Oxidation investigation of cladding specimens for regular and accident tolerant fuel rods under LOCA conditions

The high-temperature oxidation tests were carried out for the regular fuel rod claddings specimens made of sponge-based zirconium alloy (E110G) and for the accident tolerant fuel (ATF) ones - pure vacuum melted molybdenum (VCPM) and niobium alloy (Nb-1%Zr). The tests were carried out under the ambient pressure p ∼ 0.1 MPa in pure water steam. The experimental data on the oxidation characteristics were obtained for E110G specimens in the temperature range T = 1100 - 1500 °C, that for VCPM and Nb-1%Zr are investigated under extended temperature-duration range (more than 1 hour). The thermal effects of molybdenum (Q_SMR) and niobium (Q_SNR) interactions with steam were defined and the derived oxidation rate constants for refractory metals were compared with the known ones. Based on the computations performed with PARAM-TG code the high-temperature oxidation characteristics of model fuel assemblies of large-scale facilities under LOCA conditions with regular and ATF claddings were compared. It was shown that Zr-steam interaction of fuel rod cladding (Q_SZR) is more intensive compared with VCPM and Nb-1%Zr ones under investigated conditions.