Download or read book Colloid Facilitated Transport of Low Solubility Radionuclides written by R. W. Williams and published by . This book was released on 2003 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the last several years, the Underground Test Area (UGTA) program has funded a series of studies carried out by scientists to investigate the role of colloids in facilitating the transport of low-solubility radionuclides in groundwater, specifically plutonium (Pu). Although the studies were carried out independently, the overarching goals of these studies has been to determine if colloids in groundwater at the NTS can and will transport low-solubility radionuclides such as Pu, define the geochemical mechanisms under which this may or may not occur, determine the hydrologic parameters that may or may not enhance transport through fractures and provide recommendations for incorporating this information into future modeling efforts. The initial motivation for this work came from the observation in 1997 and 1998 by scientists from Lawrence Livermore National Laboratory (LLNL) and Los Alamos National Laboratory (LANL) that low levels of Pu originally from the Benham underground nuclear test were detected in groundwater from two different aquifers collected from wells 1.3 km downgradient (Kersting et al., 1999). Greater than 90% of the Pu and other radionuclides were associated with the naturally occurring colloidal fraction (

Download or read book Colloid Facilitated Transport of Radionuclides Through the Vadose Zone written by John F. McCarthy and published by . This book was released on 2006 with total page 317 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main purpose of this project was to advance the basic scientific understanding of colloid and colloid-facilitated Cs transport of radionuclides in the vadose zone. We focused our research on the hydrological and geochemical conditions beneath the leaking waste tanks at the USDOE Hanford reservation. Specific objectives were (1) to determine the lability and thermodynamic stability of colloidal materials, which form after reacting Hanford sediments with simulated Hanford Tank Waste, (2) to characterize the interactions between colloidal particles and contaminants, i.e., Cs and Eu, (3) to determine the potential of Hanford sediments for \textit{in situ} mobilization of colloids, (4) to evaluate colloid-facilitated radionuclide transport through sediments under unsaturated flow, (5) to implement colloid-facilitated contaminant transport mechanisms into a transport model, and (6) to improve conceptual characterization of colloid-contaminant-soil interactions and colloid-facili\-tated transport for clean-up procedures and long-term risk assessment. We have previously shown that upon contact with simulated waste tank solutions, Hanford sediments change their mineralogical composition. Certain minerals, i.e., quartz, smectite, and kaolinite, are partially dissolved, and new mineral phases, i.e., the feldspathoids cancrinite and sodalite, are formed. We have characterized these mineral transformations and clarified the mineral transformation pathways. The new minerals were mainly in the colloidal size fraction (diameter less than 2 mum), had a negative surface charge, and were microporous, meaning they contained small pores. When Cs was present during the formation of the minerals, contaminants, like Cs, could be trapped inside the mineral structure. Transport experiments under water saturated and unsaturated conditions showed that the colloids were mobile in Hanford sediments. As the water saturation of the sediments decreased, the amount of colloids transported also decreased. The colloids had the ability to enhance the migration of the radionuclide Cs; however, Cs initially sorbed to colloids was desorbed during transport through uncontaminated Hanford sediments. The finding that Cs was stripped off the colloids during the transport through uncontaminated sediments implies that colloids will likely not be an effective carrier for Cs, unless the Cs is incorporated into the mineral structure of the colloids such that the radionuclide cannot desorb from the colloids. Nevertheless, it appears that the amount of Cs that can be transported by mobile colloids beneath Hanford waste tanks is limited. Colloids will not be able to move the bulk mass of Cs through the vadose zone at Hanford. Colloid stability studies indicate that Hanford sediment form stable colloidal suspensions when suspended in Hanford sediment pore waters. Colloid stability was assessed by determination of the critical coagulation concentration, i.e., the chemical electrolyte concentration at which colloidal suspensions flocculate and settle out (become unstable). Although in the stable mode, Hanford colloids will settle out of solution after extended periods of time (months to years). Given the low recharge rates at Hanford range, which from near 0 to more than 100 mm/year, and the long travel times for rainwater to reach the groundwater of more than 40 years, it appears that colloidal transport is unlikely to occur if colloids are initially to be suspended close to the soil surface by infiltrating rainwater. However, if preferential flow or transient flow occurs, then colloidal transport may become more important. The results of this project have also led to improvements of our fundamental understanding of colloid transport and mobilization under unsaturated flow conditions in porous media. We have found that colloid attachment to the liquid-gas interface is not that relevant and that colloids rather attached near the triple phase interface where air, water, and solid phases meet. We have also found that capillary forces are the most dominant forces governing colloid release in unsaturated porous media. These results help to advance our understanding of colloid fate and transport in unsaturated porous media.

Download or read book Colloid Facilitated Transport of Radionuclides Through the Vadose Zone written by and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project seeks to improve the basic understanding of colloid and colloid- facilitated transport of Cs in the vadose zone. The specific objectives are: (1) Determine the structure, composition, and surface charge characteristics of colloidal particles formed under conditions similar to those occurring during leakage of waste typical of Hanford tank supernatants into soils and sediments surrounding the tanks. (2) Characterize the mutual interactions between colloids, contaminant, and soil matrix in batch experiments under various ionic strength and pH conditions. We will investigate the nature of the solid-liquid interactions and the kinetics of the reactions. (3) Evaluate mobility of colloids through soil under different degrees of water saturation and solution chemistry (ionic strength and pH). (4) Determine the potential of colloids to act as carriers to transport the contaminant through the vadose zone and verify the results through comparison with field samples collected under leaking tanks. Results of this project will help to understand the fundamental mechanisms of Cs transport under the leaking Hanford tanks, and thus contribute to the long-term clean-up strategies at the Hanford site.

Download or read book M4FT 16LL080303052 State of Knowledge for Colloid Facilitated Radionuclide Transport and Update on Actinide Diffusion in Bentonite Backfill written by and published by . This book was released on 2016 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: This progress report (Level 4 Milestone Number M4FT-16LL080303052) summarizes research conducted at Lawrence Livermore National Laboratory (LLNL) within the Crystalline Disposal R & D Activity Number FT-16LL080303051 and Crystalline International Collaborations Activity Number FT-16LL080303061. The focus of this research is the interaction of radionuclides with Engineered Barrier System (EBS) and host rock materials at various physico-chemical conditions relevant to subsurface repository environments. They include both chemical and physical processes such as solubility, sorption, and diffusion. The colloid facilitated transport effort focused on preparation of a draft manuscript summarizing the state of knowledge and parameterization of colloid facilitated transport mechanisms in support of reactive transport and performance assessment models for generic crystalline repositories. This draft manuscript is being submitted as a level 3 milestone with LANL as the primary author. LLNL's contribution to that effort is summarized only briefly in the present report. A manuscript summarizing longterm U(VI) diffusion experiments through bentonite backfill material was recently accepted for publication; the contents of that manuscript are summarized in the present report. The Np(IV) diffusion experiments were started mid-year and are ongoing. The completion of these experiments is planned for early FY17. Our progress in quantifying Np(IV) diffusion in bentonite backfill is summarized in the present report. Our involvement with the NEA TDB project was summarized in a recent Argillite Disposal activity report. It is not included in this report.

Download or read book Radionuclide Behaviour in the Natural Environment written by Christophe Poinssot and published by Elsevier. This book was released on 2012-09-20 with total page 737 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding radionuclide behaviour in the natural environment is essential to the sustainable development of the nuclear industry and key to assessing potential environmental risks reliably. Minimising those risks is essential to enhancing public confidence in nuclear technology. Scientific knowledge in this field has developed greatly over the last decade.Radionuclide behaviour in the natural environment provides a comprehensive overview of the key processes and parameters affecting radionuclide mobility and migration. After an introductory chapter, part one explores radionuclide chemistry in the natural environment, including aquatic chemistry and the impact of natural organic matter and microorganisms. Part two discusses the migration and radioecological behavior of radionuclides. Topics include hydrogeology, sorption and colloidal reactions as well as in-situ investigations. Principles of modelling coupled geochemical, transport and radioecological properties are also discussed. Part three covers application issues: assessment of radionuclide behaviour in contaminated sites, taking Chernobyl as an example, estimation of radiological exposure to the population, performance assessment considerations related to deep geological repositories, and remediation concepts for contaminated sites. With its distinguished editors and international team of expert contributors, Radionuclide behaviour in the natural environment is an essential tool for all those interested or involved in nuclear energy, from researchers, designers and industrial operators to environmental scientists. It also provides a comprehensive guide for academics of all levels in this field. Provides a comprehensive overview of the key processes and parameters affecting radionuclide mobility and migration Explores radionuclide chemistry in the natural environment Discusses the migration and radioecological behaviour of radionuclides

Download or read book Long Term Colloid Mobilization and Colloid Facilitated Transport of Radionuclides in a Semi Arid Vadose Zone written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface movement were stronger than during the receding movement. Theory indicates that, for hydrophilic colloids, the advancing interface movement generally exerts a stronger detachment force than the receding, except when the hysteresis of the colloid-air-water contact angle is small. These results of our study are particularly relevant for colloid mobilization and transport related to three process in the vadose zone at Hanford: (1) water infiltration into sediments during rainfall or snowmelt events, (2) groundwater fluctuations as caused by river stage fluctuations, and (3) steady-state, low-flow recharge in deep vadose zone sediments. Transient water flow, like during infiltration or groundwater level fluctuations, are most conducive for colloid mobilization, but even during steady-state, low-flow recharge, colloids can be mobile, although to a much lesser extent. The results of this project have led to a comprehensive and fundamental understanding of colloid transport and mobilization under unsaturated flow conditions at the Hanford site.

Download or read book Colloid Facilitated Radionuclide Transport written by and published by . This book was released on 2017 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report provides an overview of the current state of knowledge of colloid-facilitated radionuclide transport from a nuclear waste repository risk assessment perspective. It draws on work that has been conducted over the past 3 decades, although there is considerable emphasis given to work that has been performed over the past 3-5 years as part of the DOE Used Fuel Disposition Campaign. The timing of this report coincides with the completion of a 3-year DOE membership in the Colloids Formation and Migration (CFM) partnership, an international collaboration of scientists studying colloid-facilitated transport of radionuclides at both the laboratory and field-scales in a fractured crystalline granodiorite at the Grimsel Test Site in Switzerland. This Underground Research Laboratory has hosted the most extensive and carefully-controlled set of colloid-facilitated solute transport experiments that have ever been conducted in an in-situ setting, and a summary of the results to date from these efforts, as they relate to transport over long time and distance scales, is provided in Chapter 3 of this report.

Download or read book Progress Report on Colloid facilitated Transport at Yucca Mountain written by and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Uncertainty Underground written by Allison Macfarlane and published by MIT Press. This book was released on 2006 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experts from science, industry, and government discuss the unresolved scientific and technical issues surrounding the Yucca Mountain site as a geologic repository for high-level nuclear waste.

Download or read book Negotiation de la paix de Ryswick ou l an examine les droits et pretentions du Roi de France sur chacun des serenissimes princes alliez et les droits et pretentions des princes alliez sur le Roi de France written by and published by . This book was released on 1697 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloid and Colloid facilitated Radionuclide Transport at the Semi arid Hanford Site written by Ziru Liu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 3. To simulate long-term water flow and colloid transport with Hanford's meteorological and climatic information.

Download or read book International Seaweed Symposium 11 written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloid facilitated Radionuclide Transport at Yucca Mountain written by Ines R. Triay and published by . This book was released on 1995 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloid and Colloid Facilitated Contaminant Transport Experiments and Models to Support Assessments of Radionuclide Migration at Yucca Mountain and the Nevada Test Site written by P. Reimus and published by . This book was released on 2004 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, numerous laboratory and field experiments have been conducted to assess and parameterize colloid and colloid-facilitated radionuclide transport for the Yucca Mountain Project and the Nevada Test Site (NTS) Environmental Restoration Project. Radionuclide contamination of ground water currently exists within or near underground nuclear test cavities at the NTS, and the proposed Yucca Mountain high-level nuclear waste repository represents a potential future source of radionuclide contamination of ground water at the NTS. Furthermore, recent field observations have indicated that small amounts of Plutonium, which normally adsorbs very strongly to mineral surfaces in aquifers, can transport quite rapidly and over significant distances in ground water when associated with inorganic colloids (Kersting et al., 1999). Groundwater samples from all over the Nevada Test Site have been analyzed for colloid concentrations and size distributions, and it is clear that there are significant mass loadings of colloids in the ground water at some locations. These colloids represent mobile surface area for potentially transporting strongly-adsorbed radionuclides. Field transport experiments have involved the use of fluorescent-dyed carboxylate-modified latex (CML) microspheres in the 250- to 650-nm diameter size range as surrogates for natural colloids in forced-gradient tracer tests. These experiments have indicated that effective colloid filtration coefficients appear to decrease as time and length scales increase. They suggest that a small fraction of colloids may be able to transport significant distances in groundwater systems. Laboratory experiments have been conducted to determine radionuclide sorption and desorption parameters onto inorganic colloids present in the groundwater systems and also to determine transport parameters for inorganic colloids in both fractured and porous media present at the Nevada Test Site. More recent laboratory experiments have involved injecting inorganic colloids with radionuclides adsorbed onto them into fractured or porous media to determine the ability of the colloids to facilitate the transport of the radionuclides through the media. Recent experiments have also involved comparing the transport behavior of CML microspheres and inorganic colloids so that more defensible inferences about inorganic colloid transport can be made from CML microsphere transport observations in field tracer tests. All of this experimental information has been collectively used to develop a modeling framework for evaluating sensitivities of predicted colloid-facilitated radionuclide transport to various colloid-transport and radionuclide-colloid-interaction parameters. This modeling framework is helping to focus future experimental efforts on processes and parameters that have the greatest potential impact on colloid-facilitated radionuclide transport at the Nevada Test Site.

Download or read book Actinide Nanoparticle Research written by Stepan N. Kalmykov and published by Springer Science & Business Media. This book was released on 2011-06-17 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to cover actinide nano research. It is of interest both for fundamental research into the chemistry and physics of f-block elements as well as for applied researchers such as those studying the long-term safety of nuclear waste disposal and developing remediation strategies. The authors cover important issues of the formation of actinide nano-particles, their properties and structure, environmental behavior of colloids and nanoparticles related to the safe disposal of nuclear wastes, modeling and advanced methods of characterization at the nano-scale.

Download or read book Scale dependence of Collloid facilitated Radionuclide Transport written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Model for Colloid Facilitated Radionuclide Transport Through Fractured Media written by Paul Aidan Smith and published by . This book was released on 1993 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: