HU183570B - Process for the separation of isotopes with the method of directed distribution by means of the utilization of the isotopic concentration effect - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention relates to a process for separating isotopes in two-phase systems by directional distribution using the isotope concentration effect, such that a two-phase system comprising a solution or mixture of isotopic components or ligands at a concentration of KP6 M to saturation in which each isotopic component is present. its molar ratio is 1: 105 to 1: KP5 and optionally contains complex or chelating additives, and the other phase is a solid sorbent with a preferred particle diameter of KP6-10 "2m or an optional carrier applied in the dark or 2.5-102. -109 nm wavelength at 32 to 103 ° K for 1Q-2_1O * revolutions / sec for mixing speed or column arrangement l (p6—1 (at P 1 m / sec flow rate for KP2-106 sec, then desorption or reextraction, optionally excipients 238U, + J35U "= 23eU" + J35U, -1-

Description

The present invention relates to a process for separating isotopes from two-phase systems, such as solid phase-liquid phase, liquid phase-liquid phase, solid phase-gas phase systems. The method is based on the recognition that the distribution of isotopes can be controlled by the choice of phase composition, i.e., their structural and material composition, concentration of isotopes and ligands, and temperature, illumination, hydrodynamic parameters, and time of phase contact. The process of the present invention provides a highly efficient means of separating, for example, uranium, lithium, and sulfur isotopes from aqueous or non-aqueous solutions, or gaseous mixtures, when treated with solid sorbets or liquid extraction agents. ¹

The process is essentially a chemical separation method.

Chemical isotope separation techniques known and used hitherto (see, for example, N. Laskorin et al., Uspechi chimii, Vol. XLIV, 5, 761-780 (1975), J. de ² Carrnan et al., Report AAEC / LIB / BIB 273 (1970) are based on the isotope exchange reaction, which has equilibrium constants, i.e., usually elemental separation factors, ranging from 1.01 to 1.0001, depending on the mass of the corresponding isotope. 2 Isotopes of heavy metals, such as uranium, show lower values. In recent years, great attention has been paid to the separation of uranium isotopes on solid sorbents and liquid extraction agents (German Patent Nos. 2,335,603, 2,349,595 and 2,623,891, 3,663,437), and A. Ponta, A. Calusaru: Isotopenpraxis 13, 6, 214-216 (1977) and 77, 12, 422-426 (1975).

• A common feature of all known processes is the isotope exchange reaction according to Reaction Scheme A, Roman numerals denoting the individual phases to provide maximum conditions.

However, the first attempts to separate the U (VI) isotopes were unsuccessful because a separation factor of more than 1.00009 could not be reproducibly achieved using isotope-exchange and chromatography. Therefore, attention has been focused on systems with different valence uranium ions, namely the 4 U (VI-U (IV) and U (III) -U (IV) ions). In these systems, an electron exchange reaction occurs simultaneously, In addition, the use of a suitable sorbent or, optionally, a selective extraction agent for a particular valence ion of uranium in the context of the isotope effect of the complexing reactions can, in fact, result in a significant increase in separation efficiency. , Miyake, T., Inada, Nucl. Technology 50, 178-186 (1980), Report INFEC / DEP / WG 2/31, "On the Technical, Economical and Safequard Information of the Diffractive Enrichment Techniques, 15 March 1979". it can be seen that the elementary separation factor value has been raised above the 1.001 level, which is considered to be the lower limit of solubility (for example, the elemental partitioning factor of the gas diffusion process for large-scale uranium isotope separation is about 1.0027). We can say that the task to be solved is both economically and technologically significant. However, industrial use is ambiguous due to the limits of the elemental separation factor, which involves the construction of multi-stage equipment, the high retention of enriched uranium and the considerable time required to achieve the stationary state. Also, the uranium oxidation and reduction of multiple repetition of a significant weakening of the oxidizing and reducing agents used in the process and increases energy demand ^0.

These drawbacks are overcome by the novel process of the present invention, which is based on directed distribution while utilizing the isotope concentration effect in two-phase systems.

Which method according to ⁵ the invention is that one phase of a two phase system formed gas ⁰ sek inert gaseous mixtures and the separated isotopes in aqueous or non-aqueous solutions between izotópkomponensek and ligands 10 ^"6 M to saturation concentration, or a gaseous mixture or izotópkomponen the izotópkomponensek the starting mixture, optionally in the starting solution 1:10 ⁵ l: 10 ~ are in a molar ratio ^of between ⁵ and the second phase is a solid sorbent, such as styrene-divinylbenzene mycelium or cellulose-based sorbent or an extractant by ion exchange or bio ⁵ sorbent lower fungi such as tributyl phosphate or trioctylamine, optionally bonded to carriers such as teflonone, silica or cellulose.

θ The outlined biphasic system exhibits a non-linear equilibrium isotherm during sorption and / or desorption, optionally extraction and / or reextraction, and the migration of isotopes from one phase to another at the contact of the two phases. Isotopic exchange can be inhibited if the isotopes are exchanged with different ligands such as carbonate, sulfate. with citrate, chloride or ethylenediaminetetraacetic acid ions in complex form or with chelating functional groups such as carboxyl or hydroxyl, or with phosphorus, sulfur or nitrogen, and / or when in the dark or 2.5-1 (^ - 10 ⁹ working in a wavelength of light.

In carrying out the process, the following parameters are adhered to: phase contact time 10 ² - 10 ⁶ sec, temperature 10 ² - 10 ³ ° K, agitator speed lo ^{-2 -} lOVsec, column flow rate at column ΙΟ * ⁶ —10 ′ m / sec and sorbent particle diameter ΙΟ ⁶ —KT ² m.

Inorganic ⁰ Isotopes desorb or reextrakciójához salt or acid solution, such as sodium carbonate, ammonium nitrate, sodium chloride, sodium sulfate, sulfuric, nitric or hydrochloric acid solution, and complexing ligands such as citrate pelB Daul, ethylenediaminetetraacetic acid - or a solution of compounds containing isobutyric acid ions, alone or in a mixture, at a concentration of 10 ³ M to saturation.

¹⁰ may be used in the method of the invention include izotópkomponensek so ^21S U (VI) and ²³⁸ U (VI) and ligands, such as nitrate, sulfate and carbonate ions 1CT ² -1CT összkoncentrációjú ^1M aqueous solution, which solution has a ^U-235 and ^The molar ratio of the starting mixture of ²³⁸ U-ions is from 1: 500 to 1: 100. Ion-21 based on a styrene-divinylbenzene copolymer solid> 5 times

183,570 exchangers or sorbents of inferior fungi such as Penicillium chrysogenum mycelium are used. The phases of the contact time selected from a range of 10 ² -10 ⁴ sec; working in the dark or in the wavelength range of 250-650 and adjusting the agitator speed from 0.800 to 12.0 rpm or at column flow ΙΟ * ⁴ -IO * ¹ m / sec, ΙΟ ^-4 -IO ^-3 m a solid sorbent having a particle diameter and a temperature of 273-373 ° K. For desorption

Using 10 ^-1 -1.5 M solution of sodium carbonate and sodium chloride or sodium carbonate and a hydrochloric acid solution.

The process of the present invention is characterized by a much higher separation factor than has been achieved so far with isotope exchange reactions. During sorption and sorption of uranium isotopes, the maximum elemental partition coefficient ranges from 1.02 to 1.10. Particularly advantageous is the use of a solution of hexavalent uranium and a high selectivity but not too high capacity for the uranium, as well as the kinetics of the sorption and, if desired, desorption process. The process of the present invention for separation of isotopes is of great economic and technological importance. The increase in elemental separation factor, particularly when separating uranium isotopes, results in a 1.0 to 1.5-fold reduction in separation steps, a reduction in the time needed to reach a stationary state and a one-fold reduction in the number of uranium remaining in the plant. The process involves working with a solution of hexavalent uranium, without the need to change the valence of the uranium and to convert it to UF ₆ before enrichment, as was the case with the industrially used enrichment processes. A further significant advantage of the process is that it is possible to use enriched uranium as a starting material containing uranium, which is "produced" by its present process and at least halves the waste ²³⁵ U isotope.

The process of the present invention for separating isotopes is further illustrated by the following example in which a sorption agent is used:

(a) When contacting an aqueous solution of a solid sorbent or liquid extraction agent and isotopes such as ²³⁵ U (VI) and ²³⁸ U (VI), where the concentration of one isotope is at least 0.5 to 1 times higher than the other, simultaneous sorption, except that the sorption rate of the process is relative to the equilibrium state and the mass transfer coefficient. This generally different sorption rate for each isotope component, which is related to the inhibition of isotope exchange (see (g)), is the essence of an effect called the "isotope concentration effect". The sorption rate can be described, for example, by the following equation:

R - K, · q - K · c

In the equation:

R is the sorption rate, the desorption rate, if any, and the isotope transport rate from one phase to another, k _q , k _{c is} the mass transfer coefficient, q, c, the process force and the concentration gradient between the "q" and "c" phases,

(b) the driving force for isotope transport from one phase (here from one to the other) to another is the concentration of isotopes within one phase and the equilibrium isotherm in the range and time of change of isotope concentration;

c) in view of the concentration of isotope in the solution and the type of control of the sorption process, a sorbent is selected which has, as far as possible, different directions of opening at the equilibrium isotherms corresponding to each isotope. Preferably, the sorption equilibrium isotherm for lower isotope concentrations has a control coefficient of 10 ^{2 to} 10 ³ and a higher concentration for the isomer of about 10;

d) since sorbent selection is limited by its properties, the composition of the solution may also be adapted to the sorbent properties. In this sense, it is possible to change the absolute isotope concentration, for example by dilution while maintaining the original isotope ratio, and the composition of the solution by adding additional components, such as complexing agents;

(e) the mass transfer coefficient depends on the composition of the solution (isotope concentration) and the sorbent, if appropriate, the type of extraction agent, and on the system temperature and hydrodynamic parameters (mixing and flow rate, sorbent particle size, etc.). As one of the most important concentration dependencies, these coefficients usually give different values for each isotope, but their absolute value depends primarily on the sorbent species. It has been found to be advantageous to work with a sorbent having a mass transfer coefficient within the range 10 * ^{5 to} 10 * ³ sec * ¹ ;

(f) as a sorbent having the above equilibrium and kinetic properties, generally referred to as "biosorbents" (see 155 833, 184 471 and

190,692 (Czechoslovakian Authentication Certificates), and ion exchangers based on styrene-divinylbenzene copolymer, alone or in extraction with a support such as Teflon, cellulose, silica;

(g) at the same time as sorption, optionally at the same time as extraction, ion exchange is initiated which reduces the adsorbed amount of each isotope due to differences in sorption rates. The negative effect of the isotope exchange process, which has a rate close to the sorption rate of the higher concentrations of isotopes, can be compensated for, if not eliminated, by appropriate choice of sorption agent and solution composition, and lower temperature and low illumination work. Isotope exchange can also be inhibited by binding the isotope components with complexing agents in one of the phases, for example, by adding appropriate ligands to the solution or by using a sorbent, optionally an extraction agent.

183 57C having complexing functional groups;

h) The kinetics of isotopic sorption described above are essentially valid for the kinetics of desorption and reextraction and the accompanying isotopic exchange.

Use examples

Example 1 A sorbet based on fungi of the Penicillium chrysogenum strain (Ostsorb MV 6/5) activated with hydrated titanium dioxide and Na-formulated (swollen and centrifuged) at 5 rpm with 293 ° K and exclusion of light. 60 ml of 0.01 M uranyl nitrate solution adjusted to pH 3.5. The ratio of ¹³⁵ U to ²³⁸ U isotopes in the stock solution is 0.725 1CT ² (a compound made of uranium, of course). During the sorption reaction, samples were taken from the liquid phase 10 and assayed for total uranium concentration (spectroscopically using Arsenazo I reagent) and the ratio of ²³⁵ U to ²³⁸ U isotopes determined using a mass spectrometer (AldermastonMicromass 30). From the result, 15 needles calculate the value of the separation factor over time:

time (sec) 0 0.6-10 ³ 1,2-10 ³ 2.4-10 ³ 3.6-10 ³ 7.2-10 ³ 14.4-10 ³ total uranium concentration 0.1 0,006 0.0053 0.0046 .0042 0.0037 0.0035 separation factor 1,000 0.997 0,976 .993 1,024 1,030 1,005

The separation factor is the ratio of ²³³ U to ²³⁸ U isotopic ratios in the sorbent phase and in the liquid phase.

Example 2

The time course of the change in total uranium concentration and isotope ratio of the liquid phase was determined as described in Example 1, except that it was performed under daylight. From the results obtained, we calculate the time dependence of the separation factor:

time (sec) 0 0.6-10 ³ 1.2-10 ² 2.4-10 ³ 3.6-10 ³ 7.2-10 ³ 14.4-10 ³ total uranium concentration 0.01 0.0058 0.0052 0.0044 .0042 0.0039 0.0037 separation factor 1,000 0,980 0,980 0.997 1.016. 1,020 1,025

Example 3

The total uranium concentration and the change in isotope ratio of the liquid phase were determined as described in Example 1, except that the highly acidic Katex (Amberlite

IH-120) ion exchanger was used. From these results, we calculate the time dependence of the separation factor:

time (sec) 0 0.3-10 ³ 0.6-10 ³ 1.8-10 ³ 3.6-10 ³ 10.8-10 ³ total uranium concentration 0.01 0.0031 0.0013 0.0003 0.0002 0.0002 separation factor 1,000 0.997 1,025 1,007 1,000 1,001

Example 4 g of swollen and centrifuged Ostsorb MV 6/5 sorbent was saturated with uranium up to 4-10 ^-3 M uranium / g, followed by stirring at 5 rpm,

At 293 K and daylight, add 20 ml of 1 M sodium chloride + 0.1 M sodium carbonate. The ratio of uranium isotopes in the sorbent at the beginning of 65 experiments was 0.725 · 10 ^-2 . During the desorption process, samples were taken from the liquid phase where total uranium concentration and ^23? U: ratio of ²³⁸ U isotopes. From the results the time dependence of the separation factor was calculated:

183,570

time (sec) 0 0.3-10 ³ 0.9-10 ³ 1.8-10 ³ 3.6-10 ³ 10.8-10 ³ total uranium concentration . 0 ³ 3,5-10- 3,7-10- ³ 4,3-10 ^-3 4,5-10- ^{3 3} 5,2-10- separation factor 1,000 0.984 1,033 1,045 1,050 1,032 Example 5 The total uranium concentration and liquid phase isotope ratio were determined as in Example 4. with the exception that the experiment is conducted in the dark. 1 ρ From the results we calculated the time dependence of the separation factor: time (sec) 0 0.3-10 ³ 0.9-10 ³ 3.6-10 ³ 10.8-10 ³ total uranium concentration 0 ³ 2,7-10- 3,5-10- ³ 4,4-10- ³ 4.9 ΙΟ- ' separation factor 1,000 1,059 1,038 1,071 1,066

Example 6 Hydrogen-form swollen and centrifuged sorbent (Ostsorb MV 6/5) based on fungi of the strain Penicilium chrysogenum (Ostsorb MV 6/5) was mixed with 50 ml of 0.01 M uranyl nitrate solution at 293 K and daylight. The stock solution had a ²³⁵ U-1: ²³⁸ U isotope ratio of 0.725 · 10 ~ ² . After three hours, the two phases were separated and the solution was stirred in a second step with 2 g of the same fresh sorbent for an additional three hours. a total of four sorption steps. After each step, the ratio of ²³⁵ U to ²³⁸ U is determined in the liquid phase (spectrophotometrically with Arsenazo I reagent) and after the final step in the sorbent phase (Aldermaston-Micromass, Model 30 mass spectrometer).

From the results, the elemental separation factor of a stair is calculated to be 1.020.

The separation factor in this case is the ratio of ²³⁵ U to ²³⁸ U isotopic ratios of the sorbent phase and the liquid phase three hours after mixing.

Example 7

Four sorption steps were carried out as described in Example 6, except that Ostsorb MV 6/5 sorbent activated with titanium dioxide was used. From the results, the elemental separation factor of a stair is calculated to be 1.025.

Example 8 Ostsorb MV 6/5 sorbent g (hydrogenated and centrifuged) was saturated with uranium to a capacity of 4 · 10 ~ ^S M uranium / g, followed by stirring at 5 rpm, 293 ° K and daylight with 20 ml of 1 M sodium chloride + 0.1 M sodium carbonate solution. The ratio of ²³⁵ U to ²³⁸ U in the sorbent at the beginning of the experiment was 0.725 · 10 ~ ² . After one hour, the two phases are separated and a fresh solution of the above composition is added to the sorbent. A total of four such desorption steps are performed. After each step, the total uranium concentration of the solution was determined, followed by the total sorbent concentration of the sorbent and the ²³⁵ U: ²³⁸ U isotope ratio after the final step. From the results, the elemental separation factor of each step is calculated to be 1,150.

Example 9

Four desorption steps were carried out as described in Example 8, except that 0.1 M sodium carbonate solution was used for desorption. From the results, the elemental separation factor of each step is calculated to be 1,120.

Example 10

Four desorption steps were carried out as described in Example 8, except that 0.1 M hydrochloric acid was used for desorption. From the results, the elemental separation factor of each step can be calculated as 0.980.

Example 11

20.0 ml of a 0.1 M solution of tri-n-octylamine in basic form are mixed with 100.0 ml of 0.01 M uranyl sulfate + 0.1 M sodium sulfate in a laboratory shaker with stirring. The stock solution has a ²³⁵ U: ²³⁸ U isotope ratio of 0.725-10 ^-2 (a compound made of uranium, of course). During extraction, samples are taken from the aqueous phase, which determine total uranium concentration (spectrophotometrically using Arsenazo I reagent) and Aldermaston-Micromass 30 mass spectrometer to determine the isotope ratio. From the results the time dependence of the separation factor can be calculated:

time (sec) 0 15 30 60 120 240 total uranium concentration 0.01 0.0083 0.0069 0.0063 .0071 .0071 separation factor 1,000 1,029 1,003 1,004 1,000 1,000 5

-5183570

The principle of the directed distribution method can also be used to separate components present at different concentrations or with different transport rates between phases, i.e. in cases where the sorption and desorption rates of each component are different. In addition to separating isotopic mixtures, the method is suitable for the separation of rare earth metals, zirconium hafnium, radium 226-barium and similar components with close properties. The method is preferably applicable to the separation of high purity materials, analytical grade materials or nuclear and semiconductor materials.

Claims (8)

1. A process isotopes Two-phase separation system in the directional distribution method to make use of the isotope-koncentrációshatás, wherein ^2, characterized in that a two-phase system in which one phase concentration of the solution or mixture from ΙΟ ^6M and saturation of izotópkomponensek or ligands, wherein each izotópkomponensek the molar ratio is 1:10 ^{5 to} 1: 10 ⁵ and optionally contains 2 complexing or chelating agents and the other phase is a solid sorbent having a particle diameter of preferably 10 to ^{6 to 2 2} m or an extraction agent optionally applied to a support in the dark or 2 5 -10 ^{2 9} -10 nm light at ⁵ ° -1Ö 3 1 O ² K ² 10 -10 rpm / sec is heated to ICR ^{6 1} -10 m / sec flow speed in case of mixing or column arrangement IO * ² -10 ⁶ seconds, followed by desorption or reextraction, given The isotopes are isolated from the phases separated by the use of excipients. 2. The process of claim 1 wherein the one phase is an aqueous or non-aqueous solution of the isotope components or ligands 4 or a gaseous mixture of the isotope components or a gaseous mixture of the isotope components. 3. A method according to claim 1 or 2, characterized in that a two-phase system 4 is used in which the other phase is a Based on solid sorbent having a particle diameter of 10 ~ ^{4 to} 10 ~ ³ m, such as biosorbent or cellulose based on highly acidic cation exchange or lower fungi such as Penicillium chrysogenum mycelium A sorbent or an extraction agent such as tributyl phosphate or trioctylamine, optionally bonded to a carrier such as teflonone, silica or cellulose. 4. eljá'3 Rás embodiment of any of the preceding claims, characterized in that compounds of the complexing agent additive carbonate, sulfate, citrate, chloride or ethylene diamine chelating agent tetraecetsavionokat containing chelating functional groups, e.g., carboxyl or hydroxyl group ^{of 5} or phosphorus-, nitrogen- or a sulfur-containing sorbent or extraction agent. 5. A method according to any preceding embodiment, wherein the de ⁰ sorption or reextrakciós as excipients sodium carbonate, sodium sulfate, sulfuric acid, nitric acid, hydrochloric acid or compounds having a chelating group such as citrate or ethylenediamine tetraecetsavionokat used alone or ⁵ in admixture with 10 ^-3 In the total concentration between M and saturation. 6. A process according to any one of claims 1 to 3, characterized in that a two-phase system is used in which one of the phases θ is ^23S U (IV) and ²³⁸ U (VI) isotope components and compounds containing nitrate, sulfate or carbonate ions 10 * ² - Kh ¹ M aqueous solution of the total concentration in which the molar ratio of ²³⁵ U to ²³⁸ U isotopes is between 1: 500 and 1: 100. - 7. A method according to any preceding embodiment, wherein the phase mixing of the dark or light of wavelength 250 to 650 nm 273 to 373 ° K in case of 0.80 to 12.0 rpm / sec speed mixer or ko lonnaelrendezés ^{0 4} 10 -10 m / sec at a flow rate of 10 ^{2 to} 10 ⁴ sec. 8. Sections 1-5. A method according to any preceding embodiment, wherein the desorption or reextrakciós excipient nátrium5 chloride and sodium carbonate or hydrochloric acid 10 ^-1 to 1.5 M concentration was used.