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  • Author or Editor: R. Jérôme x
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Abstract  

The ability to electrochemically control the binding of uranium ions by redox active polypyrrole resins has been studied. The optimization of the conditions for the fixation of uranium has been defined while taking in account the nature of the fixed species, the nature of the resin and the nature of the solutions.

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Abstract  

We describe an original process for the treatment of low level activity radioactive liquid wastes. It deals with the electrochemical preparation of three polyacrylate polymers: polyacrylamide (PAam), polyacrylamidoglycolic acid (PAAG), polyacrylamidomethylpropanesulfonic acid (PAMPS) which are capable of complexing uranyl ions. We have demonstrated the complexation of uranyl by FT-IR and UV-Visible spectroscopy. All these complexes are soluble in water and we insolubilize in turn the complexes by crosslinking or by neutralization of positively charged complexes by the addition of polyanions to the medium. We have then done dynamic and static leaching tests on these insoluble complexes.

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Journal of Thermal Analysis and Calorimetry
Authors: Stéphanie Etienne, C. Becker, D. Ruch, B. Grignard, G. Cartigny, C. Detrembleur, C. Calberg, and R. Jerome

Abstract  

Silica nanoparticles of various sizes have been incorporated by melt compounding in a poly(methyl methacrylate) (PMMA) matrix to enhance its thermal and mechanical properties. In order to improve nanoparticles dispersion, PMMA grafted particles have been prepared by atom transfer radical polymerization (ATRP) from well-defined silica nanoparticles. This strategy was expected to ensure compatibility between both components of the PMMA nanocomposites. TEM analysis have been performed to evaluate the nanosilica dispersion whereas modified and non-modified silica/PMMA nanocomposites thermal stability and mechanical properties have been investigated by both thermogravimetric and dynamical mechanical analysis.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Ponomarenko, C. Klason, N. Kazantseva, M. Buzin, M. Alexandre, Ph. Dubois, I. Tchmutin, V. Shevchenko, and R. Jérôme

Abstract  

Thermogravimetry was used to investigate the effects of different inorganic functional fillers on the heat resistance of polymer matrices. The kinetic parameters of thermal oxidative degradation were shown to depend on the polymer, the chemical composition of the filler surface, the filler concentration, and the processing method, which determines the distribution of filler particles in the polymer matrix. Magnetic fillers (carbonyl iron, and hexaferrites of different structural types) were shown to be chemically active fillers, increasing the heat resistance of siliconorganic polymers. Their stabilizing effect is due to blocking of the end silanol groups and macroradicals by the surface of the filler and non-chain inhibition of thermal oxidative degradation. In the case of fiber-forming polymers (UHMWPE, PVOH and PAN), most magnetic fillers are chemically inert, but at concentrations of 30–50 vol% they increase the heat resistance of the composite. Addition of carbon black increased the heat resistance of the thermoplastic matrix. The dependence of the thermal degradation onset temperature on the kaolin concentration in the polyolefin matrix exhibited a maximum. Analysis of the experimental results demonstrated the operating temperature ranges for different composites, and their maximum operating temperature.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Inn, Zhichao Lin, Zhongyu Wu, C. McMahon, J. Filliben, P. Krey, M. Feiner, Chung-King Liu, R. Holloway, J. Harvey, I. Larsen, T. Beasley, C. Huh, S. Morton, D. McCurdy, P. Germain, J. Handl, M. Yamamoto, B. Warren, T. Bates, A. Holms, B. Harvey, D. Popplewell, M. Woods, S. Jerome, K. Odell, P. Young, and I. Croudace

Abstract  

In 1977, the Low-level Working Group of the International Committee on Radionuclide Metrology met in Boston, MA (USA) to define the characteristics of a new set of environmental radioactivity reference materials. These reference materials were to provide the radiochemist with the same analytical challenges faced when assaying environmental samples. It was decided that radionuclide bearing natural materials should be collected from sites where there had been sufficient time for natural processes to redistribute the various chemically different species of the radionuclides. Over the succeeding years, the National Institute of Standards and Technology (NIST), in cooperation with other highly experienced laboratories, certified and issued a number of these as low-level radioactivity Standard Reference Materials (SRMs) for fission and activation product and actinide concentrations. The experience of certifying these SRMs has given NIST the opportunity to compare radioanalytical methods and learn of their limitations. NIST convened an international workshop in 1994 to define the natural-matrix radionuclide SRM needs for ocean studies. The highest priorities proposed at the workshop were for sediment, shellfish, seaweed, fish flesh and water matrix SRMs certified for mBq per sample concentrations of 90 Sr, 137 Cs and 239 Pu + 240 Pu. The most recent low-level environmental radionuclide SRM issued by NIST, Ocean Sediment (SRM 4357) has certified and uncertified values for the following 22 radionuclides: 40 K, 90 Sr, 129 I, 137 Cs, 155 Eu, 210 Pb, 210 Po, 212 Pb, 214 Bi, 226 Ra, 228 Ra, 228 Th, 230 Th, 232 Th, 234 U, 235 U, 237 Np, 238 U, 238 Pu, 239 Pu + 240 Pu, and 241 Am. The uncertainties for a number of the certified radionuclides are non-symmetrical and relatively large because of the non-normal distribution of reported values. NIST is continuing its efforts to provide the ocean studies community with additional natural matrix radionuclide SRMs. The freeze-dried shellfish flesh matrix has been prepared and recently sent to participating laboratories for analysis and we anticipate receiving radioanalytical results in 2000. The research and development work at NIST produce well characterized SRMs that provide the world's environment-studies community with an important foundation component for radionuclide metrology.

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