JPH08327772A - Water level instrument nozzle mounting structure - Google Patents

Abstract

(57) [Abstract] [Object] An object of the present invention is to provide a new water level instrumentation nozzle mounting structure capable of easily inspecting and repairing a welded part of a water level instrumentation nozzle provided in a pressure vessel body. To do. [Structure] The present invention is provided with a vessel body 1 which constitutes an outer shell of a reactor pressure vessel, and is provided with a water level instrumentation nozzle to which a water level sensor S is connected to measure the water level of cooling water in the vessel body 1. In the structure, the through hole 1 formed in the container body 1
4, a cylindrical nozzle body 15 is inserted from the inside, and the nozzle body 15 is attached by welding from the outer surface side of the container body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure for a water level instrument nozzle provided in a reactor pressure vessel for heating cooling water to generate high temperature and high pressure steam.

[0002]

2. Description of the Related Art FIG.
1 shows an improved boiling water reactor pressure vessel called BWR. As shown, this reactor pressure vessel
The steel pressure vessel shell 1 forming the outer shell is filled with cooling water made of light water, and a core 2 made of a fuel assembly for heating the cooling water and cooling water heated by the core 2 A steam-water separator 3 for separating steam and a steam dryer 4 for drying the steam separated by the steam-water separator 3 are mainly accommodated, and the high-temperature and high-pressure steam generated here is stored in the pressure vessel body 1 Power is supplied from the main steam nozzle 5 provided to the turbine side to a turbine side (not shown). In the figure, 6 is a pump casing for mounting an internal pump that circulates the cooling water in the container body 1, 7 is a stub tube for passing a control rod (not shown), 8 is a core support plate, 9 is an upper lattice plate, Reference numeral 10 is a water supply nozzle or the like, 11 is a skirt flange for supporting the storage container body 1, and 12 is a top mirror.

In addition to the nozzles such as the main steam nozzle 5 and the water supply nozzle 10 described above, the water container body 1 has a water level sensor S for constantly measuring the water level of the cooling water in the water container body 1. A plurality of water level instrumentation nozzles 13 are installed along the height direction. As shown in FIG. 6, this instrumentation nozzle has a nozzle body 15 formed of a small-diameter pipe from the inner surface side of the container body 1 in a through hole 14 formed in the container body 1.
Is inserted and the rear end of the insertion is welded from the inside of the container body 1, and a part of the cooling water or steam in the container body 1 is extracted and made to flow to the water level sensor S side. .

[0004]

By the way, since the reactor pressure vessel is required to have extremely high safety and reliability due to its nature, periodic ISI (in-service inspection) is required.
Is required, and one of the inspection targets is the inspection of the welded portion of the container body 1 and the welded joint portion such as the nozzle. And in order to prevent the influence of radioactivity on the human body during inspection,
It is performed automatically by remote control using an automatic ultrasonic flaw detection robot that uses ultrasonic waves.

However, as described above, in the case of the water level instrumentation nozzle 13, the welded portion is located on the inner surface side of the container body 1 in which the cooling water, the steam dryer 4 and the like are accommodated, and therefore the flaw inspection is performed. In order to perform the above, it is necessary to remove the upper mirror 12 and then move the automatic ultrasonic flaw detection robot with high accuracy while confirming the position of this portion, which requires a lot of time and skill, and Moreover, if cracks or defects were found by this inspection, it was extremely difficult to repair them.

Therefore, the present invention has been devised to solve the above problems, and an object thereof is to easily inspect and repair a welded portion of a water level instrument nozzle provided in a pressure vessel body. (EN) Provided is a new water level instrument nozzle mounting structure.

[0007]

In order to achieve the above object, the present invention is provided in a vessel body which constitutes the outer shell of a reactor pressure vessel, and is for measuring the water level of cooling water in the vessel body. In the mounting structure of the water level instrumentation nozzle to which the device is connected, a cylindrical nozzle body is inserted from the inside into the through hole formed in the container body, and the nozzle body is welded from the outer surface side of the container body. It is designed to be attached.

[0008]

As described above, according to the present invention, the cylindrical nozzle body is inserted from the inside into the through hole formed in the container body, and the nozzle body is attached by welding from the outer surface side of the container body. Therefore, the weld is exposed on the outer surface of the container body. Therefore, not only the automatic flaw detection inspection of the welded portion but also the repair work thereof can be easily performed.

[0009]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a water level instrumentation nozzle according to the present invention. As shown in the figure, this water level instrumentation nozzle has a through hole 14 formed so as to penetrate the container body 1.
The nozzle body 15 formed of a small-diameter pipe is inserted from the inside of the container body 1 and is attached by welding from the outer surface side of the container body 1 in a state where the rear end portion of the insertion is flush with the inner surface of the container body 1. There is.

Further, the rear end portion 15 of the insertion of the nozzle body 15
a and the inside of the through hole 14 are formed in a tapered shape, and when the nozzle body 15 is inserted into the through hole 14 or when the nozzle body 15 is inserted into the through hole 14, the nozzle body 15 is outside the container body 1. It does not fall through.

The welded portion 16 is a groove 1 processed into a ring shape so as to surround the exposed portion of the nozzle body 15.
The buttering material 17, the nozzle body 15, and the build-up welding material 18 having good compatibility are doubly build-up welded to the 6a, and a welding method capable of omitting the heat treatment of the welded portion 16 after welding is provided. Has been taken. That is, as shown in FIG. 2, since the container body in which the groove 16a is formed is generally made of low alloy steel, after the nozzle body 15 is mounted, the weld overlay is directly applied to the groove 16a. This is because if applied, welding strain remains on the base material side and its mechanical properties change, and it is necessary to subject this portion to heat treatment after this build-up welding.

As described above, by welding and attaching the nozzle body 15 conventionally welded from the inner surface side from the outer surface side of the container body 1, the welded portion 16 is attached to the outer surface of the container body 1 in an exposed state. Therefore, not only the automatic flaw detection inspection of the welded portion 16 but also the repair work thereof can be performed from the outside of the container body 1, and the work can be easily performed.
In addition, since the welding part 16 can be easily removed, it is possible to easily replace the nozzle body 15 with a different material. In FIG. 1, reference numeral 20 denotes a clad layer made of a corrosion resistant material such as stainless steel or Inconel, which is formed on the entire surface of the container body 1 to prevent corrosion of the base material of the container body.

Further, as a modified embodiment of the present invention, as shown in FIG. 3, a welded portion 16a between the container body 1 and the nozzle body 15 is formed.
After inserting the nozzle body 15 without forming a groove in the groove, the buttering material 17 and the overlay welding material 18 may be directly overlay welded to the surface of the base material. Also, like the present invention,
When the outer side of the container body 1 is welded, the cooling water or steam in the container body 1 enters the gap between the through hole 14 and the nozzle body 15, which causes corrosion such as oxidation on the base material surface side in particular. Therefore, before welding the nozzle body 15, as shown in FIG. 4, a buttering layer 19 made of a corrosive material may be built up on the inner surface side of the through hole 14 in advance.

[0015]

In summary, according to the present invention, since the welded portion of the water level instrument nozzle is located on the outer surface of the container body, inspection / repair work of the welded portion is facilitated, and the inspection period is shortened. It has excellent effects such as improvement of reliability.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the vicinity of a welded portion of section A in FIG.

FIG. 3 is a sectional view showing a modified example of the present invention.

FIG. 4 is a sectional view showing a modified embodiment of the present invention.

FIG. 5 is an overall sectional view showing the structure of a conventional reactor pressure vessel.

FIG. 6 is a cross-sectional view showing a mounting structure for a conventional water level instrument nozzle.

[Explanation of symbols]

 1 Container Body 14 Through Hole 15 Nozzle Body 16 Welded Part S Water Level Sensor

Claims (1)

[Claims] 1. A mounting structure of a water level instrumentation nozzle, which is provided in a vessel body constituting an outer shell of a reactor pressure vessel, and to which a water level sensor for measuring a water level of cooling water in the vessel body is connected, A mounting structure for a water level instrumentation nozzle, characterized in that a cylindrical nozzle body is inserted from the inside into a through hole formed in the container body, and the nozzle body is welded and mounted from the outer surface side of the container body.