Yu. A. Sapozhnikov

Behavior of Cs, Np(V), Pu(IV), and U(VI) in pore water of bentonite

Sorption of Cs, Pu(IV), Np(V), and U(VI) with bentonite from solutions was studied. Physicochemical species of radionuclides in the liquid phase were determined, the sorption mechanisms were established, and the influence of bentonite colloids on the behavior of radionuclides was studied. It was shown that Cs is sorbed by the ion-exchange mechanism, whereas the sorption of actinides at pH > 5 is governed by the reaction with surface hydroxy groups of betonite, and at pH < 5 the competing processes are ion exchange and complex formation. Reduction of Np(V) and U(VI) to Np(IV) and U(IV) in the solution with Fe(II) compounds present in the system was proved by the extraction method. Various methods of separating the solid phase were used in studying the dependence of the distribution coefficients of Np and Pu on the ratio of pore water and bentonite; it was shown that Np and Pu are sorbed on bentonite colloids.

Determination of lead-210 in bottom sediments via bismuth-210

Determination of lead-210 in bottom sediments is applied for evaluation of sedimentation rates and sediments ages by concentration profiles of disequilibrated lead-210 from atmospheric sources. Advences in low level liquid scintillation spectrometry (LS) fitted for natural radioactivity measurements, permit to combine the possibility of immediate bismuth-210 separation with its radioactivity registration using LS spectrometer Quantulus (LKB-1220, Wallak, Finland). The method was tested on bottom sediment samples from Baltic Sea shelf, collected during the 76th cruise of RV “Academician S. Vavilov”. The proposed method of separation, purification and chemical yield determination is characterized by simplicity, rapidity and may be used in routine analysis.

Extraction of Sr(II), Ag(I) and Pb(II) by some oxa-tia- and tia-crown ethers

Liquid-liquid extraction of several cations by some oxa-tia- and tia-crown ethers was studied. Sr(II), Pb(II) and Ag(I) were taken as hard, borderline and soft Lewis acids, respectively. Trace amounts of210Sr and110mAg were used as chemical yield monitors. The results were explained by the Pearson theory. Some of the examined compounds posses high affinity towards Ag(I) and Pb(II) extraction. The distribution coefficent for Ag(I) reached the value of 140.

The sorption of 90Sr from natural waters by alginates

Abstract The analytical applications of alginates, obtained from the marine algae Laminaria, for the pre-concentration of 90Sr from natural waters was studied. The sorption capacity for strontium in the samples investigated reached 30 mmol kg−1. The alginate sorbents were tested with sea water from the north-western part of the Black Sea over a wide range of salinity. The limit of detection for 90Sr in sea water with a salinity of 15‰ mBq dm −3 . The sorbents described are waste products of alginate manufacture and have a relatively low cost which considerably reduces the total costs of the analysis.

Rapid determination of strontium-90 in seawater

It is shown that Y2O3, YF3, LaF3, and CeF3 help concentrate 90Y from seawater. To determine 90Sr, YF3 is the best reagent because the effect of interfering lead and thorium radioisotopes is minimum in this case. It is proposed to preconcentrate 210Bi on PbS to eliminate its interference. To determine 90Sr we measure the Cherenkov radiation of 90Y concentrated on YF3 without prior elution.

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.).

Humic Acids as Barriers in Actinide Migration in the Environment

Humic acids (HAs) and fulvic acids (FAs) are the main components of natural waters that can influence the migration ability of cations. They form stable complex compounds with actinide elements that can change their solubility. In addition, HAs could be responsible for migration of colloidal species. The role of HAs in formation of geochemical barriers in actinide migration in the geosphere is discussed on the basis of results of laboratory experiments and speciation of plutonium and neptunium in field samples collected from the regions contaminated by human-made radionuclides.

Use of iron sulfide for removing polonium from liquid radioactive waste

Immobilization of polonium from low-level liquid radioactive waste (LRW) on iron monosulfide in batch and dynamic modes was studied. In batch experiments, the Po immobilization on FeS increases with increasing pH. At the solid phase: solution weight ratio of 1: 100, the degree of 210Ро removal from the solution in 2 days is 72.6% at pH 5.45 and 92.8% at pH 6.20. In filtration of LRW with pH 3–4 through a bulk filter of iron monosulfide dispersed in aluminosilicate gel and quartz sand, more than 99.4% of 210Ро is removed from the LRW volume exceeding the volume of the sulfide gel material by a factor of approximately 700. Iron monosulfide can be used for efficient removal of Po from low-level LRW.

Sorption of 90Sr and 90Y with stable and metastable modifications of calcium carbonate

A comparative study of sorption of 90Sr2+ and 90Y3+ cations from aqueous solutions saturated with respect to calcium carbonate on the metastable CaCO3 modifications (aragonite and vaterite) and also on the stable CaCO3 modification (calcite) was carried out at 20°C. The sorption of these radionuclides from the solutions containing Sr(NO3)2 carrier and without it was studied. Aragonite shows the highest sorption capacity for 90Sr2+, and these parameters are the lowest for calcite. All the CaCO3 metastable modifications irreversibly sorb 90Sr2+ and 90Y3+ cations and therefore show promise for sorptive decontamination of water from 90Sr.

Extraction of radionuclides from natural waters using alginates

Fourteen samples of wastes from algal plants were tested for possible analytical and/or technological use for90Sr and137Cs extraction from natural waters. Sorption experiments were carried out in static and dynanic conditions. It was noted that the examined sorbents posses high affinity for Sr2+. The sorption capacity reached the value of 4.72·10−3 mole/g. Simple and express analytical procedures for90Sr determination were developed and tested in the Dnieper estuary region.