Title: Effect of high temperature in-pile irradiation upon high density UO/sub 2/ bodies
Abstract: A s a part of the ML-1 fuel evaluation program, high density bulk UO pellets were irradiated to burnups equivalent to 8500 hours o$ ML-1 reactor operation (3.0 a/o U-235) under temperature conditions approximating those expected in the reactor (1750OF peak cladding surface temperature).Post irradiation examination revealed severe fuel cracking although fission product gas release measurements agreed well with calculated values.No structural changes were revealed by metallography and X-ray diffraction except for a small unidentified phase observed at the fuel grain boundaries.This phase is considered to be the result of impurities or fission product gas sites.The data obtained on U02 fuel is in agreement with that determined in irradiation experiments performed at other facilities.The performance of U02 fuel was sufficiently good to permit use in the ML-1 reactor.