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

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B.16<br />

applicable as disposal media are situated in distinct sedimentary basins throughout many <strong>of</strong><br />

the contiguous 48 states, as illustrated in Figure B.6.2 (Office <strong>of</strong> <strong>Waste</strong> Isolation 1978b).<br />

The existence <strong>of</strong> salt beds and formations that are known to be hundreds <strong>of</strong> millions <strong>of</strong><br />

years old testifies to their isolation from water and their stability. Salt deposit<br />

strength properties are relatively fair to good in the undisturbed state. Salt is basically<br />

isotropic with minimal cohesive strength. The result is a highly plastic medium that tends<br />

to move (creep) under earth pressures, increasing with greater depth and temperature. Creep<br />

tends to seal discontinuities but is difficult to stabilize in tunnel openings. Although<br />

heat tends to reduce strength, high thermal conductivity <strong>of</strong> salt is conducive to heat dissi-<br />

pation. A salt deposit may contain moisture in interbed materials and in small cavities as<br />

brine inclusions. These brine inclusions have been shown to migrate or move toward a heat<br />

source (ERDA 1976). Salt moisture, if present, leads to increased heat effects and to the<br />

potential for strength loss from solution action. Undisturbed salt beds are essentially<br />

impermeable (Office <strong>of</strong> <strong>Waste</strong> Isolation 1978a,b).<br />

Rock types associated with salt deposits include anhydrite (CaSO 4 ), limestone (CaCO 3 ),<br />

dolomite, (CaCO 3 MgCO 3 ), and shale (Si0 2 , A1 20 3 , Fe20 3, FeO, MgO, CaO, Na20, K 20). Hal-<br />

ite is highly soluble (Office <strong>of</strong> <strong>Waste</strong> Isolation 1978a). More information is needed about<br />

ion exchange rate, reaction to radioactivity, and potential chemical reactions with salt<br />

deposits, related rock types, and waste materials.<br />

WILLISTON<br />

BASIN<br />

SRIVER<br />

S-- BASIN WASHAKIE [<br />

ASIN<br />

ALLIANCE BASIN -<br />

MICHIGAN<br />

BASIN<br />

APPALACHIAN BASIN<br />

SEVIER PICEANCE LUSK<br />

BASIN I BASIN . EMBAYMENT \<br />

SDENVER BASIN<br />

ARO \PERMIAN<br />

o I"<br />

BASIN<br />

ANDARKO BASIN GIUAF<br />

REA VIRGIN PALA OURO BASIN<br />

R R 2<br />

LAKE<br />

VALLEY ' SUPAI<br />

INTERIORSALTDOMES<br />

DELAWARE<br />

SUB-BASIN COASTAL SALT DOMES<br />

SBASINS CONNING SA<br />

GULFBASIN SOUTH<br />

FLORIDA<br />

SUB-BASINS CONTAINING RELATIVELY<br />

THICK BEDDED SALT, SALT DOMES. OR<br />

SALT ANTICLINES<br />

FIGURE B.6.1. Bedded Salt Deposits and Salt Domes in the<br />

United States (adapted from Office <strong>of</strong> <strong>Waste</strong><br />

Isolation 1978a)

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