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

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Response<br />

384<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

The need for seal systems development is discussed in the final Statement in Sec-<br />

tion 6.1.6.3, Status <strong>of</strong> Technical Development and R&D Needs. Estimates are not currently<br />

available for cost or time to develop technology that would be necessary for the implemen-<br />

tation <strong>of</strong> the well injection concept. See Section 6.2 <strong>of</strong> the final Statement for a compara-<br />

tive assessment <strong>of</strong> alternative waste disposal technologies.<br />

Draft p. 1.28<br />

Issue<br />

What advantages does the reverse well disposal alternative have? It is not clear why<br />

it is being considered. (34, 154)<br />

Response<br />

The well injection concept involves pumping grout slurry wastes to depths from 1000m<br />

to 5000m into porous or fractured rock strata which would be isolated from the biosphere by<br />

relatively impermeable overlying strata. The grout mixture would harden to a low leach<br />

mass. This is a relatively low cost alternative concept designed to retard nuclide move-<br />

ment by minerals within the rock strata. Because <strong>of</strong> the depth <strong>of</strong> disposal, the probability<br />

<strong>of</strong> a breach by either natural or human induced events are low. See Section 6.1 <strong>of</strong> the final<br />

Statement for additional discussion <strong>of</strong> the well injection concept. Also see Section 6.2 <strong>of</strong><br />

the final Statement for a discussion <strong>of</strong> the attributes and disadvantages <strong>of</strong> a alternative<br />

concepts and the mined geologic repository.<br />

Draft pp. 1.28 and 1.32<br />

Issue<br />

The discussion and assessment <strong>of</strong> the reverse well injection alternative should include<br />

a general consideration and evaluation <strong>of</strong> the vertical separation <strong>of</strong> individual plates or<br />

sheets <strong>of</strong> injected waste-bearing grout. Consideration <strong>of</strong> the impacts <strong>of</strong> the alternative<br />

should also include at least generalized assessment <strong>of</strong> effects <strong>of</strong> possible deviation <strong>of</strong><br />

sheets from bedding planes and possible unplanned or unscheduled accumulation <strong>of</strong> wastes in<br />

any given zone. (218-D01)<br />

Response<br />

Consideration and evaluation <strong>of</strong> the vertical separation <strong>of</strong> individual plates or sheets<br />

<strong>of</strong> injected waste-bearing grout would be important in the design <strong>of</strong> a well injection dis-<br />

posal system. For example, the number <strong>of</strong> grout sheets and their separation would be depen-<br />

dent on the gross thermal loading acceptable for the host rock.

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