The French Atomic Energy Commission (CEA) and the Institute for Radiological Protection and Nuclear Safety (IRSN) are developing a hydrogen risk analysis code (safety code) which incorporates both lumped parameter (LP) and computational fluid dynamics (CFD) formulations. In this paper we present briefly the main physical models for containment thermal-hydraulics. Validation and typical numerical results will be presented for hydrogen distribution and combustion applications in small and realistic large geometries.Copyright © 2006 by ASME