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Abstract  

The use of an electrochemical process for U/Pu partitioning has demonstrated a good performance and is a safe alternative for nuclear facilities. Its great advantages are the lack of introduction of foreign ions into the process and, especially, the minimization of the waste volume generated. For the introduction of electrochemical U/Pu partitioning in the 2nd Pu purification cycle, preliminary studies were carried out with a single mixer-settler unit. Based on the results, an 8-stage electrolytic mixer-settler (M-S MIRELE) was designed. Titanium was MIRELE's housing material (cathode) and platinum the anode, insulated with PTFE. The Pu recovery was higher than 99%, indicating the efficiency of this equipment.

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Abstract  

Additional1 bifunctional anion-exchange resins have been designed, synthesized and evaluated for their ability to take up Pu(IV) from nitric acid solutions. Bifunctionality is achieved by adding a second anion-exchange site to the pyridine nitrogen (also an anion-exchange site) of the base poly(4-vinylpyridine) resin. Previous work focused on the effect of varying the chemical properties of the added site along with the length of an alkylene ‘spacer’ between the two sites. Here we examine four new 3- and 4-picolyl derivatives which maintain more rigidly defined geometries between the two nitrogen cationic sites. These materials, which have the two anion-exchange sites separated by three and four carbons, respectively, exhibit lower overall Pu(IV) distribution coefficients than the corresponding N-alkylenepyridium derivatieves with more flexible spacers. Methylation of the second pyridium site results in a ca. 20% increase in the Pu(IV) distribution coefficients.

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Abstract  

Nuclear chemistry is usually associated with great disasters, especially the atomic bomb; this without reflecting that knowledge of nuclear chemistry has also had many benefits in the field of medicine and health. Whereas in technologically advanced countries, nuclear chemistry is considered to be an important part of the syllabus, including topics such as radioactivity with the emphasis in making conscience in the common citizen of the inherent benefits.

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The choice of an appropriate and safe disposal alternative should be based on the wide range of physicochemical examination thermal analysis in conjunction with other data enables identification of wastes, allows determination of weight losses at any stage of thermal decomposition and characterization of the combustible properties of wastes.

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Abstract  

Selenite was boiled in KCl solutions of different concentrations at the respective boiling temperatures and atmospheric pressure. The products were subjected to X-ray diffraction analysis, qualitative infrared analysis, differential thermal analysis and microscopic examination. The product obtained in 1.0 M KCl solution was the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O). In more concentrated KCl solution (1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 M), the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O) was formed, and a reaction took place between KCl and CaSO4, which gave a double salt: potassium pentacalcium sulphate monohydrate (K2SO4·5CaSO4·H2O).

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Abstract  

The crystallization behaviour of amorphous melt spun Fe82−x−yCr18ZrxBy (x=0–8, y=10–20) ribbons have been investigated using differential scanning calorimetry. The crystallization temperature and crystallization behaviour change with varzing Zr and B content. The microstructural development during annealing of amorphous Fe64Cr18Zr8B10 has been investigated by a combination of transmission electron microscopy and energy dispersive X-ray microanalysis. Isothermal annealing for 2 h at temperatures in the range 600–1000°C produces a variety of different microstructures depending on the annealing temperature. At 600°C, the amorphous alloy partially crystallizes to a form a microstructure consisting of 9 nm sized bee ferrite grains embedded in an amorphous matrix. At temperatures in the range 700–900°C, the alloy microstructure transforms into a mixture of bee ferrite, faulted fcc MB12 boride particles and tetragonal M3B boride particles. At 1000°C, the faulted fcc MB12 boride particles are replaced by orthorhombic M4B boride particles.

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Abstract  

Both oxidation and methoxymethylation of the surfaces of a series of MDI (methylene diphenyl isocyanate) and TDI (toluene diisocyanate) polyether and polyester soft segment 1–4 butanediol polyurethanes result in increased thermal stability as measured by TG. Explosive loss of mass above the hard segment melting temperature suggests that the diffusion of the dissociated diisocyanate moiety is hindered at lower temperatures. Thus suppression of the depolycondensation reaction by chemical blockage of the surface may result in a material with an increased service life at use temperatures as thermal stability of a polyurethane may depend upon the low diffusivity of its diisocyanate comonomer. The effect of vacuum, oxygen and water vapor on the kinetics of mass-loss of several of the polyurethanes is presented.

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