JP4001561B2 - Melting canister - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a melting canister used for melting and solidifying radioactive miscellaneous solid waste generated from a nuclear facility.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent No. 3096184 [0003]
Radioactive miscellaneous solid waste such as metal, concrete, and glass generated from nuclear power plants and other nuclear facilities has been conventionally melted and solidified in a high-frequency induction heating furnace, and a ceramic canister is used for this purpose. It has been. Radioactive miscellaneous solid waste is melted at a high temperature of about 1400-1500 ° C. in the canister. However, if the radioactive miscellaneous solid waste contains low-boiling-point components, May foam and foam, and the molten metal surface may be exposed. At this time, as shown in FIG. 5, a large amount of splashing occurs on the surface of the melt, and there is a possibility of overflowing outside the canister. If such an overflow occurs, it will adhere to the ascending / descending portion of the canister and will not be able to move up and down smoothly, or will cause a problem that radioactive material will adhere to the furnace. A typical low-boiling component is zinc having a boiling point of about 930 ° C., which is abundant in galvanized iron products.
[0004]
Therefore, when processing radioactive miscellaneous solid waste containing a large amount of low-boiling substances, the radioactive miscellaneous solid waste thrown into the canister will not cause overflow due to splashing even when the molten metal surface rises temporarily. The low boiling point material had to be pretreated and completely removed. However, there is a problem that volumetric efficiency decreases when the input amount of radioactive miscellaneous solid waste is reduced. Further, there is a problem that it is difficult to completely remove low boiling point waste in the pretreatment process.
[0005]
Therefore, Patent Document 1 describes a method for subjecting radioactive miscellaneous solid waste to a solid waste containing a low boiling point substance and a solid waste other than that and then subjecting it to a melting treatment. However, this method has a problem that it cannot prevent molten metal overflow due to low boiling point components that could not be completely removed.
[0006]
[Problems to be solved by the invention]
The present invention solves the above-described conventional problems, and can prevent overflow from the canister even when the radioactive miscellaneous solid waste containing low-boiling substances is melt-processed. Therefore, the input amount to the canister can be reduced. The object of the present invention is to provide a melting canister that can be stably treated even when a low boiling point component that does not need to be lowered and cannot be removed by pretreatment is mixed.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention is a melting canister for melting and solidifying radioactive solid waste, and is provided with an overflow prevention ring that forms an inner flange at the upper opening edge of the canister. It is characterized by. The overflow prevention ring can be attached to the upper opening edge of the canister by bonding or fitting, and any material that can withstand the melting temperature may be used. Especially, the overflow prevention ring is used to suppress thermal stress. Is preferably made of the same material as the canister.
[0008]
The melting canister of the present invention is provided with an overflow prevention ring at the upper opening edge, so even when the radioactive miscellaneous solid waste containing low-boiling substances is melted, even if the molten metal surface rises temporarily and jumps, Spattering of the molten metal can be prevented by the overflow prevention ring. For this reason, the melting process can be performed in the same manner as in the case of melting a normal radioactive miscellaneous solid waste. This overflow prevention ring can be easily attached by gluing or fitting, and any material can be used as long as it can withstand the melting temperature. No cracking occurs.
Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes a canister made of conductive ceramics capable of induction heating by high frequency. The canister 1 is made of an alumina or zirconia ceramic containing carbon, and has a diameter of 480 mm and a thickness of 30 mm, for example. An overflow prevention ring 3 that forms a horizontal inner flange 2 is provided at the upper opening edge of the canister 1. The overflow prevention ring 3 in FIG. 1 is a flat ring shape having a thickness of, for example, 10 mm, and the inner flange portion 2 projects over the inside of the canister 1 by about 25 mm. The overflow prevention ring 3 may be any material as long as it can withstand the melting temperature. In particular, if the same material as that of the canister 1 is used, the coefficient of thermal expansion becomes equal. Can be prevented. The overflow prevention ring 3 in FIG. 1 is bonded to the upper opening edge of the canister 1 with an adhesive.
[0010]
The overflow prevention ring 3 in FIG. 1 is a flat ring shape, but it may have a height of several tens of millimeters as shown in FIG. By making the inner flange portion 2 an upward inclined surface, the splash direction of the molten metal can be changed inward, so that the splash does not fall on the overflow prevention ring 3 and overflows to the outside of the canister 1. The flow can be prevented more reliably. For this reason, in the case of the overflow prevention ring 3 in which the inner flange portion 2 is inclined upward, the inner flange portion 2 can be slightly reduced.
[0011]
If the height of the overflow prevention ring 3 is too high, the upper clearance required for melting cannot be secured. Further, since the overflow prevention ring 3 is stored and stored in the drum can as it is without being removed from the canister 1, if the height of the overflow prevention ring 3 is too high, an operation such as cutting is required. The height of the overflow prevention ring needs to be set based on the relationship between the upper clearance in the furnace and the height of the drum.
[0012]
The overflow prevention ring 3 in FIG. 2 is also bonded to the upper opening edge of the canister 1 with an adhesive. However, as shown in FIG. 3, the step 4 that fits into the overflow prevention ring 3 on the inner periphery of the opening edge of the canister 1. It is also possible to provide a fitting type. In this case, an adhesion process is not necessary. However, since the outer diameter becomes large when it is fitted to the inner periphery of the opening edge of the canister 1 and it is difficult to store it in the drum can, it is preferable to use the inner circumference fitting type as shown in FIG.
[0013]
Next, a method for melting radioactive miscellaneous solid waste by the high-frequency melting furnace 10 shown in FIG. 4 will be described. First, as shown by a one-dot chain line in FIG. 4, the canister 1 is placed on the lifting platform 11 in the lowered position, and then the lifting device is driven to move the canister 1 to the furnace body as shown by the solid line in FIG. 4. Insert into 12 from below. A predetermined amount of radioactive miscellaneous solid waste is stored in the canister 1 in advance.
[0014]
Thereafter, high frequency power is applied to the induction heating coil 13 to inductively heat the canister 1 made of conductive ceramics to 1400 to 1500 ° C. to melt the radioactive miscellaneous solid. Since the liquid level is lowered with melting, radioactive miscellaneous solid waste is additionally charged into the canister 1 via the waste waste charging port 14 and melted. If the radioactive miscellaneous solid waste introduced at this time contains a low-boiling substance such as zinc, the low-boiling substance vaporizes and foams in the molten metal, and the molten metal in the canister 1 temporarily rises.
[0015]
During the temporary rise of the molten metal surface, a large amount of splashing occurs on the molten metal surface. However, splashing that occurs at the peripheral edge of the canister that tends to jump to the outside is stopped by hitting the inner flange 2 of the overflow prevention ring 3 provided at the upper edge of the opening of the canister 1. Doing so is prevented. 2 and 3, in the case of the overflow prevention ring 3 with the inner heel portion inside inclined upward, the upward inclined inner ridge portion 2 of the molten metal that scatters more than the one with the inner heel portion inner side horizontal. The direction will be inward, and overflow will be prevented more accurately.
[0016]
In this way, while preventing overflow, radioactive miscellaneous solid waste is introduced into the canister 1 and melted. When the molten metal surface in the canister 1 reaches a predetermined level, the elevator 16 is lowered to lower the abutment. 23 Canister 1 is carried out from above. As described above, the overflow prevention ring 3 remains attached to the canister 1. The unloaded canister 1 is cooled to solidify the molten metal, accommodated in a drum can, and cement mortar is poured into a stable melt-solidified material suitable for transportation and storage.
[0017]
【The invention's effect】
As is apparent from the above description, the present invention is introduced into the molten metal by providing an overflow prevention ring that forms an inner flange at the upper opening edge of the canister used in the melting furnace for melting radioactive miscellaneous solid waste. Even if the low boiling point material is vaporized to cause a temporary rise of the molten metal surface or a splash from the molten metal surface, overflow can be prevented. For this reason, there is no need to reduce the capacity of the canister. Stable treatment is possible even when low-boiling components that could not be separated during pretreatment of radioactive solid waste are mixed.
[0018]
In addition, if the overflow prevention ring is attached to the upper opening edge of the canister by adhesion or internal fitting as in claim 2, the production cost of the canister does not increase significantly, and the overflow prevention ring is in accordance with claim 3. Any material can be used as long as it can withstand the melting temperature. Therefore, an optimal material can be selected under conditions such as cost and formability. In particular, when the overflow prevention ring is made of the same material as that of the canister as in the fourth aspect, cracks and breakage due to the coefficient of thermal expansion can be accurately suppressed. Therefore, the present invention greatly contributes to the development of the industry as a melting canister that solves the conventional problems.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a third embodiment of the present invention.
FIG. 4 is a partially cutaway front view showing a high-frequency melting furnace.
FIG. 5 is an explanatory diagram showing the occurrence of overflow in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Canister, 2 Inner ridge part, 3 Overflow prevention ring, 10 High frequency melting furnace, 11 Lifting stand, 12 Furnace main body, 13 Induction heating coil, 14 Waste waste inlet

Claims (4)

A melting canister for melting and solidifying radioactive miscellaneous solid waste, comprising an overflow prevention ring that forms an inner flange at an opening edge of the upper portion of the canister. 2. The melting canister according to claim 1, wherein the overflow prevention ring is attached to the upper opening edge of the canister by adhesion or fitting. 3. The melting canister according to claim 1, wherein the overflow prevention ring is made of a material that can withstand a melting temperature. 4. The melting canister according to claim 1, wherein the overflow prevention ring is made of the same material as that of the canister.

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