JPS58127197A - Reactor control rod drive mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a control rod drive mechanism for a boiling water nuclear reactor, and more specifically, the drive mechanism of the control rod remains stable even when the control rod is completely withdrawn from the reactor core. The present invention relates to a control rod drive mechanism equipped with a cooling system that can prevent the control rod drive mechanism from becoming high temperature by ensuring a cooling water flow path within the control rod drive mechanism.

Technical background of the invention and its problems The control rod drive mechanism of a conventional boiling water nuclear reactor will be explained with reference to FIG.

The hydraulic cylinder 1 is vertically and watertightly fixed to the bottom wall 2 of the pressure vessel of the reactor at its upper end outer wall, and the lower end of the control rod guide tube 3 is vertically and watertightly fixed to the upper end surface. The inside and the inside of the control rod guide tube 3 communicate with each other to form a water flow path. The piston 4 is movable up and down within the hydraulic cylinder 1, and the upper end of the upper piston rod 5 is connected to the joint 6.
A control rod 7 that can be freely moved up and down within the control rod guide tube 3 via
is connected to the bottom edge of the The outer periphery of the lower end of the joint 6 forms a valve-shaped part 8, and the valve-shaped part 8 is connected to the lower part of the control rod guide tube 3/9.
) It is possible to close the communication water flow path between the inside of the hydraulic cylinder 1 and the inside of the control rod guide pipe 3 by engaging with the valve seat part 9 provided on one side.

The piston 4 is provided with a through hole in its central length direction,
This through hole forms an internal cylinder 10. The interior of the internal cylinder 10 communicates with the interior of the control rod guide tube 3 via a communication hole 11 near its upper end.

The internal piston 12 has an upper piston head 13 having a small diameter at the upper end and a lower piston head 14 having a large diameter at the lower end and a small diameter protrusion at the center of the lower tip. The lower piston head 14 through which the head is inserted is fitted into the large diameter part of the lower end of the hydraulic cylinder 1 so as to be able to move up and down.
and the lower bottom wall 17. Outer circumference and inner circumference of the piston head of the piston 4, upper piston head 13
Two annular seals 18, 19, and 20° 21 are fitted into the outer periphery of the lower piston head 14, respectively. The center of the internal piston 12 runs from the lower end of the lower piston head 14 (7) to the upper piston head 13 in the longitudinal direction.
A deep hole 22 is provided, and the upper end of the deep hole 22 is connected to the communication hole 2.
It communicates with the inside of the internal cylinder 10 via 3. The piston 4 is vertically movable along the hydraulic cylinder 1 as described above, and is also vertically movable along the internal piston 12.

On the bottom outer wall of the hydraulic cylinder 1, there are a first water supply channel 24 that opens into the hydraulic cylinder 1 between the piston 4 and the lower piston head 14, and a second water supply channel 25 that opens into the water pressure cylinder 1 below the lower piston head 14. The first water supply channel 24 and the second water supply channel 25 are connected to an operational cold water water supply device (not shown) via water pipes 26 and 27, respectively.

The branch narrow channel 28 branches from the second water supply channel 25 and rises vertically within the circumferential wall of the hydraulic cylinder 1, and its upper end is below the valve seat portion 9 for water flow communicating between the hydraulic cylinder 1 and the control rod guide W3. It opens onto the road.

When high-pressure operating cold water is fed into the hydraulic cylinder 1 through the water supply pipe 26 and the water supply conduit 24, the piston 4 is pushed upward, and the control rod 7 is moved into the reactor (not shown) inside the pressure vessel whose bottom wall is 2. It is inserted into the reactor core and maintained at a desired insertion depth by known means (not shown). At the same time, the lower piston head 14 is pushed down and its lower tip comes into close contact with the lower bottom wall 17 of the hydraulic cylinder 1, thereby closing the lower end opening of the deep hole 22.

The working cold water sent from the water pipe 27 to the second water channel 25 passes through the branched narrow channel 28, is depressurized by the channel resistance, flows into the hydraulic cylinder 1 from above, and is pushed up as the piston 4 rises. It is pushed out from the upper end of the hydraulic cylinder 1 into the control rod guide tube 3 together with the operating cold water in the pressure vessel, and then mixed with reactor water in the pressure vessel.

At this time, each of the above-mentioned parts constituting the control rod drive mechanism is cooled by being immersed in operating cold water.

When the supply of operating cold water into the hydraulic cylinder 1 via the first water supply channel 24 is stopped and high-pressure operating cold water is supplied to the second water supply channel 25, the lower piston head 14 is pushed up and its upper end surface becomes the hydraulic cylinder. The lower part (5) in 1 stops when it comes into contact with the step part 16, and the high-pressure operating cold water flows through the deep hole 22.
The piston 4 enters the internal cylinder 10 through the communication hole 23.
is depressed, and as the piston 4 descends, the control rod 7 also descends via the stitch 6. When the valve-shaped portion 8 of the joint 6 reaches the point where it contacts the valve seat portion 9, the lowering of the piston 4 is inhibited and the control rod 7
will be in a fully withdrawn state, and the reactor equipped with this control rod drive mechanism will be in a steady operating state. At this time, at the valve-shaped part 8 and the valve seat part 9, the control rod guide pipe 3 is inserted from inside the hydraulic cylinder 1.
Since the working cold water flow path into the control rod drive mechanism is cut off, there is no flow of working cold water within this control rod drive mechanism, and each of the components of the control rod drive mechanism is exposed to the high temperature reactor in the pressure vessel located above it. Due to the influence of water, the temperature rises above the limit value, making the operation unsmooth, and in particular, there is a risk that the sealing materials 18 to 21 may deteriorate and wear out. In order to avoid this situation, conventionally, the control rods 7, which are fully withdrawn, are raised slightly and inserted into the reactor core as described above to ensure the flow of operating cold water. This may disrupt the symmetry of the control rod withdrawal pattern (6) and may cause distortion in the power distribution within the sub-reactor.

Purpose of F# This invention was made in order to solve the above-mentioned problems of the conventional control rod drive mechanism of a nuclear reactor. By securing a flow path for operating cold water into the control rod guide tube fixed to the upper end and cooling the control rod drive mechanism with operating cold water, the temperature of the control rod drive mechanism is prevented from rising and the control rod drive mechanism operates smoothly. It is an object of the present invention to provide a control i-rod drive mechanism that can maintain the temperature and prevent deterioration and wear of the sealing material, which is a component of the control rod drive mechanism, due to temperature rise.

Summary of the Invention A control rod drive mechanism for a nuclear reactor according to the present invention has a hydraulic cylinder piston mechanism whose upper end is fixed to the bottom of a pressure vessel, and a control rod guide that guides a control rod to the upper end of the hydraulic cylinder so as to be able to move vertically. The lower end of the pipe is fixed, and the upper end of the hydraulic cylinder and the lower end of the control rod guide tube form a communicating water flow path that can be opened and closed.The upper end of the hydraulic cylinder communicates with the lower end of the control rod guide tube. The above objective is achieved by adding a bypass water flow path and installing a check valve in this bypass water flow path that allows water flow only in the direction from the hydraulic cylinder side to the control rod guide pipe and blocks water flow in the opposite direction. It is.

Examples of the invention An embodiment of the invention will be described with reference to FIG.

The control rod drive mechanism according to the present invention adds a bypass water flow path to the water flow path that communicates the inside of the hydraulic cylinder, which is a component part of the conventional control rod 1 drive mechanism, and the inside of the control rod guide tube whose lower end is fixed to the upper end of the hydraulic cylinder. A check valve is provided in this bypass water flow path, and the other parts are the same as the conventional control rod drive mechanism explained above with respect to Fig. 1, so the parts shown in Fig. 2 are Components that are the same as those shown in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted and replaced with the above explanation regarding FIG. 1.

The control rod guide pipe 30 is provided with a bypass water flow path 31 on its bottom wall ζ, which is fixed to the upper MIi of the hydraulic cylinder l.
The third bypass water flow path is provided with a check valve 32 that allows water to flow from the hydraulic cylinder 1 to the control rod guide pipe 30 and prevents water flow in the opposite direction.
(Fig. 1).

The supply of high-pressure operating cold water from the water pipe 26 is cut off, and the high-pressure operating cold water flows through the water pipe 27, second water channel 25, deep hole 22, and communication hole 23.
When the piston 4 is fed into the internal cylinder 0 through the When the part 8 comes into contact with the valve seat part 9,
The control rod 7 is fully withdrawn, and direct communication of the operating cold water between the inside of the hydraulic cylinder 1 and the inside of the control rod guide pipe 30 is cut off.

However, even when the control rod 7 is fully withdrawn, the operating cold water that has flowed into the cylinder 1 via the branch gauging channel 28 pushes open the check valve 32 via the bypass water channel 31 and flows into the control rod guide pipe 30. The flow path for operating cold water is secured.

As a result, this control rod drive mechanism is cooled by the operating cold water even in the fully withdrawn state ζ of the control rods 7, so that the influence of high-temperature reactor water in the pressure vessel, where 2 forms the bottom wall (9), is reduced. As a result, the control rod drive mechanism does not experience smooth operation due to temperature rise, and in particular, the sealing materials 18 and 21 are prevented from deterioration and wear due to temperature rise.

On the other hand, closing of the water flow path by the valve-shaped portion 8 and valve seat portion 9 and the check valve 3
2 prevents the reactor water inside the pressure vessel from flowing down into the control rod drive mechanism, so maintenance and inspection of the control rod drive mechanism can be performed without leakage of reactor water.

Effects of the Invention As described in detail above in the embodiment, the control rod drive mechanism according to the present invention has a lower end in the hydraulic cylinder of the control rod drive mechanism which is fixedly suspended from the bottom of the reactor pressure vessel and at the upper end of the hydraulic cylinder. A bypass water flow path is provided in the water flow path that communicates with the inside of the fixed control rod guide pipe, and a non-return check is installed in the bypass water flow path to allow only water flow from the hydraulic cylinder side to the control rod guide pipe side and to block water flow in the opposite direction. By using a configuration with a valve, even when the main water flow path from the hydraulic cylinder to the control rod guide tube is closed (10) when the control rod is fully withdrawn, water can still flow from the hydraulic cylinder to the control rod guide tube. The water flow of the control rod drive mechanism is secured by the bypass water flow path, thereby cooling the control rod drive mechanism with its operating cold water, preventing the temperature rise of the control rod drive mechanism due to the influence of high temperature reactor water, and maintaining smooth operation. It has the effect of preventing deterioration and wear of the sealing material, and also controls the reactor water inside the pressure vessel through the control rod guide pipes by closing the valve seat of the main water flow path and closing the bypass water flow path with a check valve. This has the effect of preventing leakage of reactor water into the rod drive mechanism and eliminating problems caused by leakage of reactor water during maintenance and inspection of the control rod drive mechanism.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional control rod drive mechanism, and FIG. 2 is a longitudinal sectional view of a control rod drive mechanism according to the present invention. 1...Hydraulic cylinder, 2...Bottom wall of pressure vessel, 4...
・Piston, 6... Joint, 7... Control rod, 8... Valve-shaped part, 9... Valve seat part, 30... Control rod guide tube, 31
...Bypass water flow path, 32...Check valve. (11) Figure 1

Claims (1)

[Claims] A hydraulic cylinder having an upper end connected to the inner number of the control rod guide tube 3 and having a water flow path communicating with the control rod guide tube, a piston that is movable up and down within the hydraulic cylinder, and a piston that is movable up and down within the control rod guide tube. a joint that connects the lower end of the control rod to the upper end of the piston rod in the upper part of the piston, and the lower end forms a valve-like part that opens and closes the water flow path in a valve seat part below the control rod guide pipe, and In a control rod drive mechanism for a nuclear reactor that is fixed perpendicularly to the bottom of a vessel, there is provided a bypass water flow path that communicates the upper part of the hydraulic cylinder and the lower part of the control rod guide pipe without passing through the valve seat; A control rod drive mechanism for a nuclear reactor, characterized in that a check valve for blocking water flow from the inside of the control rod guide pipe toward the inside of the hydraulic cylinder is provided in the water flow path.