Application of density functional theory to the adsorption of Po, Po2, PbPo, H2Po, and PoOH on Ag(1 1 1) surfaces for 210Po capture in lead-bismuth eutectic coolant environments

Abstract Recent nuclear power reactor designs propose the use of lead-bismuth eutectic (LBE) as a coolant. However, neutron capture in liquid LBE produces the radioactive nuclide polonium-210 as 210Po and 210Po-based molecules, which must be sequestered via a capture process. While silver has demonstrated a high adsorption capacity for 210Po, the adsorption capacity of silver for the various forms of Po-based molecules remains uncertain. The present study addresses this issue by applying density functional theory to investigate the adsorption properties of Ag(1 1 1) surfaces with Po, Po2, PbPo, H2Po, and PoOH adsorbates. The results demonstrate that the adsorption capacities of Ag(1 1 1) surfaces for these forms of 210Po reside in the order of Po2 > PoOH > Po > PbPo > H2Po, and all of the adsorption processes are exothermic. In addition, the adsorption processes involved are also characterized based on the calculated density of states. The calculations demonstrate that strongly overlapping Po 6p, O 2p, and Ag 4p states result in the chemisorption of Po, Po2, PbPo, and PoOH on Ag(1 1 1) surfaces, while these states do not overlap strongly for the H2Po adsorbate, resulting in its physisorption on Ag(1 1 1) surfaces.