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Title: Pore Connectivity, Episodic Flow, and Unsaturated Diffusion in Fractured Tuff

We use an integrated approach consisting of experiments and complementary pore-scale network modeling to investigate the occurrence of sparsely connected pore spaces in rock matrices at Yucca Mountain, Nevada, and its implication to matrix diffusion. Imbibition results indicate that pore spaces in devitrified tuff are not well-connected, and that this lack of connectivity is further compounded by episodic flow in fractured devitrified tuff with low matrix permeability. A rigorous methodology for investigating chemical transport in fractured rock under episodic conditions, employing a suite of both sorbing and non-sorbing tracers (including radionuclides U-235, Np-237, and Pu-242), has been developed and implemented. In addition, gas diffusion and synchrotron microtomography techniques have been under development to examine the scaling issues of diffusion and pore connectivity. Preliminary results from experiments and modeling work are presented in this paper, in order to reexamine our understanding of matrix diffusion and to evaluate the impact on diffusive radionuclide retardation of episodic fracture flow and low pore connectivity.
Authors:
; ; ;
Publication Date:
OSTI Identifier:
893980
Report Number(s):
UCRL-PROC-218551
TRN: US0700038
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: 2006 International High Level Radioactive Waste Management Conference, Las Vegas, NV, United States, Apr 30 - May 04, 2006
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 43 PARTICLE ACCELERATORS; 58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; DIFFUSION; FRACTURES; MATRICES; PERMEABILITY; RADIOACTIVE WASTE MANAGEMENT; RADIOISOTOPES; SIMULATION; SYNCHROTRONS; TRANSPORT; TUFF; YUCCA MOUNTAIN