V. A. Khalkin

Anion exchange behaviour of light rare earths in aqueous methanol solutions containing neutral nitrates : I. Separation of carrier-free light rare earths

Abstract The anion exchange adsorption and separation of the cerium sub-group rare earths were investigated in CH 3 OHNH 4 NO 3 IRA 400, CH 3 OHLiNO 3 IRA 400 and CH 3 OHLiNO 3 Dowex i systems. It was shown that in aqueous methanol solutions of ammonium nitrate the distribution coefficients of the light rare earths are linear functions of the nitrate concentration. Based on this, a simple scheme for the calculation of the probable location of the peaks in gradient elution, as well as a method for the determination of the distribution coefficients by means of gradient elution are presented.

ANION-EXCHANGE BEHAVIOUR OF LIGHT RARE EARTHS IN AQUEOUS METHANOL SOLUTIONS CONTAINING NEUTRAL NITRATES. II. MACRO--MICRO SEPARATIONS.

Abstract The separating power of methanolic solutions containing ammonium nitrate for the separation of trace amounts of light rare earths from macroamounts of adjacent rare earths was investigated. It was shown that anion exchange carried out from methanolic solutions of ammonium nitrate provides a useful means for the purification and analysis of the light rare earths. Methods for the purification of gadolinium and for the concentration of light rare earth impurities from gadolinium oxide and gadolinium metal samples are described in detail.

Generator of actinium-225

Dependence upon pH of Ac and Th distribution coefficients between the cation exchange resin and buffer citrate solutions had been investigated; the optimal conditions are suggested for effective separation of the elements in this system. These results are in successful accordance with such conditions calculated on the basement of Ac and Th citrate complex formation constants.The generator method for225Ac periodical separation from229Th samples is developed.229Th storage in solution between separations excludes the contamination of actinium final solution with radiolysis products and provides 100-% yield of this isotope and its high radiochemical purity. The parent nuclide loss after continuous use of the generator does not take place.

Separation of thallium-201 from Tl, Pb and Bi cyclotron target materials

Radiochemical methods of thallium-201 separation from proton-irradiated thallium, lead and bismuth targets have been developed. The procedures are based on the processes of coprecipitation, ion-exchange chromatography and high temperature gas chemistry. The purity of thallium samples complies with requirements of nuclear medicine for thallium-201 product.

Excitation Function and Yield for 97Ru Production in 99Tc(p,3n)97Ru Reaction in 20 – 100 MeV Proton Energy Range

Proton-induced reactions on 99Tc target were studied in order to evaluate the 99Tc(p,3n)97Ru reaction as a source of high radionuclidic purity 99Ru. Measurements of excitation functions for the main reaction 99Tc(p,3n)97Ru and competmg 99Tc(p,pxn)99m,96,95Tc reactions were performed in a stacked-foil experiment using gamma spectrometry. The maximum cross section for 97Ru formation in the first reaction was found to be 440 mb (±15%) at 32 MeV. Results are compared With calculations based on the hybrid model of nuclear reactions (Overlaid Alice and Alice 85/300). For the proton energy range 99 – 20 MeV the cumulative 97Ru yield of 10.5 mCi/μA·h was estimated.

Radiochemical separation of radiothallium from proton-irradiated lead

Absorption of carrier-free T1 from nitric acid solutions of lead by ammonium 12-molybdophosphate fixed in the matrix of porous Teflon (AMP-sorbent) has been investigated. Effective separation of T1 and Pb is shown to take place. Elution processes of T1 from AMP-sorbent have been investigated. It is found that complete extraction of T1 is achieved upon dissolving AMP in concentrated ammonia. Further purification and concentration of T1 are performed by means of cation exchange chromatography on Dowex-50 or KU-2 resins. Investigation of high temperature behaviour of T1 ultramicroamounts in Pb melt showed that T1 is quantitatively separated out into the gas phase when fluorinating additions of PbF2 or NaF solid salts covering the melt surface are used. The volatile compounds of radiothallium formed were transported by a stream of inert gas (He or N2) from the evaporation zone to the thermochromatographic column, where they were sorbed on the surface in a limited zone with the maximum at ∼240 °C. Liquid and gas thermochromatographic methods for separation of carrier free radiothallium from protonirradiated lead material have been developed. The radiochemical, chemical and radionuclidic purity of T1 samples complies with requirements of nuclear medicine for201T1 product. Both methods ensure ∼95% chemical yield of T1 and take about two hours each.

ELECTROMIGRATION OF CARRIER-FREE RADIONUCLIDE IONS BISMUTH COMPLEXES IN AQUEOUS SOLUTIONS OF OXALIC, FUMARIC AND SUCCINIC ACIDS

The overall ion mobilities u of carrier-free radiobismuth have been measured in aqueous solutions of some dicarboxylic acids (H(2)L)-xalic, fumaric and succinic-by means of a new version of the electromigration method in electrolytes consisting of HClO(4)/H(2)L, 0.20m H(+), mu = 0.20m; Na(H)ClO(4)/H(2)L, 0.05m H(+), mu = 0.20m; Na(H)ClO(4)/H(2)L, 0.05m H(+), mu = 0.25m; at 298.15 K. Mathematical processing of the experimental functions u = f([L(2-)]) allowed calculation of the mean individual stability constants K(n) and ion mobilities u degrees of the complex ions [BiL(n)](3-2n), n = 1, 2: [Bi(C(2)O(4))](+), log K(1) = 7.65 (8), u degrees = +2.26 (5) x 10(-4) cm(2). sec(-1).V(-1); [Bi(C(2)O(4))(2)](-), log K(2) = 4.81 (2), u degrees = -1.63 (64) x 10(-4) cm(2).sec(-1).V(-1); [Bi(C(4)O(4)H(2))](+), log K(1) = 6.90 (20); [Bi(C(4)O(4)H(4))](+), log K(1) = 8.76 (48).

Electromigration of carrier-free radionuclides : III. Oxalate and tartrate complexes of ytterbium(III_ in aqueous solution

Abstract The dependences of the overall ionic mobilities, u , of Yb(III) on the oxalate (C2O2−4) and tartrate (C4H4O2−6) concentrations in aqueous nitrate electrolytes of overall ionic strength 0.01 and temperature 298.1(1)K were obtained by direct measurements of the electromigration mobilities of carrier-free 169Yb-Yb(III). Mathematical processing of the experimental data allowed the individual concentration constants of Yb(III) to be determined: [Yb(C2O4)]+, log K1 = 5.80(5); [Yb(C2O4)2]−, log K2 = 4.06(3); [Yb(C4H4O6)]+, log K1 = 4.61(6). The individual ionic mobilities, u0i, of the ions were u0Yb3+ = +6.01(5) · 10−4 cm2 s−1 V−1, u0[Yb(C2O4)]+ = + 2.5(2) · 10−4 cm2 s−1 V−1, u0[Yb(C2O4)2]− = − 2.5(1) · 10−4 cm2 s−1 V−1, u0[Yb(C4H4O6)]+ = + 2.3(5) · 10−4 cm2 s−1 V−1. It is shown that Yb(III) is not hydrolysed in neutral (pH

Excitation Function for 178W Production in the 181Ta(p,4n)178W Reaction over Proton Energy Range 28.8-71.8 MeV

Ta (T\¡2 = 9.3 min) is of a certain interest to nuclear medicine. It can be produced from a generator following the reaction Ta(p,4n)W Ta. The excitation function for this reaction was measured over the proton energy range of 28.8 — 71.8 MeV. Natural Ta in metallic form was used as target material. The cross sections were measured using a conventional stacked foil technique. Our measurements indicated that the maximum cross section of the excitation function is (495 ± 74) mb at 40 MeV. The error in the absolute cross section data was estimated to be ±15%. The results are compared with previous experimental data and theoretical calculations based on the Hybrid Model of nuclear reactions using the well developed computer code Overlaid Alice. With a natural thick tantalum target and 65 MeV proton beam, yields of W are of the order of (1.3 ±0.20) mCi/μΑΙι.

Cross Sections for the 100 MeV Proton-Induced Nuclear Reactions and Yields of some Radionuclides used in Nuclear Medicine

Cross sections and yields have been determined for some radionuclides, frequently used in nuclear medicine (52Fe, 77Kr/77Br, 82Sr, 123Xe/123I, 128Ba, 201Tl), by bombardment of natural and enriched targets with protons of energy ≤ 100 MeV. The experimental cross sections are compared with the excitation functions calculated by the code Overlaid ALICE in the energy range from the thresholds up to 100 MeV. At the end of bombardment the thick target yields were as follows (mCi/μA·h, in the selected energy range): for 52Fe from 55Mn — 0.8 (36–100 MeV) and from 59Co — 0.1 (64–100 MeV); 77Kr from 79,81Br — 313 (24–100 MeV); 82Sr from 85,87Rb — 0.43 (36–100 MeV); 123Xe from 127I — 270 (48–100 MeV); 128Ba from 133Cs — 8.4 (43–100 MeV); and for 201Tl from: 206Pb — 3.5 (48–57 MeV), 207Pb — 3.0 (57–68 MeV), 208Pb — 1.5 (68–76 MeV) 32 hours at the end of the bombardment.