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  • Author or Editor: B. Tomar x
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Abstract  

The after effects of β -decay on time differential perturbed angular correlation (TDPAC) spectra of II–VI semiconductor CdS have been studied using β -emitting111Ag as well as111mCd as probe nuclei. The TDPAC spectrum of111Ag in CdS exhibits a time dependent interaction indicating that the preceding β -decay leaves the daughter nucleus in an excited state. The recovery time (τg) of the probe atom was found to be 16±6 ns while Abragam and Pound's relaxation time (τkr) was found to be 9±2 ns. The results show that β -decay does change the chemical environment around the probe atom.

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Abstract  

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.

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Abstract  

149Gd was produced from the 12C induced reaction on natural praseodymium target. No-carrier-added (nca) 149Gd was separated from the bulk target matrix by liquid–liquid extraction (LLX) using cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. High separation factor of 2,450 was achieved at the optimal experimental condition when 1% HDEHP and 0.1 M HCl were used as organic and aqueous phases respectively. The result was also compared with the previous reports.

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Abstract  

The classical chemistry like precipitation technique is relevant even in modern days trans-disciplinary research from the view point of green chemistry. A definite demand of no-carrier-added (nca) cadmium tracers, namely, 107,109Cd, has been realized for diverse applications. Development of efficient separation technique is therefore important to address the purity of the tracers for various applications. No-carrier-added 107,109Cd radionuclides were produced by bombarding natural silver target matrix with 13 MeV protons, which gave ~15 MBq/μA h yield for nca 107Cd. The nca cadmium radionuclides were separated from the natural silver target matrix by precipitating Ag as AgCl. The developed method is an example wherein green chemistry is used in trans-disciplinary research. The method is also simple, fast, cost effective and environmentally benign.

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Abstract  

An alternative reaction route for the production of111In from rhodium target bombarded with a12C beam has been developed. Sulfate fusion was adapted for dissolution of the irradiated rhodium metal target. Indium was coprecipitated with La(OH)3 and purified by solvent extraction of the InBr3 complex into di-isopropyl ether and back extraction in 6M HCl. The chemical yield of the separation, determined using105Rh as tracer, was found to be above 90%. The radionuclidic purity of the separated111In satisfies the requirement prescribed for radiopharmaceutical preparations. The radioactivity yield achieved using this route was about 0.2 MBq/μAh.

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Abstract  

An emulsion liquid membrane (ELM) containing di-2-ethylhexylphosphoric acid (D2EHPA) as the carrier extractant and SPAN 80 as the surfactant was used to pre-concentrate Am3+ from dilute acid solutions. Effects of various factors such as: external phase pH, internal phase conditions, equilibration time, D2EHPA concentration, SPAN 80 concentration, etc. on Am3+ mass transfer were investigated. Emulsion was broken by the addition of solvents such as acetone and the actual mass transfer obtained after breaking the emulsion agreed well with that obtained by the difference method.

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Abstract  

Cumulative fission yields of rare earth isotopes have been determined in the spontaneous fission of252Cf by fast radiochemical separation and gamma-ray spectrometry. The determined yield values are compared with the available literature data. The yield values for147Nd,151Nd and151Pm differ from the reported values. The yield for145Ce is determined for the first time.

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Abstract  

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 E lab = 72 MeV, corresponding to E cm 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.

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Abstract  

Release of long-lived radioactivity to the aquatic bodies from various nuclear fuel cycle related operations is of great environmental concern in view of their possible migration into biosphere. This migration is significantly influenced by various factors such as pH, complexing ions present in aquatic environment and sorption of species involving radionuclides on the sediments around the water bodies. 241/243Am are two major radionuclides which can contribute a great deal to radioactivity for several thousand years. In the present study, 241Am sorption on natural sediment collected from site near a nuclear installation in India, has been investigated under the varying conditions of pH (3–10) and ionic strength [I = 0.01–1 M (NaClO4)]. The sorption of Am increased with pH of the aqueous medium [10% (pH 2) to ~100% (pH 10)], which was explained in terms of the increased negative surface charge on the sediment particles. There was marginal variation in Am(III) sorption with increased ionic strength (within error limits) of the aqueous medium suggesting inner-sphere complexation/sorption process. Sediment was characterized for its elemental composition and structural phases using Energy Dispersive X-Ray (SEM-EDX) and X-Ray Diffraction (XRD) techniques. Zeta-potential measurement at I = 0.1 M (NaClO4) suggested that Point of Zero Charge (pHPZC) was ~2, indicating the presence of silica as major component in the sediment. Kurabtov plot using sorption data as a function of pH at fixed I = 0.1 M (NaClO4) indicated the presence of multiple Am(III) species present on the surface. Potentiometric titration of the suspension indicated the presence of mineral oxide like behavior and assuming a generic nature (≡XOH) for all types of surface sites, protonation–deprotonation constants and total number of sites have been obtained. The sorption data has been modeled using 2-pK Diffuse Double Layer Surface Complexation Model (DDL-SCM). ≡XOAm2+ has been identified as the main species responsible for the sorption profile.

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Abstract  

LIII edge X-ray Absorption Fine Structure (XAFS) spectroscopic study of Eu(III) sorbed on γ-alumina from aqueous solutions of different pH (values ranging from 6 to 8) has been carried out at XAFS beam line of Elettra Synchrotron facility, Italy, in transmission mode. Extended X-ray Absorption Fine Structure spectra of reference compounds, namely, Eu2O3, Eu(OH)3 and Eu-aquo complex in solution, were also measured. The data were analyzed using the IFEFFIT suite of code. XAFS spectra of the sorption samples is dominated by the Eu–O near neighbor co-ordination at distance 2.4 ± 0.1 Å. 8–9 oxygen atoms, coming from both coordinating water molecule and oxygen atoms from alumina surface, surround the Eu(III) in the surface complex. Next near neighbor atoms in all the sorption samples consist of Al at distance ~3.6 and 3.8 Å, which on comparison with literature data indicates towards Eu(III) bidentate binding to apical oxygen of two different alumina octahedra on γ-alumina surface.

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