JP3593006B2 - Burnable Poison Tool - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tool for inserting and removing a burnable poison (BP), which is a kind of insert of a fuel assembly used in a pressurized water nuclear power plant.
[0002]
[Prior art]
The fuel assemblies used in pressurized water nuclear power plants contain control rod assemblies (RCCs) containing neutron absorbers and combustible absorbers to suppress excess reactivity by absorbing neutrons. A combustible absorption rod assembly (BP) comprising a plurality of combustible absorption rods and a thimble plug are inserted therein. And BP handling tools are manufactured according to the respective shapes. The thimble plug is usually handled in the latter.
[0003]
Among these, the BP handling tool has a plate called a comb for positioning the BP rod at one position at the lower end of the tool to prevent the BP rod from oscillating. Conventionally, the comb is operated by a drive system using an air cylinder. Opening and closing.
However, in the above-mentioned conventional BP handling tool, the comb for positioning the rod is driven horizontally using an air cylinder, so that the comb protrudes outside the size of the fuel assembly when the comb is opened. In addition, the size of the air cylinder is very large because the air cylinder for driving the air cylinder is located outside the air cylinder.
[0004]
In addition, when using a spent fuel rack in a spent fuel pit, if there is a tall structure that comes up from the rack in the adjacent rack, the comb interferes and the tool cannot be used. was there.
In addition, since the tool is large and the bottom cannot be seen, it has been extremely difficult to position the entire tool directly above the fuel assembly.
Therefore, in order to solve the problem of such size and installation in the fuel assembly, a total of four combs 20 in four directions in the directions indicated by arrows at the time of positioning as shown in FIG. Some handling tools are used.
[0005]
[Problems to be solved by the invention]
However, in the device of the falling type, four driving mechanisms are required to move the combs 20 one by one. Further, since the drive shaft always receives the rotational moment due to the weight of the comb, a drive system for overcoming the moment is required. Further, a stopper mechanism 21 for accurately stopping in the horizontal direction when the comb is tilted is required.
[0006]
The present invention addresses the actual situation as described above, and focuses particularly on the comb drive mechanism for positioning the rod, and achieves simplification of the mechanism by simplifying the mechanism and achieves a reduction in the size of the entire tool. It is another object of the present invention to facilitate installation in a fuel assembly and to enable comb driving with a small force.
[0007]
[Means for Solving the Problems]
That is, a feature of the present invention that achieves the above object is that in a burnable poison handling tool including two combs facing each other at right angles, two facing combs are formed so as to be rotatable in the horizontal direction from the upper side. On the other hand, the other two facing combs orthogonal to the comb are formed so as to be rotatable in the horizontal direction from below, and each of the two orthogonal combs is rotated by one drive shaft. In addition, the two combs rotating from the upper side and the two combs rotating from the lower side are brought into contact with each other and stopped, so that a stopper at the horizontal position is unnecessary.
[0008]
The invention according to claim 2 is a preferred rotary drive mechanism of each comb described above, wherein small bevel gears are respectively attached to both ends of each of two orthogonal combs, and the small bevel gears are connected to one drive shaft and an idle shaft. The comb is driven by a single drive shaft through a large bevel gear of the idle shaft and a small bevel gear of the comb.
By using this drive mechanism, it is possible to drive the comb with a very small force.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show an example of a comb drive mechanism according to a main part of the present invention. FIG. 1 shows a comb opened state, and FIG. 2 shows a comb closed state.
[0010]
In these figures, reference numerals 1 and 2 denote two combs related to one pair of two pairs of combs facing each other orthogonally, and reference numerals 3 and 4 relate to another pair orthogonal to the combs 1 and 2. Two combs.
[0011]
The bevel gears 5, 5 ', 6, 6', 7, 7 ', 8, 8' are attached to both ends of each of the two pairs of orthogonal combs 1, 2, 3, 4 respectively. A large bevel gear 10 attached to a drive shaft 9 for driving the comb is engaged with one of the opposed small bevel gears, in the figure, the small bevel gears 5 and 7, and the other bevel gears mesh with each other. Large bevel gears 14, 15, 16 attached to idle shafts 11, 12, 13 mesh with the small bevel gears 5 ', 8, 6, 8', 6 ', 7', respectively.
[0012]
In this case, the small bevel gears 5, 5 ', 6, 6' of the combs 1, 2 are attached to the tip of a shaft attached to both sides of the lower surface of the comb, while the small bevel gears 7, 7 ', 8, and 8' are attached to the shaft ends attached to both sides of the upper surface of the comb, and when the drive shaft 9 is rotated clockwise as viewed from above, the small bevel gears and the large bevel gears of the idle shaft are rotated. Comb 1 and comb 2 rotate from the upper side in the horizontal direction, while comb 3 and comb 4 rotate from the lower side in the horizontal direction, and when they are just horizontal, as shown in FIG. When the combs 1 and 2 rotating from the upper side come into contact with the combs 3 and 4 rotating from the lower side, the rotation stops, and the two serve as stoppers to stop the horizontal position of the comb. Therefore, it is not necessary to provide a separate stopper mechanism as in the related art.
[0013]
During the rotation of the comb, the comb 1 and the comb 2 generate a torque such that they rotate in the horizontal direction due to gravity, while the comb 3 and the comb 4 rotate in the direction away from the horizontal direction due to gravity. Is generated. However, small bevel gears are attached to the combs 1 and 2 and the combs 3 and 4 respectively. , 16 are engaged with each other, so that the torque generated by the combs 1 and 2 and the torque generated by the combs 3 and 4 cancel each other, so that there is no particular need for the drive system to overcome the gravity. The comb can be opened and closed with very little torque just to cause the comb to open and close.
At this time, since the number of the drive shafts is one, and four combs can be driven by the one drive shaft, the mechanism is greatly simplified.
[0014]
Thus, a BP handling tool having approximately the same size as the fuel assembly can be manufactured using the comb drive mechanism.
Further, the above mechanism can also be adopted for a control rod cluster (RCC) handling tool using a comb and a handling tool shared by BP and RCC.
[0015]
【The invention's effect】
INDUSTRIAL APPLICABILITY As described above, in the burnable poison handling tool, the two combs facing each other are rotated in the horizontal direction from the upper side by the drive shaft of one comb, and the two combs orthogonal to the combs are used. The comb is rotated in the horizontal direction from the lower side. Each comb rotates by the rotation of one drive shaft, and the comb rotating from the upper side and the comb rotating from the lower side. Stops when it is horizontal, so there is no need to provide a separate stopper mechanism for horizontal stop of the comb as in the past, and the torque generated by the comb from the upper side and the torque from the comb from the lower side is reduced. The combs can be opened and closed with a small torque because they cancel each other, and the mechanism for driving four combs with one drive shaft is extremely simple. It has a remarkable effect that makes it the installation of the body extremely easily.
[Brief description of the drawings]
FIG. 1 is a perspective view of an example of a comb drive mechanism constituting a main part of a handling tool of the present invention, showing a comb opened state.
FIG. 2 is a perspective view of the comb drive mechanism in a state where a comb is closed.
FIG. 3 is a schematic diagram for explaining the operation of a comb of a conventional BP handling tool.
[Explanation of symbols]
1,2 facing comb 3,4 facing comb orthogonal to the comb 5,5 'bevel gear 6,6' bevel gear 7,7 'bevel gear 8,8' bevel gear 9 drive shaft 10 drive shaft Large bevel gears 11, 12, 13 Idle shafts 14, 15, 16 Large bevel gears with idle shafts

Claims (2)

In a burnable poison handling tool including two combs facing each other at right angles, the two combs facing each other are formed so as to be rotatable in a horizontal direction from the upper side, while the other two combs perpendicular to the comb are formed. Are formed so as to be rotatable in the horizontal direction from the lower side, and the two orthogonal combs are rotated by one drive shaft, and the two combs rotated from the upper side. A burnable poison handling tool characterized in that two combs rotating from below are brought into contact with each other to stop the comb, and a stopper at a horizontal position is not required. Small bevel gears are attached to both ends of each of two orthogonal combs, and the small bevel gears are meshed with one drive shaft and a large bevel gear attached to the idle shaft, and the idle shaft is driven by one drive shaft. The burnable poison handling tool according to claim 1, wherein the comb is driven via the large bevel gear and the small bevel gear of the comb.

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