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

6.41
Implementation Time and Estimated R&D Costs
In view of the significant technical uncertainties remaining, it is not possible to
predict a cost estimate of the required R&D to implement this concept, nor the amount of time
it would take.
Summary
Major uncertainties, shortccmings, and advantages of the concept are summarized below:
* There is not a multiplicity of engineered barriers .inherent to the concept.
* The temperature, chemistry, and other characteristics of the molten waste-rock mixture
are not considered consistent with technical conservatism.
* The required characteristics of a site are not known, and criteria for selection are
considered extremely difficult to derive.
* The concept cannot be implemented in a step-wise, technically conservative manner due to
the scale required for demonstration.
* Performance assessment capability is perhaps most distant for this concept than for any
other.
* Retrievability of the waste is considered to be unlikely, so that corrective action
cannot be accomplished.
* The time required for monitoring prior to full solidification (defined as the operational
period of up to 1,000 years for this concept) exceeds the likely acceptable life
for institutional controls.
* The primary postulated advantage relates to the possibility that the solidified waste
form might be more stable than other possible forms.
* Lower mining requirements compared to a mined geologic repository may be a secondary
advantage.
6.1.2.4 Impacts of Construction and Operation (Preemplacement)
Potential environmental impacts of a rock melt repository would be similar in many re-
spects to those of a mined geologic repository. Both would require surface and subsurface
activities that lead to environmental impacts. This impact analysis focuses on unique
aspects of the rock melt concept, and refers to discussions on mined geologic emplacement in
Section 5.4 as appropriate.
Health Impacts
Health studies related to the rock melt concept for the disposal of HLW can be divided
into two phases: the presealing phase, which includes waste transportation and active oper-
ation of the waste disposal facility, and the postsealing phase, which includes the melting
and resolidification of the HLW/ rock matrix and its long-term effects. In the following
discussion, radiological and nonradiological concerns for the first phase are covered
separately.