Conceptual model for radionuclide release,Yucca Mountain,Nevada, USA     

John C. Walton  Lubna HamdanArturo Woocay 《Applied Geochemistry》2010

A new conceptual model for release rate of radionuclides from the proposed repository for high level nuclear waste located at Yucca Mountain, Nevada is developed. The model predicts that heat generated from radioactive decay combined with the unsaturated environment will lead to an inward flow system that, under many relevant conditions, will slow the release of and sometimes sequester radionuclides at locations of higher heat release and lower water percolation. The amount of protection will be greatest for more concentrated waste forms such as spent fuel and less for glass waste forms. The redistribution and concentration of the radionuclides is anticipated to significantly delay radionuclide release and create a tendency towards gradual release over time that is independent of localized penetrations of metallic barriers.  相似文献   

Optical and infrared spectroscopy of the type IIn SN 1998S: days 3–127     

A. Fassia  W. P. S. Meikle  N. Chugai  T. R. Geballe  P. Lundqvist  N. A. Walton  D. Pollacco  S. Veilleux  G. S. Wright  M. Pettini  T. Kerr  E. Puchnarewicz  P. Puxley  M. Irwin  C. Packham  S. J. Smartt  D. Harmer 《Monthly notices of the Royal Astronomical Society》2001,325(3):907-930

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Mineralogy,petrology, and shock history of lunar meteorite Sayh al Uhaymir 300: A crystalline impact‐melt breccia     

J. A. Hudgins  E. L. Walton  J. G. Spray 《Meteoritics & planetary science》2007,42(10):1763-1779

Abstract— Sayh al Uhaymir (SaU) 300 comprises a microcrystalline igneous matrix (grain size <10 μm), dominated by plagioclase, pyroxene, and olivine. Pyroxene geothermometry indicates that the matrix crystallized at ?1100 °C. The matrix encloses mineral and lithic clasts that record the effects of variable levels of shock. Mineral clasts include plagioclase, low‐ and high‐Ca pyroxene, pigeonite, and olivine. Minor amounts of ilmenite, FeNi metal, chromite, and a silica phase are also present. A variety of lithic clast types are observed, including glassy impact melts, impact‐melt breccias, and metamorphosed impact melts. One clast of granulitic breccia was also noted. A lunar origin for SaU 300 is supported by the composition of the plagioclase (average An₉₅), the high Cr content in olivine, the lack of hydrous phases, and the Fe/Mn ratio of mafic minerals. Both matrix and clasts have been locally overprinted by shock veins and melt pockets. SaU 300 has previously been described as an anorthositic regolith breccia with basaltic components and a granulitic matrix, but we here interpret it to be a polymict crystalline impact‐melt breccia with an olivine‐rich anorthositic norite bulk composition. The varying shock states of the mineral and lithic clasts suggest that they were shocked to between 5–28 GPa (shock stages S1–S2) by impact events in target rocks prior to their inclusion in the matrix. Formation of the igneous matrix requires a minimum shock pressure of 60 GPa (shock stage >S4). The association of maskelynite with melt pockets and shock veins indicates a subsequent, local 28–45 GPa (shock stage S2–S3) excursion, which was probably responsible for lofting the sample from the lunar surface. Subsequent fracturing is attributed to atmospheric entry and probable breakup of the parent meteor.  相似文献   

Bridging the Divide—A Reply to Mitchell and Peet     

Judy Walton 《The Professional geographer》1996,48(1):98-100

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A comparison of pre‐ and post‐remediation water quality,Mineral Creek,Colorado     

Robert L. Runkel  Kenneth E. Bencala  Briant A. Kimball  Katherine Walton‐Day  Philip L. Verplanck 《水文研究》2009,23(23):3319-3333

Pre‐ and post‐remediation data sets are used herein to assess the effectiveness of remedial measures implemented in the headwaters of the Mineral Creek watershed, where contamination from hard rock mining has led to elevated metal concentrations and acidic pH. Collection of pre‐ and post‐remediation data sets generally followed the synoptic mass balance approach, in which numerous stream and inflow locations are sampled for the constituents of interest and estimates of streamflow are determined by tracer dilution. The comparison of pre‐ and post‐remediation data sets is confounded by hydrologic effects and the effects of temporal variation. Hydrologic effects arise due to the relatively wet conditions that preceded the collection of pre‐remediation data, and the relatively dry conditions associated with the post‐remediation data set. This difference leads to a dilution effect in the upper part of the study reach, where pre‐remediation concentrations were diluted by rainfall, and a source area effect in the lower part of the study reach, where a smaller portion of the watershed may have been contributing constituent mass during the drier post‐remediation period. A second confounding factor, temporal variability, violates the steady‐state assumption that underlies the synoptic mass balance approach, leading to false identification of constituent sources and sinks. Despite these complications, remedial actions completed in the Mineral Creek headwaters appear to have led to improvements in stream water quality, as post‐remediation profiles of instream load are consistently lower than the pre‐remediation profiles over the entire study reach for six of the eight constituents considered (aluminium, arsenic, cadmium, copper, iron, and zinc). Concentrations of aluminium, cadmium, copper, lead, and zinc remain above chronic aquatic‐life standards, however, and additional remedial actions may be needed. Future implementations of the synoptic mass balance approach should be preceded by an assessment of temporal variability, and modifications to the synoptic sampling protocol should be made if necessary. Published in 2009 by John Wiley & Sons, Ltd.  相似文献   

Dilation and Post-peak Behaviour Inputs for Practical Engineering Analysis     

Gabriel Walton  Mark S. Diederichs 《Geotechnical and Geological Engineering》2015,33(1):15-34

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The San Fernando Observatory Video Spectra-Spectroheliograph     

Stephen R. Walton  Gary A. Chapman 《Solar physics》1996,166(2):267-285

We describe recent work in the development of the San Fernando Observatory (SFO) Video Spectra-Spectroheliograph (VSSHG), a spectrum-based instrument for the measurement of the solar Stokes profiles. Its most important features are: simultaneous measurement of Stokes I plus one of Stokes Q, U, or V; spatial sampling of 0.5 arc sec; spectral sampling of 8.8 mÅ; and time sampling of one minute (for one pair of Stokes profile) to three minutes (for all four profiles). Routine data processing is carried out using a moments technique; tests of this technique show it to be reasonably accurate. Sample data are shown and briefly discussed: a longitudinal magnetogram and Dopplergram of NOAA 5573 observed on 17 August, 1989, and a vector magnetic field map and Dopplergram of NOAA 6659 observed on 10 June, 1991.  相似文献   

How Real(ist) Can You Get?*     

Judy R. Walton 《The Professional geographer》1995,47(1):61-65

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Ray Theory for a Pre-strained Medium     

K. Walton 《Geophysical Journal International》1973,33(2):223-235

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Seismic Waves in Pre-strained Media     

K. Walton 《Geophysical Journal International》1973,31(4):373-394

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