[0008] By contrast, returning the condensate inside the core barrel above the core reduces core flow and core power. The manometer effect of higher-density water in the downcomer versus lower-density fluid inside the core barrel is what drives natural circulation in a boiling water reactor. This manometer effect is intentionally exaggerated in a boiling water reactor without forced circulation due to jet pumps or external recirculation loops by increasing the height of the upper plenum with a chimney above the core. Return of isolation condenser system condensate into the lower density region above the core reduces the manometer effect, reduces core flow, causes core voiding to increase, and consequently the core power decreases. Since the region above the core has a higher steam quality, the return of the cold isolation condenser system condensate region is very effective in condensing steam which further increases the fluid density on the core side of the manometer. Direct condensation of steam also rapidly lowers the reactor pressure vessel pressure. [0009] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. [0010] The isolation condenser system (ICS) consisting of one or more heat exchangers returns liquid condensate to the reactor pressure vessel (RPV) of a boiling water reactor (BWR) . Typically, condensate is returned to the downcomer region of the boiling water reactor pressure vessel. The present disclosure returns the condensate inside the core shroud above SUMMARY