An experimental study to immobilize simulated high uranium waste from reprocessing of Candu fuels

An experimental study was carried out to determine the feasibility of using the sol-gel process for immobilization of fission products from a simulated high level liquid waste stream resulting from CANDU fuel reprocessing with the Amine process. Most of the fission products were found to be immobilized in sol-gel beads made of an uranium matrix from the waste itself but 60 to 100% of cesium and 0 to 4% of strontium could not be immobilized and were washed out. Cesium was re-absorbed from the wash using a Zeolon inorganic ion exchange column but only after most of the ammonia from the wash was removed and the column operated at a low superficial velocity of 1 cm/min. Sol-gel beads were pelletized and sintered into strong, dense pellets and leaching of these pellets in a simulated granite groundwater showed that they were relatively leach resistant with a waste leach rate of about 1.4 x 10-5 kg of waste/m2.d. This leach rate is in the same order of magnitude as that from CANDU unirradiated fuel