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

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6.53<br />

Repository Facility. The layout <strong>of</strong> the reference repository for island disposal is a<br />

preliminary adaptation <strong>of</strong> the conventional geologic disposal concept discussed in Chapter 5.<br />

It is assumed that the island bedrock is crystalline and that the waste is emplaced approxi-<br />

mately 500 m underground.<br />

The conceptual design for an island crystalline rock repository is not supported by a<br />

data base comparable to that for salt repositories. The crystalline rock conceptual design<br />

discussed in Chapter 5 is assumed to be applicable to the underground aspects <strong>of</strong> island<br />

disposal except salt stockpile handling equipment would not be needed. The surface facili-<br />

ties for island disposal are assumed to be the same as for conventional mined geologic dis-<br />

posal.<br />

Assuming that the repository capacity for spent fuel disposal is the same as for the con-<br />

ventional mined geologic disposal and that sufficient intermediate storage and transportation<br />

capacity can be provided, the once-through cycle would require four to eight island reposi-<br />

tories, depending on the media. More respositories would be needed if island area were<br />

insufficient to support a repository <strong>of</strong> the size discussed in Chapter 5. Uranium-plutonium<br />

recycle wastes would require six to ten island repositories, depending on the island media<br />

(DOE 1979). The scheduled availability <strong>of</strong> the repositories for wastes from both fuel cycles<br />

would be expected to be a few years behind that <strong>of</strong> the conventional mined geologic disposal<br />

program.<br />

Retrievability/Recoverability. Retrievability <strong>of</strong> emplaced waste or spent fuel from the<br />

rooms would be essentially the same as for the conventional mined geologic repository in<br />

crystalline rock. If retrieval were required because <strong>of</strong> deterioration or failure <strong>of</strong> the<br />

waste containers, special transportation containers and storage facilities would be needed.<br />

This need could be met by using a special cask design suitable for either rail, truck, or sea<br />

transport. Recoverability would also be similar to that with mined geologic disposal and<br />

would involve techniques similar to those used for the original emplacement process. Retrie-<br />

vability from island repositories could be complicated by the hydrogeologic characteristics<br />

<strong>of</strong> the sites.<br />

Sealing, Decommissioning, and Monitoring. The sealing concepts might be the same as<br />

those for conventional mined geologic disposal in crystalline rock. The principal difference<br />

would be in the supply <strong>of</strong> labor and materials, which would involve sea transport to the<br />

island.<br />

Final decommissioning <strong>of</strong> the island facilities could involve underground disposal <strong>of</strong> all<br />

contaminated equipment, the removal or disposal <strong>of</strong> all surface facilities, and suitable re-<br />

storation and landscaping <strong>of</strong> the island.<br />

Monitoring systems would be used during emplacement operations to detect air, surface<br />

water, and ground-water contamination. After the repository was sealed, a long-term moni-<br />

toring system would be implemented. This system would be similar to those for the conven-<br />

tional geologic disposal concept, with modifications to suit the island option.

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