Abstract: A condensation chamber cooling system of a condensation chamber for a boiling water reactor has a heat exchanger outside the condensation chamber. An elongate cooling module is provided in the condensation chamber with an evaporation space in its upper region. The cooling module is configured such that the evaporation space is located above a maximum filling level of the condensation chamber. The cooling module includes at least one riser pipe and one downpipe that issue with their upper ends into the evaporation space and with their lower ends in the condensation chamber. A first pressure line leads from the evaporation space to the heat exchanger and, from there, a second pressure line which issues in the condensation chamber below the minimum filling level. Thus, the condensation chamber, the pressure lines, the cooling module and the heat exchanger form a passive closed cooling circuit.