SHIELD PLUG FOR PRESSURE TUBE IN PRESSURE TUBE TYPE NUCLEAR REACTOR

摘要

ABSTRACT OF THE DISCLOSUREA shield plug inserted in a lower extension of apressure tube in a pressure tube type nuclear reactor.The shild plug has a coolant injection passage formedtherethrough and a ball valve mechanism disposed at anintermediate portion of the passage. The ball valvemechanism is so constructed that it permits a coolantinjected through the passage to flow into the pressuretube at the time of exchanging a fuel assembly disposedin the pressure tube and that it blocks the passage bydynamic pressure of a primary circulating coolant introducedin the pressure tube during the normal operation of thereactor.