JPH0328795A - Hydraulic control rod driving device - Google Patents

Abstract

PURPOSE:To prevent the inner peripheral surface of a cylinder fromdamaging by providing a driving force generation part which is arranged in the cylinder while a gap is left and an alignment part which aligns a driving shaft which the cylinder axis. CONSTITUTION:A foreign matter acquisition part 22 on the downstream side of the driving force generation part 21 is equipped with an annular soft packing 22b for passing a cooling material containing foreign matter through a fluid passage 22a as shown by an arrow 25, a straightener 22 provided at the exit of the passage 22a, etc. The alignment part 20 has plural by-pass passages 20a and 20b formed in the piston 15c of the driving shaft 15b. The entrance 20a-1 of the flow passage 20a is formed on the upstream side of the generation part 21, the exit 20a - 2 is formed on the downstream side of the generation part 21, and the entrance 20b-1 and exit 20b of the passage 20b are formed on the downstream side of the generation part 21. The exit 20a 2 of the flow passage 20a forms a recessed part and the flow passage 20a is arranged at an equal interval in the circumferential direction at a position radially outside the flow passage 20b. Similarly, the flow passage 20b which is arranged at an equal interval is also arranged angularly eccentrically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of Industry-L] The present invention relates to a drive device for raising and lowering control rods such as water exclusion rods used in nuclear reactors using water pressure.

BACKGROUND ART For example, in a pressurized water nuclear reactor, various control rods are used to control the reactor. Since it is necessary to finely adjust the amount of power control rods inserted into the fuel assemblies that make up the reactor core, the drive device for these control rods is of a continuously variable type that can be finely adjusted.

However, the drive devices for other control systems, such as water exclusion rods, do not need to be of the continuously variable type; instead, they can be driven in two stages by hydraulic pressure to either fully insert or completely withdraw the control rods from the fuel assembly. are commonly used. An example of such a control rod drive device is disclosed in Japanese Patent Publication No. 63-45560.

The hydraulic drive device disclosed in the above publication is installed upright on the lid of the reactor vessel like other continuously variable drive devices, and is connected to the pressure housing outside the reactor vessel and the pressure Equipped with a drive shaft housed in the housing,
The upper end of the control rod is connected to the lower end of the drive shaft via an openable/closable gripper. The pressure housing is connected to a hydraulic drive system including a valve, and the upper end of the drive shaft is a piston with a latching mechanism. Typically, by opening a valve and directing the coolant in the pressure housing to a drain tank outside the reactor vessel, the pressure differential across the piston is increased and the drive shaft is held in position within the pressure housing, thus controlling the By holding the rods in a fully withdrawn position from the fuel assembly and closing the valve to substantially eliminate the pressure differential across the piston section, the drive shaft and control rods are pulled into the fuel assembly by their gravitational force. It is designed to be lowered to the fully inserted position.

On the other hand, as is well known, when replacing a spent fuel assembly in a nuclear reactor with a new fuel assembly, the lid of the reactor vessel must be removed. However, since not only the control rods for output control but also the water exclusion rods are connected to the drive shaft as described above, from the viewpoint of workability, the water exclusion rods and output control rods must be connected before removing the reactor vessel lid. It is advantageous to disconnect the control rods and their drive shafts.

A typical coupling for disconnecting a power control rod from its drive shaft is disclosed in U.S. Pat. No. 4,147,589. In the joint disclosed in this patent specification, as mentioned in Japanese Patent Publication No. 63-45560, the drive shaft is first lowered and then raised by water pressure to engage and disengage the drive shaft from the control rod. It is carried out.

[Problems to be Solved by the Invention] However, as schematically shown in FIG. 7, in the conventional hydraulically driven control rod drive device, the cylinder 2 is installed inside the housing 1 attached to the reactor vessel M3. , the piston part 4 of the drive shaft 5 having the piston ring 4a slides along the cylinder 2 due to the differential pressure generated by the vent 1 or drainage from the hem 1 to system 6 communicating with the upper housing part. Driven. Therefore, if a foreign object such as metal chips in the coolant gets caught between the piston ring 4a and the inner surface of the cylinder 2, the surfaces of both will be damaged, and in the worst case, the piston 1 will be damaged. It may become stuck and not move.

Therefore, an object of the present invention is to provide a hydraulic control rod drive device that can avoid damage that would cause the piston to stick even if foreign matter is mixed in the coolant. .

[Means for Solving the Problems] To this end, the present invention provides a hydraulic system comprising a fluid cylinder communicating with a vent system and a drive shaft having a piston portion movably disposed within the fluid cylinder. The control rod drive device includes a driving force generating section having a diameter that creates a predetermined gap between the piston section of the drive shaft and the inner circumferential surface of the fluid cylinder, and the driving force generating section with respect to the fluid flow direction. a foreign matter capturing section provided on the upstream side of the foreign matter capturing section and having a fluid passage therein; and a bypass located on the downstream side of the foreign matter capturing section guiding a part of the fluid exiting the foreign matter capturing section to the outer peripheral surface on the downstream side. The centering section has a flow path.

[Operation] The coolant first passes through the foreign matter trapping section. A large foreign object ↓j is captured in this foreign object capturing section and does not reach the driving force generating section.

4. If the coolant contains small foreign matter, the foreign matter passes through the foreign matter trapping section and reaches the driving force generation section. However, since there is a gap between the driving force generating part and the inner peripheral surface of the cylinder, small foreign objects can pass through the driving force generating part without getting caught between the driving force generating part and the cylinder, and are ejected from the vent system. Ru.

A part of the fluid that has exited the foreign matter capturing part flows along the outer peripheral surface of the driving force generating part, but the remaining part enters a bypass flow path formed inside the drive shaft and exits from the bypass flow path. , used for centering action.

[Embodiments] Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts.

FIG. 2 schematically shows, in cross section, a part of a pressurized water reactor 10 equipped with a preferred embodiment of the hydraulic control rod drive device according to the present invention. A substantially hemispherical lid body l is attached to the top of l1 by a plurality of bolts 12.
3 is removably attached. At the top of the lid 13, there are a plurality of continuously variable drive devices 14 for driving control rods (not shown) for controlling the output of the reactor core.
A plurality of hydraulic actuators according to the present invention for driving a two-stage action control forest, such as the well-known water displacement rods 16, into fully inserted and fully withdrawn positions relative to the fuel assemblies (not shown) comprising the core. A control rod drive device 15 is inserted and removed through the lid 13.

Each hydraulic control rod drive 15 includes a substantially cylindrical pressure housing I. 5a and a drive shaft 1.5a housed in this pressure housing. 5b, and the inside of the pressure housing 15a communicates with one end of a hydraulic drive system or l\nt system 17 having a flow control valve 17a, and
Drive shaft 1. The lower end of 5b is detachably connected to the upper end of the water removal rod 16 by a gripper (not shown). The other end of the hydraulic drive system 17 can be connected to a drain tank (not shown).

Pressure housing 15a of this hydraulic control rod drive device 15
A latch device 18 is provided in the upper end, which is not shown in detail because it may be a well-known device such as that described in the above-mentioned Japanese Patent Publication No. 63-45560, and the latch device 18 is - 12 engages with the head 24 (see FIG. 1) of the raised drive shaft 15l) to bring the drive shaft 151] to the raised position;
Therefore, the water removal rod 16 can be held in the fully withdrawn position from the fuel assembly 1"-1. That is, the water removal rod 1
6 or valve], assuming it is in the fully inserted position. By opening 7a, the pressure in the upper part of the pressure housing]-5a decreases, so the drive shaft 15b gradually rises under the force of the coolant in the reactor vessel, and its head 24 moves towards the latch W.
18 and comes into contact with the cap 15c at the top end of the pressure housing 1.5a and stops. If the valve 17a is closed at this stage, the pressure inside the pressure housing 15a becomes equal, so that the drive The shaft 15l1 is lowered due to its weight, during which the head 24 is lowered by the action of the latching device 18.
The drive shaft 151] is latched by the latch device 18, and the drive shaft 151 is held in the raised position. When it is desired to lower the drive shaft 1.5b, open the valve 1.7a again and then close it. 5c, passes downwardly through the latch device {8, and is thus released from the locking by the latch device 18, and as a result, the drive shaft 15
h moves to the lowered position, and therefore the water 1j17 and the removed rod 16 move to the fully inserted position into the fuel assembly.

Incidentally, a latch device that operates in this manner is disclosed in the aforementioned Japanese Patent Publication No. 63-45560, so reference can be made to the same publication if necessary.

Next, FIG. 1 shows the piston portion 1. which is the main part of the drive shaft 15b mentioned above. 5 shows details of c, drive shaft]
．． 5b other than those shown in the drawings can have the same structure as the conventional one, so explanations thereof will be omitted. As can be understood from FIG. 1, the piston part 15c of the drive shaft 15l is provided with a latch (this may be the same as the conventional one) at its -to end, and the latch mechanism part 19 Below are an alignment section 20, a driving force generating section 21, which will be explained in detail below. A foreign matter capturing section 22 is provided. The bulb-shaped head 24 provided at the tip of the elongated rod 23 of the latch mechanism section 19 that extends above the driving force generating section 21 (to the left in the figure) is, for example, simply shown above in relation to FIG. The latch device 18 described in 1. is used to selectively lock the latch device 18 as described above and as described in detail in the above-mentioned publication.

First, the driving force generating section 21 will be explained with reference to FIG. 3. The driving force generating section 21 of the preferred embodiment includes a plurality of circumferential grooves 21 spaced apart in the axial direction. The diameter of the dog-diameter portion 211 which has a diameter of 2.a and defines the diameter 21a is smaller by 2δ than the inner diameter of the cylinder 2 (corresponding to the cylinder described in connection with FIG. 7), and is similar to the inner peripheral surface of the cylinder. A gap having a size of δ in the direction of radius Jf is formed between the cylinder and the outer circumferential surface of the piston, and the driving force generating section 21 is configured not to contact the inner circumferential surface of the cylinder.

The gap size δ is selected to actively allow small foreign objects that can pass into the vent system to pass through, but if it is too large, no driving force will be generated, so it should be set appropriately according to the design conditions. be done.

In this way, multiple lectures 2]. If a is formed on the outer peripheral surface of the driving force generating part 21, in the conventional type in which the piston 1/ring of the driving force generating part contacts the inner peripheral surface of the cylinder, the difference If acting on the driving shaft or the upper and lower surfaces of the driving force generating part However, pressure loss occurs due to flow contraction, flow expansion, and pipe friction in each shaft 21a, and this pressure loss acting between both ends of the driving force generating section 21 drives the drive shaft 15b. Ru.

As described above, a small foreign object can pass through the driving force generating section 21, but if a foreign object larger than the dimension δ reaches the driving force generating section 21, it will cause damage to the inner peripheral surface of the cylinder and the surface of the driving force generating section. Therefore, according to the present invention, the above-mentioned foreign matter capturing section 22 is provided downstream of the driving force generating section 2l. As shown in an enlarged view in FIGS. 4 and 5, this foreign matter capturing section 22 traps the coolant containing foreign matter in a fluid passage 22 as shown by an arrow 25.
The fluid passage 22a includes an annular soft packing 22b made of, for example, carbon-based graph oil for passing through the fluid passage 22a, and a filter or strainer 22b such as a wire notch filter provided at the outlet of the fluid passage 22a. A plurality of fluid passages 22a are formed so as to be spaced apart in the circumferential direction and extend in the axial direction, but the inlet and outlet thereof are common, and open into an annular inlet recess 26a and an annular outlet recess 26b, respectively. There is. The filter 2 described above is placed in the outlet recess 26b.
2c is attached by appropriate means.

Since the foreign object capturing section 22 is located upstream of the driving force generating section 21, large foreign objects that might bite into the driving force generating section 21 are captured by the foreign object capturing section 22.

Furthermore, even if the diameter of the driving force generating part 21 is selected as described above, if the driving shaft 15b is not centered with respect to the cylinder 2 (FIG. 3), the driving force generating part 21 will be There is a possibility of coming into contact with

Therefore, according to the present invention, in the embodiment, the driving force generating section 2l
An alignment section 20 is provided that includes a flow path inside the drive shaft that bypasses the flow path.

That is, this alignment part 20 has a structure called a so-called static pressure bearing, and as understood from FIG. 1, a plurality of bypass passages 20a formed inside the piston part 15c of the drive shaft 15b, 20b. An inlet 20a-1 of the flow path 20a is formed upstream of the driving force generating section 21, and an outlet 20a-2 is formed downstream of the driving force generating section 21 at the illustrated position. In addition, the inlet 20b-L of the flow path 20b
The outlet 20b-2 is also located at the illustrated position downstream of the driving force generating section 21. There are four outlets 20a-2 of the flow path 20a, as can be seen from FIG. 6B.

As can be seen from FIGS. 68 to 6p showing cross sections at various positions in FIG. The flow channels 20b are also arranged at angularly eccentric positions with respect to the flow channels 20b, which are also arranged at equal intervals. Therefore, the inlet 20b-1 of the flow path 20b can communicate with the flow path 20b without interfering with the flow path 20a, as shown in FIG. 6C.

In FIG. 1, these channels 20a pass through the foreign matter trap 22.
, 20b is indicated by arrows. When the coolant flows in this way, the pressure in the plurality of recesses, which are the outlet 20a-2 of the flow path 20a, is increased by the drive shaft 15b.
When the piston part 15c is located at the center of the cylinder, they are balanced in an equal state; however, when the piston part 15c moves away from the center of the cylinder, the pressure in the recess on the drive shaft side close to the inner peripheral surface of the cylinder increases, The pressure in the recess on the opposite side decreases, and a centripetal force acts to return the drive shaft toward the center of the cylinder.

As is well known, in a nuclear reactor equipped with a hydraulic drive system having the structure described above, the valve shown in Figure 2 is activated at the beginning of the operation cycle to eliminate the water moderator in the reactor core. 17a is closed, the drive shaft=12 15b is lowered together with the water exclusion rod 16, and the water exclusion rod 16 is inserted into the fuel assembly (not shown) of the reactor core. Then, when the reactivity decreases in the latter half of the operation cycle, the valve 17a is opened to create a pressure difference between both ends of the driving force generating section 21, and the drive shaft 15b, and therefore the water removal rod 16, are pulled out.

When the coolant, ie, the water moderator, flows in the direction shown by the arrow in FIG. 1 in order to move the drive shaft 15b in this way, the drive force generating section 21 does not come into contact with the inner circumferential surface of the cylinder. The water moderator passes through a foreign object capturing section 22 located upstream of the driving force generating section 21, and large foreign objects that might bite into the driving force generating section 21 are captured by the foreign object capturing section 22. Thereafter, the water moderator enters the flow l\820a, 20b and holds the drive shaft 15b at the center of the cylinder 2.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications are possible. For example, a groove was provided in the driving force generating part to cause pressure loss due to flow contraction, flow expansion, and pipe friction, but instead of providing a groove, the surface roughness of the driving force generating part 0 was set to A depression W may be formed on the surface of the driving force generating portion to generate pressure loss. In addition, in the embodiment, two types of bypass flow paths 2 are used.
0a and 20b are provided, but the high pass flow path 20a
There is no need to pass through the inside of the driving force generation part,
Bypass channel 20b is not necessarily required.

[Effects of the Invention] As described above, according to the present invention, the piston portion of the drive shaft is connected to the driving force generating portion disposed with a gap in the cylinder, and does not pass through this gap. Since it has a floating object capturing section that captures foreign objects and an alignment section that aligns the drive shaft with respect to the cylinder axis, unlike conventional cylinders, there is no possibility that the inner peripheral surface of the cylinder will be damaged or foreign objects will be caught. In the worst case scenario, this can prevent the drive shaft from becoming stuck.

[Brief explanation of drawings]

FIG. 1 is a side view showing a part of a hydraulic drive device according to the present invention in a partially cross-sectional view with a horizontal drive shaft shortened in length in the vertical direction, and FIG. 2 is a side view showing a part of the hydraulic drive device according to the present invention Water 17} A partial cross-sectional view of a Harryo reactor equipped with a hydraulic drive system for removing rods. Figure 3 is an enlarged view of a part of the driving force generating part in the drive shaft piston l/n part of Figure 1. Figure 4 (:J) is a cross-sectional view showing the part of the cylinder that captures foreign matter in the drive shaft shown in Figure 1. The fS sectional views along the line, Figures 68 to 6D, are 6^-6 in Figure 1.
8 line, 613-6B line, 6C-6C line, and 6D-6D line; Figure 6E is a cross-sectional view along line 6E-6E in Figure 6B; Figure 7 is a conventional water pressure FIG. 2 is a schematic cross-sectional view of a drive device. 2...Fluid cylinder 15...Hydraulic control rod drive device 1.5b Drive shaft 1. ．． 5 c. Piss I
・N part 17...Hen 1~ system 20...Aligning part 20
a. Bypass flow path 201]...High bus a tdF
t21...Driving force generation section 22...Foreign object extraction section 22a
...Fluid passage JP-A-3 28795 (6)

Claims (1)

[Claims] In a hydraulic control rod drive device including a fluid cylinder communicating with a vent system and a drive shaft having a piston portion movably disposed within the fluid cylinder, the piston portion of the drive shaft is connected to the fluid cylinder. a driving force generating portion having a diameter that creates a gap of a predetermined size between the driving force generating portion and the inner circumferential surface of the driving force generating portion;
A foreign matter capturing section is provided upstream of the driving force generating section with respect to the fluid flow direction and has a fluid passage therein; 1. A hydraulic control rod drive device comprising: an alignment section having an internal bypass flow path for guiding the section to a downstream outer circumferential surface.