JPS6316295A - Earthquakeproof supporter for nuclear reactor built-in type wet motor pump - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an earthquake-resistant support device for a wet motor pump built into a nuclear reactor.

(Prior technology) A reactor built-in wet motor pump is usually called an internal pump, and this internal pump is installed at the bottom of the reactor pressure vessel and supplies reactor water, which is a coolant, to the reactor core. It is configured to serve.

A conventional example of such an internal pump will be explained with reference to FIG. In the figure, a pump impeller 2 for driving reactor water, which is a coolant, is disposed inside the reactor and connected to a wet motor section 10 via a pump shaft 8. Most of the pump shaft 80 and the wet motor section 10 are housed in a motor casing 9, and the casing neck section 4 of the casing 9 has a root section 3 which is welded to the nozzle section of the reactor pressure vessel. are combined with.

Therefore, since the internal pump with a casing has a cantilever structure with the root 3 as a fixed end, the stress in the root 3 of the casing will increase when excessive vibration occurs. have.

With this casing, in order to reduce the stress on the root part 3,
A locking portion 5 is provided on a sleeve 7 extending downward from the casing neck portion 4 or the lower part of the outer wall of the reactor pressure vessel.

This locking portion 5 has a fitting structure at room temperature, but is configured so that a minute gap is created during normal operation of the nuclear reactor. By the way, if the casing 9 undergoes a large lateral vibration during an earthquake, contact will occur at the locking portion 5 across the above-mentioned gap. As a result, the movement of the casing 9 is suppressed, and the moment, stress, etc. applied to the root portion 3 of the casing, which is the most stressed part, can be reduced. As shown in FIG. 4, the locking portion 5 provided on a sleeve 7 extending downward from the lower part of the outer wall of the reactor pressure vessel can also reduce moment, stress, etc. in the same way as shown in FIG. 3 above. . There is a linear relationship between the gap between the locking portions 5 and the maximum stress that can occur in the root portion 3 of the casing during an earthquake, as shown in FIG.

However, because conventional locking parts are made of the same carbon steel (SFVV3) as the casing and reactor pressure vessel sleeve, there is a risk of surface corrosion, rust, etc. occurring during the life of the plant. Like corrosion.

When rust or the like occurs, the gap becomes larger than the gap at the initial stage of plant operation. For example, if a gap equal to the gap at the beginning of the plant life occurs due to corrosion, considering both the casing side and the reactor pressure vessel outer sleeve side, the gap at the end of the plant life will be three times the gap at the beginning of the plant life. With a casing, the stress that can occur at the root is also tripled. This means that the earthquake resistance function of the locking portion is significantly reduced. It is extremely important for the internal pump support device to function effectively that the gap does not expand during plant operation and remains constant.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to install a pump in a sleeve extending downward from the pump casing neck or the lower part of the outer wall of the reactor pressure vessel during plant operation. It is an object of the present invention to provide an earthquake-resistant support device for a jet motor pump built into a nuclear reactor, in which the gap between the locking parts does not expand due to corrosion or the like.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a sleeve extending downward from the lower part of the outer wall of the reactor pressure vessel and a sleeve attached to the lower part of the outer wall of the reactor pressure vessel. In a wet motor pump built into a nuclear reactor, which is arranged so as to have a gap between the pump casing and the pump casing, stainless steel locking parts are welded to the neck part of the pump casing in a ring shape around the entire circumference or in several places. It is characterized in that stainless steel is welded to the abutment surface of the sleeve that faces the locking portion.

(Function) According to the seismic support device for a wet motor pump built into a nuclear reactor of the present invention, the locking portion provided on the sleeve extending downward from the pump casing neck portion or the lower part of the outer wall of the reactor pressure vessel and the contact surface thereof. Since stainless steel is used, corrosion occurs during plant operation.

It is possible to prevent the occurrence of rust, etc., and thereby maintain the gap at the initial stage of plant operation.

(Example) Embodiments of the present invention will be described with reference to the drawings.

FIG. 1(a) is a sectional view of an embodiment of the present invention, and FIG. 1(b) is a sectional view of an embodiment of the present invention.
are partially detailed cross-sectional views, and as shown in these figures, a pump impeller 2 that drives reactor water is installed in the reactor, and is connected to a wet motor section 10 via a pump shaft 8.
is connected to. Most of the pump shaft 8 and the wet motor section 10 are housed in a casing 9, and the casing neck section 4 of the casing 9 is connected to a nozzle section at the lower part of the outer wall of the reactor pressure vessel by welding.

In general, the members of the locking portion 5 and the locking portion contact surface 6 are made of stainless steel, and this stainless steel is welded to the carbon steel of the casing 4 or the reactor pressure vessel outer sleeve 7. Further, the locking portion 5 and the locking portion abutment surface 6 are surface-finished by welding so that they fit into contact at room temperature.

Next, the operation of this embodiment will be explained.

At room temperature, the locking portion 5 and the locking portion contact surface 6 have a fitting structure, but during normal operation of the nuclear reactor, a small gap is created between them due to the influence of internal pressure and heat. For example, if a large lateral vibration occurs during nuclear reactor operation, such as occurs during an earthquake, the locking part 5 and the locking part contact surface 6 will come into contact with each other, so the casing is the most severe part in terms of vibration and stress. The attachment can reduce the stress on the root portion 3.

By the way, the relationship between the gap of this locking part and the maximum stress that can occur in the root part of the case with a casing during an earthquake is explained in the fifth section already explained.
As shown in the figure, the two are in a line shape relationship.

Therefore, it is important to keep the gap between the locking portions as small as possible. Conventionally, the proposed locking portion 5 and locking portion contact surface 6 are made of the same carbon steel as the casing and the reactor pressure vessel sleeve, as shown in FIGS. Under the influence of these factors, the initial gap of the locking portion may gradually expand, and the gap at the end of the plant life may become significantly larger than the initial gap.

In this embodiment, stainless steel is used for the locking part 5 and the locking part contact surface 6 to eliminate the risk of corrosion, rust, etc., and the structure is such that the above-mentioned gap does not expand beyond the initial gap of plant operation. be.

FIG. 2(a) is a sectional view of another embodiment of the present invention, and FIG. 2(b) is a sectional view of another embodiment of the present invention.
) is a partially detailed cross-sectional view of the same, and as shown in these figures, even if the locking part 5 is provided on the RPV outer sleeve 7 side and the locking part contact surface 6 is provided on the casing 4 side, the same result as in the above embodiment is obtained. It has a great effect.

[Effects of the Invention] As described above, according to the present invention, the initial gap can be maintained for the locking part gap during the life of the plant. This results in an excellent effect in that the present support device can significantly improve its ability to withstand B damage and its reliability.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a sectional view and a partially detailed sectional view of one embodiment of the present invention, and FIGS. 2(a) and 2(b) are
b) is a sectional view of another embodiment of the present invention and a partially detailed sectional view thereof, FIGS. 3 and 4 are sectional views of a conventional internal pump, and FIG. 5 is a sectional view of a locking part gap and a casing. Attached is a diagram for explaining the relationship between the root and the maximum stress during an earthquake. 1... Reactor pressure vessel wall 2... Pump impair 3... Root with casing 4... Casing neck part 5... Locking part 6... Locking part contact surface 7...・Reactor pressure vessel external sleeve 8...Pump shaft 9...Casing 10...Wet motor 11...Welding department agent Patent attorney Noriyuki Ken Yudo Hirofumi Mitsumata °° Figure 1 Ca) 2 Figure 3 Figure 4 Same as Figure 5 ↓ Figure 5

Claims (1)

[Claims] (1) In a reactor built-in wet motor pump arranged so that there is a gap between a sleeve extending downward from the lower part of the outer wall of the reactor pressure vessel and a pump casing attached to the lower part of the outer wall of the reactor pressure vessel, A nuclear reactor characterized in that a locking part made of stainless steel is welded to the neck part of the pump casing all around the ring shape or at several places, and stainless steel is welded to the abutting surface of the sleeve facing the locking part. Earthquake-resistant support device for built-in wet motor pump.