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.

265<br />

GEOLOGIC CONSIDERATIONS<br />

The preliminary site selection process (Section 5.1) considers such factors as resource<br />

potential, proximity to natural resources, tectonic stability, water system, etc. The<br />

Statement considers that repositories are potentially feasible in all media. However, the<br />

Statement acknowledges that there are some unresolved issues regarding these media and sug-<br />

gests continued research and development to fill existing data gaps.<br />

Issue<br />

The statement that granite has "...little ability to deform under stress" is not true.<br />

Under varying combinations <strong>of</strong> the following: 1) high confining pressure, 2) elevated temper-<br />

atures, or 3) when the stresses are applied for long time spans, granite will deform.<br />

(208-NRC)<br />

Response<br />

Granite will undergo deformation under the influence <strong>of</strong> pressure, time, and tempera-<br />

ture. For the levels <strong>of</strong> these phenomena predicted in a repository, however, such deforma-<br />

tions are expected to be small and certainly manageable.<br />

The deformation characteristics <strong>of</strong> granites are being studied analytically, in the lab-<br />

oratory, and in field experiments approximating repository conditions. Information obtained<br />

from these studies will be used to evaluate deformations in, and prepare designs for, a<br />

repository in granite.<br />

Issue<br />

The statement that the "mineral components <strong>of</strong> granite are almost inactive chemically<br />

under ambient temperature and pressure conditions" is misleading. Granite does decompose<br />

at surface temperatures and pressure as evidenced by well developed regoliths found on top<br />

<strong>of</strong> many granites. (208-NRC)<br />

Response<br />

Given the anticipated time frame (on the order <strong>of</strong> several tens <strong>of</strong> years) for exposure<br />

<strong>of</strong> granitic rocks to ambient temperature and pressure in a repository excavation, it is<br />

reasonable to assume that the mineral components <strong>of</strong> granite would be relatively inactive<br />

chemically. Decomposition <strong>of</strong> granite into well developed regoliths under conditions <strong>of</strong> sur-<br />

face temperature and pressure is a phenomena requiring periods <strong>of</strong> time orders <strong>of</strong> magnitude<br />

greater than those expected for similar physical conditions in a repository. In addition,<br />

regolith formation is assisted by constant exposure to the hydrologic cycle. Repository<br />

design will be such that moisture in the excavation will be kept to a minimum.

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

Saved successfully!

Ooh no, something went wrong!