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Progress in Deep Geologic Disposal Safety Assessment in the U.S. since 2010

Mariner, Paul M.; Connolly, Laura A.; Cunningham, Leigh C.; Debusschere, Bert D.; Dobson, David C.; Frederick, Jennifer M.; Hammond, Glenn E.; Jordan, Spencer H.; LaForce, Tara; Nole, Michael A.; Park, Heeho D.; Perry, Frank V.; Rogers, Ralph D.; Seidl, Daniel T.; Sevougian, Stephen D.; Stein, Emily S.; Swift, Peter N.; Swiler, Laura P.; Vo, Jonathan V.; Wallace, Michael G.

Abstract not provided.

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TYPE Other Report YEAR 2019
OSTIDOI

Using Bayesian Networks for Sensitivity Analysis of Complex Biogeochemical Models

Water Resources Research

Dai, Heng; Chen, Xingyuan; Ye, Ming; Song, Xuehang; Hammond, Glenn E.; Hu, Bill; Zachara, John M.

Sensitivity analysis is a vital tool in numerical modeling to identify important parameters and processes that contribute to the overall uncertainty in model outputs. We developed a new sensitivity analysis method to quantify the relative importance of uncertain model processes that contain multiple uncertain parameters. The method is based on the concepts of Bayesian networks (BNs) to account for complex hierarchical uncertainty structure of a model system. We derived a new set of sensitivity indices using the methodology of variance-based global sensitivity analysis with the Bayesian inference. The framework is capable of representing the detailed uncertainty information of a complex model system using BNs and affords flexible grouping of different uncertain inputs given their characteristics and dependency structures. We have implemented the method on a real-world biogeochemical model at the groundwater-surface water interface within the Hanford Site's 300 Area. The uncertainty sources of the model were first grouped into forcing scenario and three different processes based on our understanding of the complex system. The sensitivity analysis results indicate that both the reactive transport and groundwater flow processes are important sources of uncertainty for carbon-consumption predictions. Within the groundwater flow process, the structure of geological formations is more important than the permeability heterogeneity within a given geological formation. Our new sensitivity analysis framework based on BNs offers substantial flexibility for investigating the importance of combinations of interacting uncertainty sources in a hierarchical order, and it is expected to be applicable to a wide range of multiphysics models for complex systems.

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TYPE Journal Article YEAR 2019
ScopusOSTIDOI

Re-evaluation of U.S. DOE R&D efforts for generic deep geologic repositories - Roadmap update

International High-Level Radioactive Waste Management 2019, IHLRWM 2019

Sevougian, S.D.; Hammond, Glenn E.; Mariner, Paul M.; MacKinnon, R.J.; Swift, Peter N.; Rogers, R.D.; Dobson, D.C.; Tynan, M.C.

R&D addressing the disposal of commercial spent nuclear fuel in the U.S. is currently generic (i.e., “non-site-specific”) in scope. However, to prepare for the eventuality of a repository siting process, the former Used Fuel Disposition (UFD) Campaign of the Nuclear Energy (NE) Office of the U.S. DOE formulated an R&D Roadmap in 2012 outlining generic R&D activities and their priorities appropriate for developing safety cases and associated performance assessment (PA) models for deep geologic repositories in several potential host-rock environments in the contiguous United States. This 2012 UFD Roadmap identified the importance of re-evaluating priorities in future years as knowledge is gained from the DOE's ongoing R&D activities. Since 2012, significant knowledge has been gained from these activities through R&D in the U.S. and via international collaborations, especially with countries that operate underground research laboratories (URLs). The 2019 R&D Roadmap Update, introduced here, summarizes the progress of ongoing R&D activities, re-assesses R&D priorities, and identifies new activities of high priority, such as R&D on disposal of DPCs (dual purpose canisters), which now contain a significant fraction of the Nation's spent fuel activity.

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TYPE Conference Poster YEAR 2019
ScopusOSTI

Benchmarking and QA testing in PFLOTRAN

International High-Level Radioactive Waste Management 2019, IHLRWM 2019

LaForce, Tara; Frederick, Jennifer M.; Hammond, Glenn E.; Stein, Emily S.; Mariner, Paul E.

PFLOTRAN is well-established in single-phase reactive transport problems, and current research is expanding its visibility and capability in two-phase subsurface problems. A critical part of the development of simulation software is quality assurance (QA). The purpose of the present work is QA testing to verify the correct implementation and accuracy of two-phase flow models in PFLOTRAN. An important early step in QA is to verify the code against exact solutions from the literature. In this work a series of QA tests on models that have known analytical solutions are conducted using PFLOTRAN. In each case the simulated saturation profile is rigorously shown to converge to the exact analytical solution. These results verify the accuracy of PFLOTRAN for use in a wide variety of two-phase modelling problems with a high degree of nonlinearity in the interaction between phase behavior and fluid flow.

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TYPE Conference Poster YEAR 2019
ScopusOSTI

Advances in Geologic Disposal Safety Assessment and an Unsaturated Alluvium Reference Case

Mariner, Paul M.; Stein, Emily S.; Cunningham, Leigh C.; Frederick, Jennifer M.; Hammond, Glenn E.; Lowry, Thomas S.; Basurto, Eduardo B.

The Spent Fuel and Waste Science and Technology (SFWST) Campaign of the U.S. Depat ment of Energy (DOE) Office of Nuclear Energy (NE), Office of Fuel Cycle Technology (OFCT) is conducting research and development (R&D) on geologic disposal of spent nuclear fuel (SNF) and high level nuclear waste (HLW). Two high priorities for SFWST disposal R&D are design concept development and disposal system modeling (DOE 2011, Table 6). These priorities are directly addressed in the SFWST Geologic Disposal Safety Assessment (GDSA) work package, which is charged with developing a disposal system modeling and analysis capability for evaluating disposal system performance for nuclear waste in geologic media. This report describes specific GDSA activities in fiscal year 2018 (FY 2018) toward the development of GDSA Framework, an enhanced disposal system modeling and analysis capability for geologic disposal of nuclear waste. GDSA Framework employs the PFLOTRAN thermal-hydrologic-chemical multiphysics code (Hammond et al. 2011a; Lichtner and Hammond 2012) and the Dakota uncertainty sampling and propagation code (Adams et al. 2012; Adams et al. 2013). Each code is designed for massivelyparallel processing in a high-performance computing (HPC) environment. Multi-physics representations in PFLOTRAN are used to simulate various coupled processes including heat flow, fluid flow, waste dissolution, radionuclide release, radionuclide decay and ingrowth, precipitation and dissolution of secondary phases, and radionuclide transport through engineered barriers and natural geologic barriers to the biosphere. Dakota is used to generate sets of representative realizations and to analyze parameter sensitivity.

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TYPE Other Report YEAR 2018
OSTIDOI

Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream-aquifer-land interactions (CP v1.0)

Geoscientific Model Development

Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater-river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater-river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater-river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion into the subsurface in response to an elevated river stage that increased soil moisture for evapotranspiration and suppressed available energy for sensible heat in the warm season. The coupled model developed in this study can be used for improving mechanistic understanding of ecosystem functioning and biogeochemical cycling along river corridors under historical and future hydroclimatic changes. The dataset presented in this study can also serve as a good benchmarking case for testing other integrated models.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI

Advances in Geologic Disposal System Modeling and Shale Reference Cases

Mariner, Paul M.; Stein, Emily S.; Frederick, Jennifer M.; Sevougian, Stephen D.; Hammond, Glenn E.

The Spent Fuel and Waste Science and Technology (SFWST) Campaign of the U.S. Department of Energy (DOE) Office of Nuclear Energy (NE), Office of Fuel Cycle Technology (OFCT) is conducting research and development (R&D) on geologic disposal of spent nuclear fuel (SNF) and high level nuclear waste (HLW). Two high priorities for SFWST disposal R&D are design concept development and disposal system modeling (DOE 2011, Table 6). These priorities are directly addressed in the SFWST Generic Disposal Systems Analysis (GDSA) work package, which is charged with developing a disposal system modeling and analysis capability for evaluating disposal system performance for nuclear waste in geologic media (e.g., salt, granite, shale, and deep borehole disposal).

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TYPE Other Report YEAR 2017
OSTIDOI
Results 1–50 of 144
Results 1–50 of 144