Does Iodate Incorporate into Layered Uranyl Phosphates Under Hydrothermal Conditions?

Three new layered uranyl phosphates, Ba3(UO2)2(HPO4)2(PO4)2, Ba(UO2)F(PO4), and Cs2(UO2)2(PO4)2, were synthesized under mild hydrothermal conditions. These compounds serve as models for uranium alteration phases that might form when spent nuclear fuel is subjected to oxidizing groundwater containing dissolved phosphate. In order to address the possibility of the incorporation of the key fission product 129I in the form of iodate into uranyl alteration phases, the substitution of IO3− for the structurally related PO3(OH)2− or PO43− unit was probed. Iodate incorporation into these phases was investigated using LA-ICP-MS, and these data indicate incorporation of iodine with levels as high as 4162 ppm.