JPS5885200A - Method of decomposing metal material waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for decomposing and treating waste metal materials such as, for example, radioactive metal materials from a discontinued atomic couplant, particularly radioactive container equipment in a reactor containment vessel, and piping. Regarding.

Current nuclear power plants require decontamination of highly radioactive equipment, especially structures inside the reactor, reactor pressure vessel 9 equipment, and There is a need for a simple method to decompose waste such as pipes.

In addition, in the future, the ratio of dependence on nuclear energy will continue to increase, and it will be important to make the storage of waste after its use as compact as possible.

Conventionally, in the decommissioning technology for nuclear couplants that have ceased to be used, as a treatment method for reactor pressure vessel 1 equipment, piping, etc.
It has been considered to implement methods such as arc cutting and water jet cutting after plant decontamination. In the former case, a large amount of gas or electric power is required as a large heat source for cutting, and a large amount of gaseous secondary waste is generated during cutting, which needs to be disposed of. In the latter,
These include the generation of large amounts of liquid secondary waste and the need for large amounts of electricity. Furthermore, what is common to both is that the blocks of dismantled waste cannot be reduced to a certain level, so in order to reduce the volume, (JP treatment etc.) is required.
Furthermore, the atomic couplant uses materials with different material properties such as stainless steel, carbon steel, and low-alloy steel, and conventional techniques may be subject to limitations in disassembly processing.

This is an application of the properties of metals that cause embrittlement, such as the radioactive Kinne materials at the Chikahara Plant, which has been shut down, and especially the radioactive reactor pressure vessel equipment and piping inside the reactor containment vessel. The present invention provides a simple and safe method for decomposing metal material waste.

The present invention forms a eutectic between a solid wire mesh and a low melting point metal in the part of the metal material to be disposed of that is to be destroyed,
This is a method for decomposing wire mesh material waste, which is characterized by applying force to this part to break it into a desired size. In general, low melting point metals such as Cd, Ga, and Zn are heated at a temperature higher than their melting temperature. If it is attached to other polycrystalline metal materials, it will easily diffuse into the interior of those materials, especially to the grain boundaries, if heated at a temperature that does not allow sufficient diffusion, promoting grain boundary embrittlement of those materials. , significantly lowers strength and causes intergranular cracking at low stress levels.

Moreover, as a result of this, DJ performance is achieved by separating waves into one crystal @ degree as the smallest block.

The above-mentioned embrittlement phenomenon caused by liquid metal is more pronounced when a eutectic is formed between the solid metal and the liquid metal. However, if the temperature is increased first, eutectic formation will occur,
Because the liquid metal diffuses at grain boundaries, the temperature during the diffusion process can be lower than the melting point of the liquid pure metal. Figure 1 shows the embrittlement phenomenon. If a liquid low melting point metal 4 is applied to the surface of a metal material 3 having grain boundaries 2 made up of many crystal grains 1 in FIG. 1A, a low melting point metal @ as shown in FIG. 4 forms a liquid 5 with a eutectic composition with the gold material 3, which can be shown in Figure 181C.
diffuses to grain boundary 2. After the time has elapsed for the diffusion to penetrate through the thickness of the metal material 3, the metal material 3 reaches the grain boundary 2.
This causes de facto grain boundary separation. By applying a slight tensile force to the metal material 3 in this state 11), the metal material 3 can be broken almost on the order of crystal grains, as shown in the first diagram.

For example, if gallium (Ga) is heated and applied to aluminum or aluminum alloy (approx. It has been experimentally confirmed that

The radioactive metal material in question here can be decomposed into fine particles by the following procedure, and is made of a material that is not gas permeable. The finely divided material can be tightly loaded into the container having the opening 6 without any gaps, and the volume of waste can be kept to a minimum.

Examples of combinations of metal materials and low melting point metals that cause embrittlement include steel materials, indium (In), and lithium (Li).
), cadmium (rcd), zinc (Zn) and tellurium (
There is a combination with Te). Further, the combination of aluminum alloy with mercury (Hg), gallium (Ga), sodium (Na), indium (In), tin (an), and zinc (Zn) causes embrittlement of the aluminum alloy. In addition, titanium alloys and cadmium (C'd) cause the embrittlement of titanium alloys. Furthermore, magnesium alloys and sodium (Na)
, in combination with zinc (Zn) causes embrittlement in magnesium alloys. ``In addition, when tensile stress is applied to these structural materials such as steel, aluminium alloy, titanium alloy, magnesium alloy, etc., the diffusion of low melting point metals into the material is promoted, and the present invention It enhances the effect.

In order to fully exhibit the effects of the present invention, it is first necessary to improve the wettability of the low melting point metal with the metal material that causes embrittlement when it becomes a liquid. This can be done by chemical or mechanical treatment to remove dirt, oxides, etc. For example, it is also effective to expose the new surface using a grinder.

Nine, it is possible to liquefy a low melting point metal and physically apply it strongly to promote wetting. In addition to the above-mentioned application method, the liquid metal is vaporized in a container such as a containment vessel or a pressure vessel,
Chemical 1 Application by vapor deposition on the surface of a mechanically treated material. Can be applied to objects with complex shapes. However, due to grain boundary diffusion,
A barrel that is easier to collapse mechanically by providing extremely sharp notches.

Figure 2 shows an example in which the invention is applied to radioactive steel piping inside a containment chamber 4'6.
Low melting point gold l117 is applied over a width δ to a part of the steel pipe 6 in FIG. A, and heated by the heater 8. For example, when gallium Ga is used as a low melting point metal, gallium Ga is 3
Since 1"0 is the melting point, it will sufficiently diffuse in the thickness direction of the steel piping 6 at room temperature, but if you use the 0-mouth heater 8 shown in the figure, the diffusion effect will be further promoted. After the low melting point metal 7 has sufficiently diffused over the period of time, when a tensile force σ is applied as shown in FIG. It is dismantled into a collection of fragments on the order of crystal grains, which constitute 6.

When carrying out demolition work as described above, place a thin sheet of poor material 1 paper or a plastic sheet such as a Teflon sheet on the broken material F to effectively prevent the collection of fragments 11 from scattering.
- Concentrating collection in one place increases the effect of minimizing the area to be decontaminated. Further, in order to make the 60-minute steel pipe fragment 9 and the steel pipe fragment 1o into smaller blocks, the above-mentioned procedure can be repeated. Figure 3 shows a 60-minute steel pipe fragment that has been divided and dismantled as described above and has radioactivity. 9 and fragments IJ, and a collection 11 of crystal grain-sized fragments constituting the steel pipe 6 whose surface is covered with low melting point gold 117 are stored in a storage container 1 that is not gas permeable.
If the embodiment housed in 2 is lined with another plastic, the state of preservation will be even better. This figure shows a state in which divided pieces 9 and 10 of steel piping and a collection of crystal grain-sized pieces 11 are stored without any gaps. In the figure, 12 is the storage container shown earlier, and 13 is the plastic lining inside the storage container. be. The shape of the storage container may be arbitrary, but in order to minimize the gap in the storage location later, a cube, rectangular parallelepiped, or regular hexagonal prism is preferable for storing the storage container.

The method shown in FIGS. 2 and 3 is an embodiment of the present invention, and the combination of fragments of the material to be dismantled and fragments in the order of crystal grains is appropriately selected depending on the shape of the material to be dismantled or the storage container. Naturally, it is within the scope of the present invention to store them in a storage container without any gaps.

As described above, according to the present invention, a large amount of energy is not required to decompose a metal material, and only a small amount of gas or electricity is required to heat a low melting point metal to its melting point. The amount of eyelids as waste is negligible compared to conventional ones, and it can be easily and safely disassembled, disassembled, and stored.

[Brief explanation of drawings]

182 (A) to (D) are cross-sectional views of metal materials showing the grain boundary diffusion mechanism for explaining the decomposition treatment method for metal material waste according to the present invention, and FIGS. 182 (A) to (B) are A schematic diagram for explaining the decomposition treatment method for metal material waste according to the invention, and FIG. 3 is a perspective view showing a storage container used in the invention. l... Metal material crystal grain 2 - Grain boundary 3 - - Gold maple material 4... Low melting point Gold maple 8. ．． Heater
9,10. i Fragments of maple material 11...Collection of fragments 12 Storage container 13...Plastic lining

Claims (5)

[Claims] (1) A metal material that is characterized by forming a eutectic in the part of the metal material that is to be discarded and then applying force to this part to destroy it to a desired size. Waste decomposition treatment method. (2) Form a eutectic between the solid metal and the low-melting point metal liquid metal in the part of the metal material to be destroyed, and apply force to this part to destroy it to the required size. Claim 1: A method for decomposing metal material waste as set forth in claim 1. (3) Applying or applying a low melting point metal as a solid thin film or in a molten state to the part of the metal material to be destroyed, either on the entire surface or in the form of a grid of any size, and then heating it to diffuse and penetrate into the metal material. 3. A method for decomposing metal material waste according to claim 2, characterized in that a eutectic is formed by: (4) A method for decomposing metal material waste as set forth in claim 2, characterized in that the portion to be destroyed is subjected to force by colliding a Kingyoju-Shuntai or by using an explosive such as Daito. . (5) After forming a eutectic in the part of the metal material to be disposed of, apply force to this part to break it into the desired large umbrella, and then use the Teflon sheet or plastic 1. A method for decomposing gold-material waste, comprising storing it in a storage container lined with a sheet.