Immobilization and aqueous durability of Nd2O3 and CeO2 incorporation into rutile TiO2

Synroc is recognized as the second generation waste form for safety disposal of high-level radioactive waste (HLW). In this study, the Synroc mineral of rutile was employed as host phase for the immobilization of Nd 2 O 3 and CeO 2 , which were selected as surrogates of trivalent and tetravalent actinide nuclides. Rutile waste forms with different Nd 2 O 3 and CeO 2 incorporations were prepared under normal pressure sintering. Nd 2 Ti 2 O 7 pyrochlore was produced as the target phase in 1100   °C calcined Nd-bearing TiO 2 . Lattice stabilization of CeO 2 in rutile TiO 2 could not be accomplished even under 1500   °C sintering. The 28 day normalized leaching rates ( LR i ) of Ti and Nd in Nd-bearing rutile, which decline congruously as the Nd 2 O 3 content increases, are lower than 3×10 −5   g   m −2   d −1 . The incorporation of CeO 2 significantly impairs the aqueous durability of rutile waste form.