Disposal facility. Physical infrastructure of the facility, including tunnels or surface excavations, the surrounding host rock, and engineered barriers, including the waste form if present.

Disposal system performance. The ability of a disposal system to sequester radioactive and hazardous constituents in the near field.

Disposal system. Refers to both physical infrastructure and how the natural and engineered barriers in that infrastructure function to sequester radioactive and hazardous constituents.

Dissolution. A process (or processes) by which mass transport from a solid waste form to a liquid takes place as the result of mechanistic reactions in which chemical bonds are broken and constituents are released from a material and become solvated in a test solution.

Dissolution rate. The rate of mass removal per unit time normalized to surface area of the material.

Durability. The resistance of a waste form material to chemical and physical alteration and the associated release of contained radioactive and hazardous constituents.

Encapsulation. The process by which radioactive and hazardous constituents are physically surrounded and isolated by the material.

Experiment. The application of tests to a waste form material to gain a better understanding of its degradation behavior and the release of radioactive constituents.

Far-field environment. The region beyond the near field, including the biosphere.

Fluidized bed. A bed of granular material that exhibits fluid-like properties by passing a liquid or gas through it.

Fluidized Bed Steam Reforming. A process for thermally treating and immobilizing waste through the use of fluidized bed technologies.

Geologic repositories. Facilities constructed in geologic formations located hundreds of meters below Earth’s surface that are designed for the disposal of higher-hazard wastes such as spent nuclear fuel, high-level radioactive waste, and transuranic waste.

Geopolymers. Ceramic-like, inorganic polymers made from aluminosilicates cross-linked with alkali metal ions.

Glass. An amorphous solid material produced by cooling a material from a molten to a solid state without crystallization.

Glass-ceramic materials. Materials that contain both crystalline and glass phases.

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