[en] Sandia National Laboratories is participating in several NRC-sponsored programs to study severe accident phenomenology. Part of that effort involves the combined use of the computer codes MARCH and HECTR to examine hydrogen behavior during severe accidents. These codes have been applied to an ice-condenser containment. Results indicate the importance of combustion and containment system modeling parameters in predicting containment pressure-temperature response. Important factors include the ignition and propagation limits, combustion completeness, flame speed, spray operation, and recirculation fan operation