BOX 5.1
Key Terms and Concepts

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.

Dissolution: A process (or processes) by which mass transport from a solid waste form to a liquid takes place (see ASTM C1308, ASTM C1220). Dissolution is 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 (see ASTM C1662).

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.

Leaching: The loss of radioactive or chemical constituents from a waste form by diffusion or dissolution.

Performance: The ability of a waste form (waste form performance) or a disposal system containing the waste form (disposal system performance) to sequester radioactive and chemical constituents.

Release mechanisms: The process that controls the rate of mass transport out of a specimen during dissolution (see ASTM C1308).

Solubility: The thermodynamically limited saturation state or equilibrium concentration limit of species in solution.

Standard test protocols: A standardized procedure for testing a specific type of material to generate a clearly defined test response. In principle, any test can be applied to any material to generate a response. However, a response will be meaningful only when the test and material are matched appropriately (see Section 5.1).

Waste form qualification: Demonstration that a waste form material will have acceptable performance in a specific disposal facility and can be fabricated with acceptable performance control.

Waste form test protocols: Standard tests developed by organizations such as the American Nuclear Society, American Society of Testing and Materials, International Atomic Energy Agency, and the International Organization for Standardization (see Section 5.3).

5.1 PURPOSE OF WASTE FORM TESTING

Laboratory testing of waste form materials is undertaken for several purposes, including to:

  • Conduct experiments to elucidate the release mechanisms of radioactive and chemical constituents from a waste form material.


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