A vitreous ceramic waste form for Oak Ridge K-25 pond wastes
Conference
·
OSTI ID:210162
- Pacific Northwest Lab., Richland, WA (United States); and others
The 16 million kilograms of K-25 pond sludge/soil contains EPA-listed F006 waste and radionuclides such as U, Tc and Cs. It has been known that the waste loading of K-25 sludge cannot be more than 30% in a glass waste form in order to meet the 0.32 ppm limit on Ni release in an EPA TCLP test according to Land Disposal Restriction (LDR). The treatment of this waste, using vitreous ceramics (VC), is being studied at Pacific Northwest laboratory. VC is a waste form consisting of metal oxides embedded in a silicate glass matrix. The carefully designed melting and heating treatment of a VC sample, LVC-5, resulted in targeted crystal formation of magnetite (including trevorite and chromite, hosts for Ni and Cr), potassium feldspar (host for Cs{sup +}), and Ca-P phases (host for Ce, a surrogate for U and Pu). The LVC-5 was made of almost 100 wt% Oak Ridge K-25 pond sludge. The PCT results of LVC-5 show a normalized release of 0.38 g/m2, which is a factor of 18 lower than that of high-level EA glass. The hazardous element releases in EPA TCLP test are at least 476 times lower than the EPA limits. More significantly, the Ni concentration in the TCLP leachate is less than 0.02 PPM (detection limit of ICP-AES), which is at least 16 times lower than the LDR limit of 0.32 ppm. An improved formulation and melting of another VC sample, LVC-6, at 90 wt% loading of K-25 pond sludge and 10 wt% Oak Ridge soil, showed a PCT Na release of 0.16 g/m2, which is 42 times lower than that of EA glass. The TCLP concentration of LVC-6 is at least 2000 times lower than EPA limits. The detailed properties of the VC samples for immobilizing K-25 pond wastes are discussed in the full paper.
- OSTI ID:
- 210162
- Report Number(s):
- CONF-9509139--
- Country of Publication:
- United States
- Language:
- English
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