Tc immobilization by using perovskite-rich and rutile-rich synroc

The simulating technetium (Tc) separated from HLW was immobilized in perovskite-rich and rutile-rich synroc which contained 85wt% of perovskite or rutile, and 20, 25, 30 or 35wt% waste loading, respectively. The synroc was prepared by hot pressing under reducing condition. The fabricated samples have good physical properties (density and open porosity). The XRD analyses show that the major phase is perovskite or rutile and the minor phases are zirconolite, hollandite and metal alloy. At higher waste loading the metal alloy phase appeared, particularly in the rutile-rich synroc. The scanning electron microscopy (SEM) and back scattered electron images (BEI) show the samples to be homogeneous and densified. The MCC-1 leaching tests (90 degree C, 28 d) results show that: mass losses are at the level of 10-3 g·m-2·d-1, and the nominal element leaching rates are 10-5-10-3 g·m-2·d-1. It indicates that the fabricated samples have good leach resistance. According to their physical properties and leach resistance, the perovskite-rich and rutile-rich synroc can immobilize Tc up to 35 wt%. In comparison, Tc immobilization by using perovskite-rich synroc is more favorable. (authors)