Iodine-129, the longest lived isotope of radioiodine in spent nuclear fuel, is a major environmental contaminant of concern potentially released during nuclear fuel reprocessing. Many methods exist to trap iodine from the off-gas at nuclear fuel reprocessing facilities, including flowing the gas through AgNO3-coated packing materials. Studying the interaction of iodine species with the AgNO3 lattice can help to better understand and model the fate of iodine in the system. Quantum-mechanical calculations were used to calculate the reaction energies involved in the incorporation of I- and IO3- into AgNO3. All calculations were performed using the Perdew-Burke-Ernzerhoff (PBE) functional of the generalized gradient approximation (GGA) and the projector augmented-wave formalism as implemented in the Vienna Ab initio Simulation Package (VASP). The solid systems, AgNO3, AgI, AgIO3, as well as the gases involved in the reactions, I2, O2, N2, and NO2, were run with an energy cutoff of 500 eV. The solid systems, Ag8I(NO3)7, and Ag8(IO3)(NO3)7, were also run to calculate the incorporation energies. The solid systems were run using a 4x4x4 or 6x6x4 k-point mesh, depending on the symmetry of the system. The formation of AgI from AgNO3 was found to be unfavorable with a total reaction energy of +1.550 eV and an incorporation energy of +1.511 eV. On the other hand, the formation of AgIO3 from AgNO3 was found to be favorable with a total reaction energy of -1.047 eV and an incorporation energy of -0.967 eV. These results suggest that AgIO3 is likely the favored end product of the reaction between I2 gas and AgNO3 coating.

Quantum-mechanical calculations of iodine incorporation into Ag(NO3)

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.