JPH0425678Y2 - - 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.

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.

Note that 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, and the oxygen gas blown into the melting tube 12 from the blowing pipe 26 passes through the communication pipe 24 and reaches the slab 16.
Go inside.

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 solution in which the liquid can come into contact with the nuclear fuel. special request
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, and a simple pipe installed at the bottom of the basket. A discharge tubular member 50 and a bottom member 42 that can be opened and closed with a simple operation and do not open during melting operations.
An opening/closing mechanism is provided, which allows the pipe to be discharged without having to reverse the basket.

That is, as shown in the drawings, the basket 14a of the present invention includes a porous outer tube 34 having a bottom member 42 having a center hole 44 at its lower end, and a porous outer tube 34 that is coaxially disposed within the outer tube 34 and whose lower end is located at the bottom. The inner tube 3 is configured to be located a predetermined distance above the material 42.
2, and a discharge tubular member 50 provided at the bottom of the basket 14a.

This discharge tubular member 50 has a cylindrical upper half 5
2. A lower half 56 consisting of a plurality of vertical bars hanging from the lower end of the cylindrical upper half 52; a ring-shaped bottom seat 58 fixed to the lower end of the lower half; the upper half 52 and the lower half 56; It consists of an engaging member (hereinafter abbreviated as an engaging member) 60 that engages the peripheral edge of the bottom member center hole 44 and is engaged with the outer periphery of the boundary of the bottom member. The cylindrical upper half 52 is loosely fitted to the lower end of the inner tube 32, and the lower half 56 is loosely passed through the bottom member center hole 44.

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.

[Function] The basket 14a of the present invention has a porous inner tube 3.
2 and an outer tube 34, and the spent nuclear fuel is cut into short pieces and charged between the inner tube 32 and the outer tube 34. Furthermore, although the discharge tubular member 50 is movable in the vertical direction, its engagement member 60 is pressed against the upper surface of the bottom member 42 due to its own weight. Therefore, under normal conditions in which the discharge tubular member 50 is not pushed up, the spent nuclear fuel flows into the inner pipe 32.
and the outer tube 34.

On the other hand, as mentioned above, the bottom member 42 has a hole 4 in the center.
4, and the lower half 5 of the discharge tubular member 50.
6 is in play. Further, at the lower end of the lower half portion 56,
A bottom seat 58 for engagement with the push-up jig 62 is provided. As shown in FIG. 10, when the ejection tubular member 50 is pushed up using the push-up jig 62, a gap is created between the engaging member 60 and the bottom member 42, and the pipe falls through this gap and is ejected. be done.

Note that the basket has a double tube structure with an inner tube 32 and an outer tube 34, and when the basket of the present invention is loaded into a melting device and used for melting work, the melting liquid does not bypass the basket. , through the inner pipe 32, and uniformly circulates inside the basket 14a, so that the dissolution rate of the spent nuclear fuel inside the basket 14a is equalized in each portion. Therefore,
There is no dissolution unevenness, and the time required per dissolution cycle is shortened.

[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 charged into the melting tube 12, this enlarged diameter portion 36
It comes into contact with the inner wall surface and supports the basket 14a in an upright position.

The upper end of the inner tube 32 is fixed to the inner wall surface of the outer tube 34 via three ribs 38 fixedly provided so as to extend in the tube axis direction. Further, as shown in an enlarged view in FIGS. 6 and 7, the lower end of the inner tube 32 is connected to the outer tube 3.
The lower end of the inner tube 32 is fixed to the outer tube 34 via three ribs 40 extending in the tube axis direction.

On the other hand, a ring-shaped bottom member 4 is provided at the lower end of the outer tube 34.
2 is provided. This bottom member 42 has a circular center hole 44 in the center, and the center hole 44
It has a slope 46 that slopes downward toward.
(As will be described later, this slope 46 is for smoothing the discharge of dissolved residue from the pipe.) In the figure, 50 is a discharge tubular member. As shown in FIG. 9, the discharge tubular member 50 includes a cylindrical upper half 52 and a plurality of (three in this embodiment) vertically extending from the lower end of the cylindrical upper half 52. Vertical bar 54
It is mainly composed of a lower half 56 consisting of.

A ring-shaped bottom seat 58 is fixed to the lower end of the lower half 56. The upper surface of the bottom seat 58 is a slope that slopes downward in the radial direction, and the lower surface is horizontal. The bottom seat 58 serves to engage with a cylindrical portion 64 of a push-up jig 62, which will be described later, and at the same time serves as a weight, increasing the force of pushing down the entire discharge tubular member 50.

In this embodiment, the cylindrical upper half 52 is a porous body similar to the inner tube 32, and the solution can freely flow through the tube wall. Moreover, this cylindrical upper half 52 is connected to the inner tube 3.
The inner tube 32 has an outer diameter slightly smaller than the inner diameter of the inner tube 32.
can be freely inserted through the bottom of the

At the boundary between the cylindrical upper half 52 and the lower half 56 (in this embodiment, the lowest end of the cylindrical upper half 52),
A ring-shaped engagement member 60 is provided, and engages with the peripheral edge of the center hole 44 of the bottom member 42 to lock the discharge tubular member 50 to the bottom member 42 . (That is, as shown in the figure, the outer diameter of the engaging member 60 is
The hole diameter is set larger than the hole diameter of No.4. ) This engaging member 60 has a lower surface that is connected to the bottom member 4.
The slope has the same slope as the slope 46 of No. 2, and tight sealing is possible by contacting the top surface of the bottom member 42. In this embodiment, both the bottom member 42 and the engaging member 60 are made of metal, and are configured to provide a more reliable seal by means of a metal touch seal.

In the present invention, the discharge tubular member 50 is pushed up and moved up and down by a central cylindrical portion 64 of a push-up jig 62, which will be described next.

As shown in FIGS. 10 and 12, this push-up jig 62 has three legs 66 that are fixed to the lower part of the outer peripheral surface of the cylindrical portion 64 and extend in the radial direction and are curved in a waveform. This leg portion 66 is suspended so as to straddle the upper edge of the drum 30 that accommodates the pipe discharged from the basket 14a.

The diameter of this cylindrical portion 64 is large enough for the ring-shaped bottom seat 58 to be placed on its upper end surface.

The operation of the basket of this embodiment will be described below.

This basket 14a has an inner tube 32 and an outer tube 34.
A cut body of spent nuclear fuel is inserted between the two and inserted into the melting tube 12 to be used for melting.
In this state, the discharge tubular member 50 is lowered by its own weight, and the engagement member 60
The lower surface of the fuel cell is seated on a slope 46 at the periphery of the center hole 44, so that the spent nuclear fuel inside will not fall out.

After the melting is completed, the basket 14a with the pipe remaining inside is lifted up by a crane and carried above the drum can 30 on which the pushing jig 62 is installed. Next, the push-up jig 62 is suspended so that the bottom seat 58 is placed on the cylindrical portion 64.

Then, the bottom seat 58 is pushed up against the cylindrical portion 64, and the discharge tubular member 50 is stopped from descending and rises relative to the inner tube 32 and outer tube 34. As the discharge tubular member 50 starts to rise, the engagement member 6
0 and the bottom member 42, and the pipe held between the inner tube 32 and the outer tube 34 falls between the upper parts of the vertical bars 54 in this gap and through the center hole 44. Begin to. Note that since the top surface of the bottom seat 58 is inclined, the pipe is prevented from resting on the top surface of the bottom seat 58 when the fall starts.

Then, the discharge tubular member 50 further rises,
When the upper surface of the engaging member 60 comes into contact with the lower end surface of the inner tube 32, the evacuation tubular member 50 stops rising, resulting in the state shown in FIG. 10. In this state, the pipe continues to be discharged. At this time, the slope 46 of the bottom part 42 smoothes the fall of the pipe, prevents the pipe from falling and remaining on the top surface of the bottom member 42, and enables smoother pipe discharge.

Note that the discharged pipe is accommodated in a drum can 30 disposed below.

Moreover, the above-mentioned discharge operation is performed by remote control.

When the basket 14a is lifted up after the discharge operation is completed, the discharge tubular member is lowered, and the engaging member 60 of the discharge tubular member comes into contact with the bottom member 42, thereby sealing the lower end of the basket 14a. Then, a cut piece of spent nuclear fuel is placed again between the inner tube 32 and the outer tube 34, and inserted into the melting tube to perform the melting operation.

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 pipes 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 liquid blown from the fluid blowing pipe 74 and is 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 collecting 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 portions of the two communicate with a common sludge collecting section 78 via a communication pipe 80. Also, slab 16
The bottom part of the sludge collecting part 78 is inclined downwardly toward the central part, and the lowest part thereof communicates with the sludge collecting part 78 via a connecting pipe 82. To explain, 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 within 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. Figures 5 and 6
The figures are enlarged sectional views of the upper and lower parts of the basket shown in Fig. 1, respectively, and Figs.
9 is a perspective view of the discharge tubular member, FIG. 10 is a sectional view illustrating the opening and closing action of the lower part of the basket, and FIG.
12 is a sectional view taken along the line -2 in the figure, and FIG. 12 is a perspective view of the inner pipe pushing jig. 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...cap, 40...rib, 42...
... Bottom member, 44 ... Center hole, 46 ... Slope, 50
...Discharge tubular member, 52... Upper half, 54...
Vertical bar, 56...lower half, 58...bottom seat, 62...
Push-up jig.

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 bottom member having a center hole at the lower end. a porous outer tube provided within the outer tube; a porous inner tube installed coaxially within the outer tube such that its lower end is located a predetermined distance above the bottom member; and a cylindrical upper half. , a lower half consisting of a plurality of vertical bars hanging from the lower end of the cylindrical upper half, a ring-shaped base fixed to the lower end of the lower half, and a boundary between the upper half and the lower half. a member formed on the outer periphery of the bottom member for engaging with the peripheral edge of the center hole of the bottom member;
The cylindrical upper half part is loosely fitted to the lower end of the inner tube, and the lower half part includes a discharge tubular member inserted through the center hole of the bottom member. A basket of nuclear fuel melting equipment. (2) The basket for a spent nuclear fuel melting device according to claim 1, wherein the upper surface of the bottom member is a slope that slopes downward toward the center hole. (3) The lower surface of the engaging member provided on the discharge tubular member is a slope having the same slope as the bottom member at the lower end of the outer tube. Basket of spent nuclear fuel melting equipment described. (4) The upper surface of the bottom seat provided at the lower end of the discharge tubular member is a slope that slopes downward in the radial direction. A basket for the spent nuclear fuel melting device according to item 1.