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[en] 'The project on ceramic-supported polymer membranes focuses on the development of a novel class of membranes for the separation of organics from both organic-aqueous and organic-organic mixtures, Theses membranes are fabricated by a graft polymerization process where polymer chains are grown onto the surface of a ceramic support membrane. The surface graft polymerization process, developed at UCLA, results in the formation of a thin polymer layer covalently bonded to the membrane pore surface as a layer of terminally anchored polymeric chains. Through the selection of the polymer most appropriate for the desired separation task, the graft polymerized surface layer can be synthesized to impart specific separation properties to the membrane. It is expected that this project will lead to the demonstration of a new technology for the tailor design of a new class of selective and robust ceramic-supported polymer membranes. This new approach will allow the rapid deployment of task-specific membranes for the separation of waste constituents for subsequent recovery, treatment or disposal. Progress to date includes the preparation of successful silica-polyvinylpyrrolidone (PVP) membrane for the treatment of oil-in-water emulsions and a silica-polyvinylacetate (PVAc) pervaporation membrane for the separation of organics from water. Current work is ongoing to study the performance of the pervaporation membrane for the removal of chlorinated organics from water and to develop a pervaporation membrane for organic-organic separation. In another aspect of the study, the authors are studying the hydrophilic PVP CSP membrane for oil-in-water emulsion treatment with the goal of determining the optimal membrane polymer surface structure as a function of various operating conditions (e.g., tube-side Reynolds number and transmembrane pressure), Work is also in progress to characterize the polymer layer by AFM and internal reflection FTIR, and to model the conformation of the polymer surface layer.'
[en] 'This report summarizes the work progress over the last 1.75 years of a 3 year project. The objectives of the project have been to develop a new class of ceramic-supported polymeric membranes that could be tailored-designed for a wide-range of applications in remediation and pollution prevention. To date, a new class of chemically-modified ceramic membranes was developed for the treatment of oil-in-water emulsions and for the pervaporation removal of volatile organics from aqueous systems. These new ceramic-supported polymer (CSP) membranes are fabricated by modifying the pore surface of a ceramic membrane support by a graft polymerization process (Chaimberg and Cohen, 1994). The graft polymerization process consists of activating the membrane surface with alkoxy vinyl silanes onto which vinyl monomers are added via free-radical graft polymerization resulting in a thin surface layer of terminally anchored polymer chains. Reaction conditions are selected based on knowledge of the graft polymerization kinetics for the specific polymer/substrate system. The resultant ceramic-supported polymer (CSP) membrane is a composite structure in which mechanical strength is provided by the ceramic support and the selectivity is determined by the covalently bonded polymer brush layer. Thus, one of the unique attributes of the CSP membrane is that it can be used in environments where the polymer layer is swollen (or even completely miscible) in the mixture to be separated (Castro et al., 1993). It is important to note that the above modification process is carried out under mild conditions (e.g., temperature of about 70 C) and is well suited for large scale commercial application. In a series of studies, the applicability of a polyvinylpyrrolidone CSP membrane was demonstrated for the treatment of oil-in-water emulsion under a variety of flow conditions (Castro et al.,1996). Improved membrane performance was achieved due to minimization of surface adsorption of the oil components. For the special case of long surface chains, significant additional performance improvement permeate stream was attained at high Reynolds numbers. At the high Reynolds number condition, shear-induced deformation of the terminally anchored polymer chains and as a consequence the screening of the pore entry, resulted in improved permeate quality. Current studies are focused on the optimization of the polymer surface layer and quantification of chemical and hydrodynamic polymer-emulsion interactions.'
[en] The soluble boron content of the cooling water of a PWR is automatically controlled by vertical displacement of neutron absorbing control rods into the reactor core consisting of assemblies disposed vertically and side by side and a boron supply system and a dilution system for the water. The control rods comprise at least one control group. A system is associated with the reactor to determine the axial core power imbalance and the difference between this imbalance and a reference imbalance corresponding to minimum insertion of the control rods into the core and to xenon concentration equilibrium. The process involves predefining the respective operational ranges of the boron supply and dilution systems corresponding to the two values of two control parameters, i.e. a parameter characteristic of the position of the control group in the core and the power imbalance difference, taking into account the conditions of rector use and safety standards. The control parameters are determined continuously during reactor operation; the boron supply system or dilution system are stopped or actuated when the operation point goes over a limit of the operational range. The invention applies more particularly to reactors controlled in gray mode
[fr]La conduite du reacteur PWR est assuree par le deplacement dans la direction verticale de barres de commande absorbant les neutrons dans le coeur du reacteur constitue par des assemblages disposes verticalement et cote a cote et par le reglage de la teneur en bore soluble de l'eau sous pression grace a des moyens de borication et a des moyens de dilution de cette eau; les barres de commande comportent au moins un groupe de regulation et des moyens etant associes au reacteur pour la determination du desequilibre axial de puissance dans le coeur et de l'ecart de ce desequilibre axial par rapport a un desequilibre de reference correspondant a l'insertion minimum des barres de commande et a l'equilibre de la concentration en xenon dans ce coeur; ce procede le reglage agit de facon sure pour assister le groupe de regulation et permettre le maintien d'une distribution de puissance suffisamment homogene dans le coeur. On definit des domaines de fonctionnement des moyens de borication et des moyens de dilution respectivement, correspondant a des couples de valeurs de deux parametres de reglage, a savoir un parametre caracteristique de la position du groupe de regulation dans le coeur et l'ecart du desequilibre axial de puissance par rapport au desequilibre de reference, en tenant compte des conditions d'exploitation du reacteur et des normes de securite. De facon continue, pendant le fonctionnement du reacteur, on determine la valeur instantanee des parametres de reglage et on commande l'arret ou le declenchement des moyens de borication ou de dilution quand le point de fonctionnement franchit une limite du domaine de fonctionnement. L'invention s'applique en particulier a un reacteur pilote en mode G
[en] A brief historical approach is given to the way in which the concept of radiopharmaceuticals developed from the empirical use of radiotracers in man. Quality control of radiopharmaceuticals in different countries is briefly considered. Finally the changing form and origin of radiopharmaceuticals over the years is discussed. (UK)