JPS63315994A - Continuous dissolving treatment device for spent nuclear fuel - Google Patents

Abstract

PURPOSE:To exactly take cladding pipes out of a fuel loading cage in a limited space by constituting a loading cage gripper of a fuel loading cage lifting device in such a manner that the loading cage is automatically turned down at the time of lifting the loading cage. CONSTITUTION:A cladding pipe taking-out section 9 is provided to the upper part of a circular dissolving vessel 1 which consists of a dissolution treating liquid 3, a feed port 29 and a discharge port 30 and is disposed with the plural fuel loading cages in the circumferential direction thereof. A cover 8 is provided to the upper part of this dissolving vessel 1 and the cladding pipe taking-out section 9 to maintain airtightness. A cladding pip taking-out port 4 is provided to part thereof. The fuel loading cage gripper 5 is coupled to the lifting device 6 and the lower part of the loading cage 2 is freely turnably gripped by the gripper 5. The loading cage 2 is turned down into the cladding pipe taking-out port 4 by a guide plate 7 and its own weight of the cage 2 when the gripped cage 2 is hoisted. The cladding pipes in the cage 2 is thus surely taken out.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an apparatus for dissolving spent nuclear fuel with heated nitric acid and separating it from insoluble cladding in a spent nuclear fuel reprocessing process. In particular, the present invention relates to an apparatus suitable for accurately removing a cladding tube from a fuel loading tank in order to continuously and efficiently melt nuclear fuel with a high concentration of fissile material.

[Conventional technology]

Nuclear fuel that releases energy through a nuclear fission reaction in a nuclear reactor and consumes fissile material and is no longer suitable for use is generally referred to as spent nuclear fuel. Reprocessing is the process of recovering and reusing the fissile material and nuclear fuel material contained in this spent nuclear fuel.

The reprocessing process further consists of a wide variety of unit processes. In the Picolex process, in the first step, the fuel rods are sheared into small pieces and the nuclear fuel material inside is subsequently dissolved in nitric acid. The cladding tube of this fuel piece is generally made of zirconium alloy or stainless steel, so it does not dissolve in nitric acid and can be separated after the nuclear fuel material is completely dissolved.

By the way, as a device for melting spent nuclear fuel,
There is a so-called batch method in which the necessary amount of nitric acid is added into a corrosion-resistant container loaded with nuclear fuel to complete 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 nuclear fuel and nitric acid into the container. , as well as semi-continuous systems that have a compromise between the two. In general, the continuous type is more efficient than the batch type, but there is a problem in removing undissolved materials such as cladding tubes.
An apparatus for continuously processing the processed material described in the above publication was provided. This device rotated the fuel loading baskets, which were supported on the same level, in the vertical direction, and dropped the cladding tubes by gravity from the fuel loading basket located above the center of rotation, and dumped them.

[Problem that the invention seeks to solve]

However, since this device has a vertically elongated structure, it is disadvantageous in terms of earthquake resistance, and since the structure is complex, there is a concern that clogging of the path by the cladding tube may occur. A continuous melting process characterized by immersing a container loaded with fuel pieces in a melting solution in a melting tank held horizontally to avoid clogging of the cladding tube, and then removing the cladding tube from the container after melting. Research and development of the device is underway. For example, a straight-array continuous melting apparatus described in Japanese Patent Application Laid-Open No. 61-99893 is a continuous melting processing apparatus in which fuel sheared pieces are fed by a conveyor into a plurality of melting containers arranged in a straight line. As typified by this known example, it is necessary to accurately take out the cladding tube from the melting container using a device equipped with some kind of drive mechanism.

However, the dissolution treatment equipment handles high concentrations of radioactive materials and high temperatures.
Since the drive unit handles highly concentrated acids, regular maintenance is required, but this maintenance is extremely difficult because it is performed in an atmosphere with high radioactivity. Therefore, there is a desire for a mechanism that is easy to maintain and requires less frequent maintenance, that is, a mechanism that is simple and has fewer driving parts. Furthermore, when taking out the cladding tube, there is a risk that radioactive substances may come out of the device and spread contamination, so a mechanism that is compact and can maintain airtightness of the device is desired.

It is an object of the present invention to provide a mechanism that requires less maintenance, is easy to maintain, has a compact shape that is easy to maintain airtightness to prevent the spread of contamination when removing the cladding, and is capable of accurately removing the cladding. The purpose of the present invention is to provide a continuous melting treatment apparatus having the following features.

[Means for solving problems]

The above purposes are (a) a circular dissolution tank filled with a dissolution treatment liquid and for dissolving the spent nuclear fuel; (b) for loading spent nuclear fuel and immersing it in the dissolution tank; (c) a fuel loading basket lifting device equipped with a fuel loading basket gripping device for taking the fuel loading basket in and out of the melting tank; (d) Undissolved fuel cladding outlet, (e)
In a continuous spent nuclear fuel dissolution processing device that includes a dissolution treatment liquid supply port and (f) a discharge port, a fuel loading basket gripping device provided in the fuel loading basket lifting device is configured to dispose of the spent nuclear fuel after the spent nuclear fuel dissolution processing is completed. When the fuel loading basket is raised, the fuel loading basket is automatically moved This is achieved by inverting the tube so that the upper opening faces downward so that the internal undissolved fuel cladding tube can be discharged to the outlet of the undissolved fuel cladding tube.

According to the present invention, the fuel loading basket has a cladding tube inside, and the center of gravity is located higher than the part where the fuel loading basket is gripped, that is, the one gripping point, and the fuel loading basket is tilted by the gravity applied to itself. It turns out. At this time, the gripping portion has a mechanism that allows the fuel loading basket to rotate freely around the gripping point. In addition, in order to ensure that the fuel loading basket is always tilted to the side where the cladding tube extraction port exists, a means for pushing back the fuel loading basket when the fuel loading basket is tilted to the opposite side of the cladding tube extraction port, or
A guide plate with a pressing structure is installed.

[Effect]

According to the device of the present invention, when the fuel-loaded basket is lifted from the melting tank after the melting process is completed, the weight of the fuel-loaded basket is designed in consideration of the weight of the basket itself and the undissolved fuel cladding tube. Since the center of gravity is configured to be higher than the gripping point, the fuel basket rotates and tilts around the gripping point, so that the opening at the top of the fuel loading basket faces downward. Therefore, if the cladding pipe outlet is placed at the top of the lifted position,
A tilted fuel container falls into its cladding tube outlet through the opening at the top, and by lifting the fuel loading basket upward, the fuel loaded container falls into the cladding tube outlet, releasing the cladding tube inside. , this can be retrieved. In this way, the cladding tube can be taken out accurately with a simple and small number of drive parts, ie, a lifting drive part and one gripping drive part.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 is a vertical sectional view of a continuous melting treatment apparatus according to an embodiment of the present invention. In FIG. 1, a circular melting tank 1 contains a high temperature, highly acidic, 1 degree melting treatment liquid 3, and a plurality of fuel loading containers 2 are arranged in the circumferential direction. The lower part of is immersed in the dissolving treatment liquid 3. The fuel loading shell 2 is loaded with fuel shear pieces, and only the fuel is dissolved in the dissolution treatment liquid 3, so that an insoluble fuel cladding tube remains in the fuel loading shell 2.

The upper part of the dissolution tank 1 is kept airtight by a cover 8. The dissolution treatment liquid 3 is supplied into the dissolution tank 1 from the supply port 29 and discharged from the discharge port 30. The fuel loading basket gripping device 5 lifts and lowers the fuel loading basket'! The fuel loading car lifting device 6 is attached to the cover 8 in a suspended state.
The fuel loading basket gripping device 5 is installed so as to be placed inside the cover 8.

That is, the cladding tube removal section 9 is covered with the cover 8, and the airtightness of the entire melting treatment apparatus can be maintained. Cladding tube outlet 4
is connected to the cladding tube removal section 9. In order to take out the cladding tube inside the fuel loading basket 2, the fuel loading basket gripping device 5 first grasps the fuel loading basket 2, lifts it up with the fuel loading basket lifting device 6, and the fuel loading basket 2 is coated by the gravity applied to the white. It falls into the tube outlet 4 and the cladding tube inside is taken out. If it falls to the side opposite to the cladding tube outlet 4, the guide plate 7 pushes back the fuel loading port 2 so that it always falls into the cladding tube outlet 4.

Next, the method for removing the fuel cladding tube will be explained in detail with reference to FIG. FIG. 2(,) is a sectional view showing the operation at a position where the fuel loading lever 2 is gripped.

The fuel loading basket lifting device 6 descends, and the fuel loading basket gripping device 5 grips the fuel loading basket 2 disposed in the melting tank 1 at a position closer to the bottom than the center of gravity. Next, the fuel loading car lift device 6 lifts up the fuel loaded basket 2 and transports it to the cladding pipe removal section 9. FIG. 2(b) is a sectional view showing the operation of the fuel loading cap 2 falling into the cladding tube outlet 4. The gripping part 10 of the fuel loading basket gripping device 5 is configured to hold a fuel loading basket 2.
Is it times? Since it has a mechanism that allows it to move freely, depending on the balance between fuel loading and 2, the center of gravity position 1 can be adjusted as shown by the arrow.
1 moves. Further, when the fuel loading basket 2 is lifted upward as shown by arrow B, the upper part of the fuel loading basket collapses into the cladding tube outlet 4 as shown by arrow C, and the cladding tube that is falling down is taken out.

FIG. 3 is a sectional view showing the operation when the cladding tube falls to the side opposite to the cladding tube outlet 4 due to the balance between the fuel loading and the cladding tube 2, or when it does not fall in either direction.

When the fuel loading car 2 is raised by the fuel loading car lift bag [6, the upper end of the fuel loading car 2 comes into contact with the guide plate 7, as shown by the broken line in FIG. 3(a). When further raised as shown by the arrow, the upper end of the fuel loading lever 2 moves along the shape of the guide plate 7. When the fuel loading basket 2 is tilted as shown by the broken line in FIG. Fall down. From now on, Figure 2 (b
) The tube to be covered can be taken out by the same operation as in ).

The guide plate may have any shape as long as it always pushes the fuel loading basket 2 back toward the cladding tube outlet 4 side. Further, instead of using this guide plate, a method may be used in which a driving mechanism is used to push back the fuel loading lever 2.

FIG. 4 is a sectional view showing an example of the push-back device @12. In this example, the push-back section 13 is the push-back drive device 14.
As a result, an operation as shown by arrow F is performed, and as a result, the fuel loading lever 2 is tilted toward the cladding tube outlet 4 side.

FIG. 5 is a sectional view showing an embodiment of a portion that grips the fuel loading lever 2. FIG. A gripping member 15 is joined to the side surface of the fuel loading cap 2 at a position closer to the bottom than the center of gravity, and a circular gripping hole 16 is bored thereon. One gripping hole 16 is provided on each side, and the centers of the two gripping holes 16 are located at the same height. In other words, the straight line QQ in Figure 5
'Grip holes on both sides] Make sure the center of 6 is on the top.

FIG. 6 is a sectional view showing an embodiment of the structure of the gripping portion of the fuel loading basket gripping device 5. As shown in FIG. There is a conical gripping claw 18 at the tip of the gripping arm 17, and when the gripping arm 17 opens and closes as shown by arrow G, it grips the fuel loading valve 2.

When gripped, the gripping claw 18 enters the gripping hole 16, but
By providing a slight margin, the fuel loading lever 2 can rotate freely around the grip. If the grip hole 16 is tapered as shown, the grip claw 18 can be easily inserted.
The strength to withstand times IJj can be ensured. Since the position of the gripping hole IG needs to be closer to the bottom than the center of gravity of the fuel loading cap 2, the length of the gripping arm 17 can be shortened by making the upper part of the fuel loading cap 2 heavier. In this example, 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 order to move the fuel loading car lifting device 6 to the position of the fuel loading car 2, there are two methods: (1) a method of moving the fuel loading car (2), and (2) a method of moving the fuel loading car lifting device 6 (6). , or G) by partially moving both of them.

An embodiment of the third method will be described with reference to FIG. FIG. 7 shows the moving state of the fuel loading basket 2 in the continuous melting treatment apparatus. The fuel loading basket 2 in the melting tank 1 is held by an annular hanging plate 23, and rotates in one direction at regular intervals. The rotation is performed by a hanging plate rotation drive device 24. The melting 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 this and a partition plate 27, which is installed on the opposite side of the partition wall 26. Discharge port 30
A dissolving treatment liquid 3 in which fuel is dissolved is discharged from the tank. In this device, continuous melting is possible by moving the fuel loading 2 as shown by the arrow. At part 0 in the figure, the fuel loaded part 2 is taken out and transported to part 1, where the cladding tube is taken out and part 3 is put into the melting tank 1 again, and a fuel sheared piece is newly loaded. In the figure, the dissolving treatment liquid 3 is heated by the jacket bottom 25.

An example of the continuous melting treatment apparatus of the present invention using the continuous melting method shown in FIG. 7 will be explained with reference to FIG. 8. The dissolution tank 1 is completely covered with a cover 8 to maintain airtightness. Sections H, I, and 3 in FIG. 7 are also sealed with covers 8, and are connected to the cladding tube outlet 4.

The fuel loading basket lifting device 6 is attached to the cover 8 with the fuel loading basket gripping device 5 hanging thereon, and is moved on the cover 8 by the horizontal moving device 2B as shown by the arrow. This makes it possible to move the fuel loading basket 2 and take out the cladding tube.

According to embodiments of the present invention, fewer drive mechanisms are required to move the fuel loading basket, which is essential to achieve cladding removal and continuous melting, and the frequency of maintenance required for the drive is reduced. Further, the drive unit is attached to a cover 8 on the dissolution tank 1, and can be easily replaced by partially removing the cover 8.

Since maintenance can be performed by remote control of the manipulator, etc., the time required for maintenance and the radiation exposure of maintenance workers can be reduced. Furthermore, since it can be realized in a compact shape, the space required for the melting treatment stage m in the spent nuclear fuel reprocessing facility is small, and the entire melting treatment equipment can be covered with a cover to maintain its airtightness. Therefore, the spread of radioactive contamination can be prevented.

[Effects of the Invention] According to the present invention, by utilizing gravity, fewer driving parts are required to take out the cladding tube, and maintenance frequency can be reduced. In addition, the structure is simple and the drive unit can be replaced by removing part of the cover, making maintenance easy. Remote maintenance using a manipulator, etc. is also possible, reducing maintenance time and maintenance work. This has the effect of reducing radiation exposure for personnel. Further, the cladding tube can be taken out in a compact space, and the airtightness of the entire melting treatment apparatus is not impaired, so that it is possible to prevent the spread of contamination due to radioactivity.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a continuous melting treatment device for spent nuclear fuel according to an embodiment of the present invention, FIGS. 2 to 4 are cross-sectional views of the cladding pipe extraction portion of the device in FIG. 1, and FIG. A perspective view of a fuel loading basket, FIG. 6 is a partial cross-sectional view showing an example of a fuel loading basket gripping device, FIG. 1 is a perspective view of a continuous dissolution processing apparatus showing an embodiment of the present invention during operation. DESCRIPTION OF SYMBOLS 1...Dissolution tank, 2...Fuel loading, 3...Dissolution treatment liquid, 4...Claying tube outlet, 5...Fuel loading basket gripping device, 6...Fuel loading basket lifting/lowering Device, 7... Guide plate, 8... Cover, 9... Cladding tube removal part, 10
... Gripping part, 11... Center of gravity position, 12... Pushing back device, 13... Pushing back portion, 14... Pushing back drive device, 15... Gripping member, 16... Gripping hole, 17...
... Gripping arm, 18... Gripping claw, 23... Hanging plate, 24... Hanging plate rotation drive device, 25... Jacket bottom, 26... Bulkhead, 27... Shikiri plate ,2
8...Horizontal movement device, 29...Cb) Figure 4 Section 5 No. 6 Exit Z4 No. [

Claims (1)

[Claims] 1. (a) a circular dissolution tank filled with a dissolution treatment liquid and for dissolving spent nuclear fuel; (b) a circular dissolution tank filled with a dissolution treatment liquid and for dissolving spent nuclear fuel; (c) a fuel loading basket provided with a fuel loading basket gripping device for taking the fuel loading baskets in and out of the melting tank; A car lifting device, (d) an outlet for undissolved fuel cladding, (e) a supply port for a dissolution treatment liquid, and (f) a discharge port, in the melting treatment device, the fuel loading device provided in the fuel loading car lifting device. The basket gripping device is configured to rotatably grip the fuel loading basket at a position lower than the center of gravity of the entire fuel loading basket including the undissolved fuel cladding after the spent nuclear fuel melting process is completed. When the fuel loading basket is raised, the fuel loading basket is automatically tipped over so that the opening at the top faces downward, so that the internal undissolved fuel cladding tube can be discharged to the outlet of the undissolved fuel cladding tube. A continuous melting and processing device for spent nuclear fuel, which is characterized by: 2. A means for pressing the fuel loading basket is provided in a part of the lifting path of the fuel loading basket so that the upper opening of the fuel loading basket faces the outlet of the insoluble fuel cladding tube. A continuous melting and processing apparatus for spent nuclear fuel according to claim 1. 3. The continuous melting treatment apparatus for spent nuclear fuel according to claim 2, wherein the pressing means is a guide plate.