JPH04240594A - Tool for handing in-core locknut - Google Patents

Abstract

PURPOSE:To tighten a nut in a short time with remote operation by operating a operating pole, engaging a socket of that upper end with an in-core locknut, rotating the operating pole, and tightening the locknut. CONSTITUTION:A worker 50 stands directly under a fixed in-core locknut N, and a hexagonal socket 56 of an operating pole 53 removed from a base 52a of a frame 52 of the lower part is engaged with the nut N. Another workman 50 takes the base 52a directly under the pole 53, and installs the pole 53 in the frame 52a. Next, the socket 56 and the nut N being engaged with the socked 56 is confirmed, a handle 60a is operated, a spring cap 60 is driven, upward spring force is applied to the pole 53, and the socket 56 is pushed against the nut N. A torque wrench 54 is applied to a wrench connecting element 55, the pole 53 is rotated, and the nut N is tightened. In the case of removing the nut N, the same procedure as above is taken. However, the rotational direction of the pole 53 by the wrench 54 becomes reverse.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Field of Industrial Application] The present invention relates to a neutron instrumentation tube in a boiling water nuclear reactor equipped with a motor-driven control rod drive mechanism, and more particularly to an in-core tightening nut for fixing the neutron instrumentation tube. Concerning tightening nut handling tools.

0002

[Prior Art] Since the output of a nuclear reactor such as a boiling water reactor is proportional to the neutron flux, a nuclear reactor is equipped with a neutron flux detector (neutron flux monitor) to monitor the neutron flux. The detected output of this neutron flux monitor is used to display reactor output, evaluate burnup, etc. The neutron flux detector is equipped with a startup region monitor (hereinafter referred to as SRNM).
and output area monitor (referred to as LPRM, APRM, etc.)
There are multiple monitors installed in each reactor core. Among the above, SRNM measures the neutron multiplication factor while approaching criticality and the neutron flux while increasing the reactor power.

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

The neutron instrumentation tube 1 is formed into an elongated tube shape, and its upper end is elastically supported in a supporting recess 5a formed on the lower surface of the upper grid plate 5, and its lower end is connected to the neutron instrumentation tube 1. The lower surface of the reactor pressure vessel 2 via the in-core guide pipe 8 and the in-core housing 9 that concentrically surround the
It protrudes downward. Further, the lower end of the neutron instrumentation tube 1 is supported in contact with an in-core flange 10. In addition,
The lower end of the neutron instrumentation tube 1 is connected to the in-core flange 10
is fixed by an in-core tightening nut 11. The in-core flange 10 is fixed to a flange 9a provided at the lower end of the in-core housing 9 with tightening bolts 12.

[0005] To attach the neutron instrumentation tube 1 to the core 3 of a nuclear reactor, the following steps are performed. 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 so that 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 at the top of the neutron instrumentation tube 1, and an upward spring force is applied to the plunger 13 by a coil spring 14. . Therefore, after suspending as described above, while pushing down the plunger 13 against the spring force, the tip 13a of the plunger 13 is fitted into the support recess 5a, and the neutron instrumentation tube 1 is made elastic. It can be attached to. Finally, Incore tightening nut 11
tighten the lower end of the neutron instrumentation tube 1 to the in-core flange 1.
Fix it to 0 and complete the installation.

On the other hand, in order to remove the neutron instrumentation tube 1 from the reactor core 3, the procedure described above can be reversed. That is, first remove the in-core tightening nut 11 fixing the lower end, and then push down the plunger 13 against the elasticity of the coil spring 14 while inserting its tip 13a into the supporting recess 5a.
The gripping ring 13b is grasped and lifted using an appropriate handling tool (not shown), and removed from the reactor core 3.

By the way, at the lower end of the neutron instrumentation tube 1, as shown in FIG.
As shown in FIG. 1, a sensor cable 15 is connected, and this sensor cable 15 is inserted into a cable guide 16, and a signal cable 18 is connected to its terminal via a cable connector 17. The signal cable 18 is led 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 into the lower end of the neutron instrumentation tube 1, and a seal 19 provided therein protects the cable connector 17 from water leakage.

[0008]

[Problems to be Solved by the Invention] In a boiling water reactor, a large number of control rod drive mechanisms (hereinafter referred to as CRD) 21 hang down in a group at the bottom of the reactor pressure vessel 2, as shown in FIG. A large number of CRD housings 22 are arranged around an in-core housing 9 that protrudes downward from the bottom of the reactor pressure vessel 2 . Some boiling water reactors, such as improved boiling water reactors, are designed with a motor-driven control rod drive mechanism (hereinafter referred to as FMCRD). In the above FMCRD, an elongated motor section 23 is attached to the lower part of the CRD housing. The space between adjacent motor sections 23 is extremely narrow. Therefore, when attaching or removing the in-core tightening nut 11 that fixes the neutron instrumentation tube 1 to the in-core flange 10, a worker cannot enter the space, and it is difficult to operate the tightening nut 11 directly by hand. Can not.

The above-mentioned attachment/detachment work of the in-core tightening nut 11 is performed when replacing the neutron instrumentation tube 1 such as the LPRM, SRNM, etc., and the above-mentioned replacement is performed when a plurality of neutron instrumentation tubes, such as 10 tubes each, are replaced during a periodic inspection of the reactor. This will be carried out one book at a time. When replacing the neutron instrumentation tube 1, it is necessary to remove the CRD motor section 23 around the in-core housing 9 before replacing each neutron instrumentation tube, and it takes several hours for each CRD motor section 23 to be removed and installed. I need.

[0010] Therefore, the replacement work of the neutron instrumentation tube 1 performed during a periodic inspection of a nuclear reactor requires an extremely long time, resulting in a prolongation of the periodic inspection time and an increase in the amount of radiation exposure of the workers.

The present invention has been made based on the above circumstances, and has an object to improve the workability of neutron instrumentation tube replacement work, shorten the time required for periodic nuclear reactor inspections, and reduce the amount of radiation exposure of workers. The purpose of this invention is to provide an in-core tightening nut handling tool that can handle in-core tightening nuts. [Structure of the invention]

0012

[Means for Solving the Problems] The in-core tightening nut handling tool of the present invention includes a lower frame having a base and an operation pole support provided on the upper part of the base, and a lower frame that is rotatable and detachable from the operation pole support. a hollow operating pole that is freely supported and has a socket at its upper end that engages with an in-core tightening nut; a water receiving device that surrounds the socket and communicates with the inside of the operating pole at its bottom; A wrench engaging portion is provided.

[0013]

[Operation] In the in-core tightening nut handling tool of the present invention having the above structure, the in-core tightening nut is prepared for attachment and detachment with the operating pole and the lower frame separated. First, the socket at the upper end of the operating pole is engaged with the in-core tightening nut to be removed or installed. Next, the lower part of the operating pole is supported by the operating pole supporting part of the lower frame, a torque wrench is engaged with the wrench engaging part to rotate the operating pole, and the nut is tightened or loosened to attach or detach it.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram of an embodiment of the in-core tightening nut handling tool of the present invention, and FIG. 2 is a partially cutaway front view showing its detailed configuration. FIG. 1 shows a state in which a worker 50 is positioned on a CRD exchange device platform 51, and a lower pedestal 52 and an operating pole 53 are set on an in-core tightening nut. The worker 50 operates the torque wrench 54 to apply rotational force to the operating pole 53.

In FIG. 2, the above embodiment has an operating pole 5
3, and a lower pedestal 5 that rotatably and detachably supports it.
2. The lower end of the operation pole 53 is a small diameter portion 53a, and an operation pole support portion 52b is provided above the base 52a of the lower pedestal 52 to rotatably and detachably support the small diameter portion 53a. Further, a hexagonal wrench engaging portion 55 is provided at the upper end of the small diameter portion 53a. Furthermore, a cylindrical cover 53b with an open bottom end is provided below the wrench engaging portion 55. At the upper end of the operation pole 53 is a hexagonal socket 56 that engages with an in-core tightening nut.
is provided. Further, a water receiving device 57 is provided that surrounds the hexagonal socket 56 and can receive the drain from the in-core flange 10. The operation pole 53 is hollow and has a small diameter portion 5 inside the lower frame 52.
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 inside the operation pole 53 and is discharged via the drain hose 58 inside the lower frame 52.

The operation pole support portion 52 of the lower pedestal 52
A cylindrical spring retainer 60 with a closed upper end is provided inside b so as to be slidable along the small diameter portion 53a and rotatable around the small diameter portion 53a. This spring presser 6
0 is a handle 60 protruding along one diameter from its peripheral wall.
The handle 60a is engaged with the circumferential wall of the operating pole support portion 52b, and an elongated hole consisting of an axial portion and circumferential portions at both 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 presser 60 does not apply any restraint to the spring 59, and the handle 6
When Oa is engaged with the circumferential portion of the upper end, the spring 59 is pressed against the inner surface of the upper end of the cover 53b. The operation pole support section 52b has a threaded section 61 at its lower end, and can be raised, lowered, and positioned by operating a handle 62 provided at the base 52a.

In the above embodiment, the in-core tightening nut is tightened as follows. One of the multiple (for example, three) workers who attaches and detaches the in-core tightening nut,
Operation pole 53 located directly below the in-core tightening nut to be attached and detached and removed from the base 52a of the lower frame 52
Hexagonal socket 56 is engaged with the in-core tightening nut. In this state, another worker than the one mentioned above
The base 52a of the user is brought directly under the operating pole 53, and the operating pole 53 is attached to the base 52a. Next, confirm that the hexagonal socket 56 and the target in-core tightening nut are engaged, and operate the handle 60a to drive the spring presser 60 to apply upward spring force to the operating pole 53. and press the hex socket 56 against the in-core tightening nut. Here, a torque wrench is engaged with the wrench engaging portion 55 and the operating pole 53 is rotated to tighten the in-core tightening nut. In addition, when removing the in-core tightening nut, the same procedure as described above is taken. However, it goes without saying that the direction in which the operating pole 53 is rotated by the torque wrench is opposite to that described above.

As described above, according to the in-core tightening nut handling tool of the present invention, the in-core tightening nut located in a position where it is difficult for an operator to enter and where workability is poor can be easily attached or detached by remote control. Note that the present invention is not limited to the above embodiments. For example, although the wrench engaging portion and the socket are illustrated as having a hexagonal shape, they may have any other suitable shape.

[0019]

As is clear from the above, according to the in-core tightening nut handling tool of the present invention, the in-core tightening nut can be tightened by remote control in a significantly shorter time than before. Therefore, the period required for periodic nuclear reactor inspections can be shortened, and the amount of radiation exposure of workers can be reduced.

[Brief explanation of the drawing]

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

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

FIG. 3 is a schematic diagram showing how a neutron instrumentation tube is attached to a nuclear reactor.

FIG. 4 is a longitudinal cross-sectional view showing in detail how the neutron instrumentation tube is attached.

FIG. 5 is a vertical cross-sectional view showing the structure of the lower part of the neutron instrumentation tube.

FIG. 6 is a schematic cross-sectional view of the lower part of a boiling water reactor employing FMCRD.

[Explanation of symbols]

1...Neutron instrumentation tube 2...Reactor pressure vessel 3...
...Core 4...Core support plate 5...Upper grid plate 5a...Engagement recess 6...Core shroud 8...In-core guide tube 9...In-core housing 9a...Flange 10...In-core flange 11...In-core tightening Attached nut 12...Tightening bolt
50... Worker 51... CRD exchange device platform 52... Lower mount 52a... Base 52b... Operating pole support section 53... Operating pole
53a...Small diameter part 43b...Cover 54...
Torque wrench 55...Wrench engaging part 56...Hex socket 57...Water receiving device 58...Drain hose 59
... Spring 60 ... Spring holder 60
a...handle

Claims (1)

[Claims] 1. A lower pedestal having a base and an operation pole support provided on the upper part of the base, and a socket rotatably and detachably supported by the operation pole support and having an upper end engaged with an in-core tightening nut. A water receiving device that surrounds the socket and communicates with the interior of the operating pole at a bottom, and a wrench engaging portion provided on the operating pole. Incore tightening nut handling tool.