JP3847231B2 - High frequency induction furnace for miscellaneous solid waste melting and miscellaneous solid waste melting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for incineration or melting to reduce the volume of solid waste, particularly radioactive miscellaneous solid waste generated in a nuclear facility or the like.
[0002]
[Prior art]
Of the low-level radioactive waste generated at Japanese nuclear power plants, miscellaneous solid waste is disposed of at the Rokkasho Low-Level Radioactive Waste Burial Center operated by Japan Nuclear Fuel Co., Ltd. At the time of disposal, the waste is filled in a 200-liter drum and buried as a waste body filled with mortar.
Since the burial site is limited, it is preferable to increase the capacity of the waste packed in the drum can to reduce the number of drum cans to be buried. Power companies are also trying to reduce disposal costs by reducing the number of drums as much as possible. For this reason, it is required to reduce the volume as much as possible when packing waste into drums.
[0003]
As a method for reducing the volume of waste, there is a method using a high frequency induction heating furnace. In this method, waste is melted and reduced in a canister installed in a high-frequency induction heating furnace, solidified in the canister as it is, and packed in a drum can together with the canister, and a solidified material such as mortar is filled in the gap. To make a waste.
In order to facilitate handling of the canister, such as loading into the furnace and taking it out of the furnace, and to facilitate measurement of the outer surface temperature of the canister, it is usually between the inner wall of the induction heating furnace body and the canister. It has a gap. For example, Japanese Patent Laid-Open No. 6-273591 discloses an incineration melting treatment technique in which a combustible solid waste is incinerated under an oxygen-containing gas supply to reduce the amount, and further is induction-heated to melt and reduce the volume. Also, a melting furnace having a gap between the canister and the furnace wall is shown.
However, if the canister breaks due to canister manufacturing defects, thermal stress due to excessive temperature rise, erosion, etc., the melt inside the canister flows into the gap between the canister and the furnace wall, and a great deal of effort is required to recover it. It is required and long-term shutdown is required.
[0004]
[Problems to be solved by the invention]
Therefore, the problem to be solved by the present invention is that even if there is an accident where the canister is broken in the furnace, it is not necessary to suspend the operation for a long time for the recovery of the induction heating furnace. It is intended to provide a high-frequency induction heating furnace for melting radioactive solid waste and a method for melting miscellaneous solid waste that can produce waste.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a high-frequency induction heating furnace for melting miscellaneous solid waste according to the present invention includes a device for supplying a sandy substance between a furnace wall and a canister outer wall of the melting furnace, and between the furnace wall and the canister outer wall. The apparatus is provided with a device for discharging the sandy substance, and the outside of the canister is filled with the sandy substance to melt the miscellaneous solid, and after the melting, the sandy substance is discharged.
As the sandy substance, it is preferable to select a non-conductive substance having heat resistance and fluidity.
[0006]
When the sandy substance is filled around the canister by using the high frequency induction heating furnace of the present invention and the solid waste is melted, the temperature difference between the inside and outside of the canister wall is suppressed by the heat insulating effect of the sandy substance. Thermal stress can be relaxed. A high-temperature canister tends to expand due to the hoop stress generated by the molten metal having a high specific gravity, but the canister is not easily damaged because the pressure of the sandy substance is applied from the periphery of the canister to relieve the hoop stress.
Thus, the requirements for thermal and mechanical strength are reduced, the wall of the canister can be thinned, the manufacturing cost of the canister is reduced, and the volume of waste to be packed in the drum can is increased.
Furthermore, even if a crack occurs in the canister and the molten metal leaks, it soaks into the sandy substance and solidifies to serve as a lid for the crack to prevent new leakage, thus preventing the spread of leakage.
[0007]
In addition, when the canister base mounted with the canister is moved up and down, the canister is set in the melting furnace to close the opening provided in the bottom of the melting furnace to form a gap for storing the sandy substance around the canister. It may be configured as follows.
When such a method is used, the convenience of the present invention can be easily obtained by making the most of the conventional configuration.
[0008]
Alternatively, an outer container for storing the canister may be prepared, and when the canister is stored in the outer container, a space for storing the sandy substance may be formed around the canister. The canister table can be set at an appropriate position in the melting furnace by mounting the outer container and inserting it from the opening of the melting furnace bottom.
In this method, the canister can be stored in the outer container and filled with the sandy substance or the sandy substance can be excreted with an appropriate tool at an appropriate place. Maintenance of the equipment is simple because no sandy material contacts the furnace walls.
[0009]
In addition, it is preferable to provide the rotating brush which wipes off the sandy substance adhering to the outer wall of the canister below the melting furnace.
In addition, used sandy substances include separators that remove contaminants from sandy substances, radiation monitors that measure the radioactivity of sandy substances, supply hoppers that hold sandy substances, and new sandy substances. It is preferable to recycle and reuse it with a sandy material regenerating apparatus equipped with a storage hopper for replenishing the water.
Sandy substances can be radioactive because they are exposed to exhaust gas when radioactive waste is melted or mixed with fragments of miscellaneous solids. Must be eliminated and reused.
[0010]
In order to solve the above-mentioned problem, the miscellaneous solid waste melting method of the present invention includes a canister filled with solid waste placed on a canister base, the canister is inserted into the melting furnace, and the bottom cover is placed on the melting furnace with the canister base. To form a void, fill the void with sandy material, perform high-frequency heating of the canister, fill and melt the solid waste as the volume of the canister decreases, and after cooling and solidification The canister base is lowered and the sandy substance is discharged and received in a receiving tray.
When the miscellaneous solid waste melting method of the present invention is used, it is possible to prevent leakage accidents by using a simpler canister, and solidify immediately in the sandy material even if a crack occurs and the molten metal leaks. Then, it will close the crack and will not leak any more.
[0011]
The miscellaneous solid waste melting method of the present invention uses an outer container that houses a canister filled with solid waste, fills the periphery of the canister housed in the outer container with a sandy substance, and places the outer container on a canister base. The canister is placed in a melting furnace and set at an appropriate position, and the canister is heated at high frequency. The content of the canister is reduced and the solid waste is filled and melted. After cooling and solidification, the canister stand , And the outer container may be transported to an appropriate place to discharge the sandy substance.
Furthermore, the discharged sandy substance may be reused after being subjected to a regeneration process using a separator or a radiation monitor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to examples.
FIG. 1 is a flowchart of a miscellaneous solid waste melting method according to one embodiment of the present invention, FIG. 2 is a diagram illustrating the function of a rotating brush in this embodiment, and FIG. 3 is a block diagram showing a sandy material reuse mechanism. FIG. 4 is a diagram for explaining an example of an apparatus used for the miscellaneous solid waste melting treatment of the present invention, and FIG. 5 is a diagram for explaining another method for discharging a sandy substance.
[0013]
FIG. 1 is a step-by-step description of a miscellaneous solid waste melting method using a high-frequency induction heating furnace in one embodiment of the present invention, according to (a) to (f). The high frequency induction heating furnace of the present embodiment includes a melting furnace 4 having an open bottom. A canister base 3 on which the canister 2 is mounted is provided immediately below the melting furnace 4. The canister base 3 is driven up and down by an elevating mechanism 5. When the mounted canister 2 is set in the melting furnace 4, the upper surface of the canister base 3 hits the edge of the bottom of the melting furnace 4 and is sealed. A tray 6 is provided under the canister base 3.
[0014]
In the miscellaneous solid waste melting method of the present embodiment, first, a canister 2 previously filled with a solid waste 1 is placed on a canister base 3 made of a refractory material (FIG. 1A), and the canister 2 is melted in a melting furnace. 4 and set (FIG. 1B). The canister table 3 hits the bottom edge of the melting furnace 4 and serves as a bottom lid.
Next, the sandy substance 8 is filled in the gap 7 formed between the canister 2 and the inner wall of the melting furnace 4 (FIG. 1C). When high-frequency heating is performed in this state, miscellaneous solid waste melts to become molten metal 9 and the volume is reduced. When the liquid level of the molten metal 9 in the canister 2 decreases, the miscellaneous solid waste 1 is added to compensate for this (FIG. 1 (d)). After additional supply is repeated and a predetermined amount of waste is melted and further cooled and solidified (FIG. 1 (e)), when the canister 2 is lowered, a gap is formed between the bottom edge of the melting furnace 4 and the canister base 3, Since the sandy substance 8 filled in the portion 7 falls from the end of the canister base 3, it is received by the tray 6 and collected (FIG. 1 (f)).
[0015]
The canister 2 in which miscellaneous solid waste is melted and solidified is charged into a drum can by a processing apparatus (not shown), mortar is injected and fixed, and then transported to a predetermined burial site for disposal. If the sandy substance 8 exposed to the exhaust gas in the melting furnace 4 or mixed with or adhering to the radioactive substance adheres to the surface of the canister 2, the sandy substance 8 peels off while the canister 2 is handled. Therefore, as shown in FIG. 2, it is preferable to provide a rotating brush 10 below the melting furnace 4 to wipe off the sandy substance 8 attached to the surface of the canister 2. The rotating brush 10 moves in the vertical direction while rotating and rotates around the canister 2. The sandy substance 8 that has been wiped off is received by the tray 6.
Similarly, it is preferable to remove sand adhered to the furnace wall with a brush or the like.
[0016]
A substance having heat resistance and fluidity is selected as the sandy substance 8 to be filled in the gap 7. In addition, non-conductive materials are selected so as not to interfere with high-frequency induction. Further, during melting of the miscellaneous solid waste, the temperature becomes about 1200 ° due to heat conduction from the canister 2, so the particles need not be fixed or fused to each other even in a high temperature state. Substances that release gas even if they come out of contact with the canister 2 must be avoided. Examples of satisfying such conditions include dry silica sand, ceramic particles such as alumina and zirconia.
[0017]
When the sandy substance 8 meeting such a condition is filled around the canister 2 and the waste is melted, the temperature difference between the inside and outside of the canister wall is conventionally 200 ° C. due to the heat insulating effect of the sandy substance 8. What is about 300 ° C. can be suppressed to 100 ° C., for example, and the thermal stress of the canister 2 can be relaxed. The high-temperature canister 2 tends to expand due to the hoop stress generated by the molten metal 9 having a specific gravity of about 7.8 if iron is the main component. However, the pressure of the sandy substance 8 is applied from the periphery of the canister 2. Since the hoop stress is relieved, the canister 2 is hardly damaged.
[0018]
Furthermore, even if a crack occurs in the canister 2 and the molten metal 9 leaks, it penetrates into the sandy substance 8 and solidifies to become a lid of the crack to prevent new leakage, thus preventing the leakage from expanding. Can do.
In addition, as described above, since the requirements for thermal and mechanical strength are reduced, the wall of the canister can be thinned, and there is an advantage that the capacity is increased and the manufacturing cost is reduced.
[0019]
Part of the sandy material is exposed to the exhaust gas when the radioactive waste is melted, and radioactive waste may be mixed in. Therefore, the sandy material filled between the canister and the furnace wall is very small. Comes with radioactivity. If all the sandy substance recovered from the melting furnace is treated as low-level radioactive waste, the cost becomes excessive. Therefore, it is preferable to attach a processing plant for sandy substances and separate and separate contaminated portions, and reuse the available sandy substances.
[0020]
FIG. 3 is a block diagram of a processing plant that enables reuse of sandy material.
The processing plant comprises a separator 11, a radiation monitor 12, a supply hopper 13 and a storage hopper 14 for storing fresh sandy material. The sandy substance collected from the melting furnace 4 may contain additional supplied waste fragments or leaked solidified waste pieces. The separator 11 separates and removes the mixed substances. To do.
Since the sandy material to be recycled is exposed to the gas generated when melting the radioactive waste, it is exposed to minute radioactivity because it is a radioactive material that cannot be removed. Then, the radioactivity is measured with the radiation monitor 12, and if there is a contaminated part exceeding a predetermined reference value, it is separated and disposed of.
[0021]
Sandy substances that are determined to be reusable are stored in the supply hopper 13 and supplied in order when the canister 2 is set.
In order to enable continuous use of the melting furnace, a filling amount for a plurality of batches is secured in the supply hopper 13. If the sandy substance becomes insufficient due to the disposal, a new sandy substance can be replenished from the storage hopper 14 as appropriate.
If necessary, a cooling device may be provided in front of the separator to cool the collected sand substance.
A solid-gas mixed phase flow using air as a medium can be used for conveying the sandy substance in the sandy substance treatment system.
[0022]
FIG. 4 is a view for explaining a method of using the outer container instead of setting the canister directly on the canister table.
An outer container 22 having a size capable of accommodating the canister 21 and creating a gap is prepared. The outer container 22 is formed of a nonconductive heat resistant material such as ceramic.
The canister 21 is inserted into the outer container 22 (FIG. 4 (a)), and the gap between the canister 21 and the inner wall of the outer container 22 is filled with the sandy substance 23 (FIG. 4 (b)). The outer container 22 filled with the canister 21 and the sandy substance 23 is placed on the canister table and inserted into the melting furnace.
[0023]
Since the sand-like substance 23 is stored in the outer container 22, the canister base and the bottom edge of the melting furnace do not need to be tightly sealed, and the position of the canister 21 in the melting furnace can be freely selected. . Further, in the previous embodiment, when the canister table is lowered from the melting furnace, the sandy material falls from the edge of the canister table to the receiving tray. However, in the method using the outer container 22, the sandy material 23 is filled in the canister 22. The place and method for picking up and taking out can be arbitrarily selected. For example, the sandy substance 23 may be taken out after the canister 22 is moved from the canister base to another place. In the outer container 22 shown in the drawing, a plurality of holes 24 are provided in the bottom, and by opening the holes 24 provided in the bottom of the outer container 22, the sand-like substance 23 can be recovered by dropping into a receiving tray 25. (FIG. 4C).
In addition, as shown in FIG. 5, the sand-like substance 23 can be sucked out from the outer container 22 by the vacuum suction device 26 and transported to a collection tank 27 provided at an arbitrary place.
[0024]
【The invention's effect】
As described above, the high frequency induction furnace for melting miscellaneous solid waste and the miscellaneous solid waste melting method of the present invention makes it difficult for the canister to be damaged during processing, and the canister is damaged in the furnace. Even if there is, the induction heating furnace can be easily restored, so that the waste body can be manufactured stably without a long-term operation stoppage.
[Brief description of the drawings]
FIG. 1 is a flowchart of a miscellaneous solid waste melting method according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating the function of a rotating brush in the present embodiment.
FIG. 3 is a block diagram illustrating a sandy material reuse mechanism used in the present embodiment.
FIG. 4 is a drawing for explaining an example of an apparatus used for the miscellaneous solid waste melting treatment of the present invention.
FIG. 5 is a drawing for explaining another method for discharging sandy substances in the apparatus of FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Miscellaneous solid waste 2 Canister 3 Canister stand 4 Melting furnace 5 Elevating mechanism 6 Sampling pan 7 Cavity 8 Sandy substance 9 Molten metal 10 Rotary brush 11 Separator 12 Radiation monitor 13 Supply hopper 14 Storage hopper 21 Canister 22 Outer container 23 Sandy substance 24 bottom hole 25 saucer 26 vacuum suction device 27 collection tank

Claims (9)

The melting furnace has an opening at the bottom, and includes a canister base that moves up and down with a canister, and the canister base closes the opening at the bottom when the canister is set in the melting furnace to store the sandy substance. a high frequency induction furnace to form a gap portion for discharging a device for supplying a sandy material between an outer wall of the the furnace wall of the melting furnace canister, sand-like material between the furnace wall and the canister outer wall A high-frequency induction furnace for melting miscellaneous solid waste, comprising: a device for melting miscellaneous solids by filling the outside of a canister with the sand-like material and melting the miscellaneous solids.   The high frequency induction furnace according to claim 1, wherein the sandy substance is a non-conductive substance having heat resistance and fluidity. And an outer container of a non-conductive having a hole to drop the sand-like material on the bottom to form a void portion for accommodating the sand-like substance on the outside of the outer wall of said canister further accommodate the canister, the wall Instead of filling a sandy substance between the outer wall and the canister, a sandy substance is filled in the gap in the outer container, and the outer container is inserted through an opening of the canister base at the bottom of the melting furnace. 3. The high frequency induction furnace according to claim 1, wherein the induction furnace is set at an appropriate position in the melting furnace. The high-frequency induction furnace according to any one of claims 1 to 3 , further comprising a rotating brush that removes the sandy substance adhering to the outer wall of the canister below the melting furnace. Sandy with a separator that removes contaminants from sandy substances, a radiation monitor that measures the radioactivity of sandy substances, a supply hopper that holds sandy substances, and a storage hopper that replenishes new sandy substances The high frequency induction furnace according to any one of claims 1 to 4 , further comprising a substance regeneration device.   A canister filled with solid waste is placed on a canister table, the canister is inserted into a melting furnace, the bottom of the melting furnace is covered with the canister table, a void is formed, and a sandy substance is placed in the void. Filling and high-frequency heating of the canister, filling and melting solid waste as the volume of the canister is reduced, cooling and solidifying, lowering the canister base and discharging the sandy substance A miscellaneous solid waste melting method characterized by being received in a tray. A canister filled with solid waste is stored in an outer container having a hole in the bottom, and a sandy substance is filled around the canister, and the outer container is placed on a canister table and inserted into a melting furnace, and placed in an appropriate position. Set, perform high-frequency heating of the canister, fill and melt the solid waste as the volume of the canister decreases, and after cooling and solidifying, lower the canister base and place the outer container in an appropriate place A miscellaneous solid waste melting method, wherein the sandy substance is discharged from the hole and received in a tray . The miscellaneous solid waste melting method according to claim 6 or 7 , wherein the sandy substance is a non-conductive substance having heat resistance and fluidity. Furthermore, contaminants are removed from the discharged sandy substance, the radioactivity of the sandy substance is measured, the high-radioactivity part is discarded, and the remaining sandy substance is stored in the supply hopper, 9. The miscellaneous solid waste melting method according to any one of claims 6 to 8 , wherein when the amount of the stored sandy substance is insufficient, a new sandy substance is supplied from the storage hopper.

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