JPS58113892A - Main steam isolation valve leakage suppression device - Google Patents

Abstract

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

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a main steam isolation valve leakage suppression system for a boiling water nuclear reactor.

Technical background of the invention and its problems In a boiling water nuclear power plant, water, which is a coolant, is turned into steam in a boiling water reactor, and this steam is sent to a turbine (= feed generator) through a main steam pipe. The main steam pipe (- indicates that a plurality of main steam isolation valves are installed, but the turbine side main steam pipe downstream of the most downstream main steam isolation valve may be structurally broken.

If the main steam pipe ruptures for some reason during the operation of this nuclear reactor, the coolant inside the reactor may flow out from the rupture port, and fission products may be released directly into the power plant premises. Therefore, the main steam pipe flow generated by the rupture is maximum,
Signals such as main steam pressure images are used to automatically close the main steam isolation valves installed on both sides of the main steam pipe's penetration of the reactor containment vessel to suppress the release of coolant. After the isolation valve is closed, the reactor pressure is maintained close to the rated operating pressure (= maintained), and because the pressure is high (2. There is a possibility that a small amount of reactor steam may leak through the main steam isolation valve. The steam isolation valve leakage suppression device has three main steam isolation valves interposed in series from the main steam pipe (-1 reactor side to the turbine side), and the third main steam isolation valve Since there is a probability of rupture in the main steam pipe on the turbine side of the valve, the front main steam pipe between the first main steam isolation valve and the second main steam isolation valve,
Or, the rear main steam pipe between the second main steam isolation valve and the third main steam isolation valve (by releasing the leaked steam into the suppression pool (second), it is passed through the third main steam isolation valve to the rupture port). Although efforts have been made to further reduce the amount of steam leaking from the system, it is still considered insufficient.

OBJECTS OF THE INVENTION An object of the present invention is to provide a main steam isolation valve leakage suppression device that suppresses the amount of steam leaking from a rupture port through the main steam isolation valve to an extremely low level after the main steam isolation valve is closed in the event of a main steam pipe rupture accident. There are two things.

Summary of the Invention In the present invention, a main steam pipe connecting a boiling water nuclear reactor and a turbine (= a plurality of main steam isolation valves are connected in series), and when the main steam pipe on the turbine side is ruptured, the first main steam isolation valve An air pipe that supplies high-pressure air from a high-pressure air supply source is installed in the main steam pipe between the main steam pipes, and when the main steam pipe on the turbine side breaks, the space between the main steam isolation valves is filled with high-pressure air, and steam leaks from the main steam isolation valve. suppress as much as possible.

Embodiment of the Invention Hereinafter, one embodiment (two embodiments) of the present invention will be described with reference to the drawings.

A reactor side main steam pipe (1, ), penetrate the reactor containment vessel wall (3), connect to the second main steam isolation valve (4), and pull out the rear main steam pipe (13) from this second main steam isolation valve (4). 3rd main steam isolation valve (5)
The turbine side main steam pipe (14) is pulled out from this third main steam isolation valve (5) and connected to the turbine (not shown). The compressor (6) and the high pressure air storage tank (power) are connected through the first air pipe (81).

Pull out the second air pipe (80) from the high-pressure air storage tank and install a high-pressure air supply valve (9) in it, and install a safety valve in the third air pipe (fourth air pipe (84) branched in the middle of 80). 0 [.The third air pipe (80) further branches into the fifth and sixth air pipes (85), (8,), and the fifth air pipe (8,) is connected to the reactor containment vessel wall ( 3) is connected to the front main steam pipe (10) via the first main steam pipe connection valve αD.The sixth air pipe (8ρ is connected to the second main steam pipe connection valve a)
Connect to the rear main steam pipe (1◇) via 2.

Next (explaining the two effects.

In the figure, the black valves are closed during normal operation, and the white valves are open during normal operation. Reactor containment vessel wall (3
) When the main steam pipe (14) on the turbine side, for example, breaks outside the main steam pipe (14), the break port is opened to the atmosphere, and steam is rapidly released from the break port.

The main steam pipe steam flow rate increases rapidly, and a signal indicating a large main steam pipe steam flow rate is generated. This signal causes the first, second, and third
The main steam isolation valves (2), (4) and (5) are closed and attempt to stop the release of coolant from the rupture.

However, even if a rupture is detected and the reactor is scrammed, the reactor is still maintained at high pressure, so the main steam isolation valves (2), (4), (5) Internal steam leaks out and is released little by little from the fracture opening. Therefore, high pressure air is always stored in the high pressure air storage tank (7). The high-pressure air compressor (6) is activated in response to a signal indicating that the main steam pipe has broken due to a large steam flow rate, etc., and further blows high-pressure air into the high-pressure air storage tank (7). Open the air supply valve (3) and each main steam isolation valve (2), (4), (
5) has completed closing, the two-way steam pipe connection valve α1), α
open, clean high-pressure air is injected into the front main steam pipe (10) and the rear main steam pipe (13), and the double steam pipe (IJ,
(13) Maintain high pressure inside. Therefore, when the reactor is kept at fairly high pressure, each main steam isolation valve (2+,
(4), (5) (2) Suppressing the differential pressure (from 2), steam leakage can be reduced, and when the reactor pressure is reduced to a certain extent and becomes lower than the pressure of high-pressure air,
Since high pressure air leaks to the reactor side through the first main steam isolation valve (2), leakage of steam from the reactor is prevented.

In addition, in the above, each main steam isolation valve (2), (4)
, (5) is inoperable (in order to deal with both cases, the first main steam pipe connecting valve (Ill.
After the first main steam isolation valve (2) on the most upstream side (two main steam isolation valves) is closed, it opens with a slight delay, and the second main steam isolation valve on the downstream side
The main steam pipe connection valve az will be opened with a slight delay after the third main steam isolation valve (5) located on the most downstream side has been closed. Safety valve H helps prevent overpressure.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but may include the following without changing the gist thereof:
Of course, it can be implemented with various modifications.

Effects of the Invention As described above, according to the present invention, high-pressure air is injected into the main steam pipe between a plurality of main steam isolation valves in a turbine-side main steam pipe rupture accident outside the reactor containment vessel. By doing so, the pressure is maintained at a high pressure, so that a main steam isolation valve leakage suppressing device that effectively suppresses leakage of steam from the main steam isolation valve can be obtained.

[Brief explanation of the drawing]

The drawing is a pipe system diagram showing an embodiment of the main steam isolation valve leakage suppressing device of the present invention. ■0. ...Reactor side main steam pipe 1. ...Front side main steam pipe 13...Rear side main steam pipe 14...Turbine side main steam pipe 2.4.5...First, second, third main steam isolation valve 3... Reactor containment vessel wall 6... High pressure air compressor 7... High pressure air storage tank 8 which is a high pressure air supply source,
~86...Air piping 9...High pressure air supply valve 1
0...Safety valve 11.12...1st and 2nd main steam pipe connection valve agent
Patent Attorney Inoue - Male

Claims (2)

[Claims] (1) A plurality of main steam isolation valves are interposed in series in the main steam pipe connecting the boiling water reactor and the turbine, and when the main steam pipe on the turbine side breaks, the main steam pipe between the main steam isolation valves; two high pressure A main steam isolation valve leakage suppression device characterized by being provided with air piping that supplies high-pressure air from an air supply source. (2) Three main steam isolation valves are connected in series, and air piping from a high-pressure air supply source is branched to the main steam pipe between each main steam isolation valve and connected via a main steam pipe connection valve, and the upstream side The main steam pipe connection valve opens with a slight delay after the most upstream main steam isolation valve closes, and the downstream main steam pipe connection valve opens with a slight delay after the most downstream main steam isolation valve closes. The main steam isolation valve leakage suppressing device according to claim 1, characterized in that the main steam isolation valve leakage suppressing device is opened by holding the main steam isolation valve open.