Management of Commercially Generated Radioactive Waste - U.S. ...

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Comment
Comment
Number Number
3.h.3 p. 3.1.5 3.h.7 p. 3.1.23
The definition of convection is incorrect. Convection signifies the It is stated.that interior drainage is a favorable hydrologic characteristic
transport of a contaminent by a moving fluid. Thermal differences may in selecting a burial site. An example given is the Great Basin of Nevada
produce fluid motions, and thermally driven convection must be considered and Utah. However, one characteristic of interior drainage is that during
in the analysis of a radioactive waste repository. The usual driving wet climatic periods they can become almost completely water-covered.
force for groundwater flow is the head gradient (where the head is due to This has happened in the recent geologic past in the Great Basin. Conse-
elevation and pressure). The velocity and direction of flow are. governed quences of the potential for such drastic changes in the surface and
by a combination of fluid properties, rock properties .and head gradients. subsurfaces water regime should be more carefully investigated before
asserting that interior drainage is favorable. Interior drainage is again
3.h.4 p. 3.1. favorably mentioned on page 3.1.27.
Line 2: To group geologic materials into two categories, either aquifers
or aquitards is misleading. A whole continuum of both permeability and 3.h.8 p. 3.1.8
porosity exists which can describe an aquifer (high permeability and high Because of the complexity and nature of deep geologic and hydrologic
porosity), aquitard (low permeability), and aquiclude (very low permea- Investigations, simple analysis using permeability, porosity, and hydraulic
bility but may contain appreciable porosity) also known as an Impervious gradients are not sufficient. Appropriate parameters for evaluation of
horizon or an aquifuge (very low permeability and very low porosity). The hydrologic regimes are:
local site conditions generally determine how you would classify the fluid properties
hydrostratigraphic unit since these terms are often relative, density
compressibility
3.h.5 p. 3.1.6 thermal.expansion/heat capacity
Line 4: A discussion is needed of piezometric levels, leakage between viscosity
confined, unconfined, and various combination hydrostratigraphic units, matrix properties
and how a unit may change from a phreatic, to a confined, leaky, or artesian longitudinal and transverse dispersities
aquifer. vertical permeability
density
3.h.6 . 3.1.6 compressibility
A discussion of steady state versus transient flow conditions and their storage and leakage factors along with permeability and porosity.
implications on hydrostratigraphic unit storage is needed. The variability
of parameters governed by the matrix plus secondary features such In addition one needs to assess the difficulty in determining these paramas
faults, joints, structure, and alterations also need discussion. . eters, their uncertainties and extent to which and time required for a
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hydrologic model to be validated and calibrated. The above items may
contribute significantly to uncertainty in predicting future safe perfor-
mance. They could also impact the data for initial emplacement.