Method for decontaminating solutions from natural radionuclides

FIELD: chemical technology; recovery of deactivated and decontaminated radioactive industrial wastes.

SUBSTANCE: proposed method that can be used for deactivating and decontaminating industrial radioactive wastes incorporating Tb-232 and their daughter decay products (Ra-228, Ra-224), as well as rare-earth elements, Fe, Cr, Mn, Sl, Ti, Zr, Nb, Ta, Ca, Mg, Na, K, and the like includes dissolution of wastes, treatment of solutions or pulps with barium chloride, sulfuric acid, and lime milk, and separation of sediment from solution. Lime milk treatment is conducted to pH = 9 - 10 in the amount of 120-150% of total content of metal oxyhydrates stoichiometrically required for precipitation, pulp is filtered, and barium chloride in the amount of 0.4 - 1.8 kg of BaCl2 per 1 kg of CaCl2 contained in source solution or in pulp, as well as pre-diluted sulfuric acid spent 5 - 20 times in chlorine compressors in the amount of 0.5 - 2.5 kg of H2SO4 per 1 kg of BaCl2 are introduced in filtrate. Alternately introduced in sulfate pulp formed in the process are lime milk to pH = 11 - 12, then acid chloride wash effluents from equipment and industrial flats at pulp-to-effluents ratio of 1 : (2 - 3) to pH = 6.5 - 8.5, and pulp obtained is filtered. Decontaminated solution is discharged to sewerage system and sediment of barium and calcium sulfates and iron oxysulfate are mixed up with oxyhydrate sediment formed in source pulp neutralization process; then 35 - 45 mass percent of inert filler, 10 - 20 mass percent of magnesium oxide, and 15 -m 25 mass percent of magnesium chloride are introduced in pasty mixture formed in the process while continuously stirring ingredients. Compound obtained is subjected to heat treatment at temperature of 80 - 120 oC and compressed by applying pressure of 60 to 80 at.

EFFECT: reduced radioactivity of filtrates upon separation of radioactive cakes due to enhanced coprecipitation of natural radionuclides.

7 c, 1 ex

 

The present invention relates to chemical technology, particularly to a technology of inorganic substances and can be used for processing neutralization and decontamination of radioactive waste containing Th-232 and child products of disintegration (Ra-228, Ra-224), and REE, Fe, Cr, Mn, Al, Ti, Zr, Nb, TA, CA, Mg, Na, K, etc. of the Invention can be used for processing multicomponent complex intermediates containing natural radionuclides, industrial products and/or waste generated at different stages of technological processes of complex processing of loparite, zircon, ilmenite concentrates, sludge dump ferrocolumbium production, tailings wet magnetic separation of titanomagnetites, red slime aluminum production waste from the processing of columbite, ferroniobium and other

There is a method of recycling (Recycling process of chlorination of loparite // non-ferrous metallurgy, 1987, No.1, p.32-33) radioactive waste - waste molten salt irrigation filter chlorination process loparite concentrates, which consists in leaching of the melt through the drain into the water, stirring chloride slurry with a solution of barium chloride, sulfuric acid, heating the pulp and supply of steel scrap with the order in which Stanovlenie trivalent iron to divalent and raising the pH to 2.5 to 3.5; the treatment of the pulp with the milk of lime to a pH of 4.5 to 5.0, and then with 0.5%solution of polyacrylamide, filtering and washing the precipitate, drying the precipitate and subsequent removal and burial in store special waste (HSO).

There is a method allows to increase the degree of concentration of thorium and its contents in the “cake”that is sent to landfill; however, the degree of extraction of thorium from the solution in the sediment - radioactive cake - over 99.9%.

For reasons that impede the achievement of specified following technical result when using the known method is unsatisfactory degree of decontamination solutions due to the high radioactivity of the effluent after separation of thorium sludge.

Known analogues of the closest to the technical essence and the achieved result for the proposed method is a known method of disposal of radioactive waste (Concentration of chloride waste processing of loparite concentrates of // non-ferrous metals, 1985, No. 2, p.53-56), which is selected as a prototype.

According to the prototype of the original radioactive waste is dissolved, the resulting solution (slurry) is treated with a solution l2, sulfuric acid and lime milk, followed by filtration of the slurry, separating the mother liquor from oxyhydrate su is hatago sludge and its disposal in store special waste. There is a method allows to localize the thorium and place it in a convenient location to store the form in store special waste.

The disadvantage of the prototype method is unsatisfactory degree cleaning - decontamination solutions from daughter nuclides number of thorium-232, in particular from Ra-224 and Ra-228, which is connected with incomplete coprecipitation of radium with precipitation of barium sulphate, calcium and metal oxyhydrates. Another disadvantage of the prototype method is associated with the need of transporting radioactive fallout (Chekov) in store special waste (HSO), the construction and operation of which requires large capital expenditures.

The claimed technical solution aimed at addressing the challenge in improving the environmental and radiation safety.

The technical result that can be obtained by carrying out the claimed invention is to reduce the radioactivity of the effluent after separation of the radioactive Chekov by increasing the extent of coprecipitation of natural radionuclides of the number of Th-232, in particular Ra-224 and Ra-228 with the fallout - cakes, as well as in the localization of radioactive elements (thorium and the products of its decay) and transfer them in a radiation-safe form - non-dusting water-insoluble utverjdenie state, resistant to atmospheric precipitation, Grun the new and groundwater, not having a harmful effect on the health of the public and workers, and is suitable for further storage without causing ecological damage to the environment.

This technical result in the implementation of the inventive method is achieved in that in the method of decontamination solutions from natural radionuclides, including the production of chloride solutions or slurries by dissolving the radioactive waste processing their barium chloride, sulfuric acid and lime milk, separating the precipitate from the solution, the peculiarity lies in the fact that the original solution or slurry is neutralized with lime milk to pH 9-10 in the number of 120-150% of the stoichiometrically required for the deposition amount of the metal oxyhydrates received oxyhydrate the slurry is filtered, the filtrate is injected barium chloride in an amount of 0.4-1.8 kg BaCl21 kg CaCl2, present in the original solution or pulp, and pre-diluted in 5-20 times waste sulfuric acid chlorine compressors in the amount of 0.5-2.5 kg N2SO41 kg l2in the resulting sulphate pulp consistently give the milk of lime to a pH of 11-12, and then the acid chloride wastewater from washing of equipment and production areas with a ratio of pulp: runoff = 1:(2-3) to a pH of 6.5 to 8.5, the resulting slurry is filtered, desactive the integration of the solution discharged into the sewer, and sulfate precipitate containing sulfates of barium, calcium and oxysulfate iron mixed with oxyhydrate sludge from neutralization of the initial solution or slurry, the resulting pasty mixture is injected under continuous stirring 35-45% (wt.) inert filler, 10-20% (wt.) magnesium oxide and 15-25% (wt.) of magnesium chloride, the resulting composition is subjected to heat treatment at a temperature of 80-120°and pressing under a pressure of 60-80 ATM.

The peculiarity lies in the fact that the mixture of oxyhydrate and sulphate precipitation is carried out directly on the filter press by filtration oxyhydrate pulp through a layer of sulphate precipitate, obtained from processing the previous batch of radioactive waste.

The peculiarity lies in the fact that as the inert filler is used precipitation and sludge treatment facilities of the companies.

The peculiarity lies in the fact that as the inert filler using wood sawdust.

The peculiarity lies in the fact that as the magnesium oxide used crushed and heat treated magnesium-containing mineral oxide materials selected from the series, serpentine, and/or brucite, and/or magnesite.

The peculiarity lies in the fact that as the magnesium oxide used asbestos waste production.

The peculiarity lies in t is m, as the magnesium chloride used solution and/or slurry of magnesium chloride, for example condensed magnesia slurry formed during the purification of exhaust gases from CL2and/or Hcl magnesia suspension.

Under other equal conditions, the proposed method is characterized by new techniques of performing actions and the new order of execution of actions, the use of certain substances, without which it is impossible the implementation of the method, the new modes and parameters of the process, ensures the achievement of the technical result in the implementation of the claimed invention.

Check the patentability of the claimed invention shows that it corresponds to inventive step, as it is not necessary for professionals explicitly.

The analysis of the prior art indicates that in book, journal and patent literature contains no data on decontamination solutions from natural radionuclides by sequential processing of initial solution (slurry) first lime milk, then after separation of the oxyhydrate precipitate with chloride of barium, spent sulphuric acid, chlorine compressors in the amount of 0.5-2.5 kg N2SO41 kg BaCl2then the introduction of the milk of lime slurry, acid chloride wastewater from equipment washing the production sites at a ratio of pulp:runoff = 1:(2-3), filtration of the pulp, mix radioactive sludge with an inert filler, magnesium oxide, magnesium chloride and receiving units.

Analysis of the totality of the features of the claimed invention and achieved technical result shows that between them there is a causal relationship, which is expressed in the fact that the process of decontamination solutions from natural radionuclides in strictly defined above conditions, modes, and parameters of the process: the sequence of operations, the availability of new activities, the introduction of certain substances, defined by the ratio of the reagents, and a well-defined procedure for the introduction of reagents provide an improved decontamination and reduction of radioactivity of the effluent after separation of the radioactive fallout at the expense of increasing the degree of co-precipitation of natural radionuclides of the number of Th-232, in particular Ra-228 and Ra-224 hydrated, sulfate and oxysulfate precipitation - cakes, the localization of radioactive metals and their conversion into an environmentally safe form of non-dusting water-insoluble utverjdenie state, resistant to atmospheric precipitation, ground and underground waters, not having a harmful effect on the health of the public and workers, and is suitable for further skladi the Finance without causing environmental and radiation damage to the environment.

For violations of the above ratios of the reagents, a well-defined procedure for the introduction of reagents, mixing, process conditions, sequence, etc. of the above technical result is not achieved.

It should be noted that established a causal relationship is not obvious for specialists and not derived from literature data on the chemistry and technology of rare metals.

Information supporting the implementation of the present invention to provide the above technical result, and comparing the effectiveness of known (the prototype) and the proposed technical solutions described in the example.

Example

As solutions containing natural radionuclides for conducting experiments, were used: waste molten salt irrigation filter chlorination process loparite concentrates.

Solutions containing, wt.%: 2,5 ThCl4, 20 ll3, 7 LnCl3and impurities TiCl4Nbl3, TaCl5, NaCl, KCl, MgCl2, l2, water-insoluble residue (5%), was dissolved in water at W:T=4:1. With the obtained chloride pulp comparative trials on the effectiveness of decontamination and to determine the effectiveness of known (prototype) and predlagaemoj the methods.

According to the method the slurry was heated to 75±5°and treated With 200 l of 10%solution of barium chloride and 50 l of 78%sulfuric acid solution, and then neutralized with calcium hydroxide to pH 8.0±0.5, it was filtered on a plate and frame filter press. In the filtrate measured αradioactivity, and then again sent for decontamination according to the described scheme. The process of decontamination were thus 6 times before reaching the radioactivity of the filtrate 1 EQ-mg thorium/DM3.

In the proposed method the pulp was treated with lime milk to a pH of 9.0±0.5 in the amount of 130% of the stoichiometric required for the deposition amount of the metal oxyhydrates and filtered to frame filter press. The mother solution-the filtrate was treated with 50 DM310%-aqueous solution of barium chloride and 10 DM310%-aqueous solution of spent sulphuric acid chlorine compressors, after which the pulp was treated with lime milk to a pH of 11.5±0,5 introduced 2 m3acid chloride wastewater from washing of equipment and production areas to pH 7.0±0.5 in. Thus obtained slurry was filtered, the filtrate measured αradioactivity and dumped into the sewer. Fallout - oxyhydrate and oxysulfate - mixed, the resulting pasty mixture was injected under continuous stirring to 42.5% (wt.) inert filler, 15,5% (wt.) OK the IDA magnesium and 20% (wt.) of magnesium chloride, then the obtained composition was subjected to heat treatment at a temperature of 100°and pressing under a pressure of 75 ATM.

Research and testing has shown that the process of decontamination solutions from natural radionuclides in the proposed method gives the possibility to deactivate RAO to established standards, and transfer of radioactive Chekov in utverjdenie the state provides them with environmentally - safe storage without causing damage to the environment, public health and staff: obtained in accordance with the proposed method "blocks", as shown by tests that are resistant to fluctuations in ambient temperature (-50 to +50° (C), no dust, vodorastvorimyi and resistant to atmospheric precipitation, groundwater and subsurface waters.

1. The method of decontamination solutions from natural radionuclides, including the production of chloride solutions or slurries by dissolving the radioactive waste processing their barium chloride, sulfuric acid and lime milk, separating the precipitate from the solution, wherein the source solution or slurry is neutralized with lime milk to a pH of 9÷10 120-150% of the stoichiometrically required for the deposition amount of the metal oxyhydrates received oxyhydrate the slurry is filtered, fil the rat injected barium chloride in an amount of 0.4÷ 1.8 kg BaCl21 kg CaCl2, present in the original solution or pulp, and pre-diluted in 5-20 times waste sulfuric acid chlorine compressors in the amount of 0.5÷2.5 kg N2SO41 kg BaCl2in the resulting sulphate pulp consistently give the milk of lime to a pH of 11÷12, then the acid chloride wastewater from washing of equipment and production areas with a ratio of pulp : runoff = 1: (2÷3) to pH 6.5÷8,5, the resulting slurry was filtered and decontaminated solution discharged into the sewer, and sulfate precipitate containing sulfates of barium, calcium and oxysulfate iron, mixed with oxyhydrate sludge from neutralization of the initial solution or slurry, the resulting pasty mixture is injected under continuous stirring 35-45 wt.% inert filler, 10÷20 wt.% magnesium oxide and 15÷25 wt.% of magnesium chloride, the resulting composition is subjected to heat treatment at a temperature of 80-120°and pressing under a pressure of 60-80 ATM.

2. The method according to claim 1, characterized in that the mixture of oxyhydrate and sulphate precipitation is carried out directly on the filter press by filtration oxyhydrate pulp through a layer of sulphate precipitate, obtained from processing the previous batch of radioactive waste.

3. The method according to claim 1, characterized in that the image quality is as inert filler used precipitation and sludge treatment facilities of the companies.

4. The method according to claim 1, characterized in that as the inert filler using wood sawdust.

5. The method according to claim 1, characterized in that the magnesium oxide used milled and heat treated magnesium-containing mineral oxide materials selected from a number of serpentinite and/or brucite, and/or magnesite.

6. The method according to claim 1, characterized in that the magnesium oxide used asbestos waste production.

7. The method according to claim 1, characterized in that the magnesium chloride used solution and/or slurry of magnesium chloride, for example condensed magnesia slurry formed during the purification of exhaust gases from CL2and/or Hcl magnesia suspension.



 

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