Fuel Chemistry Division

India

Fuel Chemistry Division

India
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Vats B.G.,Fuel Chemistry Division | Phatak R.,Fuel Chemistry Division | Krishnan K.,Fuel Chemistry Division | Keskar M.,Fuel Chemistry Division | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

Compounds Sr7U(PO4)6 (1) and Ba7U(PO4)6 (2) were prepared by the solid state reaction route, by mixing appropriate molar proportions of alkaline earth metal carbonates (Sr and Ba), UO2 and NH4H2PO4 (ADHP) and heating in high purity Ar atmosphere at 1373 K for 10 h with intermittent grinding. Powder X-ray Diffraction (XRD) was done to ascertain the phase purity of the compounds. Structural characterization was carried out by Rietveld refinement method which shows the octahedral coordination for U4+ in both the compounds. Thermo-gravimetric (TG) measurement revealed that the compounds are stable up to 1000 K and, then, they oxidize in the air. High Temperature X-ray Diffraction (HT-XRD) study of both the compounds in vacuum showed positive thermal expansion over the temperature range from 298 to 1273 K. Heat capacity (Cp) of the compounds was also measured by heat flow Differential Scanning Calorimeter (DSC) under argon atmosphere from 303 to 858 K. © 2016 Elsevier B.V.


Sali S.K.,Fuel Chemistry Division | Kulkarni N.K.,Fuel Chemistry Division | Phatak R.,Fuel Chemistry Division | Agarwal R.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2016

Oxidation behaviour of (U0.3Pu0.7)C1.06 was investigated in air by heating samples up to 1073 K and 1273 K. Thermogravimetry (TG) of the samples and X-ray powder diffraction (XRD) of the intermediate products were used to understand the phenomenon taking place during this process. Theoretical calculations were carried out to understand the multiple phase changes taking place during oxidation of carbide. Theoretical results were validated by XRD analysis of the products obtained at different stages of oxidation. The final oxidized products were found to be a single FCC phase with O/M = 2.15 (M = U + Pu). Oxidation kinetic studies of (U0.3Pu0.7)O2 and (U0.47Pu0.53)O2 were carried out in dry air, using thermogravimetry, under non-isothermal conditions. The activation energy of oxidation was found to be 49 and 70 kJ/mol, respectively. Lattice parameter dependence on Pu/M and O/M of plutonium rich mixed oxide (MOX) was established using combined results of XRD and TG analysis of (U0.3Pu0.7)O2+x and (U0.47Pu0.53)O2+x. © 2016 Elsevier B.V.


Pai R.V.,Fuel Chemistry Division | Bamankar Y.R.,Fuel Chemistry Division | Yadav A.K.,Atomic and Molecular Physics Division | Bhattacharyya D.,Atomic and Molecular Physics Division | And 5 more authors.
RSC Advances | Year: 2016

(Th0.7-xU0.3Gdx)O2+y microspheres where x = 0, 0.05, 0.10 and 0.15 were prepared by internal gelation method. Good quality translucent microspheres of size ∼1.70 to 2.0 mm were obtained when low metal ([M]) and high [hexamethylenetetramine + urea]/[M] (R) concentration was used. The solid solutions prepared from these microspheres were subjected to thermal expansion studies which showed a gradual decrease in thermal expansion coefficient values with increase in Gd ion concentration. Specific heat capacities of mixed oxides were measured from 300 to 850 K and showed that the temperature dependence of the heat capacities of Gd doped samples is similar to that of the un-doped sample. The local structure studies by EXAFS showed that Gd-O, Gd-Th and longer Gd-O paths are similar to Th-O, Th-Th and longer Th-O path lengths. EXAFS studies showed higher oxygen coordination in the case of the 10% Gd substituted sample compared to the other samples. © 2016 The Royal Society of Chemistry.


Sarkar A.,Fuel Chemistry Division | Sarkar A.,Bhabha Atomic Research Center | Sasibhusan K.,Fuel Chemistry Division | Sasibhusan K.,Bhabha Atomic Research Center | And 4 more authors.
Lasers in Engineering | Year: 2013

Laser-induced breakdown spectroscopy (LIBS) methodology is reported in this work for the determination of boron (B) at thousands of parts per million and lithium (Li) at a few parts per million levels in simulated primary cooling water. The methodology will be useful for the rapid quantification in real life day-to-day analyses of samples from a pressurized- water reactor (PWR). Calibration curves were obtained by employing high purity solutions of the individual elements using three different calibration models. It was found that the B and Li give best results by different models applications. The usefulness of the model was determined on the basis of regression coefficient and root mean square error of prediction (RMSEP) values. The limit of detection (LOD) for the LIBS methodology for Li quantification were found to be 0.01 μg/g and 0.06 μg/g for Li(I) 670.790 nm and Li(I) 610.364 nm, respectively.


Chavan V.,Radiochemistry Division | Paul S.,Fuel Chemistry Division | Pandey A.K.,Radiochemistry Division | Kalsi P.C.,Radiochemistry Division | Goswami A.,Radiochemistry Division
Journal of Hazardous Materials | Year: 2013

Alpha spectrometry and solid state nuclear track detectors (SSNTDs) are used for monitoring ultra-trace amount of alpha emitting actinides in different aqueous streams. However, these techniques have limitations i.e. alpha spectrometry requires a preconcentration step and SSNTDs are not chemically selective. Therefore, a thin polymer inclusion membrane (PIM) supported on silanized glass was developed for preconcentraion and determination of ultra-trace concentration of actinides by α-spectrometry and SSNTDs. PIMs were formed by spin coating on hydrophobic glass slide or solvent casting to form thin and self-supported membranes, respectively. Sorption experiments indicated that uptakes of actinides in the PIM were highly dependent on acidity of solution i.e. Am(III) sorbed up to 0.1molL-1 HNO3, U(VI) up to 0.5molL-1 HNO3 and Pu(IV) from HNO3 concentration as high as 4molL-1 A scheme was developed for selective sorption of target actinide in the PIM by adjusting acidity and oxidation state of actinide. The actinides sorbed in PIMs were quantified by alpha spectrometry and SSNTDs. For SSNTDs, neutron induced fission-fragment tracks and α-particle tracks were registered in Garware polyester and CR-39 for quantifications of natural uranium and α-emitting actinides (241Am/239Pu/233U), respectively. Finally, the membranes were tested to quantify Pu in 4molL-1 HNO3 solutions and synthetic urine samples. © 2013 Elsevier B.V.


Tiwari I.,Banaras Hindu University | Gupta M.,Banaras Hindu University | Sinha P.,Banaras Hindu University | Aggarwal S.K.,Fuel Chemistry Division
Electrochimica Acta | Year: 2012

A modified glassy carbon electrode has been constructed using a 4′-(4-carboxyphenyl)-2, 2′: 6′, 2′′- terpyridine(1, 10-phenanthroline)chloride ruthenium (II) tetrafluoroborate complex along with multiwalled carbon nanotubes and nafion. The synthesized composite has been characterized using scanning electron microscopy, Transmission electron microscopy, and UV-Visible spectroscopy and IR spectroscopy. Electrochemical behaviour and stability of modified electrode has been investigated by cyclic voltammetry. Electrocatalytic activity of the modified electrode was investigated for the oxidation of phenyl hydrazine in 0.1 M phosphate buffer solution of pH 7.4. We observed Ruthenium complex/MWCNTs/ionomer composite has better electrochemistry, electrical properties and firm adhesion of the material with homogeneous dispersion at the electrode surface. The modified electrode showed electro-catalytic response to the oxidation of phenyl hydrazine at the potential of 600 mV. The linear range and detection limit for the detection of phenyl hydrazine in the optimum condition was found to be 5 × 10 -6 to 0.2 × 10 -3 M and 0.15 μM respectively. The modified electrode also exhibited several attractive features such as simple preparation, fast response, good stability and repeatability. © 2012 Elsevier Ltd. All rights reserved.


Tiwari I.,Banaras Hindu University | Singh M.,Banaras Hindu University | Gupta M.,Banaras Hindu University | Aggarwal S.K.,Fuel Chemistry Division
Materials Research Bulletin | Year: 2012

We herein report a simple, low cost and green preparation of nanowires of (anthraquinone-2-carboxylic acid/amino functionalized) multiwalled carbon nanotubes (HOOC-2-AQ/AMWCNTs) which has been further employed for the development of highly sensitive oxygen sensor. The prepared composite has been characterized by TEM and electrochemical studies. The glassy carbon electrode modified with composite shows an irreversible and good electrocatalytic activity for the reduction of oxygen. The reduction potential of the oxygen was shifted 460 mV towards the positive potential with this modified electrode as compared to bare glassy carbon electrode. The prepared material was stable with no leaching observed of the mediator. A linear response range of 0.2-6.8 mg L -1, with a sensitivity of 5.0 μA L mg -1 and a detection limit of 0.02 mg L -1 were obtained with this sensor. © 2012 Elsevier Ltd. All rights reserved.

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