RU2035074C1 - Agent for removing impurities of radioactive and toxic metals - Google Patents

Abstract

FIELD: deactivation. SUBSTANCE: powder detergent is proposed, solution of said detergent is used for removing impurities by radioactive and toxic metals of various surfaces. Said solution contains polyamine carboxylic acids or their salts, surface active substances, inorganic polyphosphates and other components. Proposed agent contains 3-10 mass % of polyamino carboxylate or its alkali salts and 1-5 mass % of polyamino phosphonate per 96-85 % of its base. EFFECT: improves quality of agent. 3 dwg, 1 tbl

Description

 The invention relates to decontamination and directly relates to technical detergents (STM) for washing strongly fixed contaminants with radioactive and toxic metals.

 It is known to use aqueous solutions of carboxylic acids to remove radioactive contaminants from solid surfaces. For example, in the known method for the decontamination of metal surfaces, aqueous solutions of organic acids such as oxalic, citric, nitrilotriacetic, hydroxyethylene diaminotriacetic, were used, the first two acids being isolated as preferred for surface decontamination.

Their main disadvantage is the limited range of application because of low complexing ability of the neutral and alkaline media, the effective solutions of oxalic acid and citric acid at elevated temperatures (60-100 ° ^C) surface treatment of contaminated radioactive cobalt.

 The invention has been examined using only oxalate and citrate solutions and there is no way to evaluate the use of other complexing agents. It should be noted the high corrosive activity of oxalate and citrate solutions, which leads to the formation of secondary deposits of iron oxalate (citrate) and thus to a decrease in deactivating ability.

 It is also known to use mixtures of oxalic acid and alkali with ethylenediaminetetraacetic acid (EDTA) or hydroxyethylidene diphosphonic acid (OEDP) at a molar ratio of alkali and EDTA or OEDP equal to 7-15: 1 and pH 7-9 as deactivating agents.

The disadvantage of this composition is its unstable efficiency when washing various metal surfaces. It is quite effective when washing a surface of carbon steel, and when washing a surface of stainless steel, the efficiency drops by an order of magnitude. Moreover, the use of this agent is recommended to carry out at elevated temperatures (60-90 ° ^C), that in the real world is not always feasible.

 As deactivating agents, multicomponent compositions are used, which contain, along with complexones, other components of synthetic detergents (SMS), hereinafter referred to as the “base” of the agent.

 As a prototype of the proposed new tools selected well-known composition in the form of a solution containing 1 wt. Na-salts of ethylenediaminetetraacetic acid (Trilon B) and 1 wt. surface active substances (surfactants) (sulfonol). The data indicate a limited scope of application of this composition both in relation to radionuclides and in relation to various surfaces, i.e. Known formulations are not universal decontaminants. Their other disadvantage is the inconvenience of their application, it is necessary to weigh, dissolve various components before use. This composition has high foaming, because it does not contain SMS components that reduce foaming and foam removal requires a large amount of wash water, thus a large amount of radioactive waste is generated.

 Since the necessary information about the effectiveness of this composition is not given in the source, additional laboratory tests of the deactivating composition obtained on the basis of the standard decontaminating preparation SF-3 containing sulfonol and polyphosphates were carried out, to which Trilon B was added in various concentrations for the correctness of the experiment (see Fig. . 1).

 A means for removing contaminants from radioactive and toxic metals, including polyaminocarboxylic acids or their salts, surfactants, inorganic polyphosphates, contains 3-10 wt. polyaminocarboxylate or its alkaline salts and an additional 1-5 wt. organic polyaminophosphonate or its salts to 85-96 wt. SMS basics.

 The new composition differs from the known content of an additional component of the polyaminophosphonate or its salts at a certain weight ratio of carboxy- and aminophosphonate-containing reagents.

 The use of polyaminophosphonic acids and their salts as deactivating agents is not described in known publications.

 Polyaminocarboxylate (PAA) or its salts are included in the composition of the deactivating agent in an amount of at least 3 wt. of the total weight of the composition, since with smaller amounts of PAA there is a sharp decrease in the effectiveness of deactivation, an increase in concentration of more than 10% does not lead to a significant increase in deactivating ability (see Fig. 2).

 As the polyaminocarboxylate, nitrilotriacetic, ethylenediaminetetraacetic, diethylene triamine pentaacetic and their higher molecular weight analogues, as well as their mixtures, including the carboxyalkylation product of polyethylene polyamine, can be used.

 The following compounds may be included as organic polyaminophosphonates: nitrilotimethylphosphonic acid (NTP), ethylenediaminetetramethylphosphonic acid (EDTP), diethylenetriaminepentamethylenephosphonic acid (DTPP), other higher molecular weight analogues and their mixtures, including polyethylene phospholipids.

 The choice of the concentration range of the aminophosphonate-containing component from 1 to 10% is explained by the fact that at lower concentrations the deactivation efficiency decreases (see Fig. 3), and at concentrations of more than 10% precipitation of insoluble polynuclear complexes with metals is possible, which limits the possibility of their deposition using regular means of decontamination.

 The highest decontamination efficiency is achieved with compositions containing a composition of carboxy- and aminophosphonate-containing complexones (see Fig. 3), and their optimum content is the following: 1-5% polyaminophosphonic complexon, 3-10% polyaminocarboxyl-containing complexon.

 To compare the deactivating properties of the known and the new composition, laboratory tests of the deactivating ability of 1% SF-3 solutions with the addition of Trilon B, a composition with different concentrations of PAA and the proposed product with the simultaneous content of polyaminocarboxylate and aminophosphonate-containing reagent were carried out (see Fig. 1-3).

 To simulate the complex isotopic composition of contaminants under laboratory conditions, a mixture of the cesium-137 and cerium-144 + praseodymium-144 isotopes was selected. In this case, cesium is the most easily removed element, and the rest imitate elements of transition groups with variable valency. A 1% deactivating solution was prepared from powdered STM by dissolving in water.

 As can be seen from FIG. 1-3, these compositions are most effective for washing metal and fabric surfaces, i.e. where the processes of complex formation play the largest role, and in the case of plastic, the decontamination efficiency is lower, since mainly the dirt is fixed in microcracks, where the decontamination solution penetrates with difficulty and complexation processes do not play a big role.

 The ratio of the aminophosphonate and carboxyl-containing components in the composition can vary within these limits, depending on the radionuclide composition of the contaminants, in order to bind alkaline and alkaline-earth metals, it is necessary to increase the concentration of polyaminophosphonate, while heavy elements bind with polyaminocarboxylic acids with greater efficiency.

 Thus, the choice of the concentration range of the composition of carboxylic and aminophosphonate-containing acids (or their salts) is explained by the fact that it is within these limits that the greatest versatility and effectiveness of decontamination is ensured while maintaining the remaining consumer qualities of solubility, washing properties, predetermined composition, moisture content, bulk density and etc.

 In addition to the composition of carboxylic and phosphonate-containing acids and their salts, the composition of technical detergent includes known components of synthetic detergents, considered as the "basis" of the agent. Such well-known components include surfactants of various nature; polyphosphates, for example TPP tripolyphosphate; liquid glass; CMC carboxymethyl cellulose; electrolytes, etc., which can be included in various forms, for example, such as in the Lotus formulation.

 The invention is illustrated by the following example of the formulation of STM presented in the table.

The new composition of STM (code "Granula", commercial name "MAGNIT", example 1), containing a composition of polyaminocarboxylic and polyaminophosphonic acids or their salts, allows you to clean the surface (metal, plastic, fabric) in a wide temperature range (4-100 ^о С ) from radioactive contamination of a whole spectrum of radionuclides, has greater efficiency and versatility of decontamination compared with the well-known drug SF-3 (Fig. 1-3). In addition, it has improved detergent qualities due to an increase in complex-forming ability and stronger binding of hardness ions and heavy metals. STM "MAGNET" is effective for the removal of secondary radioactive contaminants in the form of corrosion products of metal surfaces.

 It should be noted that an important advantage of the new composition is its ease of use, since there is no need to mix the individual components before use, foaming is significantly reduced, this reduces the amount of radioactive and toxic waste and reduces the burden on the environment. The new composition is effective at low temperatures in the Far North.

Claims (1)

 MEANS FOR REMOVAL OF POLLUTIONS BY RADIOACTIVE AND TOXIC METALS, including a base from synthetic detergent and polyaminocarboxylic acids or their salts, characterized in that it additionally contains polyaminophosphonic acids or their salts in the following ratio of components of the mixture, wt. Polyaminocarboxylic acids or their salts 3 10
Polyaminophosphonic acids or their salts 1 5
Synthetic detergents

Images