RU2176829C1 - Method for sorption decontamination of low-activity liquid wastes from strontium - Google Patents

Abstract

FIELD: chemical technology for decontaminating solutions from radioactive elements. SUBSTANCE: liquid wastes are decontaminated from strontium-90 on sulfonated cationite KU-2 in Ni²⁺- form. Cationite in Ni²⁺- form is produced in the course of nickel extraction from rinsing water in electroplating process. Proposed method provides for increasing working cycle of column with sulfonated cationite KU-2 in Ni²⁺- form by 1.5 times. EFFECT: facilitated procedure due to use of nickel-containing sorbent. 2 cl, 1 tbl, 1 ex

Description

 The invention relates to the field of chemical technology, specifically to methods for sorption purification of solutions from radioactive strontium.

 Radioactive strontium-90 is the most dangerous of the fragmentation of radioactive elements, as it is firmly held in the body, concentrating in the bones, and has a long half-life of 29 years.

A known method of extracting radioactive strontium from contaminated water by sorption on cationite nalcite HCR in sodium form / Ion-exchange technology. Sat under the editorship of F. Nachod and J. Schubert. Metallurgizdat, 1959. - p. 480 /. The disadvantage of this method is the small dynamic capacity of strontium. After passing 534 ml / cm ^{3 of} nalcite (or 534 column volumes), the strontium-90 content exceeded the permissible level in water of 4.0 • 10 ^-10 Ku / l (radiation safety standards, NRB-76/87, M. - Energoatomizdat, 1988 .-- pp. 38-39). In the initial solution there were 8.0 • 10 ^-8 Ku / l strontium-90 and 85 mg / l hardness, calculated on calcium carbonate.

A known method of extraction of fission products on cation exchange resin nalcite HCR, when half of the cation exchange resin was in the Fe ³⁺ form, and the other half in the H ⁺ form. / Ion exchange technology. Sat under the editorship of F. Nachod and J. Schubert. Metallurgizdat, 1959. - p. 484 /. However, neither strontium-90 nor cesium-137 is adsorbed by the iron form of ion exchanger at pH 2.5; at pH 7.0, the results are unstable, since iron (III) is likely to form hydroxide upon ion exchange, which can adversely affect the ion exchange process.

The closest to the achieved effect is the method of purification of the solution from strontium-89 through cation exchange resin IR-120 in H ⁺ form / Ion-exchange technology. Sat under the editorship of F. Nachod and J. Schubert. Metallurgizdat, 1959. - c. 480. Prototype. Comparative experiments showed that cation exchanger in the H ⁺ form compares favorably with cation exchanger in the Na ⁺ and Ca ²⁺ forms: for the same volume of the passed solution equal to 82 column volumes, the purification coefficient for the H ⁺ form was approximately 30 times higher the content of strontium in the filtrates is 1.8 • 10 ^-9 Ku / l for H ⁺ cation exchanger and 5.5 • 10 ^-8 Ku / l for Na ⁺ and Ca ²⁺ cation exchanger. The disadvantage of this method is the low exchange capacity, which leads to an increase in the number of regeneration cycles and, consequently, the accumulation of liquid radioactive regenerates.

 Object of the invention: increasing the life of the ion exchanger and the degree of purification of the solution.

The solution of this problem is achieved by the fact that in the method of sorption purification of low-level liquid waste from strontium-90, including the exchange of ions on cation exchange resin, sorption is carried out on sulfocationite, for example, KU-2 in Ni ²⁺ form. Cation exchanger in Ni ²⁺ form is obtained in the process of sorption purification of nickel from washing water of galvanic production.

 Example.

Two glass columns are loaded with 10 ml of KU-2 cation exchanger in a swollen state in Ni ²⁺ and H ⁺ forms. A column volume at a temperature of 20-25 ^° C is passed through each column at a speed of 20-30 min. A solution of the following composition contaminated with radionuclides: content of radionuclides in Ci / L - Sr (89 + 90) - 1.6 • 10 ^-8 ; Y-90 - 1.7 • 10 ^-8 ; Cs-137 - 1.5 • 10 ^-9 ; Zr-95 + Nb-95 - 2.2 • 10 ^-10 ; Ru (103 + 106) - 6.8 • 10 ^-10 ; Ce - 144 - <2 • 10 ^-10 ; total β-activity - 2.4 • 10 ^-8 ; salinity of 0.2 g / l; hardness - 1.5 mEq / l, pH 8-9.

 The main share of the total β activity is Sr (89 + 90) or the practically long-lived isotope Sr-90.

 The degree of purification of the solution was determined by the content of Sr-90 in the filtrates. The solution was allowed to pass through strontium into the filtrate. The experimental results are shown in the table.

Technical appraisal and economic advantages of the proposed method are to increase, compared with the prototype, the working cycle of the column with sulfacationite KU-2 in Ni ²⁺ form approximately 1.5 times. The strontium content in the filtrates is less than the maximum permissible concentration _B.

 In the process of ion exchange, a gradual transition of nickel ions into the filtrate occurs; Nickel content in the filtrate depends on the chemical composition of the initial solution. Depending on the use of purified liquid low-level waste, the standards for nickel content in them can vary widely.

Claims (2)

1. The method of sorption purification of low-level liquid waste from radioactive strontium, including the exchange of ions on cation exchange resin, characterized in that the sorption is carried out on sulfocationite, for example, KU-2 in Ni ²⁺ form. 2. The method according to claim 1, characterized in that the cation exchanger in Ni ²⁺ form is obtained in the process of sorption purification from nickel of washing water from galvanic production.

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