JPS6411160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactor water leakage cutoff device for a nuclear reactor pressure vessel, and more particularly, to a reactor water leakage cutoff device used during drain piping replacement work for a boiling water reactor pressure vessel. It is something.

Prior to explaining the present invention, the internal structure of a boiling water reactor pressure vessel will be explained based on FIG. In FIG. 1, reference numeral 1 generally indicates the entire reactor pressure vessel, and the pressure vessel 1 is roughly divided into a vessel body 2, a lower mirror 3, and an upper cover (not shown). There is. Inside the pressure vessel 1, there are a steam dryer 4, a steam separator 5, a shroud upper cover 6, an upper grid plate 7, a fuel rod 8, a fuel rod support (not shown),
Internal reactor structures such as a core support 9 and further control rod guide tubes 10 are incorporated. Also, lower mirror 3
A control rod drive mechanism housing 11 and a reactor pressure vessel drain pipe 12 are welded to each other.

In the above configuration, in order to replace the drain pipe 12 connected to the bottom of the pressure vessel 1, the vessel 1 must be filled with reactor water, that is, the drain pipe connection port at the bottom of the vessel must be sealed with water. , creating a highly radioactive environment that workers cannot approach.

Therefore, in a state where reactor water is present, the drain pipe 12
To replace the reactor, a water seal plug must be installed at the drain pipe connection port at the bottom of the vessel, but this plug is installed from above the core.
When installing the plug, it is necessary to remove various installed equipment from the inside of the pressure vessel 1. The items that can be removed from the inside of the pressure vessel 1 are the steam dryer 4, steam separator 5, shroud top cover 6, fuel rods 8, and the The fuel rod support and control rod guide tube 10 are omitted, and the other reactor internal structures are integrally welded to the fuselage 1 and cannot be removed. Fig. 2 is a diagram showing the arrangement relationship between the vessel body and the internal welding members after removing various installed equipment from the inside of the pressure vessel 1 shown in Fig. 1, and Fig. 3 is a view taken along arrow A-A in Fig. 2. In the figure, the upper grid plate 7, core support 9, and control rod drive mechanism housing 11 remain in the shell of the pressure vessel 1, and these become obstacles when inserting and withdrawing the water seal plug. To explain this in more detail, reference numeral 1 is shown in Figure 2.
The drain pipe connection port indicated by 3 is located between many control rod drive mechanism housings 11, and in the existing reactor pressure vessel, as shown in FIG. Since the mouth part 13 is provided offset from the center of the pressure vessel 1, a platform is installed on the flange part 1a of the pressure vessel 1 prior to the replacement work of the drain pipe 12, and the reactor is filled with water. Even if an attempt is made to attach a water seal plug to the drain pipe connection port 13, this operation is complicated.

On the other hand, foreign matter such as crud adheres to the inner wall of the drain pipe connection port 13 over time, and this foreign matter is expected to impair the water sealing effect. Beforehand, it is necessary to consider the removal of the foreign matter.

On the other hand, in order for the water seal plug to easily reach the drain piping connection port, which is offset from the center of the reactor pressure vessel, there is a bend in the middle of the operating rod with the water seal plug attached to the tip. A reactor water leakage cutoff device was developed in Japanese Patent Application Laid-Open No. 2003-103002, in which the operating rod can be taken in and out of the reactor from above the reactor pressure vessel.
Previously proposed as No. 55-39020.

The present invention is a further improvement of this type of reactor water leakage cutoff device, that is, a reactor water leakage cutoff device for a reactor pressure vessel in which a bent part is provided in the middle of an operating rod with a water seal plug attached to the tip. The purpose of this is to polish the drain piping connection port while the reactor water is full, prior to the drain piping replacement work of the boiling water reactor pressure vessel. Foreign matter such as crud adheres to the inner wall over time, and it is expected that this foreign matter will impair the water sealing effect. Furthermore, when installing a water seal plug subsequent to this, it is possible to share a part of the equipment and reduce product costs.In addition, the water seal plug can improve the reliability of the water seal at the drain piping connection port. It is an object of the present invention to provide a reactor water leakage cutoff device for a nuclear reactor pressure vessel that can also ensure a long service life.

The above purpose is to attach a plug unit to the tip of the operating rod that is moved in and out of the reactor from above the reactor pressure vessel to seal the drain pipe connection port at the bottom of the reactor pressure vessel, and The plug unit that water-seals the pipe connection port has a two-stage seal structure, upper and lower, and the upper seal plug is wedge-shaped so that it tightly contacts the inner wall of the drain pipe connection port due to its own weight and the hydraulic head of the reactor water. At the same time, a drain pipe is provided in the middle of the operating rod (the part of the operating rod that is inserted below the core support located in the reactor pressure vessel) and is offset from the center of the reactor pressure vessel. A reactor water leakage cutoff device for a reactor pressure vessel having a bent portion through which a plug unit reaches a connection port, comprising: a joint portion connected to the tip of the operating rod;
An air motor installed at the bottom of the joint,
A polishing unit having a polishing brush attached to the bottom of the air motor and polishing the drain pipe connection port at the bottom of the pressure vessel is attached to the operating rod so as to be replaceable with the plug unit, and a passage is provided in the operating rod. This passage is shared as a compressed air supply passage to the air motor of the polishing unit and a compressed air supply passage to the lower seal plug of the seal plug unit configured with upper and lower seal plugs, Among the two-tiered seal plugs, the lower seal plug is expanded by processing the hollow part of the plug, so that it comes into close contact with the inner wall of the drain pipe connection port. It is achieved by doing so.

Hereinafter, the present invention will be explained based on an embodiment shown in FIGS. 4 to 7.
The operating rod 14 shown in FIG. 1 and FIG.
A plug unit 16 (FIG. 6) which is attached to the tip of the operating rod 14 in place of the polishing unit 15 and seals the drain pipe connection port 13 of the pressure vessel 1 with water. 7
A polishing unit 15 is attached to the drain pipe connection port 13 which is provided offset from the center of the pressure vessel 1 (in other words, the hole center d of the upper grid plate 7 and the core support 9). (and the plug unit 16), there is a bent part 14 in the middle of the operating rod 14 (the part of the operating rod inserted below the core support 9).
a is formed.

As shown in FIG. 6, the polishing unit 15 for polishing the drain pipe connection port 13 of the reactor pressure vessel 1 is composed of a joint 17 with the operating rod 14, an air motor 18, and a polishing brush 19. The air motor 18 that rotates the
Compressed air is supplied from an air source through a passageway passing through the operating rod 14.

The plug unit 16 that seals the drain pipe connection port 13 of the reactor pressure vessel 1 has rubber seal plugs 20 and 21 in two stages, upper and lower, as shown in FIG. The seal plug 20 expands by pressurizing its hollow portion and comes into close contact with the inner wall of the drain pipe connection port 13 .
The hollow portion of the seal plug 20 is supplied with compressed air from an air source through a passage passing through the operating rod 14, and a compressed air supply passage for the polishing unit 15 and the plug unit 16 is provided. By sharing the air supply system with both units 15 and 16, the air supply system can be simplified, contributing to a reduction in product cost. The seal plug 21 located above the seal plug 20 is formed into a wedge shape, and is brought into close contact with the inner wall of the drain pipe connection port 13 due to its own weight and the hydraulic head of the reactor water.

In the above configuration, before replacing the drain pipe connected to the bottom of the reactor pressure vessel 1 while the reactor water is full, first, the operating rod 14
A polishing unit 15 is attached to the tip of the pipe, and the polishing unit 15 polishes the drain pipe connection port 13 of the pressure vessel 1 to remove foreign matter such as crud that has adhered to the inner wall of the port 13 over time. This improves the adhesion between the plug unit 16 and the mouth portion 13. The handling of the operating rod 14 in that case is as follows. First, as shown in FIG. 6, the operating rod 14 is lowered from above the pressure vessel 1, and when the bent portion 14a of the rod 14 passes through the hole in the core support 9, the rod 1
4 in parallel in the direction of the drain pipe connection port 13. In this way, when the polishing unit 15 reaches the position of the drain pipe connection port 13, the rod 14 is lowered, the air source is opened, compressed air is supplied to the air motor 18, and the polishing brush 19 is rotated. By doing so, foreign matter such as crud adhering to the inner wall of the drain pipe connection port 13 is removed.

When the inner wall polishing of the drain pipe connection port 13 is completed as described above, the air source is closed to stop supplying compressed air to the air motor 18, the rotation of the polishing brush 19 is stopped, and the operation rod 14 is The polishing unit 15 is pulled up from the mouth 13, and the operating rod 14 is taken out from the pressure vessel 1 in the reverse order of insertion into the furnace. Next, operation rod 1
Remove the polishing unit 15 attached to the tip of the rod 4, attach a new plug unit 16 to the tip of this rod, and insert the plug unit 16 into the drain pipe connection port in the same manner as the insertion of the polishing unit 15 into the furnace described above. Install it within 13. After installing the plug unit 16 into the mouth 13, open the air source and
When the hollow part of the seal plug 20 is pressurized with compressed air, the seal plug 20 expands and comes into close contact with the inner wall of the drain pipe connection port 13. When the drain piping replacement work is completed with the drain piping connection port 13 sealed with water as described above, the air source is closed to stop pressurizing the seal plug 20.
The operation is completed by pulling up the operating rod 14, extracting the plug unit 16 from the drain pipe connection port 13, and removing the operating rod 14 from the pressure vessel 1.

If a universal joint is attached near the tip of the operating rod 14 or to the polishing unit 15 and plug unit 16, the tips of the units 15 and 16 will fit smoothly into the hole of the drain pipe connection port 13. be guided.

By the way, in the above-mentioned Japanese Patent Application Laid-open No. 55-39020, there is a seal plug located at the lower part of the upper and lower two-stage plug unit that water-seals the drain pipe connection port of the reactor pressure vessel, that is, a seal plug made of rubber or the like. The outer diameter of the seal plug made of an elastic material is larger than the inner diameter of the drain pipe connection port, and the seal plug is made larger than the inner diameter of the drain pipe connection port, so that when the drain pipe connection port is blocked, this seal There is a description of forcibly pushing the plug into the drain pipe connection port, but according to this, the seal plug made of an elastic material is forced into the drain pipe connection port of the reactor pressure vessel each time it is used. Therefore, the sliding friction between the inner wall of the drain pipe connection port and the seal plug is extremely large, and it is thought that the water sealing effect around the plug's outer periphery will be lost relatively quickly.
In order to ensure the water-sealing function of the reactor pressure vessel, which is an important piece of equipment, it is necessary to predict in advance that the frequency of replacing the plug will increase. In contrast, in the present invention, as described above, of the pair of upper and lower seal plugs 21 and 20 that water-seal the drain pipe connection port 13 of the reactor pressure vessel, the lower seal plug 20 is By applying pressure to the hollow part to expand it and make it tightly contact the inner wall of the drain pipe connection port 13, the seal plug 20 can be attached to the drain pipe connection port without applying excessive external force to the seal plug 20. It can be brought into close contact with the inner wall, and its durability can be greatly improved compared to the conventional devices of this kind.

The present invention is as described above, and according to the present invention, a water seal is attached to the tip of the water seal plug so that the water seal plug can easily reach the drain pipe connection port provided offset from the center of the reactor pressure vessel. Replacement work on the reactor pressure vessel drain piping in a reactor water leakage shutoff system in which a bent part is provided in the middle of the operating rod to which a plug is attached so that the operating rod can be taken in and out of the reactor from above the reactor pressure vessel. When polishing the drain piping connection port and subsequently installing the water seal plug in a state where the reactor water is full prior to the process, it is possible to share part of the equipment and reduce product costs. It is possible to provide an improved reactor water leakage shutoff device for a reactor pressure vessel that can simultaneously improve the reliability of the water seal at the drain piping connection port using the water seal plug and extend its life.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the internal structure of a boiling water reactor pressure vessel, and Figure 2 shows the arrangement of the vessel body and internal welding parts after removing various installed equipment from the pressure vessel body shown in Figure 1. The figure shown in Figure 3 is A- in Figure 2.
A view from arrow A and FIGS. 4 to 7 show an embodiment of the present invention, FIGS. 4 and 5 are illustrations for explaining the overall operation of the device of the present invention, and FIG. 6 shows the reactor pressure. FIG. 7 is an explanatory diagram of the configuration of a polishing unit for polishing a drain pipe connection port of a vessel, and FIG. 1... Reactor pressure vessel, 1a... Flange, 7
... Upper grid plate, 9 ... Core support, 11 ...
Control rod drive mechanism housing, 12... Drain pipe, 13... Drain pipe connection port, 14... Operation rod, 14a... Bent part, 15... Polishing unit, 16... Plug unit, 17... Joint part , 18...Air motor, 19...Abrasive brush, 20 and 21...Seal plug.

Claims (1)

[Scope of Claims] 1. A plug unit for water-sealing the drain piping connection port at the bottom of the pressure vessel is attached to the tip of an operating rod that is moved in and out of the reactor from above the reactor pressure vessel, and The plug unit that seals the drain piping connection port of the vessel has a two-tiered seal structure, with the upper seal plug tightly attached to the inner wall of the drain piping connection port due to its own weight and the hydraulic head of the reactor water. It is formed in a wedge shape, and is provided in the middle of the operating rod (the part of the operating rod that is inserted below the core support located in the reactor pressure vessel) so as to be offset from the center of the reactor pressure vessel. In a reactor water leakage cutoff device for a reactor pressure vessel, which has a bent part where the plug unit reaches the drain pipe connection port, a joint part connected to the tip of the operating rod and a joint part provided at the bottom of the joint part are used. A polishing unit having an air motor and a polishing brush attached to the bottom of the air motor and polishing the drain pipe connection port at the bottom of the pressure vessel is attached to the operating rod so as to be replaceable with the plug unit,
In addition, a passage is provided in the operating rod, and this passage is used as a passage for supplying compressed air to the air motor of the polishing unit, and for supplying compressed air to the lower seal plug of the seal plug unit, which has two upper and lower seal plugs. In addition to being shared as an air supply passage, the lower seal plug of the two-tiered seal plug is expanded by pressurizing the hollow part of the plug, and the inner wall of the drain pipe connection port is expanded. 1. A reactor water leak cutoff device for a reactor pressure vessel, characterized by having a structure that is in close contact with the reactor pressure vessel.