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

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6.168<br />

Spent fuel assemblies would be packaged individually into canisters at a waste packag-<br />

ing facility located in the continental U.S. All canisters would be loaded into shipping<br />

casks and transported by rail to the embarkation port facility. At the port-facility the<br />

waste packages would be transferred from the rail casks to ocean shipping casks which would<br />

be loaded aboard ocean-going vessels. These vessels would transport the waste to a receiv-<br />

ing port on the U.S.-owned repository island. <strong>Waste</strong> casks would be transferred to rail or<br />

highway vehicles for shipment to the repository site. Here the canisters would be unloaded<br />

from the shipping casks, placed in multibarrier packages, and placed in individual boreholes<br />

in the floor <strong>of</strong> mined chambers at least 500 m deep in granite or basalt, located either<br />

within the fresh groundwater lens or within underlying saline groundwater. Backfill would<br />

be placed around each package following emplacement. As each chamber is ready it would be<br />

backfilled and sealed. When the repository is filled the access tunnels and shafts would<br />

be backfilled with appropriate materials and sealed.<br />

A reprocessing fuel cycle would require high-level liquid waste to be converted into<br />

an immobile solid that would be incorporated into a multibarrier package compatible with the<br />

island geologic environment. Other wastes would be packaged and emplaced in the island<br />

repository.<br />

6.2.1.5 Subseabed Disposal<br />

In the subseabed disposal concept, disposal <strong>of</strong> waste would be achieved by remote<br />

emplacement in relatively thick, stable beds <strong>of</strong> sediment located in deep, quiescent, and<br />

remote regions <strong>of</strong> the oceans. Engineered multibarrier containment would be provided by the<br />

waste form, canister, and the outer body <strong>of</strong> the emplacement container. Isolation and a<br />

natural barrier would be provided by clay sediments which would be chosen for uniformity,<br />

high plasticity, low permeability, high sorption potential, long-term stability and low<br />

resource attractiveness. The ocean itself would enhance remoteness, providing protection<br />

from human intrusion. Because the ocean is part <strong>of</strong> the accessible environment it would not<br />

be considered as a barrier to waste release.<br />

Spent fuel assemblies would be packaged individually in canisters at a waste packaging<br />

facility located in the continental U.S. Packaged fuel assemblies would be loaded into<br />

shipping casks and transported by rail to the embarkation port facility. At the port facil-<br />

ity waste packages would be removed from the shipping casks and loaded into emplacement<br />

vehicles, probably free fall penetrometers. These would be loaded onto special oceangoing<br />

vessels and transported to the emplacement site, located in the mid-plate, mid-gyre region<br />

<strong>of</strong> the ocean with depths <strong>of</strong> 3,000 to 5,000 m. At the site the penetrometers would be<br />

released to penetrate 50 to 100 m into the clay sediment. Closing <strong>of</strong> the hole above the<br />

penetrometers might occur spontaneously or be accomplished by mechanical means and would<br />

seal the waste into the sediment. A monitoring vessel would verify satisfactory<br />

emplacement.

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