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

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B.22<br />

CONTINENTAL U.S.<br />

TECTONIC CONSIDERATIONS<br />

HYDROLOGIC CONSIDERATIONS<br />

STAGE I CANDIDATE REGIONS<br />

HYDROLOGICALLY ACCEPTABLE<br />

TECTONICALLY ACCEPTABLE<br />

FIGURE B.7.1. Site Selection Process, Stage I<br />

outlining the most suitable regions. Optimal choices for candidate regions are areas that<br />

satisfy both broad considerations. A hypothetical Stage I candidate region, for instance,<br />

could be an area that passes certain criteria both for optimal tectonic stability and<br />

hydrologic conditions. Selection <strong>of</strong> candidate regions can be accomplished by a thorough<br />

evaluation <strong>of</strong> available literature, existing geologic exploration data, and other existing<br />

information such as satellite imagery.<br />

The candidate regions defined in Stage I enter into Stage II <strong>of</strong> the site selection pro-<br />

cess (see Figure B.7.2). General geologic considerations are applied on a scale appropriate<br />

to regional study, and criteria are again established to select areas with the most accept-<br />

able characteristics. A similar process is followed for each additional consideration (i.e,<br />

regional tectonics, hydrology, and depth). Optimal choices for candidate siting areas are<br />

those that have satisfied all Stage II considerations.<br />

Data base additions required for evaluation in Stage II include extensive geologic map-<br />

ping, generic research on rock properties (particularly their temperature dependence), characterizations<br />

<strong>of</strong> regional hydrology, climatic data, and instrumental data such as that<br />

obtained from geodetic, geophysical and microseismic networks.<br />

A major task in Stage II will be to determine the activity or inactivity <strong>of</strong> fault<br />

systems within candidate areas. Repository siting will be ruled out within a designated<br />

distance from active faults to protect against possible fault rupture and the effects <strong>of</strong><br />

strong seismic shaking. Repository siting criteria for seismic hazards have not been estab-<br />

lished. However, they may resemble current criteria <strong>of</strong> the Nuclear Regulatory Commission<br />

for siting <strong>of</strong> nuclear power plants.<br />

The results <strong>of</strong> the above studies will be basic input to hydrologic considerations and<br />

Stage III modeling <strong>of</strong> specific sites. Stage III will require collection <strong>of</strong> as much

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