Publications

There is a growing recognition internationally of the need to demonstrate comprehensiveness in order to build confidence in performance assessments (PAs) for radioactive waste disposal projects. This has resulted in a number of methodologies being developed to formalize the process of defining and documenting the decision basis that underlies a PA. Such methodologies include process influence diagrams and the rock engineering system (RES) matrix. However, these methodologies focus mainly on the conceptualization of the disposal system and do not provide a ready framework to document the decisions behind the model development and parameterization of the PA system. The Performance Assessment Support System (PASS) is a flexible electronic tool designed to increase the transparency and traceability of decision making in the entire PA process. An application of PASS has been developed for the Waste Isolation Pilot Plant (WIPP) where it forms an important component of Desk Top PA, a PC-based PA computational environment under development at Sandia National Laboratories to document, plan, and support management decisions and to assess performance for the WIPP recertification process. This desk-top PA environment is also aimed at providing scientifically-based decision support for assessing the performance of nuclear and hazardous waste management and environmental clean-up systems.

The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface-based and underground testing. Analyses have been performed to design site characterization activities with minimal impact on the ability of the site to isolate waste, and on tests performed as part of the characterization process. One activity of site characterization is the construction of an Exploratory Studies Facility, which may include underground shafts, drifts, and ramps, and the accompanying ponds used for the storage of sewage water and muck water removed from construction operations. The information in this report pertains to the two-dimensional numerical calculations modelling the movement of sewage and settling pond water, and the potential effects of that water on repository performance and underground experiments. This document contains information that has been used in preparing Appendix I of the Exploratory Studies Facility Design Requirements document (ESF DR) for the Yucca Mountain Site Characterization Project.

The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface-based and underground testing. Analyses have been performed to design site characterization activities with minimal impact on the ability of the site to isolate waste, and on tests performed as part of the characterization process. One activity of site characterization is the construction of an Exploratory Studies Facility, consisting of underground shafts, drifts, and ramps, and the accompanying surface pad facility and roads. The information in this report addresses the following topics: (1) a discussion of the potential effects of surface construction water on repository-performance, and on surface and underground experiments; (2) one-dimensional numerical calculations predicting the maximum allowable amount of water that may infiltrate the surface of the mountain without affecting repository performance; and (3) two-dimensional numerical calculations of the movement of that amount of surface water and how the water may affect repository performance and experiments. The results contained herein should be used with other site data and scientific/engineering judgement in determining controls on water usage at Yucca Mountain. This document contains information that has been used in preparing Appendix I of the Exploratory Studies Facility Design Requirements document for the Yucca Mountain Site Characterization Project.

The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface-based and underground testing. Analyses have been performed to design site characterization activities with minimal impact on the ability of the site to isolate waste, and on tests performed as part of the characterization process. One activity of site characterization is the construction of an Exploratory Studies Facility, for which many design options are being considered, including shafts, drifts, and ramps. The information in this report pertains to: (1) engineering calculations of the potential distribution of residual water from constructing the shafts and drifts; (2) numerical calculations predicting the movement of residual construction water from the shaft and drift walls into the rock; and (3) numerical calculations of the movement of residual water and how the movement is affected by ventilation. This document contains information that has been used in preparing Appendix 1 of the Exploratory Studies Facility Design Requirements document for the Yucca Mountain Project.

The near field surrounding buried waste in the proposed high level nuclear waste repository in Yucca Mountain, Nye County, Nevada, is a region where strongly heat driven processes can exist. These strongly heat driven processes further complicate an already very difficult problem, i.e,. predicting groundwater flow and chemical transport through unsaturated fractured, heterogeneous porous media. The coupling between fluid flow and heat emanation is central to understanding these strongly heat driven processes. Although it is important that all of couplings be investigated, the intent of this paper is to discuss the mathematical models and associated computer codes that can be used in investigating the coupled heat emanation and fluid flow in unsaturated porous media. The information in this paper should be useful to those studying these phenomena, validating these models, or investigating the coupling of fluid flow and heat emanation with the other phenomena. The codes implementing these models are commonly referred to as nonisothermal two-phase flow codes. 5 refs., 4 tabs.