Browsing by Author "Stuart, WI"

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    Composition and structure of ammonium uranates
    (Australian Atomic Energy Commission, 1968-10) Stuart, WI; Whateley, TL
    The ammonium uranate system was studied by thermal analysis, ion-exchange measurements and infra-red spectroscopy. The results show that in all ammonium uranates, ammonia is combined as NH4+. Infra-red results indicate that the ammonium uranate system is single-phase in which the NH3:U ratio can be varied continuously. In an aqueous environment the variation of composition occurs by a cation exchange mechanism.
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    Haemolytic activity of uranium compounds: haemolysis by thermochemical derivatives of ammonium uranate.
    (Australian Atomic Energy Commission, 1975-01) Stuart, WI; Tucker, AD; Adams, RB; Smith, HE
    A study has been made of the haemolytic action on human erythrocytes by ammonium uranate (AU) and various thermochemical products of AU. These products were obtained by heating AU in hydrogen at 5ºC min-1 to various temperatures. Haemolysis has been interpreted in terms of a diffusion model which for each product yields a single parameter Kn, the haemolytic activity factor. The magnitude of Kn is a convenient measure of the ability of a powder to damage erythrocytes. The haemolytic activity of certain thermochemical derivatives indicates an exceptionally high potential for damage to erythrocytes. Infrared and thermoanalytical measurements have shown that the high activity of these products derives principally from a self-reduction reaction, induced by heating AU to 400-420ºC in hydrogen.
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    Hemolysis by asbestos
    (Australian Atomic Energy Commission, 1980-08) Stuart, WI; Price, GH
    Various experimental factors that affect hemolysis by crocidolite and chrysotile were studied. Microscopic observations of cell-fibre interactions were made using a video-scanning technique. The same general pattern of hemolysis can be observed for the two asbestos materials: attachment of a cell to asbestos fibre is an essential requirement for hemolysis; hemolysis of a cell is preceded by a prolytic stage in which the optical density of the cell does not change; hemolysis is a comparatively sudden event in which hemoglobin is released over a period of about 30 s. Nevertheless, significant differences can be observed in the interaction of the two materials with erythrocytes, namely: (i) there are observable differences in the mode of attachment of cells to fibre. These presumably arise from the differing surface properties of the two minerals. (ii) the duration of prolysis observed for crocidolite is very much greater than for chrysotile, so the rates of hemolysis are correspondingly less. (iii) the duration of prolysis is, on average, reduced by increasing the extent of agitation of cell-crocidolite suspension. These results suggest that boundary layer diffusion may be an important factor in determining rates of prolytic transport phenomena.
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    Interaction of erythrocytes and hexavalent uranium compounds - an autoanalytical study.
    (Australian Atomic Energy Commission, 1980-05) Stuart, WI; Shying, ME
    An automated analytical system was devised to measure the kinetics of hemolysis by uranyl compounds. Accurate plots of percentage hemolysis v. time were obtained; these together with the corresponding differential curves show that hemolysis of plasma-free erythrocytes is a two-stage process. The first stage of hemolysis is particularly affected by pH and anion content of uranyl solutions and also by incubation of cell suspensions at 37 deg. before mixing with lysing solution. Complementary studies involving Coulter counting and microscopic observation established the general pattern of hemolysis and showed that cell agglutination is a prominent feature of the interaction of cells with uranyl solutions.
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    Study of the variables affecting the corrosion of beryllium in carbon dioxide
    (Australian Atomic Energy Commission., 1961-12) Draycott, A; Nicholson, FD; Price, GH; Stuart, WI
    Beryllium is a favoured canning and/or moderating material in the proposed Australian High Temperature Gas Cooled Reactor. With carbon dioxide as the most likely coolant a detailed knowledge of the corrosion of beryllium in this gas is required. Two separate investigations have proceeded simultaneously. First the effect of the following variables was studied; surface preparation of the specimen, temperature (100—725ºC), pressure (0—280 p.s.i.g.), velocity, and impurity content of the gas. The influence of irradiation has not yet been studied. Autoclaves, thermobalances, and dynamic loops were used. The results were statistically analysed and kinetic data obtained. In all cases specimens with etched surfaces yielded approximately 25 — 30 per cent, greater weight gains than specimens with ground or polished surfaces. On extruded material no "breakaway" oxidation was encountered below 650ºC in commercially dry gas (< 20 p.p.m. moisture). The rate of attack was to some extent affected by the pressure of the gas. Breakaway was only observed in one series of specimens at 650ºC. In this particular case the gas pressure was 280 p.s.i.g. However, it seems that surface temperatures of beryllium cans made from extruded material should be maintained below 650ºC in a reactor system using the commercially pure carbon dioxide as coolant. In the second approach a more basic study of the chemistry of the reaction was made as well as a detailed investigation into the variation caused by differences in the composition and fabrication of the metal. Spiral spring balances at atmospheric pressure were used. Extruded material made from beryllium powder oxidized in dry oxygen for a short period of time had greatly enhanced oxidation resistance when exposed to carbon dioxide. Some of the material exposed to wet carbon dioxide at 700ºC and atmospheric pressure did not exhibit "breakaway" oxidation. The weight gains after 1,000 hours exposure under these conditions were never greater than 0.5 mg/cmZ, Some comparisons were made between the reaction rates of beryllium with oxygen and carbon dioxide. In certain circumstances dry oxygen gave breakaway oxidation whereas carbon dioxide did not.
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    Thermal decomposition of ammonium uranates
    (Australian Atomic Energy Commission, 1973-04) Price, GH; Stuart, WI
    Thermal decomposition of ammonium uranates in various atmospheres was studied using thermogravimetric analysis, differential thermogravimetric analysis, differential thermal analysis and infra-red spectrophotometry. The various stages of decomposition are discussed in terms of reaction mechanisms. The effect of nitrate impurities on thermal decomposition is briefly described. It is concluded that the ammonium uranate system at equilibrium is a continuous non-stoichiometric system with zeolitic properties.