JPH0631841B2 - Method and apparatus for treating radioactive waste - Google Patents

Description

The present invention relates to a method and apparatus for treating mobile radioactive waste.

Liquid radioactive waste such as radioactive waste liquid, waste resin, waste sludge, etc. generated in a radioactive material handling facility such as a nuclear power plant has conventionally been treated or stored according to its characteristics. For example, radioactive liquid waste is concentrated in an evaporator,
It is stored in a tank as a concentrated waste liquid as it is, or as a solidified product mixed with cement or asphalt in a drum, and then stored in the facility. Further, the waste resin and the waste sludge are stored in a slurry state in a tank or dehydrated by a centrifugal dehydrator or the like and then mixed and cemented with cement in a drum can and stored in a facility. However, in these methods, the storage efficiency is low and the number of storage tanks or drums is enormous.Therefore, concentrated waste liquid, waste resin, and waste sludge are evaporated and dried into powder by an externally heated centrifugal thin film dryer, and then pelletized. Alternatively, it has been attempted to further reduce the volume by mixing and solidifying with asphalt or plastic. However, the method using the centrifugal thin film dryer has the following drawbacks. That is, since the scraping blade provided inside the dryer rotates at a high speed, there are many failures due to wear and vibration, and it takes time and trouble to replace and inspect parts. Since it grows while sticking to the rotating shaft and the like, it is necessary to stop the device at regular intervals and wash the inside with hot water or the like, so continuous operation for a long time cannot be performed. Also, since the heating method is external heat indirect heating, the heat transfer efficiency is low and the temperature of the steam, which is the heat source, is 200
Since it was as low as ℃ or less, the processing capacity of the device was small, and it was impossible to directly powder the radioactive waste liquid before concentration. In particular, when treating a concentrated waste liquid containing boric acid and sodium hydroxide as main components, which is generated from a pressurized water nuclear power plant, the product is hard to be a powder because the drying temperature is as low as 200 ° C or less, and boric acid and hydroxide After adjusting the mixing ratio of sodium to a certain narrow range, it was necessary to carry out a drying treatment. Further, since the steam generated by the drying is returned to the water by the condenser, a secondary waste liquid is generated and it is necessary to reprocess this waste liquid.

The present invention solves the above-mentioned drawbacks of the prior art. A method for treating radioactive waste, which enables treatment for a long time with a device that has few failures and does not require maintenance, and is capable of treating a large amount of radioactive waste. Another object of the present invention is to provide a liquid radioactive waste generated in a radioactive material handling facility in a vertical type with a support plate having a large number of holes. A plurality of spherical bodies are supplied onto a large number of spherical bodies deposited in a cylindrical container, and the spherical bodies are horizontally fixed with a base fixed to a vertical rotation shaft and extend in the horizontal direction so that the tip reaches near the inner wall surface of the container. The hot gas supplied to the lower side of the supporting plate is circulated upward through the holes by pressing and driving by the stirring blades, and the radioactive waste is discharged from the high temperature gas through the holes. In a method for treating radioactive waste, which is characterized in that after heating with a gas to form a powder, the powder is dropped and accumulated from a hole of the support plate into a powder reservoir provided at the bottom of the container, Further, the gist of the present invention is that a vertical cylindrical container-shaped main body having a support plate having a large number of holes therein, a large number of spherical bodies deposited on the support plate, and extending in the horizontal direction. A stirrer in which the bases of a plurality of stirring blades whose tips reach the vicinity of the inner wall surface of the main body are fixed to a vertical rotating shaft, a radioactive waste supply port opening above the spherical body, and the support plate. A high-temperature gas inlet provided in the main body below the main body, an exhaust outlet provided in the main body above the deposition layer of the spherical body, and a bottom portion of the main body below the support plate. Radioactive waste with a powder reservoir In the processing unit.

The present invention will be described in more detail below with reference to FIG.

Liquid radioactive waste 1 such as radioactive waste liquid, concentrated waste liquid, waste resin, slurry of waste sludge, etc. is stored in tank 2
Is pumped into the processing device 4 by the pump 3. The processing device 4 is provided with a support plate 6 having a large number of holes inside a main body 5 in the form of a vertical cylindrical container, and a large number of spherical bodies 7 preferably made of ceramic material are deposited on the support plate 6. The spherical body 7 is formed by fixing the bases of a plurality of stirring blades 10 that extend horizontally and the tips of which reach the vicinity of the inner wall surface of the main body 5 to a vertical rotary shaft 9 driven by a rotary drive mechanism 8. The apparatus 11 is configured to continuously stir. Further, an air supply port 12 provided below the support plate 6 of the main body 5
Is supplied with hot air that is high-temperature air heated to 200 ° C. or higher by the hot air generator 13. The radioactive waste 1 sent into the processing device 4 is supplied from the nozzle-shaped radioactive waste supply port 14 opening above the spherical body 7 to the spherical body 7.
Inside the deposit layer while being dropped from the surface of the spherical body 7 heated by hot air and flowing down along the surface of the spherical body 7 and through the holes of the support plate 6 fed from the air supply port 12. Is dried by hot air flowing upwards, drops downward together with the powder 15, collects in a powder reservoir 16 provided at the bottom of the main body 5, and is discharged outside from the powder outlet 16a at any time. Be done. On the other hand, the hot air containing the evaporated water flows out from the exhaust port 17 provided in the upper portion of the main body 5, is removed by the dust remover 18 and is then discharged into the atmosphere by the exhaust fan 19. Obtained powder 1
5 can be used for any solidification treatment method using cement or the like.

Example In the above apparatus, about 20 alumina spheres having a diameter of 20 mm were used as the spherical body 7, and Na ₂ SO ₄ was used as the main component in an amount of 20.
Spherical body 7 at a rate of 8 kg / H containing simulated concentrated waste liquid containing 7% by weight
Of air at 300 ° C.
It was supplied from the air supply port 12 at a ratio of m ³ / H, the rotary shaft 9 was rotated at a speed of 3 rotations per minute to rotate the alumina balls, and the simulated concentrated waste liquid was dried. As a result, the powder 15 extracted from the powder outlet 16a is a dry powder having a water content of 1% or less,
The amount of dry powder contained in the exhaust gas discharged from the exhaust port 17 was 1% or less of the powder 15.

The present invention is not limited to the above apparatus. For example, by using the ceramic material as the spherical body 7 as described above, a processing apparatus having excellent corrosion resistance can be obtained. You may use the thing made from a metal or resin. Further, as the hot air supplied from the air supply port 12, air heated by utilizing waste heat of exhaust gas generated from other equipment or the exhaust gas itself may be used.

As described above, according to the present invention, since the structure of the processing apparatus is simple and there is no portion that rotates at high speed and slides at high speed, the first required failure as a processing apparatus for radioactive waste is small and maintenance is troublesome. The treatment can be performed by a device that does not cost much and the reduction of radiation exposure can be achieved. In addition, the spherical body is pressed and driven by a plurality of horizontally extending stirring blades reaching the vicinity of the inner wall surface of the main body to roll, and the entire spherical body deposited layer is stirred to ensure good contact with high temperature gas. High thermal efficiency is achieved, and the sliding contact of the rolling spherical body ensures that the powder adhering to the surface of the spherical body is separated, and the powder is an apparatus such as the inner surface of the main body, the stirring blade, or the spherical body itself. It is possible to perform the treatment continuously for a long period of time because the adhesion and growth of the inner portions are prevented. Further, since the high-temperature gas is supplied from the air supply port provided below the support plate and fed into the spherical deposit layer through a large number of holes in the support plate, the distribution of the high-temperature gas flow in this deposit layer is It is possible to homogenize and evenly heat the various parts of the sedimentary layer to reliably pulverize radioactive waste without wasting high temperature gas. It is possible to prevent the body from blocking the hole in the support plate.

Furthermore, since the dry surface area formed by the surface of many spherical bodies is large and the radioactive waste is directly heated by the high temperature gas, the processing capacity is large even with a small equipment, and the radioactive waste liquid before concentration can be directly processed. Can be made into powder,
In addition, the necessary adjustment range of boric acid and sodium hydroxide when treating the radioactive liquid waste generated from a pressurized water nuclear power plant will be relaxed. In addition, there is no generation of secondary waste liquid such as condensed water associated with the treatment, and its treatment is unnecessary. Furthermore, since the powder falls and accumulates in the powder reservoir at the bottom of the container by its own weight, it can be easily taken out from the outlet at any time, and a separate device for powder recovery is not required. The overall size is small and simple, and operating costs are low.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a radioactive waste processing apparatus showing an embodiment of the present invention. 3 ... Pump, 4 ... Processing device, 5 ... Main body, 6 ... Support plate, 7 ... Spherical body, 8 ... Rotation drive mechanism, 9 ... Rotation shaft, 10 ... Stirring blade, 11 ... Stirrer, 12 ... Air supply port, 13 ... Hot air generator, 14 ... Radioactive waste supply port, 16 ... Powder reservoir, 16a ... Powder outlet, 17
...... Exhaust port, 19 ...... Exhaust fan.

Claims (2)

[Claims] 1. A radioactive radioactive waste generated in a radioactive material handling facility is placed on a large number of spherical bodies deposited in a vertical cylindrical container having a supporting plate having a large number of holes. The spherical body is supplied, and the base is fixedly attached to a vertical rotating shaft, the base extends, extends horizontally, and is pressed and driven by a plurality of stirring blades whose tips reach the vicinity of the inner wall surface of the container. Of the high temperature gas supplied to the lower part of the sphere is caused to flow upward in the deposition layer of the spherical body through the hole,
The radioactive waste is heated by the high-temperature gas to form a powder, and the powder is dropped and accumulated from a hole in the support plate into a powder reservoir provided at the bottom of the container. How to dispose of things. 2. A vertical cylindrical container-shaped main body having a support plate having a large number of holes therein, a large number of spherical bodies deposited on the support plate, and a tip portion extending horizontally and having the main body. A plurality of agitating blades that reach the vicinity of the inner wall surface of the agitator are fixed to a vertical rotating shaft, a radioactive waste supply port opening above the spherical body, and the main body below the supporting plate. A high-temperature gas supply port provided in, and an exhaust port provided in the main body above the deposition layer of the spherical body,
An apparatus for treating radioactive waste, comprising a powder reservoir provided at the bottom of the main body below the support plate.