Effects of Temperature on the Leaching Behavior of Sintered Modified Synroc-B Waste form

Different leaching tests (MCC-1 and MCC-2) have been conducted on a monolithic sintered modified SYNROC-B ceramic waste form containing 10 wt% simulated high-level radioactive waste in triple distilled H₂O. The temperature range was 25 to 150°C. Increases in the leach rates of cesium and barium have been observed as the leaching temperature increases indicating that the leach rate should follow the empirical Arrhenius law:LR_i(t) =K_i exp (-Q_ai/ Rt) ,where LR_i(t), K_i, and Q_ai are the leach rate, the experimental constant, and the activation energy of the element of interest, i. The activation energies for cesium and barium are 6.62 and 3.2 kcal.mol^-1, respectively. The behavior of the pH of the leachant was monitored as a function of leaching time and temperature. Increases in the fluorine ion concentration (F^-) in the leachant were found to be temperature-and time-dependent functions indicating the leaching of the Teflon containers recommended by the Materials Characterization Center. These Teflon containers should be preleached before their use in leaching experiments, or other leach-resistant containers should be used.