JPS6341438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in a radioactive waste solidification method and apparatus, and in particular to a radioactive waste solidification method and apparatus suitable for application to waste with high radioactivity concentration. Regarding.

Radioactive waste ultimately needs to be solidified in a container (drum) and transported to a processing site. During transportation, it is necessary to keep the surface dose of the container below a specified amount in order to reduce the radiation exposure of workers. Therefore, when the radioactivity concentration is high, concrete should be injected as a shield and solidified to reduce the surface dose rate, or before solidification into drums.
It is necessary to store it for a long time to attenuate its radioactivity.
In the former case, the number of drums generated increases, and in the latter case, a facility is required to store the waste in a stable state for a long time.

The present invention was developed in view of the above-mentioned problems, and its purpose is to solidify waste with high radioactivity concentration in a container without storing it for a long time, and to maintain the dose rate on the surface of the container at a specified level. At the same time, the objective is to increase the amount of radioactivity that can be filled into a container compared to the conventional method.

The solidification method that achieves the object of the present invention is characterized by solidifying radioactive waste in a container, dividing the radioactive waste into two or more types according to radioconcentration, and out of the divided radioactive waste. The purpose is to place radioactive wastes with higher radioactivity concentrations in the center of the container and to solidify these radioactive wastes.

In addition, solidification equipment is characterized by equipment that solidifies radioactive waste in containers, and equipment that separates radioactive waste into two or more types based on radioactivity concentration, and equipment that converts the separated radioactive waste into powder. a device for mixing this powder with a solidifying agent to form it into pellets; and a means for placing the pellet with the highest radioactivity concentration in the center of the container;
The present invention is comprised of means for arranging the remaining pellets so that the radioactivity concentration gradually decreases from the center of the container to the wall surface of the container, and a device for solidifying each of the pellets.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In this example, concentrated waste liquid generated from a BWR power plant will be described.
It can also be applied to used resins such as powdered resin and granular resin, incineration ash, and laundry waste. The ion exchange resin used for water purification in the reactor primary cooling system is concentrated every month using dilute sulfur and caustic soda and stored in the concentrated waste liquid tank 1 shown in FIG. Most of the radioactivity in this concentrated waste liquid is present in the iron rust generated at the same time as the ion exchange resin is regenerated. Therefore, the concentrated waste liquid is transferred to the separation tank 2, and the iron rust is sedimented and separated in the lower part of the separation tank 2 by utilizing the density difference between the iron rust and the sodium sulfate. The concentrated waste liquid from which the iron rust has been separated is sent from the separation tank 2 to the centrifugal membrane dryer 3 for drying by opening only the valve 9. After drying the powder, epoxy resin is added from the binder tank 11, and the powder is pressure-molded into pellets using the granulator 4. After the pellets are put into a wire gauze 6 of a drum 5 serving as a container, a small container 7 is placed vertically above the pellet layer. A shutter 8 is joined to this small container 7.
Next, the valve 9 is closed and the valve 10 is opened, and the slurry of iron rust is turned into a dry powder by the centrifugal film dryer 3. After adding epoxy resin to this powder from the binder tank 11, it is molded into almond-shaped pellets by the granulator 4. This iron rust pellet removes the shutter 8, closes the valve 10 and opens the valve 9. Then, as in the beginning, pellets with lower radioactivity concentration than the pellets in the small container 7 are produced from the concentrated waste liquid, and the remaining space of the wire mesh 6 is filled with the produced pellets. When the weight of pellets in the drum 5 reaches a predetermined weight, the drum 5 is moved. This drum is kept in a constant temperature bath at a predetermined temperature for 24 hours, and then asphalt is injected into it. After cooling to room temperature, more asphalt is reinjected to compensate for the shrinkage of the asphalt.

By the way, in a drum made of solidified asphalt and radioactive waste, the distance at which the gamma ray intensity is halved is approximately 8 cm. Now the radius of 200 drums is about 25cm
, then γ generated from the center of the drum is
The line strength becomes 1/8. Therefore, by concentrating radioactivity with high concentration in the center, the total amount of radioactivity that can be injected into, for example, 200 drums with a radius of 25 cm can be increased four times compared to the conventional method.

FIG. 3 shows an embodiment of the present invention.
Radioactive waste is solidified using a three-layer structure, with iron rust powder resin and concentrated waste liquid in descending order of radioactivity level. The iron rust separated from the powdered resin and concentrated waste liquid is dried into powder using a centrifugal membrane dryer, then mixed with polyester resin, which is a type of thermosetting resin, in a 1:1 ratio, and placed in a small drum can 14. Let it solidify. This small drum 14 is supported by 15
It is placed in the center of the medium-sized drum 13 by. Next, dry powders of polyester resin and powdered resin are mixed in a one-to-one ratio and filled into a medium-sized drum 13. Similarly, powder produced from concentrated waste liquid is mixed with polyester resin and injected into a large drum 12 in which a medium-sized drum 13 is placed in the center with a support 16. According to this embodiment, the distance from the iron cladding, which has the highest radioactivity concentration, to the surface of the drum can be further increased, and the amount of radioactivity to be filled can be increased.

FIG. 4 shows a case where the present invention is applied when the amount of iron rust is small and the specific radioactivity of the iron rust is high when iron rust is separated from the concentrated waste liquid. The iron rust solidifies inside the lead shield 18 of the small drum 17, which is centered by the support 19 on the large drum 20. Thereafter, the solidified material obtained by treating the concentrated waste liquid is charged into the large drum can 20, and the small drum can 17 is surrounded with this solidified material.

The invention is also applicable to the treatment of radioactive waste generated from PWR nuclear power plants, ATR nuclear power plants and nuclear fuel reprocessing plants.

According to the present invention, waste with high radioactivity concentration can be solidified in a container without being stored for a long period of time, and the amount of radioactivity that can be filled into the container can be increased.

[Brief explanation of the drawing]

Fig. 1 is a flow diagram of radioactive waste showing one embodiment of the present invention, Fig. 2 is an explanatory diagram of a method for solidifying waste in a drum, and Fig. 3 is a diagram showing a method of solidifying waste in a drum, which is another embodiment of the present invention. Fig. 4 is an explanatory diagram of a method for solidifying waste into a drum when the radioactivity concentration is high. 2... Separation tank, 3... Centrifugal membrane dryer, 4... Granulator, 5... Drum, 7... Small container.

Claims (1)

[Claims] 1. In an apparatus for solidifying radioactive waste in a container, the radioactive waste is divided into two or more types according to differences in radioactivity concentration, and the radioactive concentration of the divided radioactive waste is A method for solidifying radioactive waste, characterized in that radioactive waste with a higher value is placed in the center of a container, and the radioactive waste is solidified with a solidifying material. 2 For solidifying radioactive waste in containers, there is a device that separates the radioactive waste into two or more types according to radioactivity concentration, a device that turns the separated radioactive waste into powder, and a device that converts this powder into powder. A device for mixing the pellets with a solidifying agent and forming them into pellets; a means for placing the pellets with the highest radioactivity concentration in the center of the container; 1. An apparatus for solidifying radioactive waste, comprising means for arranging the pellets so that the concentration thereof gradually decreases, and a device for solidifying each of the pellets described above.