Resource Type

Zircaloy cladding degradation under repository conditions (open access)

Zircaloy cladding degradation under repository conditions

Creep, a potential degradation mechanism of Zircaloy cladding after repository disposal of spent nuclear fuel, has been investigated. The deformation and fracture map methodology has been used to predict maximum allowable initial storage temperatures to achieve a thousand year life without rupture as a function of spent-fuel history. Maximum allowable temperatures are 340{degree}C (613 K) for typically stressed rods (70--100 MPa) and 300{degree}C (573 K) for highly stressed rods (140--160 MPa). 10 refs., 2 figs.
Date: December 1, 1990
Creator: Santanam, L.; Raghavan, S.; Chin, B. A. & Shaw, H.
System: The UNT Digital Library
Release rates of radionuclides into dripping ground water (open access)

Release rates of radionuclides into dripping ground water

Packages of high-level waste are to be emplaced in unsaturated tuff at the proposed Yucca Mountain repository. Each cylindrical waste package is separated from surrounding rock by a 2-cm air gap. A possible mechanism for release of radionuclides is the dripping of ground water onto waste packages. Drips are assumed to penetrate cracks in failed container and to dissolve radionuclides as the partly failed container fills and overflows. For this wet-drip scenario, with assumed constant drip rate, we have developed analytical solutions for the time-dependent release rates of radionuclides to the surrounding rock. Release rates have been calculated for key radionuclides. 7 refs., 3 figs.
Date: January 1, 1990
Creator: Sadeghi, M. M.; Lee, W. W. L.; Pigford, T. H. & Chambre, P. L.
System: The UNT Digital Library
The importance of secondary phases in glass corrosion (open access)

The importance of secondary phases in glass corrosion

The analytical expression used to model glass reaction in computer simulations such as EQ6 is compared to experiments used to support the simulations. The expression correctly predicts the acceleration observed in experiments performed at high glass surface area/leachant volume ratios (SA/V) upon the formation of secondary phases. High resolution microscopal analysis of reacted glass samples suggests that the accelerated nature of the reaction after secondary phase formation is due to changes in the reaction affinity (i.e., is a solution affect) and not a change in the glass reaction mechanism. Solutions generated on samples reacted in steam are consistent with the effects of the secondary phases predicted in the model. Experiments which lead to the generation of secondary phases within short reaction times can be used to identify important secondary phases which must be included in the data base of computer simulations to correctly project long-term glass reaction behavior. 6 refs., 1 fig., 1 tab.
Date: December 31, 1990
Creator: Ebert, W.L. & Bates, J.K.
System: The UNT Digital Library
Requirements for controlling a repository`s releases of carbon-14 dioxide; the high costs and negligible benefits (open access)

Requirements for controlling a repository`s releases of carbon-14 dioxide; the high costs and negligible benefits

A repository excavated within the unsaturated zone may release carbon (C)-14 dioxide in amounts that exceed limits imposed by the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC). The release would not threaten the general population, but may expose some hypothetical maximally exposed individual to 0.0005 millirems/year. Yet a repository`s releases of C-14 dioxide are strictly regulated, perhaps unintentionally. The EPA and NRC regulations could force the Department of Energy to design and fabricate an expensive 10,000-year waste package solely for the sake of controlling releases of C-14 dioxide. This paper argues that the repository regulations should exempt releases of C-14 dioxide or at least impose more equitable limits. 21 refs., 1 tab.
Date: April 1, 1990
Creator: Park, U Sun & Pflum, C.G.
System: The UNT Digital Library
Role of underground testing to determine suitability of Yucca Mountain as a potential repository site (open access)

Role of underground testing to determine suitability of Yucca Mountain as a potential repository site

A brief description of the Exploratory Shaft based site characterization testing program for the Yucca Mountain Project of the permanent disposal of high level radioactive waste is briefly described in this paper. Details of the testing program are presented in the DOE-issued Site Characterization Plan. Overview of the current planning process and status of various activities is briefly described. This study will reevaluate the mining method, ESF location and any changes in the ESF testing program. 2 refs., 2 figs., 1 tab.
Date: February 1, 1990
Creator: Kalia, H.N.
System: The UNT Digital Library
A strategy for the derivation and use of sorption coefficients in performance assessment calculations for the Yucca Mountain site (open access)

A strategy for the derivation and use of sorption coefficients in performance assessment calculations for the Yucca Mountain site

The chemical interactions of dissolved radionuclides with mineral surfaces along flowpaths from the proposed repository to the accessible environment around Yucca Mountain constitute one of the potential barriers to radionuclide migration at the site. Our limited understanding of these interactions suggests their details will be complex and will involve control by numerous chemical and physical parameters. It appears unlikely that we will understand all the details of these reactions or obtain all the site data required to evaluate each of them in the time available for site characterization. Yet, performance assessment calculations will require some form of coupling of chemical interaction models will hydrologic flow models for the site. Clearly, strategies will be needed to bound the problem without compromising the reliability of the performance assessment calculations required for site suitability analysis. The main purpose of this paper is to describe such a strategy. 39 refs., 7 figs., 5 tabs.
Date: December 31, 1990
Creator: Meijer, A.
System: The UNT Digital Library
The International Stripa Project: Technology transfer from cooperation in scientific and technological research on nuclear waste disposal (open access)

The International Stripa Project: Technology transfer from cooperation in scientific and technological research on nuclear waste disposal

The Nuclear Energy Agency of the organization for Economic Cooperation and Development (OECD/NEA) sponsors the International Stripa Project. The objectives of the Stripa Project are to develop techniques for characterizing sites located deep in rock formations that are potentially suitable for the geologic disposal of high-level radioactive wastes and to evaluate particular engineering design considerations that could enhance the long-term safety of a high-level radioactive waste repository in a geologic medium. The purpose of this paper is to briefly summarize the research conducted at Stripa and discuss the ways in which the technology developed for the Stripa Project has been and will be transfered to the United States Civilian Radioactive Waste Management Program`s Yucca Mountain Project. 3 refs., 2 figs.
Date: April 1, 1990
Creator: Levich, R. A.; Patera, E. S.; Ferrigan, P. M. & Wilkey, P. L.
System: The UNT Digital Library
Solubility and speciation studies for nuclear repository performance assessment (open access)

Solubility and speciation studies for nuclear repository performance assessment

Solubility and speciation data are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are part of the predictive transport models. Radionuclide solubility studies in groundwaters from a repository region will provide limits on radionuclide concentrations in these waters. Meaningful thermodynamically defined solubility studies must satisfy four criteria: (1) solution equilibrium conditions, (2) effective and complete phase separation, (3) a well-defined solid phase, and (4) knowledge of the speciation/oxidation state of the soluble species at equilibrium. Results from solubility and speciation experiments of {sup 237}NpO{sub 2}{sup +}, {sup 239}Pu{sup 4+}, and {sup 241}Am{sup 3+}/Nd{sup 3+} in J-13 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at three different temperatures (25{degrees}, 60{degrees}, and 90{degrees}C) and pH values (6, 7, and 8.5) are presented.
Date: October 1, 1990
Creator: Nitsche, H.
System: The UNT Digital Library
Three dimensional visualization breakthrough in analysis and communication of technical information for nuclear waste management (open access)

Three dimensional visualization breakthrough in analysis and communication of technical information for nuclear waste management

Computer graphics systems that provide interactive display and manipulation of three-dimensional data are powerful tools for the analysis and communication of technical information required for characterization and design of a geologic repository for nuclear waste. Greater understanding of site performance and repository design information is possible when performance-assessment modeling results can be visually analyzed in relation to site geologic and hydrologic information and engineering data for surface and subsurface facilities. In turn, this enhanced visualization capability provides better communication between technical staff and program management with respect to analysis of available information and prioritization of program planning. A commercially-available computer system was used to demonstrate some of the current technology for three-dimensional visualization within the architecture of systems for nuclear waste management. This computer system was used to interactively visualize and analyze the information for two examples: (1) site-characterization and engineering data for a potential geologic repository at Yucca Mountain, Nevada; and (2) three-dimensional simulations of a hypothetical release and transport of contaminants from a source of radionuclides to the vadose zone. Users may assess the three-dimensional distribution of data and modeling results by interactive zooming, rotating, slicing, and peeling operations. For those parts of the database where information is …
Date: November 1, 1990
Creator: Alexander, D. H.; Cerny, B. A.; Hill, E. R.; Krupka, K. M.; Smoot, J. L.; Smith, D. R. et al.
System: The UNT Digital Library
The effective diffusion coefficient for porous rubble (open access)

The effective diffusion coefficient for porous rubble

Each waste package in the proposed Yucca Mountain repository is to be separated from surrounded unsaturated rock by a 2-cm air gap annulus. However, if the annulus becomes filled with rock and rubble, there can exist pathways for diffusive release of radionuclides through pore liquid, even if the repository remains unsaturated. The effective diffusion coefficient for radionuclide release through pore liquid in a rubble bed depends on the porosity and moisture content of rubble material and on the geometry and contact area of individual pieces of rubble. Here we present a theoretical analysis of the effective diffusion coefficient for a bed of rubble spheres. The results give a rough indication of the magnitude of the effective diffusion coefficient, and the analysis identifies the parameters that will affect experimental measurements of mass transfer through unsaturated rubble. 3 refs., 1 fig.
Date: January 1, 1990
Creator: Sadeghi, M. M.; Lee, W. W. L.; Pigford, T. H. & Chambre, P. L.
System: The UNT Digital Library
{sup 36}Cl studies of water movements deep within unsaturated tuffs (open access)

{sup 36}Cl studies of water movements deep within unsaturated tuffs

Measurements of {sup 36}Cl in cuttings from a borehole that was drilled 387 m into unsaturated tuffs indicate the possible detection of significant radioactive decay of cosmogenic {sup 36}Cl in two of the samples. However, the {sup 36}Cl/Cl ratio was found to vary with the amount of pulverization of the cuttings. Work is in progress to separate the {sup 36}Cl/Cl data into cosmogenic and in situ components. The cosmogenic component will be used to trace very slow water movements through the unsaturated zone. Bomb pulse {sup 36}Cl was observed as deep as 153 m, and this identification is not constrained by the problem with pulverization. This work shows the efficacy of {sup 36}Cl measurements for detecting modern water movements deep in the unsaturated zone. 9 refs., 3 tabs.
Date: May 1, 1990
Creator: Norris, A. E.; Bentley, H. W.; Cheng, S.; Kubik, P. W.; Sharma, P. & Gove, H. E.
System: The UNT Digital Library
Radionuclide distribution in LWR [light-water reactor] spent fuel (open access)

Radionuclide distribution in LWR [light-water reactor] spent fuel

The Materials Characterization Center (MCC) at Pacific Northwest Laboratory (PNL) provides well-characterized spent fuel from light-water reactors (LWRs) for use in laboratory tests relevant to nuclear waste disposal in the proposed Yucca Mountain repository. Interpretation of results from tests on spent fuel oxidation, dissolution, and cladding degradation requires information on the inventory and distribution of radionuclides in the initial test materials. The MCC is obtaining this information from examinations of Approved Testing Materials (ATMs), which include spent fuel with burnups from 17 to 50 MWd/kgM and fission gas releases (FGR) from 0.2 to 18%. The concentration and distribution of activation products and the release of volatile fission products to the pellet-cladding gap and rod plenum are of particular interest because these characteristics are not well understood. This paper summarizes results that help define the {sup 14}C inventory and distribution in cladding, the ``gap and grain boundary`` inventory of radionuclides in fuels with different FGRs, and the structure and radionuclide inventory of the fuel rim region within a few hundred micrometers from the fuel edge. 6 refs., 5 figs., 1 tab.
Date: September 1, 1990
Creator: Guenther, R. J.; Blahnik, D. E.; Thomas, L. E.; Baldwin, D. L. & Mendel, J. E.
System: The UNT Digital Library
Proceedings of the TOUGH workshop (open access)

Proceedings of the TOUGH workshop

A workshop on applications and enhancements of the TOUGH/MULKOM family of multiphase fluid and heat flow simulation programs was held at Lawrence Berkeley Laboratory on September 13--14, 1990. The workshop was attended by 62 scientists from seven countries with interests in geothermal reservoir engineering, nuclear waste isolation, unsaturated zone hydrology, environmental problems, and laboratory and field experimentation. The meeting featured 21 technical presentations, extended abstracts of which are reproduced in the present volume in unedited form. Simulator applications included processes on a broad range of space scales, from centimeters to kilometers, with transient times from seconds to geologic time scales. A number of code enhancements were reported that increased execution speeds for large 3-D problems by factors of order 20, reduced memory requirements, and improved user-friendliness. The workshop closed with an open discussion session that focussed on future needs and means for interaction in the TOUGH user community. Input from participants was gathered by means of a questionnaire that is reproduced in the appendix. 171 refs., 91 figs., 16 tabs.
Date: September 1, 1990
Creator: Pruess, K.
System: The UNT Digital Library
Approach to developing a ground-motion design basis for facilities important to safety at Yucca Mountain (open access)

Approach to developing a ground-motion design basis for facilities important to safety at Yucca Mountain

The Department of Energy has proposed a methodology for developing a ground-motion design basis for prospective facilities at Yucca Mountain that are important to safety. The methodology utilizes a quasi-deterministic construct that is designed to provide a conservative, robust, and reproducible estimate of ground motion that has a one-in-ten chance of occurring during the preclosure period. This estimate is intended to define a ground-motion level for which the seismic design would ensure minimal disruption to operations; engineering analyses to ensure safe performance in the unlikely event that the design basis is exceeded are a part of the proposed methodology. 8 refs.
Date: April 1, 1990
Creator: King, J. L.
System: The UNT Digital Library
Application of geophysical methods for fracture characterization (open access)

Application of geophysical methods for fracture characterization

One of the most crucial needs in the design and implementation of an underground waste isolation facility is a reliable method for the detection and characterization of fractures in zones away from boreholes or subsurface workings. Geophysical methods may represent a solution to this problem. If fractures represent anomalies in the elastic properties or conductive properties of the rocks, then the seismic and electrical techniques may be useful in detecting and characterizing fracture properties. 7 refs., 3 figs.
Date: January 1, 1990
Creator: Lee, K. H.; Majer, E. L.; McEvilly, T. V. & Morrison, H. F.
System: The UNT Digital Library
A formalism to generate probability distributions for performance-assessment modeling (open access)

A formalism to generate probability distributions for performance-assessment modeling

A formalism is presented for generating probability distributions of parameters used in performance-assessment modeling. The formalism is used when data are either sparse or nonexistent. The appropriate distribution is a function of the known or estimated constraints and is chosen to maximize a quantity known as Shannon`s informational entropy. The formalism is applied to a parameter used in performance-assessment modeling. The functional form of the model that defines the parameter, data from the actual field site, and natural analog data are analyzed to estimate the constraints. A beta probability distribution of the example parameter is generated after finding four constraints. As an example of how the formalism is applied to the site characterization studies of Yucca Mountain, the distribution is generated for an input parameter in a performance-assessment model currently used to estimate compliance with disposal of high-level radioactive waste in geologic repositories, 10 CFR 60.113(a)(2), commonly known as the ground water travel time criterion. 8 refs., 2 figs.
Date: December 31, 1990
Creator: Kaplan, P. G.
System: The UNT Digital Library
A waste package strategy for regulatory compliance (open access)

A waste package strategy for regulatory compliance

This paper summarizes the strategy given in the Site Characterization Plan for demonstrating compliance with the post closure performance objectives for the waste package and the Engineered Barrier System contained in the Code of Federal Regulations. The strategy consists of the development of a conservative waste package design that will meet the regulatory requirements with sufficient margin for uncertainty using a multi-barrier approach that takes advantage of the unsaturated nature of the Yucca Mountain site. 7 refs., 1 fig.
Date: April 1, 1990
Creator: Stahl, D. & Cloninger, M.O.
System: The UNT Digital Library
The use of performance assessments in Yucca Mountain repository waste package design activities (open access)

The use of performance assessments in Yucca Mountain repository waste package design activities

The Yucca Mountain Project is developing performance assessment approaches as part of the evaluations of the suitability of Yucca Mountain as a repository site. Lawrence Livermore National Laboratory is developing design concepts and the scientific performance assessment methodologies and techniques used for the waste package and engineered barrier system components. This paper presents an overview of the approach under development for postclosure performance assessments that will guide the conceptual design activities and assist in the site suitability evaluations. This approach includes establishing and modeling for the long time periods required by regulations: near-field environment characteristics surrounding the emplaced wastes; container materials performance responses; and waste form properties. All technical work is being done under a fully qualified quality assurance program.
Date: January 1, 1990
Creator: Jardine, L.J.
System: The UNT Digital Library
An experimental program for testing the validity of flow and transport models in unsaturated tuff: The Yucca Mountain Project (open access)

An experimental program for testing the validity of flow and transport models in unsaturated tuff: The Yucca Mountain Project

Groundwater flow and contaminant transport through the unsaturated zone are receiving increased attention as options for waste disposal in saturated media continue to be considered as a potential means for resolving the nation`s waste management concerns. An experimental program is being developed to test the validity of conceptual flow and transport models that are being formulated to predict the long-term performance at Yucca Mountain. This program is in the developmental stage and will continue to evolve as information is acquired and knowledge is improved with reference to flow and transport in unsaturated fractured media. The general approach for directing the validation effort entails identifying those processes which may cause the site to fail relative to imposed regulatory requirements, evaluating the key assumptions underlying the conceptual models used or developed to describe these processes, and developing new conceptual models as needed. Emphasis is currently being placed in four general areas: flow and transport in unsaturated fractures; fracture-matrix interactions; infiltration flow instability; and evaluation of scale effects in heterogeneous fractured media. Preliminary results and plans or each of these areas for both the laboratory and field investigation components will be presented in the manuscript. 1 ref.
Date: October 1, 1990
Creator: Shephard, L. E.; Glass, R. J.; Siegel, M. D. & Tidwell, V. C.
System: The UNT Digital Library
Basaltic volcanic episodes of the Yucca Mountain region (open access)

Basaltic volcanic episodes of the Yucca Mountain region

The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs.
Date: March 1, 1990
Creator: Crowe, B.M.
System: The UNT Digital Library
Preliminary drift design analyses for nuclear waste repository in tuff (open access)

Preliminary drift design analyses for nuclear waste repository in tuff

The Yucca Mountain Project (YMP) is examining the feasibility of siting a repository for high-level nuclear waste at Yucca Mountain, on and adjacent to the Nevada Test Site (NTS). The proposed repository will be excavated in the Topopah Spring Member, which is a moderately fractured, unsaturated, welded tuff. Excavation stability will be required during construction, waste emplacement, retrieval (if required), and closure to ensure worker safety. The subsurface excavations will be subject to stress changes resulting from thermal expansion of the rock mass and seismic events associated with regional tectonic activity and underground nuclear explosions (UNEs). Analyses of drift stability are required to assess the acceptable waste emplacement density, to design the drift shapes and ground support systems, and to establish schedules and cost of construction. This paper outlines the proposed methodology to assess drift stability and then focuses on an example of its application to the YMP repository drifts based on preliminary site data. Because site characterization activities have not begun, the database currently lacks the extensive site-specific field and laboratory data needed to form conclusions as to the final ground support requirements. This drift design methodology will be applied and refined as more site-specific data are generated and …
Date: January 30, 1990
Creator: Hardy, M. P.; Brechtel, C. E.; Goodrich, R. R. & Bauer, S. J.
System: The UNT Digital Library
Basic research for assessment of geologic nuclear waste repositories: What solubility and speciation studies of transuranium elements can tell us (open access)

Basic research for assessment of geologic nuclear waste repositories: What solubility and speciation studies of transuranium elements can tell us

Solubility and speciation data are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are part of predictive transport models. Results from solubility and speciation experiments of {sup 237}NpO{sub 2} {sup +}, {sup 239}Pu{sup 4+}, and {sup 241}Am{sup 3+}/Nd{sup 3+} in J-13 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a candidate high-level nuclear waste disposal site) at three different temperatures (25{degrees}, 60{degrees}, and 90{degrees}C) and pH values (6, 7, and 8.5) are presented and compared with published modeling calculations. The comparison results indicate that there is a great need for experimental data on the solubility and speciation of transuranium elements under a wide range of conditions, for example, pH, Eh, temperature, and composition of groundwaters. Additionally, the influence of alpha radiation and the radiolysis of the secondary transuranium solids on solubility and speciation should be studies. Solubility studies and model calculations should be extended to other important long-lived nuclear waste radionuclides such as nickel, zirconium, cadmium, radium, and thorium. 14 refs., 13 figs., 5 tabs.
Date: December 1, 1990
Creator: Nitsche, H.
System: The UNT Digital Library
Prototype testing for the Yucca Mountain Project (open access)

Prototype testing for the Yucca Mountain Project

The US Department of Energy, through its Yucca Mountain Project Office, has been conducting prototype activities in welded and non-welded tuff. These activities are in preparation for characterization of the Yucca Mountain area, which is under consideration as a site for a geologic repository in which high-level nuclear waste could be safely stored. Investigators from organizations that will conduct the site investigation have been afforded opportunity, through the prototype program, to test, evaluate, and develop instruments, equipment, and methods. The Exploratory Shaft Facility will be used to collect significant amounts of underground site characterization data. The prototype tests are conducted under similar conditions. 3 refs., 4 figs.
Date: February 1990
Creator: Kalia, H. N.; Oliver, R. D. & Girdley, W. A.
System: The UNT Digital Library
{sup 14}C release from failed spent fuel containers (open access)

{sup 14}C release from failed spent fuel containers

Partially failed containers may provide a meaningful barrier to the release of gaseous radionuclides. A modeling approach is outlined and sample calculations are provided that show the effects on release due to a limited perforation area, to decreasing temperature, and to the partial occlusion of the perforated area by corrosion products. 8 refs., 2 tabs.
Date: February 1, 1990
Creator: Pescatore, C.
System: The UNT Digital Library