 17, and a rotational driving force is transmitted to the ball screw shaft 20 from a motor 22 via a shaft 21. A ball nut 26 is screwed onto the ball screw shaft 20.
The shaft 21 is housed in a spool piece 23 fixed to the CRD main body flange 16 from below, and the electric motor 22 is fixed below the spool piece 23. A seal member 25 is mounted between the shaft 21 and the spool piece 23 via a seal box 24.

In the above configuration, CR7 is inserted into CRD 11 at a relatively low speed in order to maintain and maintain the reactor output in a predetermined state.
There are an operation of pulling out (hereinafter referred to as a shim operation) and an operation of inserting CR7 at a high speed to make an emergency stop of the reactor in an emergency (hereinafter referred to as a scrum operation). The shim operation drives the electric motor 22 to rotate the ball screw shaft 20 via the shaft 21. The rotation of the ball screw shaft 20 raises the ball nut 26, and the drive piston 1
The hollow piston 17 is raised via 9. As a result, CR7 is inserted at a low speed and a predetermined amount. On the contrary, when pulling out CR7, the electric motor 22 is rotated in the reverse direction. The reverse rotation of the electric motor 22 also reversely rotates the ball screw shaft 20 to lower the ball nut 26 and simultaneously lower the hollow piston 17. As a result, the CR 7 is pulled out at a low speed by a predetermined amount.

Also, the scrum operation is performed by the flange 12 of the CRD housing
High-pressure water is supplied from a high-pressure water injection mechanism (not shown) through the high-pressure water supply port 27 formed in the A and CRD main body flanges 16, and the high pressure acts on the hollow piston 17. Due to the action of this high pressure, the hollow piston 17 separates from the ball nut 26 and rises at high speed to insert the CR 7 into the core 8 at high speed. This will make an emergency shutdown of the reactor.

Next, the work of inserting the CRD main body 13 into the CRD housing 12 and attaching it will be described. First, the CR with the spool piece 23 and the electric motor 22 separated as shown in FIG.
Insert the D body 13 into the CRD housing 12 from below.
Then, through the connecting member 18 at the upper end of the hollow piston 17, C
Connect with R7. That is, as shown in FIGS. 4 and 5, the connecting member 18 is provided with four plates 18A, while a hole 28 is formed at the lower end of the CR7. On the inner peripheral surface of the hole 28, four recesses 28A that fit into the four plates 18A are formed. The CRD main body 13 is inserted into the CRD housing 12 in a state in which the four plates 18A are fitted in the recesses 28A so as to be fitted with each other. Then, even after the four plates 18A of the connecting member 18 are completely inserted into the holes 28, the CRD main body 13 is inserted into the CRD housing 12 until the CR7 is slightly lifted in order to further ensure the inserted state. . At that time, in order to protect the seal ring 29 of the CRD main body flange 16, the insertion of the CRD main body 13 is stopped with a gap provided between the flange 12A of the CRD housing 12 and the CRD main body flange 16. At this time C
The upper surface of the upper guide 30 of the RD body 13 is the CRD housing 1
The Belleville spring row 31 for a buffer, which is in contact with the inner surface of the upper end of 2 and is mounted between the upper guide 30 and the cylinder tube 16, is in a slightly compressed state. Next is the sixth
As shown in FIG. 7 and FIG. 7, the CRD body 13 is rotated by 45 ° to engage the connecting member 18 and the hole 28, and
And CR7 are connected. And after connecting, CRD body 7
Is further inserted into the CRD housing 12, then the flange 12A and the flange 16 are fastened by mounting bolts (not shown) to fix the CRD main body 7 to the CRD housing 12, and then the spool piece 23 and the electric motor 22 are sequentially mounted.

[Problems of background technology]

According to the above configuration, when the CRD main body 13 is inserted and fixed in the CRD housing 12, even after the four plates 18A of the connecting member 18 are completely inserted into the holes 28 of the CR7 as described above, the insertion state is further improved. The CRD main body 13 is further inserted into the CRD housing 12 until the CR7 is slightly lifted in order to ensure reliability. Therefore CR7 and control rod guide tube 14
The sealing function due to is temporarily impaired, and the reactor water 2 leaks between the CR 7 and the control rod guide pipe 14. Leaked reactor water 2
Is the outer tube 1 via the upper surface of the upper guide 30.
5 and the CRD housing 12, and flows out between the flange 12A of the CRD housing 12 and the CRD main body flange 16 at a pressure of about 3 kg / cm ² . Therefore, workability is deteriorated and it takes a long time to work, and various devices must be designed to be waterproof, and there is a concern about contamination of the work site and exposure of workers.

[Object of the Invention]

The present invention has been made based on the above points, and its object is to improve the workability and shorten the working time by minimizing the leakage of the reactor water when mounting the CRD body in the CRD housing. Another object of the present invention is to provide a control rod drive mechanism capable of reducing the exposure of workers by simplifying the equipment by eliminating the need to waterproof various devices.

[Outline of Invention]

That is, the control rod drive mechanism according to the present invention includes a control rod drive mechanism housing having a flange portion at the lower end portion that is fixedly penetrated through the bottom wall of the reactor pressure vessel, and is housed in the control rod drive mechanism housing from below in a removable manner. A control rod drive mechanism main body, a control rod drive mechanism main body flange which is provided at a lower end portion of the control rod drive mechanism main body and is bolted to the flange portion of the control rod drive mechanism housing, and the control rod drive mechanism main body A hollow piston housed in the hollow piston, a connecting member provided at the upper end of the hollow piston and connected to the control rod, a drive mechanism for vertically driving the hollow piston, and a flange portion of the control rod drive mechanism housing. A seal ring provided in a liquid-tight manner between the control rod drive mechanism body flange and a seal mechanism provided on an outer peripheral surface of the control rod drive mechanism body. The seal mechanism includes the control mechanism when the distance from the upper surface of the drive control rod drive mechanism body flange is 1, and the control mechanism is used when the control rod drive mechanism body is inserted and fixed in the control rod drive mechanism housing. The rod is larger than the lifted distance from the control rod guide tube.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 8 and 9. The same parts as those of the prior art are designated by the same reference numerals and the description thereof is omitted. In the CRD according to the present embodiment, the outer diameter of the lower portion of the outer tube 51 is made larger than that of the conventional outer tube, and the large diameter portion and the CRD housing 12 are provided.
The seal mechanism 52 is provided between and. Distance l between the sealing mechanism 52 and the upper surface of the CRD body flange 16
Is C when installing the CRD main body 13 in the CRD housing 12.
R7 is larger than the distance lifted from the CR guide tube 14. The sealing mechanism 52 includes an annular groove 53 formed on the outer tube 51 side and an annular groove 53.
And a seal ring 54 attached to the.
That is, when the CRD body 13 is mounted in the CRD housing 12, the seal mechanism 52 is inserted into the CRD housing 12 before the CR7 is lifted from the CR guide tube 14, so that the space between the outer tube 51 and the CRD housing 12 is made. Even if the reactor water 2 leaks from between the CR 7 and the CR guide pipe 14, the reactor water 2 is prevented from leaking to the outside.

According to the above configuration, when the CRD main body 13 is inserted and fixed in the CRD housing 12, the axis of the CRD main body 13 is first aligned with the axis of the CRD housing 12 and the four plates 18A of the connecting member 18 are Recess 28A of hole 28 of CR7
Phase with. After that, as shown in Fig. 9, CRD
The main body 13 is inserted into the CRD housing 12, and the connecting member 18 is inserted into the hole 28 while fitting the four plates 18A into the recesses 28A. Then, in order to more securely insert the connecting member 18 into the hole 28, the CRD main body 13 is further inserted in a state of lifting the CR 7 from the CR guide tube 14. Next, rotate the CRD body 13 by 45 ° and connect the connecting member 18
And the hole 28 are engaged. At that time, since the CR 7 separates from the CR guide pipe 14, the reactor water 2 leaks from between the CR 7 and the CR guide pipe 14. However, in the case of the present embodiment, the seal mechanism 52 is provided between the outer tube 51 and the CRD housing 12, and the seal mechanism 52 is surely placed in the CRD housing 12 before the CR7 is separated from the CR guide tube 14. Since it is inserted, the seal mechanism 52 can reliably prevent the reactor water 2 from flowing out of the CRD housing 12. After that, the CRD main body 13 is fixed to the CRD housing 12 with a mounting bolt, and the spool piece 23 and the electric motor 22 are sequentially mounted.

That is, between the outer tube 51 and the CRD housing 12, before the CR7 is lifted from the CR guide tube 14 when the CRD body 13 is mounted in the CRD housing 12.
Since the seal mechanism 52 is provided at a position where it can be reliably inserted into the CRD housing 12, the CR7 separates from the CR guide tube 14 when the CRD main body 13 is mounted in the CRD housing 12, and the reactor water flows from that interval. Sealing mechanism 5 even if 2 leaks
2 can reliably prevent leakage of the reactor water 2 to the outside of the CRD housing 12. Therefore, the workability does not deteriorate due to leakage of the reactor water 2 and the work time is not prolonged as in the conventional case. The workability is improved, the work time is shortened, and the environmental pollution at the work site is prevented. Can be achieved. In addition, it is not necessary to waterproof various devices, and the equipment can be simplified.

In the above-described embodiment, the outer tube 51 side is provided with the annular groove and the seal ring is attached, but the present invention is not limited to this, and for example, as shown in FIG. 10, the CRD housing 12 side is provided with the annular groove 53A, A configuration in which the seal ring 54A is attached to this annular groove may be employed, and the same effect as that of the above-described embodiment can be obtained.

[Advantages of the Invention] As described in detail above, the control rod drive mechanism according to the present invention includes a control rod drive mechanism housing having a flange portion at the lower end portion which is fixed through the bottom wall of the reactor pressure vessel, and the control rod drive mechanism. A control rod drive mechanism body housed in the housing so that it can be inserted and removed from below, and a control rod drive mechanism body provided at the lower end of the control rod drive mechanism body and bolted to the flange portion of the control rod drive mechanism housing. A flange, a hollow piston housed in the control rod drive mechanism main body, a connecting member provided at the upper end of the hollow piston and connected to the control rod, and a drive mechanism for driving the hollow piston in the vertical direction, A seal ring provided in a liquid-tight manner between a flange portion of the control rod drive mechanism housing and the control rod drive mechanism body flange, and an outer peripheral surface of the control rod drive mechanism body. And a seal mechanism provided in the control rod drive mechanism main body, wherein the seal mechanism has a distance from the upper surface of the control rod drive mechanism main body flange of 1, and the control rod drive mechanism main body has the control rod drive mechanism housing. The length of the control rod is larger than the distance that the control rod can be lifted from the control rod guide tube when it is inserted and fixed therein.

Therefore, it is possible to prevent or minimize leakage of reactor water when the control rod drive mechanism main body is inserted and fixed in the control rod drive mechanism housing. As a result, workability is improved, work time is shortened, and exposure of workers is reduced. And the simplification of the equipment can be achieved.

[Brief description of drawings]

1 to 7 are views showing a conventional example, FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a boiling water reactor, FIG. 2 is a vertical cross-sectional view of a control rod drive mechanism, and FIG. FIG. 4 is a longitudinal sectional view showing a state in which the control rod drive mechanism main body is inserted and fixed in the control rod drive mechanism housing, FIG. 4 is a sectional view showing a state in which the connecting member is inserted into the control rod lower hole, and FIG. 6 is a cross-sectional view taken along line V-V of FIG. 6, and FIG. 6 is a cross-sectional view showing a state in which the connecting member is inserted into the lower hole of the control rod and rotated by 45 ° to engage the two, and FIG. 7 is taken along line VII-VII of FIG. Sectional views, FIGS. 8 and 9 are views showing an embodiment of the present invention. FIG. 8 is a longitudinal sectional view of a control rod drive mechanism, and FIG. 9 is a control rod drive mechanism main body with a control rod drive mechanism housing. Fig. 10 is a longitudinal sectional view showing a state of being inserted and fixed in the inside.
The figure is a longitudinal sectional view of a control rod drive mechanism showing another embodiment. 1 ... Reactor pressure vessel, 7 ... Control rod, 11 ... Control rod drive mechanism, 12 ... Control rod drive mechanism housing, 13 ...
… Control rod drive mechanism body, 17… Hollow piston, 18…
... connecting member, 20 ... ball screw shaft, 21 ... shaft, 22 ... electric motor, 26 ... ball nut, 51 ...
Outer tube, 52 ... Sealing mechanism.

Claims (1)

[Claims] 1. A control rod drive mechanism housing having a flange portion at a lower end thereof which is fixedly penetrated through a bottom wall of a reactor pressure vessel,
A control rod drive mechanism main body housed in the control rod drive mechanism housing so as to be insertable and removable from below, and bolted to a flange portion of the control rod drive mechanism housing provided at a lower end portion of the control rod drive mechanism main body. A control rod drive mechanism main body flange, a hollow piston accommodated in the control rod drive mechanism main body, a connecting member provided at the upper end of the hollow piston and connected to the control rod, and the hollow piston driven in the vertical direction. Drive mechanism, a seal ring provided in a liquid-tight manner between the flange portion of the control rod drive mechanism housing and the control rod drive mechanism body flange, and a seal provided on the outer peripheral surface of the control rod drive mechanism body. Equipped with a mechanism,
The distance of the sealing mechanism from the upper surface of the control rod drive mechanism main body flange is controlled when the control rod drive mechanism main body is inserted into the control rod drive mechanism housing and the connecting member is connected to the control rod. A control rod drive device characterized in that the rod is set to be longer than a distance to be lifted from the control rod guide tube.