OVERVIEW OF MODELING APPROACHES FOR ASSESSING NATURAL SYSTEM PERFORMANCE OF THE HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY AT YUCCA MOUNTAIN, NEVADA
For two decades, extensive hydrologic investigations have been conducted for geologic disposal of high-level radioactive waste in fractured volcanic tuffs at Yucca Mountain, Nevada. Extensive field and laboratory geologic, hydrologic, and geochemical testing has provided a large amount of data for developing the conceptual understanding of these processes and parameters for quantifying these processes. A suite of sophisticated numerical models has been developed to assess the long-term performance of the natural barrier of unsaturated zone (UZ) and saturated zone (SZ) to flow of groundwater and transport of radionuclides released from the repository. This work focuses on characterizing surface and subsurface processes of climate change, infiltration, percolation in the UZ and groundwater flow in the SZ, as well as on predicting hydrologic responses of the natural system to the emplacement of waste packages in drifts, including seepage of water into emplacement drifts and radionuclide transport in the UZ and SZ. These models are then abstracted into a total system performance assessment (TSPA) model. The TSPA integrates these natural attributes with features of engineered systems, and through systematic stochastic analyses involving Monte Carlo simulations, predicts the dose consequences and groundwater concentrations for at least 10,000 years for various future climate conditions, waste types, release scenarios, and transport pathways. The TSPA predictions demonstrate compliance with postclosure individual and groundwater protection standards in the license application for the repository. This presentation provides an overview of the development and use of these natural-system models, including the infiltration model, the site-scale UZ flow model, the seepage calibration and abstraction models, the UZ radionuclide transport and abstraction models, and the site-scale SZ flow and transport models. It describes the approaches used in the design and construct of these models, summarizes the tests and experiments conducted to obtain key input data, and discusses lessons learned in the efforts to validate the models and the treatment of uncertainties in the TSPA.
- Research Organization:
- Yucca Mountain Project, Las Vegas, NV (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC08-91RW00134
- OSTI ID:
- 888869
- Resource Relation:
- Conference: 2006 Western Pacific Geophysics Meeting
- Country of Publication:
- United States
- Language:
- English
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