JPS6042698A - Method of vitrifying radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vitrifying radioactive waste generated from nuclear power plants (BWR) and the like.

Conventionally, combustible waste and used ion exchange resins generated at nuclear power plants are incinerated in an incinerator to reduce their volume, and the incinerated ash is directly canned in drums. In addition, since it is difficult to store concentrated waste liquid for a long time in its current form (liquid), it is mixed with cement or asphalt and then poured into drums1) to form a solidified product. By the way, these radioactive wastes are scheduled to be disposed of on land or in the ocean in the future.

Therefore, they will be stored in the facility for a long period of time until they are disposed of. Therefore, some kind of treatment is performed to turn the radioactive waste into a solidified substance that has an excellent volume reduction ratio, is chemically and physically stable, is resistant to heat, and does not leak the radioactive substances contained inside. is desirable. Here, the volume reduction ratio is the ratio of the volume after treatment to the volume before treatment, and an excellent volume reduction ratio means that this value is small. However, according to conventional radioactive waste disposal methods, incinerated ash is packed directly into drums, so if the drums break, the incinerated ash may scatter, causing radioactive contamination). There was a seven-year problem with concentrated waste liquid.

The purpose of the present invention is to solve such problems, and the present invention aims to solve these problems by combining the dried solid content of concentrated waste liquid of radioactive waste generated from nuclear power plants, etc., (2) an auxiliary agent mainly composed of 5in2, and graphite, etc. The mixture is mixed with a reaction accelerator whose main component is carbon, the mixture is melted at high temperature in a melting furnace, and the resulting glassy material is filled with radioactive materials and poured into a container where it solidifies. This objective is achieved by providing a method for vitrifying radioactive waste, which enables radioactive waste to be converted into a vitrification method that has excellent volume reduction ratios, is chemically and physically stable, and is resistant to heat. It can be made into a vitrified material that does not leak radioactive substances.

The method of the present invention will be explained in detail below based on the drawings showing embodiments thereof. In the figure, (1) is radioactive concentrated waste liquid (approximately 20 to 25% solid waste) generated from nuclear power plants.
(most of which is Na25o4) in a dryer (not shown)
Dry salt obtained by drying (Tada), incineration ash and clay obtained by incinerating combustible waste and used ion exchange resin etc. generated at nuclear power plants in an incinerator (not shown). (3) is a reaction accelerator (3) whose main component is a return element such as graphite. 1) is a dry salt hopper into which the auxiliary agent (2) is fed, (5) is an auxiliary agent hopper into which the auxiliary agent (2) is fed, and (6) is a reaction accelerator hopper into which the reaction accelerator is fed, each with a feeder at the lower end. (7) (8) (9
) is provided. C1 is each hopper (4) (5)
Dry salt (1), auxiliary agent (2) and reaction accelerator (3) fed from (6) through feeder (7) (8) (9)
) to a predetermined mixing ratio, a weighing hopper, 0
1) is a mixer for mixing weighed dry salt (1), auxiliary agent (2) and reaction accelerator (3) in a weighing hopper (10), @
is a supply hopper into which the mixture discharged from the mixer (11) is fed, and a screw feeder α3 is provided at the lower end of the supply hopper On. The α unit is a melting furnace to which a mixture is continuously supplied from the supply hopper through the screw feeder, and the molten glass produced in the melting furnace α is poured into the melting furnace to solidify it. Assimilation vessel, (17) is S02°C02 generated in the melting furnace α leakage.
Indicates exhaust gas such as

With this configuration, first, dry salt (1), auxiliary agent (2), and reaction accelerator (3) are sequentially supplied from each hopper (4) (5) (6) to weighing hopper a1, and the mixture is adjusted to a predetermined mixing ratio. Weigh it so that it is.

(4) At this time, since the ratio of each component has a great influence on the properties of the glass produced by melting and solidification, the mixing ratio must be within a certain range. First of all, the amount of auxiliary agent (2) is 1 to 2 times the amount of dry salt (1).

If the amount of auxiliary agent (2) is less than this, unreacted dry salt (1) will remain during melting, and on the other hand, if the amount of auxiliary agent (2) is more than this, sufficient vitrification reaction will not occur. . The clay used as the auxiliary agent (2) preferably contains about 5 to 20% of a stable oxide such as alumina in order to improve the properties of the glass. In addition, an auxiliary agent that mixes clay and incineration ash (
In the case of 2), the mixing ratio of incinerated ash is limited to 30% of the weight of the auxiliary agent (2) after mixing. Incineration ash is mainly composed of S t O2 and the rest is Fe 20.5, ]fun 3()□
Since it is a stable oxide such as, it is incorporated into the network structure of the glass that is produced and serves to improve the properties of the glass.

Next, the wax of reaction accelerator (3) such as graphite is mixed with dry salt (1).
It is sufficient to use about 5 to 20% of the weight of .

If graphite is not added, the melting reaction requires over 1400'C, whereas with graphite, the melting reaction is approximately 1200'C.
℃, which is effective in lowering the reaction temperature and increasing the reaction rate (5). When the measuring hopper αQ finishes measuring the mixture to achieve such a mixing ratio, the entire amount is discharged to the mixer 01) and thoroughly mixed. After this, supply hopper (2)
, the mixture is continuously fed to the melting furnace 04 through the screw feeder (to). The mixture melted at high temperature in the melting furnace (b) becomes molten glass αQ. Therefore, this molten glass αe is poured into a solidification container αG and solidified. The exhaust gas aη generated during melting is treated in an exhaust gas treatment facility (not shown).

Next, an experimental example will be given. Mixing ratio: 36% dry salt
, incineration ash 5%, clay (auxiliary agent) 54%, black red reaction accelerator)
Mixed at 5%. Its composition is 5in246'l in weight R%
lJ, Na2SO4 36%, oxides such as alumina 13%
, C5%. This mixture was thoroughly mixed with a mixer until it became homogeneous. This is because if the mixing is insufficient, the resulting glass will be inferior.

The entire amount of the mixture discharged from the mixer to the supply hopper (2) was continuously supplied to the melting furnace (2) by the screw feeder (2). Especially screw feeder (to) as a feeder
The reason why a screw feeder was used is that unlike a vibrating feeder, etc., a screw feeder generates less vibration and is less likely to separate the mixture. The melting furnace (14) used was an electric melting furnace using electroformed bricks on the molten glass contact surface. here,
Upon melting the mixture at approximately 1200'C, a glass was produced by the reaction described below.

Na SO+nSiO2+mMOx+C+-H02-=
4 Na ()mMOx-nsi02+S02↑+CO2↑
Here, mMOx is a stable oxide, Na2O・ITI
MOX-nSiO2 is the glass produced. The generated molten glass ullG is S02. generated during the reaction. C02
After gas Q7) was degassed and clarified, it was poured into a solidification container αQ and solidified. Further, SO2 and CO2 gas Q71 were treated with exhaust gas treatment equipment. No molten glass! The composition of is Sin2
6m, Na2O21%, stable oxide 16%. JIS-
When the alkali elution test specified in R-3502 was conducted, the amount of alkali elution was 2.1 mg, and it was found that the performance was equivalent to or better than that of ordinary glass.

As described above, according to the method of the present invention, the radioactive waste to be treated can itself be used as a part of the solidification agent, and SO2 and CO2 can be released during melting (7), resulting in vitrification with an excellent volume reduction ratio. You can get a body. In addition to radioactive concentrated waste liquid generated from nuclear power plants,
Incineration ash from combustible waste can also be made into glass assimilate at the same time, which is very rational. Moreover, the obtained vitrified material is chemically and physically stable, resistant to heat, and there is little risk of leaking the radioactive substances contained inside.

[Brief explanation of the drawing]

The drawing is a flow diagram showing one embodiment of the present invention. (1)...Dry salt, (2)...Auxiliary agent, (3)...
Reaction accelerator, αη...mixer, 0→...melting furnace, a
G...Assimilation container agent Yoshihiro Morimoto (8)

Claims (1)

[Claims] 1. Mix the dry solid content of concentrated waste liquid of radioactive waste generated from nuclear power plants, etc., an auxiliary agent mainly composed of SiO2, and a reaction accelerator mainly composed of carbon such as graphite. A method for vitrifying radioactive waste, which is characterized by melting a mixture at a high temperature in a melting furnace, and pouring the resulting gas-like material into a container to solidify it, simulating a radioactive substance encapsulated therein.