Second progress report on pre-test calculations for the large block test Page: 3 of 127
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The U.S. Department of Energy's (DOE) Yucca Mountain Site Char-
acterization Project (YMP) is investigating the suitability of the Topopah
Spring tuff in the thick vadose zone at Yucca Mountain, Nevada, as a host
rock for permanent disposal of high-level radioactive waste. As part of the
YMP, a group of field tests, called the Large Block Test (LBT), will be con-
ducted on a large electrically heated block of Topopah Spring tuff, isolated
at Fran Ridge, Nevada Test Site. The block, which will be 3 x 3 m in hori-
zontal dimensions and about 4.4 m high, will be heated by electrical heaters
installed in five boreholes drilled in a horizontal plane 2.75 m below the top
of the block. The goals of the LBT are to gain information on the coupled
thermal-mechanical-hydrological-chemical processes that will be active in
the near-field environment of a repository; to provide field data for testing
and calibrating models; and to help in the development of measurement sys-
tems and techniques. In this second progress report, we present results of
the final set of numerical modeling calculations performed in support of the
LBT design. We use a three-dimensional conduction-only model to study
the thermal behavior of the system. The results include block temperatures
and heat fluxes across the surfaces. The results are applied primarily to
the design of guard heaters to enforce adiabatic conditions along the block
walls. Conduction-only runs are adequate to estimate the thermal behavior
of the system, because earlier calculations showed that heat transfer in the
block is expected to be dominated by conduction. In addition, conduction-
only runs can be made at substantially shorter execution times than full
hydrothermal runs. We also run a two-dimensional, hydrothermal, discrete
fracture model, with 200- m vertical fractures parallel to the heaters and
occurring at a uniform spacing of 30 cm. The results show the development
of distinct dryout and recondensation zones. The dryout zones are thickest
at the fractures and thinnest in the matrix midway between the fractures.
Block temperatures are unaffected by the location of the fractures.
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Lee, K.H. Second progress report on pre-test calculations for the large block test, report, November 15, 1995; California. (digital.library.unt.edu/ark:/67531/metadc666452/m1/3/: accessed January 18, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.