JPS6345593A - Neutron flux monitor housing - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is suitable for replacing a neutron flux monitor housing (hereinafter referred to as ICM housing) in a nuclear reactor pressure reactor (hereinafter referred to as RPV) during the service life of a nuclear power plant. Person in charge,
A new type of ICM that makes it easy to replace the ICM housing.
Regarding the structure of the housing.

[Conventional technology]

The ICM housing of the RPV of the boiling water reactor has a structure as shown in FIG. That is, a through hole 17 is provided in the RPVl which is overlay welded using Inconel material or the like, and the weld overlay seat 7 is connected to the through hole 17 so as to communicate with the through hole 17.
An IcM housing 3 is welded to the RPVI through a welded portion 8 through the wall of the RPVI.

ICM housing 5 of conventional boiling water reactor is 5US3
Since 04 series steel pipes are used, high residual stress occurs in the heat-affected zone near the weld 8 of the ICM housing 5, and a chromium-deficient layer is formed along the grain boundaries, making it susceptible to stress corrosion cracking. arise. Therefore, in the unlikely event that stress corrosion cracking occurs in the ICM housing 5 made of 5US304 series steel pipe, a method of replacing it with a low carbon content stainless steel pipe with high stress corrosion cracking resistance should be established in advance. There is a need.

Regarding the repair of ICM housing, please refer to JP-A-56-82.
696, and the structure of the ICM housing after repair is shown in FIG. 2. As shown in FIG. Cut the housing and make a new I
The CM housing was passed through the wall of the RPV from below the RPV and welded to the cut part of the old ICM housing, but this newly manufactured ICM housing had the same inner diameter as the old CM housing. However, the structure of this ICM housing is based on the design at the time of new plant construction, and as an ICM housing for repair, it is important to consider the workability during repair work and the structure when actually using welding equipment. No consideration was given.

[Problem that the invention seeks to solve]

Since the new ICM housing and the old ICM housing are welded from the inner surface of the new ICM housing, the new ICM bousing of the conventional technology
Due to the structure of the welding machine, it was extremely difficult to make the inner diameter the same as the CBM housing.

Also, instead of inserting the welding machine main body into the newly manufactured ICM housing, as shown in Fig. 8, the welding machine main body 13 is installed under the newly manufactured ICM housing flange, and rotation #15 of the welding machine is rotated inside the RPV. Another option would be to extend it to the welded part and weld it together.

If the rotating shaft 15 of the welding machine is extended, the rigidity of the rotating shaft 15 may be insufficient, and the overlay may not be applied uniformly to the welded part during welding due to vibration of the rotating shaft 15, etc. , there is also a large possibility that reliability will be compromised.

An object of the present invention is to easily manufacture a new welding machine main body 13 using an I.
It is an object of the present invention to provide a structure of a new type of ICM housing that can be inserted into the inner surface of a CM housing, has high reliability, and can be repaired relatively easily.

[Means for solving problems]

＼4 The problem mentioned above is that it was difficult to insert the automatic welding machine body from the inside due to the structural strength and length of the conventional ICM housing. By increasing the inner diameter of the portion of the ICM housing that is not inserted into the melter, the automatic welding machine main body can be easily inserted, and the lack of rigidity of the automatic welding machine rotation shaft can be prevented.

[Effect]

The structure of the new ICM housing, which is welded to the old ICM housing, has a new ICM housing structure with a larger inner diameter from the lower part of the lower mirror below the RPV that is not inserted into the RPV to the lower end. It has become possible to insert a welding machine into the inner surface of the ICM housing, which was previously difficult.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1, 3 to 7.

FIG. 3 shows the RPV of a boiling water reactor.

RPVI is RPVJIg2. RPV lower mirror 3 and RP
It consists of a V-top cover (not shown).

The RPVI is fixed by a skirt 4 on the pedestal (not shown) of the reactor pressure melter.

The ICM housing 5 is fixed to the RPV lower bell 3 by welding.

FIG. 4 shows a cross-sectional view of the ICM housing 5 fixed to the RPV lower mirror 3. On the inner surface of the RPV lower mirror 3, an Inconel built-up part 6 is formed, and this flesh-like part 6 A weld overlay seat 7 is overlay welded on top. The IC:M housing 5 passes through the RPV lower mirror 3 and is fixed to the stub tube 7 by welding 8. 9 is a sensitized region formed in the IC2A housing 5 by this welding 8.

FIG. 1 is a cross-sectional view of a new ICM housing after replacement according to an embodiment of the present invention. 5 to 7 show the steps of a method for repairing an ICM housing according to an embodiment of the present invention. First, as shown in FIG.
A remote-controlled processing machine 10 is inserted into the CM housing 5 from the lower end thereof. Cutting of the ICM housing 5 by the head 11 attached to this remote-controlled processing machine 10;
And, as shown in Fig. 6, in the primary stage where beveling etc.
Pull out the cut ICM housing below the RPVI.

Next, as shown in FIG. 7, the newly manufactured ICM housing 12 is inserted from below the RPVI and welded at the welding portion 14 using a remote-controlled automatic welding machine 13. The structure of the new chome housing 12 to be welded at this time is
As shown in the figure. The ICM housing 12 is attached to the RPV lower fi3 (
7) It is inserted into the RPVI from below, and then a remote automatic welding machine 13 is inserted inside it to perform welding.
The new 10M housing 12 is the RPV below the RPV lower mirror 3.
The inner diameter of the part from the part that is not inserted into the welding machine 1 to the lower end is increased to facilitate insertion into the remote automatic welding machine 13.

According to this embodiment, it is possible to easily insert a welding machine into the ICM housing and weld the welding process, which was extremely difficult in conventional ICM housings, and it is possible to replace the ICM housing relatively easily.

〔Effect of the invention〕

According to the present invention, it is possible to easily insert a welding machine into the ICM housing during welding, and the structure of the welding machine can also shorten the rotation axis, allowing highly reliable welding.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an ICM housing according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of an ICM housing showing a conventional ICM housing repair structure, and Fig. 3 shows a reactor pressure melter lower mirror. New view, FIG. 4 is a sectional view of the repair method of the present invention,
5 to 8 are procedural diagrams of the repair method of the present invention. 1... Reactor pressure melter, 2... RPV fuselage, 3...
・RPV lower mirror, 4... Skirt, 5... ICBM housing, 6... Overlay, 7... Weld overlay seat, 8...
・Welded part, 9... Sensitized area, 10... Remotely controlled cutting device, 11... Head, 12... New IC
M housing. 13...Remotely controlled automatic welding machine, 14...Welding section. 15... Rotating shaft, 16... Sleeve, 17... Through hole, 18... New ICM housing.

Claims (1)

[Claims] 1. A cylindrical weld pad that is inserted through the wall of the reactor pressure vessel into a cylindrical weld pad attached to the inner surface of the reactor pressure vessel, and is connected to the weld pad at a welded portion. During repair work to replace the neutron flux monitor housing,
The welded portion of the neutron flux monitor housing is cut by a cutting device in a plane perpendicular to its axis, and the cut neutron flux monitor housing is removed to the outside of the reactor pressure vessel. During repair work, a newly manufactured neutron flux monitor housing is inserted from below through the wall of the reactor pressure vessel, and welded to the newly manufactured neutron flux monitor housing from the inside using a remote automatic welding machine. The structure of the newly manufactured neutron flux monitor housing to be inserted into the reactor pressure vessel is such that the inner diameter is increased from the lower part of the lower mirror of the reactor pressure vessel to the lower end, and the remote automatic welding machine can be inserted inside. A neutron flux monitor housing characterized by: