Analysis of QUENCH-10 and -16 air ingress experiments with SCDAPSim3.5

Highlights: ► A new oxidation model for steam and air with N2 as a catalyst has been assessed at PSI. ► It recognises breakaway transition to linear from parabolic kinetics. ► The model was assessed against the QUENCH air ingress experiments Q10 and Q16. ► Breakaway prediction and timing are sensitive to the prior oxidation state of the bundle. ► Areas where model improvement is necessary were identified. - Abstract: A recently developed air oxidation model has been implemented in the code version SCDAPSim3.5 and used to analyse the air ingress experiments QUENCH-10 and QUENCH-16 as part of the model assessment. The experiments comprised pre-oxidation in steam, a period of air ingress, and reflood. The analysis focused on the thermal response and possible breakaway during the oxygen consumption. Of particular interest were the effect of the oxygen concentration on the kinetics and the effect of oxygen starvation on the oxidation excursion during the subsequent reflood. The large excursion observed in QUENCH-16 during reflood was not reproduced by the model; the possible causes were explored and indicated the need of further improvement in the model