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 m. 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.     

Influence of even nucleon numbers and closed shells on mass and charge distribution in low energy fission

Extensive experimental and evaluated yield data are now available for the fragments in low energy nuclear fission. Using these data we re-examined the influence of even nuclear numbers and closed shells on the mass and charge distribution in low energy fission. We used WAHL's Zp model and Ap model. We also examined the effects ofZ=50,N=82 and possiblyN=88 shells. A new method was developed based on two Gaussian curves for the even and odd products. TheEOZ andEON values calculated are based on these different methods and are seen to be consistent with each other in spite of the somewhat different definitions of the even-odd effect. The even-odd effect decreases with an increasing fissility parameter. TheEON values are substantially lower than the correspondingEOZ values, probably due to the effect of washing out the neutron pairing effect by prompt neutron emission. The magnitude of the even-odd effect varies with different mass regions. TheEOZ andEON values decrease as they go from asymmetric to symmetric regions in mass distributions.     

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 g.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.     

Solvent extraction behaviour of iodine and bromine in aqueous-organic systems,analogy with radioactive decay

The extraction of iodine and bromine under various conditions from their saturated aqueous solutions by CCl₄, C₆H₆ and o-xylene has been studied. The data obtained from the experiments carried out at various temperatures, for H₂O(I₂)−CCl₄ and H₂O(I₂)−C₆H₆ systems, exhibit an Arrhenius behaviour. The overall activation energy calculated for the extraction in the H₂O(I₂)−CCl₄ system, 650±50 cal·mol⁻¹ is lower than that of H₂O(I₂)−C₆H₆, 3600±300 cal·mol⁻¹. The use of the solubility parameter for the interpretation of the data in the extraction of iodine is investigated. The data obtained in multiple extractions are treated by using the analogy between extraction and radioactive decay. The half number of extraction for each system is determined. The complex curves obtained in the H₂O(I₂)−CCl₄ and H₂O(I₂) −Br₂)−CCl₄ systems are resolved into two components.     

Radiochronology of sediments from the Mediterranean Sea using natural210Pb and fallout137Cs

The²¹⁰Pb and¹³⁷Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct -ray spectroscopy. Sedimentation rates were derived for all locations using the²¹⁰Pb data. The rates range from 1.39±0.12 cm · y^–1 (0.50±0.04 g · cm^–2 · y^–1) to 0.08±0.01 cm · y^–1 (0.039±0.003 g · cm^–2 · y^–1). Except for one core, the¹³⁷Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of²¹⁰Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported²¹⁰Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm^–2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean.     

Radiochemical studies of the sorption behavior of strontium and barium

The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.⁹⁰Sr (29.1 y) and¹³³Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratioR _d, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8–10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K⁺, Sr²⁺, Ca²⁺ and Al³⁺ ions, respectively, prior to sorption studies with Ba²⁺ ions. The results of Ca²⁺ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba²⁺ ion exchanges primarily with the Ca²⁺ ion on the clay minerals.     

Cell‐loss control in multiplexing of VBR video over ATM networks

In this article we investigate the impacts of interspacing and source polling policies on the cell‐loss rates in transmission of variable bit rate video sources over Asynchronous Transfer Mode networks. We present a mathematical model that finds the approximate optimal starting times of the video sources that minimize the congestion at the multiplexer. Combined with the approximate optimal source starting times, we propose a source ordering and polling policy for reducing the cell‐loss rates. The proposed policy is tested against alternative policies using simulation of pre‐recorded video data. This revised version was published online in June 2006 with corrections to the Cover Date.     

The sorption behavior of C<Emphasis Type="SmallCaps">s</Emphasis><Superscript>+</Superscript> ion on clay minerals and zeolite in radioactive waste management: sorption kinetics and thermodynamics

In this work, Cs⁺ ion sorption on some clays and zeolite were investigated. ¹³⁷Cs was used as a tracer. Activities were measured with a NaI crystal gamma counter. The particle size distribution was determined by a laser sizer. Surface area of the particles were determined by BET (Brunauer, Emmett and Teller method). Structure analysis was made by using X-ray diffraction. The chemical compositions of the solid samples were determined using a ICAP-OE spectrometer. Kinetic and thermodynamic parameters were determined. Due to very high uptake results; clay and zeolite can be proposed as a good sorbents in waste management considerations.     

A characterization study of some aspects of the adsorption of aqueous Co2+ ions on a natural bentonite clay

The natural bentonite used in this study contained montmorillonite in addition to low cristobalite. The uptake of aqueous Co(2+) ions was investigated as a function of time, concentration, and temperature. In addition, the change in the interlayer space of montmorillonite was analyzed using XRPD, and the distribution of fixed Co(2+) ions on the heterogeneous clay surface was recorded using EDS mapping. The sorbed amount of Co(2+) appeared to closely follow Freundlich isotherm, with the sorption process showing apparent endothermic behavior. The relevance of the apparent DeltaH(o) values is briefly discussed. Analysis of the Co-sorbed bentonite samples using SEM/EDS showed that the montmorillonite fraction in the mineral was more effective in Co(2+) fixation than the cristobalite fraction. XRPD analysis demonstrated that the interlayer space of montmorillonite was slightly modified at the end of sorption.