Grain-Boundary Cavitation and Weld-Underbead Cracking in DOP-26 Iridium Alloy

摘要

Plutonium-238 oxide fuel pellets for the General Purpose Heat Source Radioisotopic thermoelectric generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in DOP-26 iridium alloy at the Savannah River Plant. DOP-26 iridium alloy was developed at the Oak Ridge National Laboratory and contains nominally 0.3 weight-percent tungsten, 60-ppM thorium and 50-ppM aluminum. Underbead cracks occasionally occur in the girth weld on the iridium alloy cladding in the area where the gas tungsten arc is quenched. A variety of electron beam techniques have been used to determine the cause of cracking. Results are discussed. (ERA citation 08:045769)