PNNL

This report describes the results from the solid phase characterization of six Cast Stone monoliths from the extended leach tests recently reported on (Serne et al 2016),that were selected for characterization using multiple state-of-the-art approaches. The Cast Stone samples investigated were leached for > 590 d in the EPA Method 1315 test then archived for > 390 d in their final leachate. After reporting the long term leach behavior of the monoliths, it was suggested that physical changes to the waste form samples and a depleting inventory of contaminants of potential concern may mean that effective diffusivity calculations past 63 d should not be used to t accurately represent long-term waste form behavior. Understanding the physical and chemical mechanisms that occur in the Cast Stone during the long-term leaching process is thus imperative to support long term modelling of cementitious waste form performance. These novel investigations provide an initial arsenal of techniques which can be utilized to perform such Cast Stone solid phase characterization work, which in turn can support upcoming performance assessment maintenance. The work was performed at Pacific Northwest National Laboratory (PNNL) for Washington River Protection Solutions (WRPS) to characterize several properties of the long term leached Cast Stone monolith samples: