The electron spin resonance of the Gd3+ ion has been studied in two series of glasses having the molar compositions 6SiO2:5Na2O: x (Gd2O3 + Y2O3) with 0 ≤ x ≤ 0.5 and 500SiO2: x Na2O:1Gd2O3 with 2.5 ≤ x ≤ 494. The spectra were nearly independent of temperature and sample composition, but varied strongly with microwave frequency in the range 5.4–38.4 GHz. The data were interpreted in terms of the spin Hamiltonian for a strong cubic crystal field and also in terms of the usual rhombic spin Hamiltonian H = g 0β H · S + D[Sz2 − (1/3)S  (S + 1)] + E(Sx2 − Sy2) with S = (7/2). Computer calculations were made yielding all possible effective g values for this latter Hamiltonian for all physically distinct combinations of the crystal field parameters when the Zeeman field H was restricted to the x, y, or z direction. The resonance features were related to three distinct sites for the Gd3+ ion. The spectra are indicative of a chemically heterogeneous glass matrix composed of soda-rich, silica-rich, and diffuse transition regions. The heterogeneities were found to exist over the entire range of compositions studied. Variations in the resonance intensity associated with the soda-rich region suggest the existence of a very well-defined substructure within the region. The data indicate that the substructure is related to the fundamental structural features of the possible crystalline compounds which can exist within the composition range.

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This report is the second in a series of summary briefings to the National Academy of Science's (NAS) Committee on Radioactive Waste Management dealing with the feasibility of disposal of heat-producing radioactive waste in silicic tuff. We discuss the interim status of studies of tuff properties determined on samples obtained from Yucca Mountain and Rainier Mesa (G-tunnel) located on the Nevada Test Site (NTS). In particular, we describe progress on resolving issues identified during the first briefing to the NAS which include behavior of water in tuff when heated, the effect of the presence or absence of water and joints on the thermal/physical properties of tuff and the detailed/complex sorptive properties of highly altered and unaltered tuff. Initial correlations of thermal/physical and sorptive properties with the highly variable porosity and mineralogy are described. Three in-situ, at-depth field experiments, one nearly completed and two just getting underway are described. In particular, the current status of mineralogy and petrology, geochemistry, thermal and mechanical, radiation effects and water behavior studies are described. The goals and initial results of a Mine Design Working Group are discussed. Regional factors such as seismicity, volcanism and hydrology are not discussed.

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Tuffp on the Nevada Test Site (NTS) are currently under investigation as a potential isolation medium for heat-producing nuclear wastes. The National Academy of Sciences has concurred in our identification of the potentially large water content (<40 vol%) of ruffs as one of the impor tant issues affecting their suitability for a repository. This Experi mental Plan describes an in-situ experiment intended as an initial assess ment of water generation/migration in response to a thermal input. The experiment will be conducted in the Grouse Canyon Welded Tuff in Tunnel U12g (G-Tunnel) located in the north-central region of the NTS. While the Grouse Canyon Welded Tuff is not a potential repository medium, it has physical, thermal, and mechanical properties very similar to those tuffs currently under consideration and is accessible at depth (-400 m below the surface) in an existing facility. Other goals of the experiment are to support computer-code and instrumentation development, and to measure insitu thermal properties. The experimental array consists of a central electrical heater, 1.2 m long x 10.2 cm diameter, surrounded by three holes f r measuring watermigration behavior, two holes for measuring temperature profiles, one hole for measuring thermally induced stress in the rock, and one hole perpendi cular to the heater to measure displacement with a laser. This Experi mental Plan describes the experimental objectives, the technical issues, tn? site; the experimental array, thermal and thennomechanical modeling results, the instrumentation, the data-acquisit ion system, posttest characterization, and the organizational details.

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it thought at first were so real were anything else after all than ways in which our mental organisation dealt with crude sensations. They might, as Bergson said later on, be the moulds into which we pour our perceptions. Physics set up a test of Reality, the law the results of Biology, but only from its methods. Did Physiology, that is, the Physiology of the Schools, ever really investigate the organism ? A muscle-nerve preparation, an excised kidney through which blood is perfused, an exposed salivary gland which is stimulated, even a frog deprived of its cerebral hemispheres these things are not organisms. They are not permanent centres of action, autonomous