JP2908584B2 - Radioactive waste melting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for melting and processing radioactive waste, and more particularly to a melting apparatus which can be used at a high temperature of 1300.degree.

[0002]

2. Description of the Related Art Conventionally, combustible waste generated from radioactive material handling facilities such as nuclear power plants is incinerated, and the incinerated ash is discharged from drums, etc. And is stored in a suitable place in the facility. However, since these incinerated ash are in powder form, it is desirable to stabilize and reduce the volume of incinerated ash when transporting or storing drums filled with incinerated ash, and various treatment methods have been studied. . Recently proposed methods of treating these radioactive wastes include, for example, the first method of solidifying radioactive waste or incinerated ash with cement, and the first method of mixing radioactive waste or incinerated ash with asphalt or plastic to solidify it. There is a second method, a third method for heating and solidifying radioactive waste or incinerated ash at a high temperature.

[0003] When each of these methods is examined in detail, in the cement solidification method, which is the first method, it is necessary to mix waste or ash with cement to obtain a solidified material having a stable density, strength, and the like. It is necessary to make the weight ratio of ash etc. and cement to ash etc. 1 or more to cement 4 or more, so that the volume of the solidified body becomes larger than the volume of ash etc., resulting in an increase in volume. . In addition, the asphalt and plastic solidification method, which is the second method, requires pretreatment such as removal of metal fragments from waste or incinerated ash and pulverization, so that the equipment becomes complicated and large. Was. Furthermore, in the third method, the heat-melt solidification method, the problems caused by the first and second methods described above can be effectively removed. However, since the waste or incinerated ash is melted at a high temperature, the iron is removed by electromagnetic induction. High temperature is achieved by heating metal containers such as
However, there is a problem that the melting treatment of wastes and the like that melt at a higher temperature cannot be performed.

On the other hand, the applicant of the present application has already proposed an apparatus using a waste storage container as a conductive ceramic heating element. According to this apparatus, the metal container is made of a conductive ceramic heating element. It is possible to realize a melting treatment of wastes and the like that melt at a high temperature of 1300 ° C to 1600 ° C.

[0005]

However, in the above-described apparatus, although a high temperature of 1300 ° C. to 1600 ° C. can be achieved, the upper limit of the calorific value of the container itself is limited by its size and the like, so there is a limit. It was difficult to increase the melt processing speed to the desired speed. (It is conceivable to increase the melt processing speed by increasing the size of waste storage containers that cannot be reused and increasing the output of electromagnetic induction heating coils. It is not a good idea to invite up). Further, in the above-described apparatus, the upper surface of the abutment made of a non-metal such as a heat insulating material, which is in contact with the lower surface of the container, becomes brittle due to a heat cycle, and causes a decrease in durability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a melting processing apparatus for melting a radioactive waste or the like at a high speed at a high temperature to obtain a stable reduced volume solidified body suitable for transportation and storage. It is assumed that.

[0007]

According to the present invention, there is provided a radioactive waste melting apparatus, comprising: a furnace main body whose bottom can be closed by a vertically movable bottom cover; and an electromagnetic wave wound around an outer peripheral portion of a side wall of the furnace main body. Waste storage comprising an induction heating coil, an abutment fixed on the bottom cover, and a conductive ceramic heating element mounted on the abutment and electromagnetically heated to a high temperature by the electromagnetic induction heating coil. A container, a furnace exhaust gas outlet provided in the upper lid of the furnace body, and a waste supply port for introducing radioactive waste into the waste storage container, and at least an upper part of the abutment is electrically conductive. Characterized by comprising a conductive ceramic heating element.

[0008]

According to the present invention, in addition to the waste storage container, the upper portion of the abutment on which the waste storage container is mounted is also formed of a conductive ceramic heating element. Heat to a desired high temperature (for example, 13
(00 ° C. to 1600 ° C.) and a desired calorific value, and the melt processing speed is improved. In addition, at least the upper part of the abutment is C-SiC
System, C-Al ₂ O ₃ system or other conductive ceramic heating element, so it has excellent thermal shock resistance and improved durability (life).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of the melt processing apparatus of the present invention. In FIG. 1, a closed vessel-shaped furnace body 2 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-made side wall 3 attached thereto. And a lid 4. A bottom cover 7 for closing the bottom of the furnace main body 2 releasably is fixed to a lift 6 that is guided vertically by a guide 5 erected on a base and is driven up and down by a drive device such as a motor (not shown). An induction heating coil 8 is attached to the outer peripheral portion of the side wall 3. The induction heating coil 8 is accommodated in a cover 9 and 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. An insulating cover 13 having a hole 12 is attached to the upper end of the insulating wall 11, and the insulating cover 13 is fixedly supported on the furnace body 2 or the support frame 1.

On the bottom cover 7, an upper portion 14a made of a conductive ceramic heating element, preferably a C-SiC or C-Al ₂ O ₃ type ceramic, and a lower portion fixed to the lower surface thereof are provided.
An abutment 14 made of 14b (a non-metal such as a heat insulating material) is fixed, and a waste storage container 15 made of the same conductive ceramic heating element as described above is placed on the abutment 14. The container 15 is driven up and down together with the bottom cover 7 and the support 14 integral therewith, and is configured to be able to be inserted into and removed from the heat insulating wall 11 from below. Furnace body 2
An exhaust gas outlet 16 is provided in the upper part of the housing, and the exhaust gas and the like at the time of melting are guided to the outside through the hole 12 provided in the heat insulating lid 13. The lid 4 of the furnace body 2 includes a waste storage container.
A waste supply port 17 for supplying radioactive waste and the like to the inside 15, and oxygen for supplying an oxygen-containing gas necessary for burning unburned matters in the waste or incineration ash supplied to the container 15 as necessary. A supply pipe 18 is provided, and a detection device such as a radiation thermometer, a liquid level gauge, and a monitor TV for detecting the molten state in the container 15
19 are attached through the lid 4 respectively. Furthermore,
A nitrogen purge nozzle 20 for guiding N ₂ from the nitrogen supply device (not shown) outside the device to the inside of the device is provided through the heat insulating wall 11 and the like, and the upper portion 14a of the support 14 and the container 15 which are easily oxidized because they contain carbon. To prevent oxidative degradation of In order to further prevent oxidation deterioration of the upper portion 14a of the abutment, a frit material may be applied to the surface to form a glass layer.

In the radioactive waste melting apparatus 21 having the above structure, when the induction heating coil 8 is energized, the waste storage container 15 itself made of a conductive ceramic heating element is directly heated and the upper part 14a of the abutment 14 is heated. Is also directly heated, so that the waste can be melted in a high temperature range of 1300 to 1600 ° C. At that time, the container 15 and the conductive refractory 14a
The material of the conductive ceramic heating element for use, for example, C-Al ₂
In the case of using O ₃ ceramics, the electric resistivity value is 5 × 10 ⁻³ (Ω · cm) to 15 × 10 ⁻³ (Ω · cm) depending on the carbon content, and the weight of the container 15 is 140 (kg). ), Heating temperature 1400 (℃)
The weight of the upper part 14a of the abutment is 60 (kg) and the heating temperature is 1200
(° C), the heat capacity (calorific value) of the container 15 is 140 (kg) × 0.3 (Kcal / kg ° C) × 1400 (° C) = 58800 (Kcal), and the heat capacity (calorific value) of the upper part 14a of the abutment ) Is 60 (kg) × 0.3 (Kcal / Kg ℃) × 1200 (℃) = 21600 (Kcal). Therefore, a calorific value equivalent to 36% of the calorific value of the container 15 can be obtained from the upper part 14a of the abutment, and the calorific value necessary for performing the melting processing of the waste at a desired speed (high speed) can be obtained. Even if it cannot be secured by itself, the shortfall can be compensated for by the calorific value from the refractory 14a.

When the melt in the vessel 15 reaches a predetermined amount, the furnace body 2 is cooled by natural cooling or the like, and
When solidified in the container 15 and fixed in the container 15, the elevator 6 is lowered, the container 15 is removed from the support 14, and a new container 15 is removed.
Is mounted on the abutment 14, and the same steps as described above are repeated.

The present invention is not limited to the above-described embodiment, but can be variously modified and changed. For example, when the furnace main body 2 is rich in heat insulation, the heat insulation wall 11 and the heat insulation lid 13 may be omitted.

[0014]

As is apparent from the above description, according to the radioactive waste melting apparatus of the present invention, at least the upper part of the waste storage container and the abutment on which the waste storage container is mounted is made of a conductive ceramic. Because of the heating element, the upper part of the container and abutment is effectively heated by induction heating, and a desired high temperature (for example, 1300 ° C to 1600 ° C) and a desired amount of heat can be obtained. Radioactive waste that could not be treated can be melted at a high speed. The abutment has C-SiC on the top.
System, C-Al ₂ O ₃ system or other conductive ceramic heating element, so it has excellent thermal shock resistance and improved durability (life).

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a radioactive waste melting apparatus according to the present invention.

[Explanation of symbols]

 2 Furnace body 6 Elevator 7 Bottom lid 8 Induction heating coil 14 Abutment 14a Upper abutment 14b Lower abutment 15 Waste container 17 Waste supply port 20 Nitrogen purge nozzle 21 Melting equipment

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/00 115 F23G 7/00 J 7/00 103Z 103 B09B 3/00 303K

Claims (2)

(57) [Claims] 1. A furnace body whose bottom can be closed by a bottom cover that can be raised and lowered, an electromagnetic induction heating coil wound around an outer peripheral portion of a side wall of the furnace body, and an abutment fixed on the bottom cover. When,
A waste storage container that is placed on the abutment and is electromagnetically heated to a high temperature by the electromagnetic induction heating coil and that is made of a conductive ceramic heating element, and an in-furnace exhaust gas outlet provided in an upper lid of the furnace body, Melting the radioactive waste, comprising: a waste supply port for charging the radioactive waste into the waste storage container; and at least the upper portion of the abutment is constituted by a conductive ceramic heating element. Processing equipment. 2. The radioactive waste melting treatment apparatus according to claim 1, wherein the conductive ceramic heating element is made of a C-SiC-based or C-Al ₂ O ₃ -based ceramic.