Adsorption of uranium, as UO22+, and thorium, as Th4+, has been studied using a modified fly ash bed. Effects of pH and various ions like La3+, Fe3+, Ce4+, SiO32- etc., have been examined. Synthetic mixtures of UO22+ and Th4+ in different concentrations were passed through the bed and eluted separately with various selective reagents viz. ammonium carbonate, sodium carbonate and acetic acid-sodium hydroxide buffer. Separations of these elements at ppm level are shown to be very effective. The separation of uranium and thorium in the presence of lanthanides in monazite sand has been studied successfully. In the analysis of monazite sand, the oxalate precipitation has been avoided. The method is simple and of very low cost. The modified fly ash bed can also be used to remove uranium from contaminated water.
The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.
An internal mono-standard method has been proposed for multi element analysis. This method gives the relative concentration of the elements in a sample of non-standard shape and size. It utilizes an in-situ relative efficiency calibration and hence, does not need the cumbersome procedures, otherwise required to correct for -attenuation in the sample. To validate this method, the relative concentration of elements in IAEA RM's SL-3 and Soil-7 were analyzed with sample amounts ranging from a few milligrams to grams. The samples were counted in different non-specific geometries. The results are in good agreement with the recommended values, suggesting that this methodology could be applied for the analysis of samples of non-standard size and shape, and in principle, for the analysis of large samples.
Present status of work on charge and mass distribution in medium energy fission of compound nuclei produced using various target projectile combinations is reviewed. Systematics of charge distribution parameters and their dependence on excitation energy of the fissioning nucleus is presented. Variation of mass distribution with excitation energy and mass and charge of the fissioning nucleus is discussed. Qualitative explanation of the data has been sought in terms of existing theories of fission. The importance of charge and mass distribution studies in identifying the different reaction mechanisms in heavy ion induced reaction is highlighted.
Authors:R. Acharya, A. Nair, K. Sudarshan, A. Goswami, and A. Reddy
A summary of k0-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA)
is presented. The k0-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials
and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples
and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization
of neutron beam, determinations of detection efficiency and prompt k0-factors, and analytical applications.
Authors:A. Nair, A. Srivastava, A. Goswami, and B. Srivastava
Cumulative yields of short-lived ruthenium isotopes in the thermal neutron induced fission of235U,235U and239Pu have been determined using a fast radiochemical separation technique followed by gamma spectrometry. The cumulative yields of107Ru and103Ru in233U (nth, f) and107Ru and109Ru in239Pu (nth, f) are determined for the first time. The measured cumulative yields are converted to chain yields assuming normal charge distribution systematics for comparison with the literature data on chain yields.
Authors:A. Ramaswami, G. Gubbi, A. Goswami, B. Tomar, and S. Monohar
Formation cross sections of several fission products have been determined using recoil catcher technique followed by gamma-ray spectrometry in 12C induced fission of 232Th at Elab = 72 MeV, corresponding to Ecm just above the Coulomb barrier. The measured formation cross sections were used to get the mass distribution by using known charge distribution systematic. Critical data analysis was carried out to look for the signatures of transfer induced fission. However, within the experimental uncertainty of about 10%, no clear indication of transfer induced fission could be seen at this energy level. The mass distribution shows a single peaked broad Gaussian distribution with the most probable mass of 119.5±1.1 and FWHM of 40.6 mass units. The total fission cross section computed from the mass distribution curve is 771±50 mb.
Authors:T. Newton Nathaniel, K. Sudarshan, A. Goswami, and A. Reddy
A non-destructive assay technique based on prompt gamma-ray neutron activation analysis for the determination of 238U to 232Th ratio in the mixed oxide fuel materials has been established. The method uses closely spaced high energy gamma-rays in
the region of 4000 keV to 4150 keV enabling it to be applied for samples of any geometry and thickness without having any
correction for gamma-ray attenuations and detection efficiencies.
Authors:A. Nair, N. Chakravarty, A. Goswami, B. Srivastava, and Satya Prakash
Using radiochemical and gamma spectrometric technique the branching fractions in the beta decay of117Cd isomers and the internal transition branching of117mIn have been established. The beta branching fraction of117gCd
117gIn was obtained as 0.86±0.06 and the value of117mCd
117gIn was found to be less than 1%. The internal transitin branching and the isomer cross-section ratio were obtained as 0.31±0.02 and 0.197±0.002, respectively. From the measured isomer cross-section ratio the spin cut-off parameter was evaluated, which agreed with the value reported in the literature.
Authors:M. Goswami, A. Sarkar, B Sharma, V. Shrikhande, and G. Kothiyal
Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared
by melt and quench-technique. Total Mg content in the form of MgF2+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950C.
Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique
was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM)
was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low
Al2O3 concentrations (up to 10.5 mol%) both MgSiO3 and fluorophlogopite phases are present and at higher Al2O3 concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg2SiO4), respectively are found as major crystalline phases. The average thermal expansion co-efficient (aavg) of the glass samples
decreases systematically from 9.8 to 5.510-6C-1 and the glass transition temperature (Tg) increases from 610.1 to 675C with increase in alumina content. However, in glass-ceramic samples the aavg varies in somewhat
complex manner from 6.8 to 7.910-6C-1 with variation of Al2O3 content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.