Probability Distribution for Flowing Interval Spacing
Fracture spacing is a key hydrologic parameter in analyses of matrix diffusion. Although the individual fractures that transmit flow in the saturated zone (SZ) cannot be identified directly, it is possible to determine the fractured zones that transmit flow from flow meter survey observations. The fractured zones that transmit flow as identified through borehole flow meter surveys have been defined in this report as flowing intervals. The flowing interval spacing is measured between the midpoints of each flowing interval. The determination of flowing interval spacing is important because the flowing interval spacing parameter is a key hydrologic parameter in SZ transport modeling, which impacts the extent of matrix diffusion in the SZ volcanic matrix. The output of this report is input to the ''Saturated Zone Flow and Transport Model Abstraction'' (BSC 2004 [DIRS 170042]). Specifically, the analysis of data and development of a data distribution reported herein is used to develop the uncertainty distribution for the flowing interval spacing parameter for the SZ transport abstraction model. Figure 1-1 shows the relationship of this report to other model reports that also pertain to flow and transport in the SZ. Figure 1-1 also shows the flow of key information among the SZ reports. It should be noted that Figure 1-1 does not contain a complete representation of the data and parameter inputs and outputs of all SZ reports, nor does it show inputs external to this suite of SZ reports. Use of the developed flowing interval spacing probability distribution is subject to the limitations of the assumptions discussed in Sections 5 and 6 of this analysis report. The number of fractures in a flowing interval is not known. Therefore, the flowing intervals are assumed to be composed of one flowing zone in the transport simulations. This analysis may overestimate the flowing interval spacing because the number of fractures that contribute to a flowing interval cannot be determined from the data. In terms of repository performance, the results of this analysis may underestimate the effect of matrix diffusion processes in SZ transport models. Underestimation of matrix diffusion in the transport modeling would result in more rapid simulated migration of radionuclide mass to the accessible environment and correspondingly higher simulated dose to the reasonably maximally exposed individual in the Total System Performance Assessment-License Application (TSPA-LA) analyses. The flowing interval spacing is appropriate for use in the SZ site-scale transport abstraction model because the 500 m grid block size in the numerical transport model is more than an order of magnitude larger than the expected flowing interval spacing (BSC 2004 [DIRS 170042], Section 6.3.1). Therefore, the use of the developed flowing interval spacing parameter is limited to a numerical grid spacing that is at least an order of magnitude greater than the average flowing interval spacing to ensure a reasonable description of transport behavior in a grid. This analysis report supports several features, events, and processes (FEPs) and contributes to the characterization of the SZ as a natural barrier, which provides evidence related to the capability of the SZ to delay movement of radionuclides through the SZ to the accessible environment.
- Research Organization:
- Yucca Mountain Project, Las Vegas, NV (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC28-01RW12101
- OSTI ID:
- 838653
- Report Number(s):
- ANL-NBS-MD-000003, REV 01; DOC.20040923.0003, DC41516; TRN: US0502833
- Resource Relation:
- Other Information: PBD: 22 Sep 2004
- Country of Publication:
- United States
- Language:
- English
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