JP2000206288A - Decontamination method for reactor inside - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover and decontaminate secondary waste such as machined powder generated in cutting work on core internals and rearrange for smooth recovery work afterward. SOLUTION: For cutting a shroud 5 in a reactor pressure vessel 4 with an electric spark machine 6, a cyclone separator 13, a pump 14 and a filter 15 are provided in a reactor well 1 and a water purifying device consisting of a pump 38 for water purifying and a filter 39 for water purifying is provided in a fuel pool 2. The filter 39 for water purifying is a filter with filter diameter of 1 μm or less. A plurality of suction hoses 43 are connected by way of a suction header 42 to the pump 38 for water purifying. By this, fine particles including ion components generated in cutting can be recovered and water purity is ensured during the work and recovery efficiency of the cutting powder is simultaneously improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decontamination method in a nuclear reactor for recovering cutting powder generated when a reactor internal structure in a reactor pressure vessel installed in a nuclear power plant is cut.

[0002]

2. Description of the Related Art A first example of a conventional decontamination method in a reactor pressure vessel (also referred to as a reactor) will be described with reference to FIG. FIG.
1 is a schematic sectional view showing a partial system diagram for explaining a system for collecting cutting powder generated when a conventional internal structure of a reactor is cut, in which reference numeral 1 denotes a reactor well, and 2 denotes a reactor well. 1
, A fuel pool 3 for separating the reactor well 1 from the fuel pool 2, a reactor pressure vessel 4 provided below the reactor well 1, and a fuel pressure vessel 5 provided in the reactor pressure vessel 4. 3 shows a shroud, which is one of the furnace internal structures as an object to be cut.

[0003] A cutting blade 7 of an electric discharge machine 6 abuts on a cut surface of a shroud 5 in a reactor pressure vessel 4 and cuts. The electric discharge machine 6 has an operation floor (not shown).
A winch 9 of a refueling machine 8 running above is suspended by a wire 10 to a predetermined position on a cut surface. An operation floor (not shown) is installed in a reactor building (not shown).

A cutting powder collecting port 11 is disposed near the cutting blade 7, and the cutting powder collecting port 11 is connected to the reactor well 1 by a hose 12.
Connected to the cyclone separator 13 installed in the inside, the pump 14 and filter
15 are connected.

At the time of cutting the furnace internals, for example, the shroud 5, the cutting is performed by an electric discharge machine 6.
The cutting powder generated by combining the hose 11, the cyclone separator 13, the pump 14, the filter 15, and the like is collected. However, in the first example, only the vicinity of the cutting portion is sucked.

As a method of cleaning the inside of the reactor pressure vessel 4 for recovering the clad in the reactor pressure vessel 4, as shown in FIGS. , Suction cleaning, sprinkling cleaning, etc. are implemented.

FIG. 17 is a view for explaining wall cleaning as a second example of the conventional example. The wall cleaning is performed by using a brush type washer 16 from the fuel exchanger 8 to the furnace wall with a winch 9.
The collected clad is processed by the filter 15 via the pump 14 by a method of washing by hanging along the 17.

FIG. 18 is a view for explaining a suction cleaning method as a third example of the prior art. In the suction cleaning, the cladding adhered to the baffle plate 18 and the furnace bottom 19 is removed by a suction brush 20.
Using a hose, a hose 12, a pump 14, and a filter.
Processed at 15.

FIG. 19 is a view for explaining a water spray cleaning method as a fourth example of the prior art. In the water spray cleaning, after water in the reactor pressure vessel 4 is discharged, 20 m of water is placed on the furnace upper part 21 and the furnace bottom part 19.
First and second sprinkling / washing devices 22, 23 having a flow rate of about ³ / h
And water is sprayed into the reactor pressure vessel 4 using a water storage tank 24 and a water spray pump 25, and the collected water is sent to the fuel pool 2 through a recovery hose 27 by a recovery pump 26, and the fuel pool 2 is filtered through a filter 28. Has been discharged into In FIG. 19, reference numeral 37 denotes a CRD housing.

In the case where water 29 in the reactor pressure vessel 4 is discharged, as shown in FIG. 20 as a fifth example of the conventional example, an existing reactor coolant purification system (hereinafter referred to as CUW) 30 is used. A method of draining water to a suppression chamber (hereinafter referred to as S / C) 32 through a CUW pump 31 using a
From the temporary hose 34 to the temporary hose 34 via the temporary filter 36 using the temporary pump 35.
Water is drained up to the furnace bottom 19 in combination with the method of discharging to the furnace bottom 32.

[0011]

When cutting is performed using an electric discharge machine or a plasma cutting machine, there is a problem that turbidity cannot be easily removed even if suction cleaning is performed only in the vicinity of the cutting. In addition, if cutting powder is generated, it may not only diffuse from the reactor pressure vessel nozzle or control rod drive mechanism housing to the outside of the reactor pressure vessel, but also recover the cutting powder remaining in the reactor pressure vessel. There was a possibility that the system could survive and shift to the grid, so it was necessary to take measures. When water is drained from the CUW system and the drain at the bottom of the furnace, there is a problem that the dose of the existing system increases due to the presence of the cutting powder, and the dose rate of the filter is too high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is intended to recover a cutting product and to prevent secondary waste such as cutting powder from remaining in a reactor pressure vessel. It is to provide a decontamination method.

[0013]

According to the first aspect of the present invention, an electric discharge machine or a plasma fusing machine is used for a cutting operation for repairing or removing a reactor internal structure in a reactor pressure vessel. A water clarifying device having a filter having a filter diameter of 1 μm or less is provided outside the reactor pressure vessel for the purpose of collecting fine powder that diffuses separately from a cutting powder collecting system for preventing water contamination generated at the time of cutting. A decontamination operation in the reactor pressure vessel is performed.

According to a second aspect of the present invention, the water clarifying device is provided with a water clarifying pump in addition to the filter on an inlet side of the filter, and an ion exchange resin container is connected to an outlet side of the filter. Features.

According to a third aspect of the present invention, an outlet side of a filter of the water dewatering device is connected to an intake port of a fuel pool purifying cooling system provided in a fuel pool, and an ion exchange resin provided in the fuel pool purifying cooling system. It is characterized by being connected to a container.

According to a fourth aspect of the present invention, there is provided a reactor well provided above the reactor pressure vessel during or after the completion of the cutting of the reactor internals, and a cutting powder scattered into the reactor pressure vessel is sucked or brushed. The reactor well is drained, the water in the reactor well is drained to a water level below the level of the flange provided at the upper end opening of the reactor pressure vessel, and the reactor well is washed. It is characterized in that the water in the furnace pressure vessel is drained and sprinkling cleaning is performed.

According to a fifth aspect of the present invention, in the case where water is drained to a furnace bottom in the reactor pressure vessel as a part of a cleaning procedure when the internal structure is cut and removed, Installing a pump to pump water in the reactor pressure vessel into the fuel pool and discharge it through the filter installed in the fuel pool into the fuel pool;
Surplus water is transferred to a suppression chamber or a waste liquid receiving tank provided outside the reactor pressure vessel using the fuel pool purification system for treatment.

According to a sixth aspect of the present invention, a control rod driving mechanism or a neutron measuring tube is provided from a plurality of housings provided at the bottom of the reactor pressure vessel when the reactor internal structure is cut and repaired or removed. If it is pulled out, in order to prevent the cutting powder from entering the housing, a lid is attached to the upper end opening of the housing before cutting, and the cutting powder is collected by cleaning the surface of the lid. It is characterized by the following.

According to a seventh aspect of the present invention, when the control rod driving mechanism or the neutron measuring pipe is pulled out, the control rod driving mechanism or the neutron is drained to prevent the cutting powder from entering the housing. When the measuring tube is pulled out, the drain flushing is performed after performing air bubbling for preventing the cutting powder from entering the housing.

In the invention according to claim 8, when the control rod driving mechanism or the neutron measuring tube is pulled out, the drain flushing is performed after performing air bubbling to prevent the cutting powder from entering the housing. It is characterized by performing.

According to a ninth aspect of the present invention, when cutting and removing the internal structure of the reactor, as a part of a procedure for cleaning the inside of the reactor pressure vessel, water is drained to a furnace bottom in the reactor pressure vessel. After that, at least four high-pressure rotating water spray nozzles of 5 MPa or more are installed on the furnace bottom to perform water washing while draining water from the furnace bottom.

According to a tenth aspect of the present invention, in the water spray cleaning, a low-pressure water spray device is installed at an upper portion and a lower portion of the reactor pressure vessel, and the inside of the reactor pressure vessel is cleaned with the low-pressure water spray device. Water is pumped up by a pump installed at the bottom, purified by a filter installed in the fuel pool, returned to a washing water tank connected to the outlet side of the filter, and supplied for spraying, whereby washing is performed while reusing washing water. It is characterized by the following.

According to an eleventh aspect of the present invention, in the water spray cleaning, a low-pressure water spray device is installed at an upper portion and a lower portion of the reactor pressure vessel, and the inside of the reactor pressure vessel is cleaned with the low-pressure water spray device. A submersible pump is installed at the bottom, water is pumped up by this submersible pump, purified by a filter, and returned to the cleaning tank and subjected to sprinkling to wash the cleaning water while reusing the cleaning water. The cleaning by the high-pressure rotary cleaning nozzle is performed while pulling out.

According to a twelfth aspect of the present invention, in the sprinkling cleaning according to the ninth to tenth aspects of the present invention, after the sprinkling cleaning is performed by a circulation method, the cutting powder remaining on the furnace bottom is cleaned by suction or a suction brush, The suctioned cutting powder is processed using the filter used in the watering and washing.

According to a thirteenth aspect of the present invention, cutting powder generated when the internal structure of the reactor is cut and removed is discharged from the various nozzle portions connected to the reactor pressure vessel to the outside of the reactor pressure vessel. In order to prevent the transfer, a nozzle plug or a hanging curtain is installed in the nozzle portion.

A fourteenth aspect of the present invention is characterized in that a nozzle plug or a hanging curtain is installed in the nozzle portion, and after the plug or the curtain is removed, visual confirmation and cleaning of the nozzle portion are performed.

According to a fifteenth aspect of the present invention, in order to prevent cutting powder generated when the internal structure of the furnace is cut and removed from being transferred from a drain provided at the furnace bottom to another system, the furnace bottom is prevented from being removed. When draining and cleaning the water, a strainer is attached to the drain.

[0028] The invention according to claim 16 is characterized in that, when the internal structure of the furnace is cut and removed, when the water is drained to the furnace bottom as a part of the cleaning procedure, the pump is installed at the furnace bottom. After pumping the water in the reactor pressure vessel to the fuel pool and transferring and filtering the same, the washing water used for the sprinkling cleaning is treated by using the pump and the filter during the sprinkling cleaning. It is characterized in that the devices are shared and used.

According to the first to sixteenth aspects of the present invention, a water clarifying apparatus for removing turbidity during the cutting operation is used. In addition, a nozzle plug, a lid, and a curtain for preventing the cutting powder from moving outside the reactor pressure vessel are used. At the time of draining, the water is lifted out of the reactor pressure vessel by a pump and discharged using the purification system of the fuel pool. After water spray cleaning, jet cleaning of the furnace bottom is performed using a high-pressure cleaning nozzle.

By using the water clarifying device, the fine particle component and the ionic component can be removed, so that the turbidity during the cutting operation can be eliminated and the cutting operation can be efficiently performed. Further, by providing a curtain or a lid to the existing nozzle of the reactor pressure vessel, the control rod drive mechanism housing, and the neutron measurement tube housing, transfer of the cutting powder to the outside of the system is prevented, and cleaning is facilitated.

At the time of draining, the water is lifted out of the reactor pressure vessel by a pump installed in the reactor pressure vessel and discharged to the S / C or the like by using a fuel pool purification system through a filter installed in the fuel pool. As a result, the existing piping is not contaminated, and the dose rate of the existing filter installed near the furnace bottom is increased, so that handling becomes difficult.

After the upper and lower parts of the reactor pressure vessel have been subjected to water spray cleaning, jet cleaning of the furnace bottom using a high-pressure cleaning nozzle can further reduce the dose around the furnace bottom. At this time, by draining the water through the strainer, it is possible to prevent the high-dose clad or cut piece from being discharged out of the system.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a first embodiment of a method for decontamination in a nuclear reactor according to the present invention will be described. In this embodiment, a shroud 5 as a reactor internal structure in a reactor pressure vessel 4 is cut by an electric discharge machine 6, and a decontamination operation is performed using a water clarifying device at the time of a cutting operation for repair or removal. How to do it. In FIG. 1,
The same parts as those in FIGS. 16 to 20 are denoted by the same reference numerals, and description of overlapping parts will be omitted.

Here, the clarifier is shown in FIG.
A pump 38, a filter 39, and a temporary base 40 are mainly used for the freshening pump 38, and suction hoses 41,
A suction header 42, a suction hose 43, and a suction port 44 are provided.

As a system for collecting the cutting powder generated when the shroud 5 is cut by the electric discharge machine 6, the cutting powder collecting port 11, the hose 12, the cyclone separator 13, the pump 14, the filter 15, and the like are combined. At this time, the turbidity of water cannot be completely removed.

Therefore, in order to collect fine powder which is diffused separately from the cutting powder collecting system for preventing the work delay, the clarifying pump 38 and the clarifying filter 39 are connected to the fuel pool 2.
Alternatively, a temporary gantry 40 is provided in the well 1 and installed. A suction hose 41 is connected to the clarifying pump 38, and the other end of the suction hose 41 is connected to a suction header 42.

A plurality of suction hoses 43 are connected to the suction header 42, and their suction ports 44 are suspended in the reactor pressure vessel 4. The suction port 44 is branched by the suction header 42 and is installed above and below the reactor pressure vessel 4. As a result, it is possible to collect the cutting powder from the entire area inside the reactor pressure vessel 4.

The clarifying filter 39 is installed on a temporary gantry 40 for easy replacement. The temporary gantry 40 is of a suspension type from the inner wall surface of the fuel pool 2 or a floor-standing type. The pump 38 is selected according to the size of the suction port 44 in the reactor pressure vessel 4.

In the case of an 800,000 Kw class power plant, the amount of water held in the reactor pressure vessel 4 is about 350 m ³ , so it is necessary to secure a flow rate of at least 60 m ³ / h so that circulation can be performed in about 6 hours. is there. The filter 39 for clarification uses a filter having a diameter of 1 μm or less to remove fine particle components.

Next, a second aspect of the present invention corresponding to claims 2 and 3 will be described.
As a third embodiment, the removal of ionic components at the time of water clarification will be described with reference to FIGS.
When an electric discharge machine or a plasma cutting machine is used as the cutting method, ion components are generated, but cannot be collected by a filter. Therefore, in the second embodiment, as shown in FIG. 2 in the first embodiment, an ion exchange resin container 45 is installed before or after connecting a water clarification filter 39 to a water clarification pump 38. . As a result, ionic components can be removed and water can be clarified.

In the third embodiment, as shown in FIG. 3, in order to easily treat ionic components without using an ion exchange resin container 45, a filter for clarifying water in the first embodiment is used. The outlet 39 may be installed near the water intake 47 of the fuel pool purification system via the hose 46. In this case, after the cut powder is collected by the water clarifying filter 39, the ion component can be purified using the purification pump 49 and the ion exchange resin container 45 of the fuel pool purification system 48. The outlet side of the ion exchange resin container 45 is disposed in the fuel pool 2 by a return hose 50.

Next, as a fourth embodiment corresponding to the invention of claim 4, a nuclear reactor in which cutting powder is generated by cutting the internal structure shown in FIGS. 1 to 3 according to FIG. The decontamination procedure in the pressure vessel 4 will be described.

During the cutting, the cut powder is collected by using both the cutting powder collecting device and the water clarifying device. Cutting powder is collected by the collecting device during cutting.
Since 100% cannot be recovered, it is necessary to sequentially recover the cut powder even after cutting is completed. The collection time is desirably after the end of the cutting, but may be parallel work during the cutting.

First, the cutting powder scattered on the reactor well 1 is collected by a suction device or a suction cleaning device with a brush.
Thereafter, the inside of the reactor pressure vessel 4 is cleaned so that even if the cutting powder moves into the reactor pressure vessel 4, the reactor pressure vessel 4
It can be collected by suction and brush cleaning.

Next, the cutting powder scattered in the reactor pressure vessel 4 is collected by suction or a suction device with a brush. This operation should be performed prior to draining wells and decontaminating wells, since draining the water impairs workability. Subsequently, the water in the reactor well is drained.

As a method of draining water, there are a method of transferring water to a well fuel pool by a temporary pump and draining the water using a line of a fuel pool purification system, and a method of draining water using a fuel pool purification system itself. But it doesn't matter. After draining, the water level is set to the level before and after the RPV flange, and the reactor well is washed by watering or brushing.

After ensuring workability on the wells, a sprinkling washing device is installed, and water is pumped into the fuel pool using the pump or the throwing pump used for sprinkling washing.
The water is transferred to the S / C or the existing waste liquid receiving tank via the fuel pool purification system. Unless a water sprinkling cleaning device is installed in advance, the device cannot be installed due to the high dose after the water has completely drained from the furnace. If water comes out to the bottom of the furnace, perform water spray cleaning.

By this series of methods, the cut powder can be collected from the upper part of the furnace without returning work. In addition, after the cutting powder is collected by performing the water spray cleaning, if the reactor pressure vessel 4 is again filled with water and the furnace bottom suction cleaning is performed, the cleaning effect can be further improved.

Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is a method of draining water to the reactor bottom when cutting powder remains in the reactor pressure vessel 4.

A pump 53 is installed at the bottom 19 of the reactor, and the water 29 in the reactor pressure vessel 4 is pumped up to the fuel pool 2 via the hose 52 via the hose 52, and the filter 53 is installed in the fuel pool 2.
Through the fuel pool 2. Although the fuel pool 2 closes the gate 3 and generates excess water, the fuel pool 2 passes through the fuel pool purification system 48, the purification system pump 49, and the ion exchange resin container 45.
Surplus water is treated by S / C through drain hose 54
32 or transferred to the existing waste liquid receiving tank.

In the conventional example, when water is drained from the drain of the furnace bottom 19, the water is discharged through the temporary filter 36 shown in FIG.
There was a problem that the surface dose increased and the handling became difficult, but this can be avoided.

Further, since the pipe of the drain 33 of the furnace bottom 19 is narrow, a flow rate of at most about 15 m ³ / h can be normally secured at most.
There is a problem that it takes one day to drain 350 tons of water and the drainage time increases.

However, when the pump 51 is used, the drainage time can be reduced to less than half by using a pump of 30 m ³ / h or more, or by installing a plurality of pumps in parallel. Since the pump 51 is installed at the bottom 19 of the furnace, a head of 30 m or more is required.

Next, a sixth embodiment corresponding to the invention of claim 6 will be described with reference to FIGS. 6 (a) and 6 (b). The present embodiment is a method for preventing cutting powder from entering the inside of the CRD housing 37 when the control rod driving mechanism or the neutron measuring tube is pulled out when cutting powder is generated at the time of cutting. .

That is, in this embodiment, as shown in FIG. 6B, the upper part of the CRD housing 37 is partially enlarged in FIG. That is, a temporary lid 55 is attached to the part before cutting.

The lid 55 needs to be provided with an edge 56 so as not to fly by watering and washing, or to have a fastening mechanism. When the lid 55 is attached, even when cleaning the inside of the reactor pressure vessel 4, by cleaning the upper part of the lid 55, the cutting powder can be easily collected.

Next, a seventh embodiment of the present invention will be described with reference to FIGS. 7 (a) and 7 (b). In the present embodiment, when the control rod drive mechanism or the neutron measurement tube is pulled out when cutting powder is generated at the time of cutting, the cutting powder enters the inside of the CRD housing 37. It is a collection method.

As shown in FIG. 7 (b), a part A of FIG.
When 57 enters, it accumulates in a temporary flange 58 provided at the lower part of the CRD housing 37. At this time, the water level is at least
Drain flushing can be performed by opening the valve 59 attached to the temporary flange 58 at a point of time of 10 m or more. The drained water is discharged through a temporary hose 34 to a S / C 32 via a temporary pump 35 and a temporary filter 36.

Next, an eighth embodiment corresponding to the invention of claim 8 will be described with reference to FIGS. 8 (a) and 8 (b). This embodiment is a decontamination method that can be more effectively implemented in a housing such as a control rod drive mechanism or a neutron measurement tube in the fifth embodiment.

In this embodiment, as shown in FIG. 8 (b), a part A in FIG. 8 (a) is partially enlarged, and a three-way drain is attached to a valve 59 attached to the lower end of the CRD housing 37. A hose 60 is connected, an air hose 62 is connected to a branch end of the drain hose 60 via an air supply valve 61, and a temporary hose 34 is connected to a lower end of the drain hose 60. Then, the air hose 62 is connected to the air supply device 63 as shown in FIG.

Since the temporary flange 58 has a step, there is a case where the cut piece 57 of the temporary flange 58 cannot be sufficiently washed away only with the drain. At this time, air bubbling can be performed by connecting an air supply device 63 such as an in-house air system (SA) or a cylinder in the middle of the drain hose 60 and twisting the air supply valve 61.

As a result, since the cut pieces 57 and the clad of the temporary flange 58 can be easily peeled off, the decontamination can be effectively performed by subsequently performing the draining. The air supply pressure depends on the water depth, but is preferably 3 atm or more.

Next, a ninth embodiment corresponding to the ninth aspect of the present invention will be described with reference to FIGS. 9 (a) and 9 (b). The present embodiment is a sprinkling cleaning method performed after draining water up to the furnace bottom 19. After draining the water to the furnace bottom 19, the high-pressure rotary sprinkling nozzle 64 having an original pressure of 5 MPa or more is cut by a jet pump diffuser (not shown), and FIG.
As shown in the figure, the baffle plate 18 is installed in the hole 18a.

It is desirable that the high-pressure rotating sprinkling nozzles 64 are provided at four positions at a pitch of at least 90 degrees. Fig. 9
As shown in (a), it is sent from the high-pressure nozzle pump wheel 65 to the furnace bottom 19 via the high-pressure hose 66 and the valve 67.

Even if four or more high-pressure rotary watering nozzles 64 are not installed in advance, the same effect can be obtained by moving the high-pressure rotary watering nozzle 64 each time cleaning is completed at one location and cleaning at four or more locations. Obtainable. At this time, in order to obtain the decontamination effect up to the furnace bottom 19, it is important to drain and wash the water while treating the furnace bottom 19 with the temporary hose 34, the temporary pump 35, and the temporary filter 36. In FIG. 9, reference numeral 68 denotes a partition wall.

Next, a tenth embodiment according to the tenth aspect of the present invention will be described with reference to FIG. This embodiment relates to a procedure of watering and washing. In the water spray cleaning performed after draining up to the furnace bottom 19 as a cleaning procedure, an upper water spray cleaning device 69 is installed above the reactor pressure vessel 4 and a lower water spray cleaner 70 is installed below the reactor pressure vessel 4. The inside of the reactor pressure vessel 4 is sprinkled and washed, and water is pumped up by a pumping pump 51 installed in the furnace bottom 19, purified by a filter 53, and returned to a hose.
The water is returned to the washing water tank 73 through 72 to be sprayed. As a result, since the washing can be performed while reusing the washing water, there is an advantage that the amount of water used is reduced. In FIG. 10, reference numeral 74 denotes a temporary lid for closing the upper end opening of the reactor pressure vessel 4.

Next, referring to FIG. 11, a flow of a watering and washing procedure using FIGS. 9 and 10 as an eleventh embodiment corresponding to the inventions of claims 11 and 12 will be described. FIG. 11 shows a flow of the water spray cleaning procedure. In FIG. 10, after installing the upper and lower water spray cleaning devices 69 and 70 in the reactor pressure vessel 4, the furnace bottom 19 in the reactor pressure vessel 4 is set. In the sprinkling washing performed by draining the water until the water is washed, the upper sprinkling washing device 69 and the lower sprinkling washing device 70 are sequentially used for washing, and then the furnace bottom portion 19 is cleaned.
Then, a high-pressure rotary cleaning nozzle 64 shown in FIG. 9 is inserted into the reactor pressure vessel 4 to thereby strongly clean the furnace bottom 19.

In the invention corresponding to claim 12, as a part of a cleaning procedure for collecting cutting powder generated when cutting and removing, for example, the shroud 5 as a reactor internal structure in the reactor pressure vessel 4. This is a sprinkling cleaning method performed after draining water to the furnace bottom 19.

That is, after performing water spray cleaning in a circulation system, the cut powder remaining in the furnace bottom 19 is cleaned by suction or a suction brush, and the filter used in the water spray cleaning is used.
The sucked cutting powder is processed.

Next, a twelfth embodiment according to the present invention will be described with reference to FIG. In the present embodiment, a nozzle curtain is provided to prevent migration of cutting powder. In order to prevent cutting powder generated when the internal structure of the reactor is cut and removed from the reactor from the main steam nozzle 75 or the water supply nozzle 76 connected to the reactor pressure vessel 4 to the outside of the reactor pressure vessel 4, The main steam nozzle 75 is provided with a nozzle plug 77, and the water supply nozzle 76 is provided with a hanging curtain 78. Thereby, decontamination can be easily performed without transferring the cutting powder outside the reactor pressure vessel 4. The nozzle plug 77 or the curtain 78 is fixed by using the stud bolt 79 of the reactor well 1 or the handrail 80 on the operation floor as a fall prevention.

Next, a thirteenth embodiment of the present invention will be described with reference to FIG. In this embodiment, the underwater television camera 81 suspended by the wire 10 after removing the nozzle plug 77 or the curtain 78 as shown in FIG.
The nozzle portion is visually checked and cleaned using the brush suction device 82. Thereby, it can be confirmed that there is no transfer of the cutting powder to the outside of the nozzle.

Next, a fourteenth embodiment corresponding to the invention of claim 15 will be described with reference to FIGS. 14 (a) and 14 (b). In this embodiment, when water is drained from the furnace bottom 19 as part of the decontamination, FIG. 14 (b) is used to prevent cutting powder from transferring from the drain 33 of the furnace bottom 19 to another system. As shown in part A of FIG. 14A in a partially enlarged manner, a drain strainer 83 is used.

That is, the strainer 83 is inserted into the drain 33 of the furnace bottom 19 and fixed. The discharged water flowing out of the drain 33 is discharged to the S / C through a temporary filter 36 via a temporary hose 34 and a temporary pump 35 as shown in FIG.

Next, a fifteenth embodiment of the present invention will be described with reference to FIGS. 15 (a) and 15 (b). The present embodiment relates to drainage of water to the furnace bottom 19 and cleaning with water, which are performed during cleaning. When water is drained to the furnace bottom 19, a recovery pump 26 is installed in the furnace bottom 19, water 29 in the reactor pressure vessel 4 is pumped into the fuel pool 2 and transferred using the filter 28, As shown in FIG.
The inside of the reactor pressure vessel 4 is sprinkled and washed by using the sprinkling and washing device 22 and the second sprinkling and washing device 23.

According to the present embodiment, the outlet side of the filter 28 in the fuel pool 2 is connected to the first and second watering and washing devices 2.
2 and 23, and the collection pump 26 and the first and second sprinkling / washing devices 22 and 23 can be used in common.

[0076]

According to the present invention, it is possible to completely collect the cutting powder generated when the internal structure of the reactor pressure vessel is cut, and to reduce the exposure of the workers accompanying the cutting powder. Thus, the safety of the recovery work performed after the disconnection can be ensured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view for explaining a first embodiment of a decontamination method in a nuclear reactor according to the present invention.

FIG. 2 is a schematic sectional view for explaining a second embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 3 is a schematic sectional view for explaining a third embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 4 is a flow chart for explaining a fourth embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 5 is a schematic sectional view for explaining a fifth embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 6A is a schematic sectional view for explaining a sixth embodiment of the decontamination method in a nuclear reactor according to the present invention, and FIG. 6B is an enlarged view of a portion A in FIG. Front view.

FIG. 7A is a schematic cross-sectional view for explaining a seventh embodiment of the decontamination method in a nuclear reactor according to the present invention, and FIG. 7B is an enlarged view of part A of FIG. Front view.

FIG. 8A is a schematic cross-sectional view for explaining an eighth embodiment of the decontamination method in a nuclear reactor according to the present invention, and FIG. 8B is an enlarged view of part A of FIG. Front view.

FIG. 9A is a schematic cross-sectional view for explaining a ninth embodiment of the decontamination method in a nuclear reactor according to the present invention, and FIG. 9B is a view in the direction of arrows AA in FIG. FIG.

FIG. 10 is a schematic sectional view for explaining a tenth embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 11 is a flow chart for explaining an eleventh embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 12 is a schematic sectional view for explaining a twelfth embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 13 is a schematic sectional view for explaining a thirteenth embodiment of the decontamination method in a nuclear reactor according to the present invention.

FIG. 14A is a schematic cross-sectional view for explaining a decontamination method in a nuclear reactor according to a fourteenth embodiment of the present invention, and FIG.
FIG. 2 is a schematic diagram showing an enlarged part A of FIG.

FIG. 15A is a schematic cross-sectional view for explaining a fifteenth embodiment of the decontamination method in a nuclear reactor according to the present invention, and FIG.
FIG. 2 is a schematic cross-sectional view showing a sprinkling state after drainage in (a).

FIG. 16 is a schematic cross-sectional view showing a first example of a conventional decontamination method in a nuclear reactor.

FIG. 17 is a schematic cross-sectional view showing a second example of a conventional decontamination method in a nuclear reactor.

FIG. 18 is a schematic sectional view showing a third example of the conventional decontamination method in a nuclear reactor.

FIG. 19 is a schematic sectional view showing a fourth example of the conventional decontamination method in a nuclear reactor.

FIG. 20 is a schematic cross-sectional view showing a fifth example of the conventional decontamination method in a nuclear reactor.

[Explanation of symbols]

1 ... reactor well, 2 ... fuel pool, 3 ... gate, 4 ...
Reactor pressure vessel, 5: shroud, 6: electric discharge machine, 7
... cutting blade, 8 ... refueling machine, 9 ... winch, 10 ... wire, 11 ... cutting powder collecting port, 12 ... hose, 13 ... cyclone separator, 14 ... pump, 15 ... filter, 16 ... brush type washer, 17 ... Furnace wall, 18… Baffle plate, 18a… Hole,
19: Furnace bottom, 20: Suction brush, 21: Furnace top, 22: First sprinkling / washing device, 23: Second sprinkling / washing device, 24: Water storage tank, 25: Sprinkling pump, 26: Recovery pump, 27 ... Collection hose, 28 ... Filter, 29 ... Water, 30 ... Reactor coolant purification system (CUW), 31 ... CUW pump, 32 ... Suppression chamber (S / C), 33 ... Drain, 34 ... Temporary hose, 35 ...
Temporary pump, 36 ... Temporary filter, 37 ... CRD housing, 38 ... Pump for clarification, 39 ... Filter for clarification,
40 ... Temporary stand, 41 ... Suction hose, 42 ... Suction header, 43 ...
Suction hose, 44… Suction port, 45… Ion exchange resin container, 46
… Hose, 47… Intake, 48… Fuel pool purification system, 49…
Purification pump, 50… Return hose, 51… Pumping pump, 52
… Hose, 53… Filter, 54… Drain hose, 55… Lid, 56
… Edge, 57… cut piece, 58… temporary flange, 59… valve, 60
… Drain hose, 61… air supply valve, 62… air hose, 63… air supply device, 64… high-pressure rotating watering nozzle, 65…
High pressure nozzle pump truck, 66… High pressure hose, 67… Valve, 68… Partition wall, 69… Upper sprinkler / washer, 70… Lower sprinkler / washer,
71 ... watering pump, 72 ... return hose, 73 ... washing water tank,
74 ... temporary lid, 75 ... main steam nozzle, 76 ... water supply nozzle, 77 ...
Nozzle plug, 78… curtain, 79… stud bolt, 80
… Railing, 81… TV camera, 82… brush suction device, 83
... Drain strainer.

Claims (16)

[Claims] An electric discharge machine or a plasma fusing machine or the like is used for cutting or repairing or removing a reactor internal structure in a reactor pressure vessel. A decontamination operation inside the reactor pressure vessel by providing a water clarification device having a filter with a filter diameter of 1 μm or less outside the reactor pressure vessel for the purpose of collecting fine powder diffused separately from the cut powder recovery system for preventing Decontamination method in a nuclear reactor. 2. The water clarification device according to claim 1, further comprising a water clarification pump in addition to the filter on an inlet side of the filter, and an ion exchange resin container connected to an outlet side of the filter. 2. The method for decontamination in a nuclear reactor according to 1. 3. An outlet side of a filter of the water dewatering device is connected to an intake of a fuel pool purifying cooling system provided in the fuel pool, and is connected to an ion exchange resin container provided in the fuel pool purifying cooling system. The method for decontamination in a nuclear reactor according to claim 1, wherein: 4. A cutting device scattered in the reactor well and the reactor pressure vessel provided above the reactor pressure vessel during or after the cutting of the internal structure of the reactor or after the cutting is completed, is collected by a suction device with a suction or a brush. Then, the water in the reactor well is drained to a water level equal to or lower than the level of the flange provided at the upper end opening of the reactor pressure vessel, and the reactor well is washed. The method for decontamination in a nuclear reactor according to any one of claims 1 to 3, wherein the water is drained and washed with water. 5. A pump is installed at the bottom of the reactor when water is drained to the bottom of the reactor pressure vessel as part of a cleaning procedure when the internal structure is cut and removed. Then, water in the reactor pressure vessel is pumped into the fuel pool, discharged through the filter installed in the fuel pool, into the fuel pool, and discharged into the reactor using the fuel pool purification system. 4. The decontamination method in a nuclear reactor according to claim 1, wherein the decontamination method is carried out by transferring to a suppression chamber or a waste liquid receiving tank provided outside the pressure vessel. 6. When a control rod drive mechanism or a neutron measurement tube is pulled out from a plurality of housings provided at the bottom of the reactor pressure vessel when cutting and repairing or removing the internal structure of the reactor. In order to prevent the cutting powder from entering the housing, a lid is attached to an upper end opening of the housing before cutting, and the cutting powder is collected by cleaning the surface of the lid. The method for decontamination in a nuclear reactor according to claim 1. 7. When the control rod drive mechanism or the neutron measurement tube is pulled out, drain flushing is performed to prevent the cutting powder from entering the housing. Decontamination method in nuclear reactor. 8. When the control rod driving mechanism or the neutron measuring tube is pulled out, the drain flushing is performed after performing air bubbling to prevent the cutting powder from entering the housing. Claim 7
The method for decontamination in a nuclear reactor as described in the above. 9. When cutting and removing the internal structure of the reactor, after draining water to the bottom of the reactor pressure vessel as part of a procedure for cleaning the inside of the reactor pressure vessel, 9. The decontamination method in a nuclear reactor according to claim 1, wherein at least four high-pressure rotary spray nozzles of 5 MPa or more are installed at the bottom of the furnace to spray water while draining water from the bottom of the furnace. 10. In the water spray cleaning, a low-pressure water spray device is installed at an upper portion and a lower portion of the reactor pressure vessel, and the inside of the reactor pressure vessel is washed with the low-pressure water spray device and pumped up at the bottom of the reactor. The water is pumped up, purified by a filter installed in the fuel pool, returned to the washing water tank connected to the outlet side of the filter, and sprinkled to wash while reusing washing water. The method for decontamination in a nuclear reactor according to claim 1. 11. In the water spray cleaning, a low-pressure water spray device is installed at each of an upper portion and a lower portion of the reactor pressure vessel, and the inside of the reactor pressure vessel is cleaned with the low-pressure water spray device. Is installed, the water is pumped up by this submersible pump, purified by a filter, and returned to the washing tank and subjected to sprinkling to wash the washing water while reusing it.After removing the washing water from the furnace bottom, the high pressure is applied. 11. The decontamination method in a nuclear reactor according to claim 9, wherein cleaning is performed by a rotary cleaning nozzle. 12. In the water spray cleaning, after water cleaning is performed by a circulation method, the cutting powder remaining on the furnace bottom is cleaned by suction or a suction brush, and the suction is performed using a filter used in the water cleaning. 12. The decontamination method in a nuclear reactor according to claim 9, wherein the cut powder is treated. 13. Prevention of cutting powder generated when the internal structure of the reactor is cut and removed from various nozzle portions connected to the reactor pressure vessel to move out of the reactor pressure vessel. 13. The decontamination method in a nuclear reactor according to claim 1, wherein a nozzle plug or a hanging curtain is installed in each of the various nozzle portions for passing. 14. The reactor according to claim 13, wherein a nozzle plug or a hanging curtain is installed in the nozzle portion, and the nozzle portion is visually checked and cleaned after the plug or the curtain is removed. Decontamination method inside. 15. Draining cleaning of the furnace bottom is performed to prevent cutting powder generated when the furnace internal structure is cut and removed from being transferred from a drain provided in the furnace bottom to another system. 15. The method according to claim 1, wherein a strainer is attached to the drain. 16. When the internal structure of the reactor is cut and removed, when the water is drained to the bottom of the furnace as part of a cleaning procedure, the pump is installed at the bottom of the furnace to remove the reactor. After pumping the water in the pressure vessel to the fuel pool and transferring and filtering the same, the apparatus is shared by processing the washing water used for the sprinkling cleaning by using the pump and the filter during the sprinkling cleaning. 16. The method for decontamination in a nuclear reactor according to claim 1, wherein the method is used.