The RHRS is a simple and reliable system that operates by condensing steam from the primary system in the emergency condensers. The emergency condensers are heat exchangers consisting of an arrangement of parallel horizontal U tubes located between the two common headers. The top header is connected to the reactor vessel steam dome, while the lower header is connected to the reactor vessel at a position below the reactor water level. The condensers are located in a pool filled with cold water inside the containment building. The inlet valves of the steam line are always open, while the outlet valves are normally closed (the tube bundles are filled with condensate). When the system is triggered, the outlet valves open automatically. Water drains from the tubes and steam from the primary system enters the tube bundles and condenses on the cold surface of the tubes. The condensate is returned to the reactor vessel forming a natural circulation circuit. In this way, heat is removed from the reactor coolant. During the condensation, heat is transferred to water of the pool by a process of boiling. The evaporated water is then condensed in the suppression pool of the containment.