Isomeric yields of130Sb,132Sb,134I, and136I in the thermal neutron fission of235U

Isomer yield ratios of130Sb,132Sb,134I and136I isomers formed in the thermal neutron fission of235U have been calculated from our previous experimental studies that led to the identification of these species. In those studies the iodine and antimony fractions formed in fission were rapidly separated and the decay of γ-rays belonging to each isomer pair were followed using Ge(Li) detectors and a multichannel analyzer. The isomer ratios were calculated from growth and decay considerations of these γ-rays. The results are compared with the recently published values obtained with an on-line isotope separator, those from LOHENGRIN, and those from model calculations. Angular momenta of fission fragments corresponding to the measured isomer yields have also been calculated. © 1992 Akadémiai Kiadó

Radiochronological methods as tools to study environmental pollution

The study of the environmental impact of natural and anthropogenic events forms the essence of environmental pollution considerations. The nature of the polluting species as well as their time distributions are of primary importance with respect to identifying the polluting sources. Sediments are the most frequently used materials in such studies. Sediments act as the ecological memories of the environments of their formation. Besides classical chronological methods, radiochronological methods developed recently gave a big impetus to environmental pollution studies. One of the key radioisotopic technique is to utilize 210Pb, a product of the 235U radioactive series to date the last 200 years of the sediments. A number of supporting indicators are also utilized. One of them being anthropogenic 137Cs which is used as a time-marker. Large amounts of 137Cs radioactivity was released to the environment during 1954-1963, in time of the most intense atmospheric nuclear arms testing and again in 1986 during the Chernobyl nuclear accident. These intense 137s activities form time-markers throughout sediment cores corresponding to their release years. During our studies extending over several years we have used radiochronological methods in dating several sediment cores from Zurich and Constance Lakes in Switzerland from east coast of Spain, Sea of Marmara, from the Black Sea region, Southern coast of Turkey and from North Cyprus. The distribution of several elemental concentrations of importance in pollution considerations along sediment cores were also determined. These studies allowes proposing time frames to pollution events and help inqueries in tracing possible sources of pollution. © Springer-Verlag Berlin Heidelberg 2011

Radiochronology of lake sediments

Sediment cores from Lakes Zurich, Constance, from the Sea of Marmara and from southern Turkey, northern Cyprus and eastern Spain were dated using natural 210Pb, fallout 137Cs and cosmic-ray produced 7Be radionuclides. Constant activity regions in the uppermost sections of sediments from Lake Zurich and the Sea of Marmara were attributed to post-depositional mobility of 210Pb in the former case and to bioturbation in the latter. A serious discrepancy exists between the 210Pb dating of Sea of Marmara sediments and those obtained by organic carbon based methods. The elements Zn, Cu, P and Pb were enriched in the upper sections of the sediment cores corresponding to the last 200 years. The increased metallurgical activities as a result of reforms in the Ottoman Army during the 18 th century could be the most likely cause

Instrumental neutron activation analysis of blood serum

Instrumental neutron activation analysis has been used to determine 15 trace elements in twelve blood serum samples taken from healthy students at Bilkent University in Ankara. The method allowed the determination of Sc, Cr, Mn, Fe, Co, Zn, Se, Rb, Cs, Ce, Eu, Tb, Hf, Ta and Hg, which occur at the μg.ml-1 to ng.ml-1 levels. There are no values reported for Tb, Hf, Ce, Eu and Ta before. The other results are compared with the values reported in the literature. Most are in the range of the reported values except for Fe, Zn, Se and Cs. © 1995 Akadémiai Kiadó

Thermodynamic parameters of Cs+ sorption on natural clays

The sorption behavior of Cs+ on kaolinite, chlorite-illite, and bentonite clays as a function of time, cation concentration, and temperature was studied using the radiotracer method. Sorption data were well represented by Freundlich and Dubinin-Radushkevich type isotherms. Bentonite was found to have the highest sorption capacity and the highest exchange affinity to Cs+. In all three cases Cs+ sorption was found to be exothermic with ΔH° (kJ/mol) -13, -8, -19 and ΔS° (J/mol·K) -15, 31, and -3 for kaolinite, chlorite-illite, and bentonite, respectively. Negative ΔG° values were obtained in all cases, indicating the spontaneity of sorption. The magnitudes of ΔG° suggest that ion exchange is the primary sorption mechanism

Sorption of radioiodine on organic rich soil, clay minerals and alumina

Batch method was used to investigate the sorption behavior of radioiodine on organic rich soil, alumina, chlorite-illite clay mixture and bentonite.131I was used as tracer. The grain sizes of the samples used were all below 38 μm. A rather slow kinetics was observed for the adsorption of radioiodine on organic rich soil. The distribution ratio increased with increasing solution/solid (V/m) ratio, and the contact time. The pH of the synthetic groundwater did not change the distribution ratio appreciably. The soil biomass however, showed a striking effect on the adsorption of radioiodine. Among the clay minerals, the highest distribution ratio value was found for chlorite-illite clay mixture. All the values were however well below those of the organic rich soil. The sorption data were fitted to Freundlich and Dubinin-Radushkevich types isotherms. Means energies of adsorption, as well as the affinity ratios of the sorption sites to iodine and chlorine were calculated. © 1994 Akadémiai Kiadó

Sorption of phenol and radioactive cesium onto surfactant modified insolubilized humic acid

In this study, the sorption behavior of two important contaminants, phenol and radioactive cesium (137Cs), onto surfactant modified insolubilized humic acid (SMIA) were investigated as a function of time, sorbate concentration utilizing the radiotracer method and UV-Vis spectroscopy. Phenol sorption process was well described by both Freundlich and Tempkin type isotherms, and cesium sorption was described by Freundlich and Dubinin-Radushkevich isotherms. It was found that SMIA adsorbs both cations and phenolic substances. Kinetic studies indicated that adsorption behavior of phenol obey the pseudo second order rate law. FTIR spectroscopic technique was used to understand the structural changes during modification process with surfactants. © 2010 Akadémiai Kiadó

Temperature effects in barium sorption on natural kaolinite and chlorite-illite clays

The sorption of Ba2+ ion on natural kaolinite and chlorite-illite clays was investigated at different initial concentrations and temperatures using the radiotracer method. The sorption data were well described by Freundlich and Dubinin-Radushkevich isotherms. Ba2+ sorption on both clays showed an exothermic behavior with ΔH° (kJ/mol) values being -7 and -5 for sorption on kaolinite and chlorite illite mixed clay, respectively. The ΔG° values indicate that the sorption was spontaneous with sorption energies corresponding to ion-exchange type sorption. X-ray diffraction studies showed that no significant change in the matrix of the clays occurred upon Ba2+ sorption

Characterization of Sr2+ uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT

The sorption behavior of Sr2+ ions on natural minerals rich in kaolinite and magnesite was studied using SEM/EDS, XPS, XRPD, AAS/AES and DRIFT techniques. Quantitative analysis of the XPS data shows that magnesite is more effective in Sr2+ uptake than kaolinite. DRIFT spectra and XRPD patterns indicate that the structures of both minerals were not affected upon Sr2+ sorption. Intercalation of DMSO in kaolinite lamellae aiming at increasing the interlayer space did not significantly enhance the sorption capacity of the clay towards Sr2+ probably due to the lack of a negative charge on the accessible sites. EDS mapping indicated that while the sorbed Sr is equally distributed on surface of natural kaolinite, it was associated - to a larger extent - with the regions richer in Mg in the case of natural magnesite. Comparing the uptake mechanisms of natural magnesite with that of pure MgCO3, it was seen that while natural magnesite sorbed Sr2+ mainly through an ion exchange type mechanism, the formation of SrCO3 coprecipitate was detected on the surface of the MgCO 3 at higher loadings. © by Oldenbourg Wissenschaftsverlag, München

Sorption behavior of Co2+, Zn2+ and Ba2+ ions on alumina, kaolinite and magnesite

The sorption behavior of Ba2+, Co2+ and Zn2+ ions on alumina, kaolinite and magnesite have been investigated using the batch method.60Co,65Zn and133Ba were used as radiotracers. The mineral samples were separated into different particle size fractions using an Andreasen Pipette. The particle sizes used in the sorption experiments were all less than 38 μm. Synthetic groundwaters were used which had compositions similar to those from the regions where the minerals were recovered. The samples were shaken with a lateral shaker at 190 rpm, the phases were separated by centrifuging and adioactivity counted using a NaI(Tl) detector. Kinetic studies indicated that sorption onto the minerals took place in two stages with the slower process dominating. The highest sorption was observed on alumina. Both Freundlich and Dubinin-Radushkevich type isotherms were found to describe the sorption process well. The distribution ratio, Rd was found to be a function of the liquid volume to solid mass ratio. The Rd's for sorption on binary mixtures of minerals were experimentally determined and compared with those predicted from Rd values of each individual mineral. © 1994 Akadémiai Kiadó