Interdiffusion behavior in RERTR fuels using composition profile data. MATTHEW CARLSON (Brigham Young university Idaho Rexburg, ID 83440) DENNIS KEISER (Idaho National Laboratory, Idaho Falls, ID, 83415)

Working this summer as an Intern at the I.N.L.'s M.F.C., I had the privilege of working with Dr. Dennis Keiser. We investigated interdiffusion behavior in RERTR fuels using composition profile data that was generated from actual fuel plates using a scanning electron microscope. Multicomponent, multiphase interdiffusion theory was then employed to calculate interdiffusion data from these profiles. To increase the efficiency of this process, a computer program was created using the computer code Maple. This computer program consisted of nine steps: First, data points were entered directly into Maple in matrix form. Second, concentration (atom fraction) data was plotted as a function of position (micrometers). Third, the plotted data was fit using a cubic-spline approach. Fourth, the Matano plane, or plane of mass balance, was calculated for each component. Fifth, the interdiffusion flux was calculated for each component as a function of position. Sixth, the interdiffusion flux was plotted for each component and checked, for consistency, to make sure that the sum of the fluxes at each position added to zero. Seventh, average effective interdiffusion coefficients were calculated by applying integration by parts, which is very straightforward using Maple. Eighth, effective penetration depths were calculated to get an idea of how far each component penetrated into the diffusion zone. Completion of this project has increased my understanding of the field of materials science, as well as the field of computer programming. I know that creating the above-mentioned computer program has enhanced my ability to program using Maple 9.5. The work experience gained at the INL has strengthened my scientific background, and this will serve me well as I explore other fields of science.

Theoretical Plotting of Thermodynamic Data Using the Thermocalc Software and Comparison with Established Data with an Emphasis in Radiological Fuels. TRAVIS KOENIG (Colorado School of Mines Golden, CO 80401) IRINA GLAGOLENKO (Idaho National Laboratory, Idaho Falls, ID, 83415)

Thermodynamic data for various nuclear fuels is available and needs to be implemented for the generation of phase diagrams and other thermodynamic plots to be used in predicting various fuel alloy behaviors. Thermocalc is a thermodynamic modeling software capable of generating a variety of plots, however, it has not yet been fully evaluated and its use is limited by knowledge of the software. By implementing a database on nuclear fuel elements it is possible to generate accurate plots exhibiting the behavior of various fuel alloys to be used in power plants. These plots will then be compared with established or theoretical data from previous work to check validity and make predictions. The procedure involved in generating these graphs also needs to be documented. Working closely with the Thermocalc software developers and laboratory workers in the lab it is possible to generate plots for use in the prediction of nuclear fuel behavior of various alloys of Americium, Plutonium, Neptunium, Uranium, and Zirconium. These plots will be compared with previous and current work to create accurate predictions as well as the generation techniques documented. When comparing data established in situ with plots generated with Thermocalc, it was found that accurate plots were possible to generate, with only minimal discrepancies, plots of thermodynamic behavior of various alloys. However, with the software's limitations in modeling intermetallic phases, the Np-Zr phase diagram was difficult to interpret and further research will be required. This is part of an ongoing project to fully implement the Thermocalc software along with data established in this lab and previous work to accurately predict various fuel alloy behavior for use in nuclear power plants.

Transient Liquid Phase Bonding Development. JARED WIGHT (Brigham Young university Idaho Rexburg, ID 83460) CURTIS CLARK (Idaho National Laboratory, Idaho Falls, ID, 83415)

Transient liquid phase bonding (TLPB) is a process that employs a liquid eutectic which diffuses into a parent material. For the Reduced Enrichment for Research and Test Reactors (RERTR) program, aluminum 6061 is used as a parent material while silicon is used to form the eutectic. Silicon is deposited on a piece of aluminum and put in a hot press to create the bond. The RERTR program is currently developing this process for cladding a newly developed uranium-molybdenum monolithic fuel foil. Work on cladding the monolithic fuel foil began with selecting silicon as the material to create the eutectic with aluminum. A previous patent was used to determine how to apply the silicon to the aluminum plate. This was done by creating a silicon "paint" and painting it on the surface. Bonding times, temperatures, and pressures were studied to determine the optimal procedure. Ultra-sonic scanning was used to determine bond integrity. Initial results were promising but not satisfactory for testing in the reactor due to incomplete bonding. Recent literature research and novel ideas have led to many new variables that needed to be tested to make TLPB a valid bonding process for the RERTR project. Three key areas were targeted for development work: initial cleaning, silicon application, and actual bonding procedures. The current process includes mechanical and chemical cleaning and silicon application by flame spraying. The assembly is then put in a hot press near the eutectic temperature and held at 1000 psi for 30 minutes. This is now creating very desirable bonds. Future work will include development of the bonding parameters, inclusion of TLPB fuel plates in the next RERTR test in the Advanced Test Reactor, and plans for scaling up the process for larger foils. More work will also need to be done to create a good bond with a desirable grain structure.