[en] The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure

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[en] Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La_2-xSr_xCuO₄, YBa₂Cu₃O_7-δ, YBa₂Cu₄O₈, and the Bi₂Sr₂Ca_n-1Cu_nO₂₊₄ (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible

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[en] The fracture stress of several types of U,Pu)C/sub 1+x/ pellets was measured from 25⁰ to 1200⁰C at a fixed strain rate. The fracture stress increases with temperature and the fracture is predominantly transgranular up to approx. = 500⁰C. At > 500⁰C, the fracture stress decreases as the temperature increases and the fracture becomes increasingly intergranular. The flow stress, delta ₀₀₀₂, decreased rapidly between 1000⁰ and 1600⁰C. An investigation of the stress dependence and kinetics of crack healing at 1300⁰ to 1600⁰C indicates that strength may recover by a volume-diffusion-controlled mechanism

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[en] The elastic, diffusional, and mechanical-properties data for carbide and nitride nuclear fuels, including UC, UN, (U,Pu)C, (U,Pu)N, and some mixed systems are summarized and critically reviewed. The review was written in an attempt to unify the understanding of these important materials as well as to provide an objective source of information for fuel-element designers. Important phenomena that have not been explored or are inadequately understood are cited, and recommendations for additional studies are made. (Auth.)

[en] A preliminary small-angle scattering (SANS) experiment has been performed on MnO single crystal at the Intense Pulsed Neutron Source. The experiment was preformed at 1700⁰K at oxygen partial pressures of 2.2 x 10^-4, 1 x 10², and 2 x 10² Pa, which resulted in deviations from stoichiometry of about 0.0015, 0.082, and 0.127. No statistically significant change in SANS was observed at this temperature with the pressure changes. Neither was any significant change observed in the wavelength-dependent sample transmission, also measured in-situ as a function of pressure. Therefore, either clustering of cation vacancies is negligible in MnO for these conditions, or the clusters are smaller than about 5 A. Of proposed cluster configurations, only the existence of the smallest (4:1, 6:2, or possible 8:3) appears to be consistent with these results

[en] The Hertzian indentation technique has been used to determine the fracture toughness, K_Ic of two borosilicate glasses developed to contain high-level nuclear waste. For the product VG 98/12, adding selected groups of fission products leaves K_Ic unchanged, but addition of Pb lowers K_Ic by approx. 20%. Radiation with 77 MeV α-particles to a dose of approx. 10¹⁵ α/cm² increases K_Ic by approx. 75%. For the product SM 58 LW 11, the fracture toughness was measured on pieces taken from different parts of a large cylinder to investigate the effects of segregation phenomena and of partial crystallization and formation of small cristobalite inclusions which decrease K_Ic by approx. 25%