BWR type reactor

Purpose: To decrease loss of coolant at the ruptures of pipes in recirculation systems. Constitution: The pipes of a recirculation system penetrates the wall of a pressure vessel at a position above the reactor core, and is apertured with a small opening with a valve at the portion within the pressure vessel and higher than the reactor core. If the pipes are ruptured outside of the reactor, the coolants are released from the ruptured point while the small opening is below the liquid level within the reactor. Then, when the liquid level goes lower than the small opening to form vapor phase in its vicinity, the valve is automatically opened to take vapors through the opening. This rapidly decreases the pressure in the reactor enabling faster introduction of cooling water of ECCS system than usual. (Furukawa, Y.)