JPH0658430B2 - Continuous spent fuel processing equipment - Google Patents

Description

The present invention relates to an apparatus for dissolving spent nuclear fuel with heated nitric acid and separating it from an insoluble cladding tube in a spent nuclear fuel reprocessing step. In particular, the present invention relates to an apparatus suitable for accurately removing a cladding tube from a fuel-loaded cage in order to continuously and highly efficiently dissolve a nuclear fuel having a high concentration of fissile material.

[Conventional technology]

Nuclear fuel that has released energy by the nuclear fission reaction in the nuclear reactor and consumed the fissile material and is no longer suitable for use is generally called spent nuclear fuel. Reprocessing is a process for recovering and reusing the fissile material and nuclear fuel material contained in the spent nuclear fuel.

The reprocessing process consists of a wider variety of unit processes. In the Purex process, in its first step, the fuel rods are sheared into pieces, followed by dissolution of the contents of the nuclear fuel material in nitric acid. Since the cladding of this fuel piece is generally a zirconium alloy or stainless steel, it does not dissolve in nitric acid and can be separated after the nuclear fuel material has dissolved.

By the way, as a device for melting spent nuclear fuel,
A so-called batch method in which the required amount of nitric acid is added to a corrosion-resistant container loaded with nuclear fuel to complete the fuel dissolution and then the dissolution treatment liquid is taken out, and a continuous method in which the dissolution treatment liquid is taken out while loading the nuclear fuel and nitric acid into the container , And there is a semi-continuous method that has an eclectic character of both. In general, the continuous method has a higher efficiency than the batch method, but there is a problem in taking out insoluble matter such as a covering tube, and as a solution to this problem, an apparatus for continuously treating the processed matter described in JP-A-56-94297. Was provided. In this device, a fuel-loaded cage supported by a peripheral path is rotatively moved in the vertical direction, and the cladding tube is dropped by gravity from the fuel-loaded cage located above the center of rotation to be discarded.

[Problems to be solved by the invention]

However, since this device has a vertically long structure, it is disadvantageous in terms of earthquake resistance, and there is a concern that the structure is complicated and clogging in the path by the cladding tube occurs. A continuous dissolution process characterized in that a container loaded with fuel pieces is immersed in a dissolution treatment liquid in a dissolution tank held horizontally to avoid clogging by the cladding pipe, and the cladding pipe is taken out of the container after the dissolution. Research and development of the device is underway. For example, the direct array continuous melting apparatus described in Japanese Patent Laid-Open No. 61-99893 is a continuous melting processing apparatus of a system in which fuel shear fragments are supplied by a conveyor into a plurality of melting vessels arranged in a straight line. As typified by this known example, it is necessary to accurately take out the coating tube from the melting container by using a device equipped with this drive mechanism.

However, the dissolution treatment equipment has high concentration of radioactive materials and high temperature
Since the drive unit needs to be regularly maintained in order to handle a high concentration of acid, the maintenance is extremely difficult because it is performed in an atmosphere with high radioactivity. Therefore, there is a demand for a mechanism that is easy to maintain and requires less maintenance, that is, a mechanism that is simple and has a small number of drive units. Further, when the covering tube is taken out, there is a possibility that radioactive substances may come out of the device and contamination may spread, and a mechanism that can maintain the airtightness of the device in a compact shape is desired.

An object of the present invention is to provide an apparatus for continuously dissolving spent nuclear fuel, which has a simple structure and can easily discharge all of the cladding tubes in a car loaded with fuel to the outside of the car to reduce the frequency of maintenance.

[Means for Solving Problems] A feature of the present invention is that a dissolution tank filled with a dissolution treatment liquid that dissolves spent nuclear fuel, and a dissolution tank that projects above the dissolution tank and is provided in the dissolution tank are used. A fuel-carrying car elevating part forming an ascending / descending path in which a fuel-carrying car having a nuclear fuel loaded therein moves up and down, and gripping parts provided on opposite side walls of the fuel-carrying car below the center of gravity of the fuel-carrying car. And a fuel-carrying car lifting device that is provided in the fuel-carrying car lifting / lowering unit and that vertically moves the fuel-carrying car gripped by the gripping device in the lifting path, and On the inner surface of the fuel-carrying car elevating part, which is connected to the side wall of the loading car elevating part and has a cross section larger than the cross-section of the fuel loading car, and which faces the clad tube evacuation part. The clad pipe outlet is provided so as not to interfere with the vertical movement of the gripping device, and the fuel loading car is centered around the gripping part when the fuel loading car comes into contact with the upper end of the fuel loading car that is raised by the fuel loading car elevating device. It is provided with a projecting portion which is inclined to the part side.

[Action]

The position of the center of gravity of the fuel-carrying car that rises in the fuel-carrying car lifting / lowering unit by the fuel-carrying car lifting / lowering device is above the position of the center of rotation gripped by the gripping device provided in the fuel-loading car lifting / lowering device, and the coating Since the projecting part is provided on the inner surface of the fuel loading car elevating part facing the pipe outlet, the upper end of the fuel loading car rising in the fuel loading car elevating part comes into contact with the projecting part, so that the fuel loading Due to the action of the center of gravity of the car and the protrusion, the fuel-loaded car inclines toward the cladding tube outlet side. When the grip of the fuel loading car is raised by the fuel loading car lifting device in such a state, the rising of the gripping device is not hindered by the protrusion and the upper end of the fuel loading car is inserted into the cladding tube outlet. Eventually, the upper end of the fuel-loaded car faces downward. For this reason,
All of the cladding in the fuel-loaded car is easily discharged into the cladding outlet.

As described above, according to the present invention, the action of the center of gravity and the protrusion of the fuel-loaded car causes the fuel-loaded car to incline toward the cladding tube outlet side, and the protrusion does not hinder the lifting of the gripping device. All of the cladding tubes of can be easily discharged, and the mechanism for discharging the cladding becomes significantly simpler,
The frequency of maintenance and inspection is reduced.

〔Example〕

 Examples of the present invention will be described below.

FIG. 1 is a vertical sectional view of a continuous dissolution treatment apparatus according to an embodiment of the present invention. In Figure 1, circular melting tank 1
Inside, the high-temperature, high-acid-concentration dissolution treatment solution 3 is contained, a plurality of fuel-loaded cages 2 are arranged in the circumferential direction, and the lower portion of the fuel-loading cage 2 is immersed in the dissolution-treatment fluid 3. There is. The fuel loading cage 2 is loaded with fuel shear fragments, which dissolves only the fuel in the dissolution treatment liquid 3 and leaves the insoluble fuel cladding tube in the fuel loading cage 2. The structure of the fuel-loaded car 2 is shown in FIG. Melting tank
The upper part of 1 is kept airtight by the cover 8. The dissolution treatment liquid 3 is supplied into the dissolution tank 1 through the supply port 29 and discharged through the discharge port 30. The fuel loading car gripping device 5 (see FIG. 6) is connected to the fuel loading car lifting / lowering device 6 in a suspended state, and the fuel loading car lifting / lowering device 6 is held by the cover 8 so that the fuel loading car gripping device 5 is It is installed inside the cover 8. That is, the covering tube take-out portion 9 is covered with the cover 8 and the airtightness of the entire dissolution treatment apparatus can be maintained. The cladding pipe outlet 4 is connected to the cladding pipe outlet 9. In order to take out the cladding tube in the fuel-loaded cage 2, first, the fuel-loaded cage holding device 5 grasps the fuel-loaded cage 2,
Suspended by the fuel-carrying basket lifting device 6, fuel-carrying car 2
Is collapsed into the cladding tube outlet 4 by the gravity applied to itself, and the inside cladding tube is taken out. When it falls to the opposite side of the cladding tube outlet 4, the fuel loading basket 2 is pushed back by the guide plate 7 and always falls into the cladding tube outlet 4.

Next, the method of taking out the fuel cladding tube will be described in detail with reference to FIG. FIG. 2 (a) is a sectional view showing an operation at a position where the fuel-loaded car 2 is gripped. The fuel-loading cage which is placed in the melting tank 1 after the fuel-loading cage elevator 6 descends.
A position closer to the bottom than the position of the center of gravity of 2 is gripped by the fuel loading car gripping device 5. Next, the fuel-carrying car lifting device 6 suspends the fuel-carrying car 2 and carries it to the cladding pipe unloading section 9. Fig. 2
(b) is a cross-sectional view showing an operation in which the fuel-loaded cage 2 falls into the cladding tube outlet 4. Grasping part 1 of fuel loading basket gripping device 5
0 indicates a mechanism in which the fuel-loaded cage 2 is rotatable, so the balance A of the fuel-loaded cage 2 causes the arrow A
The center of gravity position 11 moves as shown in. When the fuel-loaded cage 2 is further lifted upward as indicated by arrow B, the upper portion of the fuel-loaded cage is tilted into the cladding tube outlet 4 and the cladding tube being taken out is taken out, as indicated by arrow C.

Figure 3 shows the outlet of the cladding tube depending on the balance of the fuel-loaded cage 2.
FIG. 9 is a cross-sectional view showing an operation when the device is tilted to the side opposite to that of 4 or is not tilted to either side. When the fuel loading basket 2 is lifted by the fuel loading basket lifting device 6, the upper end of the fuel loading basket 2 contacts the guide plate 7 as shown by the broken line in FIG. 3 (a). When it is further raised as indicated by arrow D, the upper end of the fuel-loaded car 2 moves along the shape of the guide plate 7.
When the fuel-loaded cage 2 is tilted as shown by the broken line in FIG. 3 (b), the center of gravity 11 is rotated by gravity as shown by arrow E, and the upper portion of the fuel-loaded cage 2 is located inside the cladding pipe outlet 4. Collapse to. After that, the cladding tube can be taken out by the same operation as in FIG. 2 (b).

According to the present embodiment, the center of gravity of the fuel-loaded car and the action of the protrusions cause the fuel-loaded car to incline toward the cladding tube outlet side, and the protrusion does not hinder the lifting of the gripping device. Can easily discharge all of the cladding tube of
The mechanism for evacuating the cladding is significantly simplified (fewer drive parts needed to remove the cladding) and the frequency of maintenance is reduced. This leads to a significant reduction in the risk of maintenance personnel being exposed to radiation. Further, since the drive unit can be replaced by removing the cover 8 with a simple structure, maintenance is easy. The shape of the guide plate is
Any structure may be used as long as the fuel loading basket 2 is pushed back to the cladding pipe outlet 4 side. Further, instead of this guide plate, a method may be used in which a pushing mechanism is added to the fuel-loaded car 2 by using a drive mechanism.

FIG. 4 is a sectional view showing an example of the push-back device 12.
In this example, the push-back section 13 is operated by the push-back drive device 14 as indicated by arrow F, whereby the fuel-loaded car 2 is tilted toward the cladding pipe outlet 4 side.

FIG. 5 is a cross-sectional view showing an embodiment of a portion for gripping the fuel-loaded car 2. A gripping member (15) is joined to the side surface of the fuel-loaded car (2) closer to the bottom than the center of gravity, and a circular gripping hole (16) is formed on it. It is assumed that the gripping holes 16 are provided at one place on each side surface, and the centers of the two gripping holes 16 are located at the same height. That is, the centers of the grip holes 16 on both sides are arranged on the straight line ll 'in FIG.

FIG. 6 is a cross-sectional view showing an embodiment of the structure of the grip portion of the fuel loading car grip device 5. A conical grip claw 18 is provided at the tip of the grip arm 17, and the grip arm 17 opens and closes as shown by an arrow G to grip the fuel-loaded car 2. When gripped, the grip claw 18 enters the grip hole 16, but by allowing a slight margin, the fuel loading basket 2 becomes rotatable around the grip. If the grip hole 16 has a taper as shown in the drawing, the grip claw 18 can be easily inserted, and strength enough to withstand rotation can be secured. Since the position of the grip hole 16 may be closer to the bottom than the position of the center of gravity of the fuel loaded car 2, the length of the grip arm 17 can be shortened by making the upper part of the fuel loaded car 2 heavier. The opening / closing operation of the gripping arm 17 is performed by transmitting the rotation of the shaft 21 of the actuator 22 to the worm 19 and the worm wheel 20 in this example.

In order to move the fuel-loading car lifting device 6 to the position of the fuel-loading car 2, a method of moving the fuel-loading car 2 or a method of moving the fuel-loading car lifting device 6 or both of them. Can be partially moved.

One embodiment of the third method will be described with reference to FIG. Fig. 7 shows the fuel loading cage 2 in the continuous melting treatment equipment.
Shows the moving state of. The fuel-loaded car 2 in the melting tank 1 is held by an annular suspension plate 23, and sequentially rotates in one direction at regular intervals. The rotation is performed by the hanging plate rotation drive device 24. The dissolution tank 1 has a partition wall 26, and nitric acid is supplied from a supply port 29 installed in a space for one fuel-loading basket between the dissolution tank 1 and the end plate 27, and an exhaust gas installed on the opposite side of the partition wall 26 is discharged. The dissolution treatment liquid 3 in which the fuel is dissolved is discharged from the outlet 30. In this device, continuous melting is possible by moving the fuel-loaded cage 2 as indicated by the arrow. The fuel loading basket 2 is taken out at the H portion in the figure and is conveyed to the I portion. Here, the cladding tube is taken out and again put in the melting tank 1 at the J portion, and the fuel shear fragments are newly loaded. In the figure, the dissolution treatment liquid 3 is heated by the jacket bottom 25.

An example of the continuous dissolution treatment apparatus of the present invention in the continuous dissolution system of FIG. 7 will be described with reference to FIG. The melting tank 1 is completely covered with the cover 8 and airtightness is maintained. The H, I, and J portions in FIG. 7 are also sealed by the cover 8 and the covering pipe outlet 4 is connected. The fuel-carrying car lifting / lowering device 6 is attached to the cover 8 while the fuel-carrying car gripping device 5 is suspended, and is moved by the horizontal moving device 28 on the cover 8 as indicated by an arrow K. As a result, it becomes possible to move the fuel-loaded cage 2 and take out the cladding tube.

According to the embodiment of the present invention, the number of drive mechanisms required for moving the fuel-loaded cage, which is indispensable for realizing the take-out of the cladding tube and the continuous melting, is small, and the frequency of maintenance required for the drive unit is low. Further, the drive unit is attached to the cover 8 on the melting tank 1, and by partially removing the cover 8, it can be easily replaced, and maintenance can be performed by remote operation of a manipulator or the like. Radiation exposure of maintenance workers can be reduced. Furthermore, since it can be realized in a compact shape, the space for the dissolution processing equipment in the spent nuclear fuel reprocessing facility can be small, and the whole can be covered with a cover to maintain the airtightness of the dissolution processing apparatus. Can prevent the spread of radioactive contamination.

〔The invention's effect〕

According to the present invention, the action of the center of gravity of the fuel-loaded car and the projecting portion causes the fuel-loading car to incline toward the cladding tube take-out port side, and the protrusion does not hinder the lifting of the gripping device. Can be easily discharged,
The mechanism for draining the cladding is significantly simplified and the frequency of maintenance is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an apparatus for continuously dissolving spent nuclear fuel according to an embodiment of the present invention, FIGS. 2 to 4 are cross-sectional views of a cladding tube extraction portion in the apparatus of FIG. 1, and FIG. FIG. 6 is a perspective view of a fuel-loaded car, FIG. 6 is a partial cross-sectional view showing an example of a fuel-loaded car gripping device, FIG. 7 is an explanatory view of movement of a fuel-loaded car in a continuous melting treatment device, and FIG. 8 is FIG. FIG. 3 is a perspective view of a continuous dissolution treatment apparatus showing an embodiment of the present invention during the operation of FIG. 1 …… Solving tank, 2 …… Fuel-loaded basket, 3 …… Dissolution processing liquid, 4
…… Cladding pipe outlet, 5 …… Fuel loading basket gripping device, 6 ……
Fuel loading basket lifting device, 7 …… guide plate, 8 …… cover,
9 …… Clad tube outlet, 10 …… Grip, 11 …… Center of gravity, 1
2 ... Push back device, 13 ... Push back part, 14 ... Push back drive device, 15 ... Grip member, 16 ... Grip hole, 17 ... Grip arm, 18 ... Grip tab, 23 ... Suspension plate, 24 …… Suspension plate rotation drive device, 25 …… Jacket bottom, 26 …… Differential wall, 27 …… Cleaving plate, 28 …… Horizontal moving device, 29 …… Supply port, 30 …… Discharge port.

Claims (1)

[Claims] 1. A dissolution tank filled with a dissolution treatment liquid for dissolving spent nuclear fuel, and a fuel-loaded basket provided in the dissolution tank so as to project above the dissolution tank and having spent nuclear fuel loaded therein. A fuel-carrying car elevating / lowering unit that forms an up-and-down moving path, and a gripping device that rotatably grips each gripping unit provided on opposite side walls of the fuel-carrying car below the center of gravity of the fuel-carrying car. A fuel loading car elevating device which is provided in the fuel loading car elevating part and moves up and down the fuel loading car gripped by the gripping device in the elevating passage; and the fuel connected to the side wall of the fuel loading car elevating part. A cladding pipe outlet having a cross-section larger than the transverse cross section of the loading basket and an inner surface of the fuel-carrying car elevating unit that faces the cladding pipe outlet, and inhibits vertical movement of the gripping device. And a protrusion for inclining the fuel loading car toward the cladding pipe outlet when the upper end of the fuel loading car is raised by the fuel loading car lifting device. Continuous melting and processing equipment for nuclear fuel.