Abstract: Modified passive containment cooling systems for cooling a reactor core of a boiling water nuclear reactor are described. The reactor core is positioned in a reactor pressure vessel which is located in a drywell of the nuclear reactor. The passive containment cooling system (PCCS), in one form, includes an IC/PCC pool, a GDCS pool, a suppression pool, and a condensate drain tank. The IC/PCC and the GDCS pool each are substantially isolated from the drywell, and the suppression pool is separated from the drywell by a wall having a spill-over hole therein. An equalizing line extends between the suppression pool and the RPV and is configured to transport water from the suppression pool to the RPV. The condensate drain tank is positioned in the drywell and includes a base wall having a sidewall extending therefrom to define a fluid retaining cavity. A steam inlet line extends from within the drywall to a set of passive containment cooling condensers, which condense steam generated within the drywall to water.