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

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Response<br />

363<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

b. The likelihood <strong>of</strong> biotransport is enhanced by the combination <strong>of</strong> thermal and<br />

solution effect. (124)<br />

If the canister sinks, it will approach bedrock which is fissured and allows high water<br />

migration rates. If the sediment rises and. carries the canister upward, the sediment column<br />

and, hence, long-term barrier is rendered less effective.<br />

The canister currently envisioned is a temporary barrier in the sense that it is<br />

intended to contain the waste only through the heat generation period after which a breached<br />

canister will release wastes at essentially ambient temperatures only. It should be empha-<br />

sized that the penetrometer represents an additional barrier to waste release, and that<br />

additional engineered barriers might be incorporated into the package.<br />

Draft p. 3.6.6<br />

Issue<br />

Supposing the correctness <strong>of</strong> the assumptions, the breakthrough time, T, is not a<br />

million years, but is:<br />

Response<br />

T = D2/A = (100 m)2/(3 x 10-6cm2/yr) = 3 x 1013 yrs (23-DOC)<br />

The A value should be:<br />

Thus:<br />

3 x 106 cm2/sec = 3.15 x 107 sec/yr x 3 x 10- 6 cm 2 /sec =9.5 x 10 cm2/yr<br />

D2/A = 108 cm2/9.5 x 10 cm2/yr = 1.05 x 10 6yr<br />

or approximately 1 million years.<br />

Draft p. 3.6.6, Table 3.6.2<br />

Issue<br />

The sorption coefficients listed are credible although they could easily be 1 or 2<br />

orders <strong>of</strong> magnitude in error. Their source should be properly explained and cited. They<br />

should not be used for transport-time calculation. (218-D01)<br />

Response<br />

The sorption coefficients have been measured and their values have been documented.<br />

(See Russo 1979, Talbert 1977, Tablert 1979, Talbert 1980, and McVey 1980)<br />

The transport time calculation is based on an assumed molecular diffusion constant<br />

wherein no interaction between the dissolved nuclides and the sediment is assumed.

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