23.04.2013 Views

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

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

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

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Response<br />

359<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

The continental margins have been removed from consideration as possible sites for<br />

waste disposal. Reasons for this include present knowledge <strong>of</strong> the abundance <strong>of</strong> biological<br />

and mineral resources in these areas; the frequency and broad use <strong>of</strong> coastal waters; the<br />

relatively low and highly variable sorptivity <strong>of</strong> coastal margin sediments; and the diffi-<br />

culty in developing reliable methodologies for predicting the future characteristics <strong>of</strong><br />

sediments in these regions. Similarly, proximal (i.e. landward) portions <strong>of</strong> abyssal plains,<br />

where relatively thick and permeable sand layers generally exist, have been removed from<br />

consideration. (See also Talbert 1979 and Talbert 1980.)<br />

Draft p. 3.6.3<br />

Issue<br />

The footnote on p. 3.6.3 discusses abyssal "deserts". This may be an overstatement.<br />

As abyssal depths continue to be explored, we are finding that deep areas are not biologi-<br />

cally sterile. We know the real desert is a complex and fragile ecosystem. The lay reader,<br />

however, may interpret desert to be equal to sterile. Table 3.6.1 is more accurate and cor-<br />

rects the overstatement in the footnote. Suggest deleting the note entirely. (124)<br />

Response<br />

The deep sea is likely to be equivalent to the desert in terms <strong>of</strong> being a subtly com-<br />

plex ecosystem. While the deep sea has a very low standing crop, "desert" is not an accu-<br />

rate simile. As suggested in this comment, the note has been deleted from the text <strong>of</strong> the<br />

final Statement.<br />

Draft p. 3.6.4<br />

Issue<br />

The sediment thickness is reported to be 50 to 100 meters, while in Table 3.6.1 it is<br />

given as 100 to 300 meters. (208-NRC)<br />

Response<br />

Sediment thickness depends upon many processes: erosion and deposition, size <strong>of</strong> the<br />

ocean basin, inputs from the continental margins, etc. Generally, the older the crust, the<br />

thicker the sediments. The sediments have a thickness <strong>of</strong> approximately zero at the midocean<br />

ridge and get progressively thicker as one moves away from the ridge across the older<br />

plates. Sediments vary in thickness from ocean to ocean as well as within each ocean. The<br />

minimum thickness presently thought to be needed (from basement rock to sediment surface)<br />

is 60 m, but this is tentative, and depends on what is learned from the ion-transport<br />

studies that are just beginning to produce results.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!