JP2862899B2 - Radioactive waste conditioning method, device for implementing the method and storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention, as is known, relates to a radioactive waste conditioning method for the storage and storage of radioactive waste, which is one or a major problem in the nuclear industry.

Various methods are being considered to control such waste. For example, waste can be stored open in a pool and sealed or melted in a drum with or without a conventional coating. It is also known to compact waste, so that its volume is reduced by pressing.

The invention applies to compression molding, in particular to all waste whose volume is reduced by this method, for example shells resulting from the cutting of nuclear fuel rods.

The shell is a section of a tube containing fissile material. To withdraw and decompose the material, the pins that make up the fuel assembly are cut and then placed in a decomposer. After decomposing the fissile material, the empty shell is removed for storage and constitutes waste. They can also include other elements, such as plugs, spring profiles, etc., that enter the reactor rod configuration.

The waste can also include tubing fragments resulting from the cutting operation and referred to as "shearing fines".

However, the practice of the method has been particularly contaminated,
For highly irradiated waste, considerable difficulty arises due to the fact that it can only be carried out by the operator at intervals and only in shielded cells or containers.

Although compression molding partially solves the problem of volume required for waste storage, there are also two other issues that are important: waste cooling or coating.

Thus, compression molding is accomplished by condensing radioactive masses that spontaneously heat and become substantially monolithic.
It makes cooling of the storage pool more difficult, for example by water. In addition, there is the danger of radioactive product entrainment by prolonged storage, for example hundreds of years of storage, by constantly leaching from surface water. Attempts have been made to eliminate this problem by coating or encapsulating materials, such as some metals of moist nature, such as cement, resin or lead. However, compression molding and coating have heretofore been relatively incompatible, especially in the core of the compression molded mass.

The present invention relates to a method and a device for the preparation of radioactive waste, which allow the acquisition of non-monolithic compression molding materials which can be penetrated by the liquid phase while using compression molding. In special cases, a cooling liquid phase or a liquid phase consisting of a coating substance can penetrate the material to the core.

Methods for controlling radioactive waste, such as from cutting fuel rods, involve compression molding the shell without reaching a monolithic state and subjecting the resulting mass to its cooling or its coating. It is characterized by processing by immersion in a liquid phase penetrating the core to obtain.

According to the invention, the coating material is a sequestered product selected from cement, resin and metal.

The device according to the invention has a cylindrical jacket or casing, the side walls of which are in the form of longitudinal slots parallel to the direction of compression, the size of which is impermeable to the waste to be compacted. The casing has a closed base at one end and an opening at the other end for the introduction of said waste into the tubular body and forms a daisy. Daisy refers to a configuration in which a plurality of thin plates are provided adjacent to the periphery of the opening, and the shape is reminiscent of daisies (daisy).

According to the invention, the casing is made of a material having a lubricating property to facilitate the action of the press, and the lubricating material is, for example, copper or a copper-based alloy.

The invention also relates to a storage device for coating or cooling, which is compression-molded according to the method of claim 1, wherein the storage device is closed at one end and is introduced into a casing body containing irradiated fuel waste. A cylindrical body having an opening at the other end thereof, a centering means for centering the casing in the cylindrical body, and a return preventing means for fixing the casing in the cylindrical body; It is characterized in that a cooling liquid phase or a coating liquid phase can be introduced into the liquid.

As a result of these features, the casing allows for easy handling of the waste. It also allows lubrication of the press mold, especially if the casing is made of a lubricating material such as copper or copper alloy or other lubricating material. This casing makes it possible to limit the wear of the mold. In addition, the longitudinal slots prevent leakage of waste from the casing during filling and prior to compression molding. However, after compression molding, the slots are opened to allow the coolant to circulate in the block or to allow the adhesive to penetrate the core. After compression molding, the small sized waste that falls into the compression molded block cannot escape, but the longitudinally open slots, called buttonholes, allow for the circulation of liquid and the penetration of the adhesive.

The storage device according to the invention allows cooling or coating of the waste contained in the jacket or casing. As a result of the presence of the casing centering means, the coolant or the coating binder can regularly surround the casing. The flexibility of the centering means also allows for a change in the diameter of the casing introduced into the storage device.

Hereinafter, the present invention will be described in more detail with reference to non-limiting examples and the accompanying drawings.

FIG. 1 is an external view of a jacket or casing according to the invention for compression molding of waste, especially irradiated nuclear fuel waste. The casing, generally designated by the reference numeral 1, is constituted by a tubular body 2 closed at one end by a base 4 and opened at the other end, the upper end in FIG. The tubular body 2 is formed from a thin and preferably metal wall made of a lubricating material such as copper or a copper alloy. The tubular body 2 has a longitudinal opening 6 in the form of a slot parallel to the future compression axis (FIG. 2). This shape is particularly advantageous. Thus, when the casing is in its initial state, i.e., not deformed and before compression molding, the slot 6 has an elongated shape whose cross section is smaller than the smallest dimension of the waste to be compression molded. Thus, the slot 6 allows for the retention of waste within the tubular body 2. However, after compression molding of the casing 1 in the press, the longitudinal slots 6 have button holes 6a allowing the passage of cooling fluid or coating material.
Open to form (FIG. 3). However,
At this stage, small sized waste cannot escape through the opening buttonhole 6a due to the fact that the material contained in the casing is compression molded.

The upper casing opening is constituted by a daisy 8. In the open position of the daisy 8, a space is provided between which the radial lamellas 10 are moved away from each other and which allows filling of the casing. Once the casing has been filled, all the fan-shaped lamellas are turned downward and are easy to reclose the daisy 8 in an adjacent manner to allow a complete sealing of the casing.

FIG. 2 shows the process of compression molding the casing in a filled or sealed state in a mold using jack 23. The casing 1 is made, for example, of copper for lubricating the mold and in FIG. 2 the longitudinal slots 6 begin to open under the action of a jack 23 which causes the start of compression molding.

The material from which the casing is formed allows lubrication of the press mold, especially if said material is lubricating and is, for example, copper or a copper alloy or other lubricant. This feature facilitates the introduction of the casing into the mold. Furthermore, it has the advantage of reducing the compression force during compression molding and limits mold wear. Reduce the coefficient of wear between the outside of the casing and the body of the mold. Finally, upon removal of the mold, it facilitates removal of the compression molded casing and therefore reduces the risk of disassembly of the block.

A longitudinal slot 6 having a cross section smaller than the cross section of the waste ensured that the waste could not escape from the casing during filling before compression molding. During the compression molding, the compressive force exerted in the longitudinal direction tends to collapse the tubular body of the casing and moves away from the lips of the longitudinal slot 6. At the end of the compression molding, the slot 6a is opened but small waste falling into the compression molded block cannot escape. However, the open slot 6a is then formed like a buttonhole and allows the circulation of liquid or subsequently the penetration of the adhesive.

FIG. 3 shows a state of the casing 1 after compression molding. The longitudinal dimension of the casing has been reduced to approximately one-fourth of its original size and the slot 6 has been opened to allow the subsequent supply of liquid phase to penetrate the core of the compacted mass. It has the shape of a buttonhole. In accordance with the method of the present invention, the compression molding is stopped at a stage where it does not further comprise a monolithic mass that is desirable to avoid that the compacted waste must exert excessive force on jack 23.

After compression molding, the casing is stored in the storage device shown in FIG.
21 can be introduced within. This device has an elongated tubular body 12 closed by a base 14 and having an opening 16 in its upper part according to FIG. Reference numeral 18 is in the cylindrical body 12.
Is fixed. These centering means are constituted by flexible elements fixed to the inner wall of the cylinder 12. Thus, the cooling liquid or coating adhesive introduced into the device surrounds the casing 1 and penetrates their core. The flexibility of the centering member 18 also allows for a change in the diameter of the introduced casing.

The return preventing means 20 is formed of a flexible member disposed near the opening 16 and fixed to the inner wall of the tubular body 12.
It should be noted that the centering member 18 can also fulfill a detent function. Thus,
When the members do not encounter the cylindrical outer wall of casing 1 as a result of their flexibility, they are labeled in FIG.
It occupies the position indicated by 20 and bears against the upper end of the casing 1, thus preventing axial movement of the casing in the longitudinal direction of the storage device 21. Thus, in the event of an accident, for example a fall of the device 21, the casing is retained in said device 21. The detent means also ensure that the casing or jacket does not float in the adhesive due to buoyancy when the coating adhesive used has a density higher than the density of the compression molded casing. The device is applicable irrespective of the number of casings introduced and allows for height and diameter variations in connection with compression molded casings.

If the storage device 21 with its compression molded casing or jacket is immersed in a cooling liquid (eg a pool) or filled with a coating liquid (eg molten lead) via its opening 16, The liquid then immediately passes through the core of the material and fills the gaps evacuated by non-monolithic compression molding of each casing.

Furthermore, in the case of a cooling liquid, the base 14 of the storage device 21
Does not need to be hermetically sealed (or can be provided with a valve not shown in FIG. 4) to facilitate the circulation of the cooling liquid within the tubular body 12, thereby being further compression molded. Improves cooling through the core of casing 1.

FIG. 5 shows a shell, such as 24, broken into chunks and embedded in a coating material 25 in a cross-sectional view of a compression molded and coated casing or jacket. FIG. 5 shows the crushing of the copper body 2 of the casing 1 having the buttonhole-shaped opening 6a.

[Brief description of the drawings]

FIG. 1 is an external view of a compression molded jacket or casing according to the present invention. FIG. 2 is a schematic sectional view showing the casing of FIG. 1 during compression molding in a press. FIG. 3 is a schematic diagram showing the subsequent compression molding of the casing. FIG. 4 is a schematic diagram showing a storage device for a compression molded casing for cooling or coating the casing. FIG. 5 is a sectional view showing the final state of the subsequent compression molding and coating of the casing. In the drawing, reference numeral 1 is a casing, 2 and 12 are cylindrical bodies, 4 is a base, 6 is an opening, 8 is a daisy, 10 is a thin plate, 14 is one end of a cylindrical body, 16 is the other open end, and 18 and 20 are open ends. The centering means 21 is a storage device.

Claims (8)

(57) [Claims] 1. A radioactive waste conditioning method for treating radioactive waste resulting from the cutting of a nuclear fuel rod, wherein said radioactive waste is compressed and shaped without reaching a monolithic state and the lumps thus obtained. Immersion in a liquid phase to obtain its cooling or its coating, and treating the lumped core by penetrating the liquid phase. 2. The radioactive waste control method according to claim 1, wherein the coating material for coating the mass is a sealed product selected from cement, resin and metal. 3. Apparatus for compression molding waste by compression in a press under the action of a jack, comprising a tubular body (2), the side walls of which are to be compressed. A casing, having an opening (6) in the form of a longitudinal slot parallel to the compression direction, sized not to pass through the casing and having a base (4) closed at one end and said cylindrical shape at the other end. A waste compression device having an opening for introducing the waste into the body (12), wherein a plurality of thin plates are provided adjacent to the periphery of the opening, and the thin plate can seal the opening. Molding equipment. 4. The waste compression molding apparatus according to claim 3, wherein said casing is made of a material having lubricity to facilitate a pressing operation. 5. The apparatus according to claim 4, wherein the lubricating material is copper or a copper-based alloy. 6. A storage device for coating or cooling compression molded waste according to the method of claim 1 for introducing a casing (1) closed at one end (14) and containing irradiated fuel waste. A cylindrical body (12) having an open end (16), a centering means (18) for centering the casing in the cylindrical body, and a centering means (18) for fixing the casing (1) in the cylindrical body; A return blocking means (20),
A storage device, wherein a cooling liquid phase or a coating liquid phase can be introduced into the casing. 7. The storage device according to claim 6, wherein said centering means (18) is constituted by a flexible member fixed to an inner wall of said tubular body. 8. The centering means (18) also prevents passage of the compression molded waste from the casing (1) from the tubular body (12) of the storage device (21). 8. The storage device according to claim 7, wherein the storage device serves as a return blocking member.