Between 8 and 50 metric tonnes of excess plutonium are currently planned to be immobilized in a glass or ceramic waste form in the US. The immobilized Pu would then be encased in HLW glass (the can-in-canister alternative), which would provide a radiation barrier to enhance the proliferation resistance of the material. Associated with the plutonium are about 15 metric tonnes of uranium primarily {sup 238}U and a variety of other impurities (primarily Ga, Mo, Al, Mg, Si, and Cl) totaling about 1 metric tonne or less. Immobilization of this material is complicated by the fact that the uranium content in the various feed streams varies widely, from 0 to about 95%. The proposed ceramic form is composed of about 90% zirconolite (CaZrTi{sub 2}O{sub 7}) and/or pyrochlore (CaPuTi{sub 2}O{sub 7}) with about 10% other phases, typically hollandite (BaAl{sub 2}Ti{sub 6}O{sub 16}) and rutile (TiO{sub 2}). The form is a variation of Synroc-C, which contains nominally 30% zirconolite, 30% perovskite, 30% hollandite, and 10% rutile and noble metal alloys. Zirconolite and perovskite are the actinide host phases in Synroc-C with zirconolite being the more durable phase. The pyrochlore structure is closely related to zirconolite and forms at higher actinide loadings. Thus, …

Shape overlays provide a means of statically imposing a physical region containing specified material properties onto a zoned mesh. In the most general case, material interface boundaries are unrelated to mesh zone boundaries, causing zones to contain a mixture of materials, and the mesh itself is not uniform in physical space. We develop and apply an algorithm for shape overlays on nonorthogonal, nonuniform meshes in two dimensions. Examples of shape generation in a multiblock uid dynamics code are shown.