A Model for Colloid Facilitated Radionuclide Transport Through Fractured Media
Title | A Model for Colloid Facilitated Radionuclide Transport Through Fractured Media PDF eBook |
Author | Paul Aidan Smith |
Publisher | |
Pages | 38 |
Release | 1993 |
Genre | |
ISBN |
A model for colloid facilitated radionuclide transport through fracture media
Title | A model for colloid facilitated radionuclide transport through fracture media PDF eBook |
Author | P. A. Smith |
Publisher | |
Pages | 0 |
Release | 1993 |
Genre | |
ISBN |
A Model for Colloid Facilitated Radionuclide Transport Through Fractured Media
Title | A Model for Colloid Facilitated Radionuclide Transport Through Fractured Media PDF eBook |
Author | Paul Aidan Smith |
Publisher | |
Pages | 0 |
Release | 1993 |
Genre | Chemisorption |
ISBN |
Colloid and Colloid-Facilitated Contaminant Transport Experiments and Models to Support Assessments of Radionuclide Migration at Yucca Mountain and the Nevada Test Site
Title | Colloid and Colloid-Facilitated Contaminant Transport Experiments and Models to Support Assessments of Radionuclide Migration at Yucca Mountain and the Nevada Test Site PDF eBook |
Author | P. Reimus |
Publisher | |
Pages | 1 |
Release | 2004 |
Genre | |
ISBN |
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.
Colloid Migration in Fractured Media
Title | Colloid Migration in Fractured Media PDF eBook |
Author | |
Publisher | |
Pages | 4 |
Release | 1989 |
Genre | |
ISBN |
Field studies at the Nevada Test Site by researchers at Lawrence Livermore National Laboratory have demonstrated that radionuclides are being transported by colloidal material suspended in groundwater. This observation is counter to most predictions from contaminant transport models because the models assume adsorbed species are immobile. The purpose of this research is to quantify the transport processes for colloidal materials and develop the mechanistic understanding necessary to predict radionuclide transport in fractured media. There were three areas of investigation during this year that have addressed these issues: chemical control of colloid deposition on clean mineral surfaces, colloid accumulation on fracture surfaces, and the influence of deposited colloids on colloid and tracer migration. 7 refs.
Colloid-facilitated Radionuclide Transport in Fractured Porous Rock
Title | Colloid-facilitated Radionuclide Transport in Fractured Porous Rock PDF eBook |
Author | Inseok Baek |
Publisher | |
Pages | 128 |
Release | 1994 |
Genre | |
ISBN |
Colloid Facilitated Transport in Fractured Rock
Title | Colloid Facilitated Transport in Fractured Rock PDF eBook |
Author | |
Publisher | |
Pages | 5 |
Release | 2002 |
Genre | |
ISBN |
Many contaminants in groundwater strongly interact with the immobile porous matrix, which retards their movement relative to groundwater flow. Colloidal particles, which are often present in groundwater, have a relatively small size and large specific surface area which makes it possible for them to also adsorb pollutants. The sorption of tracers to colloids may enhance their mobility in groundwater, relative to the case where colloids are not present. A class of pollutants for which colloid-facilitated transport may be of particular significance are radioactive isotopes. A major reason for why geologic repositories are considered suitable for the disposal of spent nuclear fuel is the strong affinity of many radionuclides to adsorb onto the porous matrix. Therefore, radionuclides accidentally released, would be contained in the geological media by adsorption or filtration until sufficient decay takes place. However, the presence of colloids may enhance radionuclide mobility in the groundwater, and reduce the efficiency of geologic media to act as a natural barrier.