JPS5896289A - Gasket of internal 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 The present invention relates to an internal pump installed at the bottom of a nuclear reactor pressure vessel, which is left in high-temperature water inside the reactor during operation of the reactor, and during maintenance and disassembly of the pump when the reactor is shut down. The present invention relates to a metal gasket suitable for preventing leakage of reactor cooling water.

The internal pump is installed at the bottom of the reactor pressure vessel l as shown in Figure 1 and is a pump with nine wet pumps.As shown in Figure 2, the internal pump consists of an impeller 2, a shaft 3, a diffuser 4, and a stretch tube. 5 is reactor pressure vessel 1
The motor housing 6, which incorporates the radial bearing, thrust bearing, motor, etc., has a structure that can be removed upward and removed downward. When removing the motor housing 6 or attaching the IRI, the flange 3a near the upper end of the shaft 3 and the top 5a of the stretch tube 5 come into contact to seal the reactor cooling water in the reactor pressure vessel 1. The water leaking between the shaft 3 and the stretch tube 5, and the water leaking between the diffuser 4 and the reactor pressure vessel 10 are further sealed by activating the auxiliary seal 7 with pressure water from the outside, and the water leaking between the diffuser 4 and the reactor pressure vessel 10 is sealed. The motor housing 6 can be taken in and out until the pressure vessel 1 is filled with water.

The stretch tube top 51 and the shaft 7 flange 3a are machined to be particularly precise and smooth, and the high-level machining is far apart, so it is necessary to prevent leakage between the upper end surface 1a of the bottom of the reactor pressure vessel and the lower end of the diffuser 4a. , it is necessary to attach some kind of gasket to this part.

This gasket is required to have high heat resistance and corrosion resistance because (1) it is left in water at a high temperature of nearly 300 C during operation of the nuclear reactor. In addition, (2) as shown in FIG. 2, the diffuser 4 is stretched by a thin stretch tube 5 and fixed against the reactor pressure vessel 1, so if the installation compressive force required for the gasket is large, A large initial tensile force must be applied to the stretch tube 5, which may impair safety. Therefore, the gasket needs to have sufficient sealing function with low installation compression force.

Furthermore, (3) the gasket must have a structure that can be fixed to the diffuser 4 in order to prevent the gasket from falling into the reactor pressure vessel when the diffuser 4 is installed or removed.

Note that (4) the performance required of the gasket is to seal the reactor cooling water at room temperature to a pressure of Z3Kf/C11K” when the motor housing 6 is installed or removed, but (5) in the event of a reactor accident, , temperature 300C
It is desirable to be able to prevent leakage of reactor cooling water at a high temperature and pressure of about 80 Kg/cm''G.

Conventional metal spiral gasket, metal medium g! The O-ring satisfies the requirements (1), +4), +5) above, but does not satisfy the requirements +2), (31), and the metal corrugated gasket satisfies the requirements (1), (2+ , the asbestos gasket satisfies the requirement (4), but (<31. (51) was not satisfied.
, (4) is satisfied, but 11), +3), +5)
However, the conventional technology has not been able to supply a gasket that satisfies all of the required items.

The present invention has been made in view of the structure, function, and performance required of such internal pump gaskets, and has the following features:
It is an object of the present invention to provide a gasket that satisfies all of the requirements (1) to (5) above, is compact, and has high reliability.

The present invention relates to a gasket interposed between the upper end surface of the bottom of a reactor pressure vessel and a diffuser of an internal pump, in which a sealing portion has a semicircular arc cross-sectional shape, the sealing portion forming a semicircular recess. It is recommended that the convex portion be fixed so that it is located on the high pressure side and the convex portion is located on the low pressure side.

Hereinafter, five embodiments of the present invention will be described with reference to FIG. #!
Figure 3 is an enlarged view of the joint between the bottom of the reactor pressure vessel 1 and the diffuser 4. 5 is a stretch tube that brings the diffuser 4 into pressure contact with the pressure vessel l. 11 is a ring-shaped chamber bored into diffuser 4, and this one! In ll, the seal part has a semi-circular cross-sectional shape, and a gasket 8 in the form of a cross-section is fixed to the diffuser 4 with a bolt 9 via a retaining ring of 10 feet so that the high pressure individual is located in the concave part and the low pressure part 111B is located in the convex part. ing. Gasket) 8Fi The gasket 8, which seals from the high pressure mA to the low pressure side B at the upper part 81 and lower part 8b, is made of corrosion-resistant and heat-resistant stainless steel, nickel-based alloy, or the like. By the way, if the surface of the gasket 80 is silver plated, the sealing performance will be improved. Before installing the gasket 8Fi, it has the cross-sectional shape shown in Figure 4. Since the cross section is semi-circular and thin, the third
It is easy to create the state shown in the figure. (9) In the event of a nuclear reactor accident, the high pressure @A cooling water increases the sealing surface pressure of the gasket 8 and improves the sealing performance, so leakage from the high pressure i11]A to the low pressure 1i11B can be avoided.

As explained above, according to the present invention, the above (11-
(5) Be able to satisfy all items. Further, since the metal gasket of the present invention has no stress concentration portion, the risk of breakage is low and it has high reliability P, t-.

Moreover, it is compact, making it ideal for use as a gasket to seal reactor cooling water between the internal pump diffuser and the reactor pressure vessel.

[Brief explanation of the drawings] Fig. 1 is a longitudinal cross-sectional view of the internal pump, and Fig. 2 is a longitudinal cross-sectional view of the internal pump.
Internal pump disassembly 1st figure explanatory diagram, total 3 diagrams, #!
FIG. 4 is a vertical cross-sectional view of the metal gasket of the present invention, and the third
The figure shows the installed state, and Figure @4 shows the free state. l... Reactor pressure vessel, 2... Inves 2, 3...
Shaft, 4... Diffuser, 5... Stretch tube. 6...Motor housing, 7...Auxiliary seal, 8.
...Metal gasket. Figure 2￥J 3 Figure 4

Claims (1)

[Claims] In the gasket interposed between the upper end surface of the bottom of the reactor pressure vessel and the diffuser of the internal pump, the sealing part forms a semicircular cross-sectional shape and is an annular gasket, and the semicircular concave part is a gasket in which high pressure is detected. A gasket for an internal pump, wherein the gasket is fixed to the diffuser so that the convex portion is located on the low pressure side.