The United States Department of Energy is building the Hanford Waste Treatment and Immobilization
Plant (WTP) in south-central Washington State to immobilize a portion of the stored high-level radioactive wastes generated by decades of producing nuclear defense materials. To comply with United States
Environmental Protection Agency (EPA) and Washington State air emission regulations, the WTP is
planning to use reduced silver mordenite to control releases of any volatilized waste constituent radioiodine ( 129I t1/2 = 1.7 107 a). Because the EPA and Washington State have designated silver as a
hazardous or dangerous waste constituent, the disposal form for the waste reduced silver mordenite
must comply with their land disposal regulations. We used the mandated EPA Toxic Characteristic Leach
Procedure to evaluate and qualify a disposal form for the waste reduced-silver mordenite. Our development effort resulted in a regulation-compliant disposal form which used cast American Society for Testing and Materials (ASTM) Portland Type III cement modified to include calcium iodide to solidify and
stabilize the reduced-silver mordenite and control silver release to regulatory levels.