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

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Response<br />

223<br />

GEOLOGIC CONSIDERATIONS<br />

The purpose in this section is to describe the physical properties <strong>of</strong> the four speci-<br />

fied media -- especially as they relate to isolation (or lack <strong>of</strong> it) <strong>of</strong> the waste. Ground<br />

water is assumed to be the most likely agent for waste transport, should it occur. Joints<br />

and fractures are probably the most likely candidates for flow channels, given a supply <strong>of</strong><br />

water, the necessary gradients, etc., thus, the primary concern is with them. Thermal<br />

effects on existing joints and fractures are treated under Effects <strong>of</strong> Changes Induced by<br />

Emplacement <strong>of</strong> <strong>Waste</strong> (draft p. 3.1.34) and other places (e.g., draft p. 3.1.4). In-situ<br />

tests are specifically recommended for representative rock mass properties as opposed to<br />

laboratory test (draft p. 3.1.26).<br />

Draft p. 3.1.8<br />

Issue<br />

Because <strong>of</strong> the complexity and nature <strong>of</strong> deep geologic and hydrologic investigations,<br />

simple analysis using permeability, porosity and hydraulic gradients are not sufficient.<br />

Appropriate fluid and matrix parameters need to be determined; difficulties in determining<br />

them and the uncertainties should be discussed. (208-NRC)<br />

Response<br />

To thoroughly characterize a geologic and hydrologic setting and to model it would<br />

require a detailed knowledge <strong>of</strong> the site. This type <strong>of</strong> information would be collected<br />

during site investigation and testing. Simulation modeling would probably be used to pre-<br />

dict performance once a site had been selected and the information could be obtained. For<br />

a generic approach to repository siting, an overall geologic and hydrologic assessment must<br />

be made with less detail. As the site selection process is described, each stage or phase<br />

will add to the detail and depth <strong>of</strong> investigation.<br />

Draft p. 3.1.8<br />

Issue<br />

Response<br />

Salt domes may deform overlying strata without penetrating them. (208-NRC)<br />

The text has been changed (see Section B.6.1 <strong>of</strong> the final Statement).

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