Hydrogeologic analyses in support of the conceptual model for the LANL Area G LLRW performance assessment

The Los Alamos National Laboratory low level radioactive waste disposal facility at Area G is currently completing a draft of the site Performance Assessment. Results from previous field studies have estimated a range in recharge rate up to 1 cm/yr. Recent estimates of unsaturated hydraulic conductivity for each stratigraphic layer under a unit gradient assumption show a wide range in recharge rate of 10{sup {minus}4} to 1 cm/yr depending upon location. Numerical computations show that a single net infiltration rate at the mesa surface does not match the moisture profile in each stratigraphic layer simultaneously, suggesting local source or sink terms possibly due to surface connected porous regions. The best fit to field data at deeper stratigraphic layers occurs for a net infiltration of about 0.1 cm/yr. A recent detailed analysis evaluated liquid phase vertical moisture flux, based on moisture profiles in several boreholes and van Genuchten fits to the hydraulic properties for each of the stratigraphic units. Results show a near surface infiltration region averages 8m deep, below which is a dry, low moisture content, and low flux region, where liquid phase recharge averages to zero. Analysis shows this low flux region is dominated by vapor movement. Field data from tritium diffusion studies, from pressure fluctuation attenuation studies, and from comparisons of in-situ and core sample permeabilities indicate that the vapor diffusion is enhanced above that expected in the matrix and is presumably due to enhanced flow through the fractures. Below this dry region within the mesa is a moisture spike which analyses show corresponds to a moisture source. The likely physical explanation is seasonal transient infiltration through surface-connected fractures. This anomalous region is being investigated in current field studies, because it is critical in understanding the moisture flux which continues to deeper regions through the unsaturated zone

Cornerstones of Sampling of Operator Theory

This paper reviews some results on the identifiability of classes of operators whose Kohn-Nirenberg symbols are band-limited (called band-limited operators), which we refer to as sampling of operators. We trace the motivation and history of the subject back to the original work of the third-named author in the late 1950s and early 1960s, and to the innovations in spread-spectrum communications that preceded that work. We give a brief overview of the NOMAC (Noise Modulation and Correlation) and Rake receivers, which were early implementations of spread-spectrum multi-path wireless communication systems. We examine in detail the original proof of the third-named author characterizing identifiability of channels in terms of the maximum time and Doppler spread of the channel, and do the same for the subsequent generalization of that work by Bello. The mathematical limitations inherent in the proofs of Bello and the third author are removed by using mathematical tools unavailable at the time. We survey more recent advances in sampling of operators and discuss the implications of the use of periodically-weighted delta-trains as identifiers for operator classes that satisfy Bello's criterion for identifiability, leading to new insights into the theory of finite-dimensional Gabor systems. We present novel results on operator sampling in higher dimensions, and review implications and generalizations of the results to stochastic operators, MIMO systems, and operators with unknown spreading domains

Busted Butte Unsaturated Zone Transport Test: Fiscal Year 1998 Status Report Yucca Mountain Site Characterization Program Deliverable SPU85M4

This report describes the status of the Busted Butte Unsaturated Zone Transport Test (UZTT) and documents the progress of construction activities and site and laboratory characterization activities undertaken in fiscal year 1998. Also presented are predictive flow-and-transport simulations for Test Phases 1 and 2 of testing and the preliminary results and status of these test phases. Future anticipated results obtained from unsaturated-zone (UZ) transport testing in the Calico Hills Formation at Busted Butte are also discussed in view of their importance to performance assessment (PA) needs to build confidence in and reduce the uncertainty of site-scale flow-and-transport models and their abstractions for performance for license application. The principal objectives of the test are to address uncertainties associated with flow and transport in the UZ site-process models for Yucca Mountain, as identified by the PA working group in February 1997. These include but are not restricted to: (1) The effect of heterogeneities on flow and transport in unsaturated and partially saturated conditions in the Calico Hills Formation. In particular, the test aims to address issues relevant to fracture-matrix interactions and permeability contrast boundaries; (2) The migration behavior of colloids in fractured and unfractured Calico Hills rocks; (3) The validation through field testing of laboratory sorption experiments in unsaturated Calico Hills rocks; (4) The evaluation of the 3-D site-scale flow-and-transport process model (i.e., equivalent-continuum/dual-permeability/discrete-fracture-fault representations of flow and transport) used in the PA abstractions for license application; and (5) The effect of scaling from lab scale to field scale and site scale

Albuquerque, New Mexico, USA: A sunbelt city rapidly outgrowing its aquifer

Albuquerque, New Mexico, is located along the Rio Grande in central New Mexico, at an elevation of 5280 feet. Albuquerque`s climate reflects its high desert setting; average annual precipitation in the basin is only 8 to 10 inches. The Albuquerque metropolitan area is part of the rapidly growing {open_quotes}sunbelt{close_quotes} region of the southwestern United States and is undergoing rapid development. The municipal, industrial, and residential water needs of the entire population are currently met by groundwater, while agricultural needs within the basin are met by surface water diverted from the Rio Grande. While the city is blessed with an extremely productive aquifer, current metropolitan area annual groundwater extractions of 170,000 acre-feet far exceed the sustainable yield of the aquifer. Continued drawdown will lead to greater pumping costs, ground surface subsidence problems, and eventual aquifer depletion. At the same time, industrial and non-point-source contamination and naturally occurring arsenic levels are raising concerns about groundwater quality. New Mexico water law has required the City to acquire surface water rights and allocations on the Rio Grande sufficient to offset estimated losses from the river induced by the City`s groundwater extraction. It has become increasingly clear that the induced recharge had been greatly overestimated, and that the City is thus not actually consuming its surface water as intended. The City, in cooperation with local, state, and federal agencies, has explored a variety of conjunctive use proposals, all designed to permit the City to use its surface water more directly. The City Council is presently considering a strategy calling for full use of the city`s surface water resources and creation of a groundwater drought reserve. Implementation of this strategy will require regulatory approval and major capital investment, both of which require political support

Mobility of Metal Tracers in Unsaturated Tuffs of Busted Butte, Nevada

A complex tracer mixture was injected continuously for over two years into a 10 m x 10 m x 7 m block of unsaturated tuff as part of the Busted Butte unsaturated-zone tracer test at Yucca Mountain. The test was designed to measure tracer transport within the Topopah Springs and Calico Hills tuffs, units that occur between the potential high-level nuclear waste repository at Yucca Mountain and the water table below. The mixture included nonreactive (Br, I, and fluorinated benzoic acids (FBAs)) and reactive tracers (Li, Ce, Sm, Ni, Co, and Mn). Bromide, I, FBAs, and Li were detected during the test on absorbent pads emplaced in a series of solute collection boreholes located beneath the injectors but the more strongly sorbing metals did not reach the collection boreholes during this period. To determine the distribution and mobility of these metals, tracer constituents were extracted from tuff samples collected during overcoring and mineback of the test block. Tracers were extracted from the tuff samples by leaching with a 5% nitric acid solution for metals and a bicarbonate-carbonate buffer for anions. Results from the overcore sample suite show that metals have migrated through the tuff in the region adjacent to and immediately below the tracer injectors. Consistent with laboratory sorption measurements and observed breakthrough in the collection boreholes, rock analyses showed that Li is the most mobile of the metals. Co and Ni behave similarly, traveling tens of cm from the injection sites, while Sm and Ce moved far less, possibly due to precipitation reactions in addition to sorption. Determination of Mn transport is complicated by high background concentrations in the tuff; additional background samples are currently being evaluated. As expected, the rock analyses show that the nonreactive tracers Br and FBAs have moved beyond the overcore region, corroborating results from collection boreholes

Busted Butte: Achieving the Objectives and Numerical Modeling Results

The Unsaturated Zone Transport Test (UZTT) at Busted Butte is a mesoscale field/laboratory/modeling investigation designed to address uncertainties associated with flow and transport in the UZ site-process models for Yucca Mountain. The UZTT test facility is located approximately 8 km southeast of the potential Yucca Mountain repository area. The UZTT was designed in two phases, to address five specific objectives in the UZ: the effect of heterogeneities, flow and transport (F&T) behavior at permeability contrast boundaries, migration of colloids , transport models of sorbing tracers, and scaling issues in moving from laboratory scale to field scale. Phase 1A was designed to assess the influence of permeability contrast boundaries in the hydrologic Calico Hills. Visualization of fluorescein movement , mineback rock analyses, and comparison with numerical models demonstrated that F&T are capillary dominated with permeability contrast boundaries distorting the capillary flow. Phase 1B was designed to assess the influence of fractures on F&T and colloid movement. The injector in Phase 1B was located at a fracture, while the collector, 30 cm below, was placed at what was assumed to be the same fracture. Numerical simulations of nonreactive (Br) and reactive (Li) tracers show the experimental data are best explained by a combination of molecular diffusion and advective flux. For Phase 2, a numerical model with homogeneous unit descriptions was able to qualitatively capture the general characteristics of the system. Numerical simulations and field observations revealed a capillary dominated flow field. Although the tracers showed heterogeneity in the test block, simulation using heterogeneous fields did not significantly improve the data fit over homogeneous field simulations. In terms of scaling, simulations of field tracer data indicate a hydraulic conductivity two orders of magnitude higher than measured in the laboratory. Simulations of Li, a weakly sorbing tracer, indicate less retardation than predicted from laboratory batch measurements

Chlorine-36 investigations of groundwater infiltration in the Exploratory Studies Facility at Yucca Mountain, Nevada

Chlorine-36, including the natural cosmogenic component and the component produced during atmospheric nuclear testing in the 1950`s and 1960`s (bomb pulse), is being used as an isotopic tracer for groundwater infiltration studies at Yucca Mountain, a potential nuclear waste repository. Rock samples have been collected systematically in the Exploratory Studies Facility (ESF), and samples were also collected from fractures, faults, and breccia zones. Isotopic ratios indicative of bomb-pulse components in the water ({sup 36}Cl/Cl values > 1,250 x 10{sup {minus}15}), signifying less than 40-yr travel times from the surface, have been detected at a few locations within the Topopah Spring Tuff, the candidate host rock for the repository. The specific features associated with the high {sup 36}Cl/Cl values are predominantly cooling joints and syngenetic breccias, but most of the sites are in the general vicinity of faults. The non-bomb pulse samples have {sup 36}Cl/Cl values interpreted to indicate groundwater travel times of at least a few thousand to possibly several hundred thousand years. Preliminary numerical solute-travel experiments using the FEHM (Finite Element Heat and Mass transfer) code demonstrate consistency between these interpreted ages and the observed {sup 36}Cl/Cl values but do not validate the interpretations

The flight control system for the experimental aircraft programme (EAP) demonstrator aircraft

Published in: Active control systems - review, evaluation and projections, Conference Proceedings no. 384Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman