JPS63253298A - Method of processing radioactive washing waste liquor - 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 [Field of Industrial Application] The present invention relates to a method for treating radioactive laundry waste liquid, and in particular, a radioactive washing method suitable for powdering and granulation treatment of highly foaming detergent-containing radioactive waste liquid. Concerning a waste liquid treatment method.

[Conventional technology]

At nuclear power plants and other facilities, radioactive waste liquid mixed with detergent is generated when working clothes are washed. Conventionally, approximately 115
After concentrating and reducing the volume to 0.00, it is stored by solidifying with cement. In order to further reduce this storage amount, it is reasonable to remove and reuse the contained water and discard only the surfactant.

Evaporative drying treatment is used to separate and remove moisture. However, since the surfactant is a highly viscous substance, it is extremely difficult to powder and granulate it, and the surfactant has foaming properties, which causes impurities to flow into the steam when powdered. This causes problems such as the separated water becoming contaminated. In other words, DF(
Supply side impurities/steam side impurities) are reduced.

According to Japanese Patent Publication No. 60-38680, in order to suppress the above-mentioned properties of surfactants when treating laundry waste liquid alone,
It has been discussed that pulverization becomes possible by adding an adsorbent such as activated carbon to the waste liquid to physically adsorb the surfactant.

[Problem that the invention seeks to solve]

In the above-mentioned prior art, the problem of foaming of the surfactant during drying was solved by adding an adsorbent such as activated carbon, but no consideration was given to granulation properties.

Pellets (granules) produced by conventional techniques have a low specific gravity and have a problem with volume reduction properties.

This method uses a large amount of activated carbon or zeolite as an adsorbent to physically adsorb the surfactant, which has the problem of increasing the amount of waste.Furthermore, the specific gravity of these adsorbents is light and Since it is a substance with poor granularity, its specific gravity is small even when granulated, resulting in further reduction in volume reduction properties.

In order to improve volume reduction performance, we considered using a silicone antifoaming agent that has an antifoaming effect in small amounts, but both the antifoaming agent and the surfactant are highly viscous substances, and There was a limit to the mixing amount due to the phenomenon that powdering and granulation was difficult.

The purpose of the present invention is to eliminate foaming without using an adsorbent and to reduce the DF during drying.
It is an object of the present invention to provide a method for treating radioactive laundry waste liquid that improves the quality of radioactive laundry waste and has excellent volume reduction properties and granulation properties.

[Means for solving problems]

In order to achieve the above object, the present invention adds a water-soluble salt compound of an alkaline earth metal and a mineral acid.

By reacting a surfactant with an alkaline earth metal to form a precipitable salt compound, foaming caused by the surfactant is suppressed, and washing waste liquid and other waste liquids (boric acid waste liquid, sodium sulfate waste liquid, sodium nitrate waste liquid) are This paper proposes a method to minimize the influence of surfactants by mixing waste liquid, etc.) to produce a powder suitable for granulation.

That is, the objective is achieved by adding 10% by weight or more of a water-soluble salt compound of an alkaline earth metal and a mineral acid to the detergent component in the laundry waste liquid.

[Effect]

Since surfactants have hydrophilic and hydrophobic groups, they are adsorbed and oriented to the gas-liquid interface, forming a monomolecular film and lowering the surface tension. Laundry waste liquid contains this surfactant, so it has a low surface tension and is easy to foam.By adding an alkaline earth metal, it reacts with the anionic group (long chain alkyl of fatty acid) of the surfactant, and the solution becomes muffled. It becomes a precipitable salt with a low degree of precipitation, which prevents the formation of a singleton film and prevents a decrease in surface tension.

Due to the above action, bubbles do not move to the steam side, and DF is improved.

In addition, by using precipitable salts, highly viscous substances can be more easily solidified, so when mixed with other waste liquids, it is possible to increase the amount of laundry waste liquid mixed in, and it has excellent volume reduction properties. This is a new processing method.

〔Example〕

When radioactive laundry waste containing detergent was treated with a water-soluble salt compound of alkaline earth metals and mineral acids in a centrifugal thin film dryer, foaming disappeared during drying, and the D
F became equivalent to the waste liquid that did not contain detergent. Furthermore, when the resulting powder was granulated using a granulator, pellets with good physical properties were created.

The present invention was made based on the results of this experiment. The results of this experiment are shown below.

Figure 2 shows the results of a study on the appropriate amount of alkaline earth gold Bc salt to be added to detergents.

It shows the relationship between the amount of alkaline earth metal salt added to detergent and the concentration of detergent transferred to the distillation side during distillation.

As is clear from FIG. 2, it was found that if 10% by weight or more of detergent was added to the detergent, the detergent concentration transferred to the distillation side could be kept significantly low.

Based on the above results, one or more of the alkaline earth metal salts should be mixed in the minimum amount to achieve the defoaming effect (there may be slight differences depending on the type of alkaline earth metal salt), and the heat transfer surface roughness should be 1.2 d. It was supplied to a centrifugal thin W4 dryer at a flow rate of 50 kg/hr, and subjected to evaporation drying.

The result of granulating the above powder using a tablet machine (tablet type granulator) is shown in FIG.

The relationship between the detergent concentration in the total solid content and pellet strength (relative ratio) will be shown. As is clear from FIG. 3, the pellet strength tends to decrease as the detergent concentration increases in the total solid content. Furthermore, if a large amount of detergent is contained beyond the limit, the pellets will buckle during granulation, making it impossible to mold them. From the results of this experiment, the concentration of detergent in the total solid content of the waste liquid was 16
It was found that granulation was possible if the amount was less than % by weight.

Specific examples are shown below.

<Example 1> Embodiment 1 of the present invention will be explained based on FIG.

A boric acid waste liquid 2 and a washing waste liquid 1 containing a surfactant are mixed in a supply tank 5 to form a 10% by weight waste liquid. Barium chloride 3 is added to the supply tank 5 in a predetermined amount necessary for defoaming.

(In the case of this example, barium chloride was added in an amount of 45% by weight based on the amount of detergent.) The detergent was mixed in such a way that 16% by weight of the fixed amount of the prepared waste liquid was detergent.

1. Supply the above waste liquid to a 2-pot dryer 5o.

It was dried and powdered at a rate of 50 kg/hr. The solid content of the steam is removed by a mist separator 11, liquefied by a condenser 12, and returned to the concentrator. The generated powder is transferred to powder hopper 6
After being mixed with the binder in the binder hopper 7 in the granulator 8, it is molded into a cylindrical shape (φ28×28t). The molded pellets are weighed in a hopper 9 and filled into a drum 1°0.

When we sampled A and B in Figure 1 and measured the decontamination coefficient of the dryer 50, we found that the decontamination coefficient was 7 compared to before adding the antifoaming agent.
It's doubled.

In addition, the generated pellets do not buckle during granulation,
The pellets had sufficient specific gravity and strength.

Furthermore, since foaming has been completely suppressed, the amount of detergent that migrates to the mist separator and condenser side with steam is reduced.
It was possible to significantly reduce the amount of water and prevent any adverse effects on the concentrator after liquefaction.

<Example 2> The second embodiment will be explained based on FIG. 4.

A boric acid waste liquid 2 and a washing waste liquid 1 containing a surfactant are mixed in a supply tank 5 to form a waste liquid having a solid content of 10ffi%. Barium chloride 3 is mixed into the supply tank 5 and defoamed. The resulting waste liquid was mixed so that 16% by weight of the solid content was detergent.

The waste liquid is sprayed and supplied to a calciner 13 having a fluidized bed in which air in which assimilated particles (fluidized medium) on the hearth are heated by a heater 16 is suspended by a calciner gas blower 17 . The spray droplets dry on contact with the fluidizing medium.

The calcined product adheres to and forms a envelope on the surface of the fluid medium. As a result, the vJa bodies grow and produce small pieces due to mutual collisions and the like. Among these, fine particles are discharged out of the furnace along with the air current, and the solid content is captured by the cyclone separator 18 and collected in the powder hopper 6. After being granulated into pellets by a granulator 8 and filled into a pellet hopper 9, the pellets are filled into a drum 10. Further, the solid content is decomposed in the scrubber 19 and liquefied in the condenser 21.6 According to this embodiment, the bubbles are not entrained into the air layer and are pulverized, and the generated powder is used during granulation. without buckling,
It was possible to mold sufficient pellets in both specific gravity and strength as in the conventional method.

<Example 3> In Examples 1 and 2, round-shaped pellets were produced using a doublet-type granulator, but similar effects can be obtained by granulating the pellets into an almond-shape using a briquette-type granulator.

<Example 4> In Example 1.2, boric acid waste liquid, which is the main component of concentrated waste liquid generated from a PWR power plant, and laundry waste liquid were mixed and treated, but other waste liquids (sodium sulfate waste liquid, sodium nitrate waste liquid, A similar effect can be obtained with resin).

<Example 5> In Examples 1 and 2, barium chloride was used as an additive, but the same effect can be obtained if it is a water-soluble salt compound of an alkaline earth metal and a mineral acid. . The amount added may be equimolar to the barium chloride used in this experiment.

〔Effect of the invention〕

According to the present invention, by adding a water-soluble salt compound of an alkaline earth metal and a mineral acid, foaming during drying can be suppressed, so that there is an effect of improving the pF of the dryer.

In addition, the amount of detergent mixed with the solid content can be up to 16% by weight.
Pellets with excellent volume reduction properties can be granulated.

[Brief explanation of the drawing]

Figure 1 shows a process flow showing an example of the configuration of a volume reduction treatment facility for carrying out the method of the present invention, and Figure 2 shows the amount (relative ratio) of alkaline earth metal salt added to the detergent and the amount transferred to the distillation side during distillation. Figure 3 is a diagram showing the relationship between the detergent concentration in the total solid content of the waste liquid and the relative pellet strength ratio, and Figure 4 is the volume reduction treatment for carrying out the method of the present invention. It is a process flow which shows another example of a structure of equipment. 4... Auxiliary tank, 13... Calciner, 50... Dryer.

Claims (1)

[Claims] 1. A step of adding a water-soluble salt compound of an alkaline earth metal and a mineral acid to a radioactive waste liquid containing at least a washing liquid to change detergent components into precipitable salts, and a step in which the salts are mixed. A method for treating radioactive laundry waste liquid, which comprises the steps of: concentrating and drying the radioactive waste liquid by heating and turning it into powder; and granulating the generated powder. 2. Claim 1, characterized in that the radioactive waste liquid is a waste liquid that is a mixture of the radioactive laundry waste liquid and other radioactive waste liquid such as boric acid waste liquid, sodium sulfate waste liquid, sodium nitrate waste liquid, etc. How to dispose of radioactive laundry liquid. 3. The radioactive laundry waste liquid according to claim 1 or 2, wherein the amount of the water-soluble salt compound added is 10% by weight or more based on the detergent component of the radioactive laundry waste liquid. Processing method. 4. In any one of Claims 1 to 3, the pulverization treatment step includes a rotating blade for transferring the radioactive laundry waste mixed with the water-soluble salt compound and other radioactive waste. From the step of supplying the radioactive waste liquid to a container that has a rotating shaft inside and having a heating means on the outer periphery, and rotating the rotating shaft while heating the radioactive waste liquid in the container with the heating means to powderize the radioactive waste liquid. A method for treating radioactive laundry waste liquid, which is characterized by: 5. In any one of claims 1 to 3, the pulverization treatment step comprises heating fixed particles of the radioactive laundry waste liquid mixed with the water-soluble salt compound and other radioactive waste liquid. A method for treating radioactive laundry waste liquid, comprising the steps of supplying the radioactive waste liquid into a calciner having a fluidized medium layer suspended from below by air, and bringing the radioactive waste liquid into contact with the fluidized medium to pulverize it.