Amol Mhatre

Anion dependence of transport of mercury ion through Nafion-117 membrane.

Studies on isotopic and ion-exchange kinetics of mercury ions in Nafion-117 membrane have been carried out with (203)Hg radiotracer in the presence of Cl(-) and NO(3)(-) in solution. The results of isotopic-exchange kinetics indicate that mercury ions diffuse into the membrane as monovalent cation from HgCl(2) solution while as divalent ion from Hg(NO(3))(2) solution. The studies on the kinetics of ion exchange of Hg(2+) with Na(+) follow the prediction of the Nernst-Planck equation when NaNO(3) is used as an external salt solution. The Nernst-Planck equation fails to predict the kinetics when NaCl is used as an external salt solution, indicating that the complexation of Cl(-) with Hg(2+) in the membrane influences the kinetics. Permeation studies using (203)Hg and (36)Cl radiotracer between two HgCl(2) solutions show that the permeability coefficients of mercury and chloride ions are the same, indicating the cotransport of mercury and chloride ions through the membrane. Ion-exchange equilibrium studies using a mixture of HgCl(2) and HNO(3) solution were carried out to ascertain the species transporting through the membrane. The equilibrium sorption of mercury in the membrane shows the uptake of an ionic species, presumably HgCl(+), not a neutral salt. The speciation diagrams, calculated as a function of pH, show wide divergence of species present in HgCl(2) and Hg(NO(3))(2) solution and explain the difference in membrane transport behavior for HgCl(2) and Hg(NO(3))(2) solution. The results show that any ion-exchange-membrane-based separation of Hg(2+) needs careful consideration regarding the anions present in the solution, as it influences the speciation of mercury and hence its transport behavior through the membrane.

High performance liquid chromatographic separation of 228,229 Th and 232,233 U and their estimation by α- and γ-ray spectrometry

The activities of 228,229Th and 232,233U from an irradiated ThO2 sample were radiochemicaly separated by using high performance liquid chromatography. Plancheted sources of the separated samples were made and the amount of 232,233U and 228,229Th were estimated by using alpha and gamma-ray spectrometric techniques. These estimations are important for the Th–U fuel reprocessing cycle of advanced heavy water reactor and accelerator driven sub-critical system.

Phosphate-bearing polymer grafted glass for plutonium(IV) ion-selective alpha spectrometry

A phosphate-bearing polymer thin film was covalently anchored on a glass substrate for alpha spectrometric determination of Pu4+ ions in aqueous samples. This method combined matrix elimination, preconcentration and source preparation into one-step sample manipulation. The thin polymer film was formed by first coupling 3-(trimethoxysilyl)propyl acrylate (TMSPA) on a hydrolyzed glass substrate by a sol–gel process, and simultaneously utilizing the double bonds of TMSPA for the UV-initiator-induced graft polymerization of bis[2-(methacryloyloxy)ethyl] phosphate monomers. The thin phosphate ligand bearing the thus formed poly(bis[2-(methacryloyloxy)ethyl] phosphate) (poly(BMEP)) film was characterized for homogeneity, physical morphology, and its affinity toward representative actinide ions such as UO22+, Am3+, Th4+ and Pu4+ in a HNO3 medium. Alpha track radiography and elemental mapping of the C and P atoms indicated uniform formation of the poly(BMEP) film on the glass substrate. Atomic force microscopy indicated a 10–15 nm thickness of the film, and the alpha spectrum of Pu4+-loaded glass@poly(BMEP) exhibited well defined alpha energy peaks without any significant loss of energy in the host matrix. The glass@poly(BMEP) film was found to sorb Pu4+ ions preferentially in 3 mol L−1 HNO3 in the presence of competing UO22+ and Th4+ ions. Am3+ ions did not sorb to a significant extent under similar conditions, even in the absence of Pu4+ ions. The Pu4+ ions loaded on the glass@poly(BMEP) substrate were quantified by isotope-dilution alpha spectrometry. This glass@poly(BMEP)-based alpha spectrometric method was applied successfully to quantify Pu in aqueous samples. The concentrations of Pu measured by this technique were reproducible within ±6% and required a minimum preconcentration of 2.95 Bq Pu activity in the glass@poly(BMEP) film. The measured Pu concentrations showed good agreement with those obtained by standard thermal ionization mass spectrometry.

Determination of europium content in Li2SiO3(Eu) by neutron activation analysis using Am-Be neutron source

Circulardiscs of Li2SiO3 doped with europium were prepared and a new activation procedure for the neutron dose estimation in a breeder blanket of fusion reactor is described. The amount of europium in the disc was determined by neutron activation analysis (NAA) using an isotopic neutron source. The average neutron absorption cross section for the reaction was calculated using neutron distribution of the Am-Be source and available neutron absorption cross section data for the 151Eu(n,γ)152mEu reaction, which was used for estimation of europium in the pallet. The cross section of the elements varies with neutron energy, and the flux of the neutrons in each energy range seen by the nuclei under investigation also varies. Neutron distribution spectrum of the Am-Be source was worked out prior to NAA and the effective fractional flux for the nuclear reaction considered for the flux estimation was also determined.

Donnan membrane equilibrium studies of mercury salts with Nafion-117 membrane

ABSTRACT The Donnan membrane equilibrium experiments using two compartment cell have been carried out to understand the effect of speciation on the transport behavior of mercury ion through Nafion-117 ion-exchange membrane. The mercury ions have been observed to rapidly permeate to Cl− side from Hg(NO3)2 solution, showing the extraordinary preference of mercury ions for Cl− ion in aqueous solution. On the other hand, from HgCl2 solution, slow permeation of mercury ions through the membrane has been observed. Also the transport of mercury ion from HgCl2 solution has been found to be higher than expected based on Donnan membrane equilibrium principle considering the ionic concentration of HgCl2 calculated using speciation diagram. This has been attributed to the leakage of neutral HgCl2 molecules through the membrane. The leakage of neutral HgCl2 species through Nafion-117 membrane has been confirmed in different cationic forms of the membrane. An attempt has been made to determine the concentration of cati...

Functionalized glass fiber membrane for extraction of iodine species

ABSTRACT Poly(vinylpyrrolidone) (PVP) has been anchored on the glass fiber membrane for capturing radioiodine in gaseous state and dissolved in water. First, precursor alkoxy silane monomer was anchored by sol-gel method on the glass fiber membrane and its polymerizing double bond was used subsequently for the anchoring of PVP by UV graft-polymerization. Thus formed PVP-membrane was characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy with EDS and thermo-gravimetric analysis. The sorption efficiency and loading capacity of the membrane toward I2, and stability of I2 complexed in the membrane were studied by UV-Vis spectrophotometry and 131I radiotracer method.

Phosphate functionalized radiation grafted Teflon for capturing and quantifications of U(VI) and Pu(IV) ions at ultra-trace concentration in aqueous samples

A phosphate groups bearing thin polymer film has been anchored on Teflon by radiation induced grafting and subsequent chemical modification. Thus formed phosphate-g-Teflon (Ph-g-T) sheet has been characterized appropriately and studied for its selectivity towards Pu(IV) and U(VI) ions at different acidities. Depending upon acidity dependent selectivity of Ph-g-T toward actinides ions, the solid state nuclear track detector based methods was developed to quantify Pu(IV) and U(VI) at ultra-trace concentration in a variety of aqueous samples.

Development of a technique for the calibration of HPGe detector to estimate radionuclides present in steel samples

The quantitative assay of radionuclides present in steel samples is required for the environmental safety as well as in the process control and quality control of the finished products. The standard sources should also be prepared in the required size and shape as that of the sample, for the efficiency calibration of the HPGe detector system. A method was developed and tested to use 152Eu point source for the determination of efficiency of an extended steel disk source using HPGe detector system. Standard point sources of 152Eu were prepared by transferring known amount of 152Eu activity by weight. Standard steel disk sources of required dimensions were also prepared by distributing uniformly the standard activity of 152Eu on both sides of the inactive steel disk. The extrapolated efficiency of the steel disk sample was determined using the efficiency of the 152Eu point source and it was compared with the efficiency determined using the standard sources of 152Eu prepared on the steel disks. The two efficiency calibration curves matched very well within the experimental limits. Using this efficiency calibration, a few steel samples were analyzed for the radionuclides present in them. The detections limits for most of the nuclides were much less than the specified limits. The method can further be extended for other types of geometries with suitable modifications for the changes in thickness and attenuation corrections.