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

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Draft p. 3.1.5<br />

Issue<br />

220<br />

GEOLOGIC CONSIDERATIONS<br />

One commenter felt the section on Hydrology <strong>of</strong> the Host Rock is highly simplified; for<br />

more detailed explanations standard reference works should be cited. (208-NRC)<br />

Response<br />

This section is intended as an overall description <strong>of</strong> a general geologic consideration<br />

as it applies to waste isolation and site selection. Two references were added: Davis and<br />

DeWiest, and Walton (see reference list Appendix B).<br />

Draft. pp. 3.1.5, 6, 19<br />

Issue<br />

One area <strong>of</strong> serious concern which appears to be neglected is the effect <strong>of</strong> repository<br />

construction and operation and hydrologic barriers to long-term transport <strong>of</strong> radioactive<br />

materials from the repository. The following examples are cited:<br />

Construction is likely to increase hydraulic conductivity <strong>of</strong> the rock mass. There is<br />

no evidence presented in GEIS to show that such factors have been considered. This is a<br />

serious defficency.<br />

Rock fractures, joints and fissures are potential paths for increased ground-water<br />

flow. Mine construction and testing may induce local fracture conditions that may or may<br />

not be identified in sample permeability testing. However, the in-situ extent <strong>of</strong> fractures,<br />

joints, and fissures could produce increased ground-water flow in other than direct down-<br />

gradient directions. Have such factors been considered and what conclusions have been<br />

drawn? (208-NRC)<br />

Response<br />

These concerns are part <strong>of</strong> Effects <strong>of</strong> Changes Induced by Emplacement <strong>of</strong> <strong>Waste</strong> Excava-<br />

tion (draft p. 3.1.34). In general, these effects are discussed qualitatively as concerns<br />

and sources <strong>of</strong> possible effects. Most <strong>of</strong> the effects will depend on specific site condi-<br />

tions which will not be known until a site is selected and some testing/excavation has been<br />

conducted.<br />

For hard rocks, such as granite, permeability is difficult to measure in boreholes<br />

because the fractures intersecting the hole are most likely not representative <strong>of</strong> those in<br />

the larger rock mass. To obtain rock mass permeabilies a new test has been developed by<br />

Lawrence Berkeley Laboratory and is being applied in granite in the Stripa mine in Sweden.<br />

Briefly, the test involves isolating a section <strong>of</strong> mine drift, pumping in air <strong>of</strong> known hum-<br />

idity, and measuring the humidity <strong>of</strong> the discharged air. Also, pressures are measured in

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