Analysis of Quench Tests Including a B4C Control Rod with the ICARE/CATHRE Code and B4C Oxidation Modelling Assessment

International Topical Meeting on Nuclear Thermal-Hydraulics (NURETH-11), Avignon, 3-6 Octobre 2005

Nathalie Seiler, Frédéric Bertrand.

The present paper deals with ICARE/CATHARE post-test calculations of the experiments QUENCH-07, QUENCH-08 and QUENCH-09. On the one hand, the objective is to check the ability of this code to simulate these QUENCH experiments and the B4C control rod degradation. On the other hand, the local impact of B4C control rod degradation on the whole bundle degradation is studied, thanks to simulation results of QUENCH-07 and 08 experiments.
The main modelling features of the ICARE/CATHARE code are presented. Among others, an improved B4C oxidation modelling, elaborated from IRSN previous modelling and the last results of the VERDI analytical experiments performed by IRSN at low pressure, is established. Finally, according to the agreement between the measured and the calculated bundle temperatures as well as hydrogen release and oxidized B4C, the ICARE/CATHARE code simulates rather well QUENCH experiments involving B4C control rod degradation, Zircaloy oxidation under starvation and cooling with steam. Moreover, by performing a simulation of QUENCH-08 configuration applying the boundary conditions of QUENCH-07, the importance of the existing discrepancies between QUENCH-07 and 08 boundary conditions is highlighted : these discrepancies are responsible for the differences in the thermal behaviour of both tests and for about 73% of the surplus of hydrogen produced in QUENCH-07 compared to QUENCH-08 test. In these simulations, the B4C degradation has a little direct effect and an influence on Zircaloy oxidation through power release, material melting and flowing down.