Effect of synthesis conditions on phase composition of pyrochlore-brannerite ceramics

摘要

Three pyrochlore-brannerite based ceramic samples intended for actinide waste immobilization were synthesized from oxide batches using an inductive melting in a cold crucible and in a microwave furnace and examined by X-ray diffraction and electron microscopy. As follows from electron microscopy data the ceramics are composed of calcium (major) and barium (minor) pyrochlore varieties, minor rutile, uraninite-based solid solution as well as pseudobrookite in the sample produced in the microwave furnace only. Uranium considered as tetravalent actinides surrogate is partitioned between two pyrochlore varieties, brannerite, and uraninite-based solid solution. Leach rates of waste elements measured using a MCC-3 test at 95 deg C are at the level of 10~(-4)-10~(-5) g/(cm~2.day).