JPH0731199Y2 - Tools for handling expansion springs of nuclear fuel assemblies - Google Patents

Description

[Detailed Description of the Invention] << Industrial Application Field >> The present invention relates to a lock nut, a washer, and an upper tie plate when disassembling and inspecting a nuclear fuel assembly irradiated in a BWR plant in pool water. After removing the above, the expansion spring left attached to the upper end plug of the fuel element is pulled up and removed, and after the inspection is completed, the above expansion spring is attached to the upper end plug for assembly of the assembly. The present invention relates to a nuclear fuel assembly expansion spring handling tool suitable for use in mounting.

<< Prior Art >> A BWR nuclear fuel assembly is configured as follows, as is known.

That is, as shown in FIG. 4, for example, in the fuel element a arranged in an aligned state of a square lattice of 8 × 8, an expansion spring c is fitted on the upper end plug b thereof, and By lowering the upper tie plate d from above, the above-mentioned upper end plug b is fitted into the insertion hole (not shown), and thereby the expansion spring is in a compressed state.

Here, of the upper end plugs b, only eight of the fuel elements a arranged on the outermost peripheral side are tie rod type upper end plugs b ′ having a large axial length, and therefore the screw portion thereof e
Project upward from the upper tie plate d.

Therefore, a nut g is attached to the screw portion e through a washer f.
By screw-fastening, the large number of fuel elements a and the upper tie plate d are integrally fixed, and the assembly is completed.

Therefore, in the case of performing the disassembly inspection on the fuel element a as described above for the nuclear fuel assembly A as described above, the disassembly work is first performed in the pool water in consideration of the reduction of the exposure of the worker. For this purpose, as already mentioned, remove the nut g and the washer f, then pull up the upper tie plate d, and after removing it, make sure that the expansion spring c is not dropped into the pool water. First, it has to be taken out of the water.

In such a case, of course, a tool for that purpose is required, but as a conventionally used tool for handling this type,
The ones shown in FIGS. 6 and 6 are known.

In the illustrated handling tool B, the outer cylinder m ₄ is screwed downward as shown by an arrow h by rotating the grip m ₃ with respect to the main body m ₂ having the handle m _1. when the drilling of holes m ₆ to the lower end of the inner cylinder m ₅ was hung from the grip m _3, ball
have been m ₇ is fitted, the tapered surface m ₈ in the outer tube m ₄ came to screwing of the said ball m ₇ is pushed inward, accommodated in the inner cylinder m in ₅ this in pitch in the expansion spring c of the upper end plug b to which said balls m ₇
It comes to be engaged.

Therefore, from this state, hold the handle m ₁ and handle the tool B.
Lifting up, while holding the expansion spring c,
The expansion spring c can be removed from the upper end plug b by pulling up the entire handling tool B.

Then, the removed expansion spring c is
Since it is left in the inner cylinder m ₅ , by rotating the grip m ₃ in the reverse direction to move the outer cylinder m ₄ upward, the pushed state of the ball m ₇ is released, and then the ball is inserted into the main body m _2. The expansion spring c can be detached from the inner cylinder m ₅ by pressing a certain push rod m ₉ .

However, during the irradiation fuel assembly inspection at the BWR plant,
In the target nuclear fuel assembly, a thin neck portion i is formed at the base portion of the upper end plug b as shown in FIG.
There is one designed so that the expansion spring c does not fall from the upper end plug b by fitting the small-diameter end portion c ′ of the expansion spring c therein.

In the case of such an expansion spring c, when the conventional handling tool B is used, the ball m ₇ is the expansion spring c.
Since the expansion spring c is to be removed by a force of manually pulling up the entire handling tool B, the engagement of the small-diameter end portion c ′ with the thin neck portion i is reliably removed. That is extremely difficult.

<Problems to be Solved by the Invention> In view of the above-mentioned conventional problems, the present invention provides a chuck at the lower end of the inner cylinder, and the chuck can be retracted by lowering the outer cylinder. The expansion spring locking part such as chevron teeth formed on the chuck mouth not only securely locks the expansion spring, but also pushes the lower end pressing part of the pushing rod against the upper end plug to By making it possible to apply a pulling force to the cylinder so that it can be pulled up by a large external force with sufficient locking of the expansion spring, any expansion spring can be easily and surely removed. The purpose is to easily attach the expansion spring to the narrow neck portion of the upper end plug even when the nuclear fuel assembly is assembled.

Next, in claim (2), at the time of the pushing operation of the pushing rod in claim (1), the screw means is utilized to give a sufficient pulling force to the inner cylinder, and in claim (3), The purpose is to effectively increase the pulling force by effectively utilizing the force.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a grip formed at the upper end of the inner cylinder on the gripping base in a stopped state. Engaging so as to be rotatable, extending the inner cylinder downward, and screwing the upper end male screw portion of the outer cylinder covered on the outer side of the inner cylinder to the female screw portion of the grip,
A chuck mouth having a locking portion for an expansion spring is formed on the lower end side of the inner cylinder, and a chuck that is retractable by an outer cylinder that is screwed down by the turning operation of the grip is provided. A push rod having a lower end pressing portion that can come into contact with the upper end plug of the fuel element in the nuclear fuel assembly inserted from the chuck port is inserted into the axial center portion of An object of the present invention is to provide a tool for handling an expansion spring of a nuclear fuel assembly, which is equipped with a transmission means that is inserted into the inner cylinder and that transmits a pulling force to a gripping base portion when the push rod is pressed.

The content of claim (2) is that in the above-mentioned claim (1), the transmission means of the gripping base portion and the pushing rod for penetrating so as to be able to move up and down on the gripping base portion is provided in the gripping base portion. The male screw portion of the push rod is screwed into the screw mouth.

Further, according to claim (3), the transmission means of the gripping base portion and the push rod of the penetrating so as to be able to vertically move the gripping base portion according to this (1), the pushing rod from the gripping base portion. In the protrusion, a return spring is fitted between the upper lever of the push rod and the grip base, and the grip base is provided with an upper end fixing lever that can be gripped together with the upper lever. The content is that a guide protrusion projecting from the push rod is engaged with the vertically elongated guide groove so as to be movable up and down.

<Operation> When the handling tool according to the present invention is lowered, the upper end plug having the expansion spring of the fuel element is pulled from the chuck opening of the inner cylinder,
When the grip is screwed into the grip base in a predetermined direction after being inserted into the chuck, the outer cylinder of the screw fitting is screwed down to the male screw part and the chuck mouth is contracted. The locking portion for the expansion spring, such as a chevron tooth protruding from the base, is newly locked within the pitch of the expansion spring, and the locked state is maintained.

Here, in the case where the male screw portion of the push rod is screwed into the female screw opening of the grip base (FIG. 1), the push rod is screwed in a predetermined direction to screw it. When it is advanced and lowered, its lower end pushing part comes into contact with the tip part of the upper end plug, and by continuing screwing, the grip body, the grip and the inner cylinder will move upward. The expansion spring is pulled up by the movement and is removed from the upper end plug.

In addition, the push rod has an upper end lever and a return spring, and the grip base has an upper end fixing lever and a guide longitudinal groove into which a guide protrusion of the push rod is vertically movable. In the case of Fig. 3), by operating the upper end fixing lever and the upper end lever so as to be tightened, the inner cylinder having the gripping base and hence the chuck against the push rod pressed against the upper end plug. Can be moved upwards, and this pulling force pulls the expansion spring from the upper end plug.

<Embodiment> The present invention will be described in detail with reference to the illustrated embodiment. As shown in FIGS. 1 and 2, the gripping base 2 having the handle 1 includes an upper small cylinder portion 2a and a lower large cylinder portion. 2b and the engaging peripheral groove 2c formed in the inner peripheral wall of the lower large tubular portion 2b, the grip 3
The upper end protruding peripheral portion 3a of the grip engages, whereby the grip 3 can be freely rotated with respect to the grip base 2, and the inner cylinder 4 fixed to the inner wall of the grip 3 extends long downward. Has been issued.

Furthermore, in the above-mentioned grip 3, a female screw portion 3c is engraved on the inner peripheral wall of the lower cylinder portion 3b, and the upper end male part of the outer cylinder 5 which is mounted on the outer side of the inner cylinder 4 The screw portion 5a is screwed.

A chuck 6 having a required number of vertical slits 6a formed in the lower end opening is formed on the lower end side of the inner cylinder 4, and a lower end of the chuck 6 protruding downward from the outer cylinder 5 is formed. The chuck mouth 6b is opened.

The chuck mouth 6b has a required number of expansion spring engaging portions 6c protruding in a chevron-like shape, a serrated shape, or the like on its inner peripheral wall.
Is provided.

The chuck 6 has a chuck opening formed by rotating the grip 3 in a predetermined direction and screwing the outer cylinder 5 downward by screwing the female screw portion 3c and the upper male screw portion 5a.
In the illustrated example, the outer peripheral wall of the chuck 6 is formed with a taper sliding surface 6d having a larger diameter toward the lower end so that the lower end of the outer cylinder 5 slides. It is free.

Further, the small rod portion 2a of the gripping base portion 2 has a pushing rod 7 having an axial lower end portion and having a lower end pushing portion 7a which is inserted through the inner barrel 4 so as to be vertically movable. In addition, a transmission means is provided for transmitting the pulling force to the grip base 2 when the push rod 7 is pressed.

Therefore, in order to configure the transmission means, in the embodiment according to claim (2) of FIG. 1, the push rod 7 is provided with the upper end lever 7b in a protruding manner, and the upper end side is provided with the screw portion 7c. Is
This is screwed into a female screw opening 2d opened in the top plate portion of the small tube portion 2a.

On the other hand, in the transmission means of the embodiment according to claim (3) of FIG. 3, the pushing rod 7 is not moved up and down by the screw mechanism as described above, but is projected upward from the small tubular portion 2a. At the protruding portion of the push rod 7, a return spring 8 is fitted between the upper end lever 7b and the small tube portion 2a, and an upper end fixing lever 2e is provided on the upper side of the small tube portion 2a. The guide protrusion 7d of the pushing rod 7 is engaged with the guide rod 7d of the push rod 7 so as to be movable up and down.

Therefore, in order to remove the expansion spring from the upper end plug with the above handling tool, the tool is lowered with the chuck port 6b open as shown in FIG. 1, and the fuel is fed from the chuck port 6b into the chuck 6. The upper end plug b with the expansion spring c of the element a is inserted.

When the grip 3 is rotated in the predetermined direction with respect to the grip base 2 in this state, the outer cylinder 5 descends as described above, so that the lower end of the outer cylinder 5 is slidably contacted with the taper sliding surface 6d. Becomes a contracted state, the expansion spring locking portion 6c of the chuck opening 6b bites into the pitch of the expansion spring c, and this state is maintained.

Next, in the embodiment shown in FIG. 1, the push rod 7 is screwed by the operation of the upper end lever 7b, whereby the push rod 7 is screwed down and the lower end pressing portion 7a is moved to the upper end plug b. Abut the upper end.

If the pushing rod 7 is further screwed from this state, the gripping base 2 is raised by the screwing with respect to the pushing rod 7 which does not descend further, so that the expansion spring c together with the base 2. The chuck 6 of the inner cylinder 4 that has been gripped is also pulled up, and as a result, as shown in FIG. 2, the small-diameter end portion c ′ of the expansion spring c is engaged with the thin neck portion i of the upper end plug b. However, the expansion spring c can be detached from the upper end plug b.

In this way, if only the expansion spring c is left in the chuck 6, of course, after the tool is transferred from the pool water to a proper position, the grip 3 is reversed to screw the outer cylinder 5 upward. As a result, the chuck port 6b is restored to its original shape and is in the expanded state, so that the expansion spring c can be taken out from the tool.

Next, at the time of assembling the nuclear fuel assembly, the expansion spring c is housed in the chuck 6, and the tool is kept in the locked state by the expansion spring locking portion 6c of the chuck port 6b. , The expansion spring c can be easily set up to the thin neck portion i, and when the setting is completed, the grip 3 is rotated to release the above-mentioned locked state, and then the tool is pulled up. so,
The expansion spring c can be fitted on the upper end plug b.

Next, in the case of the configuration as shown in FIG. 3, the upper end lever 7b of the push rod 7 and the upper end fixing lever 2e of the grip base 2 as described above.
When the push rod 7 is pushed down by pushing the lower end pushing portion 7a against the upper end stopper b as described above, the holding base 2 and the grip are gripped via the upper end fixing lever 2e. The pulling force acts on the outer cylinder 5, the outer cylinder 5, and the inner cylinder 4, and the chuck 6 is pulled up, so that the expansion spring c is removed upward from the upper end plug b. Substantially the same as the contents already described for the embodiment,
In addition, the presence of the return spring improves the operability.

<Effect of the Invention> When using the handling tool according to claim (1), the expansion spring is lowered by the turning operation of the grip, so that the expansion spring is firmly locked by the expansion spring locking portion of the chuck opening. Since the chuck can be held relatively and the chuck can be pulled up relatively strongly by the downward movement of the push rod, even if the expansion spring is difficult to remove from the upper end plug, this can be done easily, quickly and securely. It can be removed.

Further, according to claim (2), since the lifting and lowering of the push rod is realized by the screwing means, a strong pulling force can be applied to the expansion spring by an easy work which is a screwing operation of the push rod. Further, in the case where the lifting and lowering operation of the push rod is performed by the gripping operation of the lever according to claim (3), it is possible to achieve the same purpose with a simpler configuration without the need for screwing.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an embodiment of a tool for handling an expansion spring according to the present invention, FIG. 2 is an enlarged vertical sectional front view of a main portion showing a lower end side of the same tool in use, and FIG. FIG. 4 is a front view of the main part on the upper end side showing another embodiment.
FIG. 5 is a front view showing the upper half of the BWR nuclear fuel assembly, FIG. 5 is a partially cutaway front view showing a conventional same-type handling tool, and FIG. 6 is a main part showing the lower end side of the same tool when in use. FIG. 7 is an enlarged front view of the vertical section, and FIG. 7 is a front view of the essential parts showing the relative relationship between the upper end plug showing a certain fuel element of the nuclear fuel assembly and the expansion spring. 2 …… Grip base 2d …… Female screw mouth 2e …… Upper end fixing lever 2f …… Guide vertical groove 3 …… Grip 3c …… Female screw part 4 …… Inner cylinder 5 …… Outer cylinder 5a …… Upper male screw Part 6 …… Chuck 6b …… Chuck port 6c …… Expansion spring locking part 7 …… Push rod 7a …… Lower end pressing part 7b …… Top lever 7c …… Male screw part 7d …… Guide protrusion 8…. … Return spring A …… Nuclear fuel assembly a …… Fuel element b …… Upper end plug

Claims (3)

[Scope of utility model registration request] 1. A grip formed at the upper end of the inner cylinder is rotatably fitted to the gripping base so as to be rotatable in a retaining state, the inner cylinder extends downward, and the grip is formed outside the inner cylinder. The upper male screw portion of the covered outer cylinder is screwed into the female screw portion of the grip, and a chuck port having a locking portion for an expansion spring is formed on the lower end side of the inner cylinder, and the grip of the grip is formed. A chuck that can be retracted by an outer cylinder that descends by screwing is provided by a turning operation, and an axial end portion of the gripping base is provided with an upper end plug of a fuel element in a nuclear fuel assembly loaded from the chuck mouth. A push rod having a lower end pressing portion that can abut is inserted into the inner cylinder so as to be vertically movable, and is equipped with a transmission means for transmitting a pulling force to the grip base by pressing the push rod. Tools for handling expansion springs of existing nuclear fuel assemblies. 2. A gripping base part and a transmission means of a push rod inserted through the grip base so as to be able to move up and down. The male screw portion of the push rod is screwed into a female screw opening penetrating the grip base portion. A tool for handling an expansion spring of a nuclear fuel assembly according to claim 1. 3. A gripping base and a transmission means of a push rod inserted through the grip so that it can be moved up and down. The transmission means is located on the push rod protruding portion from the grip base, and the upper end lever of the push rod and the grip base are provided. A return spring is fitted between the upper end lever and the upper end fixing lever that can be grasped together with the upper end lever. The guide protrusion is engaged so as to be movable up and down.
A tool for handling an expansion spring of the described nuclear fuel assembly.