Book Description

The Los Alamos Scientific Laboratory has been active for the past twenty years in the development and testing of graphitic-based high temperature reactor fuel elements. The initial involvement was in the field of nuclear propulsion systems. Project Rover began as a program to develop a nuclear-powered, hydrogen-propelled rocket engine. The basic fuel element for the Rover Program became uranium-loaded graphite. The enriched uranium fuel was incorporated into the graphite matrix as uranium oxide, later as pyrolytic-carbon coated uranium dicarbide microspheres, and, most recently, as a solid solution of uranium carbide and zirconium carbide. The fuel element matrix was protected from the hydrogen propellant/coolant by a chemical vapor deposited coating of refractory carbides such as niobium carbide, zirconium carbide, and tantalum carbide. The performance of these fuel elements was established through actual tests up to a sustained power level of about 3000 MW. The Ultra High-Temperature Reactor Experiment, UHTREX, utilized uranium-loaded graphite fuel elements in a demonstration high-temperature process-heat nuclear reactor. This system operated at temperatures in excess of 1500°K using helium as the cooling medium. The performance of the graphitic fuel elements again proved excellent. Presently, the Los Alamos Scientific Laboratory is developing fuel elements for possible use in the Argonne National Laboratory TREAT reactor. This report describes the nondestructive examination program for these experimental fuel elements.