JPH0526159B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a method for replacing an in-core housing flange forming a reactor pressure vessel boundary and an in-core housing sealing device used for the replacement, and particularly relates to a method for replacing an in-core housing flange forming a reactor pressure vessel boundary and an in-core housing sealing device used for the replacement. The present invention relates to a method for replacing an in-core housing flange that allows the in-core housing flange to be replaced without removing the in-core housing flange, and an in-core housing flange sealing device used for the replacement.

[Technical background of the invention and its problems]

Generally, a reactor pressure vessel is housed in a reactor building of a boiling water nuclear power plant. As shown in FIG. 1, this reactor pressure vessel 1 is supported on a reactor pressure vessel pedestal 2, and has an upper lattice plate 3 inside.
A core support plate 4 is housed therein to constitute a core portion of a nuclear reactor. A number of fuel assemblies (not shown) are disposed in the reactor core, and a second Icore monitor detector assembly 5 is inserted through the fuel group of each fuel assembly.
It is installed as shown in the figure and detects neutrons within the reactor core to detect local output. This in-core monitor detector assembly 5 has an elongated cylindrical shape, and its head is held by the upper grid plate 3, and its lower part extends downward through the core support plate 4 and is guided into the in-core guide tube 6. The in-core monitor detector assembly 5 guided by the in-core guide tube 6 is then guided into the in-core housing 7 and supported by the in-core housing flange 8 with a metal touch. The in-core guide tube 6 has its top supported by the core support plate 4, and its lower part supported by the in-core housing 7.
is connected with metal touch. This in-core housing 7 is welded to the bottom of the reactor pressure vessel 1 as shown in FIG. As shown in FIG. 2, the in-core housing flange 8 is attached in a watertight manner.

Therefore, when the in-core monitor detector assembly 5 is installed in the reactor pressure vessel 1, the reactor pressure vessel boundary (hereinafter referred to as RPV boundary) is divided between the lower part of the reactor pressure vessel 1, the in-core housing 7, and the in-core housing. It consists of a flange 8 and an in-core monitor detector assembly 5. The in-core monitor detector assembly 5 is replaced during periodic inspections of nuclear power plants. At the time of this replacement, a bag-shaped jig is attached to the in-core housing flange 8 to expand the RPV boundary, and the in-core housing flange 8 and the in-core monitor are The metal touch part of the detector assembly 5
It is designed to fit within the RPV boundary so that it can be easily replaced. However, when replacing the in-core housing flange 8, the RPV boundary will be damaged, making it impossible to maintain the reactor water at a predetermined level.

In conventional nuclear power plants, the following two methods of replacing the in-core housing flange are adopted.

The first method is to move all the fuel assemblies installed in the reactor core to another storage location so that there is no problem even if the RPV boundary is damaged, and then pour the reactor water to the level of the top of the in-core housing 7. Remove up to
Even if the in-core housing flange 8 is removed, the replacement is performed so that reactor water does not flow out.

The second method is to press a highly elastic stopper 9 made of rubber or the like onto the top of the in-core guide tube 6 from above, as shown in Figures 1 and 6, to seal the in-core guide tube 6 in such a way as to suppress the spurt of reactor water. and exchange it. As an emergency measure against leakage from the sealing surfaces of the in-core housing flange 8 and the in-core monitor detector assembly 5, a nut 10 is provided as shown in FIG. 4, and the seal portion of the in-core housing flange 8 is tightened with this nut 10. Therefore, there is a method of preventing leakage using a rubber O-ring attached to the nut 10.

However, the in-core housing flange 8
If you use the first method to replace
Removal of the fuel inside the reactor, lowering of the reactor water level, and restoration work after replacing the in-core housing flange 8 are complicated and require approximately 20 work days, so the inspection of the entire periodic inspection of the nuclear power plant is difficult. There is a problem in that the number of days increases, and the period during which nuclear power plants are out of operation becomes longer.

Further, in the second method, the plug 9 is attached to the tip of the rubber holding pole 9a, but there is a lack of certainty in holding the plug 9 in a predetermined position on the core support plate 4. There were problems such as it easily coming off. Furthermore, the connection between the in-core guide tube 6 and the in-core housing 7 is kept watertight by a metal touch, but since the metal touch in this part is in the middle, it is tightened with a nut 10 like the in-core housing flange 8 to ensure sealing performance. It cannot be increased. Therefore, if the plug 9 only presses the top of the in-core guide tube 6, the seal plug at the metal touch part will not be completely sealed, which may cause reactor water to leak from the metal touch or cause backup if the plug 9 comes off. Because there is no sealing regime, if plug 9 is removed, reactor water will gush out of the in-core housing, and in the worst case, the reactor water level may drop and irradiated fuel may be exposed, causing damage to the nuclear power plant. There was a risk of negative effects.

[Purpose of the invention]

The present invention takes the above-mentioned points into consideration, and by simply installing a simple in-core housing sealing device inside the in-core housing, the in-core housing flange can be replaced safely and reliably in a short period of time without draining the reactor water. An object of the present invention is to provide a method for replacing an in-core housing flange and an in-core housing sealing device used for the replacement, which saves the shutdown period of a nuclear reactor and improves the operating rate of a nuclear power plant.

[Summary of the invention]

In order to achieve the above-mentioned object, the first invention of the present invention provides a method for attaching a flange sealing body such as a valved pipe or a blind plug to an in-core housing flange that constitutes a reactor pressure vessel boundary.
Pull the in-core monitor detector assembly out of the in-core housing and remove it from the reactor core.
Subsequently, an in-core housing sealing device is inserted into the in-core housing and this sealing device is installed in the reactor core, and after this installation, a working fluid is pressurized into the expansion seal ring of the in-core housing sealing device to expand it. After this seal is completed, replace the in-core housing flange and attach a new in-core housing flange to the in-core housing.Attach a flange sealing body to the installed in-core housing flange.After this installation, close the in-core housing. The seal device is pulled out from the in-core housing and removed from the reactor core, and then the aforementioned or new in-core monitor detector assembly is inserted into the in-core housing and installed in the reactor core, and the in-core housing is removed without draining the reactor water. This invention provides a method for replacing an in-core housing flange in which the flange is replaced.

Further, the second invention of the present invention is that when installed in the core of a nuclear reactor, an in-core housing sealing device that can be inserted into the in-core housing is attached to a main body pipe supported by a core support plate, and an upper part of this main body pipe. It is configured in an elongated cylindrical shape from a holding rod that is elastically supported by a spring and removably engages with the upper grid plate, and an in-core housing seal pipe that is provided at the lower part of the main body pipe and that can be inserted into the in-core housing. The in-core housing seal pipe is equipped with an expansion seal ring that expands freely, and when working fluid is pressurized into this expansion seal ring, the expansion seal ring expands and comes into close contact with the inner circumferential wall surface of the in-core housing, causing reactor water to leak. The present invention provides an in-core housing sealing device used for replacing an in-core housing flange, which is designed to watertightly seal the in-core housing flange.

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 7 shows a nuclear reactor installed in a boiling water nuclear power plant, and reference numeral 11 in the figure indicates a reactor pressure vessel housed in a reactor building (not shown).
This reactor pressure vessel 11 is supported on a reactor pressure vessel pedestal 12, and has an upper lattice plate 13 inside.
and a core support plate 14 are housed, and the core part of the nuclear reactor is constructed between them. A large number of fuel assemblies (not shown) are arranged in the reactor core, and an in-core monitor detector (local power range monitor...LPRM) assembly 15 is installed through the fuel group of each fuel assembly.
is installed, and this assembly 15 detects neutrons within the reactor core to detect local reactor power.

The in-core monitor detector assembly 15 has an elongated cylindrical shape, and its head is held by the upper grid plate 13. The lower part of the in-core monitor detector assembly 15 extends downwardly through the core support plate 14 and is conventionally guided within an in-core guide tube 16 and an in-core housing 17, and is attached to the lower flange 17a of the in-core housing 17. It is held watertight by the housing flange 18.

Therefore, when replacing the in-core housing flange 18, a valved pipe 20 as a flange sealing body is watertightly attached to the lower part of the flange 18, as shown in FIG. Cover the bottom end watertight. At this time, the valve 21 of the pipe 20 is closed.

As shown in FIG. 8, the in-core housing 18
After sealingly covering the lower part of the in-core monitor detector assembly 15 with the pipe 20, the in-core monitor detector assembly 15 is held by an exchanger (not shown), pulled out upward from the in-core housing 17 and the in-core guide tube 16, and stored in another storage location (not shown). . After this storage, the in-core housing sealing device 25 shown in FIG. 9 is inserted.

The in-core housing sealing device 25 has an elongated cylindrical structure similar to the in-core monitor detector assembly and replaces this assembly 15.
The upper end of the in-core housing seal device 25 is adapted to fit into a recess in the upper grid plate 13 at the location of the in-core monitor detector assembly device. The center part of the in-core housing sealing device 25 has a support collar 26
is held on the core support plate 14, while its lower part is housed within the in-core guide tube 16 and the in-core housing 17.

The in-core housing sealing device 25 includes a main body pipe 27 having a multistage connection structure constructed by connecting a plurality of pipes, a holding rod 29 elastically supported by a spring 28 housed in the upper part of the main body pipe 27, and the above-mentioned holding rod 29. In-core housing seal support pipe 3 connected to the lower part of the main body pipe 27
0, and an in-core housing seal pipe 32 connected to this support pipe 30 via an intermediate pipe 31, of which the seal pipe 32 guides the in-core housing sealing device 25 to the in-core housing 17 through the in-core guide pipe 16. It also serves as a guide.

The upper part of the in-core housing sealing device 25 is constructed as shown in FIG. Holding rod 29
is slidably attached to the upper part of the main body pipe 27 and is biased by a spring 28.
The upper expanded portion of the holding rod 29 engages with the recess of the upper grid plate 13, thereby being elastically held.

The central part of the in-core housing sealing device 25 is composed of a main body pipe 27, and a support collar 26 is attached to the lower center of the main body pipe 27 to support the sealing device 25 on the core support plate 14. The engagement of the retaining rods 29 into the recesses of the upper grid plate 13 secures the in-core housing sealing device 25 in place. Support pipe impulse pipes 35a and 35b are introduced from the middle of the main body pipe 27 of this sealing device 25. The impulse tubes 35a and 35b come out from the center of the main body pipe 27 and are connected to impulse tube side connectors 36a and 36b, respectively. Impulse tube side connector 36a,
36b is the pressure-conducting flexible tube connector 3
a flexible tube 38a, coupled to 7a, 37b and connected to a source of working fluid (not shown);
38b.

On the other hand, the support pipe impulse tubes 35a and 35b guided into the main body pipe 27 are introduced into the in-core housing seal support pipe 30 from the lower part of the main body pipe 27, and are connected to impulse tube side connectors 39a and 39b and impulse flexible connectors 40a and 40b. Pressure guiding flexible tubes 41a, 41b
are connected to each. The pressure guiding flexible tubes 41a and 41b are guided to an in-core housing seal pipe 32 via an intermediate pipe 31, and have an expansion seal ring 42 at each tip that expands in a contractable manner.
connected to a and 42b. Expanding seal ring 42
a, 42b are accommodated in outer circumferential grooves 43a, 43b formed in the in-core housing seal pipe 32. Guide holes 44a, 44b are opened in the side walls (or bottoms) of the outer circumferential grooves 43a, 43b, and the expansion seal ring 42 is inserted through the guide holes 44a, 44b.
a, 42b are pressure guiding flexible tubes 41a,
41b. Said expansion seal ring 42
Numerals a and 42b are rubber tubes that expand when a working fluid such as water or gas is forced into them, and are brought into close contact with the inner circumferential wall surface of the in-core housing 17 to form a seal. Expandable seal rings 42a, 42
The outer circumferential grooves 43a and 43b that accommodate the seals b are formed in multiple stages in the seal pipe 32 at different heights in the axial direction, so that damage to one seal ring 42a or 42b will not impair the soundness of the other seal ring. is independent. Expanding seal rings 42a, 42
b can be replaced periodically.

On the other hand, the intermediate pipe 31 is connected to the in-core housing seal support pipe 30 with a normal thread (or a reverse thread), and is connected to the in-core housing seal pipe 32 with a reverse thread (or a normal thread). Therefore, the in-core housing seal support pipe 30 can be connected to the seal pipe 32 at the same time by simply rotating the intermediate pipe 31 in one direction, and the pipe connection work can be simplified.

Next, the operation of the present invention will be explained.

After the in-core monitor detector assembly 15 is pulled out from the target in-core housing 17 by a handling device (not shown) and removed from the reactor core, the in-core housing sealing device 25 is removed by operating the assembly handling device. It is inserted into the in-core housing 17 and installed in the reactor core. At this time, a valved pipe 20 shown in FIG. 8 is attached to the in-core housing flange 18 and held watertight. By installing the valved pipe 20, the RPV boundary is expanded from the in-core housing flange 18 into the valved pipe 20.

After the in-core housing sealing device 25 is attached to the target in-core housing 17, a working fluid is pressurized into the expansion seal rings 42a, 42b through the working fluid source flexible tubes 38a, 38b, etc. to inflate the seal rings 42a, 42b, These expansion seal rings 42a and 42b are pressed against the inner circumferential wall surface of the in-core housing 17. At this time, in order to improve the reliability of the seal of the in-core housing 17, the seal rings 42a and 42b respectively accommodated in the upper and lower outer circumferential grooves 43a and 43b of the in-core housing seal pipe 32 constitute independent seals. There is. After the sealing is completed by the expansion of the expansion seal rings 42a and 42b, the valve 21 of the valved pipe 20 is opened to drain the residual reactor water in the in-core housing 17 and the valved pipe 20, and this drain water is removed. Check the completion of the seal. Even if the valve 21 of the valved pipe 20 opens and the RPV boundary opens, the sealing action of the expansion seal rings 42a and 42b prevents reactor water from falling.

After the sealing action by the expansion seal rings 42a, 42b is completed, the in-core housing flange 18 is replaced. To replace the in-core housing flange 18, remove the valved pipe 20 as necessary, remove the in-core housing flange mounting bolts (not shown), and replace the in-core housing flange 18 with the in-core housing 1.
7 and install a new in-core housing flange 18 in place of the removed in-core housing flange 18. After installing the new in-core housing flange 18, attach the valved pipe (or blind threaded plug) 20 to this flange, and then
Complete the RPV boundary.

After completing the RPV boundary, the inflatable seal rings 42a, 42 of the in-core housing sealing device 25
Remove the working fluid from b and expand the seal ring 42.
Contract a and 42b. After this contraction, the in-core housing sealing device 25 is removed by operating an assembly handling device (not shown) on the operation floor in the same manner as the method for removing the in-core monitor detector assembly 15, and the in-core housing 1 is removed.
7 and store it in another storage location.

On the other hand, the removed in-core monitor detector assembly 15 or the new in-core monitor detector assembly 15 is housed in a predetermined in-core housing 17 by operating the assembly handling device and installed in the core of the nuclear reactor. When the in-core monitor detector assembly 15 is mounted, the lower end of the assembly is held watertight with the in-core housing flange 18 by a metal touch, and is formed by an RPV boundary. After this, the valve 21 of the valved pipe 20 is opened to drain the reactor water in the pipe, and it is confirmed that the seal between the in-core housing flange 18 and the in-core detector assembly 15 is complete. Then, by removing the valved pipe 20 from the in-core housing flange 18, the replacement work of the in-core housing flange 18 is completed.

Note that the expansion seal rings 42a and 42b are made of a highly elastic material such as rubber and are subject to deterioration over time, so they are attached to be replaceable. That is, the impulse flexible tube connectors 40a and 40b are removed from the impulse tube side connectors 39a and 39b,
By pulling out the removed connector and flexible tubes 41a, 41b from the guide holes 44a, 44b, the expansion seal rings 42a, 42b are removed.
and pressure guiding flexible tubes 41a, 41b
can be exchanged together.

〔Effect of the invention〕

As described above, in the in-core housing flange replacement method and the in-core housing seal device used for this replacement according to the present invention,
By pressurizing the working fluid into the expansion seal ring of the in-core housing sealing device and expanding it, it comes into close contact with the inner circumferential wall of the in-core housing and seals the reactor water. The in-core housing flange can be replaced while water is sealed, and there is no need to draw out the reactor water when replacing the in-core housing flange, simplifying the replacement work and reducing the number of work days required for this replacement. It can be shortened.

Therefore, by simply installing the in-core housing sealing device inside the in-core housing, the in-core housing flange can be replaced safely and reliably in a short period of time, saving the reactor shutdown period and increasing the operation of the nuclear power plant. It is possible to improve the reliability of nuclear power plants and reduce operating costs.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a boiling water reactor equipped with a conventional in-core monitor detector assembly, Fig. 2 is an overall view showing the in-core monitor detector assembly installed in the reactor core, and Fig. 3 is a diagram showing a boiling water reactor equipped with a conventional in-core monitor detector assembly. A view showing an in-core guide tube and an in-core housing that accommodate the above-mentioned in-core monitor detector assembly, FIG. 4 is a view showing the installed state of the in-core housing and the in-core housing flange, and FIG. 5 is a view taken along the - line in FIG. 4, Figure 6 shows a plug that closes the in-core guide tube from above the core support plate, Figure 7 is an overall view of a boiling water reactor with an in-core monitor detector assembly installed in the core, and Figure 8 shows the in-core housing. 9 is an overall view showing an embodiment of the in-core housing seal device according to the present invention; FIG. 10 is a view showing the upper part of the in-core housing seal device; FIG. The figure is a vertical sectional view showing the lower part of the in-core housing sealing device. 11...Reactor pressure vessel, 12...Reactor pressure vessel pedestal, 13...Upper grid plate, 14...
...Core support plate, 15...In-core monitor detector assembly, 16...In-core guide tube, 17...In-core housing, 18...In-core housing flange, 20...Pipe with valve (flange sealing body), 25...In-core housing sealing device,
26...Support collar, 27...Body pipe, 28...
Spring, 29... Holding rod, 30... In-core housing seal support pipe, 31... Intermediate pipe, 32... In-core housing seal pipe, 35a, 35b... Support pipe impulse pipe, 38
a, 38b...Flexible tube, 41a,
41b... pressure flexible tube, 42a,
42b... Expanding seal ring, 43a, 43b...
...Outer circumferential groove, 44a, 44b...Guiding hole.

Claims (1)

[Claims] 1. After attaching a flange sealing body such as a valved pipe or a blind plug to the in-core housing flange constituting the reactor pressure vessel boundary, the in-core monitor detector assembly is pulled out from the in-core housing and removed from the reactor core. Then, the in-core housing sealing device is inserted into the in-core housing and this sealing device is installed in the reactor core, and after this installation, working fluid is supplied to the expansion seal ring of the in-core housing sealing device. Press fit and expand to tightly seal the inside of the in-core housing. After this seal is completed, replace the in-core housing flange and attach the new in-core housing flange to the in-core housing. Attach the flange sealing body to the installed in-core housing flange. After installation, pull out the in-core housing seal device from the in-core housing and remove it from the reactor core, then insert the above or new in-core monitor detector assembly into the in-core housing and install it in the reactor core, and drain the reactor water. A method for replacing an in-core housing flange, characterized in that the in-core housing flange can be replaced without any trouble. 2. The in-core housing flange replacement method according to claim 1, wherein the working fluid pressurized into the expansion seal ring of the in-core housing sealing device is water or gas. 3 After inserting the in-core housing sealing device into the in-core housing and completing the seal, drain the reactor water remaining in the in-core housing and flange sealing body, and confirm the seal by the in-core housing sealing device by completing this drain. A method for replacing an in-core housing flange according to claim 1. 4. The in-core housing flange replacement method according to claim 1, wherein the flange sealing body is removed from the in-core housing flange after the in-core monitor detector assembly is inserted into the in-core housing and installed in the reactor core. 5 After inserting the in-core monitor detector assembly into the in-core housing and installing it in the reactor core, drain the reactor water remaining in the flange sealing body, and when this drain is completed, the in-core monitor detector assembly and the in-core housing flange The method for replacing an in-core housing flange according to claim 1, wherein the flange sealing body is removed from the in-core housing flange after confirming the sealing property with the in-core housing flange. 6. An in-core housing sealing device that can be inserted into the in-core housing is installed in the reactor core, and this sealing device includes a main body pipe supported by a core support plate and an upper part of this main body pipe that is elastically supported by a spring. , a retaining rod that removably engages with the upper grid plate, and an in-core housing seal pipe that is provided at the lower part of the main body pipe and that can be inserted into the in-core housing; is equipped with an expandable seal ring that expands freely, and when working fluid is pressurized into this expandable seal ring, the expandable seal ring expands and comes into close contact with the inner circumferential wall of the in-core housing, watertightly sealing the reactor water. An in-core housing seal device used for replacing an in-core housing flange, characterized in that: 7. The in-core housing seal device according to claim 6, wherein the in-core housing seal pipe has outer circumferential grooves formed at a plurality of different locations in the axial direction, and an expansion seal ring is accommodated in each of the outer circumferential grooves. 8. Claim 7, wherein the inflatable seal rings accommodated in the plurality of outer circumferential grooves are each connected to a working fluid source by a connecting pipe having a connector in the middle, and each inflatable seal ring constitutes an independent seal for reactor water. In-core housing sealing device as described in Section. 9. The in-core housing seal device according to claim 6, wherein an in-core housing seal support pipe is attached to the lower part of the main body pipe, and an in-core housing seal pipe is attached to this support pipe via an intermediate pipe. 10. The in-core according to claim 9, wherein the intermediate pipe is screwed onto the in-core housing seal support pipe with a normal thread or a reverse thread, and the in-core housing seal pipe is screwed into the intermediate pipe with a reverse thread or a normal thread. Housing sealing device.