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Abstract  

The thermal behavior of chitosan (CS)/natural rubber latex (NRL) blends has been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). Decomposition behavior of CS changes with the addition of NRL. The effect of blend composition on the amount of residue remaining at various temperatures has been studied. Activation energies of degradation have been calculated using Horowitz-Metzger equation. From the activation energy values, it is found that among the series of the blend compositions, CS15NRL85 exhibits better thermal stability. DSC studies reveals that the CS/NRL blends are thermodynamically incompatible. This is evident from the presence of two glass transitions, corresponding to CS and NRL phases in the blend.

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Abstract  

The possibility of use of combined gamma spectrometry and X-ray fluorescence for uranium isotopic analysis in dilute aqueous solutions has been studied. Uranium K X-rays were excited by gamma-rays of57Co radionuclide source and were measured together with 185.7 keV gamma-rays of235U using a planar pure Ge detector. Uranium Kα1 fluorescent X-rays were used for the evaluation. The method was proved to be independent of total uranium concentration in the region of 8–20 mg U/ml. The procedure making use of measurement of 7 ml samples and allowing to achieve an accuracy better then 1% in the region of 0.4–4.5 at. % of235U is proposed.

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Abstract  

Iodine-129 may have no radiation hazard but it is a useful marker. Animal thyroids concentrate the isotope to 4 orders of magnitude greater than the intake. This results in a potential biological and physical indicator of radioiodine contamination. Since 1943, 129I/127I ratio in animal thyroids from the Northern Hemisphere has increased 2 to 5 orders of magnitude. Since 1985, thyroids of deer living near a nuclear reprocessing facility have contained 129I, which are 3 to 7 orders of magnitude greater than pre-nuclear levels. Limited measurements of 129I in thyroids from the Southern Hemisphere have shown little increase. An appendix is presented to show that 129I, may be helpful to evaluate past radiation hazard from fission products.

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Abstract  

A multistage process combining photocatalytic degradation of organic complexes and complexants followed by separation of the radionuclides by ion exchange was developed and tested for the treatment of aqueous waste from chemical or electrochemical decontamination of NPP primary circuit internals. In these solutions, both the oxalic and citric acids could be quantitatively degraded within 10-12 hours of irradiation by 254 nm UV radiation in the presence of TiO2 photocatalyst. For the group radionuclides separation, a standard cation exchanger was found to be preferable to any of the set of the tested inorganic-organic composite absorbers.

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Abstract  

The determination of uranium in solutions and sorbents by measurement of absorption of soft gamma-rays is described. The use of 22 keV gamma-rays of109Cd enbled us to improve the sensitivity of the determination for nearly an order of magnitude when compared to the measurements using241Am source. The application to the continuous measurement of uranium concentration in pilot-plant streams and of concentration profiles of uranium sorbed on columns of ion exchangers is described.

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Abstract  

appeared in the Journal of Radioanalytical and Nuclear Chemistry, Vol. 243, No. 2 (2000) 467–472.During the electronic submission of the paper the file was damaged, and parts were left out. In order to correct this, we publish the correct paper as a whole.Iodine-129 may be no radiation hazard but it is a useful marker. Animal thyroids concentrate the isotope to 4 orders of magnitude greater than the intake. This results in a potential biological and physical indicator of radioactive contamination. Since 1943, 129I/127I ratio in animal thyroids from the Northern Hemisphere has increased 2 to 5 orders of magnitude. Since 1985, thyroids of deer, living near a nuclear reprocessing facility have contained 129I which is 3 to 7 orders of magnitude greater than pre-nuclear levels. Limited measurements of 129I in thyroids from the Southern Hemisphere have shown little increase. An appendix is presented to show that 129I may be helpful to evaluate past radiation hazard from fission products.

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Abstract  

A neutron activation analysis procedure has been developed for the indirect determination of phosphorus as orthophosphate at ppb levels, via the formation of antimonyl phosphomolybdic acid. The complex is adsorbed on Sephadex G-25 resin and the antimony is estimated through NAA, allowing the determination of phosphorus. The procedure provides an easy method to adopt for the routine determination of phosphorus at 10 ng ml–1 levels with good precision, in water samples.

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Composite absorbers of inorganic ion-exchangers and polyacrylonitrile binding matrix

V. Influence of ionising radiation on the leachability of137Cs from cemented composite NiFC-PAN absorber

Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Motl, J. John, and F. Sebesta

Abstract  

Maximum attainable self-absorption dose for cemented composite ion-exchanger, consisting of nickel hexacyanoferrate and polyacrylonitrile binding matrix, loaded with137Cs up to repository acceptable level (1.1·1012 Bq·m–3) was calculated to be 105 Gy. The cemented absorber with sorbed caesium was irradiated by60Co source up to 1 MGy, and leach tests were performed to determine possible influence of self-irradiation on the caesium leachability. No radiation induced changes in caesium immobilisation in solidified ion-exchanger were observed.

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Existing data suggest that the self-enhancement and self-protection motivations (which elevate or protect the positive self-concept) exert a pivotal influence on self-evaluation and behavior. Moreover, these motivations are more potent than the self-assessment motivation (which works to increase the accuracy of the self-concept) or the self-verification motivation (which works to confirm the self-concept). The data also suggest that the self-enhancement and self-protection motivations serve crucial mental health functions and that these functions are apparent across different cultures. This article relates these findings to the possible evolutionary utility of these motivations. It is argued that self-enhancement and self-protection motivations were evolutionarily selected, because they offered personal, relational, and group-rank advantages to species members who possessed these traits.

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Composite absorbers consisting of inorganic ion-exchangers and polyacrylonitrile binding matrix

III. Options for treatment of spent composite absorbers for final disposal

Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Šebesta, J. John, A. Motl, V. Peka, and E. Vacková

Abstract  

Both cementation and vitrification was shown by preliminary experiments to be applicable for treatment of the spent composite absorbers with polyacrylonitrile binding matrix for final disposal. Loadings of cement mix with composite absorbers up to 5–9% (w/w) were achieved Admixtures of natural clinoptilolite were found to improve compressive strength of the samples. The presence of PAN binding polymer was found not to disqualify the composite absorber tested from final treatment by vitrification.

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