Method of processing liquid low-activity level radioactive wastes

FIELD: radioactive waste treatment.

SUBSTANCE: suspension of magnetite obtained via electroerosion dispersing of iron-containing raw material in distilled water is added to solution to be processed. Adjusting pH of solution to 11-12 leads to precipitation. Decanted solution is subjected to magnetic separation followed by ion-exchange purification.

EFFECT: enhanced purification efficiency.

3 cl, 1 tbl

 

The invention relates to a method for processing liquid radioactive waste (LRW) low level of activity, containing suspended and colloidal impurities, and can be used mainly in nuclear power and reprocessing plants. The invention can be used for wastewater treatment from radionuclides.

Known methods of water purification, including coprecipitation with iron hydroxide with subsequent purification of decantate ion exchange [Assocition, WEA, Mijikai. Disposal of radioactive waste. M.: Energoatomizdat, 1985]. The disadvantages of this method are the formation of a large volume hydrate-sludge slurry that you want to localize, increasing the concentration of salts in decantate that reduces cycle ion exchange columns and water quality from radionuclides.

Closest to the present invention is a method of water purification magnetite obtained EDM dispersion of ferrous metals [RF Patent №2019521 C1, CL 02 F 1/58, 1/62]. The cleaning process consists of adding in weakly acidic or neutral solution suspensions of magnetite, stirring, adjusting the pH of the solution to 7.7-9.5 and the sludge separation.

The disadvantage of this method is its limited applicability. The method is applicable only for solutions in to the activities of the radionuclides are bound colloid-dispersed state. Also featured in the way that the pH range is not optimal for cleaning solutions from radionuclides. The resulting EDM method, particles of magnetite have micron and submicron size, which can lead to leakage of magnetite particles with sorbed on them radionuclides or in purified water during the decanting stage precipitate, or additional stages of treatment. The result is a reduction in the efficiency of the cleaning process waste.

An object of the invention is to provide a method of processing low-level LRW, allowing to increase the efficiency of cleaning solution from radionuclides at the stage of water treatment magnetite, to increase the efficiency of the separation of the precipitate of magnetite and purified solution to prevent precipitation of magnetite in the purified solution or additional treatment.

The problem is solved in a way that is that the treatment of LRW from radionuclides spend suspension of magnetite obtained EDM dispersion of iron-containing raw materials, at pH=11-12. As the iron-containing raw materials can be used scrap iron or iron ore pellets. To prevent leakage of magnetite particles in purified water or optional cleaning solution on the Le decanting undergoes magnetic separation.

The described method for processing liquid radioactive waste low level of activity is implemented as follows. In the processed solution is payable suspension of magnetite and alkali is added to adjust the pH of the solution to pH=11-12. Nuclides in the colloid-dispersed state, are sorbed on the particles of magnetite. After settling, the solution is decanted and sent for further purification from the soluble forms of radionuclides by known methods, such as adsorption or membrane, and the residue is directed to curing. To prevent leakage in the purified solution and a guaranteed allocation of particles of magnetite at the stage of additional purification using a magnetic separation.

The magnetite obtained by electroerosion, its sorption properties are not inferior to traditional collectors on the basis of hydroxides. For cleaning solutions from radionuclides optimal for use magnetite is the range of pH=11-12.

The results of purification of liquid radioactive solutions of low activity with magnetite at different values of pH are given in the table.

Results purification of liquid radioactive waste magnetite obtained EDM method

pH plants the ora The degree of sorption of radionuclides %
90Sr137Cs60Co241Am
The proposed method is adsorption on magnetite at T:W=200 mg/l
4,80,00,00,091,2
6,40,00,05,096,4
7,62,08,315,098,0
8,824,69,030,296,1
10,072,625,055,099,0
11,093,934,077,099,0
1296,036,3to 85.299,4
Note: T:W is the ratio of solid phase to liquid, mg/l

Example. The original solution volume of 20 l, volumetric α-activity 2,0*103Bq/l, volumetric β-activity of 5.1*104Bq/l after addition of 200 mg/l (dry matter) suspension of magnetite obtained electric is versionnum the dispersion of iron-containing materials, and adjusting the pH goes into the sump. As a result, after deposition for 1 hour and decanting the resulting solution with a density of αactivity 12 Bq/l, volumetric β-activity 2,5*103Bq/l, which served to further purification by ion exchange, and precipitated suspension (pulp) with a volume of 0.1 l, humidity is around 90% and a density of 1.1 g/cm3surround α-activity 4*105Bq/l, volumetric β-activity of 9.2*106Bq/l, which is supplied to the curing of known methods (cementing).

Thus, the proposed method allows to process LRW low level of activity, to increase the efficiency of cleaning solution from radionuclides to carry out the separation of the precipitate of magnetite from a purified solution and is guaranteed to prevent particles of magnetite in the purified solution or additional treatment.

1. Method for processing liquid radioactive waste low level of activity, including the introduction of feed solution suspensions of magnetite obtained EDM dispersion of iron-containing raw material in distilled water, adjusting the pH of the alkali solution, the release of sludge that is sent to the curing and cleaning of decantate, characterized in that the pH of the solution adjusted with alkali to 11-12, before additional clean is such decanted clear magnetic separation.

2. The method according to claim 1, characterized in that the raw material to obtain magnetite used iron ore pellets or scrap iron.

3. The method according to claim 1, characterized in that additional cleaning is performed by using ion-exchange.



 

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