JPH0425679Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a basket for a spent nuclear fuel melting device that holds cut pieces of spent nuclear fuel inside and charges the spent nuclear fuel into the melting device. This invention relates to a basket for a spent nuclear fuel melting device that is improved so that cut pipe residues can be easily discharged.

[Prior Art] Conventionally, when dissolving spent nuclear fuel such as uranium oxide, the spent nuclear fuel is cut into short pieces, and the cut pieces are immersed in an acid solution such as nitric acid to dissolve them.

FIG. 2 is a schematic diagram showing a conventional spent nuclear fuel melting device.

This spent nuclear fuel melting device includes a cylindrical melting tube 12 and a basket 1 charged into the melting tube 12.
4. Basket 14 is porous;
Usually, a cylindrical body made of wire mesh such as stainless steel, or
A metal cylindrical body or the like with a large number of holes is used. In addition, in FIG. 2, in order to show that the basket 14 is porous, the basket 14 is
is indicated by a dashed line.

A plurality of locations on the side surface of the melting tube 12 are connected to a liquid tank 16 called a slab through communication tubes 18, 20, 22, and 24. In addition, at the bottom of the dissolution tube 12,
An oxygen gas blowing pipe 26 is installed. and,
The melting tube 12 and the slab 16 are filled with an acid solution such as nitric acid.

When oxygen gas is blown from the blowing pipe 26, this gas rises in the melting pipe 12, and along with this, the liquid in the melting pipe 12 also rises and flows from the communicating pipe 22 to the slab 16.
It returns to the melting tube 12 through the communication tube 18 and circulates.

A portion of the liquid travels between the slab 16 and the melting tube 12 through a communication tube 20 installed at an intermediate level. The communication pipe 24 is for gas distribution,
Oxygen gas blown into the melting tube 12 from the blowing pipe 26 passes through the communication pipe 24 and enters the slab 16.

Spent nuclear fuel cut into short pieces is charged in the basket 14, and is gradually dissolved in an acid solution according to the following chemical reaction formula.

UO ₂ +2HNO ₃ +1/2O ₂ →UO ₂ (NO ₃ ) ₂ +H ₂ O Although not shown in the slab 16,
A means for extracting an acid solution in which nuclear fuel has been dissolved, a means for supplying a new acid solution, a means for extracting insoluble sludge, etc. are installed. Uranium oxide nuclear fuel is
Usually, it is inserted into a pipe made of stainless steel or the like, but the cutting waste and undissolved matter in the uranium oxide rod become sludge and are included in the acid solution.

Therefore, the pipe itself into which the uranium oxide rod was inserted does not dissolve in the acid solution and remains in the basket 14 even after the uranium oxide has dissolved, so after the melting is completed, the basket 14 is pulled up and the remaining pipe is cut. I need to get things out.

Conventionally, the means shown in FIGS. 3 and 4 have been used to discharge the cut pipes (hereinafter simply referred to as pipes) remaining in the basket 14 after the melting operation has been completed. That is, the basket 14 is lifted up by a crane and extracted from the melting tube 12 (arrow 1 in FIG. 3),
The basket is moved (arrow 2) and placed into the cylindrical basket reversing case 28 (arrow 3). Then, as shown in FIG. 4, the basket reversing case 28 is reversed little by little and the basket is discharged into the drum can 30. In addition, 29 in the figure is a reversal drive device.

[Problems to be solved by the invention] However, the basket 14 is taken out from the melting tube 12, inserted into the inversion case 28, and then the case 28 is gently inverted and the drum can 3 is removed.
In order to successfully discharge the pipe into the 0, a delicate operation by a skilled worker is required and the operation takes a long time.

In addition, the basket has a double-tube structure consisting of an inner tube and an outer tube so that the dissolving solution can easily flow inside the basket, and the spent nuclear fuel is held between the inner tube and the outer tube to ensure even dissolution. The applicant has already proposed a system in which liquid can come into contact with nuclear fuel (patent application
59−126642, 59−129000, 59−129001. The reason why the double tube structure is adopted as described above is as follows. In other words, when cut pieces of spent nuclear fuel are charged into the basket, the liquid flow resistance becomes extremely large, so the liquid tries to bypass the basket and flow along the inner wall surface of the melting tube, so that it does not flow uniformly into the basket. It disappears. On the other hand, if the basket has a double tube structure and the solution is introduced into the inner tube, the solution can be evenly supplied to each part inside the basket. The rate of melting is also equalized in each part of the basket, eliminating uneven melting and shortening the time required per melting cycle. ) In this double-tube structure basket, the pipe is difficult to come out even if the basket is tilted, so the task of discharging the pipe is particularly troublesome.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a basket having a double pipe structure consisting of an inner pipe 32 and an outer pipe 34. Outer tube 3
A bottom cover 36 is provided to close the part between the 4 and 4. This bottom cover 36 is disc-shaped and has a center hole. Moreover, this bottom cover 36 is divided into two halves 3 divided in the diameter direction.
6a and 36b are connected to each other by pivot members 38 and 39 such as hinges so that they can be opened.

Further, a rotatable lock bar 38 is provided along the bottom surface of the bottom cover 36, so that the bottom cover 36 can be supported from below by the lock bar 38.

In the present invention, the term "above" or "bottom" of the basket refers to the top or bottom of the basket in an upright position when it is loaded into the melting device.

[Operation] The basket of the present invention has a porous inner tube 32 and an outer tube 34, and the spent nuclear fuel is charged between the inner tube and the outer tube.

When holding the spent nuclear fuel, the lock bar 38 is turned in a direction perpendicular to the joint of the half bodies 36a, 36b to support the half bodies 36a, 36b and prevent them from opening downward.

When the pipe is to be discharged after the melting is completed, the lock bar 38 is turned along the joint of the half bodies 36a and 36b. Then, the half bodies 36a, 36
b opens downward, and the pipe held between the inner tube 32 and the outer tube 34 falls off from the bottoms of the inner tube 32 and the outer tube 34, and is discharged.

[Example] An example of the present invention is shown in FIGS. 1 and 5 to 1.
This will be explained with reference to FIG.

FIG. 1 is an overall vertical sectional view of the basket 14a according to this embodiment.

This basket 14a has an inner tube 32 and an outer tube 34.
Both the inner tube 32 and the outer tube 34 are made of a porous material such as a wire mesh or a perforated plate with many holes, so that the acid solution can freely pass through the tube wall. can pass. (However, it is not shown that it is porous.) The upper end of the outer tube 34 is enlarged in diameter, as shown in an enlarged view in FIG.
When the basket 14a is loaded into the melting tube 12, this enlarged diameter portion comes into contact with the inner wall surface of the melting tube 12 and supports the basket 14a so that it is in an upright position.

The upper end of the inner tube 32 is fixed to the outer tube 34 in the upper interior of the basket 14a via three ribs 35a fixedly provided so as to extend in the tube axis direction.

Further, the lower part of the inner tube 32 is fixed to the outer tube 34 via three ribs 35b that similarly extend in the tube axis direction.The lower end of the inner tube 32 is located slightly above the lower end of the outer tube 34. The inner pipe 32 and the outer pipe 3
A pipe discharge mechanism is provided that can open and close the bottom of the portion between the pipe and the pipe.

The structure of the lower part of the basket 14a, including the structure of this pipe discharge mechanism, will be explained in detail below with reference to FIGS. 6 to 9.

FIG. 6 is an enlarged perspective view (perspective view) showing the structure of the lower part of the basket 14a, and FIG.
FIGS. 8 and 9a are sectional views taken along lines - and - in FIG. 7, respectively. In each figure, 32, 34
are an inner tube and an outer tube, and the lower end of the inner tube 32 is connected to the inner tube 3 so that it is slightly above the lower end of the outer tube 34.
2 is installed.

Reference numeral 36 denotes a bottom cover, which closes the bottom of a space between the inner tube 32 and the outer tube 34 (hereinafter, this space will be referred to as a filling section). This bottom cover 36 is ring-shaped, and the diameter of its center hole is slightly larger than the outer diameter of the inner tube 32, and the outer diameter is slightly smaller than the inner diameter of the outer tube 34. .

The bottom cover 36 has a ring shape that is divided into two equal parts in the diameter direction, and each half body 36a, 36b is connected by hinges 38, 39. Hinge 38,
39 common mandrels 40, this mandrel 4
0 extends diametrically across the inner tube 32 and outer tube 34 of the basket 14a. This mandrel 40
are fixed to a portion slightly above the lower end of the inner tube 32 and the lower end of the outer tube 34, respectively.

In this way, the bottom cover 36 is divided into two halves 36a,
36b is hinged by hinges 38 and 39, so that it can be folded in the middle at the half-part joining part and opened downward.

The center portion of the mandrel 40 (the portion located at the axis of the inner tube 32) is enlarged to form a boss portion 42. A shaft hole 43 is vertically bored in the boss portion 42, and a short support portion is formed in the boss portion 42. A shaft 44 is inserted therethrough.

As shown in FIGS. 8 and 9a, the length of the support shaft 44 is set to be longer than the length (thickness) in the vertical direction of the boss portion 42 by a predetermined length, and the upper end thereof has a dish-like shape. An enlarged head 46 is formed. Further, at the lower end of the support shaft 44, each half body 36a, 36b of the bottom cover 36 is pushed up from below and supported.
Lock bar 4 that can prevent it from opening downward
8 is attached.

This lock bar 48 has a length approximately equal to the outer diameter of the outer tube 34, and both ends thereof are connected to the outer tube 34.
It is possible to engage with grooves 50 and 52 formed at the lower end of.

Here, the grooves 50, 52 and the engagement relationship between the grooves 50, 52 and the lock bar 48 will be explained.

At the lower end of the outer tube 34, an L-shaped groove 50 is provided at a diametrically opposed position perpendicular to the mandrel 40.
As shown in the figure, this groove 50 is provided with horizontal parts 50b and 5 which are bent at right angles at the inner part (upper part) of the vertical parts 50a and 52a and extend in the horizontal direction.
It consists of 2b. The horizontal portions 50b, 52b are bent in the same direction as the vertical portions 50a, 52b (rightward in the illustrated embodiment) when viewed from the side surface of the basket 14a.

At both ends of the lock bar 48, steps 48a are cut from the upper side to form end portions 48b, as shown in an enlarged view in FIG. 9b. The width h of the tip portion 48b in the height direction is slightly smaller than the width H of the horizontal portions 50b and 52b of the grooves 50 and 52 in the height direction. Further, the thickness of the tip portion 48b in the horizontal direction is equal to the thickness of the vertical portion 50 of the grooves 50, 52.
a, 52a, and this vertical portion 50
a, 52a can be freely passed through.

In the states shown in FIGS. 6 to 9, the lock bar 48 is located in a direction perpendicular to the direction of the mandrel 40 (the direction of the mating part of the half bodies 36a, 36b), and its tip 48b is located in the grooves 50, 62. Horizontal part 50b, 5
2b. At this time, the top surface of the lock bar 48 is in contact with the bottom surface of the bottom cover 36, and the half bodies 36a and 36b of the bottom cover 36 are supported from below so as to form horizontal surfaces. Therefore, the side circumferential surface of the bottom cover 36 is connected to the outer tube 34.
The inner circumferential surface of the bottom cover 36 engages with the outer circumferential surface of the lower end of the inner tube 32, so that the bottom of the filling portion is sealed. The spent nuclear fuel filled in the saw filling part is stored in the basket 14a.
It is held inside and will not fall from the bottom.

Note that a bottom cover half body 3 is provided on the outer peripheral surface of the lower end of the inner tube 32 and the inner peripheral surface slightly above the lower end of the outer tube 34.
Seal members 54, 56 are provided that come into contact when 6a, 36b are pushed up to be in a sealed state, allowing for tight sealing. This reliably prevents fine particles such as cutting debris adhering to the spent nuclear fuel cut body from falling downward from the gap between the bottom cover 36 and the inner tube 32 and outer tube 34.

In this state, the filling portion of the basket 14a is filled with spent nuclear fuel, inserted into the melting tube of the melting device, immersed in an acid solution, and used for melting the spent nuclear fuel.

After the melting is completed, the basket 14a is taken out from the melting tube, the bottom cover 36 is opened downward, and the pipe, which is the melting residue, is discharged from the filling section.

The downward opening of the bottom cover 36 will now be described. As mentioned above, the bottom cover 36 has half bodies 36a,
36b are connected by a hinge 38, so unless the lock bar 48 supports it from below, it will open downward due to gravity. That is, in the state shown in FIG. 7, the lock bar 48 is slightly rotated to move both end portions 48b of the lock bar from the horizontal portions 50b, 52b of the grooves 50, 52 to the vertical portions 50a, 52a, and downwardly move through the vertical portions 50a, 52a. move it to As the lock bar 48 moves downward, the support shaft 44 also moves downward. (As mentioned above, the lock bar 48 is attached to the lower end of the support shaft 44.) Then, when the distal end 48b of the lock bar emerges from the grooves 50, 52, the enlarged head 46 at the distal end of the support shaft 44 is attached to the mandrel. 40
The support shaft 44 and lock bar 48 are prevented from moving downward any further.

Next, the lock bar 48 is rotated approximately 90 degrees to match the extending direction of the mandrel 40 (the direction in which the halves 36a and 36b are aligned). Then, as shown in FIG. 10, the half bodies 36a, 36b are pushed downward by their own weight and the weight of the pipe filled above them and begin to open. As a result, the pipe held in the filling section is discharged from the basket 14a and stored in a drum or the like.

In addition, since the half bodies 36a and 36b rotate about the mandrel 40 in this way, the lower end of the inner tube 32 has a partially rounded corner so that it is at an equal radial distance from the mandrel 40. It is being

FIG. 11 is a diagram illustrating a device 57 for rotating the lock bar 48. FIG. 11a is a longitudinal sectional view.

The lock bar rotating device 57 is used because the pipe and basket 14a are radioactive and must be controlled remotely.

In the apparatus shown in FIG. 11, a clamping member 58 having an engagement groove 58a for the lock bar 48 shown in FIG. 12 on its upper surface is used. This clamping member is attached to the upper end of a rotatable vertical shaft 60, and a pulley 62 is provided at the bottom of this vertical shaft 60. A rotation drive device 64 is separately provided so that the output rotation shaft 63 is parallel to this vertical axis 60, and a belt 68 is stretched between it and a pulley 66 fixed to the output rotation shaft 63. , the vertical shaft 60 and the clamping member 58 are rotated by the rotation of the rotary drive device 64.

The operation for opening the bottom of the basket 14a and discharging the pipe using such a lock bar rotating device 57 will be described below.

First, the basket 14a is lifted up by a crane, carried to the location where the lock bar rotation device is installed, and the lock bar 4 is inserted into the engagement groove 58a of the holding member 58.
Gradually hang it so that 8 is engaged. After the lock bar 48 engages with the engagement groove 58a, the drive device 64
to rotate the lock bar 48 by 90 degrees. This causes the bottom cover 36 to open downward and the pipe to fall. A pipe storage drum 30 is placed in advance at a position below the vertical shaft 60, and this drum 3
Store the fallen pipe inside 0.

When sealing the bottom of the basket 14a that has been discharged, the lock bar 48 is engaged with the engagement groove of the holding member 58, and the lock bar 48 is inserted into the mandrel 40.
Rotate the holding member 58 until it is almost perpendicular to the groove 5, and insert both ends 48b of the lock bar 48 into the groove 5.
It is located at the input part of the vertical part 50a, 52a of 0,52. This rotation of the lock bar 48 lifts the half bodies 36a, 36b to a nearly horizontal state. Next, push the lock bar 48 upward (or lower the basket 14a downward), pass the tip 48b of the lock bar 48 through the vertical portions 50a, 52b of the grooves 50, 52, and then insert the drive device 64.
The lock bar 48 is rotated by a small angle by slightly driving the lock bar 48, and its tip 48b is aligned with the groove horizontal portions 50b, 52b.
to engage. As a result, the basket 14a
Since the bottom of the tank is closed, it can be refilled with spent nuclear fuel and used for melting. In addition, in FIG. 11, 69 is a roof-like cover member that covers the belt 68, and prevents the discharged pipe from coming into contact with the belt 68.

Since the above-mentioned embodiment is one example of the present invention, the present invention is not limited thereto and may be implemented in other embodiments.

An example of the structure of a melting device into which a basket according to the present invention is charged will be explained next with reference to FIGS. 13 to 16.

FIG. 13 is an overall configuration diagram of a dissolving device in which a sludge collecting section 70 for collecting sludge precipitated in a dissolving solution is provided at the bottom of each dissolving tube 12, and FIG.
It is an enlarged view of the part shown in the figure.

In FIG. 13, melting tubes 12 are erected on both sides of the slab 16, and are connected to the slab 16 via pipes 18, 22, and 24, respectively, so that liquid can flow therethrough. The bottom of the melting tube 12 is a small-diameter sludge collection part 70, and the transition part to this small-diameter part is a tapered part 1 whose diameter gradually decreases downward.
It has become 2b. A fluid blowing pipe 74 is connected to the bottom of the sludge collecting section 70, and the tapered section 12b
A sludge extraction pipe 76 is connected to the lower part of the sludge extraction pipe 76.

A basket 14a (not shown) consisting of an inner tube 32, an outer tube 34, etc. is inserted into the melting tube 12, and is hung on a tapered part 12c for hanging the basket formed at the lower part of the melting tube 12. has been done. A porous sludge receiver 72 is inserted below the basket 14a and is hooked onto the tapered portion 12b.

In the melting apparatus configured in this way, the acid solution in the slab 16 passes through the communication pipe 18 to the melting pipe 1.
2 and then ascends within the dissolution tube 12,
The spent nuclear fuel is melted and returned to the slab 16 via the connecting pipe 22 for circulation.

On the other hand, the sludge contained in the acid solution that has flowed into the dissolution tube 12 settles within the dissolution tube 12 . Among the sludge, those with large particle size are stored in the sludge receiver 72.
captured by. This sludge receiver 72 is inserted into the melting tube 12 as appropriate when the basket 14 is pulled out.
The sludge is taken outside and discharged. The fine sludge passes through the sludge receiver 72 and is deposited at the bottom of the melting tube 12. The deposited sludge is agitated by the fluid blown in by the fluid blowing pipe 74 and extracted from the sludge extraction pipe 76. For example, at predetermined time intervals, or whenever the amount of deposited sludge is detected by an appropriate detection means and the amount of deposited sludge reaches a predetermined amount, fluid is blown into the sludge collection section 70 from the fluid blowing pipe 74 to deposit the sludge. The sludge is stirred and discharged from the sludge discharge pipe 76 to the outside of the apparatus.

FIG. 15 shows a type of melting device in which a common sludge collecting section 78 is provided for each melting tube 12.

That is, the melting tubes 1 are erected on both sides of the slab 16.
The lower part of the pipe 2 communicates with a common sludge collection section 78 via a communication pipe 80. Also, slab 16
The bottom of the sludge collector 78 is sloped downward toward the center, and the lowermost part of the sludge collector 78 is connected to the sludge collector 78 via a connecting pipe 82 .

To explain the configuration of the sludge collecting section 78, the first
As shown in FIG. 6, mainly the lower narrow diameter portion 78a
and an upper large diameter portion 78b. A fluid blowing pipe 74 is connected to the bottom, and a sludge discharge pipe 76 is connected to a tapered part 78c that transitions from a narrow diameter part 78a to a large diameter part 78b.

A communication pipe 80 communicating with the lower part of the melting tube 12 is connected to an upper part of the large diameter part 78b, and a communication pipe 82 with the slab 16 is inserted from the top of the large diameter part 78b into the inside of the large diameter part 78b. It has reached close to 78c.

In the melting apparatus configured in this way, the acid solution in the slab 16 flows down the communication pipe 82 and enters the sludge collection section 78 . The liquid portion of the acid solution goes around the lower opening edge of the communication tube 82 in the collecting section 78, rises between the communication tube 82 and the large diameter portion 78b, and enters the dissolution tube 12 through the communication tube 80. Then, it ascends through the melting pipe 12, melts the spent nuclear fuel, and then returns to the slab 16 via the connecting pipe 22.
circulate.

On the other hand, the sludge contained in the acid solution introduced into the sludge collection section 78 from the communication pipe 80 settles within the sludge collection section 78 and is deposited in its narrow diameter section 78a. Therefore, at a predetermined time, the fluid blowing pipe 74
Fluid is blown into the narrow diameter portion 78a to stir the deposited sludge, and the sludge is discharged from the sludge discharge pipe 76 to the outside of the apparatus.

Note that FIGS. 13 to 16 are examples of melting devices that employ the basket of the present invention, and the basket of the present invention can also be used in melting devices with other structures.
Of course, it can be adopted.

[Effects of the Invention] As detailed above, according to the basket according to the present invention, it is possible to easily and quickly discharge the pipe containing the dissolution residue without reversing the basket. In addition, the basket has a double-tube structure, which allows the acid solution to be evenly distributed throughout the basket, resulting in uniform melting of the spent nuclear fuel and greatly reducing the time required for one cycle of melting. .

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a basket according to an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of a spent nuclear fuel melting device, and Figs. 3 and 4 explain conventional pipe discharge work. It is a schematic diagram. FIG. 5 is an enlarged sectional view of the upper part of the basket 14a, FIG. 6 is an enlarged perspective view (perspective view) of the lower part of the basket 14a, and FIG.
The figure is a sectional view taken along the line of FIG. 1, FIGS. 8 and 9 a are sectional views taken along the line of FIG. 10 is a plan sectional view illustrating the opening of the bottom cover 36, FIG. 10 is a perspective view of FIG. Fig. 13 and Fig. 15 are respectively an overall view of the melting device in which the basket of the present invention is immersed, Fig. 14 is an enlarged sectional view showing the part shown in Fig. 13, and Fig. 16 is an enlarged view of the part shown in Fig. 15. FIG. 12... Melting tube, 14, 14a... Basket, 30... Drum, 32... Inner tube, 34...
Outer tube, 36...bottom cover, 36a, 36b...half body, 38...hinge, 40...mandrel, 42...boss portion, 44...support shaft, 46...dish-shaped enlarged head, 48... Lock bar, 50, 52... Groove,
54, 56... Seal member, 58... Lock bar clamping member, 70, 78... Sludge collecting section.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A cylindrical basket that holds cut pieces of spent nuclear fuel inside and is charged vertically into a melting device, with a porous outer tube and a porous outer tube inside the basket. A porous inner tube inserted and installed coaxially, a disk-shaped bottom cover with a central hole that seals the bottom of the space between the outer tube and the inner tube, and a bottom cover of the bottom cover. a lock bar that is rotatable along the inner tube and about the center point of the inner tube, and the bottom cover is divided into two diametrically divided halves that can be opened downward by a pivot member. A basket for a spent nuclear fuel melting device, characterized in that the basket is connected to a spent nuclear fuel melting device. (2) The pivot member is a hinge, and the stem of the hinge crosses the lower end of the inner tube in the diametrical direction of the inner tube. 2. The spent nuclear fuel melting device basket according to claim 1, wherein a lock bar support shaft is pivotally supported, and the lock bar is fixed to the lower end of the support shaft. (3) The support shaft is pivotally supported to be vertically movable with respect to the mandrel, and the lock bar has a length approximately equal to the outer diameter of the outer tube, and has a length in a diametrical direction perpendicular to the mandrel. A basket for a spent nuclear fuel melting device according to claim 2, characterized in that grooves are formed at two locations on the lower edge of the outer tube, into which the tips of the lock bars are engaged. (4) Claims of a utility model patent characterized in that an annular sealing member is provided on the inner peripheral surface of the lower part of the outer tube and the outer peripheral surface of the lower part of the inner tube, with which the upper peripheral edge of the bottom cover comes into contact. A basket for a spent nuclear fuel melting device according to any one of Items 1 to 3.