Fukushima Daiichi Unit 1 power plant containment analysis using GOTHIC

The 3D containment model includes models for the heat transfer from the steam and gas in the drywell vent system to the torus room, wetwell gas space and pool. Inclusion of vent heat transfer had a significant impact on the overall containment response for the 1F1 scenario, particularly during the steam and hydrogen release from the primary system following the postulated failure of reactor vessel. Condensation in the vent system reduced transfer of noncondensing gases to the wetwell resulting in lower containment pressure and higher gas concentrations in the drywell.