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[en] The general terms are defined which come under the categorical description 'corrosion'. With metals, corrosion is generally a measurable change of a mostly electrochemical nature which can lead to damage. (TK/LH)
[de]Es werden die allgemeinen Begriffe definiert, die unter die Sammelbezeichnung 'Korrosion' fallen. Allgemein ist Korrosion bei Metallen eine messbare Veraenderung meist elektrochemischer Natur, die zu einem Schaden fuehren kann. (TK)
[en] About 80 per cent of all plant outages involving steam generators can be traced back to corrosion problems. Such problems arise from the continuous ingress of non-volatile contaminants, ie corrosion products and salt impurities. These have their origin in the balance of plant systems, and the corrosion products generally accumulate in the steam generators - forming both deposits in the flow restricted areas (such as on the tube sheet and tube support plate), and scales on the steam generator heating tubes. For many years, the industry has been involved in developing various types of cleaning techniques. Among these, chemical cleaning especially has been found to be very effective for removing corrosion products. The KWU chemical cleaning process described here consists of two different single-step methods for sludge removal: a high temperature iron process; and a copper process with ambient application temperature. The iron and copper process can be applied either in combination or separately, and uses separate solvents. (author)
[en] Package 9975-04985 was examined following the identification of several unexpected conditions during surveillance activities. A heavy layer of corrosion product on the shield and the shield outer diameter being larger that allowed by drawing tolerances contributed to a very tight fit between the upper fiberboard assembly and shield. The average corrosion rate for the shield is estimated to be 0.0018 inch/year or less, which falls within the bounding rate of 0.002 inch/year that has been previously recommended for these packages. Several apparent foreign objects were noted within the package. One object observed on the air shield was identified as tape. The other objects were comprised of mostly fine fibers from the cane fiberboard. It is postulated that the upper and lower fiberboard assemblies were able to rub against each other due to the upper fiberboard assembly being held tight to the shield, and a few stray cane chips became frayed under vibratory motions.
[en] Detailed description of the characteristics of bulk and surface properties of synthetic magnetites employed in simulation studies is given. Different synthetic routes are discussed, and the products obtained are assessed. The relevance of composition and of particle size and shape for meaningful extrapolation to plant situation is discussed. (author)
[en] The introduction of super-plasticizers in cement matrices can improve the properties of cement. A new generation of polymers belonging to the family of the aliphatic saturated polymers is being used and the use in cement subjected to irradiation raises the question of its radiation sensitivity. In order to understand the long term behaviour and the radionuclides retention of cemented-waste package and cement barriers, the entire source terms able to influence the integrity of the cement and/or the radionuclides migration have to be taken into account. In this context, the degradation of organic materials belonging to the formulation of the cement itself or coming from the wastes have to be studied. For this purpose, a general approach to study the radiolysis of these organic constituents has to be implemented. The method consists, first in leading irradiation experiments on a large panel of organic polymers or molecules (additives...) under different irradiation conditions, secondly in quantifying the gas released from the irradiated material and thirdly in defining the conditions and the methodology of the leaching procedure. For the last point, the approach consists in identifying the criteria to take into account in order to follow the kinetic of the soluble degradation products release and to develop an analytical strategy based on separation techniques to determine as completely as possible the composition in small organic compounds (such as carboxylic acids) coming from the different categories of polymers, in order to evaluate their complexation ability. To illustrate this methodology, results on pure (ethylene-co-vinyl acetate) copolymer EVA are given. (authors)
[en] In the present study, the corrosion characteristics of cast Mg98Gd1.5Ni0.5 alloy with Ni-containing long-period stacking ordered (LPSO) structures were investigated. The results reveal that the Ni-containing LPSO phases were more active than the Mg matrix and preferentially eroded during the immersion process. This behavior indicates that the Ni-containing LPSO phases could have acted as microanodes, in contrast to the cathodic role of the Ni-free LPSO phases in other Mg alloys. Furthermore, the potential difference of approximately 600 mV between the phases accelerated the dissolution rate of the LPSO phase. Corrosion of the Mg matrix also occurred due to the inhomogeneous microstructure of the matrix. The synergetic corrosion between the Ni-containing LPSO phases and the enrichment of Cl− in the thick corrosion product films dominated the propagation of corrosion, which substantially deteriorated the corrosion resistance and accelerated the corrosion process of the Mg98Gd1.5Ni0.5 alloy.