Improving the Results of QUENCH-16 Experiment by Using New Models of MELCOR 2.1 – P. Vryashkova, P. Groudev

The air ingress experiment Quench-16 was analysed with MELCOR 2.1. The code version of MELCOR 2.1 included oxidation model for air at low and high temperatures. This study explores the influence of oxygen concentration on the hydrogen generation and temperature escalation. The influence of the oxygen concentration on the kinetics behaviour was observed from the Separate Effect Test. In Steinbruek’s work [1] there is an evidence for significant effect of composition and flow rates on oxidation of Zry-4 impact on cladding and the air oxidation kinetics. Oxidation of Zircaloy depends on the time, temperature, gas composition and cladding alloys. Additionally, the oxidation kinetics in air is much faster than in steam due to the formation of non-protective oxide (partially nitrided) scales.

The main purposes of QUENCH-16 test were to examine the oxidation of Zircaloy in air following a limited pre-oxidation in steam and to achieve a long period of oxygen starvation to promote the nitrogen interaction. The low concentration of the oxygen in QUENCH-16 might have resulted in lower rate of oxidation than would be expected. The studies were presented on
oxygen consumption, hydrogen generation and temperature escalation during the whole experiment. Series of simulations using new models of MELCOR for QUENCH-16were performed to examine influence of oxygen concentrations to improve the results of hydrogen generation during the quench phase. The QUENCH-16 test was conducted successfully at KIT (Karlsruhe
Institute of Technology) on 27 July 2011[2,3].

Keywords: severe accident, Hydrogen generation, Oxygen consumption, Nitrogen consumption, quenching.