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Langevin equation model of dispersion in the convective boundary layer

Description: This dissertation presents the development and evaluation of a Lagrangian stochastic model of vertical dispersion of trace material in the convective boundary layer (CBL). This model is based on a Langevin equation of motion for a fluid particle, and assumes the fluid vertical velocity probability distribution is skewed and spatially homogeneous. This approach can account for the effect of large-scale, long-lived turbulent structures and skewed vertical velocity distributions found in the CBL. The form of the Langevin equation used has a linear (in velocity) deterministic acceleration and a skewed randomacceleration. For the case of homogeneous fluid velocity statistics, this ""linear-skewed" Langevin equation can be integrated explicitly, resulting in a relatively efficient numerical simulation method. It is shown that this approach is more efficient than an alternative using a "nonlinear-Gaussian" Langevin equation (with a nonlinear deterministic acceleration and a Gaussian random acceleration) assuming homogeneous turbulence, and much more efficient than alternative approaches using Langevin equation models assuming inhomogeneous turbulence. "Reflection" boundary conditions for selecting a new velocity for a particle that encounters a boundary at the top or bottom of the CBL were investigated. These include one method using the standard assumption that the magnitudes of the particle incident and reflected velocities are positively correlated, and two alternatives in which the magnitudes of these velocities are negatively correlated and uncorrelated. The constraint that spatial and velocity distributions of a well-mixed tracer must be the same as those of the fluid, was used to develop the Langevin equation models and the reflection boundary conditions. The two Langevin equation models and three reflection methods were successfully tested using cases for which exact, analytic statistical properties of particle velocity and position are known, including well-mixed spatial and velocity distributions. Simulations of laboratory experiments of CBL dispersion show that both homogeneous Langevin equation models can ...
Date: August 1, 1998
Creator: Nasstrom, J S
Partner: UNT Libraries Government Documents Department

Nanometer-scale metal dispersions in polymeric matrices

Description: Rutherford backscattering spectrometry was used to measure the depth distribution of gold nanoparticles within thin layers of poly(t-butyl acrylate)(PTBA). The gold nanoparticles were created by evaporation of a discontinuous gold layer onto a thin film of PTBA. A second PTBA film was placed onto these samples to create ``sandwiches`` in which the gold existed between two PTBA films. Gold particle diffusion coefficients were measured from gold particle depth distributions in annealed samples for which the molecular weights of the two PTBA layers were identical. The experiments revealed that particle mobility was decreased by 2 to 3 orders of magnitude compared with predictions of the Stokes-Einstein model of particle diffusion. This is attributed to bridging interactions between particles arising from slow exchange kinetics of polymer segments at the polymer/metal interface. Experiments for which the molecular weights of the two polymer films are different, are sensitive to the ability of polymer molecules to pass through the gold particle layer. Experiments done with thermally evaporated particles are consistent with a picture in which polymer molecules are able to freely pass through the gold particle layer. Results with gold deposited by electron-beam evaporation are different: the gold is not able to diffuse and polymer molecules not able to penetrate the gold layer. These results, combined with optical absorption experiments, indicate that much smaller particles are obtained by electron-beam evaporation than by thermal evaporation.
Date: January 1, 1997
Creator: Shull, K.R.; Cole, D.H.; Rehn, L.E. & Baldo, P.M.
Partner: UNT Libraries Government Documents Department

Dependance of TWRS FSAR X/Qs on distance and example doses at Highway 240 with stationary and moving receptors

Description: A discussion of the reasons for the dependance of X/Q on receptor distance and compass sector is presented. In addition, X/Qs are calculated for three receptor scenarios on Highway 240 including a moving receptor. Example radiological doses and toxicological exposures at Highway 240 are calculated for two accidents already analyzed in the TWRS FSAR.
Date: September 23, 1996
Creator: Himes, D.A.
Partner: UNT Libraries Government Documents Department

ARAC dispersion modeling of the August 1998 Tracy, California tire fire

Description: At about 4:30 pm PDT on Friday, August 7, 1998 a fire ignited the large tire disposal pit of Royster Tire Co. on Macarthur Drive about 5 km (3 miles) south of downtown Tracy, California. While providing on-scene mutual aid late Friday night, the LLNL Fire Department called and requested that the Atmospheric Release Advisory Capability (ARAC) make a plume forecast for Saturday. The response team in the field was interested in the forecasted location as well as an estimate of potential health effects on the following day. Not having any previous experience with tire fire source terms, ARAC assessors used a constant unit source rate (1 g/s) of particulate and produced plots showing only the location of the ground-level normalized time-integrated air concentrations from the smoke plume. Very early Saturday morning the assessors faxed plots of ground-level smoke air concentrations forecasted for Saturday from 6 am through 6 pm PDT to the Tracy Fire Emergency Operations Center. (As a part of standard procedure, before delivering the plots, the assessors notified ARAC's DOE sponsor.) Fortunately due to the intense heat from the fire, the dense black smoke immediately lofted into the air preventing high ground-level concentrations close to the tire dump. Later on Saturday morning ARAC forecasted a second set of plume integrated air concentrations for Sunday. By Monday the intensity of the fire lessened, and ARAC's support was no longer requested. Following ARAC's response, we made a third calculation on a large scale of the continuous smoke dispersion for 3 days after the fire. A newspaper photograph showed the plume initially rising toward the northeast and the upper part of the smoke cloud turning counterclockwise toward the north. Winds from ARAC's mesoscale prognostic model reproduced this plume structure, while data from the Friday afternoon sounding from Oakland did not. ...
Date: August 28, 1998
Creator: Aluzzi, F J; Baskett, R L; Bowen, B M; Foster, C S; Pace, J C; Pobanz, B et al.
Partner: UNT Libraries Government Documents Department

A model for simulating airflow and pollutant dispersion around buildings

Description: A three-dimensional, numerical mode1 for simulating airflow and pollutant dispersion around buildings is described. The model is based on an innovative finite element approach and fully implicit time integration techniques. Linear and nonlinear eddy viscosity/diffusivity submodels are provided for turbulence parameterization. Mode1 predictions for the flow-field and dispersion patterns around a surface-mounted cube are compared with measured data from laboratory experiments.
Date: February 24, 1999
Creator: Chan, S T & Lee, R L
Partner: UNT Libraries Government Documents Department

Study of Dispersant Agents for Thorium Oxide

Description: S>A preliminary study of dispersing agents for thorium oxide was completed and several of the dispersants have possible uses. Also many of the industrial dispersing agents tested are not usable with thorium oxide due to induced behavior causing balling and caking. The effects of nitric acid concentration were observed to also effect each dispersing agent. (auth)
Date: August 1, 1959
Creator: Bate, L. C. & Leddicotte, G. W.
Partner: UNT Libraries Government Documents Department

PROGRESS RELATING TO CIVILIAN APPLICATIONS DURING DECEMBER 1959

Description: >The creep and stress-rupture propenties of annealed and of 15% cold- worked Zircaloy-2 are being determined at of a AgBr fuel-element leak detector for use in watercooled reactors. The development of a thermal-neutronflux monitoring system was directed toward extending the sensing-probe life, increasing the effective instrument range, and improving the instrument reliability. Resistivity of Al/sub 2/O/sub 3/-MoSi/sub 2/-UO/sub 2/ ceramic tubes was determined to investigate the effects of MoSi/sub 2/ propontion and of extrusion pressure. In the development of corrosion-resistant welding alloys for use with Hastelloy F, a number of alloys are being exposed in boiling Sulfex and Niflex solutions to determine corrosion resistance of these liquids. Corrosion tests in 200-C water for 30 days have shown that the Al--35 wt.% U alloys containing Sn or Zr additives are equivalent to the binary Al--35 wt.% U and superior to 2S Al in their resistance to the corrosion attack of 200 deg C water. Work was continued on the development of a radiometric titration method of determining Al and Fe in portland cement. The investigation of the formation and decay of radiation-induced free radicals was continued. The effect of radiation on the nitration of cyclohexane was stadied over the range of 15 to 70 wt.% HNO/ sub 3/ with a 10-to-1 ratio of organic to acid. An investlgation is being conducted on the effects of combined high pressure and temperature on the uranium oxides and on the reactions of uranium oxides with other oxide systems. An irradiation surveillance program on AISI Type 347 stainless steel is continuing. The alloys which are being investigated as alternate cladding materials for the EBR include Nb, Nb-1.84 wt.% Cr, Hb--3.21 wt.% Cr, Nb--4.33 wt.% Zr. Nb--9.95 wt.% Ta--3.31 wt.% Cr, Nb--39.8 wt.% Ti--10.6 wt.% Al, Nb--20.5 wt.% Ti--4.28 wt.% Cr, and V--11.7 wt.% Ti--3.07 wt.% ...
Date: January 1, 1960
Creator: Dayton, R.W. & Tipton, C.R. Jr.
Partner: UNT Libraries Government Documents Department

Report and analysis of the BULLION forced-gradient experiment

Description: The BULLION Forced-Gradient Experiment (FGE) was conducted in the summer of 1997, starting June 2 and ending August 28. The site of the experiment was the ER-20-6 well field adjacent to the BULLION test. Figure 1-1 shows the location of this site on Pahute Mesa in Area 20 of the Nevada Test Site. Figure 1-2 shows the ER-20-6 site within the Pahute Mesa hydrogeologic framework, and Figure 1-3 shows the site layout with respect to the BULLION test. The purpose of the BULLION FGE was to provide information relevant to the transport of radionuclides in groundwater. Transport of radionuclides from Pahute Mesa is of special concern due to the potential for rapid movement of groundwater in the fractured volcanic rocks comprising the Mesa and formations along the anticipated downgradient path of groundwater. The objective was specifically to observe the transport process and characterize transport parameters (e.g., effective porosity, dispersivity and matrix diffusion) for use in predictive modeling of contaminant transport. Additional objectives were to characterize the hydrologic source term and the relative mobility of mobile radionuclides.
Date: August 1, 1998
Partner: UNT Libraries Government Documents Department

The formation of metal/metal-matrix nano-composites by the ultrasonic dispersion of immiscible liquid metals

Description: Ultrasonic energy has been used to disperse one liquid metallic component in a second immiscible liquid metal, thereby producing a metallic emulsion. Upon lowering the temperature of this emulsion below the mp of the lowest-melting constituent, a metal/metal-matrix composite is formed. This composite consists of sub-micron-to-micron- sized particles of the minor metallic phase that are embedded in a matrix consisting of the major metallic phase. Zinc-bismuth was used as a model system, and ultrasonic dispersion of a minor Bi liquid phase was used to synthesize metal/metal-matrix composites. These materials were characterized using SEM and energy-dispersive x-ray analysis.
Date: December 1, 1996
Creator: Keppens, V.M.; Mandrus, D.; Boatner, L.A. & Rankin, J.
Partner: UNT Libraries Government Documents Department

Potential for radionuclide immobilization in the EBS/NFE: solubility limiting phases for neptunium, plutonium, and uranium

Description: Retardation and dispersion in the far field of radionuclides released from the engineered barrier system/near field environment (EBS/NFE) may not be sufficient to prevent regulatory limits being exceeded at the accessible environment. Hence, a greater emphasis must be placed on retardation and/or immobilization of radionuclides in the EBS/NFE. The present document represents a survey of radionuclide-bearing solid phases that could potentially form in the EBS/NFE and immobilize radionuclides released from the waste package and significantly reduce the source term. A detailed literature search was undertaken for experimental solubilities of the oxides, hydroxides, and various salts of neptunium, plutonium, and uranium in aqueous solutions as functions of pH, temperature, and the concentrations of added electrolytes. Numerous solubility studies and reviews were identified and copies of most of the articles were acquired. However, this project was only two months in duration, and copies of some the identified solubility studies could not be obtained at short notice. The results of this survey are intended to be used to assess whether a more detailed study of identified low- solubility phase(s) is warranted, and not as a data base suitable for predicting radionuclide solubility. The results of this survey may also prove useful in a preliminary evaluation of the efficacy of incorporating chemical additives to the EBS/NFE that will enhance radionuclide immobilization.
Date: October 1, 1997
Creator: Rard, J. A., LLNL
Partner: UNT Libraries Government Documents Department

Pathways for the Oxidation of Sarin in Urban Atmospheres

Description: Terrorists have threatened and carried out chemicalhiological agent attacks on targets in major cities. The nerve agent sarin figured prominently in one well-publicized incident. Vapors disseminating from open containers in a Tokyo subway caused thousands of casualties. High-resolution tracer transport modeling of agent dispersion is at hand and will be enhanced by data on reactions with components of the urban atmosphere. As a sample of the level of complexity currently attainable, we elaborate the mechanisms by which sarin can decompose in polluted air. A release scenario is outlined involving the passage of a gas-phase agent through a city locale in the daytime. The atmospheric chemistry database on related organophosphorus pesticides is mined for rate and product information. The hydroxyl,radical and fine-mode particles are identified as major reactants. A review of urban air chernistry/rnicrophysics generates concentration tables for major oxidant and aerosol types in both clean and dirty environments. Organic structure-reactivity relationships yield an upper limit of 10-1' cm3 molecule-' S-* for hydrogen abstraction by hydroxyl. The associated midday loss time scale could be as little as one hour. Product distributions are difficult to define but may include nontoxic organic oxygenates, inorganic phosphorus acids, sarin-like aldehydes, and nitrates preserving cholinergic capabilities. Agent molecules will contact aerosol surfaces in on the order of minutes, with hydrolysis and side-chain oxidation as likely reaction channels.
Date: November 1, 1998
Creator: Streit, Gerald E.; Bossert, James E.; Gaffney, Jeffrey S.; Reisner, Jon; McNair, Laurie A.; Brown, Michael et al.
Partner: UNT Libraries Government Documents Department

Recent upgrades and enhancements of the FEM3A model

Description: In 1984, the US Army Edgewood Research, Development and Engineering Center began to fund Lawrence Livermore National Laboratory to further develop FEM3, a fully three-dimensional heavy-gas dispersion model, as a research tool for studying the atmospheric transport and diffusion of certain chemical systems. As a result, a significantly improved version of the model, called FEM3A, was delivered to ERDEC in 1988. During the past few years, two more major improvements have been developed and tested. They are: improved mass conservation for treating dispersion scenarios with large density variations, and the addition of an advanced turbulence submodel based on the k-{var_epsilon} transport equations. These enhancements have resulted in substantial improvements in the dispersion simulations of heavy-gases and can greatly extend the range of applicability of the model, including the ability to treat problems with large density variations and dispersion scenarios of much greater complexities. Documented in this report are the new features and some of the improvements obtained with the new model.
Date: December 1, 1994
Creator: Chan, S.T.
Partner: UNT Libraries Government Documents Department

Use of an operational model evaluation system for model intercomparison

Description: The Atmospheric Release Advisory Capability (ARAC) is a centralized emergency response system used to assess the impact from atmospheric releases of hazardous materials. As part of an on- going development program, new three-dimensional diagnostic windfield and Lagrangian particle dispersion models will soon replace ARAC`s current operational windfield and dispersion codes. A prototype model performance evaluation system has been implemented to facilitate the study of the capabilities and performance of early development versions of these new models relative to ARAC`s current operational codes. This system provides tools for both objective statistical analysis using common performance measures and for more subjective visualization of the temporal and spatial relationships of model results relative to field measurements. Supporting this system is a database of processed field experiment data (source terms and meteorological and tracer measurements) from over 100 individual tracer releases.
Date: March 1, 1998
Creator: Foster, K. T., LLNL
Partner: UNT Libraries Government Documents Department

Meteorological data assimilation for real-time emergency response

Description: The US Department of Energy`s Atmospheric Release Advisory Capability (ARAC) provides real-time dose assessments of airborne pollutant releases. Diverse data assimilation techniques are required to meet the needs of a new generation of ARAC models and to take advantage of the rapidly expanding availability of meteorological data. We are developing a hierarchy of algorithms to provide gridded meteorological fields which can be used to drive dispersion codes or to provide initial fields for mesoscale models. Data to be processed include winds, temperature, moisture, and turbulence.
Date: November 1, 1996
Creator: Sugiyama, G. & Chan, S.T.
Partner: UNT Libraries Government Documents Department

Comparison of reflection boundary conditions for langevin equation modeling of convective boundary layer dispersion

Description: Lagrangian stochastic modeling based on the Langevin equation has been shown to be useful for simulating vertical dispersion of trace material in the convective boundary layer or CBL. This modeling approach can account for the effects of the long velocity correlation time scales, skewed vertical velocity distributions, and vertically inhomogeneous turbulent properties found in the CBL. It has been recognized that Langevin equation models assuming skewed but homogenous velocity statistics can capture the important aspects of diffusion from sources in the CBL, especially elevated sources. We compare three reflection boundary conditions using two different Langevin-equation-based numerical models for vertical dispersion in skewed, homogeneous turbulence. One model, described by Ermak and Nasstrom (1995) is based on a Langevin equation with a skewed random force and a linear deterministic force. The second model, used by Hurley and Physick (1993) is based on a Langevin equation with a Gaussian random force and a non-linear deterministic force. The reflection boundary conditions are all based on the approach described by Thompson and Montgomery (1994).
Date: April 1, 1997
Creator: Nasstrom, J.S. & Ermak, D.L.
Partner: UNT Libraries Government Documents Department

New meteorological data assimilation model for real-time emergency response

Description: We are developing a new meteorological data assimilation model for the Atmospheric Release Advisory Capability (ARAC) project at Lawrence Livermore National Laboratory, which provides real-time dose assessments of airborne pollutant releases. The model, ADAPT (Atmospheric Data Assimilation and Parameterization Techniques), builds three-dimensional meteorological fields, which can be used to drive dispersion models or to initialize or evaluate mesoscale models. ADAPT incorporates many new features and substantial improvements over the current ARAC operational models MEDIC/MATHEW, including the use of continuous-terrain variable-resolution grids, the ability to treat assorted meteorological data such as temperatures, pressure, and relative humidity, and a new algorithm to produce mass-consistent wind fields. In this paper, we will describe the main features of the model, current work on a new atmospheric stability parameterization, and show example results.
Date: September 1, 1997
Creator: Sugiyama, G. & Chan, S.T.
Partner: UNT Libraries Government Documents Department

New model for generating mass-consistent wind fields over continuous terrain

Description: Based on a mixed variational principle and the finite element method, a model for efficiently generating mass-consistent wind fields over continuous terraing has been developed. Two numerical examples are presented to demonstrate the applicability of the model.
Date: November 1, 1996
Creator: Chan, S.T. & Sugiyama, G.
Partner: UNT Libraries Government Documents Department

Langevin equation modeling of convective boundary layer dispersion assuming homogeneous, skewed turbulence

Description: Vertical dispersion of material in the convective boundary layer, CBL, is dramatically different than in natural or stable boundary layers, as has been shown by field and laboratory experiments. Lagrangian stochastic modeling based on the Langevin equation has been shown to be useful for simulating vertical dispersion in the CBL. This modeling approach can account for the effects of the long Lagrangian time scales (associated with large-scale turbulent structures), skewed vertical velocity distributions, and vertically inhomogeneous turbulent properties found in the CBL. It has been recognized that simplified Langevin equation models that assume skewed but homogeneous velocity statistics can capture the important aspects of dispersion from sources the the CBL. The assumption of homogeneous turbulence has a significant practical advantage, specifically, longer time steps can be used in numerical simulations. In this paper, we compare two Langevin equations models that use the homogeneous turbulence assumption. We also compare and evaluate three reflection boundary conditions, the method for determining a new velocity for a particle that encounters a boundary. Model results are evaluated using data from Willis and Deardorff`s laboratory experiments for three different source heights.
Date: October 1, 1997
Creator: Hasstrom, J.S. & Ermak, D.L.
Partner: UNT Libraries Government Documents Department

First look at the new ARAC dispersion model

Description: We describe a new atmospheric dispersion model being developed for the emergency response system of the US Department of Energy`s Atmospheric Release Advisory Capability (ARAC). This model solves the turbulent, advection-diffusion equation via a Lagrangian particle, Monte-Carlo method. Within a simulation, particles representing the pollutant are moved through the domain using a random displacement method to model the turbulent diffusion and a Runge-Kutta method to model the advection. The bottom boundary in the new model is a union of bilinear surfaces between gridded terrain data rather than the discontinuous `stair step` representation of terrain used previously in the ARAC. The new model accepts winds on (x,y,o) grids that can be horizontally and vertically graded and nested in the horizontal.
Date: November 1, 1996
Creator: Leone, J.M., Jr.; Nasstrom, J.S. & Maddix, D.M.
Partner: UNT Libraries Government Documents Department

1995 and 1996 Upper Three Runs Dye Study Data Analyses

Description: This report presents an analysis of dye tracer studies conducted on Upper Three Runs. The revised STREAM code was used to analyze these studies and derive a stream velocity and a dispersion coefficient for use in aqueous transport models. These models will be used to facilitate the establishment of aqueous effluent limits and provide contaminant transport information to emergency management in the event of a release.
Date: June 1998
Creator: Chen, K. F.
Partner: UNT Libraries Government Documents Department