Authors:Julen Ibarretxe, Gabriël Groeninckx, and Vincent B. F. Mathot
difference in crystallinity ( dashed line ), final result after correction ( dashed-dotted line ), and zero level indicator ( dotted line )
Figure 9 presents the results of the same treatment applied to
Authors:T. Oi, Y. Kikawada, T. Honda, T. Ossaka, and H. Kakihana
Determination of the lanthanoids, thorium and uranium in silicate rocks has been investigated by neutron activation analysis (NAA). Seven or eight lanthanoids and thorium and uranium were determined by non-destructive instrumental NAA. The numbers of the lanthanoids determined were increased and errors on the final values were reduced by pre-irradiation treatments, which included a coprecipitation process with aluminium as collector to remove the alkali metals and halogens and a solvent extraction process to eliminate iron. The necessity of scandium removal was indicated.
A locally produced mordenite type synthetic zeolite and its modified form obtained by the treatment with dilute hydrochloric
acid were tested for their cesium uptake characteristics. The two zeolites were compared with other commercially available
synthetic zeolites with respect to their ability to sorb radiocesium from dilute nitric acid solution. The effects of the
changes in the composition of the solution including the concentration of nitric acid, sodium and cesium on the uptake of
cesium were investigated. The results can be used in the removing processor radiocesium from different types of nuclear plant
effluents by these zeolites.
Authors:M. Vasilchenko, T. Shakhtshneider, D. Naumov, and V. Boldyrev
Topochemistry of the initial stages of evaporation and dissolution of monoclinic single crystals of paracetamol and phenacetin was studied. Thermal treatment of these crystals showed that the morphology of etch pits depicts the symmetry of etched planes. The shapes of pits formed during chemical etching of the cleavage plane of a paracetamol crystal by different etchants were not similar to each other. The chemical etching of the cleavage plane of a phenacetin crystal resulted in the formation of pits stretched along the same direction, independently of the chosen solvent. An interpretation of this result is suggested, based on the analysis of the anisotropy of the crystal structure and presence of steric hindrance.
Authors:A. P. Ribeiro, A. M. G. Figueiredo, and J. B. Sígolo
Instrumental neutron activation analysis (INAA) was used to determine metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), semi-metals (As, Sb), actinides (U, Th) and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in bottom sediments from one of the ponds of the Sewage Treatment Plant (STP) in São Paulo, Brazil. The results obtained were compared with the concentration determined in a soil profile and in a rock sample, in natura, representing the lithologies of the region, and indicated that only As, Cr and Zn can have their origin associated with the residues disposed around the pond.
Authors:M. Inoue, H. Kofuji, M. Yamamoto, H. Sasagawa, and K. Komura
In the usual measurements of radionuclides in the environmental samples by g-ray spectrometry, Compton scattering of 1461 keV g-rays from 40K severely interferes with the detection of artificial radionuclides in marine and agricultural products. In order to eliminate the interference of 40K, we have developed a simple and convenient water leaching treatment method applicable to seaweed (sargasso) samples. By this treatment, over 98% of the potassium in seaweed samples is removed without notable losses of artificial and/or natural radionuclides. In combination with the low-level g-ray counting in the Ogoya underground laboratory, the detection limit could be improved by ~1 order of magnitude.
Authors:R. C. Eerlingen, H. Jacobs, H. Van Win, and J. A. Delcour
Gelatinisation temperatures as a function of moisture content were determined for potato starch. The native starch was then hydrothermally treated at a temperature 3% (Kelvin degrees) below the gelatinisation peak temperature and at moisture levels varying from 20 to 67% (by weight). Gelatinisation temperatures, temperature ranges and enthalpy values were affected for all treated samples. However, two sample populations could be distinguished: those samples treated under ‘limited’ moisture conditions and other samples treated in the presence of ‘extragranular’ moisture. A two-step hydrothermal treatment further increased the gelatinisation temperature, but the effect of the second step was small in comparison to that of the first.
Some physico-chemical properties and reactivity in their reduction with hydrogen of NiO—Y2O3 mixed oxides prepared in a dry way have been studied using isothermal thermogravimetry in the range of 320–410°C and temperature-programmed reduction. It was found that addition of small amounts of chloride and acetate anions retarded the reduction of nickel oxide and accelerated the reduction of mixed oxides. The presence of oxalate and formate ions manifests itself by a small positive effect. Introduction of platinum activator or heat treatment of the samples in various atmospheres led to a pronounced increase in the reduction rate. The efficiency of the spill-over effect increases with increasing proportion of non-reducible Y2O3. The pre-irradiation of the samples by accelerated electrons and gamma rays at a dose of 1 MGy results in a negative kinetic effect only with the samples containing an excess of nickel oxide.