Investigation of actinide-perovskite interaction for nuclear waste immobilization

Safe disposal of nuclear waste is the most important concern for successful utilization of nuclear energy. The high level waste generated during spent fuel reprocessing needs to be encapsulated in some inert matrix as they are environmental hazards which can have somatic and genetic effects in living beings. Therefore efforts are being constantly made to find out suitable matrices for the immobilization of waste. Perovskite based matrices with general formula of ABX3, where (A = Ca, Sr, Ba etc.; B= Ti, Zr, Hf, etc. X = O, F etc.), which crystallize in cubic crystal system can be the potential host for various charged cations and anions. In present case we have chosen barium hafnate matrix viz. BaHfO₃ as our study of interest. The knowledge of the distribution of U among the BaHfO₃ lattice sites is very much important for exploring this material as a potential host. For this purpose a detailed investigation has been carried out using density functional theory (DFT) as a tool. All the DFT calculations have performed using Vienna ab initio simulation package (VASP), which is projector augmented wave (PAW) pseudo potentials based electronic structure code. The calculated defect formation energies of U doped- BaHfO₃ with U@Ba, and U@Hf lattice sites are 6.66 and 4.96 eV, respectively. Therefore, U will prefer the Hf lattice site. (author)