JP2768839B2 - Incore tightening nut handling tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron instrumentation tube in a boiling water reactor having a motor driven control rod driving mechanism, and more particularly to an incore for attaching and detaching an incore tightening nut for fixing the neutron instrumentation tube. The present invention relates to a tightening nut handling tool.

[0002]

2. Description of the Related Art Since the output of a nuclear reactor such as a boiling water reactor is proportional to the neutron flux, the reactor is provided with a neutron flux detector (neutron flux monitor) for monitoring the neutron flux. The output of the reactor, the evaluation of the burnup, and the like are performed based on the detection output of the neutron flux monitor. Activation area monitor (hereinafter referred to as SRNM) for neutron flux detector
And output area monitor (referred to as LPRM, APRM, etc.)
Each of these monitors is installed in the reactor core. In the above, the SRNM measures the neutron multiplication factor during critical approach and the neutron flux during reactor power increase.

A neutron instrumentation tube 1 containing a neutron flux detector such as the SRNM is installed in a reactor core as schematically shown in FIGS. That is, FIGS.
In the reactor pressure vessel 2, a reactor core 3 indicated by a broken line in the figure is accommodated, and the reactor core 3 is surrounded by a reactor core support plate 4, an upper lattice plate 5, and a shroud 6. Although only one neutron instrumentation tube 1 is shown for simplicity of illustration, a plurality of neutron instrumentation tubes are actually installed with their tips inserted into the core 3. I have.

The neutron instrumentation tube 1 is formed in an elongated tubular shape, the upper end of which is elastically supported by a supporting recess 5a formed on the lower surface of the upper grid plate 5, and the lower end of which is provided in the neutron instrumentation tube 1. A lower surface of the reactor pressure vessel 2 via an in-core guide tube 8 and an in-core housing 9 concentrically surrounding
It protrudes downward. The lower end of the neutron instrumentation tube 1 is supported in contact with the in-core flange 10. In addition,
The lower end of the neutron instrumentation tube 1 is
Is fixed by an in-core tightening nut 11. The in-core flange 10 is fixed to a flange 9 a provided at a lower end of the in-core housing 9 by a fastening bolt 12.

In order to attach the neutron instrumentation tube 1 to the reactor core 3 of the nuclear reactor, the operation is performed in the following procedure. First, the neutron instrumentation tube 1 is suspended from above the reactor core 3 and its lower end is inserted into the in-core guide tube 8. Next, the suspension is further advanced, and the lower end of the neutron instrumentation tube 1 is brought into contact with and supported by the tapered receiving surface 10a of the in-core flange 10 as shown in FIG. As is clear from FIG. 4, a plunger 13 is slidably provided on the upper part of the neutron instrumentation tube 1, and a spring force upward is applied to the plunger 13 by a coil spring 14. . Therefore, after the suspension is performed as described above, the tip 13a of the plunger 13 is fitted into the supporting recess 5a while pushing down the plunger 13 against the spring force, and the neutron instrumentation tube 1 is elastically moved. Can be attached to Finally, the in-core tightening nut 11
And tighten the lower end of the neutron instrumentation tube 1 to the in-core flange 1
Fix to 0 and complete the installation.

On the other hand, in order to detach the neutron instrumentation tube 1 from the reactor core 3, a procedure reverse to the above may be taken. That is, first, the in-core tightening nut 11 fixing the lower end is removed, and then, while the plunger 13 is pressed down against the elasticity of the coil spring 14, the distal end 13 a is held in the supporting recess 5 a.
The holding ring 13b is gripped and lifted by an appropriate handling tool (not shown) or the like, and is detached from the core 3.

By the way, at the lower end of the neutron instrumentation tube 1, FIG.
As shown in FIG. 1, a sensor cable 15 is connected. The sensor cable 15 is inserted into a cable guide 16, and a signal cable 18 is connected to a terminal of the sensor cable 15 via a cable connector 17. Signal cable 18
Is guided from the end of the cable guide 16 to a control room (not shown), and transmits a neutron detection signal to the control room. The cable guide 16 is screwed to the lower end of the neutron instrumentation tube 1 and the cable connector 17 is protected from water leakage by a seal 19 provided therein.

[0008]

In a boiling water reactor, as shown in FIG. 6, a large number of control rod drive mechanisms (hereinafter referred to as CRDs) 21 droop in a lower part of a reactor pressure vessel 2 in a group. A number of CRD housings 22 are arranged around the in-core housing 9 projecting downward from the bottom of the reactor pressure vessel 2. Some boiling water reactors, such as improved boiling water reactors, are planning a motor driven control rod drive mechanism (hereinafter referred to as FMCRD). In the above-mentioned FMCRD, an elongated motor portion 23 is attached to a lower portion of the CRD housing. The space between adjacent motor sections 23 is extremely narrow. Therefore, when attaching and detaching the in-core tightening nut 11 for fixing the neutron instrumentation tube 1 to the in-core flange 10, the worker cannot enter the space, and the operation of the tightening nut 11 is directly performed manually. Can not.

The above-mentioned work of attaching and detaching the in-core tightening nut 11 is performed when the neutron instrumentation tube 1 such as LPRM or SRNM is exchanged. It is implemented book by book. At the time of replacing the neutron instrumentation tubes 1, it is necessary to remove the CRD motor portion 23 around the in-core housing 9 before replacing each neutron instrumentation tube. I need.

Therefore, the replacement work of the neutron instrumentation tube 1 performed at the time of the periodic inspection of the nuclear reactor requires a remarkably long time, and as a result, the period of the periodic inspection is prolonged and the radiation dose to the workers is increased.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to improve the operability of neutron instrumentation tube replacement work, shorten the time required for periodic inspection of a reactor, and reduce the radiation exposure of workers. It is an object of the present invention to provide an in-core tightening nut handling tool which can perform the following. [Configuration of the Invention]

[0012]

That is, an in-core tightening nut handling tool according to the present invention comprises: a lower pedestal having an operation pole support at the upper part; a rotatable and detachably supported at the operation pole support at the upper end; A hollow operating pole having a socket engaged with the in-core tightening nut, a water receiver provided on the operating pole surrounding the socket, and water guided from the water receiver to a hollow portion of the operating pole. And a wrench engaging portion provided on the operation pole.

[0013]

The operation of the thus configured incore tightening nut handling device according to the present invention will be described. First, the socket part of the operation pole, which is the upper part divided and configured, is attached to the in-core tightening nut to be removed from below. Next, the lower part of the operation pole is rotatably installed on the lower base, and then a torque wrench is attached to the wrench engaging portion of the operation pole and rotated. By doing so, the in-core tightening nut can be rotated and removed. When the in-core tightening nut is loosened, water comes out from here, but this water is received by the water receiver and can be guided to the outside through the drain pipe from the hollow part of the operation pole. No pollution.

[0014]

1 is a conceptual view of an embodiment of an in-core tightening nut handling tool according to the present invention, and FIG. 2 is a partially cutaway front view showing a detailed configuration thereof. FIG. 1 shows a state in which a worker 50 is located on a CRD exchange device platform 51, and a lower gantry 52 and an operation pole 53 are set on an in-core tightening nut portion. The operator 50 operates the torque wrench 54 to apply a rotational force to the operation pole 53.

In FIG. 2, the operation pole 5 is used in the above embodiment.
3 and a lower gantry 5 for rotatably and detachably supporting the same
And 2. The lower end of the operation pole 53 is a small diameter portion 53a, and an operation pole support portion 52b for rotatably and detachably supporting the small diameter portion 53a is provided above the base 52a of the lower gantry 52. A hexagonal wrench engaging portion 55 is provided at the upper end of the small diameter portion 53a. Further, a cylindrical cover 53b having an open lower end is provided below the wrench engaging portion 55. The upper end of the operating pole 53 is provided with a hexagon socket 56 which engages with the in-core tightening nut.
Is provided. Further, a water receiving device 57 which surrounds the hexagon socket 56 and can receive the drain from the in-core flange 10 is provided. The operation pole 53 is hollow, and the small-diameter portion 5 in the lower mount 52 is provided.
A drain hose 58 is connected to the lower end of 3a. That is, the drain received by the water receiving device 57 flows down in the operation pole 53 and is discharged via the drain hose 58 in the lower base 52.

The operating pole support 52 of the lower frame 52
Inside b, a cylindrical spring retainer 60 that is slidable along the small-diameter portion 53a and rotatable about the small-diameter portion 53a and has an upper end closed is provided. This spring retainer 6
A handle 60 protrudes from the peripheral wall along one diameter.
The handle 60a is engaged with the peripheral wall of the operation pole support portion 52b, and an elongated hole including an axial portion and circumferential portions at upper and lower ends thereof is provided. When the handle 60a is engaged with the circumferential portion at the lower end of the axial portion, the spring retainer 60
Does not restrict the spring 59, and when the handle 60a is engaged with the circumferential portion at the upper end, the spring 59 is pressed against the inner surface of the upper end of the cover 53b. The operation pole support portion 52b has a screw portion 61 at the lower end thereof, and can be moved up and down and localized by operating a handle 62 provided on the base portion 52a.

In the above embodiment, the tightening of the in-core tightening nut is performed as follows. One of a plurality of (for example, three) workers who attach and detach the in-core tightening nut,
An operation pole 53 located immediately below an in-core tightening nut to be detached and detached from a base 52a of a lower frame 52.
Is engaged with the in-core tightening nut. In such a state, another worker other than the above
The second base 52a is brought directly below the operation pole 53, and the operation pole 53 is mounted on the base 52a. Next, it is confirmed that the hexagon socket 56 and the target in-core tightening nut are engaged with each other, and the handle 60a is operated to drive the spring retainer 60 to apply an upward spring force to the operation pole 53. And presses the hexagonal socket 56 against the in-core tightening nut. Here, the torque wrench is engaged with the wrench engaging portion 55 to rotate the operation pole 53, thereby tightening the in-core tightening nut. When removing the in-core tightening nut, the same procedure as described above is taken. However, it goes without saying that the rotation direction of the operation pole 53 by the torque wrench is opposite to the above.

As described above, according to the in-core tightening nut handling tool of the present invention, the in-core tightening nut at a position where it is difficult for the worker to enter and the workability is poor can be easily attached and detached by remote control. The present invention is not limited only to the above embodiment. For example, the wrench engaging portion and the socket are illustrated as being hexagonal, but may have any other appropriate shape.

[0019]

As is apparent from the above description, according to the in-core tightening nut handling tool of the present invention, the tightening of the in-core tightening nut can be performed by remote control in a significantly shorter time than in the past. Therefore, the period required for the periodic inspection of the reactor can be shortened, and the radiation exposure of the workers can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual view of an embodiment of an in-core tightening nut handling tool according to the present invention.

FIG. 2 is a partially cutaway front view showing a detailed configuration of the embodiment.

FIG. 3 is a schematic diagram showing a state in which a neutron instrumentation tube is attached to a nuclear reactor.

FIG. 4 is a vertical cross-sectional view showing a mounted state of a neutron instrumentation tube in detail.

FIG. 5 is a longitudinal sectional view showing a structure of a lower part of a neutron instrumentation tube.

FIG. 6 is a schematic sectional view of a lower portion of a boiling water reactor employing FMCRD.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Neutron instrumentation tube 2 ... Reactor pressure vessel 3 ... Core 4 ... Core support plate 5 ... Upper lattice plate 5a ... Engaging recess 6 ... Core shroud 8 ... In-core guide tube 9 ... In-core housing 9a …… Flange 10…
… In-core flange 11… In-core tightening nut 12… Tightening bolt 5
0: Worker 51: CRD exchange device platform 52: Lower frame 52a: Base 52b: Operation pole support 53: Operation pole 5
3a small diameter portion 43b cover 54 torque wrench 55 wrench engaging portion 56
... Hex socket 57 ... Water receiving device 58 ... Drain hose 59 ...
Spring 60: Spring holder 60a: Handle

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G21C 19/02 G21C 19/20

Claims (1)

(57) [Claims] 1. A lower frame having an operation pole support on an upper part.
The table and this operation pole support section are rotatable and detachable
Socket supported and engaged at the upper end with in-core tightening nut
Surrounding this socket with a hollow operating pole with
From the water receiver provided on the operation pole and this water receiver
Guides the water guided into the hollow of the operation pole to the outside of the lower stand
Drain piping and a wrench engaging part provided on the operation pole
In-core tightening nut handling tool equipped with