JPH0564758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a nuclear reactor pressure vessel, and more particularly to an improvement in the lower head of a pressure vessel of a boiling water reactor (BWR).

[Background of the invention]

Nuclear power generation is steadily increasing in number as it attempts to replace conventional fossil fuel power generation, but the construction costs are much higher than thermal power plants, making it difficult to sustain nuclear power generation into the future. In order to achieve this goal, it is necessary to significantly reduce the construction cost of power plants and shorten the construction period.

In view of this situation, there is a great need for drastic rationalization and shortening of the construction period for reactor pressure vessels, which are one of the main components of nuclear power plants.

On the other hand, there are still strong demands for absolute safety in nuclear power generation, and from this point of view, the reactor pressure vessel is one of the most important pieces of equipment and is required to have high reliability. Therefore, a decline in reliability due to rationalization cannot be tolerated; rather, it is necessary to further improve reliability based on past achievements.

A conventional nuclear reactor pressure vessel is comprised of an upper mirror 1, a body 2, and a lower mirror 11, as shown in FIG. Of these, the lower mirror is composed of a lower mirror dome 12, a lower mirror pedal 4, a shroud support 5, and a stub tube 13, as shown in FIG. It passes through 12. As shown in FIGS. 7 and 9, the lower mirror dome 12 has a hemispherical three-dimensional structure in which the stub tube 13 is attached.

FIG. 8 shows an example of details of a conventional stub tube attachment part. Stats tube 13 is
A short tube made of Inconel alloy, 1100MWe class
In the case of BWR reactor pressure vessels, there are 185.

The stub tube 13 is attached to the lower mirror dome 12 by welding, and the control rod housing 7 is attached through this, and the upper end of the stub tube 13 is fillet welded to the control rod housing 7. When installing the stub tube 13, the control rod housing 7 needs to be inserted vertically into the gap between the fuel assemblies, so a strict tilting tolerance (inclination of the center axis of the stub tube) is required. Great care is taken in welding. In addition, the inner surface of the pressure vessel of the lower mirror dome 12 has an Inconel overlay layer 1.
4 is formed, and the stub tube 13 is made of Inconel alloy because it needs to have approximately the same strength as the low alloy steel used for the lower mirror dome and excellent corrosion resistance.

Such conventional technology has the following problems in terms of the manufacturing process.

(1) The welded part between the stud tube 13 and the lower mirror dome 12 has a three-dimensional structure and is not axially symmetrical.
The amount of weld metal at each position on the circumference is different, and in a normal welding procedure, the collapse caused by shrinkage of the weld metal during solidification becomes non-uniform at each position on the circumference. As a result, a large collapse occurs when welding is completed.

For this reason, in the prior art, welding is performed by adjusting the amount of deposited metal by manual welding, which requires a large amount of time and man-hours.

In addition, in order to control the above-mentioned collapse, welding is often interrupted to measure the collapse, and welding and collapse measurement are performed alternately, resulting in extremely inefficient welding work.

(2) The welding part between the stub tube 13 and the lower mirror dome 12 is (a) because the lower mirror dome 12 is hemispherical, as is clear from FIGS. 7 and 9. 185
The groove shapes of the book stub tubes 13 are different, (b). Even for one stud tube 13, the groove shape is three-dimensional and different at each position on the circumference, so it is difficult to apply automatic welding, and the unwelded parts are attached by hand welding. . For this reason, the starting tube 1
3 and the lower mirror dome 12 requires a large amount of man-hours and time.

(3) In the case of 1100MWeBWR, 185 stub tubes 13 are attached to the lower mirror dome 12, so not only the groove shape is different at each welding part, but also the spacing between the stub tubes 13 is very narrow at about 250 mm. Due to poor workability during welding, a large amount of man-hours and time are required for welding.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above, to provide a nuclear reactor pressure vessel that can be easily manufactured in a short period of time and has high reliability.

[Summary of the invention]

The present invention provides a reactor pressure vessel comprising an upper mirror, a body, and a lower mirror in which a control rod housing through hole is formed, wherein the lower mirror has an inner surface of the pressure vessel with respect to a hole axis of the control rod housing through hole. By providing a mirror plate formed in a planar shape so as to be perpendicular to each other,
The above objectives have been achieved.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the overall structure of a nuclear reactor pressure vessel showing one embodiment of the present invention. This reactor pressure vessel is composed of an upper mirror 1, a body 2, and a lower mirror 3, and is supported by a cylindrical support skirt.

As shown in FIG. 2, the lower mirror 3 has a mirror plate 3A attached to the body 2 via a lower mirror pedal 4.
The end plate 3A is formed of an integrally forged product of low-alloy steel or a steel plate, and is provided with a through hole 7A through which the control rod housing 7 passes, and the inner surface of the pressure vessel is planar so as to be perpendicular to the through hole 7A. It is formed.

A stub tube 6 is provided on the surface of this planar head plate 3A, and a shroud support 5 for supporting the reactor internals is fixed to the head plate 3A and the lower mirror pedal 4 by welding. ing.

As shown in FIG. 3, the stub tube 6 is formed integrally with the end plate 3A without welding, and the stub tube 6 and the end plate 3A, which are integrally formed, are lined with a stainless steel or Inconel lining 8. Although not particularly shown, the inner surfaces of the body 2 and the lower mirror pedal 4 are also lined with stainless steel or Inconel. The upper end surface of the stub tube 6 provided with the lining 8 and the control rod housing 7 are fixed by fillet welding.

In the embodiment shown in FIGS. 1 to 3, the end plate 3
The inner surface of the pressure vessel A is formed into a planar shape perpendicular to the hole axis of the through hole 7A for the control rod housing 7 to pass through.
The work of fixing it to the end plate 3A is a two-dimensional work, which is easy and allows the application of machines such as automatic welding machines.

In addition, since the end plate 3A has a flat surface on which the stub tube 6 is formed, the work is much easier than the conventional three-dimensional work of integrally forming the stub tube 6 from the hemispherical lower mirror dome 12.
Moreover, since it is formed integrally with the stub tube 6, the work of fixing the end plate 3A and the large number of stub tubes 6 by welding and the work of inspecting the same can be omitted.

Conventionally, the weld between the stub tube 13 and the lower mirror dome 12 was required to undergo a radiographic test according to regulations, and a split liquid penetrant test was conducted in which a liquid penetrant test was performed on each one-third of the weld layer. Inspecting the welded portion required a large amount of man-hours and time.

Furthermore, according to this embodiment, the stub tube 6 formed integrally with the end plate 3A is lined with stainless steel or Inconel, so there is no need to use an expensive Inconel alloy for the stub tube itself as in the conventional case.

FIG. 4 is a sectional view of a main part of a nuclear reactor pressure vessel showing another embodiment of the present invention.

In FIG. 4, the end plate 3B has an inner surface of the pressure vessel formed in a planar shape so as to be perpendicular to the through hole 7A through which the control rod housing 7 passes, and an outer surface of the pressure vessel is also formed in a planar shape. Therefore, the plate thickness is thinner than that of the lower mirror 3A in the embodiment shown in FIG.

This lower mirror 3B is made by combining steel plates in a lattice shape.
A number of holes are formed through which the control rod housing 7 passes, and is supported by a reinforcing plate 9 fixed to the support skirt.

In FIG. 4, the lower mirror 3B and the stub tube 6 are integrally formed, and the stub tube 6 is lined with stainless steel or Inconel, which is the same as the embodiment shown in FIGS. 1 to 3.

According to the embodiment shown in FIG. 4, in addition to the effects achieved by the embodiments shown in FIGS. The thickness of the mirror 3B can be made thinner.

FIG. 5 is a sectional view of a main part of a nuclear reactor pressure vessel showing still another embodiment of the present invention.

The inner surface of the pressure vessel of the lower mirror 3C is formed into a planar shape orthogonal to the through hole 7A through which the control rod housing 7 passes, and the lower mirror 3C is formed integrally with the stub tube 6.
A short tube of stainless steel, Inconel or low alloy steel 1
0 are joined by butt welding. Lower mirror 3
C. The stub tube 6, the short tube 10, and the butt welded portions of the stub tube 6 and the short tube 10 are each provided with a lining 8.

The embodiment shown in FIG. 5 is effective when additional length is required for the stub tube 6 that is formed integrally with the head plate 3C in advance, and when butt welding the stub tube 6 and the short tube 10, Since it has a symmetrical rotational structure, automatic welding can be applied, and welding man-hours and time can be significantly reduced.

In the embodiment described above, the end plates 3A to 3C and the stub tube 6 are each formed integrally, but the end plates 3A to 3C and the stub tube 6 may be joined and fixed by welding. In this case, the mirror plate 3
In A to 3C, the inner surface of the pressure vessel is formed into a flat shape, so the groove shape of each stub tube 6 is the same at each position on the circumference, and the groove shape of each of the many stub tubes 6 is the same. Therefore, it is easy to apply automatic welding, and the number of welding steps can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, since the inner surface of the container in the lower mirror is formed into a flat end plate so as to be perpendicular to the hole axis of the control rod housing through hole, the end plate and the stud tube are integrated into one body. Since the forming process is a two-dimensional work, it is easy to use automatic machines to reduce the number of man-hours and time required for the forming process, and when the head plate and the stud tube are joined and fixed by welding, each Since the groove shapes of the stub tubes are the same and the work is two-dimensional, the number of welding steps and time can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a BWR type nuclear reactor pressure vessel showing an embodiment of the present invention, FIG. 2 is a sectional view of the main part of FIG. 1, and FIG. 3 is a detailed sectional view of section A in FIG. 2. Fourth
5 is a cross-sectional view of a main part of a BWR reactor pressure vessel showing another embodiment of the present invention. FIG. Figure 6 is an overall configuration diagram of a conventional BWR reactor pressure vessel, Figure 7 is a sectional view of the main part of Figure 6, Figure 8 is a detailed sectional view of section B in Figure 7, and Figure 9 is Figure 7. A of
-A arrow view. 1... Upper lid, 2... Fuselage, 3A to 3C... End plate, 4... Lower mirror petal, 5... Shroud support, 6... Stud tube, 7... Control rod housing, 8... Inner lining, 9... ...Reinforcement plate, 10...
Short tube, 11...Lower mirror, 12...Lower mirror dome, 13
...Statistic tube, 14...Inconel overlay layer.

Claims (1)

[Claims] 1. A nuclear reactor pressure vessel comprising an upper mirror, a body, and a lower mirror in which a control rod housing through hole is formed,
The reactor pressure vessel is characterized in that the lower mirror includes a mirror plate formed in a planar shape so that the inner surface of the pressure vessel is perpendicular to the hole axis of the control rod housing through hole. 2. The reactor pressure vessel according to claim 1, wherein the head plate is integrally formed with a stub tube for fixing to the control rod housing. 3. The nuclear reactor pressure vessel according to claim 1, wherein the stub tube integrally formed on the end plate and the end plate are each provided with a corrosion-resistant lining. 4. The reactor pressure vessel according to claim 1, wherein the lining is made of stainless steel or Inconel. 5 The pressure vessel outer surface side of the end plate is formed in a planar shape so as to be perpendicular to the hole axis of the control rod housing through hole, and the end plate has a hole for penetrating the control rod housing on the planar end surface side. A nuclear reactor pressure vessel according to any one of claims 1 to 4, which is provided with a reinforcing member.