JPH03238398A - Main steam pipe plug of boiling water reactor and method for testing leakage of main steam isolation valve using the same - Google Patents

Abstract

PURPOSE:To simplify the leak test of a main steam isolation valve by mounting a main steam line (pipe) plug to the main steam line between a reactor pressure vessel and the main steam isolation valve. CONSTITUTION:After a main steam escape safety valve is detached, a bag body 10 is inserted in the opening part of a main steam escape safety valve tube base 5, which is fixed to a flange 8 by bolts. Next, a nitrogen gas cylinder 12 is connected to an air guide pipe 9 to open a source-valve 11. By this operation, nitrogen gas is guided to a main steam pipe plug, that is, the bag body 10 through the air guide pipe 9. The main steam pipe plug 10 expands and closely comes into contact with the inner wall of a main steam pipe 4 to complete sealing. Herein, the source-valve 11 is fully closed to cut off the connection with the nitrogen gas cylinder 12. When a main steam line 4 is isolated from a reactor 3, compressed air is supplied to the main steam line between the main steam pipe plug 10 and the main steam isolation valve 6 to make it possible to perform the leak test of the main steam isolation valve 6 apart from in-pile work.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a main steam line that extends from a boiling water reactor pressure vessel and is detachably attached to a main steam line that is provided with a main steam isolation valve in the middle. with line plug.

This article relates to a main steam isolation valve leakage test method using this method.

[Prior Art] A conventional structure in the vicinity of a nuclear reactor pressure vessel including a main steam line is generally constructed as shown in FIG. That is, a plurality of main steam lines 4 come out from the upper part of the furnace (M child reactor pressure vessel) 3, and a main steam relief safety valve (however, the illustration of the valve itself is omitted in the figure) is connected to these lines. (Only the nozzle stub 5 on which the valve is attached is shown) and the main steam isolation valve 6
is provided.

During periodic inspections, please refer to Japanese Patent Application Laid-Open No. 58-166290,
As disclosed in Publication No. 56-30693, etc.,
A main steam line plug is detachably attached to the main steam nozzle of the reactor pressure vessel 3 to which the main steam line 4 is connected from inside the pressure vessel 3. Furthermore, the fifth
In the figure, a mounting M2 for attaching the main steam line plug is shown.

Work inside the reactor and work related to the main steam pipes accompanying periodic inspections of nuclear reactors as described above have conventionally been carried out according to the procedure shown in FIG. Among the main steam pipe-related work, the main steam isolation valve 6 is inspected by performing a leakage test before and after disassembling the main steam isolation valve. The leakage test is carried out by attaching a main steam line plug to the main steam pipe inlet (main steam nozzle) from inside the furnace, fully opening the main steam isolation valve 6, and applying air pressure between the two.

The overall process length of regular inspections is determined by a series of sequences that mainly involve in-furnace work (in other words, the in-furnace work constitutes a so-called critical bus), so a sequence is established that gives priority to the in-furnace work. When the reactor pressure vessel top cover is removed, the steam dryer is removed, and the steam separator is removed as shown in FIG. 6, the fuel can be moved from inside the reactor. However, the steam separator and fuel cannot be moved in the atmosphere because they are high-dose equipment. Therefore, in conjunction with the removal of the steam separator, the water level is raised from the normal water level below the main steam pipe to a full well above the main steam pipe, and these devices are handled underwater. However, when the water level rises, the inside of the main steam pipe becomes submerged, making it impossible to inspect the main steam isolation valve 6 starting with the leakage test. Therefore, after removing the steam separator, a main steam line plug is installed at the inlet of the main steam pipe inside the reactor pressure vessel 3 to isolate the inside of the reactor pressure vessel 3 and the main steam pipe 4.

After installing the main steam line plug, it is possible to perform a leakage test on the main steam isolation valve by draining the water accumulated in the main steam pipe and applying air pressure between the main steam line plug and the main steam isolation valve 6. Become.

On the other hand, a main steam relief safety valve is installed in the main steam pipe 4 between the main steam inlet and the main steam isolation valve.

The water valve is also removed from the main steam safety relief valve nozzle 5 having a flange structure for inspection, and a closing flange is attached to the nozzle 5 for a main steam isolation valve leakage test.

[Problem to be solved by the invention] As described above, in order to set up a work sequence that prioritizes the work inside the reactor, which is a critical bus, it is necessary to install a main steam line plug, and in the conventional technology, the main steam line The installation and removal of line plugs was included in the sequence of in-furnace work, so this was a critical bus.

Further, as shown in FIG. 7, in a boiling water reactor equipped with an internal pump 16, when inspecting the internal pump 16, the impeller shaft 17 is connected vertically to the wire 15 from the fuel exchanger 18. Lift it up and pull it out.
However, since the conventional main steam line plug installation structure has a ring-shaped structure along the inner wall of the furnace, it interferes with this during the above-mentioned extraction. Therefore, when a conventional main steam line plug is used, the main steam line plug must be removed in order to extract the impeller shaft 17. Furthermore, removal of this main steam line plug creates new process constraints on the main steam isolation valve 6 inspection work.

As described above, in the conventional technology of installing a main steam line plug inside the reactor, the installation and removal work becomes a critical path, which lengthens the work process and also hinders inspection of the internal pump of a boiling water reactor. There was a problem of process constraints to prevent this from occurring. Further, since the conventional main steam line plug is provided inside the furnace, that is, inside the pressure vessel, the installation and removal of the plug requires remote control using a jig or the like, resulting in poor workability.

Therefore, it is an object of the present invention to provide a method for easily performing a leak test of a main steam isolation valve, and another object of the present invention is to provide a method suitable for carrying out the above method, using equipment such as a jig. The purpose of the main steam line plug is to provide a main steam line plug that can be easily attached and detached without having to do so.

[Means for Solving the Problems] The present invention provides a main steam pipe plug according to each of claims 1 to 5, and also provides a main steam pipe plug according to claim 6 using the main steam pipe plug. An isolation valve leak test method is provided.

[Function] In the present invention, a leakage test of the main steam isolation valve can be performed in parallel with and separately from the work inside the reactor pressure vessel (work inside the reactor). In other words, by attaching a main steam line (pipe) plug to the main steam line (pipe) between the reactor pressure vessel and the main steam isolation valve, the main steam line is separated from the reactor pressure vessel. The main steam isolation valve can be tested for leaks by applying air pressure.

As described above, according to the present invention, testing of main steam isolation valves can be separated from in-furnace work, which is a critical path, and the testing process can be shortened. Moreover, since the main steam line plug can be installed and removed outside the furnace, no special equipment such as a jig is required.

The main steam line plug is removably attached to the nozzle stub of the main steam relief safety valve, so first the safety valve can be removed and the main steam line plug can be attached to the nozzle stub.

Preferably, the body of the main steam line plug is a bag body, and the bag body is connected to the main steam pipe between the reactor pressure vessel and the main steam isolation valve using, for example, the nozzle holder of the main steam relief safety valve. Insert into the tube. When pressurized gas, for example nitrogen gas, is supplied, the bag expands all the way into the main steam pipe and closes the chain pipe. In this way, the main steam isolation valve can be leak tested as previously described. Removal of the plug releases the fluid in the bag, reduces its volume, and pulls it out.

[Embodiment] In carrying out the present invention, the main steam line plug can be attached using any nozzle stub provided in the main steam line between the reactor pressure vessel and the main steam isolation valve. However, it is convenient to use the main steam relief safety valve nozzle. Therefore, in the illustrated embodiment, only an example in which the main steam safety relief valve is attached to the nozzle stub is shown.

Examples of the present invention will be described below.

Now, referring to Fig. 1, a main steam pipe (main steam line) 4 extends from the reactor (reactor pressure vessel) 3 as in the conventional system, and a main steam isolation valve 6 and a main steam relief safety valve are connected to this pipe. A nozzle 5 is provided. FIG. 1 shows a main steam line plug 7 installed in accordance with the present invention.

Details of the main steam line plug 7 are shown in FIG. That is, the plug is a bag body 10. which is configured to be inserted into the pipes 4 on both sides of the safety valve nozzle 5. The bag body is composed of a fluid guide pipe 9 for supplying fluid such as nitrogen gas to these bags, and a flange 8 supporting the fluid guide pipe. When using it, insert the bags 10, 10 through the opening of the main steam safety relief valve nozzle 5 after removing the main steam relief safety valve, and fix the main steam relief valve nozzle 5 and the flange 8 with bolts. . The flange 8 has a main valve 11. A fluid guide pipe 9 and a main steam pipe plug body or bag body 10 connected thereto are attached. After fixing the flange 8, the nitrogen gas cylinder 12 and the air guide pipe 9 are connected.

Open the main valve 11. Thereby, nitrogen gas is guided through the air guide pipe 9 to the main steam pipe plug or bag 10. The main steam pipe plug 1o expands and comes into close contact with the inner wall of the main steam pipe 4 to complete a seal.

At this point, the main valve 11 is fully closed and the connection with the nitrogen cylinder 12 is cut off. After the main steam line 4 is separated from the furnace 3 as described above, pressurized air is supplied to the main steam line between the main steam pipe plug 10 and the main steam isolation valve 6, and the work inside the furnace is started. Separately, a leakage test of the main steam isolation valve 6 can be performed.

Figure 3 shows the work sequence when using a simple main steam line plug installed in the main steam pipe as described above. It is only relevant. In other words, by satisfying the above-mentioned condition of installing the main steam line plug before performing the water head, it is basically possible to perform the work inside the furnace and the work related to the main steam pipe in parallel. Furthermore, it is entirely possible to satisfy the above conditions because there is sufficient time to reach the water head, and the work on the main steam pipe side will not become critical.

As shown in Fig. 3, according to this embodiment, there is no need to install a main steam line plug when working inside the furnace, and there is no need to drain water from the main steam pipe when working on main steam pipes. Therefore, the testing process can be significantly shortened.

Removal of the plug is performed in reverse order, and the main valve 11 is fully opened to release the internal pressure of the bag 10 to the atmosphere.

This causes the main steam pipe plug body, ie, the bag 10, to deflate. Then, loosen the bolts on flange 8 and remove the device.

FIGS. 4(a) and 4(b) show another embodiment of the main steam line plug. The device consists of a flange 8 and a closure plate 14 connected thereto. A guide 13 is installed in advance inside the main steam pipe 4 at the position of the nozzle stand. After removing the main steam relief safety valve, the closing plate 14 is lowered from the opening of the main steam relief valve stub 5 along the guide 13 in the main steam pipe 4. Then, the bolts on the flange 8 are tightened to bring the guide 13 and the closing plate 14 into close contact to complete the seal.

It is clear that the main steam line plug according to this embodiment can also be used in accordance with the embodiment shown in FIG.

[Effects of the Invention] As described above, according to the present invention, it is now possible to remove the installation and removal of the main steam line plug from the critical path, which was traditionally a critical path for in-furnace work, thereby shortening the periodic inspection process. You can. Furthermore, since it becomes possible to perform work related to the main steam pipe in parallel with work in the furnace, there is more time for work related to the main steam pipe.

In addition, the main steam line plug has a simple structure and can be manufactured at low cost, and can be installed on the main steam line outside the furnace using a nozzle stand, so there is no need for remote control using a jig or the like.
Removal workability is also easy.

Furthermore, the internal pumps of boiling water nuclear reactors with built-in internal pumps are inspected.

This has the advantage that it can be carried out without being interfered with by the main steam line plug.

[Brief explanation of drawings]

Fig. 1 is an overall front view showing an outline of an embodiment of the present invention, Fig. 2 is a side view showing an embodiment of a main steam line plug, and Fig. 3 shows a working procedure according to an embodiment of the present invention. 4(a) is a side view showing another embodiment of the main steam line plug, FIG. 4(b) is a front view thereof, and FIGS. 5 to 7 are views showing conventional examples. The figure is an overall front view showing the installation of the main steam line plug, Figure 6 is a diagram showing the work procedure, and Figure 7 is a diagram showing the work procedure.
The figure is a schematic front view when inspecting the internal pump. 3...Reactor (reactor pressure vessel) 4...Main steam line (pipe) 5...Main steam relief safety valve nozzle 6...Main steam isolation valve 7...Main steam line plug 8.・Flange 9...Fluid guide pipe 10...
Bag body (plug body) (1 other person) Fig. 1 Fig. 4 Fig. (0) (t) 1 Fig.

Claims (1)

[Scope of Claims] 1. With respect to a main steam pipe that extends from a reactor pressure vessel and has a main steam isolation valve in the middle thereof, a midway portion of the main steam pipe that is closer to the reactor pressure vessel than the main steam isolation valve. A main steam pipe plug for a boiling water reactor, which can be detachably attached to a boiling water reactor and configured to block the main steam pipe at an intermediate point. 2. The main steam pipe plug consists of a flange that can be detachably attached to a nozzle stub provided in the middle of the main steam pipe, and a plug body that is supported by the flange and located within the main steam pipe to close it. A main steam pipe plug for a boiling water nuclear reactor according to claim 1. 3. The main steam pipe plug for a boiling water nuclear reactor according to claim 2, wherein the plug body comprises a flexible bag that expands to come into contact with the inner wall of the main steam pipe when gas is supplied. 4. The main steam pipe plug for a boiling water reactor according to claim 2, wherein the plug body comprises a closing plate inserted into the main steam pipe from the side. 5. The main steam pipe plug for a boiling water reactor according to claim 2, 3 or 4, wherein the nozzle stub is a nozzle stub for a main steam relief safety valve. 6. Claim 1, 2, 3, 4, or 5 is provided in a part of the main steam pipe extending from the reactor pressure vessel that is closer to the reactor pressure vessel than the main steam isolation valve provided in the middle of the main steam pipe. After installing the main steam pipe plug and closing the main steam pipe at the midway point, pressurized gas is introduced into the main steam pipe between the main steam pipe plug and the main steam isolation valve, Leakage test method for main steam isolation valves of boiling water reactors.