JPH0254919B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for solidifying radioactive waste, and more particularly to a method for solidifying powdery radioactive waste using a vitreous binder. Among the radioactive waste generated at facilities that handle radioactive materials such as nuclear power plants, combustible miscellaneous solid waste such as polyethylene sheets, rags, paper, and wood are generally reduced in volume to 1/50 to 1/100 by incineration. Incineration ash is stored in drums. In addition, most of the slurry-like combustible waste such as waste ion exchange resin and filter sludge is currently stored in tanks, but volume reduction methods such as incineration are being developed to save storage space. It is thought that incineration ash will be generated in the future. A method has also been developed for separating and collecting the crud generated in the cooling water pipes of nuclear power plants and recovering it as a slurry, which can be dried to form powdered crud.
Furthermore, it is also possible to pulverize the concentrated waste liquid by heat drying treatment or the like. Among these particulate radioactive wastes, the unburned content of incinerated ash is approximately 5% or less, the main component of clay is iron oxide, and the powder of concentrated waste liquid is sodium sulfate or sodium borate. All of these wastes are inorganic or almost inorganic and therefore chemically stable; however, storing these wastes in powder form in containers such as drums is not recommended (a) Because they are dry powders, they may not scatter. Cheap. (b) High leachability to water. (c) Low bulk density and large storage space required. It has the following problems. This invention solves the above-mentioned problems and provides a method for solidifying powdery radioactive waste by solidifying it with a glassy binder, making it a stable solidified product, and achieving volume reduction. That is. However, the gist of this invention is to mix powdery radioactive waste with glass frit, fill the resulting mixture into a graphite mold consisting of a body and a bottom that is removable from the body, An upper mold made of graphite is inserted into the body, and while pressurizing the mixture, the mixture is heated to a temperature higher than the softening point of the glass frit using a heating device, and then the mixture is cooled to convert the waste into a glassy substance. A method for solidifying radioactive waste, characterized by obtaining a solidified body solidified with a binder. This invention will be explained in more detail below with reference to FIG. Powdered radioactive waste 1 such as incineration ash is fed from a waste feeder 3a into a mixer 2 with a weighing function, where it is mixed in a predetermined manner with glass frit 4 fed from a frit feeder 3b. The resulting mixture 5 is filled into a graphite mold 8 consisting of a cylindrical body 6 and a bottom 7 with the lower end of the body removably closed. Filled mixture 5
is pressurized downward by a graphite upper mold 10 driven by a hydraulic cylinder 9 and inserted into the body 6,
The mold 8 is filled with pressure. This filling operation can be carried out by supplying the mixture 5 necessary for one solidified material at once, or by dividing it into several parts and applying pressure using the upper die 10 each time it is supplied. ,
According to the latter method, the height of the mold 8 can be reduced, and the solidified body can be made smaller and more dense. The mixture 5 filled in the mold 8 is pressurized by the upper mold 10 and surrounds the body 6, which can individually control the temperature of the upper, middle, and lower zones to make the temperature distribution uniform in the height direction. electric heater 11
The glass frit 4 in the mixture 5 is heated by
is softened and further consolidated. After that, if the waste is cooled by leaving it in the mold 8, a solidified waste 12 bonded by glass frit is obtained in the mold 8, and is moved downward by the upper mold 10 while lowering the elevating table-type solidified material removal device 13. Extrude the above solidified body 1
2 from the body 6. In order to smoothly take out the solidified material 12, it is preferable that the inner surface of the body 6 has a tapered shape that expands in diameter downward. In addition, in order to prevent oxidative consumption of the graphite mold 8 and upper mold 10 during heating, it is preferable to purge the inner and outer surfaces of each mold, especially the mold 8, with an inert gas such as nitrogen. It is supplied into the apparatus through supply ports 15 and 16 provided in the furnace body 14 surrounding the mold 8, and is discharged to the outside through exhaust ports 17 and 18. If a glass frit with a low softening point of 600°C or less is used in the above process, the operating temperature of the solidification equipment can be kept low, which will prevent the volatilization of radionuclides and extend the life of the equipment. There are many advantages. In the above-mentioned solidification device, by making the mold 8 consisting of the body part 6 and the bottom part 7, and the upper mold 10 made of graphite, it is possible to prevent the glass frit from sticking to each mold and to reduce the wear of each mold. , the mold 8 and the radioactive material 10 can be made of steel with a graphite lining on the surfaces that come into sliding contact with each other and the surfaces that come into contact with the mixture 5, etc., to obtain similar effects, and the term "made of graphite" in this invention shall also include such a structure partially using graphite. Example Waste consisting of incineration ash obtained by actually incinerating simulated waste ion exchange resin and filter sludge mixed with iron oxide fine powder, and a simulator of cladding using fine iron oxide powder, which is the main component of cladding. and aluminum phosphate-based low softening point glass frit with a softening point of approximately 500°C, and mixer 2 mixes 0.6 to 1.0 glass frit per incineration ash and waste 1.
After mixing at a weight ratio ^of An inorganic solidified body with a length of 300 mm was obtained. The properties of these solidified bodies are shown in Table 1. As is clear from the table, the bulk density of the obtained solidified material is 2.7 to 2.9.
Unconfined compressive strength is 650-900Kg/cm ² , C _s leaching rate is 42
The value after 7 days is 7×10 ^-4 to 5×10 ^-3 g/cm ²・day, and the volume reduction ratio relative to the state before solidification is approximately 1/
It was 2 to 1/2.5.

[Table] The main effects of this invention are as follows. Radioactive waste incineration ash, etc., which is powdery and easily scattered, can be solidified with a glassy binder to form a stable inorganic solidified body. It is possible to densify and reduce the volume of radioactive waste, etc., which is powdery and has a low bulk density. Since graphite molds and upper molds are used, it is possible to prevent the glass frit from sticking to each mold, making it extremely easy to release the molds, and furthermore, there is little wear on each mold. Since the solidified material is obtained as a single solidified material rather than being solidified integrally with a container, the container is not required and it is economical, and the solidified material has a desired size and shape that is convenient for storage and disposal. can get. By using a glass frit with a low softening point, the operating temperature can be kept low and the life of the device can be extended.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an example of a solidification apparatus used for carrying out the method of the present invention. 1... Powdered radioactive waste, 2... Mixer, 4
... Glass frit, 5 ... Mixture, 6 ... Body, 7 ... Bottom, 8 ... Mold, 9 ... Hydraulic cylinder, 10 ... Upper mold, 11 ... Electric heater, 12 ...
...solidified body, 14...furnace body, 15...supply port, 1
6... Supply port, 17... Exhaust port, 18... Exhaust port.

Claims (1)

[Claims] 1. Powdered radioactive waste is mixed with glass frit, the resulting mixture is filled into a graphite mold consisting of a body and a bottom that is removable from the body, and the mixture is poured into the body. A graphite upper mold is inserted and the mixture is pressurized while being heated by a heating device to a temperature above the softening point of the glass frit, and then the mixture is cooled and the waste is bonded with a vitreous binder. A method for solidifying radioactive waste, characterized by obtaining a solidified solid. 2. The method for solidifying radioactive waste according to claim 1, wherein the glass frit has a softening point of 600°C or lower. 3. Claim 1 or 2, wherein the mixture is filled into the mold by feeding the mixture into the mold several times and pressurizing it with the upper mold each time it is fed. method of solidifying radioactive waste. 4. The method for solidifying radioactive waste according to claim 1, 2, or 3, wherein the inner and outer surfaces of the mold are purged with an inert gas when the mixture is heated by the heating device.