James E. Houseworth

Transport modeling in performance assessments for the Yucca Mountain disposal system for spent nuclear fuel and high-level radioactive waste.

This paper summarizes modeling of radionuclide transport in the unsaturated and saturated zone conducted between 1984 and 2008 to evaluate feasibility, viability, and assess compliance of a repository for spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. One dimensional (1-D) transport for a single porosity media without lateral dispersion was solved in both the saturated zone (SZ) and unsaturated zone (UZ) for the first assessment in 1984 but progressed to a dual-porosity formulation for the UZ in the second assessment in 1991. By the time of the viability assessment, a dual-permeability transport formulation was used in the UZ. With the planned switch to a dose performance measure, individual dose from a drinking water pathway was evaluated for the third assessment in 1993 and from numerous pathways for the viability assessment in 1998 and thereafter. Stream tubes for transport in the SZ were initially developed manually but progressed to particle tracking in 1991. For the viability assessment, particle tracking was used to solve the transport equations in the 3-D UZ and SZ flow fields. To facilitate calculations, the convolution method was also used in the SZ for the viability assessment. For the site recommendation in 2001 and licensing compliance analysis in 2008, the 3-D transport results of the SZ were combined with 1-D transport results, which evaluated decay of radionuclides, in order to evaluate compliance with groundwater protection requirements. Uncertainty in flow within the unsaturated and saturated zone was generally important to explaining the spread in the individual dose performance measure.

Hydro-mechanical model for wetting/drying and fracture development in geomaterials

This paper presents a modeling approach for studying hydro-mechanical coupled processes, including fracture development, within geological formations. This is accomplished through the novel linking of two codes: TOUGH2, which is a widely used simulator of subsurface multiphase flow based on the finite volume method; and an implementation of the Rigid-Body-Spring Network (RBSN) method, which provides a discrete (lattice) representation of material elasticity and fracture development. The modeling approach is facilitated by a Voronoi-based discretization technique, capable of representing discrete fracture networks. The TOUGH-RBSN simulator is intended to predict fracture evolution, as well as mass transport through permeable media, under dynamically changing hydrologic and mechanical conditions. Numerical results are compared with those of two independent studies involving hydro-mechanical coupling: (1) numerical modeling of swelling stress development in bentonite; and (2) experimental study of desiccation cracking in a mining waste. The comparisons show good agreement with respect to moisture content, stress development with changes in pore pressure, and time to crack initiation. The observed relationship between material thickness and crack patterns (e.g., mean spacing of cracks) is captured by the proposed modeling approach.

Sensitivity Analysis Of Hydrological Parameters In Modeling FlowAnd Transport In The Unsaturated Zone Of Yucca Mountain

The unsaturated fractured volcanic deposits at Yucca Mountain in Nevada, USA, have been intensively investigated as a possible repository site for storing high-level radioactive waste. Field studies at the site have revealed that there exist large variabilities in hydrological parameters over the spatial domain of the mountain. Systematic analyses of hydrological parameters using a site-scale three-dimensional unsaturated zone (UZ) flow model have been undertaken. The main objective of the sensitivity analyses was to evaluate the effects of uncertainties in hydrologic parameters on modeled UZ flow and contaminant transport results. Sensitivity analyses were carried out relative to fracture and matrix permeability and capillary strength (van Genuchten α) through variation of these parameter values by one standard deviation from the base-case values. The parameter variation resulted in eight parameter sets. Modeling results for the eight UZ flow sensitivity cases have been compared with field observed data and simulation results from the base-case model. The effects of parameter uncertainties on the flow fields were evaluated through comparison of results for flow and transport. In general, this study shows that uncertainties in matrix parameters cause larger uncertainty in simulated moisture flux than corresponding uncertainties in fracture properties for unsaturated flow through heterogeneous fractured rock.RésuméConsidérée comme un site potentiel pour le stockage de déchets hautement radioactifs, la zone non saturée et fracturée de la montagne Yucca dans le Nevada, USA, a fait l’objet de nombreuses études. Des investigations de terrain au niveau du site ont révélé l’existence d’une importante variabilité spatiale pour les paramètres hydrogéologiques. Des analyses systématiques de ces paramètres ont été effectuées en utilisant un modèle d’écoulement de la zone non saturée (ZNS), en 3-D et à l’échelle du site. Le principal objectif des analyses de sensibilité était d’évaluer les effets engendrés par des incertitudes au niveau des paramètres hydrogéologiques, sur les résultats de la modélisation d’écoulement et de transport de polluants dans la ZNS. Les analyses de sensibilité ont été réalisées en fonction des perméabilités de fracture et de matrice et de la force capillaire (van Genuchten α), à travers la variation des valeurs de ces paramètres et un écart type par rapport aux valeurs les plus probables. La démarche a conduit à huit séries de paramètres. Les résultats de la modélisation pour les huit cas d’écoulement dans la ZNS ont été comparés avec des données observées sur le terrain et les résultats de simulations obtenus avec le modèle aux conditions initiales. Les effets sur les champs d’écoulement des incertitudes sur les paramètres ont été évalués en comparant les résultats pour l’écoulement et le transport. En général, cette étude montre que pour un écoulement insaturé à travers un milieu hétérogène et fracturé, les incertitudes sur les paramètres de la matrice entraînent des erreurs plus importantes sur le flux d’humidité simulé que des incertitudes équivalentes sur les propriétés de fracture.ResumenSe ha investigado intensivamente la zona fracturada no saturada de Montaña Yuca en Nevada, Estados Unidos de América, como un sitio potencial para el almacenamiento de residuos radioactivos de alto nivel. Los estudios de campo del sitio han mostrado que existe una gran variabilidad en los parámetros hidrológicos en todo el ambiente espacial de la montaña. Se ha realizado análisis sistemático de parámetros hidrológicos usando un modelo 3-D, a escala del sitio, de flujo (UZ) de la zona no saturada. El principal objetivo del análisis de sensibilidad fue evaluar los efectos de las incertidumbres en los parámetros hidrológicos en el modelo UZ y los resultados del transporte de contaminantes. Los análisis de sensibilidad se llevaron a cabo en relación con la permeabilidad intersticial y de fracturas y la fortaleza de capilaridad (α de van Genuchten), haciendo variar los valores de esos parámetros mediante una desviación standard a partir de los valores básicos del caso. La variación de parámetros dio por resultado grupos de ocho parámetros. Los resultados del modelo para los ocho casos de sensibilidad de flujo UZ se han comparado con datos de campo y los resultados de la simulación del modelo de caso básico. Se evaluaron los efectos de las incertidumbres de los parámetros en los campos de flujo mediante comparación de resultados para flujo y transporte. En general, este estudio muestra que los resultados de las incertidumbres en los parámetros de la matriz causan mayor incertidumbre en la simulación del flujo de humedad que las correspondientes incertidumbres en propiedades de fracturas para flujo no saturado a través de roca fracturada heterogénea.

Overview of Total System Model Used for the 2008 Performance Assessment for the Proposed High-Level Radioactive Waste Repository at Yucca Mountain Nevada.

Abstract A summary is presented for the total system model used to represent physical processes associated with the seven scenario classes (i.e., nominal conditions, early waste package (WP) failure, early drip shield (DS) failure, igneous intrusive events, igneous eruptive events, seismic ground motion events and seismic fault displacement events) considered in the 2008 performance assessment for the proposed repository for high-level radioactive waste at Yucca Mountain, Nevada. The total system model estimates dose to an exposed individual resulting from radionuclide movement through the repository system and biosphere. Components of the total system model described in this presentation include models for (i) climate analysis, (ii) land surface infiltration and associated unsaturated zone flow, (iii) multi-scale thermal hydrology and engineered barrier system (EBS) thermal–hydrologic environment, (iv) EBS physical and chemical environment, (v) WP and DS degradation, (vi) drift seepage and drift wall condensation, (vii) waste form degradation and mobilization, (viii) water and radionuclide movement in the EBS and underlying unsaturated and saturated zones, (ix) radionuclide movement in the biosphere and resultant human exposure, and (x) processes specific to early WP and DS failures, intrusive and eruptive igneous events, and seismic ground motion and fault displacement events.

Sensitivity Analysis Of Hydrological Parameters In Modeling Flow And Transport In The Unsaturated Zone Of Yucca Mountain

Sensitivity Analysis of Hydrological Parameters in Modeling Flow and Transport in the Unsaturated Zone of Yucca Mountain Keni Zhang, Yu-Shu Wu, and James E. Houseworth Earth Sciences Division Lawrence Berkeley National Laboratory Berkeley, CA 94720, USA Abstract The unsaturated fractured volcanic deposits at Yucca Mountain have been intensively investigated as a possible repository site for storing high-level radioactive waste. Field studies at the site have revealed that there exist large variabilities in hydrological parameters over the spatial domain of the mountain. This paper reports on a systematic analysis of hydrological parameters using the site-scale 3-D unsaturated zone (UZ) flow model. The objectives of the sensitivity analyses are to evaluate the effects of uncertainties in hydrologic parameters on modeled UZ flow and contaminant transport results. Sensitivity analyses are carried out relative to fracture and matrix permeability and capillary strength (van Genuchten α), through variation of these parameter values by one standard deviation from the base-case values. The parameter variation results in eight parameter sets. Modeling results for the eight UZ flow sensitivity cases have been compared with field observed data and simulation results from the base-case model. The effects of parameter uncertainties on the flow fields are discussed and evaluated through comparison of results for flow and transport. In general, this study shows that uncertainties in matrix parameters cause larger uncertainty in simulated moisture flux than corresponding uncertainties in fracture properties for unsaturated flow through heterogeneous fractured rock. Keywords: unsaturated zone, fractured rocks, numerical modeling, hydraulic properties, Yucca Mountain

Investigation of Coupled THMC Processes and Reactive Transport: FY14 Progress

Author(s): Rutqvist, Jonny; Davis, James; Zheng, Liange; Vilarrasa, Victor; Houseworth, James; Birkholzer, Jens

Leakage Risk Assessment for a Potential CO2 Storage Project in Saskatchewan, Canada

LBNL-4915E Certification Framework Leakage Risk Assessment for a Potential CO 2 Storage Project in Saskatchewan, Canada James E. Houseworth 1 , Curtis M. Oldenburg 1 , Alberto Mazzoldi 1 , Abhishek K. Gupta 3 , Jean-Philippe Nicot 2 , and Steven L. Bryant 3 , Lawrence Berkeley National Laboratory, Earth Sciences Division, 90-1116 Berkeley CA 94720 jehouseworth@lbl.gov cmoldenburg@lbl.gov amazzoldi@lbl.gov Bureau of Economic Geology, University of Texas, University Station, Box X Austin, Texas 78713-8924 jp.nicot@beg.utexas.edu CPGE, University of Texas, Austin, 1 University Station C0300 Austin, TX 78712-0228 abhishek.k.gupta@mail.utexas.edu steven_bryant@mail.utexas.edu May 11, 2011 Acknowledgments: We thank Preston Jordon for providing a careful review of this report. This work was supported in part by the Petroleum Technology Research Centre, Regina, Saskatchewan, Canada, and by Lawrence Berkeley National Laboratory under Department of Energy Contract No. DE-AC02-05CH11231. Additional support comes from the University of Texas, Austin, and the Bureau of Economic Geology, University of Texas.

An Independent Scientific Assessment of Well Stimulation in California Volume II

In 2013, the California Legislature passed Senate Bill 4 (SB 4), setting the framework for regulation of well stimulation technologies in California, including hydraulic fracturing. SB 4 also requires the California Natural Resources Agency to conduct an independent scientific study of well stimulation technologies in California to assess current and potential future practices, including the likelihood that well stimulation technologies could enable extensive new petroleum production in the state, evaluate the impacts of well stimulation technologies and the gaps in data that preclude this understanding, identify risks associated with current practices, and identify alternative practices which might limit these risks. The study is issued in three volumes. This document, Volume I, provides the factual basis describing well stimulation technologies, how and where operators deploy these technologies for oil and gas production in California, and where they might enable production in the future. Volume II discusses how well stimulation affects water, the atmosphere, seismic activity, wildlife and vegetation, traffic, light and noise levels; it will also explore human health hazards, and identify data gaps and alternative practices. Volume III presents case studies to assess environmental issues and qualitative

Investigation of Coupled Processes and Impact of High Temperature Limits in Argillite Rock

Author(s): Zheng, Liange; Rutqvist, Jonny; Steefel, Carl; Kim, Kunhwi; Chen, Fei; Vilarrasa, Victor; Nakagawa, Seiji; Houseworth, James; Birkholzer, Jens