Continuous-Flow Leaching Studies of Crushed and Cored SYNROC

Both crushed (150- to 300-μm) and cored (1.8-mm-diam) samples of SYNROC have been leached with single-pass continuous-flow leaching equipment. Crushed samples of cesium-hollandite were also leached in a similar experiment. Temperatures used were 25° and 75°C and leachates were 0.03 N NaHCO₃ and distilled water. Leaching rates from SYNROC-C were ranked cesium >strontium ≥ calcium >barium >zirconium. A comparison of leaching rates is made between crushed SYNROC, cored SYNROC, and Pacific Northwest Laboratory 76-68 glass beads. This comparison depends on how the surface areas are determined for each sample. Based on geometric surface areas for SYNROC cores and glass beads, cesium leach rates from SYNROC compare well with both sodium and neptunium leached from the glass. The other elements leached from SYNROC are lower than sodium and neptunium leached from glass. They also vary for each element while glass shows nearly the same leach rate for both sodium and neptunium.