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

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5.2<br />

This section provides an overview <strong>of</strong> general considerations in the design and location<br />

<strong>of</strong> geologic repositories. Additional details including references to specific studies in<br />

the literature are given in Appendix B <strong>of</strong> Volume 2. Details <strong>of</strong> both engineered and natural<br />

barriers to waste release are also presented.<br />

5.1.1 Factors Relevant to Geologic Disposal<br />

Six factors relevant to geologic disposal are:<br />

1. Depth <strong>of</strong> repository below the land surface. Presently it is assumed that a range<br />

<strong>of</strong> from 600 to 1,000 m <strong>of</strong> earth material will exist between the repository and the<br />

land surface. This will provide a barrier between the waste and the biosphere and<br />

protect the repository from human activities. Dimensions <strong>of</strong> the host rock are<br />

also considered so that the repository will be buffered by rock material laterally<br />

and below as well as above it. An artist's conception <strong>of</strong> a repository is shown<br />

together with more familiar structures in Figure 5.1.1.<br />

2. Properties <strong>of</strong> the host rock. The physical, chemical, and thermal properties <strong>of</strong><br />

the host rock determine the rock's capability to isolate and contain the waste and<br />

reduce unwanted interactions between the rock and waste. These possible interac-<br />

tions include radiation effects on the rock and chemical and physicochemical<br />

interactions. Important rock characteristics include strength, permeability,<br />

thermal conductivity and expansion, and radiation resistance.<br />

ELEVATOR SHAFT FOR<br />

SPENT FUEL OR FUEL<br />

REPROCESSING WASTES<br />

WASTE CANISTERS<br />

STORAGE AREA FOR<br />

MINED MATERIAL<br />

STORAGE AREA FOR<br />

SPENT FUEL OR FUEL<br />

REPROCESSING WASTES<br />

10 METERS G 10 METERS<br />

FIGURE 5.1.1. Deep Underground Geologic <strong>Waste</strong> Repository<br />

WASHINGTON<br />

MONUMENT<br />

ME EMPIRE STATE<br />

BUILDI NG

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