Title  Interaction between metal fission products TRISO coating materials: A study of chemical bonding and interdiffusion	Researchers C. Heske Collaborators David Williams, Oak Ridge National Laboratory
Background  This project focuses on the chemical bonding and interface formation of metal fission products with the coating materials used in tri-isotropic (TRISO) fuel particles for gas-cooled reactors. By combining surface- and bulk-sensitive spectroscopic methods, intermediate chemical phases at the interface, intermixing/diffusion behavior, and the electronic interface structure as a function of material (metal and coating materials) and temperature are examined.  In detail, the project studies the interface formation of Pd, Cs, and Ag with SiC and pyrolytic carbon. Using SiC single crystals as substrates, interfaces are prepared under controlled conditions in an ultra-high vacuum environment and are studied with a combination of experimental methods, including Photoelectron Spectroscopy, Auger Electron Spectroscopy, Inverse Photoemission, X-Ray Emission Spectroscopy, and X-Ray Absorption Spectroscopy. Furthermore, microscopic techniques (Transmission Electron Microscopy, Scanning Tunneling Microscopy, Atomic Force Microscopy) and local scanning tunneling spectroscopy are being employed.   XPS survey spectra of an HF-etched SiC single crystal surface, after heat treatment at approximately 400°C, and after various deposition steps of Cs (given is the deposition time in seconds).	Research Objectives and Methods By combining results for the electronic and chemical structure of the fission product/TRISO layer interfaces, the research results give information about failure mechanisms of TRISO particles and fission product transport.  Furthermore, they can be used to derive strategies to tailor the interface properties for an optimization of TRISO particles in terms of, e.g., chemical and long-term stability.  The experiments use two different experimental set-ups. First, a multi-chamber ultra-high vacuum system at UNLV (see photo in the 2005-2006 Annual Report) houses the majority of surface-sensitive methods. Second, the soft X-ray fluorescence (SXF) endstation at Beamline 8.0 at the Advanced Light Source, Lawrence Berkeley National Lab is used to perform X-ray absorption and emission spectroscopy. The apparatus at UNLV consists of a surface spectroscopy chamber, a preparation chamber, and a ultra-high vacuum scanning probe microscope. Samples can be introduced into the machine through a glove box with integrated load-lock and then transferred to each of the chambers via a distribution chamber. The analysis chamber is equipped with a state-of-the-art electron analyzer, an X-ray source, an ultraviolet (UV) source, and an inverse photoemission setup consisting of a low-energy high-flux electron gun and a UV detector. The preparation chamber is used for cleaning samples with an ion source and for the deposition of metal films with an evaporator.
Students  Sharath Sudarshanam G Timo Hofmann G Roberto Felix G Ich Tran G Alessio Luinetti, U Sunil Subramanyam U Kyle George U	Department Chemistry
Final Report	Annual Report
Proposal 04/01/04	Quarterly Reports   05/01/04-08/01/04  10/01/04-12/31/04  01/01/05-03/31/05  04/01/05-06/30/05  01/01/06-03/31/06

Theses
M.S. Electrical Engineering, Goverdhan Gajjala, "Interaction Between Pd and SiC: A Study for Triso Nuclear Fuel" May, 2006 (TRP Task 17 )