COUNTER-INTUITIVE NITROGEN OCCUPANCY IN TETRAGONAL ZIRCONIA

摘要

This study aims to assist in the analysis of practices applied during the severe hydrogen explosion accidents at the Fukushima nuclear reactors in 2011, by using first-principles-based computer modeling techniques. In particular the influence of nitrogen gas to the stability of zirconium cladding alloys (which host nuclear fuels), has been investigated. Current design of commercial zirconium cladding alloys is based on assumptions that nitrogen substitute lattice oxygen in zirconia, and tin or niobium were alloyed to control the nitrogen effect and slow down oxidation. We expel this nitrogen substitution mechanism and established a more energetically stable NO diatomic structure from first principles calculations. Our contribution not only opens ways to form new alloying strategies for the next generation of zirconium cladding alloys but more importantly provides opportunities to critically examine the standard operation procedures in the management of severe nuclear reactor accidents.