Fission product release tests with uranium dioxide fuel and lead under conditions related to reactor accidents for lead-cooled reactors

摘要

Tests of fission product release under accident conditions were performed on three samples of irradiated UO2 fuel fragments immersed in molten Pb. Two tests of bare irradiated UO2 fragment samples were conducted under similar conditions for direct comparison. The irradiated fuel samples had been cooled for several years, then encapsulated and trace-reirradiated to populate limited inventories of short-lived fission products (such as Xe-133 and I-131). The tests were conducted with sample temperatures between 1570 and 1590 K. The releases from Pb-covered samples under inert conditions were similar to those from bare UO2 under inert conditions. Greater Xe-133 releases were observed from Pb-covered samples in oxidizing environments. Release of Ba-140 was detected for the Pb-covered sample exposed to air. Under oxidizing conditions, Pb-covered samples retained more Cs-137 and Ru-103 (delayed onset of release in air and complete retention in steam) as well as I-131. (C) 2020 Elsevier Ltd. All rights reserved.