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

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Draft p. 3.1.148<br />

Issue<br />

255<br />

GEOLOGIC CONSIDERATIONS<br />

First paragraph, last sentence reads, "It is doubtful that any fault would form a con-<br />

tinuously permeable conduit to the repository, even if a fault should occur through the<br />

repository to the land surface." Faults <strong>of</strong>ten form conduits which transport water, and are<br />

<strong>of</strong>ten located by the presence <strong>of</strong> springs along their length. The study by Meinzer (Meinzer<br />

1942) states that 3 <strong>of</strong> 65 first magnitude springs in the United States are located in sand-<br />

stone, and that they are believed to owe their existence to faults or other special<br />

features. (214)<br />

Response<br />

The influence <strong>of</strong> postclosure faulting on the capacity <strong>of</strong> a repository to isolate waste<br />

will be considered in the analysis <strong>of</strong> repository performance. Currently the modeling capab-<br />

ility exists to conduct detailed calculations <strong>of</strong> the effects <strong>of</strong> post-closure faulting on<br />

radionuclide migration. Preliminary calculations have been done for a hypothetical repos-<br />

itory in salt and are published in a document entitled Test Case Release Consequence Anal-<br />

ysis for a Spent Fuel Repository in Bedded Salt (Raymond et. al. 1980). These calculations<br />

assumed a vertical fault through the repository and overlying aquifers and extended to the<br />

ground surface. Because <strong>of</strong> the nature <strong>of</strong> the test case, many <strong>of</strong> the parameters had to be<br />

assumed; therefore, a sensitivity analysis was conducted to determine how changes in para-<br />

meter values affected the resulting dose-to-man calculations. These results are published<br />

in Paradox Basin Sensitivity Analysis (Bond and Kaszeta 1979). These types <strong>of</strong> calculations<br />

will be done for all repository sites to determine the effect <strong>of</strong> post-closure faulting even<br />

though the likelihood <strong>of</strong> faulting is small.<br />

Draft pp. 3.1.228, 3.3.22, 3.3.27, 3.3.30<br />

Issue<br />

Maintenance <strong>of</strong> the integrity <strong>of</strong> shaft seals, room seals and canister seals (particu-<br />

larly in salt) would be expected to pose greater problems than in Very Deep Hole disposal.<br />

(208-NRC)<br />

Response<br />

The entire question <strong>of</strong> sealing is still under study (See Section 5.2 <strong>of</strong> final State-<br />

ment). For the underground mined repository, it has been proposed to backfill the rooms<br />

with material removed from the repository during mining, thus completely surrounding the<br />

waste with host rock material. The shaft(s) to the repository are a more complicated prob-<br />

lem because <strong>of</strong> the various rock materials between the repository and the land surface. The<br />

very deep hole is similar to the mined shaft in this respect plus having drilling mud

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