JPS632480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jet pump that is a device for supplying a necessary flow rate of coolant to a reactor core in a boiling water nuclear reactor.

A jet pump according to the prior art will be explained below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a reactor recirculation system, where 1 indicates a reactor pressure vessel, a jet pump, 2 is installed inside the reactor pressure vessel 1, and together with a recirculation pump 3, a reactor recirculation system is installed. It is provided as a circulation system and supplies the necessary flow rate to the reactor core 4 as the reactor output increases or decreases. A portion of the coolant 5 circulating in the reactor core 4 is transferred to the reactor pressure vessel 1.
After being taken out to the outside and pressurized by the recirculation pump 3, it is injected from the nozzle of the jet pump 2 at high speed as the driving fluid for the jet pump 2. The remaining coolant is sucked into the jet pump due to the low pressure created in the absorption section at the nozzle outlet by this high-speed jet, and is sent to the core lower plenum 7 after being thoroughly mixed with driving water in the jet pump.

Figure 2 shows the structure of the jet pump. In the figure, 10 is a riser elbow, 11 is a riser pipe,
12 is the transition piece, 13 is the elbow, 1
4 is a nozzle, 15 is a mixer, 16 is a diffuser, 17 is a bracket, 18 is a support, 19 is a wedge, 20 is a beam, 21 is a beam bolt,
22 is a riser brace. riser elbow 1
0, the riser pipe 11 and the transition piece 12 are welded together, and the end of the riser elbow 10 is fixed to the reactor pressure vessel by welding. Furthermore, in order to prevent the riser pipe 11 from vibrating in the lateral direction, it is fixed to the pressure vessel by a riser brace 22. In a jet pump, the most important components in terms of structure and function are the elbow 13, nozzle 14, and mixer 15.In particular, the inner surface of the nozzle, through which high-temperature, high-pressure water flows at high speed, wears out over time due to erosion and corrosion during operation, and the inner diameter becomes large. If this happens, the performance will deteriorate and there is a risk that the necessary core flow rate will not be obtained, so it is designed to be able to be removed and replaced. These elbow 13, nozzle 14, and mixer 15 are each assembled integrally by welding, but the connection parts with transition piece 12 and diffuser 16 are connected by a mechanical method rather than welding so that they can be removed. There is. Details of these are shown in FIGS. 3, 4, and 5.

FIG. 3 shows an external view of the attachment portion of the transition piece 12 and the elbow 13. In the figure, 11 is a riser tube, 12 is a transition piece, 13 is an elbow, 14 is a nozzle, 15 is a mixer, 20 is a beam, 21 is a beam bolt, and 27 is a transition piece arm. FIG. 4 shows a detailed view of the attachment of the transition piece 12 and elbow 13, similar to FIG. 3. In the figure, 12 is a transition piece, 13 is an elbow, 20 is a beam, and 21
23 is a beam bolt, 23 is a retainer, 24 is a bolt, 25 is a tensile direction of the beam 20, 26 is a tightening direction of the beam bolt 21, and 27 is a transition piece arm.

The beam 20 and beam bolt 21 are inserted into grooves provided in the transition piece arm 27. In order to press the elbow 13 to the transition piece 12, a previously prepared handler (tensioner) pulls the beam 20 in the pulling direction 25, and while the tensile force is applied to the beam 20, the beam bolt 21 is tightened. It is tightened in the direction 26. In addition, the beam bolt 21 screwed into the beam 20 has a flange at the lower part, and the flange is prevented from easily slipping out from above the elbow 13 with a retainer 23, and the retainer 23 is attached to a horizontal bolt. 24 is fixedly attached to the elbow 13 side.

FIG. 5 shows a mixer 15 and a differential user 16.
Installation details are shown. 15 is a mixer, and 16 is a differential user. The mixer 15 is mechanically inserted into the diffuser 16. 2 to prevent lateral vibration of the removable elbow 13, nozzle 14, and mixer 15. bracket 17, support 18,
A wedge 19 is provided. bracket 17
The riser pipe 1 surrounds the mixer 15 in a ring shape.
1 by welding, and this bracket 1
A wedge 19 is driven into the gap between the mixer 7 and the mixer 5 to prevent lateral vibration. Wetsuji 19
is attached to a support 18 welded to the mixer 15 to prevent it from falling off.

As explained above, the removable elbow 1
3. The beam 20 and beam bolt 21 that tighten the nozzle 14 and mixer 15 ensure sufficient tightening force against the pressure difference between the inside of the jet pump and the reactor and the kinetic energy of the driving water inside the jet pump. Since it is necessary to do so, the stress is the highest in terms of structure, and since it has threaded parts, the stress is particularly high at the bottom of each thread, which has the drawback of easily causing fatigue failure, crevice corrosion, etc.

Due to the above drawbacks, it is conceivable to replace only the jet pump beam 20 and beam bolt 21, but it is impossible to remove the beam bolt and retainer as they are. It is necessary to loosen the bolts 24 that fix the retainer 23 to the elbow 13 and replace them. The jet pump and the surrounding reactor inner vessel are the most important equipment located at the heart of the reactor, and in order to eliminate the above-mentioned drawbacks,
Conventional elbow 13, nozzle 14, mixer 15
Removing the integrated structure and replacing the beam 20 poses problems in terms of workload and increased work potential under high radiation conditions.
It is of utmost importance to replace only the beam bolts 21 from the viewpoint of plant reliability and safety.

SUMMARY OF THE INVENTION An object of the present invention is to provide a replacement handling device for remotely handling retainer mounting bolts in order to replace the beam and beam bolt of a jet pump.

An embodiment of the present invention will be described below with reference to FIGS. 6, 7, and 8. A beam bolt 21 screwed into a beam 20 of a jet pump in a reactor pressure vessel is prevented from coming off by a retainer 23. This retainer 23 is fixed to the elbow 13 side of the jet pump by horizontal bolts 24.

The square bolt head of the beam bolt 21 is hooked into the hole 36 of the base 29, as shown in FIGS. 6 and 8, and is horizontal. The hole 36 has the same square shape so that the head of the square bolt can fit into the hole 36.

In the through hole 37 opened vertically in the base 29,
A post 31 is rotatably passed through the post, and a square head 38 is fixed to the top of the post, and the square head 38 is inserted into a socket 30 inserted from above into the reactor pressure vessel in the direction of rotation. They are shaped to interlock.

A socket 33 that engages the bolt 24 in the rotational direction
and the pole 31 are connected by a joint bar 32 so as to be rotatable at the same time. joint bar 32
An example is shown in FIG. That is, the lower part of the pawl 31 is placed inside the case 39, and the bevel gear 40 is fixed to the pawl 31 portion inside the case 39. Another bevel gear 41 that meshes with this bevel gear 40 is fixed to the end of a rotary bar 42 within the case 39. The other ends of the rotating bar 42 are fixed to the socket 33 with their centers aligned with each other.

Such a joint bar 32 is connected to the pole 31.
The rotational force is converted into rotation of a horizontal rotating bar 42 by the combination of gears 40 and 41. Then,
Regardless of the combination of the bevel gears 40 and 41, it is sufficient that the driving force transmitting means transmits the rotational force from the vertical direction to the horizontal direction of the joint bar 32.

In this embodiment, since the post 31 is held by the base 29 so as not to fall down too much, the socket 30 is attached to the square head 38 of the post 31.
This socket 30
The post 31 is rotated in the direction of the arrow 34 by rotating it from a remote location using a shaft fixed to the shaft. This rotational driving force is transmitted from the post 31 to each bevel gear 4.
Arrow 35 to horizontal rotating bar 42 through 0,41
It is transmitted as a rotational driving force in the direction. Therefore, the socket 33 also rotates to loosen the bolt 24 and disconnect the bolt 24 from the elbow 13.

When the bolts 24 are loosened, the retainer 23 can be removed from the elbow 13, and the beam 2
0 and beam bolt 21 can be replaced. As a result, compared to the method of replacing the beam 20 and the beam bolt 21 in the prior art by removing the integral structure of the elbow 13, the nozzle 14, and the mixer 15, in the present invention, the beam 20 and Only the beam bolt 21 can be removed.

Since the present invention uses a replacement device configured as described above, it is possible to remove only the beam and beam bolt, and compared to conventional methods, it has the effect of reducing work man-hours and radiation exposure. have

Although the most preferred specific embodiment has been shown in the above embodiment, similar effects can be obtained by changing the shape of each component or by using an integral structure due to the characteristics of the present invention.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the reactor recirculation system, Figure 2 is an overall configuration diagram of the jet pump in Figure 1, and Figures 3 and 4 are installation details of the transition piece and elbow in Figure 1, respectively. 5 is a detailed view of the installation of the adapter and differential user shown in FIG. 1, FIG. 6 is a front view of an embodiment of the retainer bolt remote replacement device of the present invention, and FIG. FIG. 8 is a longitudinal cross-sectional view of the joint bar portion, and FIG. 8 is a plan view of the base shown in FIG. 6. 13...Elbow, 20...Beam, 21...Beam bolt, 23...Retainer, 24...Bolt, 28...Keeper, 9...Base, 30...
Hook, 31...Pole, 32...Joint bar, 33...Socket, 34...Pole rotation direction, 35...Joint bar rotation direction.

Claims (1)

[Scope of Claims] 1. A reactor pressure vessel having a retainer fixed to the jet pump side with a horizontal bolt, and the retainer preventing the lower part of the beam bolt screwed onto the beam of the jet pump from coming off toward the jet pump side. The jet pump structure includes a base through which a vertical pole is freely rotatable, a square head attached above the base of the pole and shaped to engage with a socket, and another shape shaped to engage with the horizontal bolt. A retainer bolt remote replacement device comprising a socket and a driving force transmission device connected between the other socket and the pole and converting rotational driving force from vertical to horizontal direction. . 2. A retainer bolt remote replacement device according to claim 1, wherein the base has a hole into which a bolt corner head of a beam bolt can be inserted.