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Case subsurface emplacement by spacing waste packages at a greater distance than the design emplacement spacing. After the commercial spent nuclear fuel in the waste package has thermally cooled, the waste packages would be moved closer together to place them at the design waste package emplacement spacing. This subsurface recommendation has the following advantages compared to surface aging: a. b. C. d. e. Safety and health risks are minimized compared to surface aging locations. Worker radiological exposure and additional handling operations are similar to the Base Case design. The design is more resistant to terrorist activities. As evaluated in this study, there are no additional capital costs over the Base Case. The capital cost for surface aging is greater than for subsurface aging in the emplacement drifts since additional surface aging facilities, shield casks, and cask transportation equipment will be needed. The licensing approach is similar to the Base Case and does not require new designs to be licensed. The design is compatible with the Waste Handling Facility current scope and does not impose new handling or equipment requirements on the Waste Handling Facility. 2. Surface Aging Recommendation-Age commercial spent nuclear fuel in a dual-purpose canister, multipurpose canister, or disposable canister in any of the four surface locations considered. This surface aging recommendation has the following advantages compared to subsurface aging: a. Surface aging is more flexible than subsurface aging in decoupling receipt from emplacement. b. Surface aging sites can be developed in stages, as needed to support aging requirements. c. The design will not require complete processing of waste packages prior to aging. This will be less of a constraint to operations and plant throughput than subsurface aging in the waste package. d. The design is more flexible in accommodating changes to the repository thermal operating mode. e. The design allows for slower underground emplacement, without restricting receipt rates. TDR-MGR-MD-0000 1 1 REV 00 V April 2002 PREDECISIONAL STUDY f. The waste containers included in this option are ranked highest in the technical evaluation. 3. Combination of limited surface aging and subsurface aging Recommendation-Rather than only surface or subsurface aging, use a combination of limited surface aging with the remaining commercial spent nuclear fuel aged in the permanent emplacement drifts. This limited surface and subsurface recommendation has the following advantages: a. Compared to all subsurface aging: 1) Improves the ability to decouple waste receipt from emplacement. 2) Reduces the need to process waste packages prior to aging. Compared to all surface aging: 1) Reduces safety and health risks associated with worker radiological dose and b. additional handling operations. 2) Is more resistant to terrorist activities because of the smaller surface aging footprint. 3) Reduces capital costs. April 2002 TDR-MGR-MD-000011 REV 00 vi Revision Interim Number Change No.

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Planar, power-driven expansion into a vacuum is found to be self-similar for a power-law driving source for the two ideal cases of a thick slab and a thin foil. For the thick slab expansion, an asymptotic solution for the far-blowoff region is obtained and a numerical solution is present for the rest of the expansion wave. For the thin foil expansion, an analytical solution is obtained. In both cases, the solutions exhibit an unbounded flow field with velocities tending to infinity as a consequence of the continuum assumption, a finite temperature limit for the far-blowoff material, and density profiles that decrease as a Gaussian in the far expanded material.