This article discusses Public-Access Computer Systems (PACS) and the Internet.

Article discussing hypermedia, interactive multimedia, and virtual realities.

Article commenting on the competitive preferential solvation theory.

Article on the degradation of the metal-cyano complex tetracyanonickelate(II) by cyanide-utilizing bacterial isolates.

Article on the effect of solvent polarity on the fluorescence emission spectra of select five- and six-ring pyrene derivatives.

Article on polycyclic aromatic hydrocarbon solute probes and the evaluation of additional coronene derivatives as possible solvent polarity probe molecules.

Article discussing thermochemical investigations of associated solutions and the calculation of pyrene-dichlorobutane association parameters from measured solubility data.

Article on thermodynamic properties of ternary non-electrolyte solutions and excess molar volumes of 2-propanone-tribromomethane-alkane mixtures.

Article from the Slatonite newspaper about a bid to save the Slaton Harvey House from being demolished.

Article on rate coefficients for the hydrogen atom + ammonia reaction over a wide temperature range.

Article on kinetic and thermochemical studies of the recombination reaction sodium + oxygen + nitrogen from 590 to 1515 K by a modified high-temperature photochemistry technique.

Creep, a potential degradation mechanism of Zircaloy cladding after repository disposal of spent nuclear fuel, has been investigated. The deformation and fracture map methodology has been used to predict maximum allowable initial storage temperatures to achieve a thousand year life without rupture as a function of spent-fuel history. Maximum allowable temperatures are 340{degree}C (613 K) for typically stressed rods (70--100 MPa) and 300{degree}C (573 K) for highly stressed rods (140--160 MPa). 10 refs., 2 figs.

Packages of high-level waste are to be emplaced in unsaturated tuff at the proposed Yucca Mountain repository. Each cylindrical waste package is separated from surrounding rock by a 2-cm air gap. A possible mechanism for release of radionuclides is the dripping of ground water onto waste packages. Drips are assumed to penetrate cracks in failed container and to dissolve radionuclides as the partly failed container fills and overflows. For this wet-drip scenario, with assumed constant drip rate, we have developed analytical solutions for the time-dependent release rates of radionuclides to the surrounding rock. Release rates have been calculated for key radionuclides. 7 refs., 3 figs.

The analytical expression used to model glass reaction in computer simulations such as EQ6 is compared to experiments used to support the simulations. The expression correctly predicts the acceleration observed in experiments performed at high glass surface area/leachant volume ratios (SA/V) upon the formation of secondary phases. High resolution microscopal analysis of reacted glass samples suggests that the accelerated nature of the reaction after secondary phase formation is due to changes in the reaction affinity (i.e., is a solution affect) and not a change in the glass reaction mechanism. Solutions generated on samples reacted in steam are consistent with the effects of the secondary phases predicted in the model. Experiments which lead to the generation of secondary phases within short reaction times can be used to identify important secondary phases which must be included in the data base of computer simulations to correctly project long-term glass reaction behavior. 6 refs., 1 fig., 1 tab.

A repository excavated within the unsaturated zone may release carbon (C)-14 dioxide in amounts that exceed limits imposed by the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC). The release would not threaten the general population, but may expose some hypothetical maximally exposed individual to 0.0005 millirems/year. Yet a repository`s releases of C-14 dioxide are strictly regulated, perhaps unintentionally. The EPA and NRC regulations could force the Department of Energy to design and fabricate an expensive 10,000-year waste package solely for the sake of controlling releases of C-14 dioxide. This paper argues that the repository regulations should exempt releases of C-14 dioxide or at least impose more equitable limits. 21 refs., 1 tab.

A brief description of the Exploratory Shaft based site characterization testing program for the Yucca Mountain Project of the permanent disposal of high level radioactive waste is briefly described in this paper. Details of the testing program are presented in the DOE-issued Site Characterization Plan. Overview of the current planning process and status of various activities is briefly described. This study will reevaluate the mining method, ESF location and any changes in the ESF testing program. 2 refs., 2 figs., 1 tab.

The chemical interactions of dissolved radionuclides with mineral surfaces along flowpaths from the proposed repository to the accessible environment around Yucca Mountain constitute one of the potential barriers to radionuclide migration at the site. Our limited understanding of these interactions suggests their details will be complex and will involve control by numerous chemical and physical parameters. It appears unlikely that we will understand all the details of these reactions or obtain all the site data required to evaluate each of them in the time available for site characterization. Yet, performance assessment calculations will require some form of coupling of chemical interaction models will hydrologic flow models for the site. Clearly, strategies will be needed to bound the problem without compromising the reliability of the performance assessment calculations required for site suitability analysis. The main purpose of this paper is to describe such a strategy. 39 refs., 7 figs., 5 tabs.

The Nuclear Energy Agency of the organization for Economic Cooperation and Development (OECD/NEA) sponsors the International Stripa Project. The objectives of the Stripa Project are to develop techniques for characterizing sites located deep in rock formations that are potentially suitable for the geologic disposal of high-level radioactive wastes and to evaluate particular engineering design considerations that could enhance the long-term safety of a high-level radioactive waste repository in a geologic medium. The purpose of this paper is to briefly summarize the research conducted at Stripa and discuss the ways in which the technology developed for the Stripa Project has been and will be transfered to the United States Civilian Radioactive Waste Management Program`s Yucca Mountain Project. 3 refs., 2 figs.

Solubility and speciation data are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are part of the predictive transport models. Radionuclide solubility studies in groundwaters from a repository region will provide limits on radionuclide concentrations in these waters. Meaningful thermodynamically defined solubility studies must satisfy four criteria: (1) solution equilibrium conditions, (2) effective and complete phase separation, (3) a well-defined solid phase, and (4) knowledge of the speciation/oxidation state of the soluble species at equilibrium. Results from solubility and speciation experiments of {sup 237}NpO{sub 2}{sup +}, {sup 239}Pu{sup 4+}, and {sup 241}Am{sup 3+}/Nd{sup 3+} in J-13 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at three different temperatures (25{degrees}, 60{degrees}, and 90{degrees}C) and pH values (6, 7, and 8.5) are presented.

Computer graphics systems that provide interactive display and manipulation of three-dimensional data are powerful tools for the analysis and communication of technical information required for characterization and design of a geologic repository for nuclear waste. Greater understanding of site performance and repository design information is possible when performance-assessment modeling results can be visually analyzed in relation to site geologic and hydrologic information and engineering data for surface and subsurface facilities. In turn, this enhanced visualization capability provides better communication between technical staff and program management with respect to analysis of available information and prioritization of program planning. A commercially-available computer system was used to demonstrate some of the current technology for three-dimensional visualization within the architecture of systems for nuclear waste management. This computer system was used to interactively visualize and analyze the information for two examples: (1) site-characterization and engineering data for a potential geologic repository at Yucca Mountain, Nevada; and (2) three-dimensional simulations of a hypothetical release and transport of contaminants from a source of radionuclides to the vadose zone. Users may assess the three-dimensional distribution of data and modeling results by interactive zooming, rotating, slicing, and peeling operations. For those parts of the database where information is …

Each waste package in the proposed Yucca Mountain repository is to be separated from surrounded unsaturated rock by a 2-cm air gap annulus. However, if the annulus becomes filled with rock and rubble, there can exist pathways for diffusive release of radionuclides through pore liquid, even if the repository remains unsaturated. The effective diffusion coefficient for radionuclide release through pore liquid in a rubble bed depends on the porosity and moisture content of rubble material and on the geometry and contact area of individual pieces of rubble. Here we present a theoretical analysis of the effective diffusion coefficient for a bed of rubble spheres. The results give a rough indication of the magnitude of the effective diffusion coefficient, and the analysis identifies the parameters that will affect experimental measurements of mass transfer through unsaturated rubble. 3 refs., 1 fig.

Measurements of {sup 36}Cl in cuttings from a borehole that was drilled 387 m into unsaturated tuffs indicate the possible detection of significant radioactive decay of cosmogenic {sup 36}Cl in two of the samples. However, the {sup 36}Cl/Cl ratio was found to vary with the amount of pulverization of the cuttings. Work is in progress to separate the {sup 36}Cl/Cl data into cosmogenic and in situ components. The cosmogenic component will be used to trace very slow water movements through the unsaturated zone. Bomb pulse {sup 36}Cl was observed as deep as 153 m, and this identification is not constrained by the problem with pulverization. This work shows the efficacy of {sup 36}Cl measurements for detecting modern water movements deep in the unsaturated zone. 9 refs., 3 tabs.

The Materials Characterization Center (MCC) at Pacific Northwest Laboratory (PNL) provides well-characterized spent fuel from light-water reactors (LWRs) for use in laboratory tests relevant to nuclear waste disposal in the proposed Yucca Mountain repository. Interpretation of results from tests on spent fuel oxidation, dissolution, and cladding degradation requires information on the inventory and distribution of radionuclides in the initial test materials. The MCC is obtaining this information from examinations of Approved Testing Materials (ATMs), which include spent fuel with burnups from 17 to 50 MWd/kgM and fission gas releases (FGR) from 0.2 to 18%. The concentration and distribution of activation products and the release of volatile fission products to the pellet-cladding gap and rod plenum are of particular interest because these characteristics are not well understood. This paper summarizes results that help define the {sup 14}C inventory and distribution in cladding, the ``gap and grain boundary`` inventory of radionuclides in fuels with different FGRs, and the structure and radionuclide inventory of the fuel rim region within a few hundred micrometers from the fuel edge. 6 refs., 5 figs., 1 tab.

A workshop on applications and enhancements of the TOUGH/MULKOM family of multiphase fluid and heat flow simulation programs was held at Lawrence Berkeley Laboratory on September 13--14, 1990. The workshop was attended by 62 scientists from seven countries with interests in geothermal reservoir engineering, nuclear waste isolation, unsaturated zone hydrology, environmental problems, and laboratory and field experimentation. The meeting featured 21 technical presentations, extended abstracts of which are reproduced in the present volume in unedited form. Simulator applications included processes on a broad range of space scales, from centimeters to kilometers, with transient times from seconds to geologic time scales. A number of code enhancements were reported that increased execution speeds for large 3-D problems by factors of order 20, reduced memory requirements, and improved user-friendliness. The workshop closed with an open discussion session that focussed on future needs and means for interaction in the TOUGH user community. Input from participants was gathered by means of a questionnaire that is reproduced in the appendix. 171 refs., 91 figs., 16 tabs.