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

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387<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

This leads to the leachability and stability <strong>of</strong> the grout mixture. The binding agent<br />

is a combination <strong>of</strong> calcium carbonate and calcium silicate, both <strong>of</strong> which will be under-<br />

saturated in-most flow systems encountered at the shallow depths required for this system.<br />

The stability <strong>of</strong> this binding agent should be addressed in more detail. It is not suffi-<br />

cient to rely on the presence <strong>of</strong> the shale to sorb any ions released by the dissolution <strong>of</strong><br />

the cementing agent as most flow will be occurring in fractures created in the shale-grout<br />

mixture. (43)<br />

Response<br />

The effect <strong>of</strong> existing fractures and strength anisotropy when known can be included in<br />

an analysis <strong>of</strong> propagation directions. With multiple.fracture sets, the combination <strong>of</strong> in<br />

situ stress and strength anisotropy will determine the fracture propagation direction.<br />

Depth limitations based on probable in situ stress conditons in the continental U.S. are<br />

discussed in the.draft Statement in Section 3.8.1.4, and the final Statement in Section<br />

6.1.6.2. Section 6.1.3, R&D Requirements, <strong>of</strong> the final Statement discusses the need for the<br />

collection <strong>of</strong> geologic data before the well injection concept could be implemented. The<br />

fracture permeability <strong>of</strong> shales is recognized as important (see Section 3.8.2.1 <strong>of</strong> the draft<br />

Statement)<br />

Section 5.2.2.5 <strong>of</strong> the final Statement provides a discussion <strong>of</strong> requirements for depth<br />

<strong>of</strong> waste emplacement.<br />

References 45 and 46 from the draft Section 3.8 contain data on the extensive testing<br />

undertaken by ORNL on grout leachability. Section 6.1.6.3 <strong>of</strong> the final Statement, R&D Re-<br />

quirements, briefly addresses waste material development needs.<br />

Draft p. 3.8.1<br />

Issue<br />

A brief paragraph on retrievability appears. There is no assurance that the liquid<br />

waste, once pumped into a porous medium, is totally retrievable, a certain fraction <strong>of</strong> the<br />

waste will remain "captive" within the host rock. Total recovery, at any cost, is likely<br />

not attainable. A more detailed discussion focusing on the impact <strong>of</strong> partial recovery<br />

should appear. (208-NRC)<br />

Response<br />

The impacts <strong>of</strong> partial recovery are not yet fully known. Methods for effecting cor-<br />

rective action and the cost and benefits <strong>of</strong> their use-would be a necessary development for<br />

the implementation <strong>of</strong> the well injection concept. See Section 6.2 in the final Statement<br />

for a comparative discussion <strong>of</strong> attributes including those pertaining to corrective action.

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