JPS5894677A - Steam-leakage suppressing apparatus for main steam stop valve - Google Patents

Abstract

PURPOSE:To prevent leakage of steam at the time when main steam stop valves are closed, by connecting a water feeding means to the part of a main steam pipe located on the upstream side of the main steam stop valves for feeding water to the main steam pipe when the main steam stop valves are closed, to such an extent that the part where a poppet and the body of the main steam stop valves are held in contact with each other can be sealed by water. CONSTITUTION:While a nuclear reactor is operated normally, a water stop valve 21 is closed and both of main steam stop valves 5, 6 are opened. On the other hand, in case that a main steam pipe 9 is damaged at a position 10 located on the side of a turbine, the main steam stop valves 5, 6 are both closed and a water stop valve 22 is opened to feed water from a pressure water source 20 via a water feed pipe 22 to the part of a main steam pipe 7 located upstreams of the first main steam stop valve 5 and to thereby effect water sealing at the region where a poppet 18 and the body 17 of the valve are held in contact with each other. With such an arrangement, it is enabled to prevent leakage of steam from the main steam stop valves 5, 6 by the function of sealing water.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a device for completely suppressing main steam leakage by increasing the sealing performance of a main steam isolation valve seat when a main steam pipe of a boiling water nuclear power plant breaks.

Technical Background of the Invention In a boiling water nuclear power plant, as shown in Figure 1, reactor water (2) is contained in the shell of a reactor pressure vessel (1), and a VC reactor core (3) is inside the reactor water (2). It's submerged.

During normal operation of the nuclear reactor, uranium atoms contained within the reactor core (3) undergo nuclear fission and generate heat.

This heat causes the reactor water (21) to boil and generate steam.

This steam has a pressure of about 70 atmospheres, passes through the space (4) of the reactor power vessel (1), and enters the main steam pipe (1), +8), 191, which is divided by the main steam isolation valves (5), (6).
It passes through it and reaches a turbine (not shown below), which turns the blades of the turbine and operates the generator.

The fuel pellets of the fuel rods (not shown) in the upper part of the reactor core (3) are usually wrapped in a Zircaloy cladding tube, so that radioactive materials produced by nuclear fission during reactor operation are confined therein. . However, among the many fuel rods in the reactor core (3), there is a possibility that there may be slight damage to the Zircaloy-covered ffi and tubes, and during normal reactor operation, fuel can be removed through this minute damage. There is a possibility that the radioactive wJ substance in the pellets leaks into the reactor water (2), and the reactor water (2) is contaminated with radioactivity.

Main steam pipe (power) at the junction from the reactor pressure vessel (1) to the first main steam isolation valve (5) and the first and second main steam isolation valves (5)
The main steam pipe (8) between (6) and (8) have a dramatic design,
Although the rupture is unlikely, the second main steam isolation valve (6)
The main steam pipe (9) closer to the turbine may break for some reason during normal operation of the reactor. If the main steam 'ef (91) of this turbine port 9 is ruptured, the steam will violently flow out from the rupture port (10).Then, the pressure inside the reactor pressure vessel (1) will decrease,
If there is even slight damage to the cladding tube VC of a fuel rod, radioactive materials within the fuel rod will blow out into the reactor water (2). If this is released from the fracture, it will expose the public to a large amount of radiation, so main steam isolation valves (5) and (6) are installed.
When the main steam '# (91) breakage is detected, approximately 5
It will close in seconds. Therefore, the main steam isolation valves (5) and (6) are required to have a low leakage rate.

Problems with the Background Art By the way, the main steam isolation valve is designed so that the internal fluid is flush with steam.
+, compared to liquid, /-le π+ according to notebook VC is 10
It is technically difficult to make 0≠415. This will be explained with reference to all the drawings. Figure 2 shows the main steam isolation valve (5+,
In the elevation view of (6), both Fig. 3 and conduit Fig. 4 are fully enlarged sectional views of the part A in Fig. 2 when the main steam isolation valve is closed, and Fig. 3 is a fully enlarged cross-sectional view of the part A in Fig. 2 when the main steam isolation valve is closed. In the case of steam, FIG. 4 is fully shown in the case of water. In these figures, (12
1 is the operating section, 04 is the 1 drive section, 0 is the bonnet, (1
5) Inlet side body, (I61 is outlet side body, (17
) is the body, f181U poppet. However, the physical properties of water are much higher density and higher viscosity than steam. Therefore, as shown in Fig. 3, the fluid 0υ consisting of steam may easily leak from the slight gap between the seat surface where the poppet (IgJ and the body circle are in contact), and furthermore, If the adhesion is impaired due to the adhesion of fine dust to the water, there is a risk of leakage exceeding the allowable limit, whereas water is less likely to leak as shown in Figure 4. Since only steam was supplied to the conventional main steam isolation valves (5) and (6), there was a risk that a large amount of steam would leak from the main steam isolation valves f51 and (61).

Object of the invention The object of the invention is to improve the steam leakage prevention performance of the main steam isolation valve.
The purpose of the present invention is to provide a fully designed main steam isolation valve steam leakage suppression device.

Summary of the Invention In the present invention, water-gold is injected into the main steam pipe upstream of the main steam isolation valve to the extent that the contact area between the poppet and the body of the main steam isolation valve is water-sealed when the main steam isolation valve is closed. By connecting a water injection device, steam leakage is prevented when the main steam isolation valve is closed.

Embodiment of the Invention Hereinafter, an embodiment of the present invention will be described with reference to FIG. In this example, the reactor pressure vessel (1)
Reactor water (2) is contained in the reactor water (2), the reactor core (3) is submerged in water, and steam flows into the space (1) of the reactor pressure vessel (1).
4) to the main steam isolation valve (5) shown in Figures 2 to m4.
), (6) main steam pipe (7).

18+, (The first main steam isolation valve (
5) From 7 (main steam pipe (on the Ar side), main steam isolation valve (
Fil, (6) its main steam isolation valve (51,
(6) A water injection device consisting of a solid water injection pipe with a water injection isolation valve Qυ connected to a pressure water source (21) that injects enough water to seal the contact area between the poppet 0 barrel and the body 07). It is characterized by The above-mentioned pressure water source (20 is clean water stored in a tank (not shown) (condensate water from the turbine system can be used) can be easily obtained by applying Calo pressure with all pumps.

Next, the effect will be explained.

During normal reactor operation, the water injection isolation valve (21) is closed and the amphibious steam isolation valve (51, +6+ 'e is opened.If this causes a break in the main steam pipe (9) near the turbine, , Amphibious steam isolation valve (5), (61'z is closed, water injection isolation valve Q is opened, and water injection pipe f2 is connected from the pressure water source (decoy).
2) Inject water into the main steam pipe (forced) upstream of the first main steam isolation valve (5) through the lr to water-seal the contact area between the poppets (1 to 1 and body a'7). As shown in FIG. 4 and explained above, leakage of steam from the main steam isolation valves (51, (6)) is suppressed by the sealed water.

However, the present invention is not limited to the embodiments described above and shown in the drawings; for example, water injection may be performed using either one of the two main steam isolation valves (5) and (6). Of course, it can be implemented in various ways without changing its gist, such as just doing the same thing.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the contact portion between the poppet and the body of the main steam isolation valve is water-sealed in the main steam pipe upstream of the main steam isolation valve when the main steam isolation valve is closed. By fully connecting the water injection equipment that injects water to a certain level, the main steam isolation valve is sealed with water, preventing leakage of radioactively contaminated steam in the reactor pressure vessel. This has the effect of significantly increasing the reliability of the reactor protection system and safety system, which in turn improves the safety and reliability of the boiling water nuclear power plant as a whole.

[Brief explanation of the drawing]

FIG. 1 is a piping system diagram showing a steam leakage suppression device for a conventional main steam isolation valve, and FIG. 2 is an elevational view showing a conventional main steam isolation valve (used for C and also used in an embodiment of the present invention). Figures 3 and 41 are enlarged sectional views of section A in Figure 2 showing sealing performance against different fluids, and Figure 5 is a piping diagram showing an embodiment of the steam leakage suppression device for the main steam isolation valve of the present invention. It is a system diagram. l... Reactor pressure vessel 5.6... Main steam isolation valve 7
．． 8.9...Main steam pipe 17...Body 18...
・Poppet 20...Pressure water source 21...Water injection piping 22...Water injection isolation valve 23
...Water injection device agent Patent attorney Inoue - Male Commissioner of the Patent Office Shima 1) Haruki Tono1. Display of the case 1982 Patent Application No. 190535 2 Name of the invention Steam leak suppression device for main steam isolation valve 3 Person making the amendment Relationship to the case Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. (1 other person) ) 4. Agent Address: 4-41-11 Kamata, Ota-ku, Tokyo 144 - Tsunoda Building Subject of Amendment 11 Drawing 6, Contents of Amendment (1) Corrections will be made as per the Figure 4 interest sheet. Above is Figure 4-515-

Claims (1)

[Claims] In a device for suppressing main steam leakage when the main steam isolation valve is closed in a main steam pipe with a main steam isolation female valve installed in the reactor pressure vessel of a boiling water reactor, the main steam pipe on the upstream side of the main steam isolation valve When the main steam isolation valve is closed, the poppet of the main steam isolation valve contacts the body F! ivI A steam leak suppression device for a main steam isolation valve, which is characterized in that it is connected to a water injection device that injects water to the extent that water is completely sealed.