Comparative Evaluation and Use of Petrophysically Derived and Laboratory-Measured Core Porosity Data at Yucca Mountain, Nevada

This report addresses the comparative evaluation and use of pertrophysically derived and laboratory-measured core porosity data at Yucca Mountain, Nevada

Analysis of the Massive Salt Fall in Big Hill Cavern 103

This report summarizes recent reviews, observations, and analyses believed to be imperative to our understanding of the recent two million cubic feet salt fall event in Big Hill Cavern 103, one of the caverns of the Strategic Petroleum Reserve (SPR). The fall was the result of one or more stress driven mechanical instabilities, the origins of which are discussed in the report. The work has lead to important conclusions concerning the engineering and operations of the caverns at Big Hill. Specifically, Big Hill, being the youngest SPR site, was subjected to state-of-the-art solutioning methods to develop nominally well-formed, right-circular cylindrical caverns. Examination of the pressure history records indicate that operationally all Big Hill SPR caverns have been treated similarly. Significantly, new three-dimensional (3-D) imaging methods, applied to old (original) and more recent sonar survey data, have provided much more detailed views of cavern walls, roofs, and floors. This has made possible documentation of the presence of localized deviations from ''smooth'' cylindrical cavern walls. These deviations are now recognized as isolated, linear and/or planar features in the original sonar data (circa early 1990s), which persist to the present time. These elements represent either sites of preferential leaching, localized spalling, or a combination of the two. Understanding the precise origin of these phenomena remains a challenge, especially considering, in a historical sense, the domal salt at Big Hill was believed to be well-characterized. However, significant inhomogeneities in the domal salt that may imply abnormalities in leaching were not noted. Indeed, any inhomogeneities were judged inconsequential to the solution-engineering methods at the time, and, by the same token, to the approaches to modeling the rock mass geomechanical response. The rock mass was treated as isotropic and homogeneous, which in retrospect, appears to have been an over simplification. This analysis shows there are possible new opportunities regarding completing an appropriate site characterization for existing operating cavern fields in the SPR, as well as expansion of current sites or development of new sites. Such characterization should first be consistent with needs identified by this report. Secondly, the characterization needs to satisfy the input requirements of the 3-D solutioning calculational methods being developed, together with 3-D geomechanical analyses techniques which address deformation of a salt rock mass that contains inhomogeneities. It seems apparent that focusing on these important areas could preclude occurrence of unexpected events that would adversely impact the operations of SPR

Influence of deterministic geologic trends on spatial variability of hydrologic properties in volcanic tuff

Hydrologic properties have been measured on outcrop samples taken from a detailed, two-dimension grid covering a 1.4 km outcrop exposure of the 10-m thick non-welded-to-welded, shardy base microstratigraphic unit of the Tiva Canyon Member of the Miocene Paintbrush Tuff at Yucca Mountain, Nevada. These data allow quantification of spatial trends in rock matrix properties that exist in this important hydrologic unit. Geologic investigation, combined with statistical and geostatistical analyses of the numerical data, indicates that spatial variability of matrix properties is related to deterministic geologic processes that operated throughout the region. Linear vertical trends in hydrologic properties are strongly developed in the shardy base microstratigraphic unit, and they are more accurately modeled using the concept of a thickness-normalized stratigraphic elevation within the unit, rather than absolute elevation. Hydrologic properties appear to be correlated over distances of 0.25 to 0.3 of the unit thickness after removing the deterministic vertical trend. The use of stratigraphic elevation allows scaling of identified trends by unit thickness which may be of particular importance in a basal, topography-blanketing unit such as this one. Horizontal changes in hydrologic properties do not appear to form obvious trends within the limited lateral geographic extent of the ash-flow environment that was examined. Matrix properties appear to be correlated horizontally over distances between 100 and 400 m. The existence and quantitative description of these trends and patterns of vertical spatial continuity should increase confidence in models of hydrologic properties and groundwater flow in this area that may be constructed to support the design of a potential high-level nuclear waste repository at Yucca Mountain

Application of the SmartSampling Methodology to the Evaluation of Contaminated Landscape Soils at Brookhaven National Laboratory

Portions of the SmartSampling{trademark} analysis methodology have been applied to the evaluation of radioactive contaminated landscape soils at Brookhaven National Laboratory. Specifically, the spatial, volumetric distribution of cesium-137 ({sup 137}Cs) contamination within Area of Concern 16E-1 has been modeled probabilistically using a geostatistical methodology, with the purpose of identifying the likelihood of successfully reducing, with respect to a pre-existing, baseline remediation plan, the volume of soil that must be disposed of offsite during clean-up. The principal objective of the analysis was to evaluate the likelihood of successful deployment of the Segmented Gate System (SGS), a novel remediation approach that emphasizes real-time separation of clean from contaminated materials during remediation operations. One primary requirement for successful application of the segmented gate technology investigated is that a variety of contaminant levels exist at the deployment site, which would enable to the SGS to discriminate material above and below a specified remediation threshold value. The results of this analysis indicate that there is potential for significant volume reduction with respect to the baseline remediation plan at a threshold excavation level of 23 pCi/g {sup 137}Cs. A reduction of approximately 50%, from a baseline volume of approximately 1,064.7 yd{sup 3} to less than 550 yd{sup 3}, is possible with acceptance of only a very small level of engineering risk. The vast majority of this volume reduction is obtained by not excavating almost all of levels 3 and 4 (from 12 to 24 inches in depth), which appear to be virtually uncontaminated, based on the available data. Additional volume reductions related to soil materials on levels 1 (depths of 0--6 inches) and 2 (6--12 inches) may be possible, specifically through use of the SGS technology. Level-by-level evaluation of simulation results suggests that as much as 26 percent of level 1 and as much as 65% of level 2 soils may actually be uncontaminated. Additionally, numerical experiments have been conducted to investigate the effects of selective excavation on the volume and average activity of the remediated materials. These numerical experiments indicate that nonselective excavation may result in mixing of contaminated and uncontaminated materials such that the total volume of material above the threshold excavation level of 23 pCi/g may exceed the baseline volume, thus defeating volume-reduction efforts

THREE-DIMENSIONAL STROCHASTIC ROCK-PROPERTY AND UNCERTAINTY MODELS FOR YUCCA MOUNTAIN, NEVADA

Licensing of Yucca Mountain as a geologic disposal site for high-level nuclear waste will require quantitative predictions of the waste-isolation performance of the rocks that form Yucca Mountain and of the engineered barrier system for an extended period of time into the future. These predictions will require the use of numerical modeling in an attempt to capture the essence of highly complex physical processes, such as ground-water flow and the transport of potential radionuclide contaminants under both unsaturated and saturated conditions. Additional numerical modeling will be required to demonstrate that a mined geologic repository can be constructed safely within the rocks of Yucca Mountain, and that the underground openings will remain stable in the longer term when affected by the thermal pulse of the emplaced waste forms. A fundamental principle involved in the numerical representation of real-world physical processes is that the properties of the modeled domain that are important to that representation must be known ''exhaustively''. Standard procedure in virtually all numerical physical-process modeling is to discretize the model volume into a (large) number of individual elements or grid nodes, assign the necessary attributes to each element or node, and then apply one or more sets of mathematical expressions that are believed to represent the operation of the physical processes under investigation, given some set of external boundary and initial conditions. Because each element or node within the model domain must be assigned a set of properties to represent the variables within the numerical approximation of the process, those properties must be known at each relevant point in space. characterization of a geologic site, such as at Yucca Mountain. Because descriptive characterization is limited both by access (particularly to the subsurface) and by the availability of resources, that description is necessarily incomplete. Therefore, the exhaustive description of a site for purposes of numerical physical-process modeling requires the prior assumption of some type of conceptual model for the site, which is then implemented to assign the values of the necessary properties and other variables at every point in space

THREE-DIMENSIONAL STROCHASTIC ROCK-PROPERTY AND UNCERTAINTY MODELS FOR YUCCA MOUNTAIN, NEVADA

Licensing of Yucca Mountain as a geologic disposal site for high-level nuclear waste will require quantitative predictions of the waste-isolation performance of the rocks that form Yucca Mountain and of the engineered barrier system for an extended period of time into the future. These predictions will require the use of numerical modeling in an attempt to capture the essence of highly complex physical processes, such as ground-water flow and the transport of potential radionuclide contaminants under both unsaturated and saturated conditions. Additional numerical modeling will be required to demonstrate that a mined geologic repository can be constructed safely within the rocks of Yucca Mountain, and that the underground openings will remain stable in the longer term when affected by the thermal pulse of the emplaced waste forms. A fundamental principle involved in the numerical representation of real-world physical processes is that the properties of the modeled domain that are important to that representation must be known ''exhaustively''. Standard procedure in virtually all numerical physical-process modeling is to discretize the model volume into a (large) number of individual elements or grid nodes, assign the necessary attributes to each element or node, and then apply one or more sets of mathematical expressions that are believed to represent the operation of the physical processes under investigation, given some set of external boundary and initial conditions. Because each element or node within the model domain must be assigned a set of properties to represent the variables within the numerical approximation of the process, those properties must be known at each relevant point in space. characterization of a geologic site, such as at Yucca Mountain. Because descriptive characterization is limited both by access (particularly to the subsurface) and by the availability of resources, that description is necessarily incomplete. Therefore, the exhaustive description of a site for purposes of numerical physical-process modeling requires the prior assumption of some type of conceptual model for the site, which is then implemented to assign the values of the necessary properties and other variables at every point in space

Physical and hydrologic properties of rock outcrop samples at Yucca Mountain, Nevada

Studies are underway at Yucca Mountain to characterize physical and hydrologic conditions for a potential high-level radioactive waste repository. Site characterization requires the development of three- dimensional models describing hydrogeologic units in terms of inputs for numerical models. It is also important to understand the spatial distribution of these properties, vertical and horizontally, in order to estimate values at unmeasured points. Deterministic processes of volcanism caused the initial formation of the rock units, and it is useful to be able to correlate rock properties with the more qualitative descriptions of rock lithology that occur on a larger scale. Preliminary data were collected to develop methods and evaluate spatial relations to determine sampling frequency. In addition, a data base was developed to provide some of the parameters needed for preliminary flow-modeling exercises. Surface transects of rock outcrops facilitated rapid collection of closely spaced samples of all units exposed at and around Yucca Mountain. This report presents the data collected, descriptive statistics for various units, preliminary hydrogeologic units, and analyses of porosity compared with flow properties