JP2596915B2 - Method of melting radioactive waste - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave melting method for melting radioactive waste (incinerated ash) after incineration using microwaves.

[Conventional technology]

Radioactive waste generated from nuclear power plants, etc.
It is roughly classified into three types, liquid and solid, and the intensity of radioactivity is classified into high level, medium level, and extremely low level.

Conventionally, combustibles among low-level solid wastes have been incinerated and then stored in a drum.

However, as the amount of solid waste increases, a large amount of ash is generated after incineration, and the amount of storage is increasing year by year. Thus, the above-described treatment has its own limitations.

Therefore, treatment of the solid waste (incinerated ash) using microwaves is disclosed in, for example, Japanese Patent Application Laid-Open No. 55-143380.

The radioactive waste treated by these microwave melting devices is a so-called incinerated ash obtained by subjecting the radioactive waste discharged from a nuclear power plant or the like to an incineration process.

And in these methods, the incinerated ash stored in the drum can is supplied to the microwave melting device by any method. Then, the microwave generated by the microwave generator is supplied to the furnace main body through the waveguide, and the incineration ash is melted in the retort. After the melting is completed, the retort is separated from the furnace main body.

[Problems to be solved by the invention]

However, in the method described above, the melting state of the incineration ash in the retort cannot be accurately monitored, and the control of the incineration ash supplied to the retort has not been sufficiently performed.

[Object of the invention]

The present invention has been made to solve such a conventional problem, and an object thereof is to supply incinerated ash when radioactive waste (incinerated ash) carried into a treatment plant is melted in a retort. An object of the present invention is to provide a method for melting radioactive waste that can be efficiently controlled in accordance with the melting state.

[Means for solving the problem]

In the method for melting radioactive waste according to the present invention, a microwave generated by a microwave generator is supplied to a furnace body via a waveguide, and the radioactive waste supplied to the furnace body is melted in a retort. In the method of melting radioactive waste, the radioactive waste is continuously supplied into the retort to melt the radioactive waste, and the temperature of the entire molten metal surface in the retort is set to the wide-angle By non-contact thermometer,
It captures the ratio of the molten surface of radioactive waste in the retort and the unmelted material in the retort as viewed from the top as the average temperature of the entire molten metal surface, measures the molten state, and controls the amount of radioactive waste sent. It is assumed that.

[Function of the invention]

In the present invention, the amount of incinerated ash is controlled by monitoring the temperature of the molten surface in the retort with a wide-angle non-contact thermometer installed at the upper part of the furnace main body. Supplied.

(Example of the invention)

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the figure, 1 is a microwave generator, 2 is a waveguide attached to the microwave generator 1, and 3 is a waveguide 2
The power monitor includes an output detector 4 and a reflected wave detector 5, and monitors a microwave output. Reference numeral 6 denotes an EH tuner, which has an electric field adjuster 7 and a magnetic field adjuster 8, adjusts the amplitude of the magnetic field and the electric field, and matches the unmelted material (incinerated ash). Reference numeral 9 denotes two quartz plates provided on the waveguide 3, which pass microwaves but do not pass dust, and prevent backflow of radioactivity. The space 34 between the quartz plates 9 and 9 is provided with an alarm device 35 which constantly sends air of a predetermined pressure and detects a pressure drop when the quartz plate 9 is broken so that radioactivity does not flow backward. . Reference numeral 10 denotes a furnace main body to which the waveguide 2 is connected. Reference numeral 11 denotes a wide-angle non-contact thermometer provided at an upper portion of the furnace main body 10, which controls the amount of incinerated ash by monitoring the temperature of the molten surface in the retort 27. Reference numeral 12 denotes an ITV that monitors the state of arc and gas combustion in the furnace body 10. In order to prevent ash from adhering to the monitoring window where the ITV is installed, air is constantly supplied so that the situation inside the furnace body 10 can be accurately grasped. Reference numeral 13 denotes an exhaust device provided in the furnace body 10, which has a back filter 14, a HEPA filter 15, and an exhaust blower 16, and discharges exhaust gas from the furnace body 10 while preventing outflow of radioactivity. Reference numeral 17 denotes a glass forming material supply device provided in the furnace main body 10, which is configured to supply the glass forming material thereon after the melting of the incinerated ash in the retort 27 and to contain the radioactive material so that the radioactivity does not leak. Have been. Reference numeral 18 denotes an arc sensor provided in the furnace main body 10, reference numeral 19 denotes a radiation thermometer and a feed stop thermometer provided in the furnace main body 10, which monitors the condition of the inner wall of the retort 27 and makes the molten metal surface of the incinerated ash a predetermined level. It is configured to issue a command to stop the supply of incinerated ash when it becomes. 20 is an incineration ash supply device provided in the furnace body 10,
A device 22 for taking out the incinerated ash sent by the drum 21;
A ceramic filter 23 that adsorbs and separates incinerated ash that is pneumatically conveyed after being taken out;
A hopper 24 that receives the incinerated ash separated by the separation plate from 23
And a screw feeder 25. Reference numeral 26 denotes a glove box provided at the lower part of the furnace main body 10, a retort elevating device 28 for connecting and separating a retort 27 for receiving incineration ash to a lower part of the furnace main body 10, and a drum can 32
It comprises a retort moving device 30 packed in the inside and a turntable 31 for carrying out the retort 27 packed in the drum 32.

 Next, the present embodiment will be described according to the processing steps.

First, the retort 27 is raised by the lifting device 28,
It is connected to the lower part of the furnace body 10. This coupling is made via a choke structure 36 to prevent microwave leakage.

Next, incineration ash is continuously supplied to the retort 27 from the screw feeder 25. This supply should be done in advance
The incinerated ash packed and transported into the incinerator 21 is supplied to the incineration ash supply device 20
At the time of adsorption by the ceramic filter 23 by air transport,
Since it is separated and stored in the hopper 24 and adjusted so that it can be supplied to the furnace main body 10 by the screw feeder 25, it can be performed according to a control device (not shown) or an operator's command.

After the incineration ash is supplied, the microwave generator 1 is driven to generate a microwave, and the microwave is supplied to the furnace body 10 through the waveguide 2. Then, the incineration ash continuously supplied to the retort 27 is melted by the microwave. This situation is due to wide angle non-contact thermometer 11 and IT
It is monitored by V12 and by a radiation thermometer / feedstop thermometer 19.

In this melting process, the incinerated ash is removed from the screw feeder.
25, a continuous melting treatment is performed. The state of the molten metal surface in this processing step is a state in which the unmelted material partially covers the molten metal surface in a high temperature state of about 1200 ° C. In order to completely melt the material to be melted and obtain a uniform melt, it is necessary to keep the state of this surface in an appropriate state.

Therefore, in the present invention, the temperature of the molten metal surface is controlled by controlling the amount of the molten material to be charged.

As a specific means, a wide-angle non-contact thermometer 11 was provided on the upper part of the furnace body 10.

The wide-angle non-contact thermometer 11 is for grasping the average temperature of the entire molten metal surface, and measures the non-uniform temperature of the molten metal surface as an average value, and measures the ratio between the molten surface and the unmelted material of the entire molten metal surface. Controlling the amount of incinerated ash by capturing at the average temperature and measuring the molten state.

The radiation thermometer / feed stop thermometer 19 is a retort
It is installed at the center of the furnace body 10 so as to face obliquely downward so that the temperature at a position about 10 cm below the 27 flange surface 271 can be measured.

Therefore, the amount of incinerated ash supplied by the feeder 25 is controlled by the wide-angle non-contact thermometer 11, and the melting state in the retort 27 is directly monitored by the radiation thermometer / feed stop thermometer 19. At this time, the temperature control of the hot water surface
Based on the sensing signal from the wide-angle non-contact thermometer 11, the process is performed according to the following flow: converter → controller → converter → inverter → motor 251 → incineration ash input.

Then, when it is detected by the radiation thermometer / feed stop thermometer 19 that the molten metal surface of the incinerated ash has reached a predetermined level, the supply of the incinerated ash from the incinerated ash supply device 20 is stopped.

Next, the glass forming material is supplied from the glass forming material supply device 17, and after covering the incineration ash with the glass forming material, the glass forming material is melted by microwaves to confine the radioactivity.

Thereafter, the microwave generator 1 is stopped, and the supply of the microwave is stopped. Then, the melt in the retort 27 is cooled and solidified. Next, after the retort 27 is lowered by the retort elevating device 28, the retort 27 is rotated by the moving device 29 and packed in the drum 32 placed on the retort moving device 30. After solidifying the drum 32 with cement, the drum can 32 is carried out by the turntable 31.

The microwave generator, the waveguide, the sensing device provided in the waveguide, the various sensing devices provided in the furnace body, the exhaust device, the incineration ash supply device, the radiation thermometer and feed in the above embodiment. The stop thermometer, the glove box, the connection structure between the furnace body and the glove box, etc. are merely examples, and the present invention is not limited to these, and any structure that can be used in a microwave melting device is used. It may be.

〔The invention's effect〕

As described above, according to the present invention, the melting state of the incineration ash in the retort is monitored by the wide-angle non-contact thermometer, and the entire temperature of the molten metal surface is detected. Since the feed rate of the radioactive waste is controlled based on the average temperature of the entire hot water surface determined by the ratio, incineration ash is supplied according to the melting state of the incineration ash in the retort. That is, there is an advantage that the radioactive waste can be continuously supplied and the incineration ash can be reliably melted.

[Brief description of the drawings]

The drawings are explanatory diagrams showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Microwave generator, 2 ... Waveguide, 10 ... Furnace body, 11 ... Wide angle non-contact thermometer, 17 ... Glass forming material supply device, 19 ... Radiation thermometer and feed stop thermometer , 20
…… Incineration ash supply device (radioactive waste supply device), 25 ……
Feeder, 27 ... retort.

Claims (1)

(57) [Claims] 1. A method for melting radioactive waste, wherein microwaves generated by a microwave generator are supplied to a furnace body via a waveguide, and the radioactive waste supplied to the furnace body is melted in a retort. In the retort, radioactive waste is continuously supplied into the retort to melt the radioactive waste, and the temperature of the entire molten metal surface in the retort is measured by a wide-angle non-contact thermometer provided at the upper part of the furnace body. The ratio of the molten surface of the radioactive waste in the retort and the unmelted material in the retort viewed from the top is captured as the average temperature of the entire molten metal surface, the molten state is measured, and the feed amount of the radioactive waste is controlled. To melt radioactive waste.