JPH03221896A - Water-proof plug for neutron flux monitor guiding tube - Google Patents

Abstract

PURPOSE:To easily and surely execute the preventive maintenance of a neutron flux monitor (ICM) housing without dipping up reactor water by sealing a gap between a plug and the inside of the ICM guiding tube in stages by upper and lower gaskets attached to the plug. CONSTITUTION:A pole equipped with the plug 11 on its lower end part is inserted into a reactor water in a neuclear reactor containment, the pole and the plug 11 are penetrated into a through hole of an upper grating plate, the plug 11 is finally inserted into the upper part of the ICM guiding tube 7, and the gap between the plug 11 and the inside of the tube 7 is sealed in stages by the upper and lower rubber gaskets 13 fixed to the plug to surely prevent the inside of the guide tube 7 from the invasion of reactor water. If the reactor water invades between the gaskets 13, the invading reactor water is detected by a leakage sensor 15. In addition, dry gas is fed from a blowout port 16 to the space around the packing elements 13 and the gap between the plug 11 and the inside of the tube 7 and moisture is exhausted from the tube 7 and the ICM housing 3 following the tube 7 together with the fed gas to dry the periphery of the gasket 13.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a neutron flux monitor housing (hereinafter referred to as ICM housing) in a nuclear reactor pressure vessel (hereinafter referred to as RPV) during the use of a nuclear power plant. This invention relates to a water-resistant plug for a neutron flux monitor guide pipe, which is used to isolate the work area from reactor water in a reactor pressure vessel when performing preventive maintenance work for stress corrosion cracking, etc.

[Conventional technology]

The ICM housing of the RPV of the boiling water reactor has a configuration as shown in FIG. In other words, a through hole IA is formed in RPVi which is overlaid with Inconel material etc.
In addition, a built-up seat 2 made of Inconel material or the like is provided for attaching the ICM housing 3 which communicates with the through hole 1A. An ICM housing 3, which passes through the wall of the RPVI, is welded to the overlay seat 2 via a welded portion 4. It is assumed that such an ICM housing 3 may develop a continuous crack at or near the welding part 4, causing reactor water to leak. Preventive measures are taken to prevent this crack from occurring and prevent reactor water from leaking. Conservation methods are needed. That is, patent application Hei 1-'20
1.18], the vicinity of the welded part on the inner surface of the ICM housing 3 is machined or polished, and a thin stainless steel cylindrical sleeve whose composition is adjusted to improve stress corrosion cracking resistance is inserted into that part, Expand and seal the cylindrical sleeve with a tube expansion device.

Then, the thin sleeve is melted on the inner surface of the ICM housing using a welding machine to form a build-up layer with high corrosion resistance on the inner surface.

By the way, since reactor water exists in the RPVI during the service life of a nuclear power plant, it is necessary to remove the reactor water from inside the ICM housing 3 during preventive maintenance work. A simple means of removing reactor water could be to extract all the reactor water in the RPVI, but this would require extremely troublesome work and would not only reduce the exposure of workers performing preventive maintenance work on the ICM housing 3. From this point of view, it is considered preferable to keep only the peripheral portion of the ICM housing 3 in a state where the reactor water is cut off while maintaining the reactor water at a normal water level.

When carrying out preventive maintenance work on the ICM housing 3, there are currently no known examples of ICM guide pipe water proofing to isolate the parts subject to preventive maintenance from reactor water. The ICM guide pipe water-resistant injection for isolating the target part from reactor water is disclosed in Japanese Patent Application Laid-open No. 61-569.
There is an ICM guide tube water resistant injection method in the CM housing repair method known in Japanese Patent No. 98. ICM according to this bulletin
Figure 3 shows the structure of the guide tube water resistant injection molding. IC in Figure 3
M guide tube water resistant injection is carried out from the RP V I Jz section to the ICM using the plug 10 before ICM housing repair work.
A temporary frame is provided at the upper end opening of the guide tube 7, and the ICM housing repair work can be performed with reactor water entering the RPVI.

[Problem to be solved by the invention]

By the way, if you use the ICM guide tube water resistant injection, the RP
A working environment for ICM housing repair work can be obtained relatively easily without the need to pump out the reactor water in the V. However, since the known engineering CM guide pipe drainage plug only provides a temporary frame at the upper end of the engineering CM guide pipe, from the perspective of ensuring reliability after preventive maintenance, the reactor water can be reliably removed when performing ICM housing repair work. need to be sealed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ICM guide tube water-resistant sprayer that can easily and reliably perform preventive maintenance work on an ICM housing without pumping out reactor water.

[Means to solve the problem]

The primary means for achieving the above object includes a neutron flux monitor housing that is installed by penetrating the wall surface of the reactor pressure vessel, and a core support in the reactor pressure vessel that is connected to the neutron flux monitor housing. The neutron flux monitor guide tube inserted into the through-hole of the plate and the neutron flux monitor through-hole of the core support plate are installed in the reactor pressure vessel in a direction closer than the core support plate, and the neutron flux monitor through-hole of the core support plate is A plug to be inserted into the neutron flux monitor guide tube of a nuclear reactor, which has an upper grid plate with a through-hole arranged out of the way, the plug having a diameter that allows it to pass through the through-hole of the two-part grid plate, and the pole and a plug having a diameter that allows the plug to pass through the through hole of the upper grid plate and enter the neutron flux monitor guide tube, and the plug is capable of contacting the neutron flux monitor guide tube with the gasket. This is a neutron flux monitor guide tube water direction plug characterized in that the monitor guide tube is provided in multiple stages at intervals in the tube axis direction, and the second means includes, in addition to the first means, a multi-stage seal. A neutron flux monitor guide tube water-resistant plug characterized by being equipped with a leak sensor in the plug part between the two, and the third means is:
In addition to either the first means or the second means, there is provided a neutron flux monitor guide pipe, characterized in that the plug portion between the multi-stage packings is equipped with an ejection port through which gas is ejected. It is plug resistant,
A fourth means, in addition to any one of the means 1.2.3, is a neutron flux monitor guide tube characterized in that among the multistage packings, a packing near the lower end of the plug is an inflatable air packing. The fifth means is a water-resistant plug, and in addition to either of the first and second means, the fifth means includes a gas vent in a part of the plug that is closer to the bottom end of the plug than the multi-stage packing. A neutron flux monitor guide pipe water-resistant plug characterized by being equipped with the sixth means,
In addition to any one of means 1.2, 3, and 4.5, the pole has a straight upper and lower part, and a neutron flux characterized in that the middle of both the upper and lower parts is bent. The seventh means is a water-resistant plug for the monitor guide pipe, and the seventh means is the first, second,
3. In addition to any of the means of 4.5.6, the pole is provided with a collar that is hooked onto the upper grid plate when the neutron flux monitor guide tube is plugged. This is a water-resistant plug for the neutron flux monitor guide tube.

[Effect]

In the first method, a pole with a plug attached to the lower end is placed in the reactor water in the reactor pressure vessel, the pole and the plug are passed through a through hole in the upper grid plate, and the plug is finally guided to the neutron flux monitor. It is inserted into the upper part of the tube, and the gap between the plug and the inner surface of the neutron flux monitor guide tube is sealed in multiple stages by the upper and lower multi-stage gaskets installed on the plug, ensuring that reactor water does not enter the inside of the neutron flux monitor guide tube. Obtains a preventive effect.

In the second means, in addition to the effect provided by the first means, when reactor water enters between the multiple packings, a leak sensor detects the intruded reactor water.

In the third means, in addition to the action of either the first means or the second means, gas is supplied from the jet port from the space between the multi-stage packing to the gap between the plug and the inner surface of the neutron flux monitor guide tube. This makes it possible to dry the neutron flux monitor guide tube and the subsequent neutron flux monitor housing together with the supply gas, improving working conditions. This prevents reactor water adhering to dripping and causing the leak sensor to malfunction.

In the fourth means, in addition to the action of any one of the means 1.2.3, the air packing near the lower end of the plug among the multi-stage packings is shrunk to allow the plug to be inserted into or removed from the neutron flux monitor guide tube. The effect of making work easier can be obtained.

In the fifth means, in addition to the effects of either means 1.2 or 3.4, the gas accumulated in the neutron flux monitor guide pipe and the subsequent neutron flux monitor housing due to repair work is released from the gas vent port. The effect of hollowing out can be obtained.

In the sixth means, in addition to the effects of any one of means 1.2, 3, and 4.5, the central position of the neutron flux monitor through hole of the two-part grid plate and the neutron flux monitor guide tube is Even if the plug deviates from side to side, the deviation is absorbed by the bent portion of the pole, and the plug is inserted vertically into the neutron flux monitor guide tube, resulting in a better sealing condition than if the plug is inserted obliquely.

In the seventh means, in addition to the action of any one of the means 1.2, 3, 4, and 5.6, when the plug is inserted into the neutron flux monitor guide tube, the collar on the top of the pole touches the upper grid plate. It stably supports the hooked plug or pole and maintains a reliable seal.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 4 shows a reactor pressure vessel of a boiling water reactor. The reactor pressure vessel 1 is composed of a fuselage IC, a lower mirror 1D, and an upper cover (not shown). The reactor pressure vessel 1 is fixed by a skirt 5 on a pedestal (not shown) of the reactor containment vessel. Further, the weld overlay seat 2 is overlay welded to the reactor pressure vessel lower mirror ID. On the other hand, I.C.
The M housing 3 is connected to the weld overlay seat 2 via the weld portion 4.
It is fixedly installed.

FIG. 2 shows an overall view of an ICM guide tube water-resistant jet according to an embodiment of the present invention. 9 and a two-part lattice plate 8 fixedly supported by one of them.

- Upper grid plate 81. Here, the through hole 8a is connected to the core support plate 91. ; is provided with a through hole 9a, and the centers of the through holes 8a, 9a are shifted from each other in the left-right direction.

(2) An ICM guide pipe with a diameter that can be inserted into the CM guide pipe 7. A water plug 11 is attached to the lower end of the pole 12. The two ends of the pole 12 are attached to a flange t2a, and the flange 12a has a horizontal size that allows the pole 12 to be caught in the through hole 8a without falling out. The pole 12 is bent twice in the middle as shown in Figure 2.
The upper and lower parts are in a vertical straight line. Paul] 2
Since the entire body is bent to the left, a ballast l-1, 21) is attached to the left side of the 2a as a balancer.

FIG. 1 is a detailed view of the ICM guide tube 11-water injection plug 11 according to one embodiment of the present invention. This ICM guide pipe water-resistant plug 11 has a multi-tiered upper and lower double-layered sealing structure consisting of a primary packing made of two ring-shaped rubber packings 13 and a secondary packing made of an expandable and contractible air packing 14. Leak sensor 15, inside ICM guide tube 7,
and a drying gas outlet 16 for drying the inside of the CM housing 3, a high temperature gas vent 17 for preventing a temperature rise inside the ICM housing 3, and a high temperature gas vent 17 for preventing a rise in temperature inside the ICM housing 3. The guide 18 has a small diameter.

Inside the bracket 1, a gas passage 16a is provided, one end of which is connected to the drying gas outlet 16, and the other end connected to a high-pressure argon gas source via a valve 24. The inside of the plug 11 is equipped with a gas passage 17a whose one end is connected to a high-temperature gas vent [117] and whose other end is open outside the reactor water.

The leak sensor 15 has a power supply 19 and a leak sensor 15.
A relay unit 23 activated by a detection signal is connected by an electric wire, and its power source is passed through the plug 11 in an insulated state. An air supply/exhaust passage 14 whose one end is connected to the inside of the air packing 14
a is passed through the plug 11, and the other end is connected to high pressure air 'tX20 via a valve 21. An exhaust valve 22 is attached to a branch pipe 4b connected in the middle of the air supply/exhaust passage 14a. The hose is said to be able to withstand high pressure.

In such a configuration, the exhaust valve 22 is opened to reduce the air exhaust valve 4. In this state, a plug is inserted into the reactor pressure vessel 1 from above the reactor pressure vessel 1 where reactor water is present]1. Paul 12. The entire tsuba 12a is suspended and lowered. At this time, the plug 11 is placed in a vertical position because the balance h 12 +:) adjusts the overall balance.

The plug 11 and the pole 12 pass through the through hole 8a and descend, and finally the plug 11 is inserted into the ICM guide tube 7. When inserted, the plug 11 is supported vertically, the guide 18 is tapered, and the air packing 14 is compressed, so it can be inserted smoothly.

As the plug 1] is inserted into the CM guide tube 7,
Finally, the collar ↓2a gets caught on the upper grid plate 8 without passing through the through hole 8a. In this state, the plug 11, the pole 12, and the collar 12a are supported by the upper grid Fi8 and held at accurate positions.

Next, (1) extract the reactor water inside the ICM housing 3 and the ICM guide pipe 7 from the lower end of the CM housing 3; At this point, the upper and lower rubber gaskets 13 prevent new intrusion of reactor water into the ICM housing 3 and ICM guide pipe 7.

Next, the valve 24 is opened and high pressure argon gas is passed through the gas passage 16a from the argon gas source 25 to the dry gas outlet 1.
The argon gas is ejected from 6, and the ejected argon gas entrains moisture and releases it downward. As a result, the inner wall surfaces of the ICM housing 3 and the ICM guide tube 7 are kept in a dry state. This dry state eliminates the reactor water adhering to the leak sensor 15 and moisture that tends to drip onto the leak sensor 15 from the outer peripheral surface of the plug 11, thereby suppressing malfunction of the leak sensor 15.

Next, the valve 24, the exhaust valve 22, etc. are closed, and the valve 21 is opened. By doing this, the drying work is completed and the air source 2
0 high pressure air is supplied into the air packing 14 through the air supply/exhaust passage 14a, and as a result of the supply, the air packing 4 expands and is forced to a large contact area against the inner wall surface of the ICM guide tube 7 by pressure. The rubber gasket 13 and the rubber gasket 13 form a multiple sealing state. For this reason, the sealing condition is reliably maintained.

After this, preventive maintenance work or repair work is added to the inner wall surface of the ICM housing 3. Gases that should be exhausted, such as high-temperature gas generated during the work, are removed from the high-temperature gas vent 17.
The gas is exhausted to the outside through the gas passage 17a.

During this work, if reactor water in the reactor pressure vessel 1 passes through the rubber seal 13 for some reason and enters, the leak sensor 15 performs a detection function under the influence of the deicing water. , Test 5: Transmit the black signal to relay unit 1-23. When this relay unit 23 receives a detection signal from the leak sensor 15, the relay of the relay unit 23 is driven to drive an emergency notification means such as an emergency bell (not shown). By driving the emergency notification means, it is predicted that reactor water will enter the work area, and work will be interrupted to ensure safety.

After completing work such as preventive maintenance work, the ICM
After closing the lower end of the housing 3, the lower end 21 is closed, the exhaust valve 22 is opened, and the air packing 14 is contracted. Next, the upper guard 2a, the pole 12. Pull the plug 11 in three directions and pull it out from the ICM guide tube 7. and,
Pull it up further to remove the collar 12a and the pole 12. Plug 11
2 through the through holes 8a, and then lowered so as to pass through the through holes 8a on the three sides near the ICM housing 2 where preventive maintenance work is to be performed.

By repeating this process, preventive maintenance work can be easily carried out on a large number of ICM housings without having to pump out all the reactor water in the reactor pressure vessel.

〔Effect of the invention〕

According to the invention of claim 1, since the reactor water can be reliably sealed when performing work on the ICM housing by leaving the reactor water in the reactor pressure vessel, it is possible to obtain the effect that the work can be performed easily and safely. .

According to the invention of claim 2, in addition to the effect of the invention of claim 1, there is an effect that it is possible to detect the intrusion of reactor water from the reactor water seal portion, and that during maintenance work, the leak sensor can be prevented from performing maintenance work by the seal. Since it can be isolated from a location, it is not affected by the work environment and has the effect of eliminating malfunctions.

According to the invention of claim 3, in addition to the effects of the invention of claims 1 or 2, moisture can be removed from the inside of the ICM guide tube in the ICM housing below the sealing point, thereby improving the environment for maintenance work, etc. This provides the effect of sealing and the effect of drying the sealing surface to improve the sealing effect.

According to the invention of claim 4, in addition to the effects of the invention of either claim 1 or 2.3, the packing near the lower end of the plug inserted most deeply can be expanded and contracted by the air packing, so that the ICM guide In addition to the effect of facilitating insertion into and extraction from the pipe, especially in combination with claim 3, it protects the leak sensor as well as the gas outlet for drying, and if necessary, the air packing can be compressed. The effect of supplying drying gas below the air packing to remove moisture can be achieved.

According to the invention of claim 5, in addition to the effects of the invention of any one of claims 1, 2, 3, and 4, high temperature gas generated during maintenance work can be extracted from the work area even in a sealed state. This has the effect of making work easier.

According to the invention of claim 6, in addition to the effects of the invention of any one of claims 1, 2, 3, 4.5, the through holes in the upper grid plate and the through holes for neutron flux monitoring in the core support plate are provided. Even if there is a horizontal misalignment, the plug can be easily inserted during sealing work by bending the pole and applying its own weight vertically.
This provides the advantage of being able to be inserted vertically into the CM guide tube.

According to the invention of claim 7, claims 1, 2, and 3゜411:
In addition to the effects of any of the above inventions, since the plug is stably supported using the two-part lattice plate, it is possible to maintain a sound sealing state without any effort.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the ICM guide pipe water-resistant plug part when in use, showing an embodiment of the present invention, and FIG. FIG. 3 is a longitudinal sectional view showing the relationship, and FIG. 3 is a longitudinal sectional view showing the installation state of a conventional ICM guide tube water-resistant injection gun for repairing the ICM housing. FIG. 4 is a sectional view of the lower part of the reactor pressure vessel. FIG. 5 is a longitudinal sectional view showing the relationship between the ICM housing and the reactor pressure vessel. - Reactor pressure vessel, 1A... through hole, 1C... fuselage, 1D... lower mirror, 2 overlay seat, 3 - TCM housing, 4... welded part, 5 - to scar I, 6- CRD housing, 7 CM guide tube, 8 Upper grid plate, 8D through hole, 9 Core support plate, 9a/through hole, ]1=19- ICM guide tube water resistant injection, 12...pole, 12a/
...Trim, 12b...Ballast, 13...Rubber packing, 14...Air packing, 15...Leak sensor 16...Dry gas outlet, 16a...Gas passage, 17...High temperature Gas vent port, 17a... gas passage,
20...Air source, 21...Valve, 22...Exhaust valve, 23...Relay unit, 24...Valve, 25...
・Argon gas source.

Claims (1)

[Scope of Claims] 1. A neutron flux monitor housing installed to penetrate the wall surface of the reactor pressure vessel, and a through hole of a core support plate in the reactor pressure vessel connected to the neutron flux monitor housing. and a neutron flux monitor guide tube inserted into the reactor pressure vessel above the core support plate, and a through hole located laterally apart from the neutron flux monitor through hole of the core support plate. A plug to be inserted into the neutron flux monitor guide tube of a nuclear reactor, which is equipped with an upper grid plate having holes, includes a pole having a diameter that can pass through the through hole of the upper grid plate, and a pole attached to the lower part of the pole, a plug having a diameter that is inserted into the neutron flux monitor guide tube through the through hole of the lattice plate, and the plug moves the packing in the axial direction of the neutron flux monitor guide tube so as to be able to contact the inside of the neutron flux monitor guide tube. A water-resistant plug for the neutron flux monitor guide tube that is spaced apart. 2. A water-resistant plug for a neutron flux monitor guide tube according to claim 1, characterized in that a leak sensor is provided in the plug portion between the multiple packings. 3. The water-resistant plug for a neutron flux monitor guide tube according to claim 1 or 2, characterized in that a plug portion between the multi-stage packings is equipped with a spout through which gas is spouted. 4. The neutron flux monitor guide tube water-resistant plug according to any one of claims 1, 2, and 3, wherein the packing near the lower end of the plug in the multistage packing is an expandable and contractible air packing. 5. The neutron according to any one of claims 1, 2, 3, and 4, wherein a gas venting port is provided in a plug portion closer to the lower end of the plug than the multistage packing. Bundle monitor guide tube water resistant plug. 6. The neutron pole according to any one of claims 1, 2, 3, 4, and 5, characterized in that the upper and lower parts of the pole are straight, and the upper and lower parts are bent in the middle. Bundle monitor guide tube water resistant plug. 7. In any one of claims 1, 2, 3, 4, 5, and 6, the pole is provided with a collar that fits against the upper grid plate in a state where a plug is inserted into the neutron flux monitor guide tube. A water-resistant plug for the neutron flux monitor guide tube.