JP2859240B2 - Preventive maintenance device in reactor vessel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preventive maintenance device in a reactor vessel, and more particularly to a reactor vessel suitable for performing water jet peening in a reactor pressure vessel of a boiling water reactor. Related to preventive maintenance devices.

[0002]

2. Description of the Related Art Preventive maintenance for preventing stress corrosion cracking (SCC) by improving the tensile residual stress existing in a metal material by causing cavitation bubbles generated by injecting a liquid jet to the metal member to improve the tensile residual stress existing in the metal material. The technology is described in Japanese Patent Application Laid-Open No. 4-362124. An apparatus for applying the preventive maintenance technology to a reactor pressure vessel is disclosed in Japanese Patent Application Laid-Open Nos. 5-195052 and 5-78738.

[0003] However, those devices require a large number of CRDs.
(Control rod drive mechanism) It was not suitable for preventive maintenance work at the bottom of the reactor pressure vessel where the stub tube, ICM (in-reactor detector) housing, and CRD housing stand. For this reason, a technique described in Japanese Patent Application Laid-Open No. 52-130409 has been considered as a method of alleviating the residual stress of a piping shape such as a CRD stub tube, a CRD housing, and an ICM housing.

[0004] This is a method for alleviating the residual stress in a welded portion of a pipe having a normal single cylindrical structure. That is, while the inner surface of the pipe is cooled by running water, rapid heating is performed by a heating coil provided on the outer surface of the welded portion of the pipe. By this heating, a temperature distribution necessary for improving the residual stress was generated within the thickness of the pipe, and the inner surface of the welded portion was subjected to tensile yield, and a compressive stress was left upon complete cooling. This prior art is extremely effective in relieving residual stress in a welded portion of a pipe having a single cylindrical structure.

[0005]

However, this conventional technique is intended to alleviate the residual stress on the inner surface of the pipe, and is also used as it is for a CRD stub tube, a CRD housing, and an IC.
Even when applied to the welded part of the M housing and the bottom of the reactor pressure vessel, the CRD stub tube and the CRD housing are partially double pipes, and a considerable amount of heating is required to cause a tensile yield to the bottom of the reactor pressure vessel. Is expected and difficult.
In addition, CRD stub tubes, C
The number of RD housings and ICM housings depends on the output of the nuclear power plant, but is as large as 102 to 240. If one is installed one by one, it takes a very long time and the efficiency is low.

In a plant at the beginning of nuclear power generation, a stainless steel CRD, ICM housing or a nickel-base alloy made of a relatively high carbon content, which is susceptible to stress corrosion cracking (SCC) due to welding heat (called sensitization). CRD
A stub tube was used. The potential for the occurrence of stress corrosion cracking to be solved by the present invention increases when the above-mentioned sensitization, tensile stress and corrosive environment are superimposed. Also,
The target location for preventing stress corrosion cracking to be solved by the present invention depends on the output of the nuclear power plant, but a large number from 102 to 240, and it is very time-consuming and inefficient to construct one by one, It is expected that the impact on the regular inspection period of nuclear plants will be large.

When a preventive maintenance device using cavitation bubbles is used in water in a reactor pressure vessel, part of the cavitation bubbles wraps around a radioactive cladding and floats on the surface of the water. There is a risk of radioactive contamination of the space. An object of the present invention is to provide a preventive maintenance device in a reactor vessel that can suppress radioactive contamination from a water surface in a reactor vessel to an upper space.

[0008]

A first aspect of the present invention for achieving the above object is as follows.
The feature of the invention of the present invention is that, in water in a nuclear reactor vessel, an atomizing nozzle which jets a water flow accompanied by generation of cavitation bubbles from an injection nozzle toward a structural material for improving residual stress to impart a compressive residual stress to the structural material In the preventive maintenance device in the reactor vessel, when the water stream is injected from the injection nozzle, a gas collecting cover for collecting gas rising from the water in the reactor vessel toward the water surface is provided. .

[0009] Cavitation bubbles generated in the operation of improving the stress of the structural material in the water in the nuclear reactor vessel float with the radioactive material toward the water surface. The gas in the air bubbles is collected by the air collecting cover. For this reason,
Radioactive contamination from the water surface to the upper space can be suppressed.

[0010] The features of the second invention for achieving the above object are as follows.
A fixing structure detachably mounted on a cylindrical body disposed in a reactor vessel, a revolving body mounted on the fixing structure so as to be horizontally revolvable, and a revolving surface and an angle of the revolving body on the revolving body And a multi-joint arm mounted so as to be able to swing freely on the surface of the multi-joint arm, and the spray nozzle supported by the multi-joint arm.

A water jet is sprayed from a spray nozzle to a plurality of preventive maintenance objects by rotating a revolving body and swinging an articulated arm with respect to a fixing structure detachably set on a cylindrical body. The generated cavitation bubbles collide with each other, thereby improving the stresses of the plurality of preventive maintenance targets to compressive residual stresses.

[0012] The features of the third invention for achieving the above object are as follows.
An injection nozzle is provided on the articulated arm such that the injection center of the injection nozzle is eccentric with respect to the center of the cylindrical body.

Since the injection center of the injection nozzle is eccentric with respect to the center of the cylindrical body, the cavitation bubbles are circulated to the rear side along the cylindrical body, so that the preventive maintenance target area can be expanded.

The features of the fourth invention for achieving the above object are as follows.
The ejection nozzle is an eccentric nozzle in which the ejection center of the ejection nozzle is eccentric with respect to the center of the cylindrical body in the horizontal direction.

According to a fourth aspect, the operation of the third aspect is as follows.
It can be obtained by using an eccentric nozzle in which the ejection center of the ejection nozzle is eccentric in the horizontal direction with respect to the center of the cylindrical body.

A fifth aspect of the present invention for achieving the above object is as follows.
The articulated arm is provided with an exchange mounting means for an injection nozzle whose injection center is eccentric with respect to the center of the cylindrical body and an injection nozzle which is not eccentric.

Since the replacement mounting means is provided, the preventive maintenance area can be changed by replacing the injection nozzle.

A feature of the sixth invention for achieving the above object is that
It has a means for sucking underwater cladding.

Since clad suction means is provided,
The activated cladding soared in the bottom of the reactor vessel can be sucked in by the injection energy of the water jet ejected from the injection nozzle. For this reason, the activated cladding is suppressed from freely rising from the bottom of the reactor vessel to the reactor water surface, and the radiation contamination by the cladding is prevented from being expanded above the reactor water surface. .

A seventh aspect of the present invention for achieving the above object is as follows.
It has an exhaust duct for ventilation and air conditioning that communicates with the air collecting cover.

By connecting the air collecting cover to the ventilation air-conditioning exhaust duct, the gas containing contaminants collected by the air collecting cover is exhausted through the ventilation air-conditioning exhaust duct to collect the gas floating on the water surface. It can be done continuously.

The features of an eighth invention for achieving the above object are as follows.
An exhaust duct for ventilation and air conditioning communicates with the air collecting cover through a filter for capturing contaminants.

By providing a filter, contaminants accompanying the trapped gas can be removed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
A configuration of a preventive maintenance device in a reactor vessel according to one embodiment of the present invention applied to an R power plant will be described.

Although not shown in the drawings, the reactor pressure vessel lid, the steam dryer, the steam separator, the fuel assembly,
The control rod, the in-furnace detector (ICM), the fuel support bracket, the control rod drive mechanism (CRD), the control rod guide tube, etc. are sequentially removed.

The preventive maintenance device 1 is connected to a hoist crane 4 of a refueling trolley 3 installed on an operating floor 2 of a reactor building by a wire rope 5,
The preventive maintenance device 1 is set at a predetermined position by moving and reversing the refueling trolley 3 and raising and lowering the hoist crane 4. Although not shown in the drawings, the preventive maintenance device 1 is set up by setting a base on the flange 7 of the reactor pressure vessel 6 and setting a base on the base that is rotatable around the center of the reactor pressure vessel 6. Each of the movable carts is provided on the upper surface of the swivel cart so as to be movable in the radial direction.
May be performed on a work platform having an elevating device for elevating and lowering to set a predetermined position.

The operation of setting the preventive maintenance device 1 includes the monitoring camera 8 attached to the preventive maintenance device 1 and the preventive maintenance device 1
This is performed while monitoring the video from the independent monitoring camera 9. The image of the surveillance camera 8 is displayed on a monitor 12 incorporated in a control panel 11 via a cable 10.
This image confirms particularly the gap between the preventive maintenance device 1 and the lattice of the upper lattice plate 13 and the positional relationship between the fuel support fitting hole 15 of the core support plate 14 and suspends the preventive maintenance device 1 so as not to interfere as much as possible. . The video of the surveillance camera 9 is displayed on a monitor 16 installed near the control panel 11. Based on this image, the positional relationship between the preventive maintenance device 1 and other internal structures and the position of the preventive maintenance device 1 ascending and descending are confirmed. The operator moves the surveillance camera 9 by moving the cable 17 of the surveillance camera 9 and the rope 18 attached to the tip of the surveillance camera 9 on the fuel exchange cart 3.
FIG. 8 shows the mounting position of the monitoring camera 8 mounted on the preventive maintenance device 1.

On the operating floor 2, a control panel 11 for remotely controlling the preventive maintenance device 1 and a high-pressure pump 19 for supplying water equivalent to reactor water at a high pressure are installed. Although not shown, the high-pressure pump 19 can also be installed in a space other than the operating floor 2, for example, in the large entrance of the reactor building or in an empty space inside the reactor building. At this time, the high-pressure hose 20 connecting the high-pressure pump 19 and the preventive maintenance device 1 is extended. The control panel 11 includes a control cable 2 for transmitting and receiving electric signals for remotely operating the preventive maintenance device 1.
1. An air hose 22 for supplying air for remotely operating the preventive maintenance device 1 and a control cable 23 for transmitting and receiving an electric signal for remotely operating the high-pressure pump 19 are connected to each device to remotely operate each device. Remote operation is manual,
An automatic mode can be selected. Basically, construction is automatically performed, and adjustment of the position of the injection nozzle 24 is manually performed. The control panel 11 can adjust the respective operating speeds of lifting and lowering, rotating, and swinging the injection nozzle 24 and the pitch to optimal values for the construction. Each drive mechanism will be described with reference to FIG.

The operating air for remotely operating the preventive maintenance device 1 is guided from the air supply source of the reactor building to the control panel 11 via the air hose 25, and the valve in the control panel 11 is controlled to control the preventive maintenance device 1. Remote control. Although illustration is omitted, air for remotely operating the preventive maintenance device 1 is as follows.
It is also possible to provide a compressor other than the air supply source of the reactor building and supply air to the air hose 25.

In the configuration for supplying high-pressure water to the preventive maintenance device 1, water equivalent to reactor water is supplied to the high-pressure pump 19 from a reactor building and a water supply source in the vicinity thereof through a low-pressure hose 26 to increase the pressure. Although not shown, the water supplied to the high-pressure pump 19 is not limited to a water supply source in the reactor building and the vicinity thereof, and is also a pure water production in which ordinary water is adjusted to a water quality that does not cause a problem even if it is put into the reactor. Pure water may be supplied via the device. Further, as shown in FIG.
It is also possible to supply the high pressure pump 19 with the circulation pump 27 via a filter 69 for removing the clad floating in the reactor water. In this case, the reactor water 28 is pressurized by the high-pressure pump 19, is then injected from the injection nozzle 24, and returns to the inside of the furnace to form a circulation system.

The pressurized water (reactor water 28 in the case of the circulation system of FIG. 2) is supplied to the preventive maintenance device 1 through the high-pressure hose 20.
Nozzle 2 attached to the preventive maintenance device 1
4, cavitation bubbles 30 are generated.

It should be noted that the cavitation bubbles 3
Radioactive oxidation sedimented at the bottom of the reactor pressure vessel 6, causing a collapse pressure of 0 and a wind-up from the water stream due to the high-pressure water jet, resulting in poor visibility of the surveillance cameras 8, 9 and an increase in atmospheric dose. The clad mainly composed of iron is collected by a clad collecting device 32 having a suction port 31. The clad recovery device 32 includes a suction port 31, a clad transfer hose 33, and a clad transfer pump 34. The clad sucked together with the reactor water 28 is captured by a filter 35 in the clad recovery device 32. The reactor water 28 with the clad captured is returned to the spent fuel pool 37 via the discharge hose 36. Although not shown, the filter 35 having captured the clad is packed as a highly radioactive waste in a container such as a drum with a shield and stored in a nuclear power plant.

Among the cavitation bubbles 30 generated by the high-pressure water injection, those that reach the reactor water surface 38 without collapsing contain the above-mentioned radioactive cladding,
When collapsing at the reactor water surface 38, there is a risk of contamination expansion,
Air is collected by an air collecting cover 39 that covers the reactor water surface 38, and exhausted to an existing ventilation air conditioning exhaust duct 42 in the reactor building by a local exhaust device 41 via a transfer hose 40. A filter 43 for capturing dust and mist is incorporated in the local exhaust device 41, and contaminants are captured here. Although illustration is omitted, the filter 43 that has captured dust and mist is packed as radioactive waste in a container such as a drum and stored in a nuclear power plant.

In the present embodiment, the decontamination in the reactor pressure vessel 6, the prevention of the spread of contamination, and the reduction of the exposure dose are simultaneously performed by the clad recovery device 32 and the local exhaust device 41.

FIG. 2 shows a preventive maintenance device in a reactor vessel according to another embodiment of the present invention. This embodiment has a circulation system for injecting the reactor water 28 from the injection nozzle 24 (FIG. 3) as the injection water as described above. Circulation pump 2
7 is the same as that of the embodiment of FIG. 1 except that the furnace water 28 is supplied to the high-pressure pump 19 by the hose 29.

FIG. 3 shows a main part of the embodiment shown in FIGS. 1 and 2 which is inserted into the bottom of the reactor pressure vessel 6, and shows that the preventive maintenance device 1 is set in the CRD housing 45. .

FIG. 4 shows a construction object 4 to be subjected to preventive maintenance.
4 is an example of data showing a wraparound effect in which a cavitation bubble 30 flows downstream along a curved surface of an object having a circular or elliptical cross section. FIG. 4 shows the improvement range of the residual stress (residual stress value after construction—residual stress value before construction) radially from the center of the construction subject 44.
According to FIG. 4, the width of improvement in the residual stress is widened so as to surround the construction object 44 in one direction (the right direction in FIG. 4) from the injection nozzle 24. According to this wraparound effect, the CRD housing 45 and the CRD stub tube 4 which are a part of the construction object of the embodiment of FIGS.
6. SCC (Stress Corrosion Cracking) without scanning the injection nozzle 24 evenly over the entire circumference of the ICM housing 47
Prevention is implemented. With this implementation, the preventive maintenance device 1
Can be reduced by about half.

Table 1 shows a list of construction patterns to which the effect of the cavitation bubbles 30 being swirled is applied.

[0039]

[Table 1]

The + mark in each of the construction patterns in Table 1 indicates a CRD housing 4 in which the preventive maintenance device 1 is installed.
5 is shown. The preventive maintenance device 1 includes a CRD housing 45, a CRD stub tube 46, a CRD stub tube 46, a bottom portion of the reactor pressure vessel 6, and a CRD housing 45 in which the preventive maintenance device 1 is set as shown in No. 1 in Table 1. Each of the welds and the lower mirror overlay weld 48 are constructed. This is mainly C
This is a pattern in the case where the RD housing 45 is installed in a place where it is independently arranged.

The construction pattern of No. 2 in Table 1 indicates that the CRD housing 4 centered on the CRD housing 45 adjacent to the CRD housing 45 in which the preventive maintenance device 1 is set.
5, the CRD stub tube 46, the bottom of the reactor pressure vessel 6, and the respective welded portions and the lower mirror overlay welded portions 48 are constructed by applying the effect of the cavitation bubbles 30 to enter. Since this wrap-around effect reaches 45% of the adjacent construction object (the area shaded in Table 1), by setting the preventive maintenance device 1 at one place, 1.
It will be possible to construct 25 locations. According to this method, the construction patterns are classified into five types shown in Table 1. In Table 1, the + mark indicates the CRD housing on which the preventive maintenance device 1 is fixed, and the filled area indicates the preventive maintenance construction range. As shown in No. 6, the ICM housing 47 can be installed at 0.5 locations by setting the preventive maintenance device 1 at one location.

FIG. 5 shows a reactor pressure vessel 6 of a BWR plant as an example of an object to which the embodiment of FIGS. 1 and 2 is applied.
The bottom is viewed from above in a plan view. This example of a BWR plant has 137 CRDs and 43 ICMs.
There are books, and the construction target of the present invention is 180 places. This B
When the construction pattern shown in Table 1 is applied to the WR plant,
If the preventive maintenance device 1 is set at 88 places indicated by the + mark, the CRD housing 45 and the CRD stub tube 4 that are to be constructed
6, the ICM housing 47, the bottom of the reactor pressure vessel 6, and the entire bottom of the reactor pressure vessel 6 including the respective welded portions and the lower mirror overlay welding portion 48. In addition, the construction target of the plant as an example is 180 places, but this extends from 102 to 240 places depending on the output of each plant. If the construction patterns shown in Table 1 are applied to these plants as well, the number of locations where the preventive maintenance device 1 is set is reduced to about half, and construction efficiency is improved.

The method of fixing the preventive maintenance device 1, the driving mechanism of the injection nozzle 24, the scanning pattern of the injection nozzle 24, and the preventive maintenance method using the cavitation bubble 30 will be described with reference to FIGS.

FIG. 6 shows an example in which the injection center 49 of the injection nozzle 24 is eccentric with respect to the central axis 50 of the ICM housing 47, thereby changing the wraparound of the cavitation bubble 30 described above. According to FIG. 6, the cavitation bubble 30 is formed by eccentricity of the injection center 49.
Wraps around the back of the ICM housing 47 (to the left in FIG. 6), expanding the range leading to SCC preventive maintenance. The same effect can be obtained for the CRD stub tube 46 and the CRD housing 45, though there is a difference in the wraparound due to the difference in the outer diameter.

FIG. 7 shows a specific example of obtaining the wraparound effect by eccentricity. After performing preventive maintenance on the annular or cylindrical preventive maintenance object (ICM housing, CRD stub tube, CRD housing and their welded parts) using the injection nozzle 24, the same preventive maintenance object is injected into the injection center 49.
Is performed by replacing the injection nozzle 24 with an eccentric injection nozzle 51 eccentric with respect to the central axis 50 of the ICM housing 47. For this reason, as a means for replacing the injection nozzle, a mounting / detaching means using a screw of the injection nozzle 24 is provided at a position where the injection nozzle is attached to the arm. In FIG. 7, as in FIG. 6, the cavitation bubble 30 extends to the back side of the ICM housing 47 (to the left in FIG. 7), expanding the range leading to SCC preventive maintenance. The same effect can be obtained for the CRD stub tube 46 and the CRD housing 45, though there is a difference in wraparound due to a difference in outer diameter.

FIG. 8 shows a detailed configuration of the preventive maintenance device in the embodiment of FIGS. The preventive maintenance device 1 in FIG. 8 is a CR that constitutes the bottom of the reactor pressure vessel 6.
D stub tube 46, one of the heads of CRD housing 45 and fuel support hole 15 in core support plate 14.
It is set and fixed.

This fixing method will be described below. The tip 52 for fixing the preventive maintenance device 1 is a CRD housing 45.
It is inserted into the opening in the head. The distal end 52 is a spring-structured member whose diameter is smaller than the opening of the head of the CRD housing 45 in the free state. The pusher 53 having a taper is moved to the tip 5 by an air cylinder 54.
The structure is such that the root expands and opens and closes by entering and exiting inside 2. The preventive maintenance device 1 is fixed to the opening of the head of the CRD housing 45 by opening the tip 52. At the same time, the preventive maintenance device 1 is aligned with the CRD housing 45. The tip 52
It is mounted concentrically with the inner body 65 at a lower portion inside the inner body 65 which is a fixing structure.

The upper part of the preventive maintenance device 1 is laterally supported by the fuel support hole 15 and the core support plate 14.
By aligning the notch 56 of the preventive maintenance device 1 with the upper positioning pin 55, the position in the rotation direction is determined, and the construction start position of the injection nozzle 24 is determined.

The air cylinder 54 is fixedly installed in the upper portion of the inner body 65, and the vertical piston rod of the air cylinder 54 is connected to the pusher 53 so that the pusher 53 can move up and down. The upper part of the CRD housing 45 is inserted into the lower part of the inner trunk 65 so as to prevent the preventive maintenance device from falling down significantly. An intermediate body 61 as a revolving body is mounted around the outer periphery of the inner body 65 via a bearing 70 so as to be rotatable concentrically with the center of the inner body 65. The intermediate cylinder 61 can be driven to rotate via gears 64 and 67 by a rotation motor 66 fixed to the inner cylinder.

On the outside of the intermediate body 61, an outer body 59 is provided.
Deployed concentrically with 5. The outer cylinder 59 is attached to the intermediate cylinder 61 so as to be vertically movable by a ball screw type feeding device.
The ball screw type feeder is configured such that a rotary drive shaft of a lifting / lowering motor 62 fixed to the intermediate body 61 is connected to a vertically long screw screw shaft which is also rotatably mounted on the intermediate body 61, and is connected to the screw screw shaft. The nut 60 fixed to the body 59 is screwed, and the nut 60 is sent up and down by a screw screw shaft that is rotated by the rotation of the elevating motor 62.
9 goes up and down. Reference numeral 63 denotes a guide fixed to the intermediate body 61, and a guide fixed to the outer body 59 is slidably fitted up and down to assure that the outer body 59 can move up and down accurately without swinging. ing. Outer body 59 is intermediate body 6
The guide 63 is guided by the guide 63 attached to 1 and moves up and down smoothly and accurately.

An articulated arm is attached to the lower part of the outer trunk 59. In the articulated arm, one end of an arm 57 is rotatably mounted on an outer trunk 59, and one end of another arm 71 is connected to the other end of the arm 57 by a swing motor 6.
8 so that it can be rotated freely and attached to the arm 57
The arm 57 is connected to the outer body 59 by a cylinder 58 so that the arm 57 can swing freely by the expansion and contraction of the cylinder 58. Further, the other end of the arm 71 can be attached to any of the above-described injection nozzles. Screw that is screwed with a screw attached to each spray nozzle.

Next, the driving mechanism of the injection nozzle 24 will be described. The injection nozzle 24 moves up and down and rotates with respect to the CRD housing 45 in which the preventive maintenance device 1 is set, and the injection nozzle 24 swings so that the injection direction can be changed. When the preventive maintenance device 1 accesses the bottom of the reactor pressure vessel 6, the injection nozzle arm 57 is raised and lowered by the cylinder 58 so that the injection nozzle 24 does not interfere with other equipment in the reactor. In the configuration shown in FIG. 8, the piston of the cylinder 58 is moved up and down by the link mechanism of the injection nozzle arm 57, but this operation is performed by transmitting the rotation of the motor by a gear or the like.
7 may be raised and defeated.

The raising / lowering operation of the injection nozzle 24 is performed by moving a ball screw 60 attached to the inside of the outer case 59 of the preventive maintenance device 1 to an elevating motor 62 attached to the intermediate case 61 of the preventive maintenance device 1.
Is performed by rotating. Injection nozzle 24 CR
The rotation operation with respect to the D housing 45 is performed by the preventive maintenance device 1.
The gear 64, which is a part of the intermediate body 61, is rotated by rotating a gear 67 of a rotation motor 66 attached to the inner body 65 of the preventive maintenance device 1. The intermediate body 61 is supported in the vertical direction by a bearing 70 that receives a thrust load set on the inner body 65, and the rotation operation is smoothly performed. The swing operation of the injection nozzle 24 is performed by rotating the swing motor 68 forward and backward. The swing motor 68 is attached to the tip of the injection nozzle arm 57. The rotation axis of the swing motor 68 is fixed to an injection nozzle swing arm 71 to which the injection nozzle 24 is attached. Elevating motor 62, rotating motor 6 for driving each operation of elevating, rotating, and swinging injection nozzle 24
6. The swing motor 68 includes a detector such as a potentiometer for detecting the rotational position and speed of each motor. These detection signals are transmitted to the control cable 2
The control signal is transmitted to the control panel 11 via the control unit 1 and is used for controlling the rotation of each motor so that the scanning speed and the injection position (elevation position, rotation position, and swing angle) of the injection nozzle 24 are optimized under the preventive maintenance work.

The water pressurized by the high-pressure pump 19 is guided to the preventive maintenance device 1 through the high-pressure hose 20 and is jetted from the jet nozzle 24. At this time, cavitation bubbles 30 are generated by a pressure difference between the surrounding water (reactor water) 28 and the jet water flow, a shearing action, and the like. The impact pressure generated when the cavitation bubbles 30 collapse at and near the bottom surface of the reactor pressure vessel 6 peens the entire bottom of the reactor pressure vessel 6 to improve the residual stress to a compressive residual stress.

The shape of the joint between the CRD stub tube 46 located at the lower part of the CRD housing 45 for setting the preventive maintenance device 1 and the bottom of the reactor pressure vessel 6 is determined in advance by the control panel 11.
The address is managed within. The scanning pattern of the injection nozzle 24 is adjusted to the shape of the joint at each address being managed, and the CRD housing 45 in which the preventive maintenance device 1 is set.
On the other hand, the vertical movement is repeated at the optimum construction speed in the axial direction and the rotation operation is repeated at the optimal pitch in the circumferential direction. Further, at the lower end of the elevating operation, the injection nozzle 24 is swung to inject the cavitation bubbles 30 to the lower mirror overlay welding portion 48, thereby expanding the range of the preventive maintenance effect. CR to be applied by the above scanning pattern
SCC preventive maintenance of the D housing 45, the CRD stub tube 46, the bottom of the reactor pressure vessel 6, and the respective welds and lower mirror overlay welds 48 are performed.

FIG. 9 shows a state in which the injection nozzle 24 is directed outward by the swing of the articulated arm. Fixing method of preventive maintenance device 1, drive mechanism of injection nozzle 24, scan pattern of injection nozzle 24, and cavitation bubble 30
Is the same as that described with reference to FIG.

The spray nozzle 24 swings by rotating the swing motor 68 at an optimum spray angle for each construction site outside the CRD housing 45 for each address where the preventive maintenance device 1 is set. Furthermore, high-pressure water is injected from the injection nozzle 24 while rotating the injection nozzle 24 at an optimum elevating speed and at an optimum circumferential pitch. CRD housing 45 in which preventive maintenance device 1 is set
SCC preventive maintenance is performed on the CRD housing 45, the CRD stub tube 46, the bottom of the reactor pressure vessel 6, and the respective welded portions and the lower mirror overlay welded portions 48 around the CRD housing 45. At this time, the range of the preventive maintenance effect in each construction site is expanded due to the wraparound effect of the cavitation bubbles 30.

According to the present embodiment, the preventive maintenance device 1 provided with a driving mechanism for the injection nozzle 24 is mounted on the CRD housing 45, and the high-pressure water is injected from the injection nozzle 24 to generate the cavitation bubbles 30. The injection nozzle 24 is directed toward or outside the CRD housing 45 on which the preventive maintenance device 1 is mounted, and
The cavitation bubble 30 is rotated, raised and lowered, and the cavitation bubble 30 is transferred to the CRD stub tube 46, CRD housing 45,
The CM housing 47 and the respective welds and the lower mirror overlay weld 48 are collided with each other, and the cavitation bubbles 30 are peened by the impact pressure at the time of collapse to improve the stress state of the entire bottom of the reactor pressure vessel 6 to the compression side. The potential for stress corrosion cracking (SCC) can be reduced. Further, the decontamination inside the reactor pressure vessel 6, the prevention of the spread of contamination, and the reduction of exposure can be achieved at the same time by the clad recovery device 32 and the local exhaust device 41 in this embodiment.

Furthermore, if the construction is performed by applying the effect of the cavitation bubbles 30 wrapping around an object having a circular or elliptical cross section of the construction object 44 as in each housing, the preventive maintenance device can be mounted on the CRD housing 45. 1
The number of times of setting can be reduced, and the construction efficiency is improved.

According to the present embodiment, the cavitation bubble 30 is formed by eccentricizing the injection center 49 of the injection nozzle 24 with respect to the center axis 50 of the ICM housing 47.
It goes around to the back side of the CM housing 47, the range of SCC preventive maintenance is expanded, and construction efficiency is improved. Furthermore,
The above-described eccentricity of the injection center 49 of the injection nozzle 24 with respect to the central axis 50 of the ICM housing 47 is performed by replacing the eccentric injection nozzle 51 with an eccentric injection nozzle in advance.
It goes around to the back side of the CM housing 47, the range of SCC preventive maintenance is expanded, and construction efficiency is improved.

[0061]

According to the first aspect of the present invention, it is possible to collect gas in cavitation bubbles generated in the operation of improving the stress of the structural material in water in the reactor vessel, and to suppress radioactive contamination from the water surface to the upper space. .

According to the second aspect of the present invention, since the injection nozzle can be easily moved, the operation of improving the stresses of the plurality of preventive maintenance targets into the compressive residual stress can be easily performed.

According to the third aspect of the present invention, the cavitation bubbles are swept to the rear side along the cylindrical body, so that the preventive maintenance target area can be expanded.

According to the fourth aspect, the effect of the third aspect can be obtained by using an eccentric nozzle whose injection center is eccentric with respect to the center of the cylindrical body in the horizontal direction as the injection nozzle.

According to the fifth aspect, the maintenance area can be changed by replacing the injection nozzle.

According to the sixth aspect of the present invention, the activated cladding is prevented from freely rising from the bottom of the reactor vessel to the reactor water surface, and the radiation contamination by the cladding is expanded above the reactor water surface. Is suppressed.

According to the seventh aspect, the gas containing the contaminants collected by the air collecting cover is exhausted through the ventilation duct for air conditioning and air conditioning, and the gas floating on the water surface can be continuously collected.

According to the eighth aspect, contaminants accompanying the trapped gas can be removed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a preventive maintenance device for a reactor bottom, which is a preferred embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a preventive maintenance device for a reactor bottom according to another embodiment of the present invention.

FIG. 3 is a partially enlarged view of the preventive maintenance device in each embodiment of FIGS. 1 and 2;

FIG. 4 is a graph showing the wraparound effect of the cavitation jet of the preventive maintenance device according to each embodiment of FIGS. 1 and 2;

FIG. 5 is a plan view of the inside of the bottom of the reactor pressure vessel showing a set place of the preventive maintenance device for the inside of the bottom of the reactor pressure vessel in FIGS. 1 and 2;

FIG. 6 is a plan view showing the wraparound state of the cavitation jet when the center of the ICM housing and the injection center of the injection nozzle are eccentric in each of the embodiments of FIGS. 1 and 2;

FIG. 7 is a plan view showing the wraparound state of the cavitation jet when the eccentric injection nozzle is used to eccentric the center axis of the ICM housing and the injection center of the injection nozzle according to each embodiment of FIGS. 1 and 2;

FIG. 8 is an elevational view showing a preventive maintenance operation state of the CRD housing at the fixing position in the preventive maintenance device according to each embodiment of FIGS. 1 and 2;

9 is an elevational view showing a preventive maintenance operation state for the CRD housing around a fixing position in the preventive maintenance device in FIG. 8;

[Description of Signs] 1 ... Preventive maintenance device, 2 ... Operating floor, 3 ...
Refueling trolley, 4 ... Hoist crane, 5 ... Wire rope, 6 ... Reactor pressure vessel, 7 ... Flange, 8,9 ... Monitoring camera, 10 ... Cable, 11 ... Control panel, 12,16 ...
Monitor, 13: Upper lattice plate, 14: Core support plate, 15
... holes for fuel support brackets, 17 ... cables, 18 ... ropes,
19 high-pressure pump, 20 high-pressure hose, 21 control cable, 22 and 25 air hose, 23 control cable, 24 injection nozzle, 26 low-pressure hose, 27 circulation pump, 28 reactor water, 29 hose , 30: cavitation bubble, 31: suction port, 32: clad recovery device,
33 ... clad transfer hose, 34 ... clad transfer pump, 35, 43, 69 ... filter, 36 ... discharge hose, 37 ... spent fuel pool, 38 ... furnace water surface, 39 ... air collecting cover, 40 ... transfer hose, 41 ... Local exhaust system, 4
2: Exhaust duct for ventilation and air conditioning, 44: Object to be constructed, 45:
CRD housing, 46 ... CRD stub tube, 47
... ICM housing, 48 ... lower mirror overlay welding part, 49 ... injection center, 50 ... center axis, 51 ... eccentric ejection nozzle, 52 ...
Tip, 53 ... Pusher, 54 ... Air cylinder, 55 ...
Positioning pin, 56: Notch, 57: Arm for injection nozzle, 58: Cylinder, 59: Outer body, 60: Nut, 6
DESCRIPTION OF SYMBOLS 1 ... Intermediate cylinder, 62 ... Elevating motor, 63 ... Guide, 6
4, 67 ... gear, 65 ... inner body, 66 ... rotation motor,
68: swing motor, 71: spray nozzle swing arm.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eisaku Hayashi 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Hitachi, Ltd. Inside the Hitachi Plant (72) Koichi Kurosawa 3-1-1, Sachimachi, Hitachi-shi, Ibaraki No. 1 Hitachi, Ltd. Hitachi Plant (72) Inventor Fujio Yoshikubo 3-2-2, Sachimachi, Hitachi City, Ibaraki Prefecture Within Hitachi Nuclear Engineering Co., Ltd. (72) Inventor Hideyasu Furukawa, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi 1-1, Hitachi, Ltd., 3-chome Co., Ltd. (72) Inventor Ryo Morinaka 3-1-1, Sakaicho, Hitachi, Ibaraki Pref. Hitachi, Ltd., Hitachi, Ltd. (72) Kunio Enomoto, Tsuchiura, Ibaraki 502, Katemachi, Hitachi City Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Masahiro Otaka 502, Kantemachi, Tsuchiura-shi, Ibaraki Pref. Inside Hitachi, Ltd. Mechanical Research Laboratory (72) Inventor Noboru Chiba 2-3-1-1, Aise-cho, Hitachi City, Ibaraki Prefecture Inside Ritsukiki Co., Ltd. (72) Inventor Kazunori Sato 3-36 Takaracho, Kure City, Hiroshima Prefecture Babcock Day (58) Field surveyed (Int. Cl. ⁶ , DB name) G21D 1/00 G21C 19/02

Claims (8)

(57) [Claims] 1. A reactor for applying a compressive residual stress to said structural material by injecting a water flow accompanied by generation of cavitation bubbles from an injection nozzle toward a structural material for improving residual stress in water in a reactor vessel. In the preventive maintenance device in the vessel, when the water jet is jetted from the jet nozzle, a gas collecting cover for collecting gas rising from the water in the reactor vessel toward the water surface is provided. Preventive maintenance equipment in the reactor pressure vessel. 2. The fixing structure according to claim 1, wherein the fixing structure is detachably mounted on a cylindrical body disposed in the reactor vessel.
A revolving body mounted on the fixing structure so as to be horizontally rotatable; a multi-joint arm mounted on the revolving body so as to freely swing on a plane forming an angle with a revolving surface of the revolving body; A preventive maintenance device in a reactor vessel, comprising: 3. The preventive maintenance device in a nuclear reactor vessel according to claim 2, wherein said injection nozzle is mounted on said articulated arm such that the injection center of said injection nozzle is eccentric with respect to the center of said cylindrical body. 4. The preventive maintenance device in a nuclear reactor vessel according to claim 3, wherein the injection nozzle is an eccentric nozzle whose injection center is eccentric in the horizontal direction with respect to the center of the cylindrical body. 5. The reactor pressure vessel according to claim 2, wherein said articulated arm is provided with means for replacing an injection nozzle whose injection center is eccentric with respect to the center of said cylindrical body and an injection nozzle which is not eccentric. Preventive maintenance device. 6. The preventive maintenance device in a reactor vessel according to claim 2, further comprising means for sucking the underwater clad. 7. The preventive maintenance device in a reactor vessel according to claim 1, further comprising an exhaust duct for ventilation and air conditioning communicating with the air collecting cover. 8. The preventive maintenance device in a reactor pressure vessel according to claim 7, wherein said exhaust duct for ventilation and air conditioning communicates with said air collecting cover through a filter for capturing contaminants.