Basic Research Needs for Geosciences - Energetics Meetings and ...

APPENDIX 1: TECHNICAL PERSPECTIVES RESOURCE DOCUMENTFor example, in Sweden, the proposed repository design (KBS-3 method) involves storage ofspent nuclear fuel assemblies within copper canisters (Figure 8). The waste canisters would thenbe emplaced in vertical holes drilled into crystalline bedrock at depths of around 500 m. Theholes are to be backfilled with bentonite clay to retard the transportation of radionuclides outsideof the canisters (Lundqvist 2006). The disposal of radionuclides within the saturated zone willresult in the ubiquitous presence of water, but will also ensure that the waste will reside in areducing environment, which will significantly reduce the solubility of many radionuclides.While the elements of the proposed Yucca Mountain repository design differ from those beingconsidered in other countries, the engineered and natural components for the Yucca Mountainsite and how they function together are still illustrative and provide the required context for themore general discussion of technology and applied R&D perspectives and needs. Much of thediscussion below is taken from DOE (2002c), and the reader is referred to that report for muchmore detail. Information available in Witherspoon and Bodvarsson (2006) and on the webdescribing international high-level waste management sites illustrates the common themes andthe different geologic, hydrologic, and geochemical settings being considered worldwide (e.g.,unsaturated zone sites in tuff and saturated zone sites in granite, salt, or clay; see Table 7).The barriers important to waste isolation are broadly characterized as engineered barriers andnatural barriers associated with the geologic and hydrologic setting. The engineered barriers aredesigned specifically to complement the natural system in prolonging radionuclide isolationwithin the disposal system and limiting their potential release. Natural barriers would contributeto waste isolation by (1) limiting the amount of water entering emplacement drifts, and(2) limiting the transport of radionuclides through the natural system.In addition, the natural system provides an environment that would contribute to the longevity ofthe engineered components (disposal canisters and waste forms). The components of theengineered system are designed to complement the natural barriers in isolating waste from theFigure 8. Schematic illustration of the Swedish concept for a deep geologic repository(Lundqvist 2006).Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems Appendix 1 • 27