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.

242<br />

GEOLOGIC CONSIDERATIONS<br />

selection and testing would disqualify any site which had joint-fracture characteristics<br />

that could lead to severe problems or uncontrollable water flows.<br />

Draft p. 3.1.32<br />

Issue<br />

(218-DOI)<br />

Response<br />

The questions <strong>of</strong> shaft and borehole plugging apply to all media, not just salt.<br />

This section <strong>of</strong> draft was revised. Questions associated with borehole sealing and<br />

research currently under way on these questions is discussed in the Final Statement in final<br />

Section 5.2.3.3 and in final Appendix L.<br />

Draft p. 3.1.32<br />

Issue<br />

This section about Rock Permeability and Ground-water Flow accurately describes the<br />

problems <strong>of</strong> ground-water flow, particularly through fractures. The statement that "Ground-<br />

water flow into repository shafts and rooms can be controlled by state <strong>of</strong> the art engineer-<br />

ing technology", is only true <strong>of</strong> a mine which operates wet. The statement is not true if<br />

radioactive waste is to be isolated. (214)<br />

Response<br />

For repositories located in formations other than salt, the assumption is made that the<br />

repository will fill with water after closure. The capacity <strong>of</strong> the repository to isolate<br />

waste is then a function <strong>of</strong> the ground water flow rate, the transport rate <strong>of</strong> radionuclides<br />

through the formation, the leaching rate <strong>of</strong> the waste form, and the decay rate <strong>of</strong> the radio-<br />

nuclides. Because many uncertainties are involved in calculating the migration <strong>of</strong> radionuc-<br />

lides (arising in part from uncertainty in the validity <strong>of</strong> the models and parameters used<br />

in them) an additional level <strong>of</strong> protection will be added. This level <strong>of</strong> protection will be<br />

provided by the engineered barriers that make up the waste package. These barriers include<br />

the canister, the overpack sorption materials and backfill. The package itself will be des-<br />

igned to contain the waste under repository conditions for hundreds <strong>of</strong> years which allows<br />

for decay <strong>of</strong> a majority <strong>of</strong> short lived radionuclides with a corresponding reduction <strong>of</strong> waste<br />

temperature. The reduction in temperature after the life <strong>of</strong> the package is reached reduces<br />

the leach rate <strong>of</strong> the waste form and thus the concentration <strong>of</strong> radionuclides available for<br />

migration in ground water.

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

Saved successfully!

Ooh no, something went wrong!