Results 1 - 10 of 11452
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[en] This review contains more than 100 observations and 224 references on the dissolution phenomenon. The dissolution processes are grouped into three categories: methods of aqueous attack, fusion methods, and miscellaneous observations on phenomena related to dissolution problems
[en] This study is concerned with direct cristallization of ammonium uranyl carbonate (AUC) from a uranium loaded organic phase (30% TBP in kerosene), with ammonium carbonate (NH4)2 CO3. The effects of operating conditions (NH4)2 CO3 concentration, flowration residence time, temperature on the physical properties of AUC crystals (particle size distribution, specific area, density..) are reported. All products were identified (both by chemical analysis, X-Ray diffraction) as being ammonium uranyl ratio and (NH4)2 CO3 concentration favor the formation of fine AUC grains and aggregates. This is due mainly to the high concentration of (NH4)+ in the system which leads to a high solution supersaturation and consequently to a rapid formation rate of crystal (germination). The reverse phenomenon is observed at low phase ratio and (NH4)2 CO3 concentration, where germination and crystal growth ara slow and the product is mainly monocrystal. In the intermediate range, a mixture of polycrystal and aggregates is obtained. Residence time and temperature are also shown to have an effect on the processes (the effect of time being more important than temperature)
[en] Highlights: • The dissolution model of nanoparticles was established. • The size-dependent dissolution thermodynamics were derived. • The influence regularities of nano-Cu dissolved in dilute acid were discussed. • The dissolution behavior of nanoparticles could be explained by the dissolution model. • It provided guidance for the preparations and applications of the nanomaterials.
[en] Conclusion: Thanks to its interdiciplinary nature ASGARD has created a common platform for many aspects of novel nuclear fuel cycles, 25% into the project everything is running according to plan with significant advances in most domains. The training and education scheme used in ASGARD has already been successfully implemented allowing young scientists in the field to present their results internationally and also visit other ASGARD labs. The future collaboration with e.g. SACESS and CINCH II will enable the creation of significant added value to the communities involved. More will come. We have only begun.....
[en] A review of chemical decontamination methods for coatings indicates the following: the ease of both contamination and decontamination is a function of the radionuclide and the pH of the environment; the coating type is important in determining whether the contamination is loosely adsorbed, complexed, or contained in porous filler material; the condition of the coating is important to the decontamination factor obtained. Thus coatings can be decontaminated provided the solvent is sufficiently acid to solubilize the radionuclide and the complexant strength of the solvent is greater than that of the coating. Difficulties arise if the contamination is associated with fillers. Furthermore, though nothing has been said about temperature, decontamination of metal goes faster and, usually, with better efficiency at high temperatures. 11 references, 3 figures
[en] In the Scotia and Weddell Seas the concentration of dissolved Al was 1-1.5 nM in ice-free surface waters, up to 3 nM in ice-covered waters and about 2.6 nM in bottom waters. The solubility and the dissolution rate of diatomaceous silica, obtained from net samples and from incubations in the presence or absence of dissolved Al, were inversely related to solid-phase Al/Si ratios. At in situ temperatures, dissolution rates from Antarctic diatoms are higher than those for diatoms from temperature regions. Effects on distribution patterns of silicic acid in the Weddell Sea are discussed. (author). 32 refs.; 3 figs.; 2 tabs