Method for reprocessing of thorium-containing radwastes

FIELD: rare, dispersed and radioactive metal metallurgy, in particular hydrometallurgy.

SUBSTANCE: invention relates to method for reprocessing of polymetal, multicomponent, thorium-containing radwastes, formed when reprocessing of various mineral, containing rare-earth elements, Nb, Ta, To, V, Zr, Hf, W, U, etc. Method includes treatment of solution and/or slurry with alkaline agent; introducing of sulfate-containing inorganic compound solution and barium chloride; treatment of obtained hydrate-sulfate slurry with iron chloride-containing solution, and separation of radioactive precipitate from solution by filtration. As alkali agent magnesia milk containing 50-200 g/dm² of MgO is used; treatment is carried out up to pH 8-10; sodium sulfate in amount of 6-9 g Na₂SO₄/dm² is introduced as solution of sulfate-containing inorganic compound; barium chloride solution is introduced in slurry in amount of 1.5-3 g BaCl₂/dm². Hydrate-sulfate slurry is treated with solution and/or slurry containing 0.8-16 Fe³⁺/dm² (as referred to startingsolution) of iron chloride, followed by treatment with high molecular flocculating agent and holding without agitation for 0.5-2 h. Radioactive precipitate is separated from mother liquor, washed with water in volume ratio of 0.5-2:1; then washed with sodium chloride-containing solution and/or slurry in volume ratio of 0.5-2:1; radioactive precipitate is removed from filter and mixed with mineral oxides in amount of 0.5-0.8 kg MgO to 1 kg of precipitate. Formed pasty composition is fed in forms and/or lingots and presses with simultaneous heating up to 80-120⁰C.

EFFECT: filtrate with reduced radioactivity due to increased codeposition coefficient of natural Th-232-group radioactive nuclide, in particular Ra-224 and Ra-228, with radioactive precipitates.

10 cl, 1 ex

The present invention relates to the field of metallurgy of rare, scattered and radioactive metals, in particular hydrometallurgical methods of processing complex, multicomponent, thorium radioactive waste generated during the processing of various mineral raw materials containing REE, Nb, TA, Ti, V, Zr, Hf, W, U, etc. of the Invention can be used in the processing, neutralization and decontamination of salt waste processes chlorination loparite, and/or zirconium and/or titanium concentrates.

A method of refining of thorium radioactive waste - waste chlorination process loparite concentrates (non-ferrous metals, 1993, No. 12, p.30-31; Cm. also: Journal of applied chemistry, 1990, t, s. Dept. VINITI 10.10.1989, No. of 6,183 - 89). The known method consists in sorption extraction of thorium phosphate macroporous cationic type CFP followed by desorption of thorium from the cation carbonate-bearing solutions, the precipitation of thorium compounds from the eluate to obtain, after drying and calcining concentrates containing 90-98% h₂for decontamination solutions from daughter products - Ra-228 and Ra-224 - (Journal of applied chemistry, 1990, t, s), the operation processing of the initial pulp H₂SO₄(Na₂SO₄and BaCl₂. However, as shown by the results of the special the territorial research and testing, the introduction of this operation in the “head” of the process does not ensure the desired degree of decontamination solutions, and therefore requires additional operations decontamination solutions-filtrates after sorption columns. This ultimately leads to the formation of a large amount of secondary radioactive waste (RW)disposed in store special waste (HSO).

Known (“the Way of extraction of thorium from solutions” Application No. 9302707/26 with prior. dated 11.05.1993. MKI 01 F 15/00. Publ.: Bull. No. 18. 1995, p.27) the method of processing of thorium radioactive waste (See. also: radiochemistry, 1996, V. 38, N. 1, p.60-65; non-ferrous metallurgy, 1995, No. 7-8, p.30-33. Rimet. 1996, SG), lies in the selective extraction of thorium by coprecipitation with precipitation Ba(Ca)SO₄solutions containing REE, rare, scattered, non-ferrous metals. The method involves processing the original solution of chloride of an alkali metal and/or ammonium and/or hydrochloric acid to obtain saturated by the amount of metal chlorides solution, introducing the solution of a first soluble in water selfaddressed inorganic compounds, then a water-soluble salt of barium in quantities that establish a molar ratio of SO₄/VA≥1.1 and BaSO₄/Th≥30; Department of radioactive sludge from the solution.

There is a method allows high izbiratelni the capacity to extract thorium from solutions containing 0.01 to 0.1 g/DM³thorium and other metals. However, when the concentration of thorium more than 0.1 g/DM³requires a very high consumption of barium salts and solfataras inorganic compounds (Na₂SO₄), which leads to the formation of a large volume of precipitation - secondary radwaste disposed, with the required degree of decontamination fluids from Ra-228 and Ra-224 is not achieved due to adsorption and coprecipitation of thorium with sediment BaSO₄and the lock on the surface of barium sulfate ions Th⁴⁺.

Known analogues of the closest to the essential features is the method of processing of thorium radioactive waste, including treatment solutions and/or slurries alkaline reagent, the introduction of solutions selfaddressed inorganic compounds and barium chloride, processing hydrate sulphate pulp with a solution containing ferric chloride and separation of radioactive sludge from the solution by filtration (EN 2205461 C2, IPC G 21 F 9/30, publ. 27.05.2003, page 1, column 1, page 5 example 3, option 3, example 4, option 2).

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 Exige is the ATA metals. Another disadvantage of the prototype method is associated with the need of transporting radioactive fallout 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 fallout at the expense of increasing the degree of co-precipitation of natural radionuclides of the number of Th-232, in particular Ra-224 and Ra-228 with the fallout, and 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, ground and underground waters, not having a harmful effect on the health of the public and workers, and is suitable for further storage without the ecological damage caused to the environment.

This technical result in the implementation of the inventive method is achieved by the known method of processing of thorium radioactive waste, including treatment solutions and/or PU is IP alkaline reagent, introduction solutions selfaddressed inorganic compounds and barium chloride, processing hydrate sulphate pulp with a solution containing ferric chloride and separation of radioactive sludge from the solution by filtration, as the alkaline reagent used milk of magnesia with a MgO concentration of 50-200 g/DM³the treatment is carried out to a pH of 8-10, as a solution selfaddressed inorganic compounds enter solution of sodium sulfate in the amount of 6-9 g Na₂SO₄/DM³then the slurry is injected solution of barium chloride in the amount of 1.5-3 g l₂/DM³, hydrate sulphate pulp is treated with a solution containing ferric chloride in a quantity of 0.8-16 g Fe³⁺/DM³initial solution and/or slurry, treated with high-molecular flocculant and incubated without stirring for 0.5-2 hours, the radioactive precipitate was separated from the mother liquor, washed first with 0.5 to 2 volumes of water per 1 volume of sediment, then the solution and/or suspension containing magnesium chloride in the amount of 1-2 volume 1 volume of sludge, radioactive sludge from the filter is unloaded and mixed with magnesium-containing oxide mineral materials, taken in an amount of 0.5-0.8 kg MgO per 1 kg of sludge generated pasty composition mixture is placed in a mold and/or mold and pressed while heating up to 80-120° C.

The peculiarity lies in the fact that as milk of magnesia is used, the suspension is prepared on the basis of magnesium-containing oxide mineral materials, such as asbestos production waste.

The peculiarity lies in the fact that as a magnesium-containing oxide mineral materials use pre-heat treated natural mineral materials, industrial products and/or waste asbestos production with a particle size less than 100 microns.

The peculiarity lies in the fact that as selfaddressed inorganic compounds using a solution of Na₂SO₄with a concentration of 50-200 g/DM³.

The peculiarity lies in the fact that, as a solution of barium chloride is used a solution with a concentration of 50-200 g l₂/DM³.

The peculiarity lies in the fact that as a solution and/or suspension of magnesium chloride uses a suspension, obtained by the interaction of magnesium-containing oxide mineral materials, such as asbestos production waste with a solution of hydrochloric acid.

The peculiarity lies in the fact that as a solution and/or suspension of magnesium chloride is used, the suspension formed during the purification of exhaust gases from CL₂and/or Hcl milk of magnesia.

The peculiarity lies in the fact that RA is down use of ferric chloride solution with a concentration of 10-100 g Fl ₃/DM³.

The peculiarity lies in the fact that as of the ferric chloride solution used shop waste water generated during the washing of production sites and equipment, iron 5-2 g/DM³.

The peculiarity lies in the fact that the solution of high-molecular flocculant use a solution of polyacrylamide with a concentration of 0.01 to 0.2%.

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 information about the processing of thorium radioactive waste by sequential processing of initial solution (slurry) first alkaline reagent, then solutions of sodium sulfate, barium chloride, after which the introduction into the slurry solution containing chlorine is the ID of the iron, filtering the slurry, washing the precipitate first, 0.5 to 2 volumes of water per 1 volume of sediment, then the solution and/or suspension containing magnesium chloride in the amount of 1-2 volume 1 volume of sediment mixing radioactive precipitate with magnesium-containing oxide mineral materials, pressing, heating 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 implementation of the processing of thorium radioactive waste 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 with hydrate, sulfate and oxysulfate precipitation, the localization of radioactive metals and their conversion into an environmentally safe form of non-dusting water-insoluble utverjdenie condition resistant at overnigh precipitation, groundwater and subsurface waters, not having a harmful effect on the health of the public and workers, and is suitable for further storage 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 is shown 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, % mass: 2,5 ThCl₄, 20 ll₃, 7 LnCl₃and impurities TiCl₄, NbCl₃, l₅, NaCl, KCl, MgCl₂, CaCl₂, water-insoluble residue (5%), was dissolved in water at W:T=4:1. 1 DM³the pulp was treated with m gnatelim milk to a pH of 9.0±0.5, and then was treated with 40 DM³solution containing 100 g/DM³sodium sulfate, 25 DM³solution containing 100 g/DM³barium chloride, after which the slurry was injected 0,8 DM³solution containing 5 g/DM³Fe³⁺. Then the pulp was treated with a 0.1%solution of polyacrylamide, the slurry was kept without stirring for 1 hour and filtered, radioactive precipitate was separated from the mother liquor, washed first with 1.5 volumes of water per 1 volume of the precipitate, then a solution containing magnesium chloride in the amount of 1.5 volume 1 volume of sediment, the sediment was mixed with magnesium-containing oxide mineral materials, taken in an amount of 600 g MgO per 1 kg of sludge generated pasty composition, and the mixture was placed in a mold and was pressed while heated to 100°C.

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 norms, and transfer of radioactive fallout 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 the temperature of the environment (from -50 to +50° C)no dust, vodorastvorimyi and resistant to atmospheric precipitation, groundwater and subsurface waters.

1. The method of processing of thorium radioactive waste, including treatment solutions and/or slurries alkaline reagent, the introduction of solutions selfaddressed inorganic compounds and barium chloride, processing hydrate sulphate pulp with a solution containing ferric chloride and separation of radioactive sludge from the solution by filtration, characterized in that as the alkaline reagent used milk of magnesia with a MgO concentration of 50-200 g/DM³the treatment is carried out to a pH of 8-10, as a solution selfaddressed inorganic compounds enter solution of sodium sulfate in the amount of 6-9 g PA₂SO₄/DM³then the slurry is injected solution of barium chloride in the amount of 1.5-3 g l₂/DM³, hydrate sulphate pulp is treated with a solution containing ferric chloride in a quantity of 0.8-16 g Fe³⁺/DM source solution and/or slurry, treated with high-molecular flocculant and incubated without stirring for 0.5-2 h, the radioactive precipitate was separated from the mother liquor, washed first with 0.5 to 2 volumes of water per 1 volume of sediment, then the solution and/or suspension containing magnesium chloride in the amount of 1-2 volume 1 volume of sludge, radioactive sludge from the filter vigra is up and mixed with magnesium-containing oxide mineral materials, taken in an amount of 0.5-0.8 kg MgO per 1 kg of sludge generated pasty composition mixture is placed in a mold and/or mold and pressed while heated to 80-120°C.

2. The method according to claim 1, characterized in that as milk of magnesia is used, the suspension is prepared on the basis of magnesium-containing oxide mineral materials, such as asbestos production waste.

3. The method according to claim 1, characterized in that as the magnesium-containing oxide mineral materials use pre-heat treated natural mineral materials, industrial products and/or waste asbestos production with a particle size less than 100 microns.

4. The method according to claim 1, characterized in that as selfaddressed inorganic compounds using a solution of Na₂SO₄with a concentration of 50-200 g/DM³.

5. The method according to claim 1, characterized in that as a solution of barium chloride is used a solution with a concentration of 50-200 g l₂/DM³.

6. The method according to claim 1, characterized in that as a solution and/or suspension of magnesium chloride uses a suspension, obtained by the interaction of magnesium-containing oxide mineral materials, such as asbestos production waste with a solution of hydrochloric acid.

7. The method according to claim 1, characterized in that as a solution and/and and suspension of magnesium chloride is used, the suspension, formed during the purification of exhaust gases from Cl₂and/or Hcl milk of magnesia.

8. The method according to claim 1, characterized in that the quality of the ferric chloride solution used solution with a concentration of 10-100 g Fl₃/DM³.

9. The method according to claim 1, characterized in that as a solution of ferric chloride used shop waste water generated during the washing of production sites and equipment with an iron content of 5-2 g/DM³.

10. The method according to claim 1, characterized in that the solution of high-molecular flocculant use a solution of polyacrylamide with a concentration of 0.01 to 0.2%.