Comparative assessment of PSI air oxidation model implementation in SCDAPSim3.5, MELCOR 1.8.6 and MELCOR 2.1

The PSI air oxidation model has been successfully implemented in the lump parameter code MELCOR. The PSI air oxidation model treats oxygen as an active species and nitrogen as a catalyst that accelerates the oxidation kinetics. The essential feature of the model is the transition from parabolic to linear kinetics. The implementation has been assessed against the previous post-test analyses for the air ingress experiment QUENCH-16 performed with a local version of RELAP5/SCDAPSim3.5. This version contains the PSI air oxidation model. The pre-oxidation and air phase were consistent when similar modelling options were used and all code versions were in fair agreement with the experimental data, showing consistency in the implementation of the model. The PSI air oxidation model will be used in the future for analysis of spent fuel pool uncovery sequences where steam/air mixture is the prototypical environment.