Comparison of TCLP and long-term PCT performance on low-level mixed waste glasses

The Mixed Waste Integrated Program (MWIP) of the US Department of Energy (DOE) is currently investigating technologies for conversion of low-level mixed waste (LLMW) into a form suitable for permanent disposal. Vitrification is one of the preferred technologies since it is capable of consistently producing a durable, leach resistant wasteform, while simultaneously minimizing disposal volumes. Since vitrification of LLMW is a relatively new concept, final wasteform specifications have not been developed. The Savannah River Technology Center (SRTC) of the Westinghouse Savannah River Company (WSRC) has developed the Product Consistency Test (PCI), which is a 7-day leaching procedure for glass. Comparison indicates that both tests have merit where LLMW glasses are concerned. The TCLP is an important test for determining the release of metals and for allowing the wasteform to be delisted while the PCT is more useful for determining consistent production of durable glass. It is a better indicator of the behavior of glass in disposal site conditions. Most aggressive leaching of common oxide glasses occurs under caustic rather than acidic conditions, therefore it is necessary to perform both tests. Further tests will be conducted using additional glass compositions and variations in the TCLP and the PCT