JPH0766079B2 - Reactor internal structure dismantling system by plasma arc cutting technology - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a system for disassembling internal structures of a nuclear reactor by using a plasma arc cutting technique.

(Prior Art) A nuclear power plant will reach the end of its life after long-term use, and it will be necessary to dismantle the reactor internals together with other equipment.
There are several techniques for dismantling, but the plasma arc cutting technique is one of them.

The plasma arc cutting technology has been used as a technology for cutting stainless steel and non-ferrous metals, which are the main constituent materials of the reactor internals, but for the dismantling of activated nuclear reactor internals. Since this was not a technology, systemization such as reduction of radiation exposure from reactor internals and collection of gas and activated cutting powder generated during cutting was not considered.

(Problems to be solved by the invention) Since the reactor internals are activated or radioactively contaminated, the reactor internals to be dismantled underwater to reduce the radiation exposure of workers when disassembling work is underway. Moreover, dismantling work is required remotely. In addition, when performing underwater cutting with the plasma arc cutting technology, as the gas supplied for cutting and the gas such as hydrogen generated by water decomposition rise to the water surface, part of the cutting powder of the reactor internals It becomes a floating substance in the air. Further, a part of the cutting powder remains in the water and becomes a suspended matter in the water, and a part of the cutting powder becomes dross and falls to the bottom of the reactor pressure vessel. It is necessary to take measures against by-products accompanying these cuttings. Therefore, when disassembling the reactor internals using the plasma arc cutting technique, a system that solves the problems including the recovery of these cutting byproducts is required.

When considering a system for disassembling the internal structure of a nuclear reactor, how should each device be installed in order to efficiently arrange the equipment that has the necessary functions in the limited space of the nuclear reactor facility and increase the overall efficiency? It is important to adopt such a method.

For example, in a cutting drive device that holds a torch and cuts the internal furnace structure, the cutting position moves downward as the cutting target moves from the upper part to the lower internal structure. In this case, if the device has a short torch movement stroke, it covers the short stroke.Therefore, in the case of the method of lowering the cutting drive device with a crane or the like to set the torch at the cutting position, the cutting drive device and the furnace should be moved every time it moves. The relative position of the structure changes and it is difficult to confirm the relative position of the two after the movement. Therefore, it becomes difficult to perform the cutting operation of moving the torch along the in-core structure. And the object to be cut, the field of view is narrowed by the cutting drive device for the worker to observe the cutting position, etc. It cannot be taken out from the furnace pressure vessel, and the work of pulling up and moving the cutting drive device once is involved.

(Means for Solving the Problem) The present invention provides a system for safely and efficiently disassembling the internal structure of a nuclear reactor by using a plasma arc cutting technique.

The reactor internal structure dismantling system by the plasma arc cutting technology according to the present invention is a system in which a torch is installed at the upper part of the reactor pressure vessel and is capable of turning and ascending and descending at the lower end of an elevating shaft capable of ascending and descending. The attached cutting drive device, the generated gas recovery processing device that collects the generated gas containing the radioactive air suspended matter generated when cutting the activated reactor internals, the radioactive falling dross and the suspended solids in water. It comprises a water purifying device for recovery processing and a cut object holding / fixing / conveying device for holding and fixing the in-reactor internal structure at the time of cutting and for conveying the separated in-reactor internal structure after cutting. It also has a surveillance camera that monitors the work such as dismantling the reactor internals using these.

Therefore, the system shown in FIGS. 1 to 6 is required.

The cutting drive device 3 is installed at the same level as the working floor having an opening wider than the pressure vessel 1, and has a long lifting shaft 21. When the cut piece is taken out, the lifting shaft 21 is divided and lifted up to a well portion 87. Move to the position where the cutting piece can be taken out without moving the entire cutting device, and work efficiency will be improved.

By-products generated at the time of cutting are collected as much as possible at the place where they are generated, and a method is adopted to prevent the spread of radioactive contamination to the existing system.

The generated gas recovery processing device 4 for recovering airborne solid matter and hydrogen gas generated at the time of cutting is installed in the opening of the upper part of the reactor, and its inner diameter is larger than the outer diameter of the reactor pressure vessel. It is arranged so as not to interfere with the cutting operation of the driving device 3 and the carrying out of the separated furnace internal structure 2. In addition, this device adopts an air curtain system that has an air supply system and a system that exhausts air through a filter to prevent radioactive airborne solids from diffusing above the air curtain as much as possible, and We are trying to reduce.

Regarding the water purification device that collects suspended solids and falling dross generated during cutting, equipment such as pumps, strainers, filters that incorporate components, and hoses that collect suspended solids and falling dross when collecting water are
The strainer and filter installed or temporarily placed in the well part so as not to interfere with the cutting operation of the cutting drive device and filled with underwater floating materials, etc. can be replaced remotely in consideration of reducing the exposure of workers. It is adopted.

Regarding the cut object holding / fixing / conveying device 7 having a holding and fixing function and a take-out function for preventing the fall of the separated in-core structure at the end of cutting, when the device is set to the in-core structure 2, It is set so that the internal reactor structure 2 is placed inside and the cut object holding / fixing / conveying device 7 is placed outside the internal reactor structure 2 to avoid cutting between the narrow reactor pressure vessel 1 and the internal reactor structure 2. The method that can perform the cutting operation from the inside of the furnace internal structure 2 is adopted.

(Effect of the invention) The present invention reduces the exposure of workers by cutting and dismantling the internal structure of a reactor having a high radiation dose rate in water, and has the function of recovering the generated radioactive byproduct at the dismantling site. Since it has, it prevents the spread of radioactive contamination to the existing treatment system and can carry out the cut products without moving the cutting drive device installed in the upper part of the reactor, and the internal structure installed in the lower part of the reactor pressure vessel. It is effective for safely dismantling the reactor internals with a device that takes into consideration the efficiency of dismantling work, such as replacing the torch that has been extended for a long time when cutting, and replacing the damaged torch without pulling it up. System.

(Example) Next, an example of the present invention will be described.

FIG. 1 is an overall view of a system for disassembling a reactor internal structure by a plasma arc cutting technique, in which the reactor internal structure 2 installed in a reactor pressure vessel 1 is cut by a cutting drive device 3. However, the gas and airborne substances generated during cutting are
The generated gas recovery processing device 4 collects the suspended solids and the dross in water. The cutting piece 6 is held and fixed by the cutting piece holding and fixing conveying device 7 during cutting, and is carried out by the crane 8 together with the holding and fixing conveying device 7 after cutting. A cover 9 is provided on the upper part of the reactor pressure vessel 1 to prevent diffusion of generated gas and airborne substances that cannot be recovered by the generated gas recovery processing device 4.

FIG. 2 is a diagram showing the cutting drive device 3, in which a traveling drive device 10 for driving a horizontal surface (travel drive mechanism) is shown.
11 and a traveling guide rail 12), a traverse driving device 13 (consisting of a traverse driving mechanism 14 and a traverse guide rail 15) that drives the traveling guide rail 12 orthogonally to the traveling drive device 10, and a traverse driving device. Swing drive 16 on top of 13
(Consisting of a swivel drive mechanism 17 and a swivel table 18) and swivels the swivel table 18 together with the lifting drive device 19 (comprising a lifting drive mechanism 20, a lifting shaft 21, and a lifting guide rail 22). The lifting drive mechanism 20 moves the lifting shaft 21 up and down, and the torch 23 is attached to the tip 26 of the lifting shaft.
The furnace internal structure 2 is cut by 23. Regarding each drive mechanism, the traveling drive mechanism 11 and the traverse drive mechanism 14 are driven by the ball screw 24 and the ball nut 25, and the swing drive mechanism 17 is used.
Is a pinion gear drive, and the lift drive mechanism 20 is a pinion rack drive, each driven by a motor. Each drive unit adopts a numerical control method and can arbitrarily control the speed and position, and a cutting path and a speed for cutting the in-core structure 2 can be arbitrarily selected by a combination of controlling drive units. The elevating shaft 21 is a split-and-joint system according to the patent application already submitted. The lifting shaft tip 26 to which the torch 23 is attached can be removed remotely from the work floor and pulled up to replace the torch 23.

FIG. 3 is a view showing a mechanism for remotely removing the lifting shaft tip end portion 26 to which the torch 23 is attached from the work floor. The lifting shaft tip end portion 26 removing mechanism 27 is entirely suspended by a wire 28. The hoisting and lowering shaft 21 is used as a guide to wind up and down by a hand winding winch 29 installed above the cutting drive device.

After the entire lifting mechanism 27 for lifting the lifting shaft is wound down to the specified position, the pole 30 is set to the pin 31 and rotated to rotate the rod 32.
The claw 34 swivels in the direction of the arrow 33 around the center, and the claw 34 is set on the tip end portion 26 of the elevating shaft. Further, set the pole 30 to the pin 35 and rotate the pole 30 to make the arrow center around the pin 35.
The claw tip portion 37 turns in the direction of 36 and grips the lifting shaft tip portion 26.
When air is supplied to the air 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. The block 41 has four pins 42, and the pin 42 also rises together with the block 41. The pin 42 is inserted into the long hole of the claw 43, and the claw 43 is rotated in the direction of the arrow 45 by using the pin 44 as a branch by the ascent of the pin 42, and the claw 43 is disengaged from the elevating tip 26. When the claw 43 comes off the lifting shaft tip 26, the block 41
Is operated away from the limit switch, and a lamp indicates that the pawl 43 has come off the lifting shaft tip 26. After that, the pole 30 is set on the pin 31, and the pole is turned in the opposite direction of the arrow 33 to shift the lifting shaft tip 26 gripped by the claw 34 and the claw tip 37 around the rod 32 from the center of the lifting shaft 21 to move the lifting shaft tip. The lifting shaft tip end removing mechanism 27 is wound up together with the portion 26 by a hand winding winch 29.

FIG. 4 is a diagram showing the generated gas recovery processing device 4,
It is composed of a blower system 49 (consisting of a blower 50, a blower duct 51 and a blower duct outlet 52) and an exhaust system 53 (consisting of an exhaust duct inlet 54, an exhaust duct 55, a filter 56 and a blower 57). The air sent by the blower 50 is blown by the blower duct.
It is blown out from the ventilation duct outlet 52 through 51. The blown air is sucked by the exhaust fan 57 together with the generated gas, suspended solids and ambient air from the exhaust duct inlet 54 to dilute the generated gas, and the flow of these gases causes the gas to flow into the opening in the upper part of the reactor. An air curtain is formed to reduce the dispersion of airborne substances on the work floor. Further, the air and the generated gas and air suspended matter sucked from the exhaust air duct inlet 54 pass through the air exhaust duct 55 and are collected by the filter 56, and then the air blower 57 is used to install the existing exhaust system of the reactor facility. Sucked to 60.

FIG. 5 is a view showing the water purifying device 5, in which suspended solids in water or falling dross are sucked together with water by the large-diameter suction head 62 or the small-diameter suction head 63 by the pump 61, and the strainer casing. Inflow to 64. After large particles such as falling dross have been passed through the strainer 65,
Pump outlet pipe 68 from pump 61 through passage 67 in base 66
And then flows into the filter 70 from the filter inlet 69. The water that has been purified by the filter 70 containing small particles such as suspended solids in water flows out from the filter outlet 71.
The strainer 65, which has been filled with falling dross, opens the lid 71 of the strainer casing 64 with a hook or the like and is a strainer hanger.
Use 72 to hang a wire, and lift it with the crane 8 in Fig. 1 to replace it. The clogged filter 70 swivels the filter casing 74 with the pole set on the filter casing swiveling pin 73. When the filter casing pin 75 and the filter fixing plate cutout 76 are aligned with each other, the filter casing 77 is used to hang wires to suspend the filter casing 74 for replacement.

FIG. 6 is a view showing the cut object holding / fixing / conveying device 7, in which the wire 79 is hung on the lifting tool 78 of the cut object holding / fixing / conveying device 7 to move the internal structure 2 to the inside by the crane 8 of FIG. Then, the cut object holding / fixing / conveying device 7 is lowered. After that, eight legs 80 driven by water pressure are pressed against the reactor pressure vessel 1 to fix the cut object holding and fixing transfer device 7, and then a drill 81 rotating by a water flow is pressed by a piston 82 in a direction of an arrow 83, and a reactor internal structure The in-furnace internal structure 2 and the cut object holding / fixing and conveying device 7 are fixed by penetrating the object 2. After fixing the in-furnace internal structure 2 and the cut object holding / fixing / conveying device 7, the wire 79 is removed and the in-furnace internal structure 2 is cut by the cutting drive device 3 in FIG. After cutting, the wire 79 is hung from the suspending device 78 and then the eight legs 80 are retracted, and the cut object holding / fixing / conveying device 7 is removed from the reactor pressure vessel 1 and the cut object holding / fixing / conveying is carried out together with the separated reactor internal structure 2. Lift the device 7. Inner structure 2 separated after lifting
The cut object holding / fixing / conveying device 7 has an underwater passage 84 in FIG.
After passing through the hole and placing it in the pool 85 in FIG. 1, remove the drill 81 to remove the cut object holding and fixing conveying device 7 from the cutting piece and pull it up, and hold, fix and convey when cutting the next furnace internal structure. To reuse.

The reactor internal structure dismantling apparatus by the plasma arc cutting technology of the present invention is a cutting at the water depth necessary for reducing the exposure of the worker in disassembling the nuclear reactor internal structure having a high radiation dose rate as described above. It is an effective device for dismantling the internal structure of a nuclear reactor with the functions required for dismantling, the functions necessary for preventing the spread of radioactive contamination and the work efficiency.

[Brief description of drawings]

FIG. 1 is an overall view of a system for disassembling internal structures of a nuclear reactor by a plasma arc cutting technique. 2A and 2B are an overall view and a partial detailed view of the cutting drive device 3. 3 (a), (b) and (c) are a detaching mechanism diagram of the lifting shaft tip and a partial detailed view thereof. 4 (a) and 4 (b) are a plan view and a side view of the entire airborne material recovery apparatus of the generated gas recovery processing apparatus 4. FIG. 5 (a), (b), (c) and (d) are an overall view of the water purification device 5 and a partial detailed view thereof. 6 (a) and 6 (b) are an overall view and a partial cross-sectional view of the cut object holding / fixing / conveying device. 1 ... Pressure vessel, 2 ... Reactor internal structure 3 ... Cutting drive device 4 ... Generated gas recovery processing device 5 ... Water purification device, 6 ... Cutting piece 7 ... Cutting object holding and fixing conveying device 8 ... … Crane, 9 …… Cover

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-44898 (JP, A) JP-A-63-14000 (JP, A) JP-A 64-51000 (JP, A) JP-A-56- 48600 (JP, A)

Claims (1)

[Claims] 1. An apparatus for producing an arc between an electrode and an object, supplying a gas around the arc, and melting and cutting the object with the gas turned into plasma by arc heat, comprising: (a) a reactor pressure vessel A cutting drive device in which a lifting and lowering shaft capable of turning and lifting is attached to a traveling and traversing device installed at the upper part, and a plasma arc torch is attached to the tip of the device. (B) Holds and fixes a furnace internal structure to be cut And (c) a blower, which is composed of a blower, a blower duct, and a blower duct outlet, which faces the blower system including a blower, a blower duct, a blower duct, a filter, and a blower. A system for collecting suspended solids, which is installed in the lower part of the cutting drive device, for collecting suspended solids generated during cutting, and (d) Water for collecting suspended solids in water. A fusion cutting device provided with a purifying device and (e) a monitoring camera for confirming cutting and dismantling work.