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

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Draft p. 3.3.30<br />

Issue<br />

326<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

The fifth paragraph discusses the emplacement <strong>of</strong> a long column fuel canisters but<br />

fails to mention how crushing <strong>of</strong> the lower containers is prevented. The potential for<br />

crushing and the results there<strong>of</strong> during the period <strong>of</strong> emplacement should be treated. (58)<br />

Response<br />

The final Statement includes, in Section 6.1.1.2, a discussion <strong>of</strong> measures required to<br />

prevent crushing <strong>of</strong> the waste package.<br />

Draft p. 3.3.31<br />

Issue<br />

In the third paragraph it is indicated that leakage considerations from the deep hole<br />

repository are similar to those for a conventional geologic repository. This comparison<br />

fails to consider that the transport shaft proceeds directly to point <strong>of</strong> emplacement, that<br />

it must remain open during the entire emplacement period and that the geometry <strong>of</strong> the<br />

repository would strongly affect thermohydraulic considerations. (58)<br />

Response<br />

There is no conceptual problem in a shaft proceeding directly to the point <strong>of</strong> emplace-<br />

ment if the seal, including the interface to the rock, has an integrity at least as good as<br />

that <strong>of</strong> the undisturbed host rock and if the seal were a multibarrier system <strong>of</strong> seals. A<br />

discussion <strong>of</strong> R&D requirements, including those necessary to develop borehole seals, for<br />

the very deep hole concept is presented in Section 6.1.1.3.<br />

Draft p. 3.3.33<br />

Issue<br />

low? (35)<br />

Response<br />

If the permeability is less than as microdarcy, is not this permeability satisfactorily<br />

If no very short interval in the hole had a greater permeability, if there were reason-<br />

able porosity, and if there were a low hydraulic potential gradient throughout the region<br />

<strong>of</strong> interest, then the answer would most likely be yes. One fracture in an otherwise "tight"<br />

rock mass can make considerable difference, thus the permeability cannot be an average over<br />

much hole length. And since permeability is only one component to the flow the flow equa-<br />

tion, the other factors in the equation (hydraulic potential and porosity) must be taken

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