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[en] Several surface finishing and coating techniques used in nuclear and industrial applications have been identified and their potential for reducing the hold-up of activity on exposed surfaces in α-active facilities, and easing their subsequent decontamination have been evaluated. The permanent treatment processes considered include electro-polishing, plating and anodizing; shot peening and nitriding; glazing, enamelling and ceramic coating; paints, lacquers and plastic linings. As temporary, replaceable surface protection, strippable coatings, adhesive backed films and chemically removable paints have also been included. An experimental programme is being initiated as the result of this survey to examine the effectiveness of these surface treatments in helping to reduce PuO2 contamination and maximise decontamination effectiveness. (author)
[en] We report on the experimental results of the ionization efficiency of Rb and Cs using a surface ionization source prototype at Rare Isotope Science Project (RISP) of Institute for Basic Science (IBS). A hot-cavity surface ionization source has been studied in an off-line test bench equipped with a mass separator and a beam diagnostic system which allow accurate ionization efficiency measurements. Ionization efficiencies of 76% and 77% have been measured for Rb and Cs, respectively, from the Ta prototype of the RISP surface ionization source.
[en] Full Text:Growth behavior of interfaces is usually described by a power-law of the growing interface width with time. This general scaling picture is an average behavior description, which may not be valid when only a finite number of interfaces is considered. In this work we study theoretically and experimentally the growth behavior of single interfaces and show that the particular growth function of the width always exhibits a non-monotonic, fluctuating behavior. This behavior results from competing mechanisms of normal growth and surface tension forces in the Quenched-noise Kardar-Parisi-Zhang (QKPZ) equation, and contains information on the growth process in this specific interface. We define a new measure of the interface width fluctuations in order to extract this information from experimental data. We analyze data of mercury droplets spreading on silver films, as well as data of water spreading on paper, in order to demonstrate the validity of our claim in a wide range of growing interfaces. The experimental results are compared to the numerical results of the QKPZ equation, for different cases of noise distributions
[en] This Part of this British Standard applies to the selection of surface materials which may become contaminated by radioactive substances and which will require subsequent decontamination. It gives guidance on good practice and takes the form of recommendations only. Each installation and particular usage has to be assessed individually and the suitability of the selected materials agreed between the designers and those responsible for safety and operation. (author)
[en] A pack chromizing technique has been successfully applied to mild steel which resulted in significant improvement in surface hardness which is useful in improving the wear resistance. Chromizing mixtures using Chromite ore, Ferrochrome and chromium powder with NH/sub 4/CI were used. The hardness of the surface of the specimens increased from 63.5 VPN to 246 VPN when chromized in the Chromite ore - NH/sub 4/CI mixture which is the maximum as compared to the specimens chromized in other two mixtures. (author)
[en] Nano-materials are materials with at least one nano-phase. A nano-phase is a phase with at least one of its dimensions below 100 nm. It is shown here that nano-phases have at least 1% of their atoms along their surface layer. The ratio of surface atoms is proportional to the specific surface area of the phase, defined as the ratio of its surface area to its volume. Each specific/molar property has its bulk value and its surface value for the given phase, being always different, as the energetic states of the atoms in the bulk and in the surface layer of a phase are different. The average specific/molar property of a nano-phase is modeled here as a linear combination of the bulk and surface values of the same property, scaled with the ratio of the surface atoms. That makes the performance of all nano-phases proportional to their specific surface area. As the characteristic size of the nano-phase is inversely proportional to its specific surface area, all specific/molar properties of nano-phases are inversely proportional to the characteristic size of the phase. This is applied to the size dependence of the molar Gibbs energy of the nano-phase, which appears to be in agreement with the thermodynamics of Gibbs. This agreement proves the general validity of the present model on the size dependence of the specific/molar properties of independent nano-phases. It is shown that the properties of nano-phases are different for independent nano-phases (surrounded only by their equilibrium vapor phase) and for nano-phases in multi-phase situations, such as a liquid nano-droplet in the sessile drop configuration.
[en] Normally, beta and alpha surface contamination monitors are used with a simple counting threshold, i.e. any pulse over a predetermined amplitude is counted. This is very different from gamma monitoring, where the use of counting windows is very popular and the use of full multi-channel analysis is common. Many current surface contamination ratemeters have the capacity to drive dual phosphor detectors and can be set up to provide beta and alpha channels. Effectively, the beta channel is a counting window, i.e. all pulses which are bigger than the threshold and smaller than the alpha threshold are counted. Larger pulses go into the alpha channel. This paper addresses how this can be used with beta only and alpha only detectors to provide information on the source. The detector is set up conventionally to a defined point for the lowest beta energy anticipated. The instrument is then switched to alpha + beta mode and the alpha threshold set to 3 times the beta threshold. With this set up, the alpha to beta channel count rate ratio varies smoothly by a factor of 14 between Y-90 (Emax 2.27 MeV) and C-14 (Emax 0.16 MeV). Hence the instrument can be used to estimate the energy of an unknown beta contaminant or to confirm that a mixed beta fingerprint has essentially the same mix. The same approach can be used with alpha probes to confirm the source quality. The main worry with alpha monitoring is the surface condition. A poor surface condition will lead to a low count rate. Using the channel ratio method will identify grubby sources. The resulting ratio can be used either as a go/no trigger, i.e. any surface with a low ratio will be treated as untrustworthy, or alternatively the ratio can be used to correct the reading to give a better estimate of surface activity. (authors)