Metallic thorium uranium fuel elements continue to show excellent irradiation performance in high temperature pressurized water coolant. Volume expansion measurements made after 2.1{times}10{sup 20} fissions/cm{sup 3} (6200 MWD/T) at fuel temperatures above 500 C shows no indication of fission gas-in-duced swelling. Analysis of fuel swelling data from tubular elements shows apparent effect of geometry (restraint) on both low temperature volume expansion and the temperature at which accelerated volume expansion initiates. Evidence of grain boundary tearing has been observed in tubular metallic uranium fuels irradiated in 1600 pos water coolant. Volume expansion due to two types of structural damage have ben observed uranium - 2 w/o zirconium alloy irradiated to 0.25 a/o burnup at temperatures up to 550 C.