R. A. Aliev

Plutonium sorption onto hematite colloids at femto- and nanomolar concentrations

Abstract The surface-mediated reduction of Pu(VI) upon sorption onto hematite colloids is addressed in the paper that bring some new light on the mechanisms of interaction of Pu in high valence states with different Fe(III) oxides. We study the sorption of Pu taken at two different total concentrations around 10−9 and 10−14 M using 239Pu and short-lived 237Pu tracer. In order to conclude on the mechanisms of Pu sorption onto hematite, the kinetics of sorption of Pu(IV) and Pu(VI) at two concenrations is studied as well as its leching behavior. The rate limiting step in Pu(VI) sorption is its surface-mediated reduction. The experimental evidence of the polymerization of Pu(IV) on the surface taken at Pu total concentration of ∼10−9 M is presented based on the kinetics of sorption and leaching behavior.

Production of actinium, thorium and radium isotopes from natural thorium irradiated with protons up to 141 MeV

Abstract Cross sections of 225Ac, 227Ac, 227Th and 228Th in thorium-232 targets irradiated with protons in the energy range 21–141 MeV have been measured. Based on these data, production yields of 225Ac and 223Ra in thick thorium targets have been calculated. It is possible to produce in proton energy range 60–140 MeV about 96 GBq (2.6 Ci) 225Ac per 10-d irradiation with 100 μA proton beam current and 10-d decay, and much higher amount of 223Ra. The impurities of 227Ac and 224Ra are important and need to be assessed for further medical applications.

Production of 225Ac and 223Ra by irradiation of Th with accelerated protons

The possibility of producing 225Ac and 223Ra by irradiation of natural 232Th with medium-energy protons was examined. Thorium foils were irradiated with 90-, 110-, and 135-MeV protons at the accelerator of the Institute for Nuclear Research, Russian Academy of Sciences, in Troitsk (Moscow oblast). The cumulative production cross sections for 225Ac were 6.7 ± 0.9, 9.8 ± 1.9, and 13.9 ± 1.5 mb, and for 227Th (223Ra precursor), 43 ± 5, 37 ± 6, and 35 ± 4 mb, respectively. Based on the experimental data and theoretical calculations, the possible yields of 225Ac and 223Ra in irradiation of thick thorium targets at various accelerators were determined. An efficient procedure was suggested for isolating the products from the irradiated targets: 225Ac, by liquid extraction and extraction chromatography, and 223Ra, by sublimation from a thorium-lanthanum melt followed by thermochromatographic separation in metallic titanium columns and extraction-chromatographic isolation of radium. The procedure allows production of large (units of curies) amounts of radiochemically pure 225Ac and 223Ra, which is promising for wide use of these radionuclides in nuclear medicine.

Isolation of Medicine-Applicable Actinium-225 from Thorium Targets Irradiated by Medium-Energy Protons

A method of isolation of actinium-225 for nuclear medical applications from thorium targets irradiated by protons is presented. It comprises liquid extraction and extraction chromatography separations. The method demonstrates high (> 85%) chemical yield and radionuclide purity of the final product. An impurity of 227Ac (0.1% at the end of bombardment) does not hinder 225Ac from being used for medical 225Ac/213Bi generators.

Extraction chromatographic behavior of actinium and REE on DGA, Ln and TRU resins in nitric acid solutions

The extraction-chromatographic behavior of actinium, rare earth elements and other radionuclides formed upon the irradiation of thorium by medium energy protons was studied. The k′ values for Ac(III), Ce(III) and La(III) in nitric acid solutions using Ln Resin, DGA Resin and TRU Resin (Triskem Int.) were determined. The optimal conditions for separation of Ac(III) and rare earth elements (REE(III)) were defined. The obtained results can be used to develop the multipurpose analytical procedure for actinium separation either for the needs of nuclear medicine or for radiochemical analysis of environmental samples.

69mZn-containing radiopharmaceuticals: a novel approach to molecular design

Abstract69mZn was produced and separated for medical applications. Possibilities and perspectives for production of radiopharmaceuticals based on 69mZn containing derivatives of thiazine, thiazoline and thiourea are considered. Each one of the latters is a zinc chelator and a nitric oxide synthase (NOS) effector at the same time. Cytotoxic effect of NOS activator and NOS inhibitors are shown in experiments with HL-60, K-562 and MOLT-4 cell lines and in bone marrow cells of the acute B-lymphoblastic leukemia patients. Some of those compounds are worthy to get selected for further application as radiopharmaceuticals including their antitumor speciements.

Production of 95gTc via 95Ru decay

Abstract A method is proposed to produce the short-lived radionuclide 95gTc via formation of the parent 95Ru. To produce 95Ru, the bombardment of molybdenum target of natural isotopic composition with α-particles and the irradiation of ruthenium of natural isotopic composition with bremsstrahlung photons were used. It is shown that the isotopic purity of 95gTc produced by suggested methodology is significantly higher compared with other techniques. Attention was also paid to the production of side products such as 95mTc, 96Tc, and 97,103Ru, in order to utilize optimally the energy of the alpha particle beam.

Radiography and local microanalysis for detection and examination of actinide-containing microparticles

A procedure was proposed for examination of the spatial microdistribution of fissile actinide isotopes (235U, 239Pu) in various environmental objects (soils, bottom sediments, aerosols, colloid material). Complex analysis of natural actinide-containing microparticles involves α-track radiography (ATR) and neutron-induced fission track radiography (NITR), highly sensitive nondestructive methods for determining the spatial microdistribution of α-emitting and fissile actinides, respectively, and scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) and secondary ion mass spectrometry (SIMS) for local microanalysis of the general elemental and isotope composition of the particles and determination of the morphology and size of the particles. The actinide-containing particles were localized using an SEM microgrid with electrodeposited 239Pu. Particles characterized by a high concentration of actinides were detected by SEM and SIMS, while those with a low content of actinides, by track radiography followed by fragmentation of the sample for subsequent analysis (γ-ray spectrometry etc.).

Separation of radioisotopes of terbium from a europium target irradiated by 27 MeV α-particles

Abstract A method for obtaining 156, 155, 154m2, 154, 153Tb radiotracers by the irradiation of a europium oxide target of natural isotopic composition by 27 MeV α-particles is proposed. Terbium can be efficiently separated from bulk of europium by the reduction of the latter by zinc in an acidic solution and precipitation as EuSO4. The optimum Zn/Eu3+ and (NH4)2SO4/Eu3+ molar ratios are 20 and 3, respectively. Terbium is additionally purified from europium and gadolinium by extraction chromatography using LN Resin. It is demonstrated that optimum separation is attained in 0.6 M HNO3. The Tb/Eu separation coefficient was ~5·105. The yield of terbium was about 90%. Time of all steps was 1.5–2 h. The proposed procedure makes it possible to obtain no carrier added terbium radiotracers.

Artificial radioactivity of the White Sea

Vertical profiles of 137Cs in bottom sediments collected from various sites of the White Sea are reported. From these profiles, the 137Cs inventory in the bulk of sediment was estimated to be 270–3300 Bq m−2, and the surface contamination of sediment, 7.1–46.5 Bq kg−1. In the most of the sediment cores, 137Cs was detected to a depth of >20 cm. The highest activity of 137Cs was usually observed in the 1–2-cm layer. The mean specific radioactivity of 137Cs in the seawater was 4.1 Bq m−3.