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Assessment report on the kinetics of radionuclide adsorption on Yucca Mountain tuff

Description: The kinetics of sorption was measured by observing the uptake of radionuclides by tuff wafers and crushed tuff as a function of time. In addition, the broadening of breakthrough curves for cations eluted through crushed-tuff columns was interpreted in terms of adsorption kinetics. The results of these measurements are consistent with a diffusion-limited adsorption mechanism for simple cations, such as strontium, cesium, and barium. The adsorption kinetics for these simple cations is sufficiently fast so that equilibrium can be assumed for the retardation of these chemical species in the groundwater velocities that would be reasonable for most release scenarios. The actinides, in particular plutonium, exhibited a slow time dependence for adsorption. 23 refs., 61 figs., 12 tabs.
Date: July 1, 1987
Creator: Rundberg, R.S.
Partner: UNT Libraries Government Documents Department

Summary report on the geochemistry of Yucca Mountain and environs

Description: This report gives a detailed description of work at Los Alamos that will help resolve geochemical issues pertinent to siting a high-level nuclear waste repository in tuff at Yucca Mountain, Nevada. It is necessary to understand the properties and setting of the host tuff because this rock provides the first natural barrier to migration of waste elements from a repository. The geochemistry of tuff is being investigated with particular emphasis on retardation processes. This report addresses the various aspects of sorption by tuff, physical and chemical makeup of tuff, diffusion processes, tuff/groundwater chemistry, waste element chemistry under expected repository conditions, transport processes involved in porous and fracture flow, and geochemical and transport modeling.
Date: December 1, 1982
Creator: Daniels, W.R.; Wolfsberg, K. & Rundberg, R.S.
Partner: UNT Libraries Government Documents Department

Update report on fracture flow in saturated tuff: Dynamic transport task for the Nevada Nuclear Waste Investigations

Description: This report summarizes the results of continuing experiments on the behavior of tracers during fracture flow in saturated, welded tuff. These experiments were completed during the past year as part of the Dynamic Transport Task of geochemical investigations for the Yucca Mountain Project sponsored by the US Department of Energy. These experiments are designed to investigate the effects of fluid movement in fractures when coupled with matrix diffusion and sorption but isolated from the effects of capillary suction and two-phase flow characteristic of unsaturated conditions. The experiments reported here are continuations of experimental efforts reported previously. The behavior of three tracers [HTO (tritiated water), TcO{sub 4}{sup {minus}} (pertechnetate), and sulforhodamine B dye] have been investigated during flow through a saturated column of densely welded tuff from the Topopah Spring Member of the Paintbrush Tuff, Yucca Mountain, Nye County, southern Nevada. 31 refs., 26 figs., 2 tabs.
Date: November 1, 1990
Creator: Janecky, D.R.; Rundberg, R.S.; Ott, M. & Mitchell, A.
Partner: UNT Libraries Government Documents Department

Size and density of a /sup 242/Pu colloid

Description: The size and density of a /sup 242/Pu colloid has been measured by autocorrelation photon spectrometry. The density of the colloid was determined by ultraspeed centrifugation. From the concentration profiles of /sup 242/Pu in the centrifuged test tubes, a standard sedimentation formula was used to calculate the density; the size of the colloid was known from the light scattering experiments. The determined density of the /sup 242/Pu colloid was unexpectedly low compared to the density of crystalline PuO/sub 2/. 5 refs., 1 tab.
Date: January 1, 1987
Creator: Rundberg, R.S.; Mitchell, A.J. & Torstenfelt, N.B.
Partner: UNT Libraries Government Documents Department

Laboratory studies of radionuclide migration in tuff

Description: The movement of selected radionuclides has been observed in crushed tuff, intact tuff, and fractured tuff columns. Retardation factors and dispersivities were determined from the elution profiles. Retardation factors have been compared with those predicted on the basis of batch sorption studies. This comparison forms a basis for either validating distribution coefficients or providing evidence of speciation, including colloid formation. Dispersivities measured as a function of velocity provide a means of determining the effect of sorption kinetics or mass transfer on radionuclide migration. Dispersion is also being studied in the context of scaling symmetry to develop a basis for extrapolating from the laboratory scale to the field. 21 refs., 6 figs., 2 tabs.
Date: October 1, 1989
Creator: Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Thompson, J.L. & Triay, I.R.
Partner: UNT Libraries Government Documents Department

Numerical simulation of flow and transport in partially saturated, fractured tuff

Description: The unsaturated, fractured tuff of Yucca Mountain in the Nevada Test Site is one of the target sites for geologic storage of high-level radioactive waste. A modeling study of flow and transport in this geologically complex site is presented. Numerical models of mass and heat flow in conjunction with analytical solutions are being used for sensitivity and pathway analysis studies and to aid in design and interpretation of laboratory and field flow and transport tests in tuff. 11 references, 9 figures, 1 table.
Date: December 31, 1983
Creator: Travis, B.J.; Hodson, S.W.; Cook, T.L.; Nuttall, H.E. & Rundberg, R.
Partner: UNT Libraries Government Documents Department

Observation of time dependent dispersion in laboratory scale experiments with intact tuff

Description: The migration of radionuclides through intact tuff was studied using tuff from Yucca Mountain, Nevada. The tuff samples were both highly zeolitized ash-fall tuff from the Calico Hills and densely welded devitrified tuff from the Topopah Springs member of the Paintbrush tuff. Tritiated water and pertechnetate were used as conservative tracers. The sorbing tracers {sup 85}Sr, {sup 137}Cs, and {sup 133}Ba were used with the devitrified tuff only. Greater tailing in the elution curves of the densely welded tuff samples was observed that could be fit by adjusting the dispersion coefficient in the conventional Advection Dispersion Equation, ADE. The curves could be fit using time dependent dispersion as was previously observed for sediments and alluvium by Dieulin, Matheron, and de Marsily. The peak of strontium concentration was expected to arrive after 1.5 years based on the conventional ADE and assuming a linear K{sub d} of 26 ml/g. The observed elution had significant strontium in the first sample taken at 2 weeks after injection. The peak in the strontium elution occurred at 5 weeks. The correct arrival time for the strontium peak was achieved using a one dimensional analytic solution with time dependent dispersion. The dispersion coefficient as a function of time used to fit the conservative tracers was found to predict the peak arrival of the sorbing tracers. The K{sub d} used was the K{sub d} determined by the batch method on crushed tuff. 23 refs., 9 figs., 2 tabs.
Date: December 1, 1989
Creator: Rundberg, R.S.; Triay, I.R.; Ott, M.A. & Mitchell, A.J.
Partner: UNT Libraries Government Documents Department

Current status of crushed rock and whole rock column studies

Description: Measurements on a large number of crushed rock columns of tuff, granite, and argillite are discussed. The isotopes /sup 85/Sr, /sup 137/Cs, /sup 133/Ba, /sup 141/Ce, /sup 152/Eu, /sup 95m/Tc, and /sup 233/U were used. Flow rates were varied from approx. 30 to approx. 30000 m/y. Other parameters studied include isotope concentration and atmosphere. The sorption ratios calculated were compared with batch sorption ratios on the same samples. Methods of studying the movement of radionuclides through whole rock cores are described. The problems associated with sealing the cores to prevent leaking along the exterior surface and one possible solution are discussed. The strontium sorption ratio obtained by elution of one solid tuff core is compared with the batch and crushed rock column sorption ratios.
Date: January 1, 1980
Creator: Vine, E.N.; Daniels, W.R.; Rundberg, R.S. & Thompson, J.L.
Partner: UNT Libraries Government Documents Department

Tracer studies of radionuclide migration in fractured rock at a scale of 1 meter

Description: The Large Block Tracer Test is a series of experiments to study the migration of radionuclides through fractures in rock at the scale of one meter. The separate effects to be considered are sorption onto minerals within the rock matrix; diffusion of radionuclide species through the rock matrix, diffusion and hydrodynamic dispersion within the fracture; and the effect of heterogeneity in the fluid flow field (also known as macro dispersion or channeling). The rock fractures to be used have natural fractures or artificial fractures with engineered heterogeneity. These tracer experiments will provide data with well-defined geometry and conditions for use in code validation. The experiments also provide an experimental framework to test inverse methods. Results are presented for a series of migration experiments using conservative tracers in artificial fractures with near parallel plane and near wedge-shaped fractures. The results are compared with those predicted with transport code TRACR3D. The fracture is treated as an equivalent porous medium with a ``cubic law`` permeability and a porosity that is proportional to the aperture. The results show good agreement, both between experimental results and those predicted by TRACR3D, but also between the distribution of the dye tracer in the fracture and the elution profiles. This suggests that the transport of a tracer through a fracture can be inferred from elution profiles.
Date: March 1, 1995
Creator: Rundberg, R. S.; Travis, B.; Vandergraaf, T. T. & Drew, D. J.
Partner: UNT Libraries Government Documents Department

Review of a field study of radionuclide migration from an underground nuclear explosion at the Nevada Test Site

Description: Results from a long-term (9 year) field study of the distribution of radionuclides around an underground nuclear explosion cavity at the Nevada Test Site are reviewed. The goals of this Radionuclide Migration project are to examine the rates of migration underground in various media and to determine the potential for movement, both on and off the Nevada Test Site, of radioactivity from such explosions, with particular interest in possible contamination of water supplies. Initial studies were undertaken near the site of the low-yield test Cambric, which was detonated 73 m beneath the water table in tuffaceous alluvium. Solid samples were obtained from just below ground surface to 50 m below the detonation point, and water was sampled from five different regions in the vicinity of the explosion. Ten years after the test, most of the radioactivity was found to be retained in the fused debris in the cavity region and no activity above background was found 50 m below. Only tritium and {sup 90}Sr were presented in water in the cavity at levels greater than recommended concentration guides for water in uncontrolled areas. A satellite well is being used to remove water 91 m from the detonation point. During seven years (7 x 10{sup 6} m{sup 3}) of pumping, tritium, {sup 85}Kr, {sup 36}Cl, and {sup 129}I have been detected in the water. Approximately 40% of the total tritium from the cavity region has been removed by pumping at the satellite well, and the maximum in the tritium concentration is clearly defined. Use of sensitive analytical techniques has permitted measurement of the very low concentrations of {sup 36}Cl and {sup 129}I present in the water. The {sup 36}Cl peak precedes the tritiated water, possibly as a result of anion exclusion. Additional analyses are in progress to better define the shape ...
Date: December 31, 1983
Creator: Hoffman, D.C.; Daniels, W.R.; Wolfsberg, K.; Thompson, J.L.; Rundberg, R.S.; Fraser, S.L. et al.
Partner: UNT Libraries Government Documents Department

Migration in alluvium of chlorine-36 and tritium from an underground nuclear test

Description: This article describes a field experiment studying the migration in alluvium of radioactive elements away from an underground nuclear explosion at the Nevada Test Site in the United States. Nuclides detected in the pumped water are tritium, chlorine-36, iodine-129, and krypton-85 - all at levels below the maximum permissible concentration for drinking water in controlled areas. The chlorine-36 elution curve precedes that of tritium, and is due to an anion exclusion process. A conventional two-dimensional convection-diffusion equation does not fully describe the elution curves for tritium and chlorine-36; the tailing of the curves is longer than predicted. Successful modeling of this experiment will be important for validating codes and models to be used in the high-level nuclear waste program.
Date: January 1, 1987
Creator: Ogard, A.E.; Thompson, J.L.; Rundberg, R.S.; Wolfsberg, K.; Kubik, P.W.; Elmore, D. et al.
Partner: UNT Libraries Government Documents Department

Aerosol-Assisted Solid Debris Collection for the National Ignition Facility

Description: The National Ignition Facility (NIF) has been completed and has made its first shots on-target. While upcoming experiments will be focused on achieving ignition, a variety of subsequent experiments are planned for the facility, including measurement of cross sections, astrophysical measurements, and investigation of hydrodynamic instability in the target capsule. In order to successfully execute several of these planned experiments, the ability to collect solid debris following a NIF capsule shot will be required. The ability to collect and analyze solid debris generated in a shot at the National Ignition Facility (NIF) will greatly expand the number of nuclear reactions studied for diagnostic purposes. Currently, reactions are limited to only those producing noble gases for cryogenic collection and counting with the Radchem Apparatus for Gas Sampling (RAGS). The radchem solid collection diagnostic has already been identified by NIF to be valuable for the determination and understanding of mix generated in the target capsule's ablation. LLNL is currently developing this solid debris collection capability at NIF, and is in the stage of testing credible designs. Some of these designs explore the use of x-ray generated aerosols to assist in collection of solid debris. However, the variety of harsh experimental conditions this solid collection device will encounter in NIF are challenging to replicate. Experiments performed by Gary Grim et al. at Sandia National Laboratory's RHEPP1 facility have shown that ablation causes a cloud of material removed from an exposed surface to move normal to and away from the surface. This ablation is certain to be a concern in the NIF target chamber from the prompt x-rays, gamma rays, etc. generated in the shot. The cloud of ablated material could interfere with the collection of the desired reaction debris by slowing down the debris so that the kinetic energy is too low to ...
Date: May 21, 2010
Creator: Nelson, S L; Shaughnessy, D A; Moody, K J; Ivanov, V V; Astanovitskiy, A L; Lewis, L A et al.
Partner: UNT Libraries Government Documents Department

Some geochemical considerations for a potential repository site in tuff at Yucca Mountain, Nevada

Description: The Nevada Nuclear Waste Storage Investigations, which is evaluating potential locations for a high-level waste repository at the Nevada Test Site and environs, is currently focusing its investigations on tuff, principally in Yucca Mountain, as a host rock. This paper discusses some of the geochemical investigations. Particular emphasis is placed on definition of some basic elements and necessary technical approaches for the geochemistry data acquisition and modeling program. Some site-specific tuff geochemical information that is important for site selection and repository performance will be identified and the current status of knowledge will then be discussed.
Date: December 1982
Creator: Erdal, B. R.; Bish, D. L.; Crowe, B. M.; Daniels, W. R.; Ogard, A. E.; Rundberg, R. S. et al.
Partner: UNT Libraries Government Documents Department

Neutron Capture Measurements on Unstable Nuclei at LANSCE

Description: Although neutron capture by stable isotopes has been extensively measured, there are very few measurements on unstable isotopes. The intense neutron flux at the Manual Lujan Jr. Neutron Scattering Center at LANSCE enables us to measure capture on targets with masses of about 1 mg over the energy range from 1 eV to 100 keV. These measurements are important not only for understanding the basic physics, but also for calculations of stellar nucleosynthesis and Science-Based Stockpile Stewardship. Preliminary measurements on {sup 169}Tm and {sup 171}Tm have been made with deuterated benzene detectors. A new detector array at the Lujan center and a new radioactive isotope separator will combine to give Los Alamos a unique capability for making these measurements.
Date: November 4, 1998
Creator: Ullmann, J.; Haight, R.; Wilhelmy, J.; Fowler, M.; Rundberg, R. & Miller, G.
Partner: UNT Libraries Government Documents Department

Search for superradiant emission states in nuclear isomer crystals

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective was to verify the stimulated emission of gamma rays from {sup 125m}Te, as claimed by Russian scientists. The reported cross section for stimulated emission was sufficiently large to allow gain in a single-pass gamma-ray laser. The stimulated emission of gamma rays from a nuclear isomer is expected to result in collinear photons and, therefore, should be observable as a sum peak in the gamma-ray spectrum. Skorobogatov and Dzevitskii reported an increase of an order of magnitude in the sum peak (218.56 keV) when a sample of beryllium telluride containing {sup 125m}Te was cooled from room temperature to near-liquid-helium temperatures. The authors have repeated their experiment and have observed no increase in the sum peak above accidental summing. The upper limit for the stimulated-emission cross section based on the three-standard-deviation statistical error is 6.8 x 10 {sup {minus}21} cm{sup 2}. This result is one order of magnitude lower than the cross section reported by Skorobogatov and Dzevitskii. The cross section would not allow gain in a single-pass gamma-ray laser. Their results support the position of Baldwin and Solem rather than that of Kamenov.
Date: January 1, 1998
Creator: Rundberg, R.S.; Wilhelmy, J.B.; Taylor, R.D.; Solem, J.C.; Fowler, M.M.; Miller, G.G. et al.
Partner: UNT Libraries Government Documents Department

Size determinations of plutonium colloids using autocorrelation photon spectroscopy

Description: Autocorrelation Photon Spectroscopy (APS) is a light-scattering technique utilized to determine the size distribution of colloidal suspensions. The capabilities of the APS methodology have been assessed by analyzing colloids of known sizes. Plutonium(IV) colloid samples were prepared by a variety of methods including: dilution; peptization; and alpha-induced auto-oxidation of Pu(III). The size of theses Pu colloids was analyzed using APS. The sizes determined for the Pu colloids studied varied from 1 to 370 nanometers. 7 refs., 5 figs., 3 tabs.
Date: December 1, 1989
Creator: Triay, I.R.; Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Hobart, D.E.; Palmer, P.D. et al.
Partner: UNT Libraries Government Documents Department

Carbonate adsorption onto goethite as a function of pH and ionic strength. [Yucca Mountain Project:a1]

Description: The adsorption of carbonate onto geothite was studied as a function of both pH and ionic strength (NaClO{sub 4} electrolyte) using {sup 14}C tracer. The pH ranged from 2.5 to 11.6. The ionic strength was controlled by varying the NaClO{sub 4} concentration and ranged from 0.01 to 0.1 molar. The results indicate that carbonate is adsorbed on goethite as primarily an inner-sphere complex at pH values above the point of zero charge. This is inferred from the lack of dependence on ionic strength in the adsorption of carbonate. Below the point of zero charge carbonate is adsorbed by an additional outer-sphere mechanism. An adsorption isotherm was measured at pH 7.0 with an electrolyte concentration of 0.01M. Deconvolution of the isotherm proved that at least two sorption mechanisms exist. These mechanisms lead to large distribution coefficients at low pH. Thereby making the complete removal and exclusion of carbonate from an aqueous goethite system difficult, for the purpose of characterizing a clean'' goethite surface.
Date: January 1, 1991
Creator: Rundberg, R.S. (Los Alamos National Lab., NM (United States)) & Albinsson, Y. (Chalmers Univ. of Tech., Goeteborg (Sweden). Dept. of Nuclear Chemistry)
Partner: UNT Libraries Government Documents Department

Preparation of radioactive rare earth targets for neutron capture study

Description: The understanding of thc details of nucleosynthesis in stars remains a great challenge. Though the basic mechanisms governing the processes have been known since the pioneering work of Burbidge, Burbidge, Fowler and Hoyle (l), we are now evolving into a condition where we can ask more specific questions. Of particular interest are the dynamics of the s ('slow') process. In this process the general condition is one in which sequential neutron captures occur at time scales long compared with the beta decay half lives of the capturing nuclides. The nucleosynthesis period for C or Ne burning stellar shells is believed to be in the year to few year time frame (2). This means that radionuclides with similar half lives to this burning period serve as 'branch point' nuclides. That is, there will be a competition between a capture to the next heavier isotope and a beta decay to the element of nexl higher atomic number. By understanding the abundances of these competing reactions we can learn about the dynamics of the nucleosynthesis process in the stellar medium. Crucial to this understanding is that we have a knowledge of the underlying neutron reaction cross sections on these unstable nuclides in the relevant stellar energy regions (neutrons of 0.1-100 KeV). Tm (1.9 years) and ls'Sm (90 ycws) have decay properties that permit their handling in an open fume hood. These Iwo were therefore selected to be the first radionuclides for neutron capture study in what will be an ongoing effort.
Date: January 1, 2002
Creator: Miller, G. G. (Geoffrey G.); Rogers, P. S. Z. (Pamela S. Z.); Palmer, P. D. (Phillip D.); Dry, D. E. (Donald E.); Rundberg, R. S. (Robert S.); Fowler, Malcolm M. et al.
Partner: UNT Libraries Government Documents Department

Progress on the Europium Neutron-Capture Study using DANCE

Description: The accurate measurement of neutron-capture cross sections of the Eu isotopes is important for many reasons including nuclear astrophysics and nuclear diagnostics. Neutron capture excitation functions of {sup 151,153}Eu targets were measured recently using a 4{pi} {gamma}-ray calorimeter array DANCE located at the Los Alamos Neutron Science Center for E{sub n} = 0.1-100 keV. The progress on the data analysis efforts is given in the present paper. The {gamma}-ray multiplicity distributions for the Eu targets and Be backing are significantly different. The {gamma}-ray multiplicity distribution is found to be the same for different neutron energies for both {sup 151}Eu and {sup 153}Eu. The statistical simulation to model the {gamma}-ray decay cascade is summarized.
Date: September 5, 2006
Creator: Agvaanluvsan, U; Becker, J A; Macri, R A; Parker, W; Wilk, P; Wu, C Y et al.
Partner: UNT Libraries Government Documents Department

Review of Livermore-Led Neutron Capture Studies Using DANCE

Description: We have made neutron capture cross-section measurements using the white neutron source at the Los Alamos Science Center, the DANCE detector array (Detector for Advanced Neutron Capture Experiments) and targets important for basic science and stockpile stewardship. In this paper, we review results from (n,{gamma}) reactions on {sup 94,95}Mo, {sup 152,154,157,160,nat}Gd, {sup 151,153}Eu and {sup 242m}Am for neutron energies from < 1eV up to {approx} 20 keV. We measured details of the {gamma}-ray cascade following neutron capture, for comparison with results of statistical model simulations. We determined the neutron energy dependent (n,{gamma}) cross section and gained information about statistical decay properties, including the nuclear level density and the photon strength function. Because of the high granularity of the detector array, it is possible to look at gamma cascades with a specified number of transitions (a specific multiplicity). We simulated {gamma}-ray cascades using a combination of the DICEBOX/GEANT computer codes. In the case of the deformed nuclei, we found evidence of a scissors-mode resonance. For the Eu, we also determined the (n,{gamma}) cross sections. For the {sup 94,95}Mo, we focused on the spin and parity assignments of the resonances and the determination of the photon strength functions for the compound nuclei {sup 95,96}Mo. Future plans include measurements on actinide targets; our immediate interest is in {sup 242m}Am.
Date: May 11, 2007
Creator: Parker, W; Sheets, S; Agvaanluvsan, U; Becker, J; Becvar, F; Bredeweg, T et al.
Partner: UNT Libraries Government Documents Department

DANCE : a 4[pi] barium fluoride detector for measuring neutron capture on unstable nuclei /.

Description: Measurements of neutron capture on unstable nuclei are important for studies of s-process nucleosynthesis, nuclear waste transmutation, and stewardship science. A 160-element, 4{pi} barium fluoride detector array, and associated neutron flight path, is being constructed to make capture measurements at the moderated neutron spallation source at LANSCE. Measurements can be made on as little as 1 mg of sample material over energies from near thermal to near 100 keV. The design of the DANCE array is described and neutron flux measurements from flight path commissioning are shown. The array is expected to be complete by the end of 2002.
Date: January 1, 2002
Creator: Ullmann, J. L. (John L.); Haight, Robert C.; Hunt, L. F. (Lloyd F.); Reifarth, R. (Rene); Rundberg, R. S. (Robert S.); Bredeweg, T. A. (Todd A) et al.
Partner: UNT Libraries Government Documents Department

The Radiative Strength Function Using the Neutron-Capture Reaction on 151,153Eu

Description: Radiative strength functions in {sup 152,154}Eu nuclei for {gamma}-ray energies below 6 MeV have been investigated. Neutron capture for incident neutron energies <1eV up to 100 keV has been measured for {sup 151,153}Eu targets. Properties of resonances in these two nuclei are examined. The measurements are compared to simulation of cascades performed with various models for the radiative strength function. Comparison between experimental data and simulation suggests an existence of the low-energy resonance in these two nuclei.
Date: October 4, 2005
Creator: Agvaanluvsan, U; Alpizar-Vicente, A; Becker, J A; Becvar, F; Bredeweg, T A; Clement, R et al.
Partner: UNT Libraries Government Documents Department