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

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Draft pp. 3.1.24, 33 and 235<br />

Issue<br />

238<br />

GEOLOGIC CONSIDERATIONS<br />

Several commenters expressed concern that it may not be realistic to depend on the<br />

"self-healing behavior" (<strong>of</strong> salt) to produce an impermeable seal around the repository. The<br />

design should consider worse case behavior (i.e., the opening <strong>of</strong> thermally or mechanically<br />

induced fractures around the repository to water flow from an overlying aquifer). (208-NRC,<br />

218-DOI)<br />

Response<br />

There is an impermeable boundary or sheath around the exterior <strong>of</strong> a salt dome that has<br />

existed for 20 or more million years. The need to produce an impermeable seal should only<br />

exist if construction or testing breaks this. Because <strong>of</strong> the known plastic behavior and<br />

"self-healing" properties <strong>of</strong> the salt domes at depth and the small size <strong>of</strong> a repository com-<br />

pared to a salt dome, it seems unlikely that fractures would propagate (from repository con-<br />

struction or operation) through several hundred meters <strong>of</strong> salt and remain open conduits for<br />

water transport.<br />

Draft p. 3.1.26<br />

Issue<br />

(113-EPA)<br />

Response<br />

How will the list <strong>of</strong> problems in the draft, with only speculative solutions be handled?<br />

The problems cited are those in predicting future human activity and no specific method<br />

<strong>of</strong> handling this problem is proposed. For the accident release scenarios based on human<br />

activity, it has been assumed that the intrusion occurred. The scenario is then analyzed<br />

under the assumed conditions without assigning a probability to the human activity. For<br />

certain types <strong>of</strong> human activity, such as resource exploration, the site selection process<br />

would reduce the chances <strong>of</strong> human intrusion by selecting areas where the resource potential<br />

is as low as possible.<br />

Draft pp. 3.1.26-28<br />

Issue<br />

The section on Deficiencies in Data Base is much to general and non-specific. For<br />

example, it fails .to mention lack <strong>of</strong> data on long-term shaft and borehole sealing; large-<br />

scale sorption measurements; long-term verification <strong>of</strong> models; large scale dispersivity<br />

measurements; and other deficiencies. (218-DOI)

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