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  • Author or Editor: D. Thomas x
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Abstract  

An effort to define and characterize the environmental effects that control the release and mobility of radon in the environment is presented. The results of our preliminary field experiments on the long-term study of our radon activity measurements are reported.

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Abstract  

Nuclear resonance scattering has been applied to the measurement of copper. It has been shown that this method is sufficiently sensitive to measure, in-vivo, liver copper accumulations associated with certain diseases. The method and some preliminary results are described.

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Abstract  

Three different methods for determining the long-lived radionuclide contents of highly neutron activated metal wastes are being compared and assessed using samples of pressurized-water reactor (PWR) and boiling-water reactor (BWR) spent fuel disassembly hardware and control rods. These methods include: 1) empirical analyses involving sampling and laboratory measurements; 2) direct assay techniques; 3) calculation methods. These techniques are discussed and the results of the comparisons made to date are presented. The agreement between empirical versus calculational methods for the disassembly hardware was generally within 10% to 50%, and rarely exceeded a factor of 2.5, especially near the fueled region of the reactor core. However, large discrepancies between the measured versus calculated concentrations were observed for59Ni and63Ni at the end fittings of the fuel assembly hardware, where the calculations underestimated the concentrations by factors varying from about 8 to 28. The calculation errors are believed to be due to inadequate cross section data for the nickel isotopes.

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Abstract  

Nickel sulphide (NiS) was characterised using X-ray diffraction, thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). The 'as received' Millerite, stoichiometric NiS, observed to be slightly nickel deficient, was found to readily decompose in a nitrogen atmosphere at elevated temperatures (450C max.) to the sulphur deficient Godlevskite, Ni7S6. DSC and X-ray measurements demonstrated that the high temperature form of the Godlevskite was readily stabilised at room temperature. The kinetics of the α-β re-transformation in Godlevskite were then investigated using DSC and were observed to be first order.

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Abstract  

The hydration products of hydrothermally cured OPC-quartz blends incorporating clay-brick waste were characterised using simultaneous DTA-TG, XRD and SEM. The exotherm above 800°C on the DTA curve, due to the formation of β-wollastonite (β-CS) was related to the compressive strength. The area and/or height of the exotherm increased with compressive strength and was due primarily to the presence of calcium silicate hydrate phases including 1.1 nm tobermorite. Supporting evidence is provided by XRD and SEM.

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Abstract  

Toughened glass panels used as a glazing material in multistorey buildings are known to fracture prematurely when they contain nickel sulfide inclusions as a result of the α-β phase recrystallisation in nickel sulfide. The kinetics of this recrystallisation were studied by differential scanning calorimetry (DSC) under isothermal and non-isothermal conditions. The recrystallisation was observed to be a two-step process with an induction period followed by the phase change. A two-stage kinetic model was used to estimate the recrystallisation time under ambient conditions. These values were found to correlate well with the observed time to failure for glass panels installed in multistorey buildings.

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The amorphous state of solids is characterized by a higher chemical and physical reactivity and a hygroscopic behaviour. Furthermore processing of amorphous powders is often difficult, because of the instability. Fast crystallizations, precipitations and milling favour the formation of the amorphous state. Galenical processes like granulation, drying, lyophilization, mixing, may also induce amorphous regions in the drug products.

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The behaviour of the system PbO-PbSO4 was studied between 400 and 900°. Three basic sulphates could be identified by X-ray diffractometry namely: PbO · ·PbSO4; 2 PbO·PbSO4 and 4 PbO·PbSO4.

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Abstract  

Three different spent control rods were obtained for direct-assay measurements and empirical sampling and analysis. They were: 1) a BWR cruciform control rod, 2) a PWR rod-cluster control assembly, and 3) a burnable poison-rod assembly. The dominant activity of the BWR cruciform control rod and the PWR burnable poison-rod assembly is60Co, whereas the PWR rod-cluster control assembly is dominated not only by60Co, but also by108mAg and110mAg, which are found in the Ag–In–Cd alloy of the absorber rods. The radionuclide inventories calculated for the three spent control rods from the empirical sampling data agree very well with data determined from the two direct assay methodologies. The concentration of108mAg in the rod-cluster control assembly will have to be considered when these types of spent control rods are prepared for waste disposal.

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