Growth of oxygen-induced nanoscale-pyramidal facets on Rh(210) surface

Oxygen-induced nanometer scale faceting of the atomically rough Rh(210) surface has been studied using Auger electron spectroscopy, low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). When the Rh(210) surface is annealed at temperature ≥550 K in oxygen (pressure ≥2×10−8 Torr), it becomes completely covered with nanometer-scale facets. LEED studies reveal that the faceted surface is characterized by three-sided nanoscale pyramids exposing one reconstructed (110) and two {731} faces on each pyramid. STM measurements confirm the LEED results and show that the average facet size ranges from 12 to 21nm when changing annealing temperature from 800 to 1600 K. Moreover, atomically resolved STM images show that the (110) face of faceted Rh(210) exhibits various reconstructions (1×n, n=2–4) depending on oxygen coverage. Faceted Rh(210) is a potential template for studies of structure sensitive reactions

Radiolytic and Thermal Processes Relevant to Dry Storage of Spent Nuclear Fuel

Characterize the effects of temperature and radiation processes on the interactions of H20 with oxide surfaces. Our experiments focused on the fundamental interaction of H20 molecules with surfaces of U02. We characterized the surface chemistry of adsorbed H2O using thermal desorption methods and radiotracer methods, as well as x-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). In parallel with these measurements of thermal effects, we examined the effects of secondary electrons and high-energy photons on hydrogen and oxygen generation and, and how this related to corrosion of spent nuclear fuel. These studies concentrated on neutral and ionic (cation and anion) desorption products of low-energy electron irradiation of water-covered UO2

Radiolytic and Thermal Process Relevant to Dry Storage of Spent Nuclear Fuels

This project involves basic research in chemistry and physics aimed at providing information pertinent to the safe long-term dry storage of spent nuclear fuel (SNF), thousands of tons of which remain in water storage across the DOE complex. The Hanford Site K-Basins alone hold 2300 tons of spent fuel, much of it severely corroded, and similar situations exist at Savannah River and Idaho National Engineering and Environmental Laboratory. DOE plans to remove this fuel and seal it in overpack canisters for ''dry'' interim storage for up to 75 years while awaiting permanent disposition. Chemically bound water will remain in this fuel even after the proposed drying steps, leading to possible long-term corrosion of the containers and/or fuel rods themselves, generation of H2 and O2 gas via radiolysis (which could lead to deflagration or detonation), and reactions of pyrophoric uranium hydrides. No thoroughly tested model is now available to predict fuel behavior during preprocessing, processing, or storage. In a collaborative effort among Rutgers University, Pacific Northwest National Laboratory, and Brookhaven National Laboratory, we are studying the radiolytic reaction, drying processes, and corrosion behavior of actual SNF materials and of pure and mixed-phase samples. We propose to determine what is omitted from current models: radiolysis of water adsorbed on or in hydrates or hydroxides, thermodynamics of interfacial phases, and kinetics of drying. A model will be developed and tested against actual fuel rod behavior to ensure validity and applicability to the problems associated with developing dry storage strategies for DOE-owned SNF