Yucca Mountain Saturated Zone Carbon-14

This Scientific Investigation Plan (SIP) provides an overview of the work described in “Yucca Mountain Saturated Zone Carbon-14”, a proposal funded by the U.S. Department of Energy’s (DOE) Office of Repository Development under the UCCSN/YMP Co-op in support of the Science and Technology Initiatives. The objective of this work is to provide improved estimates of the time required for ground water to travel from the site of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, to the accessible environment

Groundwater Flow and Thermal Modeling to Support a Preferred Conceptual Model for the Large Hydraulic Gradient North of Yucca Mountain

This task will create a two-dimensional, saturated zone, vertical cross-section model of groundwater flow and thermal transport through the large hydraulic gradient (LHG). This model is referenced herein as the thermal model. The scope of this study is limited to presenting a postulated hydrogeologic configuration of the LHG. The conceptualization will include the use of postulated hydrogeologic structures and material properties. The thermal model will be spatially limited to the area immediately upgradient and downgradient of the LHG and will not reproduce the many hydrogeologic features of the existing regional and site-scale models. The thermal model will be orientated north to south, approximately along a saturated zone streamline. The results of the thermal modeling will be compared to temperature data reported for site wells by the U.S. Geological Survey (USGS) and in peer-reviewed journals. Most, if not all, of this reported data is non- qualified. This task will not qualify the reported data and the reported data will be used only as a basis of comparison for the model simulations

Phase Stability and Segregation in Alloy 22 Base Metal and Weldments

The current design of the waste disposal containers relies heavily on encasement in a multi-layered container, featuring a corrosion barrier of Alloy 22, a Ni-Cr-Mo-W based alloy with excellent corrosion resistance over a wide range of conditions. The fundamental concern from the perspective of the Yucca Mountain Project, however, is the inherent uncertainty in the (very) long-term stability of the base metal and welds. Should the properties of the selected materials change over the long service life of the waste packages, it is conceivable that the desired performance characteristics (such as corrosion reistance) will become compromised, leading to premature failure of the system. To address this, we will study the phase stability and solute segregation characteristics of Alloy 22 base metal and welds. A better understanding of the underlying microstructural evolution tendencies, and their connections with corrosion behavior will (in turn) produce a higher confidence in the extrapolated behavior of the container materials over time periods that are not feasibly tested in a laboratory. Additionally, the knowledge gained here may potentially lead to cost savings through development of safe and realistic design constraints and model assumptions throughout the entire disposal system

Interorganizational Performance Comparisons Using Quality Assurance Audit Results

The Government Performance and Results Act (GPRA) of 1993 requires government agencies to conduct performance measurements of their contractors for purposes of evaluation and comparison. To be most meaningful, performance comparisons need to consider all relevant characteristics that are of importance to the agency. Yet, bounded rationality theory states that managers of complex programs may have insufficient time and resources to consider all potentially relevant factors. Therefore, metrics used for decision making need to incorporate all relevant factors before the information is provided to decision makers. Over the last several decades, government agencies have increasingly identified Quality Assurance compliance as a characteristic of concern for government contractors. Nevertheless, government agencies, such as the United States Department of Energy (DOE), infrequently conduct quantitative performance comparisons of their contractors with respect to quality assurance compliance. When agencies do conduct the comparisons, the agencies generally use results from quality assurance audits. However, while audit results are quantitative and readily available, they generally do not address all relevant factors. Providing these incomplete data to decision makers increases the risk of making less than optimal decisions. This research investigated the feasibility of using statistical regression techniques to transform raw audit results into more meaningful data that government decision makers could use to meet the intent of the GPRA\u27s performance comparison requirements. The research used existing data from 398 DOE audits of 60 government contractors to develop fixed-effects models of quality assurance compliance. The research results show that using raw audit results for contractor performance comparisons may lead to inappropriate ranking of contractors. In order to ensure more accurate ranking of contractors, comparison metrics that use audit results must account for audit-specific variables that increase the depth of the audit. Audit-specific variables such as audit duration, audit team size, number of audit modules, and the time between successive audits contribute to the number of issues found during an audit and need to be accounted for in relative performance metrics

Geostatistical and Stochastic Study of Radio nuclide Transport in the Unsaturated Zone at Yucca Mountain

The U.S. Nuclear Waste Technical Review Board [Cohon et al. 1998] evaluated the technical and scientific validity of activities undertaken by the Secretary of Energy to characterize Yucca Mountain, Nevada, for its suitability as an underground repository in which to store high-level radioactive waste and spent nuclear fuel. In the report, the Board pinpointed that the study on groundwater flow and radionuclide transport in the saturated and unsaturated zones below Yucca Mountain should, over the next several years, focus on reducing prediction uncertainty. In its 2002, the Board repeated this concern by stating, “… hydrogeologic processes that affect radionuclide transport below the proposed repository in the unsaturated and saturated zones remain poorly understood.” However, above the saturated zone, the unsaturated zone (UZ), the area in which the repository would be located, acts as a critical natural barrier by delaying the arrival of radionuclides at the saturated zone and by reducing radionuclide concentrations in groundwater through dispersion and dilution. Before any analysis of saturated zone behavior becomes relevant, quantitative prediction of radionuclide transport in the unsaturated zone becomes critical for performance assessment and design of the repository of the Yucca Mountain Project (YMP)

NSHE/YMP Nuclear Waste Cooperative Agreement

The United States Department of Energy (DOE) and the Nevada System of Higher Education (NSHE) have established a Cooperative Agreement (Co-op) entitled: “Scientific & Engineering Studies of the High-Level Waste Repository at Yucca Mountain (DE-FC28-04RW12232). The Harry Reid Center for Environmental Studies (HRC) administers the Co-op under project activity ORD-FY04-001. In accordance with 10 CFR 600.150, the HRC conducted an audit for the purpose of managing and monitoring project activities supported under the Co-op. The audit was limited to an investigation of technical productivity and schedule. Financial compliance and quality assurance compliance issues were outside the scope of this audit. The audit was conducted during the fourth quarter of federal fiscal year 2006 which is the third year of the Coop’s five year project period

Precarious Rock Methodology for Seismic Hazard: Physical Testing, Numerical Modeling, and Coherence Studies

The precarious rock methodology used for seismic hazard assessment includes location, age dating, field measurements of the quasi-static toppling acceleration of balanced rocks, and study of their dynamic response to realistic strong motion seismograms using numerical modeling. The work scope is contained in the task description issued by the DOE to the Seismology Laboratory of the University of Nevada, Reno and is itemized in section 2.3 below. In addition, measurement of the coherence of seismic energy at high frequencies, critical to the understanding of the variability of high frequency ground motions at the repository level, will be estimated based on data collected in limited scope portable instrument deployments. Existing high-frequency geophones that remain in place from earlier geophysical experiments will be used

Extreme Ground Motion Studies

This project consists of two separate investigations into extreme ground motions due to seismic events. First, it includes field studies of geological formations that should put an upper bound on extreme ground motions that have happened at the site of the formations. The locations are critically selected to provide the most effective constraints possible on the validity of the probabilistic seismic hazard analysis for Yucca Mountain. Second, this project surveys recorded ground motions from around the world, and aims to draw general conclusions from these as to the conditions where extreme ground motions are observed

Chemical Analyses in Support of Yucca Mountain Studies

The objective of this task “Chemical Analyses in Support of Yucca Mountain Studies” is to provide the Department of Energy (DOE) with data and reports from comprehensive chemical analyses of waters sampled from the wells of the Nye County Early Warning Drilling Program (NCEWDP), the Inyo County’s Drilling Program, and the Nye county Tracer Test. In addition, this task will be used to provide other laboratory support needs as they arise within the Yucca Mountain Project. This support is provided by the Harry Reid Center for Environmental Studies (HRC) at University of Nevada, Las Vegas (UNLV), which is part of the University and Community College System of Nevada (UCCSN)

Long-Term Mechanical Behavior of Yucca Mountain Tuffs, and its Variability

We propose to continue the investigation of the long term strength of Yucca Mountain tuffs, with particular emphasis on tuffs from and near the emplacement horizon. We propose to also continue and expand the investigation of the spatial variability of rock strength and stiffness. An intrinsic component of this planned rock testing is the testing of rock joints. Although the emphasis is on tests aimed at determining long term strength, as part of the testing measurements of stiffness also are collected, and will be collected, reported, and analyzed