JPS6156479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nozzle dismantling device for a fuel assembly used in a nuclear reactor, which disassembles a nozzle of the fuel assembly in order to remove, for example, a damaged fuel rod from the fuel assembly.

Fuel assemblies are used in pressurized water reactors currently in use. As shown in Fig. 1, this fuel assembly consists of an upper nozzle 1 and a lower nozzle 2 arranged vertically apart, and a lattice formed by straps arranged at a predetermined interval between them. A plurality of support grids 3 having spaces are inserted into the grid spaces of the support grids 3 at predetermined intervals, and are fixed by the fixing portions of the support grids 3, and the upper and lower ends of each are connected to upper nozzles 1,
It has a control rod guide tube 4 connected to the lower nozzle 2, a large number of fuel pellets 6 sealed in a cladding tube 5, and a pressing spring 7, and is inserted into a predetermined position in the grid space of the support grid 3 to be supported. It is composed of a large number of fuel rods 8 that are elastically supported by the support portions of the lattice 3. Such fuel assemblies are removed from the reactor core after burning for a certain period of time, and after undergoing various inspections, only those that are found to be in good condition are reloaded into the reactor core.

However, conventionally, among the fuel assemblies, in the fuel assemblies in which damaged fuel rods were detected in the various inspections, even though the number of damaged fuel rods was 1 to 2 per fuel assembly, Regardless, if even one fuel rod is damaged, the reactor core cannot be reloaded for use, and the fuel assembly must be stored in a spent fuel tank, which is extremely uneconomical.

Therefore, it was considered to pull out the damaged fuel rod from the fuel assembly, but in this case, since the fuel assembly containing the damaged fuel rod has radiation, it should be located 3 m or less from the water surface in order to shield this radiation. There must be.

In addition, the upper end of each control rod guide tube is welded all around to the upper nozzle, so it is impossible to remove the nozzle from the fuel assembly and pull out the damaged fuel rod to make the fuel assembly reusable. It was something I should have done. That is, the entire circumference weld of each control rod guide tube is welded, the upper nozzle is removed from the fuel assembly, the damaged fuel rod is pulled out, a dummy rod is inserted in its place, and each control rod guide tube is welded again. The upper nozzle must be welded to the upper end underwater, and the control rod guide tube cannot be removed from the weld with the upper nozzle without cutting, and the control rod guide tube must be welded to the upper nozzle underwater. It was impossible to do this because this welding had to be carried out by operation on a water tank.

This invention was made in view of the above circumstances,
Using a hanging tool that is slidably and removably attached to a guide pin of a positioning plate that has a clamping plate and a clamping claw, the clamping claw is rotated, and the upper part of the fuel assembly is fixed in the water of the water tank. The positioning plate is attached to the lower nozzle located at the top of the water tank, and the housing axis, which is vertically attached to an XY table movably provided at the top of the water tank, is moved up and down to fit into the guide hole, and the housing is fitted into the guide hole. By rotating and moving up and down the drive shaft, which is installed inside the shaft and has a tool attached to its lower end, the lower nozzle can be removed from the fuel assembly by cutting the attachment part of each control rod guide tube to the lower nozzle. As a result, spent fuel assemblies can be transported for reprocessing, and for unburned fuel assemblies, damaged fuel rods are pulled out, dummy rods are inserted to replace them, and other types of fuel assemblies are removed. An object of the present invention is to provide a nozzle dismantling device for a fuel assembly, which can make the fuel assembly reusable by attaching a lower nozzle thereto, and can significantly reduce costs.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 17.
This will be explained based on the diagram. 11 in Figure 2 is the wall 12,
This is a fuel transfer canal (water tank) provided between the fuel transfer canal 11 and an upper fixing plate 13 attached to the walls 12, 12 at a predetermined location above the fuel transfer canal 11. Guide frames 14 and 15 are provided in a hanging manner on the upper fixing plate 13, and lower fixing plates 1 are provided below the guide frames 14 and 15.
6 and 17 are attached. Lower fixing plate 1
6 and 17 are connected to the walls 12 and 12 via the overhanging member 18.
is fixed. Can support frames 19 and 20 are provided between the guide frames 14 and 15 to face each other. can support frame 1
A sheave 23 is attached to the upper part of the can support frames 19 and 20, respectively.
0 is suspended vertically movably via an electric winch 22 attached to the upper fixed plate 13, a wire rope 24, and sheaves 21, 23, and is supported by a holding member 25 attached to the guide frames 14, 15. . can support frame 1
Between 9 and 20, there is a can support frame 19,
The can 26 rotatably attached to 20 is
They are fixedly provided by stoppers 27 provided on the can support frames 19 and 20.
Inside the can 26 is a fuel assembly 2 containing a damaged fuel rod.
9 is fitted and held on the can 26 by a holding mechanism 30 rotatably attached to the can 26. The holding mechanism 30 is connected to a cylinder mechanism 28 rotatably attached to the side wall of the can 26, and is configured to be rotated by the cylinder mechanism 28. This can 26 is reversed in the water of the fuel transfer canal 11 by a reversing mechanism 31, and is fixed by stoppers 27 and 32. Therefore, the fuel assembly 29 in the can 26
is fixed with the lower nozzle 33 positioned above the upper nozzle.

A fifth XY table 35 is placed on the upper fixed plate 13.
In the figure, it is provided movably in the directions of arrows A, B; C, D (X-axis, Y-axis). XY table 3
5 is a first rail 37 that is slidably fitted in two parallel rails 37 provided on a base 36 on the upper fixing plate 13 in the directions of arrows A and B (X-axis direction) in FIG. table 38 and this first table 38
The second table 40 is fitted onto two parallel rails 39 provided in the table so as to be slidable in the directions of arrows C and D (Y-axis direction) in FIG. The first table 38 is screwed to a screw rod 41 rotatably attached to the base 36, and is moved in the directions of arrows A and B by the rotation of a motor 42 connected to the screw rod 41. ing. The second table 40 has two parallel T-grooves 43, and is moved in the directions of arrows C and D by the rotation of a motor 45 connected to a screw rod 44 rotatably attached to the first table 38. It is made so that it can be done.

The second table 40 has a tool mounting plate 46.
It is fitted into the T-slot 43 and attached so that its position can be adjusted freely. As shown in FIG. 8, a hole 47 is formed in the tool mounting plate 46, and a housing shaft 48 is fitted into the hole 47 so as to be vertically movable. A rack 49 is formed on the upper outer peripheral surface of the housing shaft 48, and a tool mounting plate 46 is attached to the rack 49.
A pinion 51 rotatably attached via a shaft 50 is engaged with a predetermined location. Axis 5
A handle 52 is attached to the housing shaft 48, and rotation of the handle 52 causes the housing shaft 48 to move up and down via the pinion 51 and the rack 49. A motor (rotary drive machine) 53 is attached to the upper end of the housing shaft 48 . Further, within the housing shaft 48 , a drive shaft 54 is coupled to a joint 56 attached to a rotating shaft 55 of a motor 53 so as to be vertically slidable and to rotate together with the rotating shaft 55 . Further, a flange 57 is provided on the upper part of the drive shaft 54, and a spring 59 is interposed between the flange 57 and a spring seat 58 formed on the housing shaft 48. 54 is biased upward. A hexagonal hole 60 is formed at the lower end of the drive shaft 54. A connecting fitting 62 is attached to the housing shaft 48.
A lever 63 is rotatably attached via the lever 63, and when the lever 63 is rotated in the direction of arrow E in FIG. 8, the drive shaft 54 is lowered relative to the housing shaft 48 against the force of the spring 59. , when the force acting on the lever 63 in the direction of arrow E is removed, the force of the spring 59 causes the drive shaft 54 to return. Further, a housing (one component of the housing shaft 48) 64 is detachably attached to the lower end of the housing shaft 48 with a set screw 65. The housing 64 has a tool insertion hole 6
6, and recesses 67 and 68 are formed at both ends of the tool insertion hole 66. Further, a mounting portion 69 is provided on one side of the housing 64, and this mounting portion 69 has a communication hole 7 that communicates with the tool insertion hole 66.
0 is formed. The recess 68 consists of a small diameter part and a large diameter part, and a spring 71 is fitted into the small diameter part, and a stopper 72 is fitted into the large diameter part.
A screw hole is formed in the stopper 72. A tool 73, which is fitted into the recess 67, passed through the tool insertion hole 66, and screwed into the stopper 72, is fitted into the hexagonal hole 60 and detachably attached to the lower end of the drive shaft 54.

Further, a space 74 is formed between the inner peripheral surface of the recess 67 and the tool 73.

A chip collection device 75 is attached to the attachment portion 69 . This chip collecting device 75 is operated by a motor 76 attached to the upper part of the wall 12 as shown in FIG.
, a centrifugal pump 77 having a suction pipe 77a inserted into the water, an ejector 78 connected to the centrifugal pump 77, a discharge pipe 79 connected to the ejector 78 and inserted into the water, and a suction pipe 77a of the ejector 78. It consists of a flexible hose 81 that connects the section 80 and the mounting section 69 of the housing 64, and a filter 82, pots 83, 84, and a strainer 85 interposed in the conduit of the flexible hose 81. Note that 86, 87, and 88 are all hanging tools.

On the other hand, the lower nozzle 33 of the fuel assembly 29 is held in the can 26 and fixed in water with the lower nozzle 33 positioned above the upper nozzle.
A positioning plate 91 is placed on top of the . A guide hole 90 is formed in the positioning plate 91 so as to face the end of the control rod guide tube 89 attached to the lower nozzle 33 in FIG. A clamping plate 92 is attached to the upper and left side of the positioning plate 91 in FIG. The holding plate 92 is brought into contact with the side surface of the lower nozzle. Brackets 93 are provided on the opposite side of the two clamping plates 92 of the positioning plate 91, and clamping claws 94 are rotatably attached to these brackets 93 by shafts 95. Further, a guide pin 96 is provided upright in the center of the positioning plate 91. As shown in FIGS. 10 to 14, this guide pin 96 has large diameter portions 9 with a circular cross section located at both ends thereof.
7 and 98, a small diameter portion 99 with a circular cross section and a medium diameter portion 100 with a substantially oval cross section located between these. Further, a guide body 101 is fitted into the guide pin 96 so as to be vertically slidable. A recess 102 is formed in the guide body 101 . This recess 102 includes a small diameter part 103 with a circular cross section located at the lower end, an oval hole part 104 with an oval cross section located at the upper end, and a medium diameter part 105 with a circular cross section slightly larger than the small diameter part 103. This medium diameter portion 105
It has a large diameter portion 106 having a circular cross section and a slightly larger diameter. A disk-shaped spacer 107 is fitted into the middle diameter portion 105 . In the center of the spacer 107, there is a substantially oval-shaped hole 108a and a circular hole 1.
08b is formed. Furthermore, a groove 109 is formed on the upper surface of the spacer 107. The spacer 107 is urged upward by a spring 110 fitted into the small diameter portion 103. The clamping claw 9 is attached to the outer peripheral surface of the lower end of the guide body 101.
As shown in FIG. 7 and FIG.
It is rotatably attached via the The other end of the link 111 is rotatably attached to the upper end of the clamping claw 94 via a shaft 113. When the guide body 101 is separated from and above the positioning plate 91, the link 111 and the clamping claw 94 are in the position shown by the two-dot chain line in FIG.
The tip of is spaced apart from the lower nozzle 33. When the guide body 101 is in contact with the positioning plate 91, the link 111 and the clamping claw 94 are in the position shown by the solid line in FIG.
, and the positioning plate 91 is fixed to the lower nozzle 33. A hanging tool 114 is detachably fitted into the oval hole 104 and the large diameter section 106 of the guide body 101. A recess 115 having a circular cross section is formed at the lower end of the hanger 114 . Further, a collar 116 that fits into the oval hole 104 of the guide body 101 is provided on the outer periphery of the lower end of the hanging tool 114.
A protrusion 117 that fits into and removes from the groove 109 is formed at the lower part of the groove. A hanging ring 1 is attached to the upper end of the hanging tool 114.
18 are provided.

Next, the operation of the nozzle dismantling device in the fuel assembly configured as described above will be explained. To remove the lower nozzle 33 from the fuel assembly 29, fit the lower end of the hanger 114 into the oval hole 104 and large diameter part 106 of the guide body 101, fit the protrusion 117 into the groove 109, and remove the guide body. Rotate the hanging tool 114 by 90 degrees with respect to the hanging tool 101.
be suspended using a pit crane, etc. Then,
The collar 116 is attached to the upper part of the guide body 101, and the large diameter part 98
are respectively engaged with the spacers 107, and the spacers 107 are engaged with the guide body 101 against the force of the spring 110. As a result, the hanging tool 11
A positioning plate 91 is suspended together with 4. At this time, the guide body 101 and the positioning plate 91 are separated. In this state, place the positioning plate 91 together with the hanger 114 so that the lower nozzle 3 is positioned above the upper nozzle.
3 is located above the lower nozzle 33 of the fuel assembly 29 fixed in the water with the uppermost part located 3 m or less from the water surface of the fuel transfer canal 11,
The cylinder mechanism 28 is operated to collapse the holding mechanism 30, and the can 26 is placed with the upper part opened. At this time, the holding plate 92 is brought into contact with the side surface of the lower nozzle 33 as shown in FIGS. 7 and 8. Next, when the hanging tool 114 is pushed down, the positioning plate 9
1, the upper part of the clamping claw 94 is pushed by the link 111 in the direction of arrow F in FIG. 8, and the clamping claw 94 rotates in the direction of arrow G in the figure. As a result, the clamping plate 92 and the clamping claw 9
The positioning plate 91 is fixed to the lower nozzle 33 by sandwiching the lower nozzle 33 between the lower nozzle 33 and the lower nozzle 33. Here, the hanging tool 114 is rotated by 90 degrees with respect to the guide body 101. At this time, the guide pin 96, the guide body 101, the spacer 107, and the hanger 114 are in the positional relationship shown in FIGS. 100. Further, the guide body 101 is connected to the spring 110 with respect to the positioning plate 91.
Since the clamping claws 94 are pressed against each other by the force of , rotation of the clamping claws 94 is locked. Thereafter, the hanging tool 114 is pulled up, pulled out from the guide body 101, and removed from above the lower nozzle 33.

Next, the motors 42 and 45 are operated to move the XY table 35, and the tool 73 is moved to the positioning plate 91.
is positioned directly above the guide hole 90 of.

Next, turn the handle 52 to rotate the housing shaft 4.
8 is lowered, and the lower end of the housing 64 is fitted into the guide hole 90. Then, the motor 53 is operated to rotate the tool 73, the lever 63 is further operated to lower the tool 73, and the upper surface of the thimble screw 121 screwed into the lower nozzle 33 is cut. As a result, the welded portion of the detent pin 122, which is fitted into the groove of the thimble screw 121 and welded to the lower nozzle 33, is cut and removed. Chips during cutting are removed from the housing 64 and the tool 73.
The chips pass through the space 74 between them and the communication hole 70, and are sucked into and collected by the chip collection device 75 shown in FIG. The chip collecting device 75 collects the locking pin 122 after cutting. After collecting this detent pin 122, thimble screw 121
is loosened by turning it with the nozzle removal tool 123 shown in FIG.
That is, the removal tool 123 is a long connecting rod 12.
4 is connected to a tool 124a that fits into the groove of the thimble screw 121.The upper end of the connecting rod 124 is turned on the upper fixed plate 13 to rotate the tool 124a, and the thimble screw 121 is removed from the lower nozzle 33. Get it out. Thereafter, the thimble screw 121 is collected by suction using a suction tool (not shown).

Next, the nozzle handling tool 125 shown in FIG. 16 is suspended from above the upper fixing plate 13, the claw body 126 of this nozzle handling tool 125 is hooked on the leg part 127 of the lower nozzle, and the nozzle handling tool 125 is lifted upward. They are pulled up slightly, moved further to the side, and temporarily stored at an appropriate location underwater in the fuel transfer canal 11. The nozzle handling tool 125 moves the actuator 129 and the handle 130 up and down with respect to the tool head 128, thereby moving the pawl body 126 rotatably attached to the tool head 128 as shown by the two-dot chain line in FIG. It can be rotated between the position shown by and the position shown by the solid line.

In addition, for fuel assemblies that have unburned fuel rods and are to be reused, after pulling out the damaged fuel rods from the fuel assembly and inserting dummy rods in their place,
A lower nozzle of the type in which a control rod guide tube is attached to the lower nozzle by a locking cap screw 132 is attached to the nozzle handling tool 125, and the fuel assembly 29 from which the damaged fuel rod is pulled out is attached.
The lower nozzle is fitted to the control rod guide tube, and the locking cap screw 132 fitted to the lower nozzle is inserted into the control rod guide tube.
They are screwed together using a nozzle installation tool 131 shown in FIG. 7, and the end of the control rod guide tube is caulked to the lower nozzle. Note that the nozzle installation tool 131 connects the tool 1 to the connecting rod 124 of the nozzle removal tool 123.
31a are connected.

Incidentally, each cylinder mechanism is connected to a pipe, and these pipes are appropriately extended to the upper fixing plate 13 and connected to an operating unit (not shown) provided on the upper fixing plate 13. In addition, the operation of each of the mechanisms is performed by appropriately moving the television cameras 133, 134 shown in FIGS. 2 and 4.
All of this is done on the upper fixing plate 13 while being monitored by 4. The television cameras 133 and 134 are also moved on the upper fixed plate 13 via connecting rods connected to the television cameras 133 and 134.

As explained above, according to the present invention, the holding tool is slidably and detachably attached to the guide pin of the positioning plate having the holding plate and the holding claw, and the holding tool is rotated to rotate the holding claw. The positioning plate is attached to the lower nozzle located at the top of the fuel assembly fixed in water, and the housing shaft, which is vertically attached to an XY table movably provided at the top of the water tank, is moved up and down. The lower nozzle of the fuel assembly fixed in the water is connected to the lower nozzle of the fuel assembly fixed in the water at the upper part of the water tank. Attach a positioning plate to the tank, and use a tool to cut the attachment part between the lower nozzle and each control rod guide tube through the guide hole of the positioning plate by operating the upper part of the water tank, thereby removing the lower nozzle from the fuel assembly. be able to. Therefore, spent fuel assemblies can be transported for reprocessing, and damaged fuel rods can be removed from unburned fuel assemblies, dummy rods can be inserted in their place, and other The attachment of a seed lower nozzle allows the fuel assembly to be reused, resulting in significant cost savings.

[Brief explanation of the drawing]

Fig. 1 is a partially omitted longitudinal cross-sectional view of a fuel assembly loaded in a conventional nuclear reactor, Fig. 2 is a partially omitted front view showing an embodiment of the present invention, and Fig. 3 is its main components. FIG. 4 is a partially omitted side view of the section, FIG. 5 is a plan view thereof, and FIG. 6 is a side view of the main parts thereof.
Figure 7 is a plan view showing the positioning plate attached to the lower nozzle, and Figure 8 is a partial view showing the positioning plate attached to the lower nozzle, the tool attached, and the tool cutting. 9 is a diagram showing the chip collecting device, FIG. 10 is a vertical sectional view showing one state of attachment of the positioning plate and the hanging tool, and FIG. 11 is a diagram showing the XI- of FIG. 12 is a cross-sectional view along line XII--XII of FIG. 10, FIG. 13 is a cross-sectional view along line - of FIG. 10, and FIG. 14 is a cross-sectional view of - of FIG. 10. Cross section along line, 1st
Figure 5 shows the state in which the thimble screw of the lower nozzle is rotated by the nozzle removal tool.
Fig. 16 is a partially omitted longitudinal sectional view showing a state in which the nozzle handling tool is engaged with the lower nozzle;
The figure shows a state in which the locking cap screw of the lower nozzle is rotated by a nozzle installation tool. 1... Fuel transfer canal (water tank), 13... Upper fixing plate, 16, 17... Lower fixing plate, 18...
Overhang member, 26...Can, 27, 32...Stopper, 29...Fuel assembly, 30...Holding mechanism, 33...Lower nozzle, 35...XY table, 48...Housing shaft, 52...Handle ,
53... Motor (rotary drive machine), 54... Drive shaft, 63... Lever, 64... Housing, 73
... Tool, 75 ... Chip collection device, 89 ... Control rod guide tube, 90 ... Guide hole, 91 ... Positioning plate, 92 ... Holding plate, 94 ... Holding claw, 96 ...
Guide pin, 107... Spacer, 111... Link, 114... Hanging tool, 121... Thimble screw, 122... Stopping pin, 123...
Nozzle removal tool, 125... Nozzle handling tool, 131... Nozzle installation tool, 132... Locking cap screw, 133, 134...
...TV camera.

Claims (1)

[Claims] 1. A positioning plate having a holding plate on one side, a holding claw rotatably attached on the other side, and a positioning plate having a number of guide holes with a guide pin provided in the center, and a positioning plate that is slidable on the guide pin. The lower nozzle is positioned above the upper nozzle by rotating the clamping claw through a connecting member that is fitted onto the positioning plate and detachably attached to the positioning plate, and connected to the clamping claw, so that the lower nozzle is positioned above the upper nozzle, and the lower nozzle is placed above the upper nozzle. a hanger for attaching the positioning plate onto the lower nozzle of the fuel assembly fixed to the water tank;
A housing shaft that is vertically and vertically movably connected to the XY table and whose lower end is slidably fitted into the guide hole, and a housing shaft that is vertically movable and rotatable within the housing shaft established in
1. A nozzle dismantling device for a fuel assembly, comprising a drive shaft rotated by a rotary drive machine, and a tool detachably attached to the lower end of the drive shaft.