Separation and purification of Sr-90 nuclide from a waste mixture

Sr-90 is utilized as a raw material in various fields such as nuclear batteries, medical applications, and industrial use as a beta particle source. Therefore, high-purity Sr-90 is required to increase the thermal efficiency of nuclear battery operation or to prevent side effects on the human body during its use in medical therapy. Sr-90 is present in spent nuclear fuel and can be separated via reactive distillation through a pyrochemical process developed at the Korea Atomic Energy Research Institute, where Ba is obtained simultaneously via co-precipitation owing to its chemical similarity. In addition, Sr-90 decays into Zr-90 during the storage period after separation. Therefore, Ba and Zr-90 should be separated to obtain high-purity Sr-90 nuclides. In the present study, a separation and purification process is developed for the recovery of Sr-90 from a waste mixture containing Sr-90, Ba, and Zr-90. To separate Ba and Zr-90, the chromate precipitation reaction is modified via pH control, which can enhance the precipitation efficiency of Ba and prevent the co-precipitation of Sr owing to the excess amount of precipitants. A systematic study is conducted to optimize Sr-90 separation and purification processes, where a high yield of 84.3% is obtained, and a high purity exceeding 99.9% is maintained. (author)