James Henry Miller

Recapturing Graphite-Based Fuel Element Technology for Nuclear Thermal Propulsion

ORNL is currently recapturing graphite based fuel forms for Nuclear Thermal Propulsion (NTP). This effort involves research and development on materials selection, extrusion, and coating processes to produce fuel elements representative of historical ROVER and NERVA fuel. Initially, lab scale specimens were fabricated using surrogate oxides to develop processing parameters that could be applied to full length NTP fuel elements. Progress toward understanding the effect of these processing parameters on surrogate fuel microstructure is presented. I. Introduction HE research presented in this report is a collaborative effort between Oak Ridge National Laboratory (ORNL) and NASA to recapture manufacturing technology for full length ROVER/NERVA graphite composite fuel elements. Nuclear thermal propulsion (NTP) fuel development has been intermittently ongoing since the late 1950’s and many of the original materials used in the early fuel development are no longer available. Also, the processing capability and the art associated with the production of full-length elements have been lost. The focus of the collaboration is to recapture the capability and expertise to produce representative fuel element test samples and iteratively scale up to full-length elements. To maximize efficiency, the work was separated into two tasks, extrusion development and coating development, which were conducted in parallel. At this stage in the program, the extrusion development task is focused on recreating a representative blend of materials, evaluating blending methods, and establishing an extrusion capability. The coating task is focused on developing processing conditions and equipment to establish ZrC coating capability. This report summarizes the accomplishments and progression toward these goals. It is important to note that the results and analyses presented here are in the early stages of research (TRL 3) and should be considered preliminary.

Design Study for a Low-Enriched Uranium Core for the High Flux Isotope Reactor, Annual Report for FY 2008

This report documents progress made during FY 2008 in studies of converting the High Flux Isotope Reactor (HFIR) from highly enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. With axial and radial grading of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in reactor performance from the current level. Results of selected benchmark studies imply that calculations of LEU performance are accurate. Scoping experiments with various manufacturing methods for forming the LEU alloy profile are presented.

Nuclear Energy Research Initiative Project No. 02 103 Innovative Low Cost Approaches to Automating QA/QC of Fuel Particle Production Using On Line Nondestructive Methods for Higher Reliability Final Project Report

This Nuclear Energy Research Initiative (NERI) project was tasked with exploring, adapting, developing and demonstrating innovative nondestructive test methods to automate nuclear coated particle fuel inspection so as to provide the United States (US) with necessary improved and economical Quality Assurance and Control (QA/QC) that is needed for the fuels for several reactor concepts being proposed for both near term deployment [DOE NE & NERAC, 2001] and Generation IV nuclear systems. Replacing present day QA/QC methods, done manually and in many cases destructively, with higher speed automated nondestructive methods will make fuel production for advanced reactors economically feasible. For successful deployment of next generation reactors that employ particle fuels, or fuels in the form of pebbles based on particles, extremely large numbers of fuel particles will require inspection at throughput rates that do not significantly impact the proposed manufacturing processes. The focus of the project is nondestructive examination (NDE) technologies that can be automated for production speeds and make either: (I) On Process Measurements or (II) In Line Measurements. The inspection technologies selected will enable particle “quality” qualification as a particle or group of particles passes a sensor. A multiple attribute dependent signature will be measured and used for qualification or process control decisions. A primary task for achieving this objective is to establish standard signatures for both good/acceptable particles and the most problematic types of defects using several nondestructive methods.