Behavior of high burnup fuels under Reactivity-Initiated Accident (RIA) and Loss-of-Coolant Accident (LOCA) conditions, 7; Oxidation behavior of fuel cladding in a LOCA

Chuto, Toshinori; Nagase, Fumihisa ; Ono, Katsuto; Fuketa, Toyoshi

In order to investigate effect of burnup on high temperature oxidation of the advanced cladding alloys, isothermal oxidation tests were performed with specimens prepared from high burnup fuel cladding which were irradiated up to 79 MWd/kg as well as non-irradiated cladding. Oxidation kinetics was evaluated from weight gain and oxide layer growth. Oxide layer thickness on the cladding outside diameter (OD) is smaller in the irradiated cladding. It is considered that the oxidation at the cladding OD was suppressed by the pre-formed corrosion layer. Results of the weight gain measurement also suggest lower oxidation rates in the irradiated cladding. Difference in the alloy composition hardly affected the oxidation rates.