A nuclear reactor is surrounded by a reactor radiological containment structure. A spent fuel pool is adjacent to and outside of the reactor radiological containment structure. The spent fuel pool may also be contained in its own radiological containment structure. A valved steam pipe runs from the reactor containment structure into the spent fuel pool. During a reactor containment overpressure event, a valve on the steam pipe is opened to allow steam from the reactor containment structure to discharge into (e.g. sparge into) the spent fuel pool. In an alternative embodiment suitable for use in a two-pack nuclear power plant, steam pipes connect the reactor radiological containment structures of the two nuclear reactors, and isolation valves on the steam pipes are opened in response to an overpressure condition in one reactor containment structure in order to discharge steam into the other reactor containment structure.