JPH0231840B2 - HOSHASEIHAIKIBUTSUSHOKYAKUBAINOYOJUKOKASOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for solidifying radioactive waste, and more particularly to an apparatus for melting and solidifying incineration ash of radioactive waste.

Conventionally, combustible waste contaminated with radioactivity generated from facilities handling radioactive materials such as nuclear power plants is generally incinerated, and the incinerated ash is filled into drum cans, etc. It is usually stored in an appropriate location inside the building. However, since these incinerated ash are in the form of powder and granules, it is desirable to stabilize and reduce the volume of the incinerated ash before transporting or storing the drum can filled with incinerated ash, and various methods have been studied. has been done. Recently proposed methods for treating the incinerated ash include a method of solidifying the incinerated ash with cement, and a method of mixing asphalt, plastic, etc. with the incinerated ash and solidifying it. However, in the former method of solidifying incinerated ash with cement, (1) In order to mix ash and cement to obtain a solidified material with stable density and strength, the weight ratio of ash to cement must be adjusted to 1 part of ash. It is necessary to set the cement to 4 or more, and as a result, the volume of the solidified body becomes larger than the volume of the ash, resulting in an increase in volume.

(2) When mixing ash and cement, metal contaminants in the incinerated ash react with the alkaline aqueous solution of cement to generate hydrogen gas, which creates voids in the solidified material and reduces density, strength, etc. and lacks stability. Therefore, in order to solve this problem, pretreatment to prevent the generation of hydrogen gas is required, which complicates the apparatus.

There were drawbacks such as: In addition, the latter method or device for solidifying incinerated ash with asphalt, plastic, etc. requires pretreatment such as removing metal pieces from incinerated ash and pulverizing it, which has the disadvantage of making the equipment complex and large.

The present invention solves the above-mentioned conventional drawbacks, and provides a melting and solidifying device capable of melting and converting granular radioactive waste incineration ash into a stable, volume-reduced solidified material suitable for transportation and storage. The gist of the furnace is a sealed container-like furnace body whose bottom can be opened by a bottom cover that is driven up and down, and a guide provided on the outer periphery of the side wall of the furnace body. a heating coil, a metal cylindrical heating body disposed inside the furnace main body at a position corresponding to the induction heating coil, and a metal cylindrical heating body disposed on a support fixed to the bottom cover, and the above-mentioned heating by the bottom cover being mounted on a support fixed to the bottom cover. a bottom plate that substantially closes the lower end of the cylindrical heating body when the bottom of the furnace body is closed; a container that is placed on the bottom plate and can be inserted into and removed from the cylindrical heating body from below; and a container provided on the top of the furnace body. an inert gas supply port provided in the bottom cover, and a gas supplied from the inert gas supply port formed in the furnace main body through the inside and outside of the cylindrical heating body to the exhaust gas port. an incinerated ash supply port that is attached to the furnace body and supplies radioactive waste incineration ash into the container; and an oxygen supply that is attached to the furnace body and supplies oxygen-containing gas to the container. An apparatus for melting and solidifying radioactive waste incineration ash includes a tube and a detection device attached to the furnace body to detect the molten state in the container.

An embodiment of the present invention will be described below with reference to the drawings.

A furnace body 2 in the form of a closed container supported by a support frame 1 erected on a foundation includes a cylindrical side wall 3 made of a non-metallic material, for example quartz, and a metal lid 4 attached thereto. Consists of. A bottom cover 7 that freely closes the bottom of the furnace body 2 is fixed to a lifting platform 6 that is guided so as to be raised and lowered by a guide 5 set up on a foundation and driven up and down by a drive device such as a motor (not shown). There is. An induction heating coil 8 is installed on the outer periphery of the side wall 3.
is installed. This induction heating coil 8 is housed within a cover 9 and is cooled by a known cooling method such as air cooling or water cooling. On the other hand, a cylindrical heat insulating wall 11 made of a heat insulating material such as asbestos or castable is provided inside the side wall 3 of the furnace body 2, and an induction heating coil 8 is provided inside the heat insulating wall 11.
A metal cylindrical heating body 12 is provided at a position corresponding to the heat insulating wall 11, and an outer space 13 is formed between the metal cylindrical heating body 12 and the heat insulating wall 11. A heat insulating cover 15 having a hole 14 is attached to the upper end of the heat insulating wall 11, and a small gap 16 is formed between the heat insulating cover 15 and the cylindrical heating element 12. These heat insulating walls 11 and cylindrical heating body 1
2 is fixedly supported by the furnace body 2 or the supporting frame 1. On the other hand, a bottom plate 19 that closes the lower end of the cylindrical heating element 12 when the bottom of the furnace body 2 is closed by the bottom cover 7 is attached to a non-metallic support 18 such as a heat insulating material fixed to the bottom cover 7. be. The material of this bottom plate 19 is preferably a metal material, but may be a non-metal material. Bottom plate 1
A container 20 made of a non-metallic material such as carbon graphite or ceramic, preferably a metallic material such as stainless steel, is placed on top of the container 9 . The container 20 is driven up and down together with the bottom cover 7 and a supporting base 18 integrated therewith, and can be freely inserted into and removed from the cylindrical heating element 12 from below. An inert gas supply port 21 is provided in the bottom plate 19, and a hole 22 communicating with this supply port and a hole 2
Four radial grooves 23 communicating with the upper end of the support base 18 and opening upward are bored in the support base 18. Further, the bottom plate 19 is provided with a ventilation hole 25 that communicates the inner space 24 between the container 20 and the cylindrical heating element 12 with the groove 23 of the bottom plate 19. A port 26 is provided. As a result, from the inert gas supply port 21 to the hole 22, the groove 23, and the outer space 1.
3. An outer gas flow path 27 leading to the exhaust gas port 26 through the gap 16 and the hole 14, and an inner gas flow path which similarly branches off from the groove 23 and leads to the exhaust gas port 26 through the ventilation hole 25, the inner space 24, and the hole 14. 28 is formed. In addition, a container 20 is attached to the lid portion 4 of the furnace body 2.
An incineration ash supply port 31 that supplies radioactive waste incineration ash into the inside of the incineration ash, an oxygen supply pipe 32 that also supplies combustion air necessary for burning unburned content in the incineration ash into the container 20, A thermometer 33 such as a radiation thermometer for detecting the molten state inside the lid 4 is attached to each penetrating the lid 4.

In the radioactive waste incineration ash melting and solidifying device 34 having the above configuration, when the induction heating coil 8 is energized to heat the cylindrical heating body 12, the container 20 is heated by heat radiation and heat transfer from the heating body. be done. Further, when the container 20 is made of metal, induction heating of the container itself is also added. Also, inert gas supply port 2
1 supplies inert gas such as argon or nitrogen gas into the furnace body 2 to heat the inside and outside of the cylindrical heating body 12,
That is, the inner space 24 and the outer space 13 are made into an inert gas atmosphere. Then, if radioactive waste incineration ash is supplied into the container 20 from the incineration ash supply port 31, and at the same time, combustion air or other oxygen-containing gas is supplied into the container 20 from the oxygen supply pipe 32, the remaining waste in the incineration ash can be The fuel is burned, and the ash is heated and melted at high temperatures. At this time, if the melting point of the incinerated ash is high, a flux that forms a eutectic with the incinerated ash, such as boric acid, borax, sodium carbonate, etc., may be supplied into the container 20 together with the incinerated ash. Only the flux is first transferred from the incineration ash supply port 31 to the container 20.
Alternatively, the ash may be heated and melted into a liquid state, and then incinerated ash may be fed on top of the ash to perform the melting process. For example, _SiO2 is 35-45wt%,
Incineration ash with a chemical composition containing 12 to 17 wt% each of Al ₂ O ₃ , CaO, and MgO, 8 to 13 wt % of Fe ₂ O ₃ , and small amounts of Na ₂ O, ZnO, etc. has a melting point of about 1200°C. However, as mentioned above, if boric acid, borax, sodium carbonate, etc., which form a eutectic with the incinerated ash, are used as a flux, the temperature can be melted at a temperature of about 900 to 1100℃. Can be melted at heating temperature. During the above melting operation, the melting state inside the container 20 can be detected by the thermometer 33.
Note that a liquid level gauge, a monitor television, or the like may be used instead of the thermometer 33 or in combination with the thermometer. In addition, the gas inside the furnace body 2 is discharged through the exhaust gas port 26.
Suction from the tank and clean it using a filter, etc.
When the molten material in the container 20 reaches a predetermined amount, the furnace body 2 is cooled by natural cooling, etc., and the molten material is transferred to the container 20.
Once the container 20 is solidified and fixed within the container 20, the elevator platform 6 is lowered, the container 20 is removed from the bottom plate 19, a new container 20 is mounted on the bottom plate 19, and the same steps as above are performed. Repeat. Incidentally, all non-combustible impurities such as metals, bricks, and glass mixed in the incineration ash are also taken into the molten material in the container 20 and fixed.

The present invention is not limited to the above-mentioned embodiment, and the heat insulating wall 11 and the heat insulating lid 15 may be omitted, for example, if the furnace body 2 has good heat insulation properties. Further, the gas flow path from the inert gas supply port 21 to the inner and outer circumferential parts of the cylindrical heating element 12 does not pass through the abutment 18 and the bottom plate 19;
The inert gas may be caused to flow into the inner space 24 from around the cylindrical heating element 12 through a hole formed in the cylindrical heating element 12 or a gap formed between the cylindrical heating element 12 and the bottom plate 19.

As explained above, according to the present invention, granular radioactive waste incineration ash with a small bulk specific gravity can be confined in a container as a small-volume inorganic solidified body using an induction heating furnace type device with a simple structure, In particular, since it is equipped with an oxygen supply pipe, even incineration ash containing a large amount of unburned matter can be stably solidified. Furthermore, since the container is placed inside the metal cylindrical heating body and induction heating is performed, the incineration ash can be efficiently heated by selecting the shape and material of the cylindrical heating body. Furthermore, since the inside and outside of the cylindrical heating element and the outside of the container are in an inert gas atmosphere, there is little oxidation loss even at high temperatures, and the life of the device is long.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a melting and solidifying apparatus showing an embodiment of the present invention. 2...Furnace body, 6...Elevating platform, 7...Bottom cover, 8
... Induction heating coil, 12 ... Cylindrical heating body, 13
...Outside space, 18...Abutment, 19...Bottom plate, 2
0... Container, 21... Inert gas supply port, 24...
...Inner space, 26...Exhaust gas port, 27...Outer gas flow path, 28...Inner gas flow path, 31...Incineration ash supply port, 32...Oxygen supply pipe, 33...Thermometer, 34... Melting and solidifying equipment.

Claims (1)

[Scope of Claims] 1. A furnace body in the form of a sealed container whose bottom part is releasably closed by a bottom lid that is driven up and down, an induction heating coil provided on the outer periphery of a side wall of the furnace body, and the furnace body. a metal cylindrical heating body disposed inside the furnace at a position corresponding to the induction heating coil; a bottom plate that substantially closes the lower end of the cylindrical heating body; a container placed on the bottom plate and capable of being inserted into and removed from the cylindrical heating body from below; an exhaust gas port provided at the top of the furnace body; an inert gas supply port provided in the lid; and a gas flow passage formed in the furnace body that guides the gas supplied from the inert gas supply port to the exhaust gas port through the inside and outside of the cylindrical heating body. , an incineration ash supply port attached to the furnace body and supplying radioactive waste incineration ash into the container; an oxygen supply pipe attached to the furnace body supplying oxygen-containing gas into the container; An apparatus for melting and solidifying radioactive waste incineration ash, comprising a detection device attached to the container to detect a molten state within the container. 2. The apparatus for melting and solidifying radioactive waste incineration ash according to claim 1, wherein the container is a metal container. 3. The apparatus for melting and solidifying radioactive waste incineration ash according to claim 1 or 2, wherein the oxygen supply pipe is a combustion air supply pipe. 4. The apparatus for melting and solidifying radioactive waste incineration ash according to claim 1, 2, or 3, wherein the detection device for detecting the molten state in the container is a thermometer.