RESUMEN

A methodology has been developed for the complete compositional characterization of lithium titanate (LTO) using neutron activation, which is quite challenging and no literature report is available so far. The concept of thermal neutron induced in-situ chain reactions 6Li(n,α)3H and 16O(3H,n)18F has been used for the determination of Li and O through the measurement of 18F activity. The method is capable of analyzing Li and O in percentage level as reported in the present analysis of two types of lithium titanate samples. Spectroscopic interference of the elements which can directly or indirectly affect the outcome, were evaluated meticulously. Determination of Ti was carried out using fast neutron activation through the product isotopes like 47Sc, 48Sc, generated via (n,p) nuclear reactions. Fast neutron activation methodology seems to be advantageous for Ti determination over thermal neutron activation, as it offers self validation through different isotopes and multiple gamma lines.

Asunto(s)

Terapia por Captura de Neutrón de Boro , Neutrones Rápidos , Isótopos , Litio , Neutrones

RESUMEN

This work focuses on the selective separation of Co from Zr and Nb, for the decontamination of pressure tubes from pressurized heavy water reactor. Initial experiments were carried out using the respective radiotracers. These laboratory scale studies explore the feasibility of using oxalic acid, a benign complexing medium, for the Zr-Nb matrix, with targeted sorption of trace levels of 60Co on cation exchange membranes. Sorption of Co(II) on the membrane followed pseudo second order kinetics and the equilibrium capacity was 1.89 meq g-1. Oxalic acid concentration was a trade-off between the loading of matrix elements and the % sorption of Co(II). Energy dispersive X-ray fluorescence (EDXRF) spectrometry was used for monitoring the sorption of Co on the membrane from inactive sample solutions. Sorption improved the EDXRF detection limits for Co from 50 µg in solution to 1.3 µg on the membrane, where the total concentration of the matrix elements in solution was 50 g L-1. EDXRF method was validated by spike recovery and radiotracer studies.

RESUMEN

The effects of different physico-chemical parameters on sorption of protactinium (Pa) on three different iron oxides (goethite, hematite and magnetite) were studied. The sorption of Pa(V) on all the three iron oxides was low at pH 1, increased to ~ 90% at neutral pH and then decreased slightly above pH 9. Presence of humic acid increases the sorption of Pa(V) on iron oxides in acidic medium whereas sorption is reduced in basic medium. The classical methods like ionic strength, time and temperature dependent sorption studies have been used for the elucidation of the sorption mechanism of Pa(V) on iron oxides. Physisorption in acidic pH and chemisorption in basic pH are the most probable mechanisms. The study demonstrates that classical method alone can be used for the sorption mechanism investigations in the circumstances where it is difficult to have spectroscopic evidences.

RESUMEN

The sorption of Nb(V) on pyrolusite has been studied and the effect of pH, ionic strength, humic acid, temperature and equilibration time were also investigated in a series of batch equilibrium experiments. The sorption was found to be affected by solution pH, ionic strength and humic acid. The sorption was high in neutral/near neutral pH (~96 %) but lower sorption was observed both in acidic (~55 %) and basic (~85 %) media. Sorption was decreased in acidic pH with increase of ionic strength and reverse effect was seen in basic pH although the effect is less prominent. Presence of humic acid causes enhancement of sorption in acidic pH whereas sorption declined in basic pH. The sorption process is endothermic in acid medium and exothermic in basic medium. In acid medium the sorption is entropy driven process. Kinetics of the sorption study was found to follow pseudo first order in acidic pH whereas pseudo second order in basic pH.

RESUMEN

Determination of impurities namely Ca, Mn, Fe, Ni, Zn, Sr and Pb in graphite by energy dispersive X-ray fluorescence spectrometry is described using microfocused synchrotron radiation. The internal standard and standard addition methodologies were adopted for quantification and the results were compared with tube-based X-ray fluorescence spectrometry. Analysis of the results by the F and t-tests revealed their statistical equivalence. Synchrotron measurements improved the detection limits by an order of magnitude compared to the tube based technique. Cr and Zr, which were below the quantification limit in tube based technique, were also quantified by synchrotron based technique.