, rate constants have been evaluated for the overall radiolytic decomposition of alkali metal nitrates. This kinetic scheme is applicable in the low dose range. At higher doses, however, the radiation induced reaction, NO
may also contribute. The overall rate constants are 0.13×10–6 (LiNO3), 1.05×10–6 (NaNO3), 10.10×10–6 (KNO3), 9.50×10–6 (RbNO3) and 25.50×10–6 (CsNO3) kGy–1.
Gamma-ray induced decomposition of some divalent nitrates, viz. Mg(NO3)2·6H2O, Ca(NO3)2·4H2O, Sr(NO3)2, Ba(NO3)2, Zn(NO3)2·6H2O, Cd(NO3)2·4H2O, Hg(NO3)2·2H2O, Mn(NO3)2·4H2O, Cu(NO3)2·3H2O and trivalent nitrates, viz. Al(NO3)3·9H2O, Fe(NO3)3·9H2O, Cr(NO3)3·9H2O, Y(NO3)3·6H2O, In(NO3)3·3H2O, La(NO3)3·6H2O, Ce(NO3)3·6H2O, Pr(NO3)3·6H2O, Bi(NO3)3·5H2O has been studied in solid state at room temperature. G(NO
) values (after applying appropriate dose correction) have been found to vary in the range 0.12–3.16 and 0.069–2.15 for divalent and trivalent nitrates respectively. G'-values were calculated by dividing G by the ratio of number of electrons in nitrate ion to the total number of electrons in the nitrate salt. Cation size, its polarizing power, available free space in the crystal lattice and the number and location of water molecules seem to play a dominant role in radiolytic decomposition. For Zn, Sr, In, La and Ce nitrates dose variation studies have been carried out.
A derivatograph was used to follow the modification of the skeleton structure and thermal stability of zeolites in sodium and ammonium forms. Analogous investigations were carried out by independent methods such as IR and X-ray. Comparison showed good agreement between the results. The controlled dealumination of the Y-type zeolite enhanced the thermal stability
DHOA (Di-n-hexyl-octanamide) is one of the alternative extractants to TBP (tri-n-butyl phosphate) known for the extraction
of uranium from moderate nitric acid medium without significant extraction of the fission products. Analytical application
of DHOA was explored to develop a methodology for determination of trace metallic constituents in uranium based nuclear materials.
This involved the separation of uranium matrix by 1.1 M DHOA-dodecane followed by the analysis of the raffinate for trace
constituents by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). A systematic study showed that four contacts
of 1.1 M DHOA-dodecane were required for quantitative extraction of U from 4 M HNO3 feed for the sample size of 1 g in 10 mL. The feasibility of using DHOA for extraction of U from trace metallic constituents
in U based fuel materials without losing trace quantities of analytes of interest was studied by using synthetic samples after
appropriate spiking of common impurities and critical elements at their required specification limits (common elements—5 ppm,
critical elements—1 ppm). A systematic study was carried out to compare the analytical performance of DHOA with TBP, which
revealed that DHOA could successfully be employed for the determination of 19 trace constituents with lower estimation limits
of 5 ppm for common impurities and 1 ppm for critical elements.
A series of rare earth zeolites of types X and Y were prepared by cation exchange. Thermal analysis curves (TG/DTA) were employed to estimate the structural changes in the zeolite framework. Analogous investigations were carried out by independent methods such as XRD and IR spectroscopy. The results indicate increased thermal stability on the replacement of sodium by rare earth. Partial replacement of rare earth by ammonium/hydrogen enhances the thermal stability. The type Y zeolites are more stable than those of X type.
Authors:G. N. Natu, S. B. Kulkarni, and P. S. Dhar
A systematic TG/DTG/DTA analysis is reported of anhydrous and heptahydrate forms of tris-phenanthroline and tris-pyridyl complexes of nickel(II), whose kinetic parameters were calculated by five different methods. The dehydration and de-ligation steps are descrete in Ni(phen)3Cl2 · 7 H2O, while those in Ni(bipy)3Cl2 · 7 H2O are mixed. Partial loss of the ligand is common for both hydrated and anhydrous compounds. In most cases the activation energyEa calculated from the mechanism-non-invoking equation of Horowitz and Metzger is in good agreement with that found from the mechanism-based relation of Mampel. There is an appreciable variation in magnitude in the results obtained from the different relations for the evaluation ofEa. It is inferred that such kinetic data are of significance in comparisons of the decomposition processes in related systems but not as absolute quantities.
Authors:L. Sawant, P. Kalsi, A. Kulkarni, and S. Vaidyanathan
A differential pulse voltammetric method has been successfully used for the determination of uranium in low concentration streams of a uranium plant. The method gives a precision of about 13% to 7% in the range of 300 ppb to 15 ppm. The accuracy of the results was ascertained by comparing the values with those obtained by a spectrophotometric method. The method is simple, fast, sensitive, fairly accurate and does not require a preconcentration step.
Authors:S. Sampath, N. K. Kulkarni, and N. C. Jayadevan
Thermal decomposition of metal uranyl acetates is one of the best ways of preparation of uranates in crystalline form at low temperatures. Acetates of the type M(UO2)2(OAc)6·7H2O (M=Zn(II), Mg(II) and Ni(II) were prepared and characterised. Their X-ray powder diffraction analysis showed that they all belong to the orthorhombic crystal class.
Authors:S. Kulkarni, R. Acharya, N. Rajurkar, and A. Reddy
Studies on bioaccessibility of elements were carried out by in-vitro gastrointestinal digestion simulation method combined
with neutron activation analysis (NAA) using NH4HCO3 as an alternate base to commonly used base of NaHCO3. The effect of two bases namely NaHCO3 and NH4HCO3 on the bioaccessibility of the elements namely Br, Fe, K, La, Na, Rb, Sm and Zn from wheat seeds, fresh wheatgrass and commercial
wheatgrass tablet was investigated. The bioaccessible concentrations of the elements were determined by neutron activation
analysis (NAA). The bioaccessible concentrations of samples digested using NH4HCO3 were found to be higher by 10–15% for most of the elements than that observed using NaHCO3. In the case of fresh wheatgrass, the differences were as high as 50%. The present study indicated that NH4HCO3 can be used as a base instead of NaHCO3 in in-vitro gastrointestinal digestion simulation method.