Rapid immobilization of simulated radionuclide Nd at low temperatures by flash reaction

Immobilization of radionuclides by more feasible and efficient methods is crucial for dealing with ever-increasing quantities of radioactive nuclear waste. Immobilization of simulated radionuclide Nd through formation of zirconium-based ceramics by flash sintering has been investigated for the first time in this report. A mixture of zirconia, neodymium oxide and gadolinium oxide was flash sintered into pure single phase with pyrochlore or defect fluorite structure within 5 s at low furnace temperature. Specimen temperature during flash reaction was evaluated using black-body radiation model. Compared with flash method, conventional pressureless method could not achieve predominant single phase even at higher temperature and longer time. Results indicated that joule heating alone was not efficient enough to explain rapid mass transportation during immobilization process. Both ultrafast solid-state reaction and densification were accomplished in one-step within short time and low temperature under applied electric field. This proposed approach would be of specific significance in immobilization of nuclear waste as well as rapid synthesis of other ceramics with complex constituents and structures.