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  • Author or Editor: A. Das x
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Abstract  

Adsorption of uranium, as UO2 2+, and thorium, as Th4+, has been studied using a modified fly ash bed. Effects of pH and various ions like La3+, Fe3+, Ce4+, SiO3 2- etc., have been examined. Synthetic mixtures of UO2 2+ 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.

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Abstract  

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.

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Abstract  

Instrumental NAA based on short-lived radionuclides implies high initial total count rates which change appreciably over the counting period. This in turn necessitates corrections for three negative biases: losses due to differences in counting time between samples and standards; pile-up losses, and (residual) influence of dead-time. The procedure is demonstrated for the determination of Al, Ca, V and Mn in the IAEA Reference Material 395 Urban Dust. The obtained data are in good agreement with the reference values for this material. By limiting the total relative dead-time to 25%, statistical uncertainties are below 5%.

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Abstract  

A group of 27 tobacco samples was submitted to INAA. Bowen's Kale was analyzed with the samples. The resulting data for 21 elements in tobacco were processed by a cluster programme. This combination proves to be a convenient tool for discrimination within one group of samples.

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Summary  

Measurement of 222Rn emanation from building components is now mandatory by European law. This implies formulation in terms of basic parameters and design of a routine control procedure. Both are presented here.

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Abstract  

Radiation initiated polymerisation of N,N-dimethyl acrylamide was investigated in an aqueous medium. The polymerisation followed first order kinetics at all the concentration of monomers used. The rate constant is 0.024 h–1 at a dose rate of 270 rad/min, for 0.025 mol·dm–3.

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Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur ∼ at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol−1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments.

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Abstract  

Accuracy and precision of instrumental neutron activation analysis, based on short-lived radionuclides, are considered. Equations are derived for both quantitives as a function of concentration and features of the γ-ray spectrum. The determination of vanadium by way of52V(T=3.75 min) is used as an example.

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Abstract  

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.

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Abstract  

The applicability of a 400 kV neutron generator in the elemental analysis of dry biological material is considered. Data for the specific count-rates of 66 elements are given. A procedure for the determination of N, Mg, Si, P, K and Ca is described. The results for three Standard Reference Materials and some samples are given.

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