JPH0318797A - System for disassembling internal structure of nuclear reactor by plasma arc cutting technique - Google Patents

Abstract

PURPOSE:To improve the function and the efficiency of operations necessary for preventing the expansion of radioactivity contamination by mounting a swivelable and liftable lifting shaft to travelable and traversable devices installed in the upper part of a reactor pressure vessel. CONSTITUTION:A driving device for cutting has a traveling driving device 10, a traversing driving device 13 and a swiveling driving device 16. The entire part is swiveled together with a swiveling table 18. A lifting driving mechanism 20 lifts the lifting shaft 21 and is mounted with a torch 23 in a front end part 26 of the lifting shaft. The in-pile structure 2 is cut by the torch 23. The driving mechanisms consist of the traveling driving mechanism 11 and traversing driving mechanism 14 which are driven by means of ball screws 24, ball nuts 25 and the swiveling driving mechanism 17 which is driven by a pinion and gear. All these mechanisms are driven respectively by motors. The respective driving devices can be controlled in speeds and positions as desired. The cutting route and speed are arbitrarily selected by the combinations thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a system for dismantling nuclear reactor internals using plasma arc cutting technology. (Prior art) After long-term use, a nuclear power plant reaches the end of its service life and the I! l! Structures will also need to be dismantled along with other equipment. There are several dismantling technologies, one of which is plasma arc cutting technology. Plasma arc cutting technology has traditionally been used to cut stainless steel and nonferrous metals, which are the main structural materials of nuclear reactor internals, but it is also used for dismantling nuclear reactor internals that have been exposed to radiation. Because it was not a technology for the inside of the nuclear reactor! ! Systematization such as reducing radiation exposure from structures and collecting scraps and radioactive cutting powder generated during cutting is not considered. (Problem to be solved by the invention) Since the internal reactor structures are activated or radioactively contaminated, when demolition work is proceeding, it is necessary to dismantle the reactor internal structures to reduce radiation exposure of workers. It is necessary to disassemble objects underwater and remotely. In addition, when underwater cutting is performed using plasma arc cutting technology, some of the cutting powder from the reactor internals rises to the water surface as the scraps supplied for cutting and hydrogen and other gases generated by water decomposition rise to the water surface. It becomes empty and becomes airborne. In addition, some of the cutting powder remains in the water and becomes suspended matter, and some of it becomes dross and falls to the bottom of the reactor pressure vessel. It is necessary to take measures against by-products caused by these cuttings. Therefore, when dismantling reactor internal debris using plasma arc cutting technology, a system is required that solves the problems including recovery of these cutting by-products.

When considering a system for dismantling reactor internal structures, what should be done to each device in order to efficiently arrange each device with the necessary functions in the limited space of a nuclear reactor facility and to increase overall efficiency? It is important to decide which method to use. For example, in a cutting drive device that holds a torch and cuts a furnace internal structure, the cutting position moves downward as the object to be cut moves from the upper part to the lower part of the furnace internal structure. In this case, if the torch has a short movement stroke, in order to cover the short stroke, if the entire cutting drive device is lowered using a crane or the like and the torch is set at the cutting position, The relative positions of the reactor internals have changed, making it difficult to confirm the relative positions of both after they have been moved. Therefore, it is difficult to perform the cutting operation by moving the torch along the reactor internals. ■The entire cutting drive device. is between the worker and the object to be cut, and when the worker observes the cutting position, the field of view becomes narrow due to the cutting drive device.■ The separated W4 structure inside the furnace avoids the cutting drive device. do,
It cannot be removed from the reactor pressure vessel and requires the work of pulling up and moving the cutting drive device once. (Means for Solving the Problems) The present invention provides a system for safely and efficiently dismantling nuclear reactor internals using plasma arc cutting technology. The system for dismantling structures inside a nuclear reactor using plasma arc cutting technology according to the present invention has a torch attached to the lower end of an elevator shaft that can be rotated and raised/lowered at the top of a device that is installed at the top of a reactor pressure vessel and capable of running and traversing. Installed cutting drive equipment, generated gas collection and processing equipment that collects waste containing radioactive airborne substances generated when cutting activated reactor internals, radioactive fallen dross and suspended solids in water. It consists of a water purification device that collects and processes objects, and a cut object holding, fixing and conveying device that holds and fixes the furnace internal structure during cutting and transports the separated furnace internal structure after cutting. We also have surveillance cameras that use these to monitor work such as dismantling reactor internal structures. Therefore, a system like the one shown in Figures 1 to 6 is required. The cutting drive device 3 is installed at the same level as the work floor, which has an opening wider than the inside of the pressure vessel 1, and has a long lifting shaft 21, so that when taking out the cut piece, the lifting shaft 21 is raised in parts and raised to the well part 87. The cut piece can be retrieved without moving the entire cutting device.
Improve work efficiency and smoothness. By-products generated during cutting are collected as much as possible at the site of occurrence to prevent the spread of radioactive contamination to existing systems. The generated gas recovery and processing device 4, which recovers airborne solids and hydrogen gas generated during cutting, is installed in the opening at the top of the reactor, and its inner diameter is larger than the outer diameter of the reactor pressure vessel. This is done so that it does not interfere with the cutting operation of the drive device 3 and the removal of the separated reactor internals 2. In addition, this device uses an air curtain system that has an air supply system and an exhaust system that passes through a filter to prevent radioactive airborne solids from dispersing above the air curtain as much as possible, and to remove contaminated equipment. We are trying to reduce it. Regarding water purification equipment that collects floating solids and falling dross generated during cutting, equipment that incorporates a Kozue*AA pump, strainer, and filter, as well as hoses used to collect floating solids and falling dross, etc. teeth,
The strainer and filter, which are installed or temporarily placed in the well so as not to interfere with the cutting operation of the cutting drive device, are filled with floating objects in the water, and can be replaced remotely in order to reduce the exposure of workers. We are hiring. Regarding the cut object holding, fixing and conveying device 7, which has the function of holding and fixing the cut object to prevent the detached furnace oval scoop from falling at the end of cutting, and the function of taking it out, when setting the device to the furnace internal structure 2, The reactor internals 2 are placed inside and the cut object holding/transfer device 7 is placed outside the reactor internals 2, avoiding the narrow space between the reactor pressure vessel 1 and the reactor inner tank 3a. A method is adopted in which the cutting operation can be performed from the internal measurement of the reactor internal structure 3a object 2 to be cut.

(Effects of the invention) The present invention reduces the radiation exposure of workers by cutting and dismantling reactor internal structures with high radiation dose rates underwater, and collects generated radioactive by-products at the dismantling site. This function prevents the spread of radioactive contamination to the existing treatment system, allows cut materials to be carried out without moving the cutting drive device installed at the top of the reactor, and allows for the removal of cut materials from the inside of the reactor, which is installed at the bottom of the reactor pressure vessel. The internal structures of a nuclear reactor can be safely dismantled using equipment designed to improve the efficiency of dismantling work, such as replacing a damaged torch without having to separate and pull up a long, extended lifting shaft when cutting tree trunks. It is an effective system.

(Example) Next, an example of the present invention will be described. FIG. 1 is an overall diagram of a system for dismantling reactor internals using plasma arc cutting technology, in which reactor internals 2 installed in a reactor pressure vessel 1 are cut by a cutting drive device 3. death,
The scum and airborne substances generated during cutting are collected by the generated gas recovery and processing device 4, and the floating substances and dross in the water are collected by the water purification device 5. The cut pieces 6 are held and fixed during cutting by a cut piece holding, fixing and conveying device 7, and after cutting are carried out together with the holding, fixing and conveying device 7 by a crane 8.

Note that there is a cover on the top of the reactor pressure vessel 1.
This prevents the dispersion of generated scum and airborne substances that cannot be recovered by the generated scum collection processing device 4.

FIG. 2 is a diagram showing the cutting drive device 3, which includes a traveling drive device 10 (consisting of a traveling drive device ff111 and a traveling guide rail 12) for driving a horizontal surface, and an upper part of the traveling guide rail 12. A traverse drive device 13 (consisting of a traverse drive mechanism 14 and a traverse guide rail 15) that drives orthogonally to the travel drive device 10, and a traverse drive device 'It 1
There is a turning drive device 16 (consisting of a turning drive mechanism 17 and a turning table 18) on the upper part of 3.
(consisting of the lifting shaft 21 and the lifting guide rail 22). The elevating drive a ellipse 20 moves up and down the elevating shaft 21,
A torch 23 is attached to the tip 26 of the lifting shaft, and the furnace internal structure 2 is cut with the torch 23. Regarding each drive mechanism, the traveling drive tll mechanism 11 and the traverse drive mechanism 14 are driven by a pole screw 24 and a ball nut 25, the swing drive R mechanism 17 is driven by a pinion gear, and the elevating drive mechanism elliptical 20 is driven by a pinion. - Rack driven, each driven by a motor. The speed and position of each drive device can be arbitrarily controlled using a numerical control method, and the cutting path and speed for cutting the reactor internals 2 can be arbitrarily selected by combining the drive devices to be controlled. The elevating shaft 21 is of the split and join type according to a patent application that has already been submitted. Note that the lifting shaft tip 26 to which the torch 23 is attached can be remotely removed from the work floor and pulled up to replace the torch 23. Figure 3 shows the lifting shaft tip 2 to which the torch 23 is attached.
6 is a diagram showing a mechanism for remotely removing 6 from the work floor,
The entire removal mechanism 27 of the lifting shaft tip 26 is connected to the wire 2
8, and is hoisted up and lowered by a manual winch 29 installed above the cutting drive device using the lifting shaft 21 as a guide.

After lowering the entire elevating shaft tip removal mechanism 27 to a predetermined position, the ball 30 is set on the pin 31 and rotated, and the claw 34 pivots in the direction of the arrow 33 about the rod 32.
The pawl 34 is set on the tip end 26 of the lifting shaft. Furthermore, when the pole 30 is set in the bottle 35 and the ball 30 is rotated, the claw tip 37 rotates in the direction of the arrow 36 around the pin 35 and grips the lifting shaft tip 26. Air Jirinda-38
When air is supplied to the cylinder 38, the piston 39 in the air cylinder 38, the rod 40 connected to the piston 39, and the block 41 connected to the rod 40 rise. There are four pins 42 in block 41, which rise from bottle 42 to block 41 and tora. A pin 42 is inserted into a long hole in a claw 43, and as the bottle 42 rises, the claw 43 rotates in the direction of an arrow 45 with the pin 44 as a fulcrum.
comes off from the lifting tip 26. Claw 43 or lifting shaft tip 2
6, the block 41 moves away from the limit switch and operates, and a lamp indicates that the claw 43 has come off the tip 26 of the lifting shaft. After that, set the ball 30 in the bottle 31, turn the ball in the opposite direction of the arrow 33, center the lifting shaft 32, and slide the lifting shaft tip 26, which is gripped by the claw 34 and the claw tip 37, from the center of the lifting shaft 21. Tip part 2
6 and hoist up the lifting shaft tip part removal tl1 structure 27 with the manual winding winch 29. FIG. 4 is a diagram showing the generated gas recovery processing device 4,
The exhaust system 49 (consisting of a blower B&50, a blower duct 51, and a blower duct outlet 52) and an exhaust system 53 (consisting of an exhaust duct 54, an exhaust duct 55, a filter 56, and an exhaust fan 57) are used to control air flow. The air sent by the blower 50 passes through the blower duct 51 and reaches the blower tact outlet 52.
It is blown out from. The blown air is sucked by the exhaust fan 57 from the exhaust duct 54 along with the generated gas, airborne substances, and surrounding air, and the generated gas is thoroughly removed, and the flow of these gases blows the opening at the top of the reactor. form an air curtain to reduce the spread of airborne particles onto the work floor, etc. In addition, the air, generated gas, and airborne substances sucked from the exhaust duct 54 are removed from the exhaust duct 55.
After passing through the filter 56 and collecting the airborne particles, they are sucked into the existing exhaust system 60 of the reactor facility by the exhaust fan 57. FIG. 5 is a diagram showing the water purification device 5, in which suspended solids in water or fallen dross are sucked together with water by a pump 61 through a large-diameter suction head 62 or a small-diameter suction head 63, and a strainer It flows into Thing 64. After large particles such as fallen dross are passed through the strainer 65, they pass through the passage #167 in the base 66 and are transferred to the pump 6l.
It flows from the filter port 69 into the filter 70 via the pump outlet pipe 68. The filter 70 filters out small particles such as suspended solids in the water, and the purified water flows out from the filter outlet 71. The strainer 65 filled with falling dross is 71 of the strainer gating 64.
Open it with a hook, hang a wire using a strainer and hanging tool 72, and lift it up with crane 8 in Figure 1 to replace it. In order to remove the clogged filter 70, a filter gauging 74 having a ball set on a filter gauging rotation pin 73 is rotated. At the point where the filter gating pin 75 and the filter fixing plate notch 76 are aligned, hang a wire using the filter hanging tool 77 to lift the filter gating 74 and replace it. FIG. 6 is a diagram showing the cut object holding and conveying device 7, in which a wire 79 is attached to a hanging tool 78 of the cut object holding and conveying device 7.
The cut object holding and transporting device 7 is lowered by the crane 8 shown in Fig. 1 with the furnace internals 2 facing inside. After that, eight legs 80 driven by water pressure are pressed against the reactor pressure vessel 1 to fix the cut object holding, fixing and conveying device 7, and then a drill 81 which is rotated by a water stream is pushed in the direction of an arrow 83 with a piston 82 to form the reactor internal structure. The furnace internal structure 2 and the cut object holding/transfer device 7 are fixed by penetrating the object 2. After fixing the furnace internal structure 2 and the cutting object holding and conveying device 7, the wire 79 is removed and the furnace internal structure 2 is cut by the cutting drive device 3 shown in FIG.
After cutting, the wire 79 is hung on the hanging tool 78, and the eight legs 80 are retracted to remove the cut object holding and conveying device 7 from the reactor pressure vessel 1, and the cut object is held together with the separated reactor W4 wire 12. Lift the fixed conveyance device 7. After lifting,
Separated reactor internal structure 2 and cut object holding and conveying device 7
is the underwater passage in Figure 1! ? After passing through t8 4 and placing it in the boule 85 in Fig. 1, the drill 81 is pulled out, and the cut object holding and transporting device 7 is removed from the cut object and pulled up to hold it and fix it when cutting the next elliptical object in the furnace.・Reuse for transportation.

As described above, the nuclear reactor internal structure dismantling equipment using the plasma arc cutting technology of the present invention can cut at the water depth necessary to reduce radiation exposure of workers when dismantling nuclear reactor internal structures with high radiation dose rates. It is an effective device for dismantling nuclear reactor internal structures, as it has the functions necessary for dismantling, as well as the functions necessary to prevent the spread of radioactive contamination, and is designed to improve work efficiency.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a system for dismantling ellipsoids in a nuclear reactor using plasma arc cutting technology. FIGS. 2(a) and 2(b) are an overall view of the cut UI drive device 3 and a detailed view of a portion thereof. Figure 3 (81, (b) and (C) is a diagram of the mechanism for storing and removing the tip of the lifting shaft and its partial details. Figure 4 (a)
and (b) are a plan view and a side view of the entire airborne matter recovery device of the generated gas recovery and processing device 4. Figure 5 (a), (b). (c) and (d) are an overall view of the water purification device 5 and a partial detailed view thereof. FIGS. 6(a) and 6(b) are an overall view and a partial sectional view of the cut object holding, fixing and conveying device. 1... Pressure vessel 2... Reactor internal structure 3...
Cutting drive device 4... Generated gas recovery processing device 5... Water purification device 6... Cut piece 7... Cut object holding and transporting device

Claims (1)

[Claims] Cutting and dismantling the internal reactor structures using technology that generates an arc between the electrode and the object, supplies gas around the arc, and melts and cuts the object with the gas that becomes plasma due to the arc heat. In the equipment, a cutting drive device has a lifting shaft that can rotate and move up and down attached to a device that can travel and traverse installed on the top of the reactor pressure vessel, and a plasma arc torch is attached to the tip of the shaft, and the reactor internal structure to be cut. A holding, fixing and transporting device for holding, fixing and transporting materials, an airborne material collection device for collecting airborne materials generated during cutting, a water purification device for collecting floating materials in water, and a system for checking cutting and dismantling work. A nuclear reactor internal structure dismantling system using plasma arc cutting technology characterized by consisting of a surveillance camera.